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Miklos Szeredi dd3bb14f44 fuse: support splice() writing to fuse device 
Allow userspace filesystem implementation to use splice() to write to
the fuse device.  The semantics of using splice() are:

 1) buffer the message header and data in a temporary pipe
 2) with a *single* splice() call move the message from the temporary pipe
    to the fuse device

The READ reply message has the most interesting use for this, since
now the data from an arbitrary file descriptor (which could be a
regular file, a block device or a socket) can be tranferred into the
fuse device without having to go through a userspace buffer.  It will
also allow zero copy moving of pages.

One caveat is that the protocol on the fuse device requires the length
of the whole message to be written into the header.  But the length of
the data transferred into the temporary pipe may not be known in
advance.  The current library implementation works around this by
using vmplice to write the header and modifying the header after
splicing the data into the pipe (error handling omitted):

	struct fuse_out_header out;

	iov.iov_base = &out;
	iov.iov_len = sizeof(struct fuse_out_header);
	vmsplice(pip[1], &iov, 1, 0);
	len = splice(input_fd, input_offset, pip[1], NULL, len, 0);
	/* retrospectively modify the header: */
	out.len = len + sizeof(struct fuse_out_header);
	splice(pip[0], NULL, fuse_chan_fd(req->ch), NULL, out.len, flags);

This works since vmsplice only saves a pointer to the data, it does
not copy the data itself.

Since pipes are currently limited to 16 pages and messages need to be
spliced atomically, the length of the data is limited to 15 pages (or
60kB for 4k pages).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
2010-05-25 15:06:06 +02:00
..
9p Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs 2010-05-24 07:41:13 -07:00
adfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
affs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
afs AFS: Don't put struct file on the stack 2010-05-21 18:31:28 -04:00
autofs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
autofs4 autofs4: Pushdown the bkl from ioctl 2010-05-22 17:44:18 +02:00
befs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
bfs bfs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:25 -04:00
btrfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
cachefiles CacheFiles: Fix error handling in cachefiles_determine_cache_security() 2010-05-12 18:23:58 -07:00
ceph Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2010-05-24 07:37:52 -07:00
cifs cifs: fix noserverino handling when unix extensions are enabled 2010-05-17 20:59:21 +00:00
coda Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-24 08:01:10 -07:00
configfs Fix the regression created by "set S_DEAD on unlink()..." commit 2010-05-15 07:16:33 -04:00
cramfs
debugfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
devpts Simplify devpts_get_sb() failure exits 2010-05-21 18:31:12 -04:00
dlm dlm: fix ast ordering for user locks 2010-04-30 14:52:51 -05:00
ecryptfs switch ecryptfs_write() to struct inode *, kill on-stack fake files 2010-05-21 18:31:28 -04:00
efs
exofs Merge branch 'for-linus' of git://git.open-osd.org/linux-open-osd 2010-05-24 07:57:41 -07:00
exportfs
ext2 ext2: replace inode uid,gid,mode init with helper 2010-05-21 18:31:24 -04:00
ext3 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
ext4 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
fat Merge git://git.kernel.org/pub/scm/linux/kernel/git/hirofumi/fatfs-2.6 2010-05-24 07:41:47 -07:00
freevxfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
fscache fs-cache: order the debugfs stats correctly 2010-04-07 08:38:05 -07:00
fuse fuse: support splice() writing to fuse device 2010-05-25 15:06:06 +02:00
gfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
hfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
hfsplus hfsplus: Push down BKL into ioctl function 2010-05-17 05:27:03 +02:00
hostfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
hpfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
hppfs hppfs can use existing proc_mnt, no need for do_kern_mount() in there 2010-03-03 14:08:00 -05:00
hugetlbfs
isofs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
jbd ext3: Fix waiting on transaction during fsync 2010-05-21 19:30:41 +02:00
jbd2 Merge branch 'master' into for-2.6.35 2010-05-21 21:27:26 +02:00
jffs2 jffs2: constify xattr_handler 2010-05-21 18:31:20 -04:00
jfs jfs: replace inode uid,gid,mode init with helper 2010-05-21 18:31:23 -04:00
lockd include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
logfs logfs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:27 -04:00
minix minix: replace inode uid,gid,mode init with helper 2010-05-21 18:31:24 -04:00
ncpfs ncpfs: BKL ioctl pushdown 2010-05-17 05:27:42 +02:00
nfs NFS: Don't call iput() in nfs_access_cache_shrinker 2010-05-14 15:09:36 -04:00
nfs_common include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
nfsd sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nilfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
nls
notify Saner locking around deactivate_super() 2010-05-21 18:31:14 -04:00
ntfs include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ocfs2 ocfs2: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:25 -04:00
omfs omfs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:25 -04:00
openpromfs
partitions Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
proc Merge branch 'bkl/procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-19 17:23:28 -07:00
qnx4 fs/qnx4: decrement sizeof size in strncmp 2010-02-04 11:55:46 +01:00
quota new helper: iterate_supers() 2010-05-21 18:31:16 -04:00
ramfs ramfs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:26 -04:00
reiserfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
romfs fix leak in romfs_fill_super() 2010-01-26 22:22:26 -05:00
smbfs smbfs: Push down BKL into ioctl function 2010-05-17 05:27:04 +02:00
squashfs squashfs: fix potential buffer over-run on 4K block file systems 2010-04-25 02:09:05 +01:00
sysfs sysfs: add struct file* to bin_attr callbacks 2010-05-21 09:37:31 -07:00
sysv sysv: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:26 -04:00
ubifs ubifs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:26 -04:00
udf udf: replace inode uid,gid,mode init with helper 2010-05-21 18:31:27 -04:00
ufs ufs: replace inode uid,gid,mode initialization with helper function 2010-05-21 18:31:27 -04:00
xfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
aio.c
anon_inodes.c anon_inode: set S_IFREG on the anon_inode 2010-05-21 18:31:20 -04:00
attr.c fs: use rlimit helpers 2010-03-06 11:26:29 -08:00
bad_inode.c
binfmt_aout.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
binfmt_elf.c coredump: pass mm->flags as a coredump parameter for consistency 2010-03-06 11:26:46 -08:00
binfmt_elf_fdpic.c Remove redundant check for CONFIG_MMU 2010-04-27 09:01:26 -07:00
binfmt_em86.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
binfmt_flat.c uclinux: error message when FLAT reloc symbol is invalid, v2 2010-04-21 13:28:49 +10:00
binfmt_misc.c
binfmt_script.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
binfmt_som.c Split 'flush_old_exec' into two functions 2010-01-29 08:22:01 -08:00
bio-integrity.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
bio.c Merge branch 'master' into for-linus 2010-03-19 08:05:10 +01:00
block_dev.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
buffer.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
char_dev.c
compat.c revert "procfs: provide stack information for threads" and its fixup commits 2010-05-11 17:33:41 -07:00
compat_binfmt_elf.c elf coredump: replace ELF_CORE_EXTRA_* macros by functions 2010-03-06 11:26:45 -08:00
compat_ioctl.c pktcdvd: improve BKL and compat_ioctl.c usage 2010-04-29 08:44:37 -07:00
dcache.c fix prune_dcache()/umount() race 2010-05-21 18:31:16 -04:00
dcookies.c
direct-io.c
drop_caches.c new helper: iterate_supers() 2010-05-21 18:31:16 -04:00
eventfd.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
eventpoll.c sched, wait: Use wrapper functions 2010-05-11 17:43:58 +02:00
exec.c revert "procfs: provide stack information for threads" and its fixup commits 2010-05-11 17:33:41 -07:00
fcntl.c Merge branch 'master' into for-2.6.35 2010-05-21 21:27:26 +02:00
fifo.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
file.c fs: use rlimit helpers 2010-03-06 11:26:29 -08:00
file_table.c vfs: take f_lock on modifying f_mode after open time 2010-03-06 11:26:25 -08:00
filesystems.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
fs-writeback.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
fs_struct.c
generic_acl.c fs: xattr_handler table should be const 2010-05-21 18:31:18 -04:00
inode.c vfs: Add inode uid,gid,mode init helper 2010-05-21 18:31:22 -04:00
internal.h Bury __put_super_and_need_restart() 2010-05-21 18:31:16 -04:00
ioctl.c Introduce freeze_super and thaw_super for the fsfreeze ioctl 2010-05-21 18:31:18 -04:00
ioprio.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2010-03-19 09:43:06 -07:00
Kconfig.binfmt
libfs.c FS / libfs: Implement simple_write_to_buffer 2010-05-10 23:08:17 +02:00
locks.c Merge branch 'for-next' into for-linus 2010-03-08 16:55:37 +01:00
Makefile Take statfs variants to fs/statfs.c 2010-05-21 18:31:17 -04:00
mbcache.c
mpage.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
namei.c namei.c : update mnt when it needed 2010-05-21 18:31:22 -04:00
namespace.c Merge branch 'next' into for-linus 2010-05-18 08:57:00 +10:00
nfsctl.c Switch may_open() and break_lease() to passing O_... 2010-03-03 13:00:21 -05:00
no-block.c
open.c Take statfs variants to fs/statfs.c 2010-05-21 18:31:17 -04:00
pipe.c pipe: set lower and upper limit on max pages in the pipe page array 2010-05-21 21:12:52 +02:00
pnode.c Kill CL_PROPAGATION, sanitize fs/pnode.c:get_source() 2010-03-03 13:00:22 -05:00
pnode.h VFS: Clean up shared mount flag propagation 2010-03-03 14:07:55 -05:00
posix_acl.c
read_write.c do_sync_read/write() should set kiocb.ki_nbytes to be consistent 2010-03-24 16:43:29 -07:00
read_write.h
readdir.c
select.c Add generic sys_old_select() 2010-03-12 15:52:32 -08:00
seq_file.c seq_file: fix new kernel-doc warnings 2010-03-07 15:48:26 -08:00
signalfd.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
splice.c pipe: add support for shrinking and growing pipes 2010-05-21 21:12:40 +02:00
stack.c
stat.c
statfs.c Take statfs variants to fs/statfs.c 2010-05-21 18:31:17 -04:00
super.c vfs: add lockdep annotation to s_vfs_rename_key for ecryptfs 2010-05-21 18:31:22 -04:00
sync.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-05-21 19:37:45 -07:00
timerfd.c fs/timerfd.c: make use of wait_event_interruptible_locked_irq() 2010-05-20 13:21:42 -07:00
utimes.c
xattr.c fs: xattr_handler table should be const 2010-05-21 18:31:18 -04:00
xattr_acl.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00