2009-09-23 12:00:27 -06:00
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/*
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* V9FS cache definitions.
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*
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* Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to:
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* Free Software Foundation
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02111-1301 USA
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*
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*/
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#include <linux/jiffies.h>
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#include <linux/file.h>
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#include <linux/stat.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <net/9p/9p.h>
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#include "v9fs.h"
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#include "cache.h"
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#define CACHETAG_LEN 11
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struct kmem_cache *vcookie_cache;
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struct fscache_netfs v9fs_cache_netfs = {
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.name = "9p",
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.version = 0,
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};
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static void init_once(void *foo)
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{
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struct v9fs_cookie *vcookie = (struct v9fs_cookie *) foo;
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vcookie->fscache = NULL;
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vcookie->qid = NULL;
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inode_init_once(&vcookie->inode);
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}
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/**
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* v9fs_init_vcookiecache - initialize a cache for vcookies to maintain
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* vcookie to inode mapping
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*
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* Returns 0 on success.
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*/
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static int v9fs_init_vcookiecache(void)
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{
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vcookie_cache = kmem_cache_create("vcookie_cache",
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sizeof(struct v9fs_cookie),
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0, (SLAB_RECLAIM_ACCOUNT|
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SLAB_MEM_SPREAD),
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init_once);
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if (!vcookie_cache)
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return -ENOMEM;
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return 0;
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}
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/**
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* v9fs_destroy_vcookiecache - destroy the cache of vcookies
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*
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*/
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static void v9fs_destroy_vcookiecache(void)
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{
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kmem_cache_destroy(vcookie_cache);
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}
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int __v9fs_cache_register(void)
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{
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int ret;
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ret = v9fs_init_vcookiecache();
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if (ret < 0)
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return ret;
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return fscache_register_netfs(&v9fs_cache_netfs);
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}
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void __v9fs_cache_unregister(void)
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{
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v9fs_destroy_vcookiecache();
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fscache_unregister_netfs(&v9fs_cache_netfs);
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}
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/**
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* v9fs_random_cachetag - Generate a random tag to be associated
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* with a new cache session.
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*
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* The value of jiffies is used for a fairly randomly cache tag.
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*/
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static
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int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
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{
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v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
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if (!v9ses->cachetag)
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return -ENOMEM;
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return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
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}
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static uint16_t v9fs_cache_session_get_key(const void *cookie_netfs_data,
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void *buffer, uint16_t bufmax)
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{
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struct v9fs_session_info *v9ses;
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uint16_t klen = 0;
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v9ses = (struct v9fs_session_info *)cookie_netfs_data;
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P9_DPRINTK(P9_DEBUG_FSC, "session %p buf %p size %u", v9ses,
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buffer, bufmax);
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if (v9ses->cachetag)
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klen = strlen(v9ses->cachetag);
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if (klen > bufmax)
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return 0;
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memcpy(buffer, v9ses->cachetag, klen);
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P9_DPRINTK(P9_DEBUG_FSC, "cache session tag %s", v9ses->cachetag);
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return klen;
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}
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const struct fscache_cookie_def v9fs_cache_session_index_def = {
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.name = "9P.session",
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.type = FSCACHE_COOKIE_TYPE_INDEX,
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.get_key = v9fs_cache_session_get_key,
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};
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void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
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{
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/* If no cache session tag was specified, we generate a random one. */
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if (!v9ses->cachetag)
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v9fs_random_cachetag(v9ses);
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v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
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&v9fs_cache_session_index_def,
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v9ses);
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P9_DPRINTK(P9_DEBUG_FSC, "session %p get cookie %p", v9ses,
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v9ses->fscache);
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}
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void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
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{
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P9_DPRINTK(P9_DEBUG_FSC, "session %p put cookie %p", v9ses,
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v9ses->fscache);
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fscache_relinquish_cookie(v9ses->fscache, 0);
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v9ses->fscache = NULL;
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}
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static uint16_t v9fs_cache_inode_get_key(const void *cookie_netfs_data,
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void *buffer, uint16_t bufmax)
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{
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const struct v9fs_cookie *vcookie = cookie_netfs_data;
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memcpy(buffer, &vcookie->qid->path, sizeof(vcookie->qid->path));
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p get key %llu", &vcookie->inode,
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vcookie->qid->path);
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return sizeof(vcookie->qid->path);
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}
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static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
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uint64_t *size)
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{
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const struct v9fs_cookie *vcookie = cookie_netfs_data;
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*size = i_size_read(&vcookie->inode);
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p get attr %llu", &vcookie->inode,
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*size);
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}
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static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
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void *buffer, uint16_t buflen)
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{
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const struct v9fs_cookie *vcookie = cookie_netfs_data;
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memcpy(buffer, &vcookie->qid->version, sizeof(vcookie->qid->version));
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p get aux %u", &vcookie->inode,
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vcookie->qid->version);
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return sizeof(vcookie->qid->version);
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}
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static enum
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fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
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const void *buffer,
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uint16_t buflen)
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{
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const struct v9fs_cookie *vcookie = cookie_netfs_data;
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if (buflen != sizeof(vcookie->qid->version))
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return FSCACHE_CHECKAUX_OBSOLETE;
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if (memcmp(buffer, &vcookie->qid->version,
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sizeof(vcookie->qid->version)))
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return FSCACHE_CHECKAUX_OBSOLETE;
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return FSCACHE_CHECKAUX_OKAY;
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}
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static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
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{
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struct v9fs_cookie *vcookie = cookie_netfs_data;
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struct pagevec pvec;
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pgoff_t first;
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int loop, nr_pages;
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pagevec_init(&pvec, 0);
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first = 0;
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for (;;) {
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nr_pages = pagevec_lookup(&pvec, vcookie->inode.i_mapping,
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first,
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PAGEVEC_SIZE - pagevec_count(&pvec));
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if (!nr_pages)
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break;
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for (loop = 0; loop < nr_pages; loop++)
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ClearPageFsCache(pvec.pages[loop]);
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first = pvec.pages[nr_pages - 1]->index + 1;
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pvec.nr = nr_pages;
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pagevec_release(&pvec);
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cond_resched();
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}
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}
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const struct fscache_cookie_def v9fs_cache_inode_index_def = {
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.name = "9p.inode",
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.type = FSCACHE_COOKIE_TYPE_DATAFILE,
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.get_key = v9fs_cache_inode_get_key,
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.get_attr = v9fs_cache_inode_get_attr,
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.get_aux = v9fs_cache_inode_get_aux,
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.check_aux = v9fs_cache_inode_check_aux,
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.now_uncached = v9fs_cache_inode_now_uncached,
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};
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void v9fs_cache_inode_get_cookie(struct inode *inode)
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{
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struct v9fs_cookie *vcookie;
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struct v9fs_session_info *v9ses;
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if (!S_ISREG(inode->i_mode))
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return;
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vcookie = v9fs_inode2cookie(inode);
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if (vcookie->fscache)
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return;
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v9ses = v9fs_inode2v9ses(inode);
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vcookie->fscache = fscache_acquire_cookie(v9ses->fscache,
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&v9fs_cache_inode_index_def,
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vcookie);
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p get cookie %p", inode,
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vcookie->fscache);
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}
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void v9fs_cache_inode_put_cookie(struct inode *inode)
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{
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struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
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if (!vcookie->fscache)
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return;
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p put cookie %p", inode,
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vcookie->fscache);
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fscache_relinquish_cookie(vcookie->fscache, 0);
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vcookie->fscache = NULL;
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}
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void v9fs_cache_inode_flush_cookie(struct inode *inode)
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{
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struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
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if (!vcookie->fscache)
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return;
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p flush cookie %p", inode,
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vcookie->fscache);
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fscache_relinquish_cookie(vcookie->fscache, 1);
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vcookie->fscache = NULL;
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}
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void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
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{
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struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
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struct p9_fid *fid;
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if (!vcookie->fscache)
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return;
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spin_lock(&vcookie->lock);
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fid = filp->private_data;
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if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
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v9fs_cache_inode_flush_cookie(inode);
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else
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v9fs_cache_inode_get_cookie(inode);
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spin_unlock(&vcookie->lock);
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}
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void v9fs_cache_inode_reset_cookie(struct inode *inode)
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{
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struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
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struct v9fs_session_info *v9ses;
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struct fscache_cookie *old;
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if (!vcookie->fscache)
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return;
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old = vcookie->fscache;
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spin_lock(&vcookie->lock);
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fscache_relinquish_cookie(vcookie->fscache, 1);
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v9ses = v9fs_inode2v9ses(inode);
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vcookie->fscache = fscache_acquire_cookie(v9ses->fscache,
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&v9fs_cache_inode_index_def,
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vcookie);
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P9_DPRINTK(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p",
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inode, old, vcookie->fscache);
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spin_unlock(&vcookie->lock);
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}
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int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
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{
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struct inode *inode = page->mapping->host;
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struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
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BUG_ON(!vcookie->fscache);
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FS-Cache: Handle pages pending storage that get evicted under OOM conditions
Handle netfs pages that the vmscan algorithm wants to evict from the pagecache
under OOM conditions, but that are waiting for write to the cache. Under these
conditions, vmscan calls the releasepage() function of the netfs, asking if a
page can be discarded.
The problem is typified by the following trace of a stuck process:
kslowd005 D 0000000000000000 0 4253 2 0x00000080
ffff88001b14f370 0000000000000046 ffff880020d0d000 0000000000000007
0000000000000006 0000000000000001 ffff88001b14ffd8 ffff880020d0d2a8
000000000000ddf0 00000000000118c0 00000000000118c0 ffff880020d0d2a8
Call Trace:
[<ffffffffa00782d8>] __fscache_wait_on_page_write+0x8b/0xa7 [fscache]
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffffa0078240>] ? __fscache_check_page_write+0x63/0x70 [fscache]
[<ffffffffa00b671d>] nfs_fscache_release_page+0x4e/0xc4 [nfs]
[<ffffffffa00927f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff810885d3>] try_to_release_page+0x32/0x3b
[<ffffffff81093203>] shrink_page_list+0x316/0x4ac
[<ffffffff8109372b>] shrink_inactive_list+0x392/0x67c
[<ffffffff813532fa>] ? __mutex_unlock_slowpath+0x100/0x10b
[<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130
[<ffffffff8135330e>] ? mutex_unlock+0x9/0xb
[<ffffffff81093aa2>] shrink_list+0x8d/0x8f
[<ffffffff81093d1c>] shrink_zone+0x278/0x33c
[<ffffffff81052d6c>] ? ktime_get_ts+0xad/0xba
[<ffffffff81094b13>] try_to_free_pages+0x22e/0x392
[<ffffffff81091e24>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e743>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff81089529>] grab_cache_page_write_begin+0x65/0xaa
[<ffffffff8110f8c0>] ext3_write_begin+0x78/0x1eb
[<ffffffff81089ec5>] generic_file_buffered_write+0x109/0x28c
[<ffffffff8103cb69>] ? current_fs_time+0x22/0x29
[<ffffffff8108a509>] __generic_file_aio_write+0x350/0x385
[<ffffffff8108a588>] ? generic_file_aio_write+0x4a/0xae
[<ffffffff8108a59e>] generic_file_aio_write+0x60/0xae
[<ffffffff810b2e82>] do_sync_write+0xe3/0x120
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810b18e1>] ? __dentry_open+0x1a5/0x2b8
[<ffffffff810b1a76>] ? dentry_open+0x82/0x89
[<ffffffffa00e693c>] cachefiles_write_page+0x298/0x335 [cachefiles]
[<ffffffffa0077147>] fscache_write_op+0x178/0x2c2 [fscache]
[<ffffffffa0075656>] fscache_op_execute+0x7a/0xd1 [fscache]
[<ffffffff81082093>] slow_work_execute+0x18f/0x2d1
[<ffffffff8108239a>] slow_work_thread+0x1c5/0x308
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810821d5>] ? slow_work_thread+0x0/0x308
[<ffffffff8104be91>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8102ef83>] ? tg_shares_up+0x171/0x227
[<ffffffff8104be17>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
In the above backtrace, the following is happening:
(1) A page storage operation is being executed by a slow-work thread
(fscache_write_op()).
(2) FS-Cache farms the operation out to the cache to perform
(cachefiles_write_page()).
(3) CacheFiles is then calling Ext3 to perform the actual write, using Ext3's
standard write (do_sync_write()) under KERNEL_DS directly from the netfs
page.
(4) However, for Ext3 to perform the write, it must allocate some memory, in
particular, it must allocate at least one page cache page into which it
can copy the data from the netfs page.
(5) Under OOM conditions, the memory allocator can't immediately come up with
a page, so it uses vmscan to find something to discard
(try_to_free_pages()).
(6) vmscan finds a clean netfs page it might be able to discard (possibly the
one it's trying to write out).
(7) The netfs is called to throw the page away (nfs_release_page()) - but it's
called with __GFP_WAIT, so the netfs decides to wait for the store to
complete (__fscache_wait_on_page_write()).
(8) This blocks a slow-work processing thread - possibly against itself.
The system ends up stuck because it can't write out any netfs pages to the
cache without allocating more memory.
To avoid this, we make FS-Cache cancel some writes that aren't in the middle of
actually being performed. This means that some data won't make it into the
cache this time. To support this, a new FS-Cache function is added
fscache_maybe_release_page() that replaces what the netfs releasepage()
functions used to do with respect to the cache.
The decisions fscache_maybe_release_page() makes are counted and displayed
through /proc/fs/fscache/stats on a line labelled "VmScan". There are four
counters provided: "nos=N" - pages that weren't pending storage; "gon=N" -
pages that were pending storage when we first looked, but weren't by the time
we got the object lock; "bsy=N" - pages that we ignored as they were actively
being written when we looked; and "can=N" - pages that we cancelled the storage
of.
What I'd really like to do is alter the behaviour of the cancellation
heuristics, depending on how necessary it is to expel pages. If there are
plenty of other pages that aren't waiting to be written to the cache that
could be ejected first, then it would be nice to hold up on immediate
cancellation of cache writes - but I don't see a way of doing that.
Signed-off-by: David Howells <dhowells@redhat.com>
2009-11-19 11:11:35 -07:00
|
|
|
return fscache_maybe_release_page(vnode->cache, page, gfp);
|
2009-09-23 12:00:27 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
void __v9fs_fscache_invalidate_page(struct page *page)
|
|
|
|
{
|
|
|
|
struct inode *inode = page->mapping->host;
|
|
|
|
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
|
|
|
|
|
|
|
|
BUG_ON(!vcookie->fscache);
|
|
|
|
|
|
|
|
if (PageFsCache(page)) {
|
|
|
|
fscache_wait_on_page_write(vcookie->fscache, page);
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
fscache_uncache_page(vcookie->fscache, page);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static void v9fs_vfs_readpage_complete(struct page *page, void *data,
|
|
|
|
int error)
|
|
|
|
{
|
|
|
|
if (!error)
|
|
|
|
SetPageUptodate(page);
|
|
|
|
|
|
|
|
unlock_page(page);
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* __v9fs_readpage_from_fscache - read a page from cache
|
|
|
|
*
|
|
|
|
* Returns 0 if the pages are in cache and a BIO is submitted,
|
|
|
|
* 1 if the pages are not in cache and -error otherwise.
|
|
|
|
*/
|
|
|
|
|
|
|
|
int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
|
|
|
|
{
|
|
|
|
int ret;
|
|
|
|
const struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
|
|
|
|
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "inode %p page %p", inode, page);
|
|
|
|
if (!vcookie->fscache)
|
|
|
|
return -ENOBUFS;
|
|
|
|
|
|
|
|
ret = fscache_read_or_alloc_page(vcookie->fscache,
|
|
|
|
page,
|
|
|
|
v9fs_vfs_readpage_complete,
|
|
|
|
NULL,
|
|
|
|
GFP_KERNEL);
|
|
|
|
switch (ret) {
|
|
|
|
case -ENOBUFS:
|
|
|
|
case -ENODATA:
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "page/inode not in cache %d", ret);
|
|
|
|
return 1;
|
|
|
|
case 0:
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "BIO submitted");
|
|
|
|
return ret;
|
|
|
|
default:
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "ret %d", ret);
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* __v9fs_readpages_from_fscache - read multiple pages from cache
|
|
|
|
*
|
|
|
|
* Returns 0 if the pages are in cache and a BIO is submitted,
|
|
|
|
* 1 if the pages are not in cache and -error otherwise.
|
|
|
|
*/
|
|
|
|
|
|
|
|
int __v9fs_readpages_from_fscache(struct inode *inode,
|
|
|
|
struct address_space *mapping,
|
|
|
|
struct list_head *pages,
|
|
|
|
unsigned *nr_pages)
|
|
|
|
{
|
|
|
|
int ret;
|
|
|
|
const struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
|
|
|
|
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "inode %p pages %u", inode, *nr_pages);
|
|
|
|
if (!vcookie->fscache)
|
|
|
|
return -ENOBUFS;
|
|
|
|
|
|
|
|
ret = fscache_read_or_alloc_pages(vcookie->fscache,
|
|
|
|
mapping, pages, nr_pages,
|
|
|
|
v9fs_vfs_readpage_complete,
|
|
|
|
NULL,
|
|
|
|
mapping_gfp_mask(mapping));
|
|
|
|
switch (ret) {
|
|
|
|
case -ENOBUFS:
|
|
|
|
case -ENODATA:
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "pages/inodes not in cache %d", ret);
|
|
|
|
return 1;
|
|
|
|
case 0:
|
|
|
|
BUG_ON(!list_empty(pages));
|
|
|
|
BUG_ON(*nr_pages != 0);
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "BIO submitted");
|
|
|
|
return ret;
|
|
|
|
default:
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "ret %d", ret);
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* __v9fs_readpage_to_fscache - write a page to the cache
|
|
|
|
*
|
|
|
|
*/
|
|
|
|
|
|
|
|
void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
|
|
|
|
{
|
|
|
|
int ret;
|
|
|
|
const struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
|
|
|
|
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "inode %p page %p", inode, page);
|
|
|
|
ret = fscache_write_page(vcookie->fscache, page, GFP_KERNEL);
|
|
|
|
P9_DPRINTK(P9_DEBUG_FSC, "ret = %d", ret);
|
|
|
|
if (ret != 0)
|
|
|
|
v9fs_uncache_page(inode, page);
|
|
|
|
}
|