linux/fs/cifs/fscache.c
David Howells 0174ee9947 cifs: Implement cache I/O by accessing the cache directly
Move cifs to using fscache DIO API instead of the old upstream I/O API as
that has been removed.  This is a stopgap solution as the intention is that
at sometime in the future, the cache will move to using larger blocks and
won't be able to store individual pages in order to deal with the potential
for data corruption due to the backing filesystem being able insert/remove
bridging blocks of zeros into its extent list[1].

cifs then reads and writes cache pages synchronously and one page at a time.

The preferred change would be to use the netfs lib, but the new I/O API can
be used directly.  It's just that as the cache now needs to track data for
itself, caching blocks may exceed page size...

This code is somewhat borrowed from my "fallback I/O" patchset[2].

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <smfrench@gmail.com>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: linux-cifs@vger.kernel.org
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/YO17ZNOcq+9PajfQ@mit.edu [1]
Link: https://lore.kernel.org/r/202112100957.2oEDT20W-lkp@intel.com/ [2]
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
2022-02-01 10:29:18 -06:00

261 lines
6.4 KiB
C

// SPDX-License-Identifier: LGPL-2.1
/*
* CIFS filesystem cache interface
*
* Copyright (c) 2010 Novell, Inc.
* Author(s): Suresh Jayaraman <sjayaraman@suse.de>
*
*/
#include "fscache.h"
#include "cifsglob.h"
#include "cifs_debug.h"
#include "cifs_fs_sb.h"
#include "cifsproto.h"
static void cifs_fscache_fill_volume_coherency(
struct cifs_tcon *tcon,
struct cifs_fscache_volume_coherency_data *cd)
{
memset(cd, 0, sizeof(*cd));
cd->resource_id = cpu_to_le64(tcon->resource_id);
cd->vol_create_time = tcon->vol_create_time;
cd->vol_serial_number = cpu_to_le32(tcon->vol_serial_number);
}
int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
{
struct cifs_fscache_volume_coherency_data cd;
struct TCP_Server_Info *server = tcon->ses->server;
struct fscache_volume *vcookie;
const struct sockaddr *sa = (struct sockaddr *)&server->dstaddr;
size_t slen, i;
char *sharename;
char *key;
int ret = -ENOMEM;
tcon->fscache = NULL;
switch (sa->sa_family) {
case AF_INET:
case AF_INET6:
break;
default:
cifs_dbg(VFS, "Unknown network family '%d'\n", sa->sa_family);
return -EINVAL;
}
memset(&key, 0, sizeof(key));
sharename = extract_sharename(tcon->treeName);
if (IS_ERR(sharename)) {
cifs_dbg(FYI, "%s: couldn't extract sharename\n", __func__);
return -EINVAL;
}
slen = strlen(sharename);
for (i = 0; i < slen; i++)
if (sharename[i] == '/')
sharename[i] = ';';
key = kasprintf(GFP_KERNEL, "cifs,%pISpc,%s", sa, sharename);
if (!key)
goto out;
cifs_fscache_fill_volume_coherency(tcon, &cd);
vcookie = fscache_acquire_volume(key,
NULL, /* preferred_cache */
&cd, sizeof(cd));
cifs_dbg(FYI, "%s: (%s/0x%p)\n", __func__, key, vcookie);
if (IS_ERR(vcookie)) {
if (vcookie != ERR_PTR(-EBUSY)) {
ret = PTR_ERR(vcookie);
goto out_2;
}
pr_err("Cache volume key already in use (%s)\n", key);
vcookie = NULL;
}
tcon->fscache = vcookie;
ret = 0;
out_2:
kfree(key);
out:
kfree(sharename);
return ret;
}
void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon)
{
struct cifs_fscache_volume_coherency_data cd;
cifs_dbg(FYI, "%s: (0x%p)\n", __func__, tcon->fscache);
cifs_fscache_fill_volume_coherency(tcon, &cd);
fscache_relinquish_volume(tcon->fscache, &cd, false);
tcon->fscache = NULL;
}
void cifs_fscache_get_inode_cookie(struct inode *inode)
{
struct cifs_fscache_inode_coherency_data cd;
struct cifsInodeInfo *cifsi = CIFS_I(inode);
struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
cifs_fscache_fill_coherency(&cifsi->vfs_inode, &cd);
cifsi->fscache =
fscache_acquire_cookie(tcon->fscache, 0,
&cifsi->uniqueid, sizeof(cifsi->uniqueid),
&cd, sizeof(cd),
i_size_read(&cifsi->vfs_inode));
}
void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update)
{
if (update) {
struct cifs_fscache_inode_coherency_data cd;
loff_t i_size = i_size_read(inode);
cifs_fscache_fill_coherency(inode, &cd);
fscache_unuse_cookie(cifs_inode_cookie(inode), &cd, &i_size);
} else {
fscache_unuse_cookie(cifs_inode_cookie(inode), NULL, NULL);
}
}
void cifs_fscache_release_inode_cookie(struct inode *inode)
{
struct cifsInodeInfo *cifsi = CIFS_I(inode);
if (cifsi->fscache) {
cifs_dbg(FYI, "%s: (0x%p)\n", __func__, cifsi->fscache);
fscache_relinquish_cookie(cifsi->fscache, false);
cifsi->fscache = NULL;
}
}
static inline void fscache_end_operation(struct netfs_cache_resources *cres)
{
const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
if (ops)
ops->end_operation(cres);
}
/*
* Fallback page reading interface.
*/
static int fscache_fallback_read_page(struct inode *inode, struct page *page)
{
struct netfs_cache_resources cres;
struct fscache_cookie *cookie = cifs_inode_cookie(inode);
struct iov_iter iter;
struct bio_vec bvec[1];
int ret;
memset(&cres, 0, sizeof(cres));
bvec[0].bv_page = page;
bvec[0].bv_offset = 0;
bvec[0].bv_len = PAGE_SIZE;
iov_iter_bvec(&iter, READ, bvec, ARRAY_SIZE(bvec), PAGE_SIZE);
ret = fscache_begin_read_operation(&cres, cookie);
if (ret < 0)
return ret;
ret = fscache_read(&cres, page_offset(page), &iter, NETFS_READ_HOLE_FAIL,
NULL, NULL);
fscache_end_operation(&cres);
return ret;
}
/*
* Fallback page writing interface.
*/
static int fscache_fallback_write_page(struct inode *inode, struct page *page,
bool no_space_allocated_yet)
{
struct netfs_cache_resources cres;
struct fscache_cookie *cookie = cifs_inode_cookie(inode);
struct iov_iter iter;
struct bio_vec bvec[1];
loff_t start = page_offset(page);
size_t len = PAGE_SIZE;
int ret;
memset(&cres, 0, sizeof(cres));
bvec[0].bv_page = page;
bvec[0].bv_offset = 0;
bvec[0].bv_len = PAGE_SIZE;
iov_iter_bvec(&iter, WRITE, bvec, ARRAY_SIZE(bvec), PAGE_SIZE);
ret = fscache_begin_write_operation(&cres, cookie);
if (ret < 0)
return ret;
ret = cres.ops->prepare_write(&cres, &start, &len, i_size_read(inode),
no_space_allocated_yet);
if (ret == 0)
ret = fscache_write(&cres, page_offset(page), &iter, NULL, NULL);
fscache_end_operation(&cres);
return ret;
}
/*
* Retrieve a page from FS-Cache
*/
int __cifs_readpage_from_fscache(struct inode *inode, struct page *page)
{
int ret;
cifs_dbg(FYI, "%s: (fsc:%p, p:%p, i:0x%p\n",
__func__, cifs_inode_cookie(inode), page, inode);
ret = fscache_fallback_read_page(inode, page);
if (ret < 0)
return ret;
/* Read completed synchronously */
SetPageUptodate(page);
return 0;
}
void __cifs_readpage_to_fscache(struct inode *inode, struct page *page)
{
cifs_dbg(FYI, "%s: (fsc: %p, p: %p, i: %p)\n",
__func__, cifs_inode_cookie(inode), page, inode);
fscache_fallback_write_page(inode, page, true);
}
/*
* Query the cache occupancy.
*/
int __cifs_fscache_query_occupancy(struct inode *inode,
pgoff_t first, unsigned int nr_pages,
pgoff_t *_data_first,
unsigned int *_data_nr_pages)
{
struct netfs_cache_resources cres;
struct fscache_cookie *cookie = cifs_inode_cookie(inode);
loff_t start, data_start;
size_t len, data_len;
int ret;
ret = fscache_begin_read_operation(&cres, cookie);
if (ret < 0)
return ret;
start = first * PAGE_SIZE;
len = nr_pages * PAGE_SIZE;
ret = cres.ops->query_occupancy(&cres, start, len, PAGE_SIZE,
&data_start, &data_len);
if (ret == 0) {
*_data_first = data_start / PAGE_SIZE;
*_data_nr_pages = len / PAGE_SIZE;
}
fscache_end_operation(&cres);
return ret;
}