Commit 60e78d2c authored by Abhishek Kulkarni's avatar Abhishek Kulkarni Committed by Eric Van Hensbergen
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9p: Add fscache support to 9p



This patch adds a persistent, read-only caching facility for
9p clients using the FS-Cache caching backend.

When the fscache facility is enabled, each inode is associated
with a corresponding vcookie which is an index into the FS-Cache
indexing tree. The FS-Cache indexing tree is indexed at 3 levels:
- session object associated with each mount.
- inode/vcookie
- actual data (pages)

A cache tag is chosen randomly for each session. These tags can
be read off /sys/fs/9p/caches and can be passed as a mount-time
parameter to re-attach to the specified caching session.
Signed-off-by: default avatarAbhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>
parent 637d020a
......@@ -8,3 +8,12 @@ config 9P_FS
See <http://v9fs.sf.net> for more information.
If unsure, say N.
config 9P_FSCACHE
bool "Enable 9P client caching support (EXPERIMENTAL)"
depends on EXPERIMENTAL
depends on 9P_FS=m && FSCACHE || 9P_FS=y && FSCACHE=y
help
Choose Y here to enable persistent, read-only local
caching support for 9p clients using FS-Cache
......@@ -8,5 +8,6 @@ obj-$(CONFIG_9P_FS) := 9p.o
vfs_dir.o \
vfs_dentry.o \
v9fs.o \
fid.o \
fid.o
9p-$(CONFIG_9P_FSCACHE) += cache.o
/*
* V9FS cache definitions.
*
* Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to:
* Free Software Foundation
* 51 Franklin Street, Fifth Floor
* Boston, MA 02111-1301 USA
*
*/
#include <linux/jiffies.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <net/9p/9p.h>
#include "v9fs.h"
#include "cache.h"
#define CACHETAG_LEN 11
struct kmem_cache *vcookie_cache;
struct fscache_netfs v9fs_cache_netfs = {
.name = "9p",
.version = 0,
};
static void init_once(void *foo)
{
struct v9fs_cookie *vcookie = (struct v9fs_cookie *) foo;
vcookie->fscache = NULL;
vcookie->qid = NULL;
inode_init_once(&vcookie->inode);
}
/**
* v9fs_init_vcookiecache - initialize a cache for vcookies to maintain
* vcookie to inode mapping
*
* Returns 0 on success.
*/
static int v9fs_init_vcookiecache(void)
{
vcookie_cache = kmem_cache_create("vcookie_cache",
sizeof(struct v9fs_cookie),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD),
init_once);
if (!vcookie_cache)
return -ENOMEM;
return 0;
}
/**
* v9fs_destroy_vcookiecache - destroy the cache of vcookies
*
*/
static void v9fs_destroy_vcookiecache(void)
{
kmem_cache_destroy(vcookie_cache);
}
int __v9fs_cache_register(void)
{
int ret;
ret = v9fs_init_vcookiecache();
if (ret < 0)
return ret;
return fscache_register_netfs(&v9fs_cache_netfs);
}
void __v9fs_cache_unregister(void)
{
v9fs_destroy_vcookiecache();
fscache_unregister_netfs(&v9fs_cache_netfs);
}
/**
* v9fs_random_cachetag - Generate a random tag to be associated
* with a new cache session.
*
* The value of jiffies is used for a fairly randomly cache tag.
*/
static
int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
{
v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
if (!v9ses->cachetag)
return -ENOMEM;
return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
}
static uint16_t v9fs_cache_session_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
struct v9fs_session_info *v9ses;
uint16_t klen = 0;
v9ses = (struct v9fs_session_info *)cookie_netfs_data;
P9_DPRINTK(P9_DEBUG_FSC, "session %p buf %p size %u", v9ses,
buffer, bufmax);
if (v9ses->cachetag)
klen = strlen(v9ses->cachetag);
if (klen > bufmax)
return 0;
memcpy(buffer, v9ses->cachetag, klen);
P9_DPRINTK(P9_DEBUG_FSC, "cache session tag %s", v9ses->cachetag);
return klen;
}
const struct fscache_cookie_def v9fs_cache_session_index_def = {
.name = "9P.session",
.type = FSCACHE_COOKIE_TYPE_INDEX,
.get_key = v9fs_cache_session_get_key,
};
void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
{
/* If no cache session tag was specified, we generate a random one. */
if (!v9ses->cachetag)
v9fs_random_cachetag(v9ses);
v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
&v9fs_cache_session_index_def,
v9ses);
P9_DPRINTK(P9_DEBUG_FSC, "session %p get cookie %p", v9ses,
v9ses->fscache);
}
void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
{
P9_DPRINTK(P9_DEBUG_FSC, "session %p put cookie %p", v9ses,
v9ses->fscache);
fscache_relinquish_cookie(v9ses->fscache, 0);
v9ses->fscache = NULL;
}
static uint16_t v9fs_cache_inode_get_key(const void *cookie_netfs_data,
void *buffer, uint16_t bufmax)
{
const struct v9fs_cookie *vcookie = cookie_netfs_data;
memcpy(buffer, &vcookie->qid->path, sizeof(vcookie->qid->path));
P9_DPRINTK(P9_DEBUG_FSC, "inode %p get key %llu", &vcookie->inode,
vcookie->qid->path);
return sizeof(vcookie->qid->path);
}
static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
uint64_t *size)
{
const struct v9fs_cookie *vcookie = cookie_netfs_data;
*size = i_size_read(&vcookie->inode);
P9_DPRINTK(P9_DEBUG_FSC, "inode %p get attr %llu", &vcookie->inode,
*size);
}
static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
void *buffer, uint16_t buflen)
{
const struct v9fs_cookie *vcookie = cookie_netfs_data;
memcpy(buffer, &vcookie->qid->version, sizeof(vcookie->qid->version));
P9_DPRINTK(P9_DEBUG_FSC, "inode %p get aux %u", &vcookie->inode,
vcookie->qid->version);
return sizeof(vcookie->qid->version);
}
static enum
fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
const void *buffer,
uint16_t buflen)
{
const struct v9fs_cookie *vcookie = cookie_netfs_data;
if (buflen != sizeof(vcookie->qid->version))
return FSCACHE_CHECKAUX_OBSOLETE;
if (memcmp(buffer, &vcookie->qid->version,
sizeof(vcookie->qid->version)))
return FSCACHE_CHECKAUX_OBSOLETE;
return FSCACHE_CHECKAUX_OKAY;
}
static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
{
struct v9fs_cookie *vcookie = cookie_netfs_data;
struct pagevec pvec;
pgoff_t first;
int loop, nr_pages;
pagevec_init(&pvec, 0);
first = 0;
for (;;) {
nr_pages = pagevec_lookup(&pvec, vcookie->inode.i_mapping,
first,
PAGEVEC_SIZE - pagevec_count(&pvec));
if (!nr_pages)
break;
for (loop = 0; loop < nr_pages; loop++)
ClearPageFsCache(pvec.pages[loop]);
first = pvec.pages[nr_pages - 1]->index + 1;
pvec.nr = nr_pages;
pagevec_release(&pvec);
cond_resched();
}
}
const struct fscache_cookie_def v9fs_cache_inode_index_def = {
.name = "9p.inode",
.type = FSCACHE_COOKIE_TYPE_DATAFILE,
.get_key = v9fs_cache_inode_get_key,
.get_attr = v9fs_cache_inode_get_attr,
.get_aux = v9fs_cache_inode_get_aux,
.check_aux = v9fs_cache_inode_check_aux,
.now_uncached = v9fs_cache_inode_now_uncached,
};
void v9fs_cache_inode_get_cookie(struct inode *inode)
{
struct v9fs_cookie *vcookie;
struct v9fs_session_info *v9ses;
if (!S_ISREG(inode->i_mode))
return;
vcookie = v9fs_inode2cookie(inode);
if (vcookie->fscache)
return;
v9ses = v9fs_inode2v9ses(inode);
vcookie->fscache = fscache_acquire_cookie(v9ses->fscache,
&v9fs_cache_inode_index_def,
vcookie);
P9_DPRINTK(P9_DEBUG_FSC, "inode %p get cookie %p", inode,
vcookie->fscache);
}
void v9fs_cache_inode_put_cookie(struct inode *inode)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
if (!vcookie->fscache)
return;
P9_DPRINTK(P9_DEBUG_FSC, "inode %p put cookie %p", inode,
vcookie->fscache);
fscache_relinquish_cookie(vcookie->fscache, 0);
vcookie->fscache = NULL;
}
void v9fs_cache_inode_flush_cookie(struct inode *inode)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
if (!vcookie->fscache)
return;
P9_DPRINTK(P9_DEBUG_FSC, "inode %p flush cookie %p", inode,
vcookie->fscache);
fscache_relinquish_cookie(vcookie->fscache, 1);
vcookie->fscache = NULL;
}
void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
struct p9_fid *fid;
if (!vcookie->fscache)
return;
spin_lock(&vcookie->lock);
fid = filp->private_data;
if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
v9fs_cache_inode_flush_cookie(inode);
else
v9fs_cache_inode_get_cookie(inode);
spin_unlock(&vcookie->lock);
}
void v9fs_cache_inode_reset_cookie(struct inode *inode)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
struct v9fs_session_info *v9ses;
struct fscache_cookie *old;
if (!vcookie->fscache)
return;
old = vcookie->fscache;
spin_lock(&vcookie->lock);
fscache_relinquish_cookie(vcookie->fscache, 1);
v9ses = v9fs_inode2v9ses(inode);
vcookie->fscache = fscache_acquire_cookie(v9ses->fscache,
&v9fs_cache_inode_index_def,
vcookie);
P9_DPRINTK(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p",
inode, old, vcookie->fscache);
spin_unlock(&vcookie->lock);
}
int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
{
struct inode *inode = page->mapping->host;
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
BUG_ON(!vcookie->fscache);
if (PageFsCache(page)) {
if (fscache_check_page_write(vcookie->fscache, page)) {
if (!(gfp & __GFP_WAIT))
return 0;
fscache_wait_on_page_write(vcookie->fscache, page);
}
fscache_uncache_page(vcookie->fscache, page);
ClearPageFsCache(page);
}
return 1;
}
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);
ClearPageFsCache(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);
}
/*
* V9FS cache definitions.
*
* Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to:
* Free Software Foundation
* 51 Franklin Street, Fifth Floor
* Boston, MA 02111-1301 USA
*
*/
#ifndef _9P_CACHE_H
#ifdef CONFIG_9P_FSCACHE
#include <linux/fscache.h>
#include <linux/spinlock.h>
extern struct kmem_cache *vcookie_cache;
struct v9fs_cookie {
spinlock_t lock;
struct inode inode;
struct fscache_cookie *fscache;
struct p9_qid *qid;
};
static inline struct v9fs_cookie *v9fs_inode2cookie(const struct inode *inode)
{
return container_of(inode, struct v9fs_cookie, inode);
}
extern struct fscache_netfs v9fs_cache_netfs;
extern const struct fscache_cookie_def v9fs_cache_session_index_def;
extern const struct fscache_cookie_def v9fs_cache_inode_index_def;
extern void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses);
extern void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses);
extern void v9fs_cache_inode_get_cookie(struct inode *inode);
extern void v9fs_cache_inode_put_cookie(struct inode *inode);
extern void v9fs_cache_inode_flush_cookie(struct inode *inode);
extern void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp);
extern void v9fs_cache_inode_reset_cookie(struct inode *inode);
extern int __v9fs_cache_register(void);
extern void __v9fs_cache_unregister(void);
extern int __v9fs_fscache_release_page(struct page *page, gfp_t gfp);
extern void __v9fs_fscache_invalidate_page(struct page *page);
extern int __v9fs_readpage_from_fscache(struct inode *inode,
struct page *page);
extern int __v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages);
extern void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page);
/**
* v9fs_cache_register - Register v9fs file system with the cache
*/
static inline int v9fs_cache_register(void)
{
return __v9fs_cache_register();
}
/**
* v9fs_cache_unregister - Unregister v9fs from the cache
*/
static inline void v9fs_cache_unregister(void)
{
__v9fs_cache_unregister();
}
static inline int v9fs_fscache_release_page(struct page *page,
gfp_t gfp)
{
return __v9fs_fscache_release_page(page, gfp);
}
static inline void v9fs_fscache_invalidate_page(struct page *page)
{
__v9fs_fscache_invalidate_page(page);
}
static inline int v9fs_readpage_from_fscache(struct inode *inode,
struct page *page)
{
return __v9fs_readpage_from_fscache(inode, page);
}
static inline int v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages)
{
return __v9fs_readpages_from_fscache(inode, mapping, pages,
nr_pages);
}
static inline void v9fs_readpage_to_fscache(struct inode *inode,
struct page *page)
{
if (PageFsCache(page))
__v9fs_readpage_to_fscache(inode, page);
}
static inline void v9fs_uncache_page(struct inode *inode, struct page *page)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
fscache_uncache_page(vcookie->fscache, page);
BUG_ON(PageFsCache(page));
}
static inline void v9fs_vcookie_set_qid(struct inode *inode,
struct p9_qid *qid)
{
struct v9fs_cookie *vcookie = v9fs_inode2cookie(inode);
spin_lock(&vcookie->lock);
vcookie->qid = qid;
spin_unlock(&vcookie->lock);
}
#else /* CONFIG_9P_FSCACHE */