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linux/fs/9p/cache.c
David Howells 94d30ae90a FS-Cache: Provide the ability to enable/disable cookies 
Provide the ability to enable and disable fscache cookies.  A disabled cookie
will reject or ignore further requests to:

	Acquire a child cookie
	Invalidate and update backing objects
	Check the consistency of a backing object
	Allocate storage for backing page
	Read backing pages
	Write to backing pages

but still allows:

	Checks/waits on the completion of already in-progress objects
	Uncaching of pages
	Relinquishment of cookies

Two new operations are provided:

 (1) Disable a cookie:

	void fscache_disable_cookie(struct fscache_cookie *cookie,
				    bool invalidate);

     If the cookie is not already disabled, this locks the cookie against other
     dis/enablement ops, marks the cookie as being disabled, discards or
     invalidates any backing objects and waits for cessation of activity on any
     associated object.

     This is a wrapper around a chunk split out of fscache_relinquish_cookie(),
     but it reinitialises the cookie such that it can be reenabled.

     All possible failures are handled internally.  The caller should consider
     calling fscache_uncache_all_inode_pages() afterwards to make sure all page
     markings are cleared up.

 (2) Enable a cookie:

	void fscache_enable_cookie(struct fscache_cookie *cookie,
				   bool (*can_enable)(void *data),
				   void *data)

     If the cookie is not already enabled, this locks the cookie against other
     dis/enablement ops, invokes can_enable() and, if the cookie is not an
     index cookie, will begin the procedure of acquiring backing objects.

     The optional can_enable() function is passed the data argument and returns
     a ruling as to whether or not enablement should actually be permitted to
     begin.

     All possible failures are handled internally.  The cookie will only be
     marked as enabled if provisional backing objects are allocated.

A later patch will introduce these to NFS.  Cookie enablement during nfs_open()
is then contingent on i_writecount <= 0.  can_enable() checks for a race
between open(O_RDONLY) and open(O_WRONLY/O_RDWR).  This simplifies NFS's cookie
handling and allows us to get rid of open(O_RDONLY) accidentally introducing
caching to an inode that's open for writing already.

One operation has its API modified:

 (3) Acquire a cookie.

	struct fscache_cookie *fscache_acquire_cookie(
		struct fscache_cookie *parent,
		const struct fscache_cookie_def *def,
		void *netfs_data,
		bool enable);

     This now has an additional argument that indicates whether the requested
     cookie should be enabled by default.  It doesn't need the can_enable()
     function because the caller must prevent multiple calls for the same netfs
     object and it doesn't need to take the enablement lock because no one else
     can get at the cookie before this returns.

Signed-off-by: David Howells <dhowells@redhat.com
2013-09-27 18:40:25 +01:00

416 lines
10 KiB
C
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/*
* 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/slab.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 fscache_netfs v9fs_cache_netfs = {
.name = "9p",
.version = 0,
};
/**
* 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_debug(P9_DEBUG_FSC, "session %p buf %p size %u\n",
v9ses, buffer, bufmax);
if (v9ses->cachetag)
klen = strlen(v9ses->cachetag);
if (klen > bufmax)
return 0;
memcpy(buffer, v9ses->cachetag, klen);
p9_debug(P9_DEBUG_FSC, "cache session tag %s\n", 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, true);
p9_debug(P9_DEBUG_FSC, "session %p get cookie %p\n",
v9ses, v9ses->fscache);
}
void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
{
p9_debug(P9_DEBUG_FSC, "session %p put cookie %p\n",
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_inode *v9inode = cookie_netfs_data;
memcpy(buffer, &v9inode->qid.path, sizeof(v9inode->qid.path));
p9_debug(P9_DEBUG_FSC, "inode %p get key %llu\n",
&v9inode->vfs_inode, v9inode->qid.path);
return sizeof(v9inode->qid.path);
}
static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
uint64_t *size)
{
const struct v9fs_inode *v9inode = cookie_netfs_data;
*size = i_size_read(&v9inode->vfs_inode);
p9_debug(P9_DEBUG_FSC, "inode %p get attr %llu\n",
&v9inode->vfs_inode, *size);
}
static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
void *buffer, uint16_t buflen)
{
const struct v9fs_inode *v9inode = cookie_netfs_data;
memcpy(buffer, &v9inode->qid.version, sizeof(v9inode->qid.version));
p9_debug(P9_DEBUG_FSC, "inode %p get aux %u\n",
&v9inode->vfs_inode, v9inode->qid.version);
return sizeof(v9inode->qid.version);
}
static enum
fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
const void *buffer,
uint16_t buflen)
{
const struct v9fs_inode *v9inode = cookie_netfs_data;
if (buflen != sizeof(v9inode->qid.version))
return FSCACHE_CHECKAUX_OBSOLETE;
if (memcmp(buffer, &v9inode->qid.version,
sizeof(v9inode->qid.version)))
return FSCACHE_CHECKAUX_OBSOLETE;
return FSCACHE_CHECKAUX_OKAY;
}
static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
{
struct v9fs_inode *v9inode = 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, v9inode->vfs_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_inode *v9inode;
struct v9fs_session_info *v9ses;
if (!S_ISREG(inode->i_mode))
return;
v9inode = V9FS_I(inode);
if (v9inode->fscache)
return;
v9ses = v9fs_inode2v9ses(inode);
v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
&v9fs_cache_inode_index_def,
v9inode, true);
p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
inode, v9inode->fscache);
}
void v9fs_cache_inode_put_cookie(struct inode *inode)
{
struct v9fs_inode *v9inode = V9FS_I(inode);
if (!v9inode->fscache)
return;
p9_debug(P9_DEBUG_FSC, "inode %p put cookie %p\n",
inode, v9inode->fscache);
fscache_relinquish_cookie(v9inode->fscache, 0);
v9inode->fscache = NULL;
}
void v9fs_cache_inode_flush_cookie(struct inode *inode)
{
struct v9fs_inode *v9inode = V9FS_I(inode);
if (!v9inode->fscache)
return;
p9_debug(P9_DEBUG_FSC, "inode %p flush cookie %p\n",
inode, v9inode->fscache);
fscache_relinquish_cookie(v9inode->fscache, 1);
v9inode->fscache = NULL;
}
void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
{
struct v9fs_inode *v9inode = V9FS_I(inode);
struct p9_fid *fid;
if (!v9inode->fscache)
return;
spin_lock(&v9inode->fscache_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(&v9inode->fscache_lock);
}
void v9fs_cache_inode_reset_cookie(struct inode *inode)
{
struct v9fs_inode *v9inode = V9FS_I(inode);
struct v9fs_session_info *v9ses;
struct fscache_cookie *old;
if (!v9inode->fscache)
return;
old = v9inode->fscache;
spin_lock(&v9inode->fscache_lock);
fscache_relinquish_cookie(v9inode->fscache, 1);
v9ses = v9fs_inode2v9ses(inode);
v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
&v9fs_cache_inode_index_def,
v9inode, true);
p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
inode, old, v9inode->fscache);
spin_unlock(&v9inode->fscache_lock);
}
int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
{
struct inode *inode = page->mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
BUG_ON(!v9inode->fscache);
return fscache_maybe_release_page(v9inode->fscache, page, gfp);
}
void __v9fs_fscache_invalidate_page(struct page *page)
{
struct inode *inode = page->mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
BUG_ON(!v9inode->fscache);
if (PageFsCache(page)) {
fscache_wait_on_page_write(v9inode->fscache, page);
BUG_ON(!PageLocked(page));
fscache_uncache_page(v9inode->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_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
if (!v9inode->fscache)
return -ENOBUFS;
ret = fscache_read_or_alloc_page(v9inode->fscache,
page,
v9fs_vfs_readpage_complete,
NULL,
GFP_KERNEL);
switch (ret) {
case -ENOBUFS:
case -ENODATA:
p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
return 1;
case 0:
p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
return ret;
default:
p9_debug(P9_DEBUG_FSC, "ret %d\n", 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_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
if (!v9inode->fscache)
return -ENOBUFS;
ret = fscache_read_or_alloc_pages(v9inode->fscache,
mapping, pages, nr_pages,
v9fs_vfs_readpage_complete,
NULL,
mapping_gfp_mask(mapping));
switch (ret) {
case -ENOBUFS:
case -ENODATA:
p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
return 1;
case 0:
BUG_ON(!list_empty(pages));
BUG_ON(*nr_pages != 0);
p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
return ret;
default:
p9_debug(P9_DEBUG_FSC, "ret %d\n", 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_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
ret = fscache_write_page(v9inode->fscache, page, GFP_KERNEL);
p9_debug(P9_DEBUG_FSC, "ret = %d\n", ret);
if (ret != 0)
v9fs_uncache_page(inode, page);
}
/*
* wait for a page to complete writing to the cache
*/
void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
{
const struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
if (PageFsCache(page))
fscache_wait_on_page_write(v9inode->fscache, page);
}
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