2005-09-09 14:10:30 -06:00
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/*
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FUSE: Filesystem in Userspace
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2008-11-26 04:03:54 -07:00
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Copyright (C) 2001-2008 Miklos Szeredi <miklos@szeredi.hu>
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2005-09-09 14:10:30 -06:00
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This program can be distributed under the terms of the GNU GPL.
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See the file COPYING.
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*/
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#include "fuse_i.h"
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#include <linux/pagemap.h>
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#include <linux/slab.h>
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#include <linux/kernel.h>
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Detach sched.h from mm.h
First thing mm.h does is including sched.h solely for can_do_mlock() inline
function which has "current" dereference inside. By dealing with can_do_mlock()
mm.h can be detached from sched.h which is good. See below, why.
This patch
a) removes unconditional inclusion of sched.h from mm.h
b) makes can_do_mlock() normal function in mm/mlock.c
c) exports can_do_mlock() to not break compilation
d) adds sched.h inclusions back to files that were getting it indirectly.
e) adds less bloated headers to some files (asm/signal.h, jiffies.h) that were
getting them indirectly
Net result is:
a) mm.h users would get less code to open, read, preprocess, parse, ... if
they don't need sched.h
b) sched.h stops being dependency for significant number of files:
on x86_64 allmodconfig touching sched.h results in recompile of 4083 files,
after patch it's only 3744 (-8.3%).
Cross-compile tested on
all arm defconfigs, all mips defconfigs, all powerpc defconfigs,
alpha alpha-up
arm
i386 i386-up i386-defconfig i386-allnoconfig
ia64 ia64-up
m68k
mips
parisc parisc-up
powerpc powerpc-up
s390 s390-up
sparc sparc-up
sparc64 sparc64-up
um-x86_64
x86_64 x86_64-up x86_64-defconfig x86_64-allnoconfig
as well as my two usual configs.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-20 15:22:52 -06:00
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#include <linux/sched.h>
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2009-04-13 19:54:53 -06:00
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#include <linux/module.h>
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2010-11-30 08:39:27 -07:00
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#include <linux/compat.h>
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2011-07-25 14:35:35 -06:00
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#include <linux/swap.h>
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2013-05-07 17:19:08 -06:00
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#include <linux/aio.h>
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2013-05-17 07:30:32 -06:00
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#include <linux/falloc.h>
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2005-09-09 14:10:30 -06:00
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2006-03-28 02:56:42 -07:00
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static const struct file_operations fuse_direct_io_file_operations;
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2005-09-09 14:10:37 -06:00
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2009-04-28 08:56:37 -06:00
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static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
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int opcode, struct fuse_open_out *outargp)
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2005-09-09 14:10:30 -06:00
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{
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struct fuse_open_in inarg;
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2005-11-07 01:59:51 -07:00
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struct fuse_req *req;
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int err;
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2012-10-26 09:48:30 -06:00
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req = fuse_get_req_nopages(fc);
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2006-04-10 23:54:58 -06:00
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if (IS_ERR(req))
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return PTR_ERR(req);
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2005-11-07 01:59:51 -07:00
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memset(&inarg, 0, sizeof(inarg));
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2007-10-18 04:07:02 -06:00
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inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
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if (!fc->atomic_o_trunc)
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inarg.flags &= ~O_TRUNC;
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2009-04-28 08:56:37 -06:00
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req->in.h.opcode = opcode;
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req->in.h.nodeid = nodeid;
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2005-11-07 01:59:51 -07:00
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req->in.numargs = 1;
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req->in.args[0].size = sizeof(inarg);
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req->in.args[0].value = &inarg;
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req->out.numargs = 1;
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req->out.args[0].size = sizeof(*outargp);
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req->out.args[0].value = outargp;
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2008-11-26 04:03:55 -07:00
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fuse_request_send(fc, req);
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2005-11-07 01:59:51 -07:00
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err = req->out.h.error;
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fuse_put_request(fc, req);
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return err;
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}
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2008-11-26 04:03:55 -07:00
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struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
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2005-11-07 01:59:51 -07:00
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{
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struct fuse_file *ff;
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2009-04-13 19:54:49 -06:00
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2005-11-07 01:59:51 -07:00
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ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
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2009-04-13 19:54:49 -06:00
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if (unlikely(!ff))
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return NULL;
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2009-04-28 08:56:36 -06:00
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ff->fc = fc;
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2012-10-26 09:48:07 -06:00
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ff->reserved_req = fuse_request_alloc(0);
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2009-04-13 19:54:49 -06:00
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if (unlikely(!ff->reserved_req)) {
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kfree(ff);
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return NULL;
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2005-11-07 01:59:51 -07:00
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}
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2009-04-13 19:54:49 -06:00
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INIT_LIST_HEAD(&ff->write_entry);
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atomic_set(&ff->count, 0);
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RB_CLEAR_NODE(&ff->polled_node);
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init_waitqueue_head(&ff->poll_wait);
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spin_lock(&fc->lock);
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ff->kh = ++fc->khctr;
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spin_unlock(&fc->lock);
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2005-11-07 01:59:51 -07:00
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return ff;
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}
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void fuse_file_free(struct fuse_file *ff)
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{
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2006-06-25 06:48:52 -06:00
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fuse_request_free(ff->reserved_req);
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2005-11-07 01:59:51 -07:00
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kfree(ff);
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}
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2009-04-28 08:56:37 -06:00
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struct fuse_file *fuse_file_get(struct fuse_file *ff)
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2007-10-17 00:31:00 -06:00
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{
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atomic_inc(&ff->count);
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return ff;
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}
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2011-02-25 06:44:58 -07:00
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static void fuse_release_async(struct work_struct *work)
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{
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struct fuse_req *req;
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struct fuse_conn *fc;
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struct path path;
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req = container_of(work, struct fuse_req, misc.release.work);
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path = req->misc.release.path;
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fc = get_fuse_conn(path.dentry->d_inode);
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fuse_put_request(fc, req);
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path_put(&path);
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}
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2007-10-17 00:31:04 -06:00
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static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
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{
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2011-02-25 06:44:58 -07:00
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if (fc->destroy_req) {
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/*
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* If this is a fuseblk mount, then it's possible that
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* releasing the path will result in releasing the
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* super block and sending the DESTROY request. If
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* the server is single threaded, this would hang.
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* For this reason do the path_put() in a separate
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* thread.
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*/
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atomic_inc(&req->count);
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INIT_WORK(&req->misc.release.work, fuse_release_async);
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schedule_work(&req->misc.release.work);
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} else {
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path_put(&req->misc.release.path);
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}
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2007-10-17 00:31:04 -06:00
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}
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2011-02-25 06:44:58 -07:00
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static void fuse_file_put(struct fuse_file *ff, bool sync)
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2007-10-17 00:31:00 -06:00
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{
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if (atomic_dec_and_test(&ff->count)) {
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struct fuse_req *req = ff->reserved_req;
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2009-04-28 08:56:39 -06:00
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2013-11-05 08:05:52 -07:00
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if (ff->fc->no_open) {
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/*
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* Drop the release request when client does not
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* implement 'open'
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*/
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req->background = 0;
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path_put(&req->misc.release.path);
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fuse_put_request(ff->fc, req);
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} else if (sync) {
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2013-03-21 08:02:04 -06:00
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req->background = 0;
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2011-02-25 06:44:58 -07:00
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fuse_request_send(ff->fc, req);
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path_put(&req->misc.release.path);
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fuse_put_request(ff->fc, req);
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} else {
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req->end = fuse_release_end;
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2013-03-21 08:02:04 -06:00
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req->background = 1;
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2011-02-25 06:44:58 -07:00
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fuse_request_send_background(ff->fc, req);
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}
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2007-10-17 00:31:00 -06:00
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kfree(ff);
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}
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}
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2009-04-13 19:54:53 -06:00
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int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
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bool isdir)
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2009-04-28 08:56:37 -06:00
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{
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struct fuse_file *ff;
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int opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
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ff = fuse_file_alloc(fc);
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if (!ff)
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return -ENOMEM;
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2013-11-05 08:05:52 -07:00
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ff->fh = 0;
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ff->open_flags = FOPEN_KEEP_CACHE; /* Default for no-open */
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if (!fc->no_open || isdir) {
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struct fuse_open_out outarg;
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int err;
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err = fuse_send_open(fc, nodeid, file, opcode, &outarg);
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if (!err) {
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ff->fh = outarg.fh;
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ff->open_flags = outarg.open_flags;
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} else if (err != -ENOSYS || isdir) {
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fuse_file_free(ff);
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return err;
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} else {
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fc->no_open = 1;
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}
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2009-04-28 08:56:37 -06:00
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}
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if (isdir)
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2013-11-05 08:05:52 -07:00
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ff->open_flags &= ~FOPEN_DIRECT_IO;
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2009-04-28 08:56:37 -06:00
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ff->nodeid = nodeid;
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file->private_data = fuse_file_get(ff);
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return 0;
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}
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2009-04-13 19:54:53 -06:00
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EXPORT_SYMBOL_GPL(fuse_do_open);
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2009-04-28 08:56:37 -06:00
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2013-10-10 07:10:04 -06:00
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static void fuse_link_write_file(struct file *file)
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{
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struct inode *inode = file_inode(file);
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struct fuse_conn *fc = get_fuse_conn(inode);
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struct fuse_inode *fi = get_fuse_inode(inode);
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struct fuse_file *ff = file->private_data;
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/*
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* file may be written through mmap, so chain it onto the
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* inodes's write_file list
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*/
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spin_lock(&fc->lock);
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if (list_empty(&ff->write_entry))
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list_add(&ff->write_entry, &fi->write_files);
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spin_unlock(&fc->lock);
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}
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2009-04-28 08:56:37 -06:00
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void fuse_finish_open(struct inode *inode, struct file *file)
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2005-11-07 01:59:51 -07:00
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{
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2009-04-28 08:56:37 -06:00
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struct fuse_file *ff = file->private_data;
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2010-11-24 13:57:00 -07:00
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struct fuse_conn *fc = get_fuse_conn(inode);
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2009-04-28 08:56:37 -06:00
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if (ff->open_flags & FOPEN_DIRECT_IO)
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2005-11-07 01:59:51 -07:00
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file->f_op = &fuse_direct_io_file_operations;
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2009-04-28 08:56:37 -06:00
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if (!(ff->open_flags & FOPEN_KEEP_CACHE))
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2007-10-17 00:31:01 -06:00
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invalidate_inode_pages2(inode->i_mapping);
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2009-04-28 08:56:37 -06:00
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if (ff->open_flags & FOPEN_NONSEEKABLE)
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2008-10-16 08:08:57 -06:00
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nonseekable_open(inode, file);
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2010-11-24 13:57:00 -07:00
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if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
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struct fuse_inode *fi = get_fuse_inode(inode);
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spin_lock(&fc->lock);
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fi->attr_version = ++fc->attr_version;
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i_size_write(inode, 0);
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spin_unlock(&fc->lock);
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fuse_invalidate_attr(inode);
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2014-04-28 06:19:22 -06:00
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if (fc->writeback_cache)
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file_update_time(file);
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2010-11-24 13:57:00 -07:00
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}
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2013-10-10 07:12:18 -06:00
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if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
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fuse_link_write_file(file);
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2005-11-07 01:59:51 -07:00
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}
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2009-04-28 08:56:37 -06:00
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int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
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2005-11-07 01:59:51 -07:00
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{
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2008-11-26 04:03:55 -07:00
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struct fuse_conn *fc = get_fuse_conn(inode);
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2005-09-09 14:10:30 -06:00
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int err;
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2014-04-28 06:19:22 -06:00
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bool lock_inode = (file->f_flags & O_TRUNC) &&
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fc->atomic_o_trunc &&
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fc->writeback_cache;
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2005-09-09 14:10:30 -06:00
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err = generic_file_open(inode, file);
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if (err)
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return err;
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2014-04-28 06:19:22 -06:00
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if (lock_inode)
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mutex_lock(&inode->i_mutex);
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2009-04-28 08:56:37 -06:00
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err = fuse_do_open(fc, get_node_id(inode), file, isdir);
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2005-09-09 14:10:30 -06:00
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2014-04-28 06:19:22 -06:00
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if (!err)
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fuse_finish_open(inode, file);
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2009-04-28 08:56:37 -06:00
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2014-04-28 06:19:22 -06:00
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if (lock_inode)
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mutex_unlock(&inode->i_mutex);
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return err;
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2005-09-09 14:10:30 -06:00
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}
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2009-04-28 08:56:39 -06:00
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static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode)
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2006-01-16 23:14:42 -07:00
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{
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2009-04-28 08:56:39 -06:00
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struct fuse_conn *fc = ff->fc;
|
2006-06-25 06:48:52 -06:00
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struct fuse_req *req = ff->reserved_req;
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2008-02-06 02:38:39 -07:00
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struct fuse_release_in *inarg = &req->misc.release.in;
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2005-09-09 14:10:30 -06:00
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2009-04-28 08:56:39 -06:00
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spin_lock(&fc->lock);
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list_del(&ff->write_entry);
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if (!RB_EMPTY_NODE(&ff->polled_node))
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rb_erase(&ff->polled_node, &fc->polled_files);
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spin_unlock(&fc->lock);
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2011-03-01 17:43:52 -07:00
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wake_up_interruptible_all(&ff->poll_wait);
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2009-04-28 08:56:39 -06:00
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2005-09-09 14:10:30 -06:00
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inarg->fh = ff->fh;
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2005-11-07 01:59:51 -07:00
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inarg->flags = flags;
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2006-06-25 06:48:50 -06:00
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req->in.h.opcode = opcode;
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2009-04-28 08:56:37 -06:00
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req->in.h.nodeid = ff->nodeid;
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2005-09-09 14:10:30 -06:00
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req->in.numargs = 1;
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req->in.args[0].size = sizeof(struct fuse_release_in);
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req->in.args[0].value = inarg;
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2005-11-07 01:59:51 -07:00
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|
|
}
|
|
|
|
|
2009-04-28 08:56:39 -06:00
|
|
|
void fuse_release_common(struct file *file, int opcode)
|
2005-11-07 01:59:51 -07:00
|
|
|
{
|
2009-04-13 19:54:49 -06:00
|
|
|
struct fuse_file *ff;
|
|
|
|
struct fuse_req *req;
|
2005-09-09 14:10:30 -06:00
|
|
|
|
2009-04-13 19:54:49 -06:00
|
|
|
ff = file->private_data;
|
|
|
|
if (unlikely(!ff))
|
2009-04-28 08:56:39 -06:00
|
|
|
return;
|
2009-04-13 19:54:49 -06:00
|
|
|
|
|
|
|
req = ff->reserved_req;
|
2009-04-28 08:56:39 -06:00
|
|
|
fuse_prepare_release(ff, file->f_flags, opcode);
|
2009-04-13 19:54:49 -06:00
|
|
|
|
2011-08-08 08:08:08 -06:00
|
|
|
if (ff->flock) {
|
|
|
|
struct fuse_release_in *inarg = &req->misc.release.in;
|
|
|
|
inarg->release_flags |= FUSE_RELEASE_FLOCK_UNLOCK;
|
|
|
|
inarg->lock_owner = fuse_lock_owner_id(ff->fc,
|
|
|
|
(fl_owner_t) file);
|
|
|
|
}
|
2009-04-13 19:54:49 -06:00
|
|
|
/* Hold vfsmount and dentry until release is finished */
|
2009-04-28 08:56:36 -06:00
|
|
|
path_get(&file->f_path);
|
|
|
|
req->misc.release.path = file->f_path;
|
2009-04-13 19:54:49 -06:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Normally this will send the RELEASE request, however if
|
|
|
|
* some asynchronous READ or WRITE requests are outstanding,
|
|
|
|
* the sending will be delayed.
|
2011-02-25 06:44:58 -07:00
|
|
|
*
|
|
|
|
* Make the release synchronous if this is a fuseblk mount,
|
|
|
|
* synchronous RELEASE is allowed (and desirable) in this case
|
|
|
|
* because the server can be trusted not to screw up.
|
2009-04-13 19:54:49 -06:00
|
|
|
*/
|
2011-02-25 06:44:58 -07:00
|
|
|
fuse_file_put(ff, ff->fc->destroy_req != NULL);
|
2005-09-09 14:10:30 -06:00
|
|
|
}
|
|
|
|
|
2005-09-09 14:10:36 -06:00
|
|
|
static int fuse_open(struct inode *inode, struct file *file)
|
|
|
|
{
|
2009-04-28 08:56:37 -06:00
|
|
|
return fuse_open_common(inode, file, false);
|
2005-09-09 14:10:36 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_release(struct inode *inode, struct file *file)
|
|
|
|
{
|
2013-10-10 07:19:06 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
|
|
|
|
/* see fuse_vma_close() for !writeback_cache case */
|
|
|
|
if (fc->writeback_cache)
|
2014-04-28 06:19:23 -06:00
|
|
|
write_inode_now(inode, 1);
|
2013-12-26 08:51:11 -07:00
|
|
|
|
2009-04-28 08:56:39 -06:00
|
|
|
fuse_release_common(file, FUSE_RELEASE);
|
|
|
|
|
|
|
|
/* return value is ignored by VFS */
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
void fuse_sync_release(struct fuse_file *ff, int flags)
|
|
|
|
{
|
|
|
|
WARN_ON(atomic_read(&ff->count) > 1);
|
|
|
|
fuse_prepare_release(ff, flags, FUSE_RELEASE);
|
|
|
|
ff->reserved_req->force = 1;
|
2013-03-21 08:02:04 -06:00
|
|
|
ff->reserved_req->background = 0;
|
2009-04-28 08:56:39 -06:00
|
|
|
fuse_request_send(ff->fc, ff->reserved_req);
|
|
|
|
fuse_put_request(ff->fc, ff->reserved_req);
|
|
|
|
kfree(ff);
|
2005-09-09 14:10:36 -06:00
|
|
|
}
|
2009-04-13 19:54:53 -06:00
|
|
|
EXPORT_SYMBOL_GPL(fuse_sync_release);
|
2005-09-09 14:10:36 -06:00
|
|
|
|
2006-06-25 06:48:52 -06:00
|
|
|
/*
|
2006-06-25 06:48:55 -06:00
|
|
|
* Scramble the ID space with XTEA, so that the value of the files_struct
|
|
|
|
* pointer is not exposed to userspace.
|
2006-06-25 06:48:52 -06:00
|
|
|
*/
|
2007-10-18 04:07:04 -06:00
|
|
|
u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
|
2006-06-25 06:48:52 -06:00
|
|
|
{
|
2006-06-25 06:48:55 -06:00
|
|
|
u32 *k = fc->scramble_key;
|
|
|
|
u64 v = (unsigned long) id;
|
|
|
|
u32 v0 = v;
|
|
|
|
u32 v1 = v >> 32;
|
|
|
|
u32 sum = 0;
|
|
|
|
int i;
|
|
|
|
|
|
|
|
for (i = 0; i < 32; i++) {
|
|
|
|
v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + k[sum & 3]);
|
|
|
|
sum += 0x9E3779B9;
|
|
|
|
v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + k[sum>>11 & 3]);
|
|
|
|
}
|
|
|
|
|
|
|
|
return (u64) v0 + ((u64) v1 << 32);
|
2006-06-25 06:48:52 -06:00
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
/*
|
2013-10-10 07:12:05 -06:00
|
|
|
* Check if any page in a range is under writeback
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
*
|
|
|
|
* This is currently done by walking the list of writepage requests
|
|
|
|
* for the inode, which can be pretty inefficient.
|
|
|
|
*/
|
2013-10-10 07:12:05 -06:00
|
|
|
static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from,
|
|
|
|
pgoff_t idx_to)
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
struct fuse_req *req;
|
|
|
|
bool found = false;
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
list_for_each_entry(req, &fi->writepages, writepages_entry) {
|
|
|
|
pgoff_t curr_index;
|
|
|
|
|
|
|
|
BUG_ON(req->inode != inode);
|
|
|
|
curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT;
|
2013-10-10 07:12:05 -06:00
|
|
|
if (idx_from < curr_index + req->num_pages &&
|
|
|
|
curr_index <= idx_to) {
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
found = true;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
|
|
|
return found;
|
|
|
|
}
|
|
|
|
|
2013-10-10 07:12:05 -06:00
|
|
|
static inline bool fuse_page_is_writeback(struct inode *inode, pgoff_t index)
|
|
|
|
{
|
|
|
|
return fuse_range_is_writeback(inode, index, index);
|
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
/*
|
|
|
|
* Wait for page writeback to be completed.
|
|
|
|
*
|
|
|
|
* Since fuse doesn't rely on the VM writeback tracking, this has to
|
|
|
|
* use some other means.
|
|
|
|
*/
|
|
|
|
static int fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index)
|
|
|
|
{
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
|
|
|
|
wait_event(fi->page_waitq, !fuse_page_is_writeback(inode, index));
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2013-10-10 07:11:54 -06:00
|
|
|
/*
|
|
|
|
* Wait for all pending writepages on the inode to finish.
|
|
|
|
*
|
|
|
|
* This is currently done by blocking further writes with FUSE_NOWRITE
|
|
|
|
* and waiting for all sent writes to complete.
|
|
|
|
*
|
|
|
|
* This must be called under i_mutex, otherwise the FUSE_NOWRITE usage
|
|
|
|
* could conflict with truncation.
|
|
|
|
*/
|
|
|
|
static void fuse_sync_writes(struct inode *inode)
|
|
|
|
{
|
|
|
|
fuse_set_nowrite(inode);
|
|
|
|
fuse_release_nowrite(inode);
|
|
|
|
}
|
|
|
|
|
2006-06-23 03:05:12 -06:00
|
|
|
static int fuse_flush(struct file *file, fl_owner_t id)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2005-09-09 14:10:30 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_flush_in inarg;
|
|
|
|
int err;
|
|
|
|
|
2006-01-06 01:19:39 -07:00
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
2005-09-09 14:10:30 -06:00
|
|
|
if (fc->no_flush)
|
|
|
|
return 0;
|
|
|
|
|
2014-04-28 06:19:23 -06:00
|
|
|
err = write_inode_now(inode, 1);
|
2013-10-10 07:11:54 -06:00
|
|
|
if (err)
|
|
|
|
return err;
|
|
|
|
|
|
|
|
mutex_lock(&inode->i_mutex);
|
|
|
|
fuse_sync_writes(inode);
|
|
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nofail_nopages(fc, file);
|
2005-09-09 14:10:30 -06:00
|
|
|
memset(&inarg, 0, sizeof(inarg));
|
|
|
|
inarg.fh = ff->fh;
|
2006-06-25 06:48:55 -06:00
|
|
|
inarg.lock_owner = fuse_lock_owner_id(fc, id);
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.h.opcode = FUSE_FLUSH;
|
|
|
|
req->in.h.nodeid = get_node_id(inode);
|
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
2006-06-25 06:48:52 -06:00
|
|
|
req->force = 1;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2005-09-09 14:10:30 -06:00
|
|
|
err = req->out.h.error;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
if (err == -ENOSYS) {
|
|
|
|
fc->no_flush = 1;
|
|
|
|
err = 0;
|
|
|
|
}
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2011-07-16 18:44:56 -06:00
|
|
|
int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
|
|
|
|
int datasync, int isdir)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2010-05-26 09:53:25 -06:00
|
|
|
struct inode *inode = file->f_mapping->host;
|
2005-09-09 14:10:30 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_fsync_in inarg;
|
|
|
|
int err;
|
|
|
|
|
2006-01-06 01:19:39 -07:00
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
2011-07-16 18:44:56 -06:00
|
|
|
mutex_lock(&inode->i_mutex);
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
/*
|
|
|
|
* Start writeback against all dirty pages of the inode, then
|
|
|
|
* wait for all outstanding writes, before sending the FSYNC
|
|
|
|
* request.
|
|
|
|
*/
|
2014-04-28 06:19:23 -06:00
|
|
|
err = filemap_write_and_wait_range(inode->i_mapping, start, end);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
if (err)
|
2011-07-16 18:44:56 -06:00
|
|
|
goto out;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
fuse_sync_writes(inode);
|
2014-04-28 06:19:23 -06:00
|
|
|
err = sync_inode_metadata(inode, 1);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
2014-04-28 06:19:23 -06:00
|
|
|
if ((!isdir && fc->no_fsync) || (isdir && fc->no_fsyncdir))
|
|
|
|
goto out;
|
2013-12-26 08:51:11 -07:00
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2011-07-16 18:44:56 -06:00
|
|
|
if (IS_ERR(req)) {
|
|
|
|
err = PTR_ERR(req);
|
|
|
|
goto out;
|
|
|
|
}
|
2005-09-09 14:10:30 -06:00
|
|
|
|
|
|
|
memset(&inarg, 0, sizeof(inarg));
|
|
|
|
inarg.fh = ff->fh;
|
|
|
|
inarg.fsync_flags = datasync ? 1 : 0;
|
2005-09-09 14:10:38 -06:00
|
|
|
req->in.h.opcode = isdir ? FUSE_FSYNCDIR : FUSE_FSYNC;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.h.nodeid = get_node_id(inode);
|
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2005-09-09 14:10:30 -06:00
|
|
|
err = req->out.h.error;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
if (err == -ENOSYS) {
|
2005-09-09 14:10:38 -06:00
|
|
|
if (isdir)
|
|
|
|
fc->no_fsyncdir = 1;
|
|
|
|
else
|
|
|
|
fc->no_fsync = 1;
|
2005-09-09 14:10:30 -06:00
|
|
|
err = 0;
|
|
|
|
}
|
2011-07-16 18:44:56 -06:00
|
|
|
out:
|
|
|
|
mutex_unlock(&inode->i_mutex);
|
2005-09-09 14:10:30 -06:00
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2011-07-16 18:44:56 -06:00
|
|
|
static int fuse_fsync(struct file *file, loff_t start, loff_t end,
|
|
|
|
int datasync)
|
2005-09-09 14:10:38 -06:00
|
|
|
{
|
2011-07-16 18:44:56 -06:00
|
|
|
return fuse_fsync_common(file, start, end, datasync, 0);
|
2005-09-09 14:10:38 -06:00
|
|
|
}
|
|
|
|
|
2009-04-28 08:56:37 -06:00
|
|
|
void fuse_read_fill(struct fuse_req *req, struct file *file, loff_t pos,
|
|
|
|
size_t count, int opcode)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2008-04-30 01:54:43 -06:00
|
|
|
struct fuse_read_in *inarg = &req->misc.read.in;
|
2007-11-28 17:22:00 -07:00
|
|
|
struct fuse_file *ff = file->private_data;
|
2005-09-09 14:10:30 -06:00
|
|
|
|
2006-01-16 23:14:45 -07:00
|
|
|
inarg->fh = ff->fh;
|
|
|
|
inarg->offset = pos;
|
|
|
|
inarg->size = count;
|
2007-11-28 17:22:00 -07:00
|
|
|
inarg->flags = file->f_flags;
|
2006-01-16 23:14:45 -07:00
|
|
|
req->in.h.opcode = opcode;
|
2009-04-28 08:56:37 -06:00
|
|
|
req->in.h.nodeid = ff->nodeid;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(struct fuse_read_in);
|
2006-01-16 23:14:46 -07:00
|
|
|
req->in.args[0].value = inarg;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->out.argvar = 1;
|
|
|
|
req->out.numargs = 1;
|
|
|
|
req->out.args[0].size = count;
|
|
|
|
}
|
|
|
|
|
2012-12-14 08:20:25 -07:00
|
|
|
static void fuse_release_user_pages(struct fuse_req *req, int write)
|
|
|
|
{
|
|
|
|
unsigned i;
|
|
|
|
|
|
|
|
for (i = 0; i < req->num_pages; i++) {
|
|
|
|
struct page *page = req->pages[i];
|
|
|
|
if (write)
|
|
|
|
set_page_dirty_lock(page);
|
|
|
|
put_page(page);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2012-12-14 08:20:41 -07:00
|
|
|
/**
|
|
|
|
* In case of short read, the caller sets 'pos' to the position of
|
|
|
|
* actual end of fuse request in IO request. Otherwise, if bytes_requested
|
|
|
|
* == bytes_transferred or rw == WRITE, the caller sets 'pos' to -1.
|
|
|
|
*
|
|
|
|
* An example:
|
|
|
|
* User requested DIO read of 64K. It was splitted into two 32K fuse requests,
|
|
|
|
* both submitted asynchronously. The first of them was ACKed by userspace as
|
|
|
|
* fully completed (req->out.args[0].size == 32K) resulting in pos == -1. The
|
|
|
|
* second request was ACKed as short, e.g. only 1K was read, resulting in
|
|
|
|
* pos == 33K.
|
|
|
|
*
|
|
|
|
* Thus, when all fuse requests are completed, the minimal non-negative 'pos'
|
|
|
|
* will be equal to the length of the longest contiguous fragment of
|
|
|
|
* transferred data starting from the beginning of IO request.
|
|
|
|
*/
|
|
|
|
static void fuse_aio_complete(struct fuse_io_priv *io, int err, ssize_t pos)
|
|
|
|
{
|
|
|
|
int left;
|
|
|
|
|
|
|
|
spin_lock(&io->lock);
|
|
|
|
if (err)
|
|
|
|
io->err = io->err ? : err;
|
|
|
|
else if (pos >= 0 && (io->bytes < 0 || pos < io->bytes))
|
|
|
|
io->bytes = pos;
|
|
|
|
|
|
|
|
left = --io->reqs;
|
|
|
|
spin_unlock(&io->lock);
|
|
|
|
|
|
|
|
if (!left) {
|
|
|
|
long res;
|
|
|
|
|
|
|
|
if (io->err)
|
|
|
|
res = io->err;
|
|
|
|
else if (io->bytes >= 0 && io->write)
|
|
|
|
res = -EIO;
|
|
|
|
else {
|
|
|
|
res = io->bytes < 0 ? io->size : io->bytes;
|
|
|
|
|
|
|
|
if (!is_sync_kiocb(io->iocb)) {
|
2013-06-16 10:05:23 -06:00
|
|
|
struct inode *inode = file_inode(io->iocb->ki_filp);
|
2012-12-14 08:20:41 -07:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
fi->attr_version = ++fc->attr_version;
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
aio_complete(io->iocb, res, 0);
|
|
|
|
kfree(io);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static void fuse_aio_complete_req(struct fuse_conn *fc, struct fuse_req *req)
|
|
|
|
{
|
|
|
|
struct fuse_io_priv *io = req->io;
|
|
|
|
ssize_t pos = -1;
|
|
|
|
|
|
|
|
fuse_release_user_pages(req, !io->write);
|
|
|
|
|
|
|
|
if (io->write) {
|
|
|
|
if (req->misc.write.in.size != req->misc.write.out.size)
|
|
|
|
pos = req->misc.write.in.offset - io->offset +
|
|
|
|
req->misc.write.out.size;
|
|
|
|
} else {
|
|
|
|
if (req->misc.read.in.size != req->out.args[0].size)
|
|
|
|
pos = req->misc.read.in.offset - io->offset +
|
|
|
|
req->out.args[0].size;
|
|
|
|
}
|
|
|
|
|
|
|
|
fuse_aio_complete(io, req->out.h.error, pos);
|
|
|
|
}
|
|
|
|
|
|
|
|
static size_t fuse_async_req_send(struct fuse_conn *fc, struct fuse_req *req,
|
|
|
|
size_t num_bytes, struct fuse_io_priv *io)
|
|
|
|
{
|
|
|
|
spin_lock(&io->lock);
|
|
|
|
io->size += num_bytes;
|
|
|
|
io->reqs++;
|
|
|
|
spin_unlock(&io->lock);
|
|
|
|
|
|
|
|
req->io = io;
|
|
|
|
req->end = fuse_aio_complete_req;
|
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
__fuse_get_request(req);
|
2012-12-14 08:20:41 -07:00
|
|
|
fuse_request_send_background(fc, req);
|
|
|
|
|
|
|
|
return num_bytes;
|
|
|
|
}
|
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
static size_t fuse_send_read(struct fuse_req *req, struct fuse_io_priv *io,
|
2009-04-28 08:56:37 -06:00
|
|
|
loff_t pos, size_t count, fl_owner_t owner)
|
2005-09-09 14:10:36 -06:00
|
|
|
{
|
2012-12-14 08:20:51 -07:00
|
|
|
struct file *file = io->file;
|
2009-04-28 08:56:37 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_conn *fc = ff->fc;
|
2007-10-18 04:07:04 -06:00
|
|
|
|
2009-04-28 08:56:37 -06:00
|
|
|
fuse_read_fill(req, file, pos, count, FUSE_READ);
|
2007-10-18 04:07:04 -06:00
|
|
|
if (owner != NULL) {
|
2008-04-30 01:54:43 -06:00
|
|
|
struct fuse_read_in *inarg = &req->misc.read.in;
|
2007-10-18 04:07:04 -06:00
|
|
|
|
|
|
|
inarg->read_flags |= FUSE_READ_LOCKOWNER;
|
|
|
|
inarg->lock_owner = fuse_lock_owner_id(fc, owner);
|
|
|
|
}
|
2012-12-14 08:20:51 -07:00
|
|
|
|
|
|
|
if (io->async)
|
|
|
|
return fuse_async_req_send(fc, req, count, io);
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2006-01-16 23:14:45 -07:00
|
|
|
return req->out.args[0].size;
|
2005-09-09 14:10:36 -06:00
|
|
|
}
|
|
|
|
|
2008-04-30 01:54:43 -06:00
|
|
|
static void fuse_read_update_size(struct inode *inode, loff_t size,
|
|
|
|
u64 attr_ver)
|
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
fuse: hotfix truncate_pagecache() issue
The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.
The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:
1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.
The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:
1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.
The result will be the lost of data user wrote on the fourth step.
The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).
Changed in v2:
- improved patch description to cover both sides of the issue.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
2013-08-30 07:06:04 -06:00
|
|
|
if (attr_ver == fi->attr_version && size < inode->i_size &&
|
|
|
|
!test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
|
2008-04-30 01:54:43 -06:00
|
|
|
fi->attr_version = ++fc->attr_version;
|
|
|
|
i_size_write(inode, size);
|
|
|
|
}
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
}
|
|
|
|
|
2013-10-10 07:10:16 -06:00
|
|
|
static void fuse_short_read(struct fuse_req *req, struct inode *inode,
|
|
|
|
u64 attr_ver)
|
|
|
|
{
|
|
|
|
size_t num_read = req->out.args[0].size;
|
2013-10-10 07:10:46 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
|
|
|
|
if (fc->writeback_cache) {
|
|
|
|
/*
|
|
|
|
* A hole in a file. Some data after the hole are in page cache,
|
|
|
|
* but have not reached the client fs yet. So, the hole is not
|
|
|
|
* present there.
|
|
|
|
*/
|
|
|
|
int i;
|
|
|
|
int start_idx = num_read >> PAGE_CACHE_SHIFT;
|
|
|
|
size_t off = num_read & (PAGE_CACHE_SIZE - 1);
|
2013-10-10 07:10:16 -06:00
|
|
|
|
2013-10-10 07:10:46 -06:00
|
|
|
for (i = start_idx; i < req->num_pages; i++) {
|
|
|
|
zero_user_segment(req->pages[i], off, PAGE_CACHE_SIZE);
|
|
|
|
off = 0;
|
|
|
|
}
|
|
|
|
} else {
|
|
|
|
loff_t pos = page_offset(req->pages[0]) + num_read;
|
|
|
|
fuse_read_update_size(inode, pos, attr_ver);
|
|
|
|
}
|
2013-10-10 07:10:16 -06:00
|
|
|
}
|
|
|
|
|
2013-10-10 07:11:25 -06:00
|
|
|
static int fuse_do_readpage(struct file *file, struct page *page)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2012-12-14 08:20:51 -07:00
|
|
|
struct fuse_io_priv io = { .async = 0, .file = file };
|
2005-09-09 14:10:30 -06:00
|
|
|
struct inode *inode = page->mapping->host;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
2006-01-06 01:19:39 -07:00
|
|
|
struct fuse_req *req;
|
2008-04-30 01:54:43 -06:00
|
|
|
size_t num_read;
|
|
|
|
loff_t pos = page_offset(page);
|
|
|
|
size_t count = PAGE_CACHE_SIZE;
|
|
|
|
u64 attr_ver;
|
2006-01-06 01:19:39 -07:00
|
|
|
int err;
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
/*
|
2011-03-30 19:57:33 -06:00
|
|
|
* Page writeback can extend beyond the lifetime of the
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
* page-cache page, so make sure we read a properly synced
|
|
|
|
* page.
|
|
|
|
*/
|
|
|
|
fuse_wait_on_page_writeback(inode, page->index);
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req(fc, 1);
|
2006-04-10 23:54:58 -06:00
|
|
|
if (IS_ERR(req))
|
2013-10-10 07:11:25 -06:00
|
|
|
return PTR_ERR(req);
|
2005-09-09 14:10:30 -06:00
|
|
|
|
2008-04-30 01:54:43 -06:00
|
|
|
attr_ver = fuse_get_attr_version(fc);
|
|
|
|
|
2005-09-09 14:10:30 -06:00
|
|
|
req->out.page_zeroing = 1;
|
2009-04-02 06:25:34 -06:00
|
|
|
req->out.argpages = 1;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->num_pages = 1;
|
|
|
|
req->pages[0] = page;
|
2012-10-26 09:49:33 -06:00
|
|
|
req->page_descs[0].length = count;
|
2012-12-14 08:20:51 -07:00
|
|
|
num_read = fuse_send_read(req, &io, pos, count, NULL);
|
2005-09-09 14:10:30 -06:00
|
|
|
err = req->out.h.error;
|
2008-04-30 01:54:43 -06:00
|
|
|
|
|
|
|
if (!err) {
|
|
|
|
/*
|
|
|
|
* Short read means EOF. If file size is larger, truncate it
|
|
|
|
*/
|
|
|
|
if (num_read < count)
|
2013-10-10 07:10:16 -06:00
|
|
|
fuse_short_read(req, inode, attr_ver);
|
2008-04-30 01:54:43 -06:00
|
|
|
|
2005-09-09 14:10:30 -06:00
|
|
|
SetPageUptodate(page);
|
2008-04-30 01:54:43 -06:00
|
|
|
}
|
|
|
|
|
2013-10-10 07:10:16 -06:00
|
|
|
fuse_put_request(fc, req);
|
2013-10-10 07:11:25 -06:00
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_readpage(struct file *file, struct page *page)
|
|
|
|
{
|
|
|
|
struct inode *inode = page->mapping->host;
|
|
|
|
int err;
|
|
|
|
|
|
|
|
err = -EIO;
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
err = fuse_do_readpage(file, page);
|
2013-11-05 04:55:43 -07:00
|
|
|
fuse_invalidate_atime(inode);
|
2005-09-09 14:10:30 -06:00
|
|
|
out:
|
|
|
|
unlock_page(page);
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2006-01-16 23:14:46 -07:00
|
|
|
static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
|
2005-09-09 14:10:33 -06:00
|
|
|
{
|
2006-01-16 23:14:46 -07:00
|
|
|
int i;
|
2008-04-30 01:54:43 -06:00
|
|
|
size_t count = req->misc.read.in.size;
|
|
|
|
size_t num_read = req->out.args[0].size;
|
2010-05-25 07:06:07 -06:00
|
|
|
struct address_space *mapping = NULL;
|
2006-01-16 23:14:46 -07:00
|
|
|
|
2010-05-25 07:06:07 -06:00
|
|
|
for (i = 0; mapping == NULL && i < req->num_pages; i++)
|
|
|
|
mapping = req->pages[i]->mapping;
|
2008-04-30 01:54:43 -06:00
|
|
|
|
2010-05-25 07:06:07 -06:00
|
|
|
if (mapping) {
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Short read means EOF. If file size is larger, truncate it
|
|
|
|
*/
|
2013-10-10 07:10:16 -06:00
|
|
|
if (!req->out.h.error && num_read < count)
|
|
|
|
fuse_short_read(req, inode, req->misc.read.attr_ver);
|
2010-05-25 07:06:07 -06:00
|
|
|
|
2013-11-05 04:55:43 -07:00
|
|
|
fuse_invalidate_atime(inode);
|
2010-05-25 07:06:07 -06:00
|
|
|
}
|
2006-01-16 23:14:46 -07:00
|
|
|
|
2005-09-09 14:10:33 -06:00
|
|
|
for (i = 0; i < req->num_pages; i++) {
|
|
|
|
struct page *page = req->pages[i];
|
|
|
|
if (!req->out.h.error)
|
|
|
|
SetPageUptodate(page);
|
2006-01-16 23:14:46 -07:00
|
|
|
else
|
|
|
|
SetPageError(page);
|
2005-09-09 14:10:33 -06:00
|
|
|
unlock_page(page);
|
2010-05-25 07:06:06 -06:00
|
|
|
page_cache_release(page);
|
2005-09-09 14:10:33 -06:00
|
|
|
}
|
2007-10-17 00:31:00 -06:00
|
|
|
if (req->ff)
|
2011-02-25 06:44:58 -07:00
|
|
|
fuse_file_put(req->ff, false);
|
2006-01-16 23:14:46 -07:00
|
|
|
}
|
|
|
|
|
2009-04-28 08:56:37 -06:00
|
|
|
static void fuse_send_readpages(struct fuse_req *req, struct file *file)
|
2006-01-16 23:14:46 -07:00
|
|
|
{
|
2009-04-28 08:56:37 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_conn *fc = ff->fc;
|
2006-01-16 23:14:46 -07:00
|
|
|
loff_t pos = page_offset(req->pages[0]);
|
|
|
|
size_t count = req->num_pages << PAGE_CACHE_SHIFT;
|
2009-04-02 06:25:34 -06:00
|
|
|
|
|
|
|
req->out.argpages = 1;
|
2006-01-16 23:14:46 -07:00
|
|
|
req->out.page_zeroing = 1;
|
2010-05-25 07:06:07 -06:00
|
|
|
req->out.page_replace = 1;
|
2009-04-28 08:56:37 -06:00
|
|
|
fuse_read_fill(req, file, pos, count, FUSE_READ);
|
2008-04-30 01:54:43 -06:00
|
|
|
req->misc.read.attr_ver = fuse_get_attr_version(fc);
|
2006-02-01 04:04:40 -07:00
|
|
|
if (fc->async_read) {
|
2007-10-17 00:31:00 -06:00
|
|
|
req->ff = fuse_file_get(ff);
|
2006-02-01 04:04:40 -07:00
|
|
|
req->end = fuse_readpages_end;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send_background(fc, req);
|
2006-02-01 04:04:40 -07:00
|
|
|
} else {
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2006-02-01 04:04:40 -07:00
|
|
|
fuse_readpages_end(fc, req);
|
2008-11-26 04:03:54 -07:00
|
|
|
fuse_put_request(fc, req);
|
2006-02-01 04:04:40 -07:00
|
|
|
}
|
2005-09-09 14:10:33 -06:00
|
|
|
}
|
|
|
|
|
2007-10-17 00:31:00 -06:00
|
|
|
struct fuse_fill_data {
|
2005-09-09 14:10:33 -06:00
|
|
|
struct fuse_req *req;
|
2007-11-28 17:22:00 -07:00
|
|
|
struct file *file;
|
2005-09-09 14:10:33 -06:00
|
|
|
struct inode *inode;
|
2012-10-26 09:48:51 -06:00
|
|
|
unsigned nr_pages;
|
2005-09-09 14:10:33 -06:00
|
|
|
};
|
|
|
|
|
|
|
|
static int fuse_readpages_fill(void *_data, struct page *page)
|
|
|
|
{
|
2007-10-17 00:31:00 -06:00
|
|
|
struct fuse_fill_data *data = _data;
|
2005-09-09 14:10:33 -06:00
|
|
|
struct fuse_req *req = data->req;
|
|
|
|
struct inode *inode = data->inode;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
fuse_wait_on_page_writeback(inode, page->index);
|
|
|
|
|
2005-09-09 14:10:33 -06:00
|
|
|
if (req->num_pages &&
|
|
|
|
(req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
|
|
|
|
(req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
|
|
|
|
req->pages[req->num_pages - 1]->index + 1 != page->index)) {
|
2012-10-26 09:48:51 -06:00
|
|
|
int nr_alloc = min_t(unsigned, data->nr_pages,
|
|
|
|
FUSE_MAX_PAGES_PER_REQ);
|
2009-04-28 08:56:37 -06:00
|
|
|
fuse_send_readpages(req, data->file);
|
2013-03-21 08:02:04 -06:00
|
|
|
if (fc->async_read)
|
|
|
|
req = fuse_get_req_for_background(fc, nr_alloc);
|
|
|
|
else
|
|
|
|
req = fuse_get_req(fc, nr_alloc);
|
|
|
|
|
|
|
|
data->req = req;
|
2006-04-10 23:54:58 -06:00
|
|
|
if (IS_ERR(req)) {
|
2005-09-09 14:10:33 -06:00
|
|
|
unlock_page(page);
|
2006-04-10 23:54:58 -06:00
|
|
|
return PTR_ERR(req);
|
2005-09-09 14:10:33 -06:00
|
|
|
}
|
|
|
|
}
|
2012-10-26 09:48:51 -06:00
|
|
|
|
|
|
|
if (WARN_ON(req->num_pages >= req->max_pages)) {
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
return -EIO;
|
|
|
|
}
|
|
|
|
|
2010-05-25 07:06:06 -06:00
|
|
|
page_cache_get(page);
|
2005-09-09 14:10:33 -06:00
|
|
|
req->pages[req->num_pages] = page;
|
2012-10-26 09:49:33 -06:00
|
|
|
req->page_descs[req->num_pages].length = PAGE_SIZE;
|
2008-11-26 04:03:54 -07:00
|
|
|
req->num_pages++;
|
2012-10-26 09:48:51 -06:00
|
|
|
data->nr_pages--;
|
2005-09-09 14:10:33 -06:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_readpages(struct file *file, struct address_space *mapping,
|
|
|
|
struct list_head *pages, unsigned nr_pages)
|
|
|
|
{
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
2007-10-17 00:31:00 -06:00
|
|
|
struct fuse_fill_data data;
|
2005-09-09 14:10:33 -06:00
|
|
|
int err;
|
2012-10-26 09:48:51 -06:00
|
|
|
int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
|
2006-01-06 01:19:39 -07:00
|
|
|
|
2006-08-14 00:24:27 -06:00
|
|
|
err = -EIO;
|
2006-01-06 01:19:39 -07:00
|
|
|
if (is_bad_inode(inode))
|
2006-11-02 23:07:09 -07:00
|
|
|
goto out;
|
2006-01-06 01:19:39 -07:00
|
|
|
|
2007-11-28 17:22:00 -07:00
|
|
|
data.file = file;
|
2005-09-09 14:10:33 -06:00
|
|
|
data.inode = inode;
|
2013-03-21 08:02:04 -06:00
|
|
|
if (fc->async_read)
|
|
|
|
data.req = fuse_get_req_for_background(fc, nr_alloc);
|
|
|
|
else
|
|
|
|
data.req = fuse_get_req(fc, nr_alloc);
|
2012-10-26 09:48:51 -06:00
|
|
|
data.nr_pages = nr_pages;
|
2006-08-14 00:24:27 -06:00
|
|
|
err = PTR_ERR(data.req);
|
2006-04-10 23:54:58 -06:00
|
|
|
if (IS_ERR(data.req))
|
2006-11-02 23:07:09 -07:00
|
|
|
goto out;
|
2005-09-09 14:10:33 -06:00
|
|
|
|
|
|
|
err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
|
2006-04-10 23:54:49 -06:00
|
|
|
if (!err) {
|
|
|
|
if (data.req->num_pages)
|
2009-04-28 08:56:37 -06:00
|
|
|
fuse_send_readpages(data.req, file);
|
2006-04-10 23:54:49 -06:00
|
|
|
else
|
|
|
|
fuse_put_request(fc, data.req);
|
|
|
|
}
|
2006-11-02 23:07:09 -07:00
|
|
|
out:
|
2006-08-14 00:24:27 -06:00
|
|
|
return err;
|
2005-09-09 14:10:33 -06:00
|
|
|
}
|
|
|
|
|
2007-11-28 17:21:59 -07:00
|
|
|
static ssize_t fuse_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
|
|
|
|
unsigned long nr_segs, loff_t pos)
|
|
|
|
{
|
|
|
|
struct inode *inode = iocb->ki_filp->f_mapping->host;
|
2012-07-16 13:23:50 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
2007-11-28 17:21:59 -07:00
|
|
|
|
2012-07-16 13:23:50 -06:00
|
|
|
/*
|
|
|
|
* In auto invalidate mode, always update attributes on read.
|
|
|
|
* Otherwise, only update if we attempt to read past EOF (to ensure
|
|
|
|
* i_size is up to date).
|
|
|
|
*/
|
|
|
|
if (fc->auto_inval_data ||
|
|
|
|
(pos + iov_length(iov, nr_segs) > i_size_read(inode))) {
|
2007-11-28 17:21:59 -07:00
|
|
|
int err;
|
|
|
|
err = fuse_update_attributes(inode, NULL, iocb->ki_filp, NULL);
|
|
|
|
if (err)
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
return generic_file_aio_read(iocb, iov, nr_segs, pos);
|
|
|
|
}
|
|
|
|
|
2009-04-28 08:56:36 -06:00
|
|
|
static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
|
2009-04-28 08:56:37 -06:00
|
|
|
loff_t pos, size_t count)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2007-10-18 04:07:03 -06:00
|
|
|
struct fuse_write_in *inarg = &req->misc.write.in;
|
|
|
|
struct fuse_write_out *outarg = &req->misc.write.out;
|
2005-09-09 14:10:30 -06:00
|
|
|
|
2007-10-18 04:07:03 -06:00
|
|
|
inarg->fh = ff->fh;
|
|
|
|
inarg->offset = pos;
|
|
|
|
inarg->size = count;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.h.opcode = FUSE_WRITE;
|
2009-04-28 08:56:37 -06:00
|
|
|
req->in.h.nodeid = ff->nodeid;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.numargs = 2;
|
2009-04-28 08:56:37 -06:00
|
|
|
if (ff->fc->minor < 9)
|
2007-10-18 04:07:04 -06:00
|
|
|
req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
|
|
|
|
else
|
|
|
|
req->in.args[0].size = sizeof(struct fuse_write_in);
|
2007-10-18 04:07:03 -06:00
|
|
|
req->in.args[0].value = inarg;
|
2005-09-09 14:10:30 -06:00
|
|
|
req->in.args[1].size = count;
|
|
|
|
req->out.numargs = 1;
|
|
|
|
req->out.args[0].size = sizeof(struct fuse_write_out);
|
2007-10-18 04:07:03 -06:00
|
|
|
req->out.args[0].value = outarg;
|
|
|
|
}
|
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
static size_t fuse_send_write(struct fuse_req *req, struct fuse_io_priv *io,
|
2009-04-28 08:56:37 -06:00
|
|
|
loff_t pos, size_t count, fl_owner_t owner)
|
2007-10-18 04:07:03 -06:00
|
|
|
{
|
2012-12-14 08:20:51 -07:00
|
|
|
struct file *file = io->file;
|
2009-04-28 08:56:37 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_conn *fc = ff->fc;
|
2009-04-28 08:56:36 -06:00
|
|
|
struct fuse_write_in *inarg = &req->misc.write.in;
|
|
|
|
|
2009-04-28 08:56:37 -06:00
|
|
|
fuse_write_fill(req, ff, pos, count);
|
2009-04-28 08:56:36 -06:00
|
|
|
inarg->flags = file->f_flags;
|
2007-10-18 04:07:04 -06:00
|
|
|
if (owner != NULL) {
|
|
|
|
inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
|
|
|
|
inarg->lock_owner = fuse_lock_owner_id(fc, owner);
|
|
|
|
}
|
2012-12-14 08:20:51 -07:00
|
|
|
|
|
|
|
if (io->async)
|
|
|
|
return fuse_async_req_send(fc, req, count, io);
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2007-10-18 04:07:03 -06:00
|
|
|
return req->misc.write.out.size;
|
2005-09-09 14:10:30 -06:00
|
|
|
}
|
|
|
|
|
2013-12-26 08:51:11 -07:00
|
|
|
bool fuse_write_update_size(struct inode *inode, loff_t pos)
|
2008-04-30 01:54:41 -06:00
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
2013-12-26 08:51:11 -07:00
|
|
|
bool ret = false;
|
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
fi->attr_version = ++fc->attr_version;
|
2013-12-26 08:51:11 -07:00
|
|
|
if (pos > inode->i_size) {
|
2008-04-30 01:54:41 -06:00
|
|
|
i_size_write(inode, pos);
|
2013-12-26 08:51:11 -07:00
|
|
|
ret = true;
|
|
|
|
}
|
2008-04-30 01:54:41 -06:00
|
|
|
spin_unlock(&fc->lock);
|
2013-12-26 08:51:11 -07:00
|
|
|
|
|
|
|
return ret;
|
2008-04-30 01:54:41 -06:00
|
|
|
}
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
|
|
|
|
struct inode *inode, loff_t pos,
|
|
|
|
size_t count)
|
|
|
|
{
|
|
|
|
size_t res;
|
|
|
|
unsigned offset;
|
|
|
|
unsigned i;
|
2012-12-14 08:20:51 -07:00
|
|
|
struct fuse_io_priv io = { .async = 0, .file = file };
|
2008-04-30 01:54:42 -06:00
|
|
|
|
|
|
|
for (i = 0; i < req->num_pages; i++)
|
|
|
|
fuse_wait_on_page_writeback(inode, req->pages[i]->index);
|
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
res = fuse_send_write(req, &io, pos, count, NULL);
|
2008-04-30 01:54:42 -06:00
|
|
|
|
2012-10-26 09:49:24 -06:00
|
|
|
offset = req->page_descs[0].offset;
|
2008-04-30 01:54:42 -06:00
|
|
|
count = res;
|
|
|
|
for (i = 0; i < req->num_pages; i++) {
|
|
|
|
struct page *page = req->pages[i];
|
|
|
|
|
|
|
|
if (!req->out.h.error && !offset && count >= PAGE_CACHE_SIZE)
|
|
|
|
SetPageUptodate(page);
|
|
|
|
|
|
|
|
if (count > PAGE_CACHE_SIZE - offset)
|
|
|
|
count -= PAGE_CACHE_SIZE - offset;
|
|
|
|
else
|
|
|
|
count = 0;
|
|
|
|
offset = 0;
|
|
|
|
|
|
|
|
unlock_page(page);
|
|
|
|
page_cache_release(page);
|
|
|
|
}
|
|
|
|
|
|
|
|
return res;
|
|
|
|
}
|
|
|
|
|
|
|
|
static ssize_t fuse_fill_write_pages(struct fuse_req *req,
|
|
|
|
struct address_space *mapping,
|
|
|
|
struct iov_iter *ii, loff_t pos)
|
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(mapping->host);
|
|
|
|
unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
|
|
|
|
size_t count = 0;
|
|
|
|
int err;
|
|
|
|
|
2009-04-02 06:25:34 -06:00
|
|
|
req->in.argpages = 1;
|
2012-10-26 09:49:24 -06:00
|
|
|
req->page_descs[0].offset = offset;
|
2008-04-30 01:54:42 -06:00
|
|
|
|
|
|
|
do {
|
|
|
|
size_t tmp;
|
|
|
|
struct page *page;
|
|
|
|
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
|
|
|
|
size_t bytes = min_t(size_t, PAGE_CACHE_SIZE - offset,
|
|
|
|
iov_iter_count(ii));
|
|
|
|
|
|
|
|
bytes = min_t(size_t, bytes, fc->max_write - count);
|
|
|
|
|
|
|
|
again:
|
|
|
|
err = -EFAULT;
|
|
|
|
if (iov_iter_fault_in_readable(ii, bytes))
|
|
|
|
break;
|
|
|
|
|
|
|
|
err = -ENOMEM;
|
fs: symlink write_begin allocation context fix
With the write_begin/write_end aops, page_symlink was broken because it
could no longer pass a GFP_NOFS type mask into the point where the
allocations happened. They are done in write_begin, which would always
assume that the filesystem can be entered from reclaim. This bug could
cause filesystem deadlocks.
The funny thing with having a gfp_t mask there is that it doesn't really
allow the caller to arbitrarily tinker with the context in which it can be
called. It couldn't ever be GFP_ATOMIC, for example, because it needs to
take the page lock. The only thing any callers care about is __GFP_FS
anyway, so turn that into a single flag.
Add a new flag for write_begin, AOP_FLAG_NOFS. Filesystems can now act on
this flag in their write_begin function. Change __grab_cache_page to
accept a nofs argument as well, to honour that flag (while we're there,
change the name to grab_cache_page_write_begin which is more instructive
and does away with random leading underscores).
This is really a more flexible way to go in the end anyway -- if a
filesystem happens to want any extra allocations aside from the pagecache
ones in ints write_begin function, it may now use GFP_KERNEL (rather than
GFP_NOFS) for common case allocations (eg. ocfs2_alloc_write_ctxt, for a
random example).
[kosaki.motohiro@jp.fujitsu.com: fix ubifs]
[kosaki.motohiro@jp.fujitsu.com: fix fuse]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: <stable@kernel.org> [2.6.28.x]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Cleaned up the calling convention: just pass in the AOP flags
untouched to the grab_cache_page_write_begin() function. That
just simplifies everybody, and may even allow future expansion of the
logic. - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-04 13:00:53 -07:00
|
|
|
page = grab_cache_page_write_begin(mapping, index, 0);
|
2008-04-30 01:54:42 -06:00
|
|
|
if (!page)
|
|
|
|
break;
|
|
|
|
|
mm: flush dcache before writing into page to avoid alias
The cache alias problem will happen if the changes of user shared mapping
is not flushed before copying, then user and kernel mapping may be mapped
into two different cache line, it is impossible to guarantee the coherence
after iov_iter_copy_from_user_atomic. So the right steps should be:
flush_dcache_page(page);
kmap_atomic(page);
write to page;
kunmap_atomic(page);
flush_dcache_page(page);
More precisely, we might create two new APIs flush_dcache_user_page and
flush_dcache_kern_page to replace the two flush_dcache_page accordingly.
Here is a snippet tested on omap2430 with VIPT cache, and I think it is
not ARM-specific:
int val = 0x11111111;
fd = open("abc", O_RDWR);
addr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
*(addr+0) = 0x44444444;
tmp = *(addr+0);
*(addr+1) = 0x77777777;
write(fd, &val, sizeof(int));
close(fd);
The results are not always 0x11111111 0x77777777 at the beginning as expected. Sometimes we see 0x44444444 0x77777777.
Signed-off-by: Anfei <anfei.zhou@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <linux-arch@vger.kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-02-02 14:44:02 -07:00
|
|
|
if (mapping_writably_mapped(mapping))
|
|
|
|
flush_dcache_page(page);
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
|
|
|
|
flush_dcache_page(page);
|
|
|
|
|
2011-07-25 14:35:35 -06:00
|
|
|
mark_page_accessed(page);
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
if (!tmp) {
|
|
|
|
unlock_page(page);
|
|
|
|
page_cache_release(page);
|
|
|
|
bytes = min(bytes, iov_iter_single_seg_count(ii));
|
|
|
|
goto again;
|
|
|
|
}
|
|
|
|
|
|
|
|
err = 0;
|
|
|
|
req->pages[req->num_pages] = page;
|
2012-10-26 09:49:33 -06:00
|
|
|
req->page_descs[req->num_pages].length = tmp;
|
2008-04-30 01:54:42 -06:00
|
|
|
req->num_pages++;
|
|
|
|
|
|
|
|
iov_iter_advance(ii, tmp);
|
|
|
|
count += tmp;
|
|
|
|
pos += tmp;
|
|
|
|
offset += tmp;
|
|
|
|
if (offset == PAGE_CACHE_SIZE)
|
|
|
|
offset = 0;
|
|
|
|
|
2008-05-12 15:02:32 -06:00
|
|
|
if (!fc->big_writes)
|
|
|
|
break;
|
2008-04-30 01:54:42 -06:00
|
|
|
} while (iov_iter_count(ii) && count < fc->max_write &&
|
2012-10-26 09:49:00 -06:00
|
|
|
req->num_pages < req->max_pages && offset == 0);
|
2008-04-30 01:54:42 -06:00
|
|
|
|
|
|
|
return count > 0 ? count : err;
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:49:00 -06:00
|
|
|
static inline unsigned fuse_wr_pages(loff_t pos, size_t len)
|
|
|
|
{
|
|
|
|
return min_t(unsigned,
|
|
|
|
((pos + len - 1) >> PAGE_CACHE_SHIFT) -
|
|
|
|
(pos >> PAGE_CACHE_SHIFT) + 1,
|
|
|
|
FUSE_MAX_PAGES_PER_REQ);
|
|
|
|
}
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
static ssize_t fuse_perform_write(struct file *file,
|
|
|
|
struct address_space *mapping,
|
|
|
|
struct iov_iter *ii, loff_t pos)
|
|
|
|
{
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
fuse: hotfix truncate_pagecache() issue
The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.
The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:
1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.
The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:
1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.
The result will be the lost of data user wrote on the fourth step.
The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).
Changed in v2:
- improved patch description to cover both sides of the issue.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
2013-08-30 07:06:04 -06:00
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
2008-04-30 01:54:42 -06:00
|
|
|
int err = 0;
|
|
|
|
ssize_t res = 0;
|
|
|
|
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
fuse: hotfix truncate_pagecache() issue
The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.
The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:
1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.
The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:
1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.
The result will be the lost of data user wrote on the fourth step.
The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).
Changed in v2:
- improved patch description to cover both sides of the issue.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
2013-08-30 07:06:04 -06:00
|
|
|
if (inode->i_size < pos + iov_iter_count(ii))
|
|
|
|
set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
do {
|
|
|
|
struct fuse_req *req;
|
|
|
|
ssize_t count;
|
2012-10-26 09:49:00 -06:00
|
|
|
unsigned nr_pages = fuse_wr_pages(pos, iov_iter_count(ii));
|
2008-04-30 01:54:42 -06:00
|
|
|
|
2012-10-26 09:49:00 -06:00
|
|
|
req = fuse_get_req(fc, nr_pages);
|
2008-04-30 01:54:42 -06:00
|
|
|
if (IS_ERR(req)) {
|
|
|
|
err = PTR_ERR(req);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
count = fuse_fill_write_pages(req, mapping, ii, pos);
|
|
|
|
if (count <= 0) {
|
|
|
|
err = count;
|
|
|
|
} else {
|
|
|
|
size_t num_written;
|
|
|
|
|
|
|
|
num_written = fuse_send_write_pages(req, file, inode,
|
|
|
|
pos, count);
|
|
|
|
err = req->out.h.error;
|
|
|
|
if (!err) {
|
|
|
|
res += num_written;
|
|
|
|
pos += num_written;
|
|
|
|
|
|
|
|
/* break out of the loop on short write */
|
|
|
|
if (num_written != count)
|
|
|
|
err = -EIO;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
} while (!err && iov_iter_count(ii));
|
|
|
|
|
|
|
|
if (res > 0)
|
|
|
|
fuse_write_update_size(inode, pos);
|
|
|
|
|
fuse: hotfix truncate_pagecache() issue
The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.
The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:
1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.
The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:
1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.
The result will be the lost of data user wrote on the fourth step.
The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).
Changed in v2:
- improved patch description to cover both sides of the issue.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
2013-08-30 07:06:04 -06:00
|
|
|
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
|
2008-04-30 01:54:42 -06:00
|
|
|
fuse_invalidate_attr(inode);
|
|
|
|
|
|
|
|
return res > 0 ? res : err;
|
|
|
|
}
|
|
|
|
|
|
|
|
static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
|
|
|
|
unsigned long nr_segs, loff_t pos)
|
|
|
|
{
|
|
|
|
struct file *file = iocb->ki_filp;
|
|
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
size_t count = 0;
|
2012-02-17 10:46:25 -07:00
|
|
|
size_t ocount = 0;
|
2008-04-30 01:54:42 -06:00
|
|
|
ssize_t written = 0;
|
2012-02-17 10:46:25 -07:00
|
|
|
ssize_t written_buffered = 0;
|
2008-04-30 01:54:42 -06:00
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
ssize_t err;
|
|
|
|
struct iov_iter i;
|
2012-02-17 10:46:25 -07:00
|
|
|
loff_t endbyte = 0;
|
2008-04-30 01:54:42 -06:00
|
|
|
|
2013-10-10 07:12:18 -06:00
|
|
|
if (get_fuse_conn(inode)->writeback_cache) {
|
|
|
|
/* Update size (EOF optimization) and mode (SUID clearing) */
|
|
|
|
err = fuse_update_attributes(mapping->host, NULL, file, NULL);
|
|
|
|
if (err)
|
|
|
|
return err;
|
|
|
|
|
|
|
|
return generic_file_aio_write(iocb, iov, nr_segs, pos);
|
|
|
|
}
|
|
|
|
|
2008-04-30 01:54:42 -06:00
|
|
|
WARN_ON(iocb->ki_pos != pos);
|
|
|
|
|
2014-03-04 13:24:06 -07:00
|
|
|
count = ocount = iov_length(iov, nr_segs);
|
2008-04-30 01:54:42 -06:00
|
|
|
mutex_lock(&inode->i_mutex);
|
|
|
|
|
|
|
|
/* We can write back this queue in page reclaim */
|
|
|
|
current->backing_dev_info = mapping->backing_dev_info;
|
|
|
|
|
|
|
|
err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
|
|
|
|
if (err)
|
|
|
|
goto out;
|
2014-03-05 17:28:09 -07:00
|
|
|
iov_iter_init(&i, WRITE, iov, nr_segs, count);
|
2008-04-30 01:54:42 -06:00
|
|
|
|
|
|
|
if (count == 0)
|
|
|
|
goto out;
|
|
|
|
|
2008-06-24 08:50:14 -06:00
|
|
|
err = file_remove_suid(file);
|
2008-04-30 01:54:42 -06:00
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
2012-03-26 07:59:21 -06:00
|
|
|
err = file_update_time(file);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
2008-04-30 01:54:42 -06:00
|
|
|
|
2012-02-17 10:46:25 -07:00
|
|
|
if (file->f_flags & O_DIRECT) {
|
2014-03-03 20:03:20 -07:00
|
|
|
written = generic_file_direct_write(iocb, &i, pos, count, ocount);
|
2012-02-17 10:46:25 -07:00
|
|
|
if (written < 0 || written == count)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
pos += written;
|
2008-04-30 01:54:42 -06:00
|
|
|
|
2012-02-17 10:46:25 -07:00
|
|
|
written_buffered = fuse_perform_write(file, mapping, &i, pos);
|
|
|
|
if (written_buffered < 0) {
|
|
|
|
err = written_buffered;
|
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
endbyte = pos + written_buffered - 1;
|
|
|
|
|
|
|
|
err = filemap_write_and_wait_range(file->f_mapping, pos,
|
|
|
|
endbyte);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
invalidate_mapping_pages(file->f_mapping,
|
|
|
|
pos >> PAGE_CACHE_SHIFT,
|
|
|
|
endbyte >> PAGE_CACHE_SHIFT);
|
|
|
|
|
|
|
|
written += written_buffered;
|
|
|
|
iocb->ki_pos = pos + written_buffered;
|
|
|
|
} else {
|
|
|
|
written = fuse_perform_write(file, mapping, &i, pos);
|
|
|
|
if (written >= 0)
|
|
|
|
iocb->ki_pos = pos + written;
|
|
|
|
}
|
2008-04-30 01:54:42 -06:00
|
|
|
out:
|
|
|
|
current->backing_dev_info = NULL;
|
|
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
|
|
|
|
return written ? written : err;
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:50:29 -06:00
|
|
|
static inline void fuse_page_descs_length_init(struct fuse_req *req,
|
|
|
|
unsigned index, unsigned nr_pages)
|
2012-10-26 09:49:33 -06:00
|
|
|
{
|
|
|
|
int i;
|
|
|
|
|
2012-10-26 09:50:29 -06:00
|
|
|
for (i = index; i < index + nr_pages; i++)
|
2012-10-26 09:49:33 -06:00
|
|
|
req->page_descs[i].length = PAGE_SIZE -
|
|
|
|
req->page_descs[i].offset;
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:50:29 -06:00
|
|
|
static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)
|
|
|
|
{
|
|
|
|
return (unsigned long)ii->iov->iov_base + ii->iov_offset;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline size_t fuse_get_frag_size(const struct iov_iter *ii,
|
|
|
|
size_t max_size)
|
|
|
|
{
|
|
|
|
return min(iov_iter_single_seg_count(ii), max_size);
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:50:15 -06:00
|
|
|
static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
|
2009-04-09 09:37:52 -06:00
|
|
|
size_t *nbytesp, int write)
|
2005-09-09 14:10:35 -06:00
|
|
|
{
|
2012-10-26 09:50:29 -06:00
|
|
|
size_t nbytes = 0; /* # bytes already packed in req */
|
2012-10-26 09:50:15 -06:00
|
|
|
|
2009-04-02 06:25:34 -06:00
|
|
|
/* Special case for kernel I/O: can copy directly into the buffer */
|
2014-03-16 14:08:30 -06:00
|
|
|
if (ii->type & REQ_KERNEL) {
|
2012-10-26 09:50:29 -06:00
|
|
|
unsigned long user_addr = fuse_get_user_addr(ii);
|
|
|
|
size_t frag_size = fuse_get_frag_size(ii, *nbytesp);
|
|
|
|
|
2009-04-02 06:25:34 -06:00
|
|
|
if (write)
|
|
|
|
req->in.args[1].value = (void *) user_addr;
|
|
|
|
else
|
|
|
|
req->out.args[0].value = (void *) user_addr;
|
|
|
|
|
2012-10-26 09:50:15 -06:00
|
|
|
iov_iter_advance(ii, frag_size);
|
|
|
|
*nbytesp = frag_size;
|
2009-04-02 06:25:34 -06:00
|
|
|
return 0;
|
|
|
|
}
|
2005-09-09 14:10:35 -06:00
|
|
|
|
2012-10-26 09:50:36 -06:00
|
|
|
while (nbytes < *nbytesp && req->num_pages < req->max_pages) {
|
2012-10-26 09:50:29 -06:00
|
|
|
unsigned npages;
|
2014-03-18 23:16:16 -06:00
|
|
|
size_t start;
|
2012-10-26 09:50:36 -06:00
|
|
|
unsigned n = req->max_pages - req->num_pages;
|
2014-03-16 14:08:30 -06:00
|
|
|
ssize_t ret = iov_iter_get_pages(ii,
|
|
|
|
&req->pages[req->num_pages],
|
|
|
|
n * PAGE_SIZE, &start);
|
2012-10-26 09:50:29 -06:00
|
|
|
if (ret < 0)
|
|
|
|
return ret;
|
|
|
|
|
2014-03-16 14:08:30 -06:00
|
|
|
iov_iter_advance(ii, ret);
|
|
|
|
nbytes += ret;
|
2012-10-26 09:50:29 -06:00
|
|
|
|
2014-03-16 14:08:30 -06:00
|
|
|
ret += start;
|
|
|
|
npages = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
|
|
|
|
|
|
|
|
req->page_descs[req->num_pages].offset = start;
|
2012-10-26 09:50:29 -06:00
|
|
|
fuse_page_descs_length_init(req, req->num_pages, npages);
|
|
|
|
|
|
|
|
req->num_pages += npages;
|
|
|
|
req->page_descs[req->num_pages - 1].length -=
|
2014-03-16 14:08:30 -06:00
|
|
|
(PAGE_SIZE - ret) & (PAGE_SIZE - 1);
|
2012-10-26 09:50:29 -06:00
|
|
|
}
|
2009-04-02 06:25:34 -06:00
|
|
|
|
|
|
|
if (write)
|
|
|
|
req->in.argpages = 1;
|
|
|
|
else
|
|
|
|
req->out.argpages = 1;
|
|
|
|
|
2012-10-26 09:50:29 -06:00
|
|
|
*nbytesp = nbytes;
|
2009-04-02 06:25:34 -06:00
|
|
|
|
2005-09-09 14:10:35 -06:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:50:36 -06:00
|
|
|
static inline int fuse_iter_npages(const struct iov_iter *ii_p)
|
|
|
|
{
|
2014-03-18 23:16:16 -06:00
|
|
|
return iov_iter_npages(ii_p, FUSE_MAX_PAGES_PER_REQ);
|
2012-10-26 09:50:36 -06:00
|
|
|
}
|
|
|
|
|
2014-03-16 13:50:47 -06:00
|
|
|
ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
|
|
|
|
loff_t *ppos, int flags)
|
2005-09-09 14:10:35 -06:00
|
|
|
{
|
2013-10-10 07:12:05 -06:00
|
|
|
int write = flags & FUSE_DIO_WRITE;
|
|
|
|
int cuse = flags & FUSE_DIO_CUSE;
|
2012-12-14 08:20:51 -07:00
|
|
|
struct file *file = io->file;
|
2013-10-10 07:12:05 -06:00
|
|
|
struct inode *inode = file->f_mapping->host;
|
2009-04-28 08:56:37 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_conn *fc = ff->fc;
|
2005-09-09 14:10:35 -06:00
|
|
|
size_t nmax = write ? fc->max_write : fc->max_read;
|
|
|
|
loff_t pos = *ppos;
|
2014-03-16 13:50:47 -06:00
|
|
|
size_t count = iov_iter_count(iter);
|
2013-10-10 07:12:05 -06:00
|
|
|
pgoff_t idx_from = pos >> PAGE_CACHE_SHIFT;
|
|
|
|
pgoff_t idx_to = (pos + count - 1) >> PAGE_CACHE_SHIFT;
|
2005-09-09 14:10:35 -06:00
|
|
|
ssize_t res = 0;
|
2006-01-06 01:19:39 -07:00
|
|
|
struct fuse_req *req;
|
|
|
|
|
2013-05-14 09:25:39 -06:00
|
|
|
if (io->async)
|
2014-03-16 13:50:47 -06:00
|
|
|
req = fuse_get_req_for_background(fc, fuse_iter_npages(iter));
|
2013-05-14 09:25:39 -06:00
|
|
|
else
|
2014-03-16 13:50:47 -06:00
|
|
|
req = fuse_get_req(fc, fuse_iter_npages(iter));
|
2006-04-10 23:54:58 -06:00
|
|
|
if (IS_ERR(req))
|
|
|
|
return PTR_ERR(req);
|
2005-09-09 14:10:35 -06:00
|
|
|
|
2013-10-10 07:12:05 -06:00
|
|
|
if (!cuse && fuse_range_is_writeback(inode, idx_from, idx_to)) {
|
|
|
|
if (!write)
|
|
|
|
mutex_lock(&inode->i_mutex);
|
|
|
|
fuse_sync_writes(inode);
|
|
|
|
if (!write)
|
|
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
}
|
|
|
|
|
2005-09-09 14:10:35 -06:00
|
|
|
while (count) {
|
|
|
|
size_t nres;
|
2009-04-28 08:56:37 -06:00
|
|
|
fl_owner_t owner = current->files;
|
2009-04-02 06:25:34 -06:00
|
|
|
size_t nbytes = min(count, nmax);
|
2014-03-16 13:50:47 -06:00
|
|
|
int err = fuse_get_user_pages(req, iter, &nbytes, write);
|
2005-09-09 14:10:35 -06:00
|
|
|
if (err) {
|
|
|
|
res = err;
|
|
|
|
break;
|
|
|
|
}
|
2009-04-02 06:25:34 -06:00
|
|
|
|
2005-09-09 14:10:35 -06:00
|
|
|
if (write)
|
2012-12-14 08:20:51 -07:00
|
|
|
nres = fuse_send_write(req, io, pos, nbytes, owner);
|
2005-09-09 14:10:35 -06:00
|
|
|
else
|
2012-12-14 08:20:51 -07:00
|
|
|
nres = fuse_send_read(req, io, pos, nbytes, owner);
|
2009-04-28 08:56:37 -06:00
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
if (!io->async)
|
|
|
|
fuse_release_user_pages(req, !write);
|
2005-09-09 14:10:35 -06:00
|
|
|
if (req->out.h.error) {
|
|
|
|
if (!res)
|
|
|
|
res = req->out.h.error;
|
|
|
|
break;
|
|
|
|
} else if (nres > nbytes) {
|
|
|
|
res = -EIO;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
count -= nres;
|
|
|
|
res += nres;
|
|
|
|
pos += nres;
|
|
|
|
if (nres != nbytes)
|
|
|
|
break;
|
2006-04-11 13:16:51 -06:00
|
|
|
if (count) {
|
|
|
|
fuse_put_request(fc, req);
|
2013-05-14 09:25:39 -06:00
|
|
|
if (io->async)
|
|
|
|
req = fuse_get_req_for_background(fc,
|
2014-03-16 13:50:47 -06:00
|
|
|
fuse_iter_npages(iter));
|
2013-05-14 09:25:39 -06:00
|
|
|
else
|
2014-03-16 13:50:47 -06:00
|
|
|
req = fuse_get_req(fc, fuse_iter_npages(iter));
|
2006-04-11 13:16:51 -06:00
|
|
|
if (IS_ERR(req))
|
|
|
|
break;
|
|
|
|
}
|
2005-09-09 14:10:35 -06:00
|
|
|
}
|
2009-10-22 07:24:52 -06:00
|
|
|
if (!IS_ERR(req))
|
|
|
|
fuse_put_request(fc, req);
|
2009-04-28 08:56:36 -06:00
|
|
|
if (res > 0)
|
2005-09-09 14:10:35 -06:00
|
|
|
*ppos = pos;
|
|
|
|
|
|
|
|
return res;
|
|
|
|
}
|
2009-04-13 19:54:53 -06:00
|
|
|
EXPORT_SYMBOL_GPL(fuse_direct_io);
|
2005-09-09 14:10:35 -06:00
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
static ssize_t __fuse_direct_read(struct fuse_io_priv *io,
|
2014-03-16 13:50:47 -06:00
|
|
|
struct iov_iter *iter,
|
|
|
|
loff_t *ppos)
|
2005-09-09 14:10:35 -06:00
|
|
|
{
|
2009-04-28 08:56:36 -06:00
|
|
|
ssize_t res;
|
2012-12-14 08:20:51 -07:00
|
|
|
struct file *file = io->file;
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2009-04-28 08:56:36 -06:00
|
|
|
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
2014-03-16 13:50:47 -06:00
|
|
|
res = fuse_direct_io(io, iter, ppos, 0);
|
2009-04-28 08:56:36 -06:00
|
|
|
|
|
|
|
fuse_invalidate_attr(inode);
|
|
|
|
|
|
|
|
return res;
|
2005-09-09 14:10:35 -06:00
|
|
|
}
|
|
|
|
|
2012-10-26 09:50:15 -06:00
|
|
|
static ssize_t fuse_direct_read(struct file *file, char __user *buf,
|
|
|
|
size_t count, loff_t *ppos)
|
|
|
|
{
|
2012-12-14 08:20:51 -07:00
|
|
|
struct fuse_io_priv io = { .async = 0, .file = file };
|
2012-11-10 08:55:56 -07:00
|
|
|
struct iovec iov = { .iov_base = buf, .iov_len = count };
|
2014-03-16 13:50:47 -06:00
|
|
|
struct iov_iter ii;
|
|
|
|
iov_iter_init(&ii, READ, &iov, 1, count);
|
|
|
|
return __fuse_direct_read(&io, &ii, ppos);
|
2012-10-26 09:50:15 -06:00
|
|
|
}
|
|
|
|
|
2012-12-14 08:20:51 -07:00
|
|
|
static ssize_t __fuse_direct_write(struct fuse_io_priv *io,
|
2014-03-16 13:50:47 -06:00
|
|
|
struct iov_iter *iter,
|
|
|
|
loff_t *ppos)
|
2005-09-09 14:10:35 -06:00
|
|
|
{
|
2012-12-14 08:20:51 -07:00
|
|
|
struct file *file = io->file;
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2014-03-16 13:50:47 -06:00
|
|
|
size_t count = iov_iter_count(iter);
|
2005-09-09 14:10:35 -06:00
|
|
|
ssize_t res;
|
2009-04-28 08:56:36 -06:00
|
|
|
|
2014-03-16 13:50:47 -06:00
|
|
|
|
2007-05-23 14:57:54 -06:00
|
|
|
res = generic_write_checks(file, ppos, &count, 0);
|
2014-03-16 13:50:47 -06:00
|
|
|
if (!res) {
|
|
|
|
if (iter->count > count)
|
|
|
|
iter->count = count;
|
|
|
|
res = fuse_direct_io(io, iter, ppos, FUSE_DIO_WRITE);
|
|
|
|
}
|
2009-04-28 08:56:36 -06:00
|
|
|
|
|
|
|
fuse_invalidate_attr(inode);
|
|
|
|
|
2005-09-09 14:10:35 -06:00
|
|
|
return res;
|
|
|
|
}
|
|
|
|
|
2012-02-17 10:46:25 -07:00
|
|
|
static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
|
|
|
|
size_t count, loff_t *ppos)
|
|
|
|
{
|
2012-11-10 08:55:56 -07:00
|
|
|
struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count };
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2012-02-17 10:46:25 -07:00
|
|
|
ssize_t res;
|
2012-12-14 08:20:51 -07:00
|
|
|
struct fuse_io_priv io = { .async = 0, .file = file };
|
2014-03-16 13:50:47 -06:00
|
|
|
struct iov_iter ii;
|
|
|
|
iov_iter_init(&ii, WRITE, &iov, 1, count);
|
2012-02-17 10:46:25 -07:00
|
|
|
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
/* Don't allow parallel writes to the same file */
|
|
|
|
mutex_lock(&inode->i_mutex);
|
2014-03-16 13:50:47 -06:00
|
|
|
res = __fuse_direct_write(&io, &ii, ppos);
|
2012-12-14 08:21:08 -07:00
|
|
|
if (res > 0)
|
|
|
|
fuse_write_update_size(inode, *ppos);
|
2012-02-17 10:46:25 -07:00
|
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
|
|
|
|
return res;
|
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
2013-06-29 11:42:48 -06:00
|
|
|
int i;
|
|
|
|
|
|
|
|
for (i = 0; i < req->num_pages; i++)
|
|
|
|
__free_page(req->pages[i]);
|
2013-10-01 08:44:53 -06:00
|
|
|
|
|
|
|
if (req->ff)
|
|
|
|
fuse_file_put(req->ff, false);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
|
|
|
|
{
|
|
|
|
struct inode *inode = req->inode;
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info;
|
2013-06-29 11:42:48 -06:00
|
|
|
int i;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
list_del(&req->writepages_entry);
|
2013-06-29 11:42:48 -06:00
|
|
|
for (i = 0; i < req->num_pages; i++) {
|
|
|
|
dec_bdi_stat(bdi, BDI_WRITEBACK);
|
|
|
|
dec_zone_page_state(req->pages[i], NR_WRITEBACK_TEMP);
|
|
|
|
bdi_writeout_inc(bdi);
|
|
|
|
}
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
wake_up(&fi->page_waitq);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Called under fc->lock, may release and reacquire it */
|
2013-10-02 11:38:32 -06:00
|
|
|
static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req,
|
|
|
|
loff_t size)
|
2010-09-07 05:42:41 -06:00
|
|
|
__releases(fc->lock)
|
|
|
|
__acquires(fc->lock)
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
{
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(req->inode);
|
|
|
|
struct fuse_write_in *inarg = &req->misc.write.in;
|
2013-06-29 11:42:48 -06:00
|
|
|
__u64 data_size = req->num_pages * PAGE_CACHE_SIZE;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
if (!fc->connected)
|
|
|
|
goto out_free;
|
|
|
|
|
2013-06-29 11:42:48 -06:00
|
|
|
if (inarg->offset + data_size <= size) {
|
|
|
|
inarg->size = data_size;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
} else if (inarg->offset < size) {
|
2013-06-29 11:42:48 -06:00
|
|
|
inarg->size = size - inarg->offset;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
} else {
|
|
|
|
/* Got truncated off completely */
|
|
|
|
goto out_free;
|
2005-09-09 14:10:30 -06:00
|
|
|
}
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
req->in.args[1].size = inarg->size;
|
|
|
|
fi->writectr++;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send_background_locked(fc, req);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
return;
|
|
|
|
|
|
|
|
out_free:
|
|
|
|
fuse_writepage_finish(fc, req);
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
fuse_writepage_free(fc, req);
|
2008-11-26 04:03:54 -07:00
|
|
|
fuse_put_request(fc, req);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
spin_lock(&fc->lock);
|
2005-09-09 14:10:30 -06:00
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
/*
|
|
|
|
* If fi->writectr is positive (no truncate or fsync going on) send
|
|
|
|
* all queued writepage requests.
|
|
|
|
*
|
|
|
|
* Called with fc->lock
|
|
|
|
*/
|
|
|
|
void fuse_flush_writepages(struct inode *inode)
|
2010-09-07 05:42:41 -06:00
|
|
|
__releases(fc->lock)
|
|
|
|
__acquires(fc->lock)
|
2005-09-09 14:10:30 -06:00
|
|
|
{
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
2013-10-02 11:38:32 -06:00
|
|
|
size_t crop = i_size_read(inode);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
struct fuse_req *req;
|
|
|
|
|
|
|
|
while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {
|
|
|
|
req = list_entry(fi->queued_writes.next, struct fuse_req, list);
|
|
|
|
list_del_init(&req->list);
|
2013-10-02 11:38:32 -06:00
|
|
|
fuse_send_writepage(fc, req, crop);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
|
|
|
|
{
|
|
|
|
struct inode *inode = req->inode;
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
|
|
|
|
mapping_set_error(inode->i_mapping, req->out.h.error);
|
|
|
|
spin_lock(&fc->lock);
|
2013-10-01 08:44:53 -06:00
|
|
|
while (req->misc.write.next) {
|
2013-10-02 11:38:32 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_write_in *inarg = &req->misc.write.in;
|
2013-10-01 08:44:53 -06:00
|
|
|
struct fuse_req *next = req->misc.write.next;
|
|
|
|
req->misc.write.next = next->misc.write.next;
|
|
|
|
next->misc.write.next = NULL;
|
2013-10-02 11:38:54 -06:00
|
|
|
next->ff = fuse_file_get(req->ff);
|
2013-10-01 08:44:53 -06:00
|
|
|
list_add(&next->writepages_entry, &fi->writepages);
|
2013-10-02 11:38:32 -06:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Skip fuse_flush_writepages() to make it easy to crop requests
|
|
|
|
* based on primary request size.
|
|
|
|
*
|
|
|
|
* 1st case (trivial): there are no concurrent activities using
|
|
|
|
* fuse_set/release_nowrite. Then we're on safe side because
|
|
|
|
* fuse_flush_writepages() would call fuse_send_writepage()
|
|
|
|
* anyway.
|
|
|
|
*
|
|
|
|
* 2nd case: someone called fuse_set_nowrite and it is waiting
|
|
|
|
* now for completion of all in-flight requests. This happens
|
|
|
|
* rarely and no more than once per page, so this should be
|
|
|
|
* okay.
|
|
|
|
*
|
|
|
|
* 3rd case: someone (e.g. fuse_do_setattr()) is in the middle
|
|
|
|
* of fuse_set_nowrite..fuse_release_nowrite section. The fact
|
|
|
|
* that fuse_set_nowrite returned implies that all in-flight
|
|
|
|
* requests were completed along with all of their secondary
|
|
|
|
* requests. Further primary requests are blocked by negative
|
|
|
|
* writectr. Hence there cannot be any in-flight requests and
|
|
|
|
* no invocations of fuse_writepage_end() while we're in
|
|
|
|
* fuse_set_nowrite..fuse_release_nowrite section.
|
|
|
|
*/
|
|
|
|
fuse_send_writepage(fc, next, inarg->offset + inarg->size);
|
2013-10-01 08:44:53 -06:00
|
|
|
}
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
fi->writectr--;
|
|
|
|
fuse_writepage_finish(fc, req);
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
fuse_writepage_free(fc, req);
|
|
|
|
}
|
|
|
|
|
2014-04-28 06:19:23 -06:00
|
|
|
static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
|
|
|
|
struct fuse_inode *fi)
|
2013-06-29 11:42:20 -06:00
|
|
|
{
|
2013-10-01 08:44:52 -06:00
|
|
|
struct fuse_file *ff = NULL;
|
2013-06-29 11:42:20 -06:00
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
2014-04-28 06:19:23 -06:00
|
|
|
if (!list_empty(&fi->write_files)) {
|
2013-10-01 08:44:52 -06:00
|
|
|
ff = list_entry(fi->write_files.next, struct fuse_file,
|
|
|
|
write_entry);
|
|
|
|
fuse_file_get(ff);
|
|
|
|
}
|
2013-06-29 11:42:20 -06:00
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
|
|
|
return ff;
|
|
|
|
}
|
|
|
|
|
2014-04-28 06:19:23 -06:00
|
|
|
static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
|
|
|
|
struct fuse_inode *fi)
|
|
|
|
{
|
|
|
|
struct fuse_file *ff = __fuse_write_file_get(fc, fi);
|
|
|
|
WARN_ON(!ff);
|
|
|
|
return ff;
|
|
|
|
}
|
|
|
|
|
|
|
|
int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
|
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
struct fuse_file *ff;
|
|
|
|
int err;
|
|
|
|
|
|
|
|
ff = __fuse_write_file_get(fc, fi);
|
2014-04-28 06:19:24 -06:00
|
|
|
err = fuse_flush_times(inode, ff);
|
2014-04-28 06:19:23 -06:00
|
|
|
if (ff)
|
|
|
|
fuse_file_put(ff, 0);
|
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
static int fuse_writepage_locked(struct page *page)
|
|
|
|
{
|
|
|
|
struct address_space *mapping = page->mapping;
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct page *tmp_page;
|
2013-10-01 08:44:52 -06:00
|
|
|
int error = -ENOMEM;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
set_page_writeback(page);
|
|
|
|
|
2012-10-26 09:48:07 -06:00
|
|
|
req = fuse_request_alloc_nofs(1);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
if (!req)
|
|
|
|
goto err;
|
|
|
|
|
2013-03-21 08:02:04 -06:00
|
|
|
req->background = 1; /* writeback always goes to bg_queue */
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
|
|
|
|
if (!tmp_page)
|
|
|
|
goto err_free;
|
|
|
|
|
2013-10-01 08:44:52 -06:00
|
|
|
error = -EIO;
|
2013-06-29 11:45:29 -06:00
|
|
|
req->ff = fuse_write_file_get(fc, fi);
|
2013-10-01 08:44:52 -06:00
|
|
|
if (!req->ff)
|
|
|
|
goto err_free;
|
|
|
|
|
2013-06-29 11:42:20 -06:00
|
|
|
fuse_write_fill(req, req->ff, page_offset(page), 0);
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
copy_highpage(tmp_page, page);
|
2009-04-28 08:56:36 -06:00
|
|
|
req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
|
2013-10-01 08:44:53 -06:00
|
|
|
req->misc.write.next = NULL;
|
2009-04-02 06:25:34 -06:00
|
|
|
req->in.argpages = 1;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
req->num_pages = 1;
|
|
|
|
req->pages[0] = tmp_page;
|
2012-10-26 09:49:24 -06:00
|
|
|
req->page_descs[0].offset = 0;
|
2012-10-26 09:49:33 -06:00
|
|
|
req->page_descs[0].length = PAGE_SIZE;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
req->end = fuse_writepage_end;
|
|
|
|
req->inode = inode;
|
|
|
|
|
|
|
|
inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK);
|
|
|
|
inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
list_add(&req->writepages_entry, &fi->writepages);
|
|
|
|
list_add_tail(&req->list, &fi->queued_writes);
|
|
|
|
fuse_flush_writepages(inode);
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
2013-08-12 10:39:30 -06:00
|
|
|
end_page_writeback(page);
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
return 0;
|
|
|
|
|
|
|
|
err_free:
|
|
|
|
fuse_request_free(req);
|
|
|
|
err:
|
|
|
|
end_page_writeback(page);
|
2013-10-01 08:44:52 -06:00
|
|
|
return error;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_writepage(struct page *page, struct writeback_control *wbc)
|
|
|
|
{
|
|
|
|
int err;
|
|
|
|
|
2013-10-01 08:44:53 -06:00
|
|
|
if (fuse_page_is_writeback(page->mapping->host, page->index)) {
|
|
|
|
/*
|
|
|
|
* ->writepages() should be called for sync() and friends. We
|
|
|
|
* should only get here on direct reclaim and then we are
|
|
|
|
* allowed to skip a page which is already in flight
|
|
|
|
*/
|
|
|
|
WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
|
|
|
|
|
|
|
|
redirty_page_for_writepage(wbc, page);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
err = fuse_writepage_locked(page);
|
|
|
|
unlock_page(page);
|
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2013-06-29 11:45:29 -06:00
|
|
|
struct fuse_fill_wb_data {
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_file *ff;
|
|
|
|
struct inode *inode;
|
2013-08-16 05:51:41 -06:00
|
|
|
struct page **orig_pages;
|
2013-06-29 11:45:29 -06:00
|
|
|
};
|
|
|
|
|
|
|
|
static void fuse_writepages_send(struct fuse_fill_wb_data *data)
|
|
|
|
{
|
|
|
|
struct fuse_req *req = data->req;
|
|
|
|
struct inode *inode = data->inode;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
2013-08-16 05:51:41 -06:00
|
|
|
int num_pages = req->num_pages;
|
|
|
|
int i;
|
2013-06-29 11:45:29 -06:00
|
|
|
|
|
|
|
req->ff = fuse_file_get(data->ff);
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
list_add_tail(&req->list, &fi->queued_writes);
|
|
|
|
fuse_flush_writepages(inode);
|
|
|
|
spin_unlock(&fc->lock);
|
2013-08-16 05:51:41 -06:00
|
|
|
|
|
|
|
for (i = 0; i < num_pages; i++)
|
|
|
|
end_page_writeback(data->orig_pages[i]);
|
2013-06-29 11:45:29 -06:00
|
|
|
}
|
|
|
|
|
2013-10-01 08:44:53 -06:00
|
|
|
static bool fuse_writepage_in_flight(struct fuse_req *new_req,
|
|
|
|
struct page *page)
|
|
|
|
{
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(new_req->inode);
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(new_req->inode);
|
|
|
|
struct fuse_req *tmp;
|
|
|
|
struct fuse_req *old_req;
|
|
|
|
bool found = false;
|
|
|
|
pgoff_t curr_index;
|
|
|
|
|
|
|
|
BUG_ON(new_req->num_pages != 0);
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
list_del(&new_req->writepages_entry);
|
|
|
|
list_for_each_entry(old_req, &fi->writepages, writepages_entry) {
|
|
|
|
BUG_ON(old_req->inode != new_req->inode);
|
|
|
|
curr_index = old_req->misc.write.in.offset >> PAGE_CACHE_SHIFT;
|
|
|
|
if (curr_index <= page->index &&
|
|
|
|
page->index < curr_index + old_req->num_pages) {
|
|
|
|
found = true;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
2013-10-02 05:01:07 -06:00
|
|
|
if (!found) {
|
|
|
|
list_add(&new_req->writepages_entry, &fi->writepages);
|
2013-10-01 08:44:53 -06:00
|
|
|
goto out_unlock;
|
2013-10-02 05:01:07 -06:00
|
|
|
}
|
2013-10-01 08:44:53 -06:00
|
|
|
|
2013-10-02 05:01:07 -06:00
|
|
|
new_req->num_pages = 1;
|
2013-10-01 08:44:53 -06:00
|
|
|
for (tmp = old_req; tmp != NULL; tmp = tmp->misc.write.next) {
|
|
|
|
BUG_ON(tmp->inode != new_req->inode);
|
|
|
|
curr_index = tmp->misc.write.in.offset >> PAGE_CACHE_SHIFT;
|
|
|
|
if (tmp->num_pages == 1 &&
|
|
|
|
curr_index == page->index) {
|
|
|
|
old_req = tmp;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
if (old_req->num_pages == 1 && (old_req->state == FUSE_REQ_INIT ||
|
|
|
|
old_req->state == FUSE_REQ_PENDING)) {
|
2013-10-02 11:38:43 -06:00
|
|
|
struct backing_dev_info *bdi = page->mapping->backing_dev_info;
|
|
|
|
|
2013-10-01 08:44:53 -06:00
|
|
|
copy_highpage(old_req->pages[0], page);
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
2013-10-02 11:38:43 -06:00
|
|
|
dec_bdi_stat(bdi, BDI_WRITEBACK);
|
2013-10-01 08:44:53 -06:00
|
|
|
dec_zone_page_state(page, NR_WRITEBACK_TEMP);
|
2013-10-02 11:38:43 -06:00
|
|
|
bdi_writeout_inc(bdi);
|
2013-10-01 08:44:53 -06:00
|
|
|
fuse_writepage_free(fc, new_req);
|
|
|
|
fuse_request_free(new_req);
|
|
|
|
goto out;
|
|
|
|
} else {
|
|
|
|
new_req->misc.write.next = old_req->misc.write.next;
|
|
|
|
old_req->misc.write.next = new_req;
|
|
|
|
}
|
|
|
|
out_unlock:
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
out:
|
|
|
|
return found;
|
|
|
|
}
|
|
|
|
|
2013-06-29 11:45:29 -06:00
|
|
|
static int fuse_writepages_fill(struct page *page,
|
|
|
|
struct writeback_control *wbc, void *_data)
|
|
|
|
{
|
|
|
|
struct fuse_fill_wb_data *data = _data;
|
|
|
|
struct fuse_req *req = data->req;
|
|
|
|
struct inode *inode = data->inode;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct page *tmp_page;
|
2013-10-01 08:44:53 -06:00
|
|
|
bool is_writeback;
|
2013-06-29 11:45:29 -06:00
|
|
|
int err;
|
|
|
|
|
|
|
|
if (!data->ff) {
|
|
|
|
err = -EIO;
|
|
|
|
data->ff = fuse_write_file_get(fc, get_fuse_inode(inode));
|
|
|
|
if (!data->ff)
|
|
|
|
goto out_unlock;
|
|
|
|
}
|
|
|
|
|
2013-10-01 08:44:53 -06:00
|
|
|
/*
|
|
|
|
* Being under writeback is unlikely but possible. For example direct
|
|
|
|
* read to an mmaped fuse file will set the page dirty twice; once when
|
|
|
|
* the pages are faulted with get_user_pages(), and then after the read
|
|
|
|
* completed.
|
|
|
|
*/
|
|
|
|
is_writeback = fuse_page_is_writeback(inode, page->index);
|
|
|
|
|
|
|
|
if (req && req->num_pages &&
|
|
|
|
(is_writeback || req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
|
|
|
|
(req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_write ||
|
|
|
|
data->orig_pages[req->num_pages - 1]->index + 1 != page->index)) {
|
|
|
|
fuse_writepages_send(data);
|
|
|
|
data->req = NULL;
|
2013-06-29 11:45:29 -06:00
|
|
|
}
|
|
|
|
err = -ENOMEM;
|
|
|
|
tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
|
|
|
|
if (!tmp_page)
|
|
|
|
goto out_unlock;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* The page must not be redirtied until the writeout is completed
|
|
|
|
* (i.e. userspace has sent a reply to the write request). Otherwise
|
|
|
|
* there could be more than one temporary page instance for each real
|
|
|
|
* page.
|
|
|
|
*
|
|
|
|
* This is ensured by holding the page lock in page_mkwrite() while
|
|
|
|
* checking fuse_page_is_writeback(). We already hold the page lock
|
|
|
|
* since clear_page_dirty_for_io() and keep it held until we add the
|
|
|
|
* request to the fi->writepages list and increment req->num_pages.
|
|
|
|
* After this fuse_page_is_writeback() will indicate that the page is
|
|
|
|
* under writeback, so we can release the page lock.
|
|
|
|
*/
|
|
|
|
if (data->req == NULL) {
|
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
|
|
|
|
|
|
|
err = -ENOMEM;
|
|
|
|
req = fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ);
|
|
|
|
if (!req) {
|
|
|
|
__free_page(tmp_page);
|
|
|
|
goto out_unlock;
|
|
|
|
}
|
|
|
|
|
|
|
|
fuse_write_fill(req, data->ff, page_offset(page), 0);
|
|
|
|
req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
|
2013-10-01 08:44:53 -06:00
|
|
|
req->misc.write.next = NULL;
|
2013-06-29 11:45:29 -06:00
|
|
|
req->in.argpages = 1;
|
|
|
|
req->background = 1;
|
|
|
|
req->num_pages = 0;
|
|
|
|
req->end = fuse_writepage_end;
|
|
|
|
req->inode = inode;
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
list_add(&req->writepages_entry, &fi->writepages);
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
|
|
|
data->req = req;
|
|
|
|
}
|
|
|
|
set_page_writeback(page);
|
|
|
|
|
|
|
|
copy_highpage(tmp_page, page);
|
|
|
|
req->pages[req->num_pages] = tmp_page;
|
|
|
|
req->page_descs[req->num_pages].offset = 0;
|
|
|
|
req->page_descs[req->num_pages].length = PAGE_SIZE;
|
|
|
|
|
|
|
|
inc_bdi_stat(page->mapping->backing_dev_info, BDI_WRITEBACK);
|
|
|
|
inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
|
2013-10-01 08:44:53 -06:00
|
|
|
|
|
|
|
err = 0;
|
|
|
|
if (is_writeback && fuse_writepage_in_flight(req, page)) {
|
|
|
|
end_page_writeback(page);
|
|
|
|
data->req = NULL;
|
|
|
|
goto out_unlock;
|
|
|
|
}
|
2013-08-16 05:51:41 -06:00
|
|
|
data->orig_pages[req->num_pages] = page;
|
2013-06-29 11:45:29 -06:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Protected by fc->lock against concurrent access by
|
|
|
|
* fuse_page_is_writeback().
|
|
|
|
*/
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
req->num_pages++;
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
|
|
|
|
out_unlock:
|
|
|
|
unlock_page(page);
|
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_writepages(struct address_space *mapping,
|
|
|
|
struct writeback_control *wbc)
|
|
|
|
{
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
struct fuse_fill_wb_data data;
|
|
|
|
int err;
|
|
|
|
|
|
|
|
err = -EIO;
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
data.inode = inode;
|
|
|
|
data.req = NULL;
|
|
|
|
data.ff = NULL;
|
|
|
|
|
2013-08-16 05:51:41 -06:00
|
|
|
err = -ENOMEM;
|
|
|
|
data.orig_pages = kzalloc(sizeof(struct page *) *
|
|
|
|
FUSE_MAX_PAGES_PER_REQ,
|
|
|
|
GFP_NOFS);
|
|
|
|
if (!data.orig_pages)
|
|
|
|
goto out;
|
|
|
|
|
2013-06-29 11:45:29 -06:00
|
|
|
err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
|
|
|
|
if (data.req) {
|
|
|
|
/* Ignore errors if we can write at least one page */
|
|
|
|
BUG_ON(!data.req->num_pages);
|
|
|
|
fuse_writepages_send(&data);
|
|
|
|
err = 0;
|
|
|
|
}
|
|
|
|
if (data.ff)
|
|
|
|
fuse_file_put(data.ff, false);
|
2013-08-16 05:51:41 -06:00
|
|
|
|
|
|
|
kfree(data.orig_pages);
|
2013-06-29 11:45:29 -06:00
|
|
|
out:
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2013-10-10 07:11:43 -06:00
|
|
|
/*
|
|
|
|
* It's worthy to make sure that space is reserved on disk for the write,
|
|
|
|
* but how to implement it without killing performance need more thinking.
|
|
|
|
*/
|
|
|
|
static int fuse_write_begin(struct file *file, struct address_space *mapping,
|
|
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
|
|
struct page **pagep, void **fsdata)
|
|
|
|
{
|
|
|
|
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(file->f_dentry->d_inode);
|
|
|
|
struct page *page;
|
|
|
|
loff_t fsize;
|
|
|
|
int err = -ENOMEM;
|
|
|
|
|
|
|
|
WARN_ON(!fc->writeback_cache);
|
|
|
|
|
|
|
|
page = grab_cache_page_write_begin(mapping, index, flags);
|
|
|
|
if (!page)
|
|
|
|
goto error;
|
|
|
|
|
|
|
|
fuse_wait_on_page_writeback(mapping->host, page->index);
|
|
|
|
|
|
|
|
if (PageUptodate(page) || len == PAGE_CACHE_SIZE)
|
|
|
|
goto success;
|
|
|
|
/*
|
|
|
|
* Check if the start this page comes after the end of file, in which
|
|
|
|
* case the readpage can be optimized away.
|
|
|
|
*/
|
|
|
|
fsize = i_size_read(mapping->host);
|
|
|
|
if (fsize <= (pos & PAGE_CACHE_MASK)) {
|
|
|
|
size_t off = pos & ~PAGE_CACHE_MASK;
|
|
|
|
if (off)
|
|
|
|
zero_user_segment(page, 0, off);
|
|
|
|
goto success;
|
|
|
|
}
|
|
|
|
err = fuse_do_readpage(file, page);
|
|
|
|
if (err)
|
|
|
|
goto cleanup;
|
|
|
|
success:
|
|
|
|
*pagep = page;
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
cleanup:
|
|
|
|
unlock_page(page);
|
|
|
|
page_cache_release(page);
|
|
|
|
error:
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_write_end(struct file *file, struct address_space *mapping,
|
|
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
|
|
struct page *page, void *fsdata)
|
|
|
|
{
|
|
|
|
struct inode *inode = page->mapping->host;
|
|
|
|
|
|
|
|
if (!PageUptodate(page)) {
|
|
|
|
/* Zero any unwritten bytes at the end of the page */
|
|
|
|
size_t endoff = (pos + copied) & ~PAGE_CACHE_MASK;
|
|
|
|
if (endoff)
|
|
|
|
zero_user_segment(page, endoff, PAGE_CACHE_SIZE);
|
|
|
|
SetPageUptodate(page);
|
|
|
|
}
|
|
|
|
|
|
|
|
fuse_write_update_size(inode, pos + copied);
|
|
|
|
set_page_dirty(page);
|
|
|
|
unlock_page(page);
|
|
|
|
page_cache_release(page);
|
|
|
|
|
|
|
|
return copied;
|
|
|
|
}
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
static int fuse_launder_page(struct page *page)
|
|
|
|
{
|
|
|
|
int err = 0;
|
|
|
|
if (clear_page_dirty_for_io(page)) {
|
|
|
|
struct inode *inode = page->mapping->host;
|
|
|
|
err = fuse_writepage_locked(page);
|
|
|
|
if (!err)
|
|
|
|
fuse_wait_on_page_writeback(inode, page->index);
|
|
|
|
}
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Write back dirty pages now, because there may not be any suitable
|
|
|
|
* open files later
|
|
|
|
*/
|
|
|
|
static void fuse_vma_close(struct vm_area_struct *vma)
|
|
|
|
{
|
|
|
|
filemap_write_and_wait(vma->vm_file->f_mapping);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Wait for writeback against this page to complete before allowing it
|
|
|
|
* to be marked dirty again, and hence written back again, possibly
|
|
|
|
* before the previous writepage completed.
|
|
|
|
*
|
|
|
|
* Block here, instead of in ->writepage(), so that the userspace fs
|
|
|
|
* can only block processes actually operating on the filesystem.
|
|
|
|
*
|
|
|
|
* Otherwise unprivileged userspace fs would be able to block
|
|
|
|
* unrelated:
|
|
|
|
*
|
|
|
|
* - page migration
|
|
|
|
* - sync(2)
|
|
|
|
* - try_to_free_pages() with order > PAGE_ALLOC_COSTLY_ORDER
|
|
|
|
*/
|
2009-03-31 16:23:21 -06:00
|
|
|
static int fuse_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
{
|
2009-03-31 16:23:21 -06:00
|
|
|
struct page *page = vmf->page;
|
2013-10-01 08:44:51 -06:00
|
|
|
struct inode *inode = file_inode(vma->vm_file);
|
|
|
|
|
|
|
|
file_update_time(vma->vm_file);
|
|
|
|
lock_page(page);
|
|
|
|
if (page->mapping != inode->i_mapping) {
|
|
|
|
unlock_page(page);
|
|
|
|
return VM_FAULT_NOPAGE;
|
|
|
|
}
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
|
|
|
|
fuse_wait_on_page_writeback(inode, page->index);
|
2013-10-01 08:44:51 -06:00
|
|
|
return VM_FAULT_LOCKED;
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
}
|
|
|
|
|
2009-09-27 12:29:37 -06:00
|
|
|
static const struct vm_operations_struct fuse_file_vm_ops = {
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
.close = fuse_vma_close,
|
|
|
|
.fault = filemap_fault,
|
2014-04-07 16:37:19 -06:00
|
|
|
.map_pages = filemap_map_pages,
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
.page_mkwrite = fuse_page_mkwrite,
|
2012-10-08 17:28:46 -06:00
|
|
|
.remap_pages = generic_file_remap_pages,
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
};
|
|
|
|
|
|
|
|
static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
|
|
|
|
{
|
2013-10-10 07:10:04 -06:00
|
|
|
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
|
|
|
|
fuse_link_write_file(file);
|
|
|
|
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
file_accessed(file);
|
|
|
|
vma->vm_ops = &fuse_file_vm_ops;
|
2005-09-09 14:10:30 -06:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2009-04-02 06:25:35 -06:00
|
|
|
static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
|
|
|
|
{
|
|
|
|
/* Can't provide the coherency needed for MAP_SHARED */
|
|
|
|
if (vma->vm_flags & VM_MAYSHARE)
|
|
|
|
return -ENODEV;
|
|
|
|
|
2009-04-09 09:37:53 -06:00
|
|
|
invalidate_inode_pages2(file->f_mapping);
|
|
|
|
|
2009-04-02 06:25:35 -06:00
|
|
|
return generic_file_mmap(file, vma);
|
|
|
|
}
|
|
|
|
|
2006-06-25 06:48:52 -06:00
|
|
|
static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
|
|
|
|
struct file_lock *fl)
|
|
|
|
{
|
|
|
|
switch (ffl->type) {
|
|
|
|
case F_UNLCK:
|
|
|
|
break;
|
|
|
|
|
|
|
|
case F_RDLCK:
|
|
|
|
case F_WRLCK:
|
|
|
|
if (ffl->start > OFFSET_MAX || ffl->end > OFFSET_MAX ||
|
|
|
|
ffl->end < ffl->start)
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
fl->fl_start = ffl->start;
|
|
|
|
fl->fl_end = ffl->end;
|
|
|
|
fl->fl_pid = ffl->pid;
|
|
|
|
break;
|
|
|
|
|
|
|
|
default:
|
|
|
|
return -EIO;
|
|
|
|
}
|
|
|
|
fl->fl_type = ffl->type;
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void fuse_lk_fill(struct fuse_req *req, struct file *file,
|
2007-10-18 04:07:02 -06:00
|
|
|
const struct file_lock *fl, int opcode, pid_t pid,
|
|
|
|
int flock)
|
2006-06-25 06:48:52 -06:00
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2006-06-25 06:48:55 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
2006-06-25 06:48:52 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
struct fuse_lk_in *arg = &req->misc.lk_in;
|
|
|
|
|
|
|
|
arg->fh = ff->fh;
|
2006-06-25 06:48:55 -06:00
|
|
|
arg->owner = fuse_lock_owner_id(fc, fl->fl_owner);
|
2006-06-25 06:48:52 -06:00
|
|
|
arg->lk.start = fl->fl_start;
|
|
|
|
arg->lk.end = fl->fl_end;
|
|
|
|
arg->lk.type = fl->fl_type;
|
|
|
|
arg->lk.pid = pid;
|
2007-10-18 04:07:02 -06:00
|
|
|
if (flock)
|
|
|
|
arg->lk_flags |= FUSE_LK_FLOCK;
|
2006-06-25 06:48:52 -06:00
|
|
|
req->in.h.opcode = opcode;
|
|
|
|
req->in.h.nodeid = get_node_id(inode);
|
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(*arg);
|
|
|
|
req->in.args[0].value = arg;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_getlk(struct file *file, struct file_lock *fl)
|
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2006-06-25 06:48:52 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_lk_out outarg;
|
|
|
|
int err;
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2006-06-25 06:48:52 -06:00
|
|
|
if (IS_ERR(req))
|
|
|
|
return PTR_ERR(req);
|
|
|
|
|
2007-10-18 04:07:02 -06:00
|
|
|
fuse_lk_fill(req, file, fl, FUSE_GETLK, 0, 0);
|
2006-06-25 06:48:52 -06:00
|
|
|
req->out.numargs = 1;
|
|
|
|
req->out.args[0].size = sizeof(outarg);
|
|
|
|
req->out.args[0].value = &outarg;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2006-06-25 06:48:52 -06:00
|
|
|
err = req->out.h.error;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
if (!err)
|
|
|
|
err = convert_fuse_file_lock(&outarg.lk, fl);
|
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2007-10-18 04:07:02 -06:00
|
|
|
static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
|
2006-06-25 06:48:52 -06:00
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2006-06-25 06:48:52 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_req *req;
|
|
|
|
int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
|
|
|
|
pid_t pid = fl->fl_type != F_UNLCK ? current->tgid : 0;
|
|
|
|
int err;
|
|
|
|
|
2011-07-20 18:21:59 -06:00
|
|
|
if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
|
2008-07-25 02:49:02 -06:00
|
|
|
/* NLM needs asynchronous locks, which we don't support yet */
|
|
|
|
return -ENOLCK;
|
|
|
|
}
|
|
|
|
|
2006-06-25 06:48:52 -06:00
|
|
|
/* Unlock on close is handled by the flush method */
|
|
|
|
if (fl->fl_flags & FL_CLOSE)
|
|
|
|
return 0;
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2006-06-25 06:48:52 -06:00
|
|
|
if (IS_ERR(req))
|
|
|
|
return PTR_ERR(req);
|
|
|
|
|
2007-10-18 04:07:02 -06:00
|
|
|
fuse_lk_fill(req, file, fl, opcode, pid, flock);
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2006-06-25 06:48:52 -06:00
|
|
|
err = req->out.h.error;
|
2006-06-25 06:48:54 -06:00
|
|
|
/* locking is restartable */
|
|
|
|
if (err == -EINTR)
|
|
|
|
err = -ERESTARTSYS;
|
2006-06-25 06:48:52 -06:00
|
|
|
fuse_put_request(fc, req);
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
|
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2006-06-25 06:48:52 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
int err;
|
|
|
|
|
2008-07-25 02:49:02 -06:00
|
|
|
if (cmd == F_CANCELLK) {
|
|
|
|
err = 0;
|
|
|
|
} else if (cmd == F_GETLK) {
|
2006-06-25 06:48:52 -06:00
|
|
|
if (fc->no_lock) {
|
2007-02-20 22:55:18 -07:00
|
|
|
posix_test_lock(file, fl);
|
2006-06-25 06:48:52 -06:00
|
|
|
err = 0;
|
|
|
|
} else
|
|
|
|
err = fuse_getlk(file, fl);
|
|
|
|
} else {
|
|
|
|
if (fc->no_lock)
|
2008-07-25 02:49:02 -06:00
|
|
|
err = posix_lock_file(file, fl, NULL);
|
2006-06-25 06:48:52 -06:00
|
|
|
else
|
2007-10-18 04:07:02 -06:00
|
|
|
err = fuse_setlk(file, fl, 0);
|
2006-06-25 06:48:52 -06:00
|
|
|
}
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2007-10-18 04:07:02 -06:00
|
|
|
static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
|
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2007-10-18 04:07:02 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
int err;
|
|
|
|
|
2011-08-08 08:08:08 -06:00
|
|
|
if (fc->no_flock) {
|
2007-10-18 04:07:02 -06:00
|
|
|
err = flock_lock_file_wait(file, fl);
|
|
|
|
} else {
|
2011-08-08 08:08:08 -06:00
|
|
|
struct fuse_file *ff = file->private_data;
|
|
|
|
|
2007-10-18 04:07:02 -06:00
|
|
|
/* emulate flock with POSIX locks */
|
|
|
|
fl->fl_owner = (fl_owner_t) file;
|
2011-08-08 08:08:08 -06:00
|
|
|
ff->flock = true;
|
2007-10-18 04:07:02 -06:00
|
|
|
err = fuse_setlk(file, fl, 1);
|
|
|
|
}
|
|
|
|
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2006-12-06 21:35:51 -07:00
|
|
|
static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
|
|
|
|
{
|
|
|
|
struct inode *inode = mapping->host;
|
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_bmap_in inarg;
|
|
|
|
struct fuse_bmap_out outarg;
|
|
|
|
int err;
|
|
|
|
|
|
|
|
if (!inode->i_sb->s_bdev || fc->no_bmap)
|
|
|
|
return 0;
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2006-12-06 21:35:51 -07:00
|
|
|
if (IS_ERR(req))
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
memset(&inarg, 0, sizeof(inarg));
|
|
|
|
inarg.block = block;
|
|
|
|
inarg.blocksize = inode->i_sb->s_blocksize;
|
|
|
|
req->in.h.opcode = FUSE_BMAP;
|
|
|
|
req->in.h.nodeid = get_node_id(inode);
|
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
|
|
|
req->out.numargs = 1;
|
|
|
|
req->out.args[0].size = sizeof(outarg);
|
|
|
|
req->out.args[0].value = &outarg;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2006-12-06 21:35:51 -07:00
|
|
|
err = req->out.h.error;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
if (err == -ENOSYS)
|
|
|
|
fc->no_bmap = 1;
|
|
|
|
|
|
|
|
return err ? 0 : outarg.block;
|
|
|
|
}
|
|
|
|
|
2012-12-17 16:59:39 -07:00
|
|
|
static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
|
2008-04-30 01:54:45 -06:00
|
|
|
{
|
|
|
|
loff_t retval;
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2008-04-30 01:54:45 -06:00
|
|
|
|
2011-12-13 03:58:48 -07:00
|
|
|
/* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
|
2012-12-17 16:59:39 -07:00
|
|
|
if (whence == SEEK_CUR || whence == SEEK_SET)
|
|
|
|
return generic_file_llseek(file, offset, whence);
|
2011-07-18 11:21:38 -06:00
|
|
|
|
2011-12-13 03:58:48 -07:00
|
|
|
mutex_lock(&inode->i_mutex);
|
|
|
|
retval = fuse_update_attributes(inode, NULL, file, NULL);
|
|
|
|
if (!retval)
|
2012-12-17 16:59:39 -07:00
|
|
|
retval = generic_file_llseek(file, offset, whence);
|
2008-04-30 01:54:45 -06:00
|
|
|
mutex_unlock(&inode->i_mutex);
|
2011-12-13 03:58:48 -07:00
|
|
|
|
2008-04-30 01:54:45 -06:00
|
|
|
return retval;
|
|
|
|
}
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
static int fuse_ioctl_copy_user(struct page **pages, struct iovec *iov,
|
|
|
|
unsigned int nr_segs, size_t bytes, bool to_user)
|
|
|
|
{
|
|
|
|
struct iov_iter ii;
|
|
|
|
int page_idx = 0;
|
|
|
|
|
|
|
|
if (!bytes)
|
|
|
|
return 0;
|
|
|
|
|
2014-03-05 17:28:09 -07:00
|
|
|
iov_iter_init(&ii, to_user ? READ : WRITE, iov, nr_segs, bytes);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
while (iov_iter_count(&ii)) {
|
|
|
|
struct page *page = pages[page_idx++];
|
|
|
|
size_t todo = min_t(size_t, PAGE_SIZE, iov_iter_count(&ii));
|
2010-05-07 02:28:17 -06:00
|
|
|
void *kaddr;
|
2008-11-26 04:03:55 -07:00
|
|
|
|
2010-05-07 02:28:17 -06:00
|
|
|
kaddr = kmap(page);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
while (todo) {
|
|
|
|
char __user *uaddr = ii.iov->iov_base + ii.iov_offset;
|
|
|
|
size_t iov_len = ii.iov->iov_len - ii.iov_offset;
|
|
|
|
size_t copy = min(todo, iov_len);
|
|
|
|
size_t left;
|
|
|
|
|
|
|
|
if (!to_user)
|
|
|
|
left = copy_from_user(kaddr, uaddr, copy);
|
|
|
|
else
|
|
|
|
left = copy_to_user(uaddr, kaddr, copy);
|
|
|
|
|
|
|
|
if (unlikely(left))
|
|
|
|
return -EFAULT;
|
|
|
|
|
|
|
|
iov_iter_advance(&ii, copy);
|
|
|
|
todo -= copy;
|
|
|
|
kaddr += copy;
|
|
|
|
}
|
|
|
|
|
2009-11-03 03:40:44 -07:00
|
|
|
kunmap(page);
|
2008-11-26 04:03:55 -07:00
|
|
|
}
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2010-11-30 08:39:27 -07:00
|
|
|
/*
|
|
|
|
* CUSE servers compiled on 32bit broke on 64bit kernels because the
|
|
|
|
* ABI was defined to be 'struct iovec' which is different on 32bit
|
|
|
|
* and 64bit. Fortunately we can determine which structure the server
|
|
|
|
* used from the size of the reply.
|
|
|
|
*/
|
2010-12-07 12:16:56 -07:00
|
|
|
static int fuse_copy_ioctl_iovec_old(struct iovec *dst, void *src,
|
|
|
|
size_t transferred, unsigned count,
|
|
|
|
bool is_compat)
|
2010-11-30 08:39:27 -07:00
|
|
|
{
|
|
|
|
#ifdef CONFIG_COMPAT
|
|
|
|
if (count * sizeof(struct compat_iovec) == transferred) {
|
|
|
|
struct compat_iovec *ciov = src;
|
|
|
|
unsigned i;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* With this interface a 32bit server cannot support
|
|
|
|
* non-compat (i.e. ones coming from 64bit apps) ioctl
|
|
|
|
* requests
|
|
|
|
*/
|
|
|
|
if (!is_compat)
|
|
|
|
return -EINVAL;
|
|
|
|
|
|
|
|
for (i = 0; i < count; i++) {
|
|
|
|
dst[i].iov_base = compat_ptr(ciov[i].iov_base);
|
|
|
|
dst[i].iov_len = ciov[i].iov_len;
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
|
|
|
if (count * sizeof(struct iovec) != transferred)
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
memcpy(dst, src, transferred);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2010-11-30 08:39:27 -07:00
|
|
|
/* Make sure iov_length() won't overflow */
|
|
|
|
static int fuse_verify_ioctl_iov(struct iovec *iov, size_t count)
|
|
|
|
{
|
|
|
|
size_t n;
|
|
|
|
u32 max = FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT;
|
|
|
|
|
2012-07-24 13:10:11 -06:00
|
|
|
for (n = 0; n < count; n++, iov++) {
|
2010-11-30 08:39:27 -07:00
|
|
|
if (iov->iov_len > (size_t) max)
|
|
|
|
return -ENOMEM;
|
|
|
|
max -= iov->iov_len;
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2010-12-07 12:16:56 -07:00
|
|
|
static int fuse_copy_ioctl_iovec(struct fuse_conn *fc, struct iovec *dst,
|
|
|
|
void *src, size_t transferred, unsigned count,
|
|
|
|
bool is_compat)
|
|
|
|
{
|
|
|
|
unsigned i;
|
|
|
|
struct fuse_ioctl_iovec *fiov = src;
|
|
|
|
|
|
|
|
if (fc->minor < 16) {
|
|
|
|
return fuse_copy_ioctl_iovec_old(dst, src, transferred,
|
|
|
|
count, is_compat);
|
|
|
|
}
|
|
|
|
|
|
|
|
if (count * sizeof(struct fuse_ioctl_iovec) != transferred)
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
for (i = 0; i < count; i++) {
|
|
|
|
/* Did the server supply an inappropriate value? */
|
|
|
|
if (fiov[i].base != (unsigned long) fiov[i].base ||
|
|
|
|
fiov[i].len != (unsigned long) fiov[i].len)
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
dst[i].iov_base = (void __user *) (unsigned long) fiov[i].base;
|
|
|
|
dst[i].iov_len = (size_t) fiov[i].len;
|
|
|
|
|
|
|
|
#ifdef CONFIG_COMPAT
|
|
|
|
if (is_compat &&
|
|
|
|
(ptr_to_compat(dst[i].iov_base) != fiov[i].base ||
|
|
|
|
(compat_size_t) dst[i].iov_len != fiov[i].len))
|
|
|
|
return -EIO;
|
|
|
|
#endif
|
|
|
|
}
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
/*
|
|
|
|
* For ioctls, there is no generic way to determine how much memory
|
|
|
|
* needs to be read and/or written. Furthermore, ioctls are allowed
|
|
|
|
* to dereference the passed pointer, so the parameter requires deep
|
|
|
|
* copying but FUSE has no idea whatsoever about what to copy in or
|
|
|
|
* out.
|
|
|
|
*
|
|
|
|
* This is solved by allowing FUSE server to retry ioctl with
|
|
|
|
* necessary in/out iovecs. Let's assume the ioctl implementation
|
|
|
|
* needs to read in the following structure.
|
|
|
|
*
|
|
|
|
* struct a {
|
|
|
|
* char *buf;
|
|
|
|
* size_t buflen;
|
|
|
|
* }
|
|
|
|
*
|
|
|
|
* On the first callout to FUSE server, inarg->in_size and
|
|
|
|
* inarg->out_size will be NULL; then, the server completes the ioctl
|
|
|
|
* with FUSE_IOCTL_RETRY set in out->flags, out->in_iovs set to 1 and
|
|
|
|
* the actual iov array to
|
|
|
|
*
|
|
|
|
* { { .iov_base = inarg.arg, .iov_len = sizeof(struct a) } }
|
|
|
|
*
|
|
|
|
* which tells FUSE to copy in the requested area and retry the ioctl.
|
|
|
|
* On the second round, the server has access to the structure and
|
|
|
|
* from that it can tell what to look for next, so on the invocation,
|
|
|
|
* it sets FUSE_IOCTL_RETRY, out->in_iovs to 2 and iov array to
|
|
|
|
*
|
|
|
|
* { { .iov_base = inarg.arg, .iov_len = sizeof(struct a) },
|
|
|
|
* { .iov_base = a.buf, .iov_len = a.buflen } }
|
|
|
|
*
|
|
|
|
* FUSE will copy both struct a and the pointed buffer from the
|
|
|
|
* process doing the ioctl and retry ioctl with both struct a and the
|
|
|
|
* buffer.
|
|
|
|
*
|
|
|
|
* This time, FUSE server has everything it needs and completes ioctl
|
|
|
|
* without FUSE_IOCTL_RETRY which finishes the ioctl call.
|
|
|
|
*
|
|
|
|
* Copying data out works the same way.
|
|
|
|
*
|
|
|
|
* Note that if FUSE_IOCTL_UNRESTRICTED is clear, the kernel
|
|
|
|
* automatically initializes in and out iovs by decoding @cmd with
|
|
|
|
* _IOC_* macros and the server is not allowed to request RETRY. This
|
|
|
|
* limits ioctl data transfers to well-formed ioctls and is the forced
|
|
|
|
* behavior for all FUSE servers.
|
|
|
|
*/
|
2009-04-13 19:54:53 -06:00
|
|
|
long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
|
|
|
|
unsigned int flags)
|
2008-11-26 04:03:55 -07:00
|
|
|
{
|
|
|
|
struct fuse_file *ff = file->private_data;
|
2009-04-28 08:56:39 -06:00
|
|
|
struct fuse_conn *fc = ff->fc;
|
2008-11-26 04:03:55 -07:00
|
|
|
struct fuse_ioctl_in inarg = {
|
|
|
|
.fh = ff->fh,
|
|
|
|
.cmd = cmd,
|
|
|
|
.arg = arg,
|
|
|
|
.flags = flags
|
|
|
|
};
|
|
|
|
struct fuse_ioctl_out outarg;
|
|
|
|
struct fuse_req *req = NULL;
|
|
|
|
struct page **pages = NULL;
|
2010-12-07 12:16:56 -07:00
|
|
|
struct iovec *iov_page = NULL;
|
2008-11-26 04:03:55 -07:00
|
|
|
struct iovec *in_iov = NULL, *out_iov = NULL;
|
|
|
|
unsigned int in_iovs = 0, out_iovs = 0, num_pages = 0, max_pages;
|
|
|
|
size_t in_size, out_size, transferred;
|
|
|
|
int err;
|
|
|
|
|
2010-12-07 12:16:56 -07:00
|
|
|
#if BITS_PER_LONG == 32
|
|
|
|
inarg.flags |= FUSE_IOCTL_32BIT;
|
|
|
|
#else
|
|
|
|
if (flags & FUSE_IOCTL_COMPAT)
|
|
|
|
inarg.flags |= FUSE_IOCTL_32BIT;
|
|
|
|
#endif
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
/* assume all the iovs returned by client always fits in a page */
|
2010-12-07 12:16:56 -07:00
|
|
|
BUILD_BUG_ON(sizeof(struct fuse_ioctl_iovec) * FUSE_IOCTL_MAX_IOV > PAGE_SIZE);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
err = -ENOMEM;
|
2011-11-29 14:08:00 -07:00
|
|
|
pages = kcalloc(FUSE_MAX_PAGES_PER_REQ, sizeof(pages[0]), GFP_KERNEL);
|
2010-12-07 12:16:56 -07:00
|
|
|
iov_page = (struct iovec *) __get_free_page(GFP_KERNEL);
|
2008-11-26 04:03:55 -07:00
|
|
|
if (!pages || !iov_page)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If restricted, initialize IO parameters as encoded in @cmd.
|
|
|
|
* RETRY from server is not allowed.
|
|
|
|
*/
|
|
|
|
if (!(flags & FUSE_IOCTL_UNRESTRICTED)) {
|
2010-12-07 12:16:56 -07:00
|
|
|
struct iovec *iov = iov_page;
|
2008-11-26 04:03:55 -07:00
|
|
|
|
2008-12-02 06:49:42 -07:00
|
|
|
iov->iov_base = (void __user *)arg;
|
2008-11-26 04:03:55 -07:00
|
|
|
iov->iov_len = _IOC_SIZE(cmd);
|
|
|
|
|
|
|
|
if (_IOC_DIR(cmd) & _IOC_WRITE) {
|
|
|
|
in_iov = iov;
|
|
|
|
in_iovs = 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (_IOC_DIR(cmd) & _IOC_READ) {
|
|
|
|
out_iov = iov;
|
|
|
|
out_iovs = 1;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
retry:
|
|
|
|
inarg.in_size = in_size = iov_length(in_iov, in_iovs);
|
|
|
|
inarg.out_size = out_size = iov_length(out_iov, out_iovs);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Out data can be used either for actual out data or iovs,
|
|
|
|
* make sure there always is at least one page.
|
|
|
|
*/
|
|
|
|
out_size = max_t(size_t, out_size, PAGE_SIZE);
|
|
|
|
max_pages = DIV_ROUND_UP(max(in_size, out_size), PAGE_SIZE);
|
|
|
|
|
|
|
|
/* make sure there are enough buffer pages and init request with them */
|
|
|
|
err = -ENOMEM;
|
|
|
|
if (max_pages > FUSE_MAX_PAGES_PER_REQ)
|
|
|
|
goto out;
|
|
|
|
while (num_pages < max_pages) {
|
|
|
|
pages[num_pages] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
|
|
|
|
if (!pages[num_pages])
|
|
|
|
goto out;
|
|
|
|
num_pages++;
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:49:13 -06:00
|
|
|
req = fuse_get_req(fc, num_pages);
|
2008-11-26 04:03:55 -07:00
|
|
|
if (IS_ERR(req)) {
|
|
|
|
err = PTR_ERR(req);
|
|
|
|
req = NULL;
|
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
memcpy(req->pages, pages, sizeof(req->pages[0]) * num_pages);
|
|
|
|
req->num_pages = num_pages;
|
2012-10-26 09:50:29 -06:00
|
|
|
fuse_page_descs_length_init(req, 0, req->num_pages);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
/* okay, let's send it to the client */
|
|
|
|
req->in.h.opcode = FUSE_IOCTL;
|
2009-04-28 08:56:39 -06:00
|
|
|
req->in.h.nodeid = ff->nodeid;
|
2008-11-26 04:03:55 -07:00
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
|
|
|
if (in_size) {
|
|
|
|
req->in.numargs++;
|
|
|
|
req->in.args[1].size = in_size;
|
|
|
|
req->in.argpages = 1;
|
|
|
|
|
|
|
|
err = fuse_ioctl_copy_user(pages, in_iov, in_iovs, in_size,
|
|
|
|
false);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
|
|
|
|
req->out.numargs = 2;
|
|
|
|
req->out.args[0].size = sizeof(outarg);
|
|
|
|
req->out.args[0].value = &outarg;
|
|
|
|
req->out.args[1].size = out_size;
|
|
|
|
req->out.argpages = 1;
|
|
|
|
req->out.argvar = 1;
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2008-11-26 04:03:55 -07:00
|
|
|
err = req->out.h.error;
|
|
|
|
transferred = req->out.args[1].size;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
req = NULL;
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
/* did it ask for retry? */
|
|
|
|
if (outarg.flags & FUSE_IOCTL_RETRY) {
|
2010-12-07 12:16:56 -07:00
|
|
|
void *vaddr;
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
/* no retry if in restricted mode */
|
|
|
|
err = -EIO;
|
|
|
|
if (!(flags & FUSE_IOCTL_UNRESTRICTED))
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
in_iovs = outarg.in_iovs;
|
|
|
|
out_iovs = outarg.out_iovs;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Make sure things are in boundary, separate checks
|
|
|
|
* are to protect against overflow.
|
|
|
|
*/
|
|
|
|
err = -ENOMEM;
|
|
|
|
if (in_iovs > FUSE_IOCTL_MAX_IOV ||
|
|
|
|
out_iovs > FUSE_IOCTL_MAX_IOV ||
|
|
|
|
in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
|
|
|
|
goto out;
|
|
|
|
|
2011-11-25 08:14:30 -07:00
|
|
|
vaddr = kmap_atomic(pages[0]);
|
2010-12-07 12:16:56 -07:00
|
|
|
err = fuse_copy_ioctl_iovec(fc, iov_page, vaddr,
|
2010-11-30 08:39:27 -07:00
|
|
|
transferred, in_iovs + out_iovs,
|
|
|
|
(flags & FUSE_IOCTL_COMPAT) != 0);
|
2011-11-25 08:14:30 -07:00
|
|
|
kunmap_atomic(vaddr);
|
2010-11-30 08:39:27 -07:00
|
|
|
if (err)
|
|
|
|
goto out;
|
2008-11-26 04:03:55 -07:00
|
|
|
|
2010-12-07 12:16:56 -07:00
|
|
|
in_iov = iov_page;
|
2008-11-26 04:03:55 -07:00
|
|
|
out_iov = in_iov + in_iovs;
|
|
|
|
|
2010-11-30 08:39:27 -07:00
|
|
|
err = fuse_verify_ioctl_iov(in_iov, in_iovs);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
err = fuse_verify_ioctl_iov(out_iov, out_iovs);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
goto retry;
|
|
|
|
}
|
|
|
|
|
|
|
|
err = -EIO;
|
|
|
|
if (transferred > inarg.out_size)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
err = fuse_ioctl_copy_user(pages, out_iov, out_iovs, transferred, true);
|
|
|
|
out:
|
|
|
|
if (req)
|
|
|
|
fuse_put_request(fc, req);
|
2010-12-07 12:16:56 -07:00
|
|
|
free_page((unsigned long) iov_page);
|
2008-11-26 04:03:55 -07:00
|
|
|
while (num_pages)
|
|
|
|
__free_page(pages[--num_pages]);
|
|
|
|
kfree(pages);
|
|
|
|
|
|
|
|
return err ? err : outarg.result;
|
|
|
|
}
|
2009-04-13 19:54:53 -06:00
|
|
|
EXPORT_SYMBOL_GPL(fuse_do_ioctl);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
2011-12-13 03:58:49 -07:00
|
|
|
long fuse_ioctl_common(struct file *file, unsigned int cmd,
|
|
|
|
unsigned long arg, unsigned int flags)
|
2009-04-28 08:56:39 -06:00
|
|
|
{
|
2013-02-27 14:59:05 -07:00
|
|
|
struct inode *inode = file_inode(file);
|
2009-04-28 08:56:39 -06:00
|
|
|
struct fuse_conn *fc = get_fuse_conn(inode);
|
|
|
|
|
2013-01-14 23:30:00 -07:00
|
|
|
if (!fuse_allow_current_process(fc))
|
2009-04-28 08:56:39 -06:00
|
|
|
return -EACCES;
|
|
|
|
|
|
|
|
if (is_bad_inode(inode))
|
|
|
|
return -EIO;
|
|
|
|
|
|
|
|
return fuse_do_ioctl(file, cmd, arg, flags);
|
|
|
|
}
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
static long fuse_file_ioctl(struct file *file, unsigned int cmd,
|
|
|
|
unsigned long arg)
|
|
|
|
{
|
2011-12-13 03:58:49 -07:00
|
|
|
return fuse_ioctl_common(file, cmd, arg, 0);
|
2008-11-26 04:03:55 -07:00
|
|
|
}
|
|
|
|
|
|
|
|
static long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
|
|
|
|
unsigned long arg)
|
|
|
|
{
|
2011-12-13 03:58:49 -07:00
|
|
|
return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_COMPAT);
|
2008-11-26 04:03:55 -07:00
|
|
|
}
|
|
|
|
|
2008-11-26 04:03:55 -07:00
|
|
|
/*
|
|
|
|
* All files which have been polled are linked to RB tree
|
|
|
|
* fuse_conn->polled_files which is indexed by kh. Walk the tree and
|
|
|
|
* find the matching one.
|
|
|
|
*/
|
|
|
|
static struct rb_node **fuse_find_polled_node(struct fuse_conn *fc, u64 kh,
|
|
|
|
struct rb_node **parent_out)
|
|
|
|
{
|
|
|
|
struct rb_node **link = &fc->polled_files.rb_node;
|
|
|
|
struct rb_node *last = NULL;
|
|
|
|
|
|
|
|
while (*link) {
|
|
|
|
struct fuse_file *ff;
|
|
|
|
|
|
|
|
last = *link;
|
|
|
|
ff = rb_entry(last, struct fuse_file, polled_node);
|
|
|
|
|
|
|
|
if (kh < ff->kh)
|
|
|
|
link = &last->rb_left;
|
|
|
|
else if (kh > ff->kh)
|
|
|
|
link = &last->rb_right;
|
|
|
|
else
|
|
|
|
return link;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (parent_out)
|
|
|
|
*parent_out = last;
|
|
|
|
return link;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* The file is about to be polled. Make sure it's on the polled_files
|
|
|
|
* RB tree. Note that files once added to the polled_files tree are
|
|
|
|
* not removed before the file is released. This is because a file
|
|
|
|
* polled once is likely to be polled again.
|
|
|
|
*/
|
|
|
|
static void fuse_register_polled_file(struct fuse_conn *fc,
|
|
|
|
struct fuse_file *ff)
|
|
|
|
{
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
if (RB_EMPTY_NODE(&ff->polled_node)) {
|
2014-02-05 16:24:57 -07:00
|
|
|
struct rb_node **link, *uninitialized_var(parent);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
link = fuse_find_polled_node(fc, ff->kh, &parent);
|
|
|
|
BUG_ON(*link);
|
|
|
|
rb_link_node(&ff->polled_node, parent, link);
|
|
|
|
rb_insert_color(&ff->polled_node, &fc->polled_files);
|
|
|
|
}
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
}
|
|
|
|
|
2009-04-13 19:54:53 -06:00
|
|
|
unsigned fuse_file_poll(struct file *file, poll_table *wait)
|
2008-11-26 04:03:55 -07:00
|
|
|
{
|
|
|
|
struct fuse_file *ff = file->private_data;
|
2009-04-28 08:56:41 -06:00
|
|
|
struct fuse_conn *fc = ff->fc;
|
2008-11-26 04:03:55 -07:00
|
|
|
struct fuse_poll_in inarg = { .fh = ff->fh, .kh = ff->kh };
|
|
|
|
struct fuse_poll_out outarg;
|
|
|
|
struct fuse_req *req;
|
|
|
|
int err;
|
|
|
|
|
|
|
|
if (fc->no_poll)
|
|
|
|
return DEFAULT_POLLMASK;
|
|
|
|
|
|
|
|
poll_wait(file, &ff->poll_wait, wait);
|
2013-02-04 08:14:32 -07:00
|
|
|
inarg.events = (__u32)poll_requested_events(wait);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Ask for notification iff there's someone waiting for it.
|
|
|
|
* The client may ignore the flag and always notify.
|
|
|
|
*/
|
|
|
|
if (waitqueue_active(&ff->poll_wait)) {
|
|
|
|
inarg.flags |= FUSE_POLL_SCHEDULE_NOTIFY;
|
|
|
|
fuse_register_polled_file(fc, ff);
|
|
|
|
}
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2008-11-26 04:03:55 -07:00
|
|
|
if (IS_ERR(req))
|
2009-06-30 12:06:24 -06:00
|
|
|
return POLLERR;
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
req->in.h.opcode = FUSE_POLL;
|
2009-04-28 08:56:41 -06:00
|
|
|
req->in.h.nodeid = ff->nodeid;
|
2008-11-26 04:03:55 -07:00
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
|
|
|
req->out.numargs = 1;
|
|
|
|
req->out.args[0].size = sizeof(outarg);
|
|
|
|
req->out.args[0].value = &outarg;
|
2008-11-26 04:03:55 -07:00
|
|
|
fuse_request_send(fc, req);
|
2008-11-26 04:03:55 -07:00
|
|
|
err = req->out.h.error;
|
|
|
|
fuse_put_request(fc, req);
|
|
|
|
|
|
|
|
if (!err)
|
|
|
|
return outarg.revents;
|
|
|
|
if (err == -ENOSYS) {
|
|
|
|
fc->no_poll = 1;
|
|
|
|
return DEFAULT_POLLMASK;
|
|
|
|
}
|
|
|
|
return POLLERR;
|
|
|
|
}
|
2009-04-13 19:54:53 -06:00
|
|
|
EXPORT_SYMBOL_GPL(fuse_file_poll);
|
2008-11-26 04:03:55 -07:00
|
|
|
|
|
|
|
/*
|
|
|
|
* This is called from fuse_handle_notify() on FUSE_NOTIFY_POLL and
|
|
|
|
* wakes up the poll waiters.
|
|
|
|
*/
|
|
|
|
int fuse_notify_poll_wakeup(struct fuse_conn *fc,
|
|
|
|
struct fuse_notify_poll_wakeup_out *outarg)
|
|
|
|
{
|
|
|
|
u64 kh = outarg->kh;
|
|
|
|
struct rb_node **link;
|
|
|
|
|
|
|
|
spin_lock(&fc->lock);
|
|
|
|
|
|
|
|
link = fuse_find_polled_node(fc, kh, NULL);
|
|
|
|
if (*link) {
|
|
|
|
struct fuse_file *ff;
|
|
|
|
|
|
|
|
ff = rb_entry(*link, struct fuse_file, polled_node);
|
|
|
|
wake_up_interruptible_sync(&ff->poll_wait);
|
|
|
|
}
|
|
|
|
|
|
|
|
spin_unlock(&fc->lock);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2012-12-18 03:05:08 -07:00
|
|
|
static void fuse_do_truncate(struct file *file)
|
|
|
|
{
|
|
|
|
struct inode *inode = file->f_mapping->host;
|
|
|
|
struct iattr attr;
|
|
|
|
|
|
|
|
attr.ia_valid = ATTR_SIZE;
|
|
|
|
attr.ia_size = i_size_read(inode);
|
|
|
|
|
|
|
|
attr.ia_file = file;
|
|
|
|
attr.ia_valid |= ATTR_FILE;
|
|
|
|
|
|
|
|
fuse_do_setattr(inode, &attr, file);
|
|
|
|
}
|
|
|
|
|
2013-05-30 06:41:34 -06:00
|
|
|
static inline loff_t fuse_round_up(loff_t off)
|
|
|
|
{
|
|
|
|
return round_up(off, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
|
|
|
|
}
|
|
|
|
|
2012-02-17 10:46:25 -07:00
|
|
|
static ssize_t
|
2014-03-04 19:27:34 -07:00
|
|
|
fuse_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter,
|
|
|
|
loff_t offset)
|
2012-02-17 10:46:25 -07:00
|
|
|
{
|
|
|
|
ssize_t ret = 0;
|
2013-05-01 06:37:21 -06:00
|
|
|
struct file *file = iocb->ki_filp;
|
|
|
|
struct fuse_file *ff = file->private_data;
|
2013-05-30 06:41:34 -06:00
|
|
|
bool async_dio = ff->fc->async_dio;
|
2012-02-17 10:46:25 -07:00
|
|
|
loff_t pos = 0;
|
2012-12-14 08:21:08 -07:00
|
|
|
struct inode *inode;
|
|
|
|
loff_t i_size;
|
2014-03-04 20:38:00 -07:00
|
|
|
size_t count = iov_iter_count(iter);
|
2012-12-14 08:20:51 -07:00
|
|
|
struct fuse_io_priv *io;
|
2012-02-17 10:46:25 -07:00
|
|
|
|
|
|
|
pos = offset;
|
2012-12-14 08:21:08 -07:00
|
|
|
inode = file->f_mapping->host;
|
|
|
|
i_size = i_size_read(inode);
|
2012-02-17 10:46:25 -07:00
|
|
|
|
Fix race when checking i_size on direct i/o read
So far I've had one ACK for this, and no other comments. So I think it
is probably time to send this via some suitable tree. I'm guessing that
the vfs tree would be the most appropriate route, but not sure that
there is one at the moment (don't see anything recent at kernel.org)
so in that case I think -mm is the "back up plan". Al, please let me
know if you will take this?
Steve.
---------------------
Following on from the "Re: [PATCH v3] vfs: fix a bug when we do some dio
reads with append dio writes" thread on linux-fsdevel, this patch is my
current version of the fix proposed as option (b) in that thread.
Removing the i_size test from the direct i/o read path at vfs level
means that filesystems now have to deal with requests which are beyond
i_size themselves. These I've divided into three sets:
a) Those with "no op" ->direct_IO (9p, cifs, ceph)
These are obviously not going to be an issue
b) Those with "home brew" ->direct_IO (nfs, fuse)
I've been told that NFS should not have any problem with the larger
i_size, however I've added an extra test to FUSE to duplicate the
original behaviour just to be on the safe side.
c) Those using __blockdev_direct_IO()
These call through to ->get_block() which should deal with the EOF
condition correctly. I've verified that with GFS2 and I believe that
Zheng has verified it for ext4. I've also run the test on XFS and it
passes both before and after this change.
The part of the patch in filemap.c looks a lot larger than it really is
- there are only two lines of real change. The rest is just indentation
of the contained code.
There remains a test of i_size though, which was added for btrfs. It
doesn't cause the other filesystems a problem as the test is performed
after ->direct_IO has been called. It is possible that there is a race
that does matter to btrfs, however this patch doesn't change that, so
its still an overall improvement.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reported-by: Zheng Liu <gnehzuil.liu@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-01-24 07:42:22 -07:00
|
|
|
if ((rw == READ) && (offset > i_size))
|
|
|
|
return 0;
|
|
|
|
|
2012-12-14 08:21:26 -07:00
|
|
|
/* optimization for short read */
|
2013-05-30 06:41:34 -06:00
|
|
|
if (async_dio && rw != WRITE && offset + count > i_size) {
|
2012-12-14 08:21:26 -07:00
|
|
|
if (offset >= i_size)
|
|
|
|
return 0;
|
2013-05-30 06:41:34 -06:00
|
|
|
count = min_t(loff_t, count, fuse_round_up(i_size - offset));
|
2014-03-16 13:50:47 -06:00
|
|
|
if (iter->count > count)
|
|
|
|
iter->count = count;
|
2012-12-14 08:21:26 -07:00
|
|
|
}
|
|
|
|
|
2012-12-14 08:21:08 -07:00
|
|
|
io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
|
2012-12-14 08:20:51 -07:00
|
|
|
if (!io)
|
|
|
|
return -ENOMEM;
|
2012-12-14 08:21:08 -07:00
|
|
|
spin_lock_init(&io->lock);
|
|
|
|
io->reqs = 1;
|
|
|
|
io->bytes = -1;
|
|
|
|
io->size = 0;
|
|
|
|
io->offset = offset;
|
|
|
|
io->write = (rw == WRITE);
|
|
|
|
io->err = 0;
|
2012-12-14 08:20:51 -07:00
|
|
|
io->file = file;
|
2012-12-14 08:21:08 -07:00
|
|
|
/*
|
|
|
|
* By default, we want to optimize all I/Os with async request
|
2013-05-01 06:37:21 -06:00
|
|
|
* submission to the client filesystem if supported.
|
2012-12-14 08:21:08 -07:00
|
|
|
*/
|
2013-05-30 06:41:34 -06:00
|
|
|
io->async = async_dio;
|
2012-12-14 08:21:08 -07:00
|
|
|
io->iocb = iocb;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We cannot asynchronously extend the size of a file. We have no method
|
|
|
|
* to wait on real async I/O requests, so we must submit this request
|
|
|
|
* synchronously.
|
|
|
|
*/
|
2013-05-30 06:41:34 -06:00
|
|
|
if (!is_sync_kiocb(iocb) && (offset + count > i_size) && rw == WRITE)
|
2012-12-14 08:21:08 -07:00
|
|
|
io->async = false;
|
2012-02-17 10:46:25 -07:00
|
|
|
|
2012-10-26 09:50:15 -06:00
|
|
|
if (rw == WRITE)
|
2014-03-16 13:50:47 -06:00
|
|
|
ret = __fuse_direct_write(io, iter, &pos);
|
2012-10-26 09:50:15 -06:00
|
|
|
else
|
2014-03-16 13:50:47 -06:00
|
|
|
ret = __fuse_direct_read(io, iter, &pos);
|
2012-12-14 08:20:51 -07:00
|
|
|
|
2012-12-14 08:21:08 -07:00
|
|
|
if (io->async) {
|
|
|
|
fuse_aio_complete(io, ret < 0 ? ret : 0, -1);
|
|
|
|
|
|
|
|
/* we have a non-extending, async request, so return */
|
2013-05-30 13:35:50 -06:00
|
|
|
if (!is_sync_kiocb(iocb))
|
2012-12-14 08:21:08 -07:00
|
|
|
return -EIOCBQUEUED;
|
|
|
|
|
|
|
|
ret = wait_on_sync_kiocb(iocb);
|
|
|
|
} else {
|
|
|
|
kfree(io);
|
|
|
|
}
|
|
|
|
|
2012-12-18 03:05:08 -07:00
|
|
|
if (rw == WRITE) {
|
|
|
|
if (ret > 0)
|
|
|
|
fuse_write_update_size(inode, pos);
|
|
|
|
else if (ret < 0 && offset + count > i_size)
|
|
|
|
fuse_do_truncate(file);
|
|
|
|
}
|
2012-02-17 10:46:25 -07:00
|
|
|
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
2012-11-10 08:55:56 -07:00
|
|
|
static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
|
|
|
|
loff_t length)
|
2012-04-22 19:45:24 -06:00
|
|
|
{
|
|
|
|
struct fuse_file *ff = file->private_data;
|
2013-05-17 07:30:32 -06:00
|
|
|
struct inode *inode = file->f_inode;
|
2013-09-13 09:20:16 -06:00
|
|
|
struct fuse_inode *fi = get_fuse_inode(inode);
|
2012-04-22 19:45:24 -06:00
|
|
|
struct fuse_conn *fc = ff->fc;
|
|
|
|
struct fuse_req *req;
|
|
|
|
struct fuse_fallocate_in inarg = {
|
|
|
|
.fh = ff->fh,
|
|
|
|
.offset = offset,
|
|
|
|
.length = length,
|
|
|
|
.mode = mode
|
|
|
|
};
|
|
|
|
int err;
|
2013-06-13 02:16:39 -06:00
|
|
|
bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) ||
|
|
|
|
(mode & FALLOC_FL_PUNCH_HOLE);
|
2012-04-22 19:45:24 -06:00
|
|
|
|
2014-04-28 06:19:21 -06:00
|
|
|
if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
|
2012-04-26 02:56:36 -06:00
|
|
|
if (fc->no_fallocate)
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
|
2013-06-13 02:16:39 -06:00
|
|
|
if (lock_inode) {
|
2013-05-17 07:30:32 -06:00
|
|
|
mutex_lock(&inode->i_mutex);
|
2013-09-13 09:19:54 -06:00
|
|
|
if (mode & FALLOC_FL_PUNCH_HOLE) {
|
|
|
|
loff_t endbyte = offset + length - 1;
|
|
|
|
err = filemap_write_and_wait_range(inode->i_mapping,
|
|
|
|
offset, endbyte);
|
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
fuse_sync_writes(inode);
|
|
|
|
}
|
2013-05-17 07:30:32 -06:00
|
|
|
}
|
|
|
|
|
2013-09-13 09:20:16 -06:00
|
|
|
if (!(mode & FALLOC_FL_KEEP_SIZE))
|
|
|
|
set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
|
|
|
|
|
2012-10-26 09:48:30 -06:00
|
|
|
req = fuse_get_req_nopages(fc);
|
2013-05-17 07:30:32 -06:00
|
|
|
if (IS_ERR(req)) {
|
|
|
|
err = PTR_ERR(req);
|
|
|
|
goto out;
|
|
|
|
}
|
2012-04-22 19:45:24 -06:00
|
|
|
|
|
|
|
req->in.h.opcode = FUSE_FALLOCATE;
|
|
|
|
req->in.h.nodeid = ff->nodeid;
|
|
|
|
req->in.numargs = 1;
|
|
|
|
req->in.args[0].size = sizeof(inarg);
|
|
|
|
req->in.args[0].value = &inarg;
|
|
|
|
fuse_request_send(fc, req);
|
|
|
|
err = req->out.h.error;
|
2012-04-26 02:56:36 -06:00
|
|
|
if (err == -ENOSYS) {
|
|
|
|
fc->no_fallocate = 1;
|
|
|
|
err = -EOPNOTSUPP;
|
|
|
|
}
|
2012-04-22 19:45:24 -06:00
|
|
|
fuse_put_request(fc, req);
|
|
|
|
|
2013-05-17 13:27:34 -06:00
|
|
|
if (err)
|
|
|
|
goto out;
|
|
|
|
|
|
|
|
/* we could have extended the file */
|
2013-12-26 08:51:11 -07:00
|
|
|
if (!(mode & FALLOC_FL_KEEP_SIZE)) {
|
|
|
|
bool changed = fuse_write_update_size(inode, offset + length);
|
|
|
|
|
2014-04-28 06:19:22 -06:00
|
|
|
if (changed && fc->writeback_cache)
|
|
|
|
file_update_time(file);
|
2013-12-26 08:51:11 -07:00
|
|
|
}
|
2013-05-17 13:27:34 -06:00
|
|
|
|
|
|
|
if (mode & FALLOC_FL_PUNCH_HOLE)
|
|
|
|
truncate_pagecache_range(inode, offset, offset + length - 1);
|
|
|
|
|
|
|
|
fuse_invalidate_attr(inode);
|
|
|
|
|
2013-05-17 07:30:32 -06:00
|
|
|
out:
|
2013-09-13 09:20:16 -06:00
|
|
|
if (!(mode & FALLOC_FL_KEEP_SIZE))
|
|
|
|
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
|
|
|
|
|
2013-09-13 09:19:54 -06:00
|
|
|
if (lock_inode)
|
2013-05-17 07:30:32 -06:00
|
|
|
mutex_unlock(&inode->i_mutex);
|
|
|
|
|
2012-04-22 19:45:24 -06:00
|
|
|
return err;
|
|
|
|
}
|
|
|
|
|
2006-03-28 02:56:42 -07:00
|
|
|
static const struct file_operations fuse_file_operations = {
|
2008-04-30 01:54:45 -06:00
|
|
|
.llseek = fuse_file_llseek,
|
2006-10-01 00:28:48 -06:00
|
|
|
.read = do_sync_read,
|
2007-11-28 17:21:59 -07:00
|
|
|
.aio_read = fuse_file_aio_read,
|
2006-10-01 00:28:48 -06:00
|
|
|
.write = do_sync_write,
|
2008-04-30 01:54:42 -06:00
|
|
|
.aio_write = fuse_file_aio_write,
|
2005-09-09 14:10:30 -06:00
|
|
|
.mmap = fuse_file_mmap,
|
|
|
|
.open = fuse_open,
|
|
|
|
.flush = fuse_flush,
|
|
|
|
.release = fuse_release,
|
|
|
|
.fsync = fuse_fsync,
|
2006-06-25 06:48:52 -06:00
|
|
|
.lock = fuse_file_lock,
|
2007-10-18 04:07:02 -06:00
|
|
|
.flock = fuse_file_flock,
|
2007-06-01 03:49:19 -06:00
|
|
|
.splice_read = generic_file_splice_read,
|
2008-11-26 04:03:55 -07:00
|
|
|
.unlocked_ioctl = fuse_file_ioctl,
|
|
|
|
.compat_ioctl = fuse_file_compat_ioctl,
|
2008-11-26 04:03:55 -07:00
|
|
|
.poll = fuse_file_poll,
|
2012-04-22 19:45:24 -06:00
|
|
|
.fallocate = fuse_file_fallocate,
|
2005-09-09 14:10:30 -06:00
|
|
|
};
|
|
|
|
|
2006-03-28 02:56:42 -07:00
|
|
|
static const struct file_operations fuse_direct_io_file_operations = {
|
2008-04-30 01:54:45 -06:00
|
|
|
.llseek = fuse_file_llseek,
|
2005-09-09 14:10:35 -06:00
|
|
|
.read = fuse_direct_read,
|
|
|
|
.write = fuse_direct_write,
|
2009-04-02 06:25:35 -06:00
|
|
|
.mmap = fuse_direct_mmap,
|
2005-09-09 14:10:35 -06:00
|
|
|
.open = fuse_open,
|
|
|
|
.flush = fuse_flush,
|
|
|
|
.release = fuse_release,
|
|
|
|
.fsync = fuse_fsync,
|
2006-06-25 06:48:52 -06:00
|
|
|
.lock = fuse_file_lock,
|
2007-10-18 04:07:02 -06:00
|
|
|
.flock = fuse_file_flock,
|
2008-11-26 04:03:55 -07:00
|
|
|
.unlocked_ioctl = fuse_file_ioctl,
|
|
|
|
.compat_ioctl = fuse_file_compat_ioctl,
|
2008-11-26 04:03:55 -07:00
|
|
|
.poll = fuse_file_poll,
|
2012-04-22 19:45:24 -06:00
|
|
|
.fallocate = fuse_file_fallocate,
|
2009-04-02 06:25:35 -06:00
|
|
|
/* no splice_read */
|
2005-09-09 14:10:35 -06:00
|
|
|
};
|
|
|
|
|
2006-06-28 05:26:44 -06:00
|
|
|
static const struct address_space_operations fuse_file_aops = {
|
2005-09-09 14:10:30 -06:00
|
|
|
.readpage = fuse_readpage,
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
.writepage = fuse_writepage,
|
2013-06-29 11:45:29 -06:00
|
|
|
.writepages = fuse_writepages,
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
.launder_page = fuse_launder_page,
|
2005-09-09 14:10:33 -06:00
|
|
|
.readpages = fuse_readpages,
|
fuse: support writable mmap
Quoting Linus (3 years ago, FUSE inclusion discussions):
"User-space filesystems are hard to get right. I'd claim that they
are almost impossible, unless you limit them somehow (shared
writable mappings are the nastiest part - if you don't have those,
you can reasonably limit your problems by limiting the number of
dirty pages you accept through normal "write()" calls)."
Instead of attempting the impossible, I've just waited for the dirty page
accounting infrastructure to materialize (thanks to Peter Zijlstra and
others). This nicely solved the biggest problem: limiting the number of pages
used for write caching.
Some small details remained, however, which this largish patch attempts to
address. It provides a page writeback implementation for fuse, which is
completely safe against VM related deadlocks. Performance may not be very
good for certain usage patterns, but generally it should be acceptable.
It has been tested extensively with fsx-linux and bash-shared-mapping.
Fuse page writeback design
--------------------------
fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM.
It copies the contents of the original page, and queues a WRITE request to the
userspace filesystem using this temp page.
The writeback is finished instantly from the MM's point of view: the page is
removed from the radix trees, and the PageDirty and PageWriteback flags are
cleared.
For the duration of the actual write, the NR_WRITEBACK_TEMP counter is
incremented. The per-bdi writeback count is not decremented until the actual
write completes.
On dirtying the page, fuse waits for a previous write to finish before
proceeding. This makes sure, there can only be one temporary page used at a
time for one cached page.
This approach is wasteful in both memory and CPU bandwidth, so why is this
complication needed?
The basic problem is that there can be no guarantee about the time in which
the userspace filesystem will complete a write. It may be buggy or even
malicious, and fail to complete WRITE requests. We don't want unrelated parts
of the system to grind to a halt in such cases.
Also a filesystem may need additional resources (particularly memory) to
complete a WRITE request. There's a great danger of a deadlock if that
allocation may wait for the writepage to finish.
Currently there are several cases where the kernel can block on page
writeback:
- allocation order is larger than PAGE_ALLOC_COSTLY_ORDER
- page migration
- throttle_vm_writeout (through NR_WRITEBACK)
- sync(2)
Of course in some cases (fsync, msync) we explicitly want to allow blocking.
So for these cases new code has to be added to fuse, since the VM is not
tracking writeback pages for us any more.
As an extra safetly measure, the maximum dirty ratio allocated to a single
fuse filesystem is set to 1% by default. This way one (or several) buggy or
malicious fuse filesystems cannot slow down the rest of the system by hogging
dirty memory.
With appropriate privileges, this limit can be raised through
'/sys/class/bdi/<bdi>/max_ratio'.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 01:54:41 -06:00
|
|
|
.set_page_dirty = __set_page_dirty_nobuffers,
|
2006-12-06 21:35:51 -07:00
|
|
|
.bmap = fuse_bmap,
|
2012-02-17 10:46:25 -07:00
|
|
|
.direct_IO = fuse_direct_IO,
|
2013-10-10 07:11:43 -06:00
|
|
|
.write_begin = fuse_write_begin,
|
|
|
|
.write_end = fuse_write_end,
|
2005-09-09 14:10:30 -06:00
|
|
|
};
|
|
|
|
|
|
|
|
void fuse_init_file_inode(struct inode *inode)
|
|
|
|
{
|
2005-09-09 14:10:37 -06:00
|
|
|
inode->i_fop = &fuse_file_operations;
|
|
|
|
inode->i_data.a_ops = &fuse_file_aops;
|
2005-09-09 14:10:30 -06:00
|
|
|
}
|