linux/fs/nfs/fscache.c
David Howells 16f2f4e679 nfs: Implement cache I/O by accessing the cache directly
Move NFS 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].

NFS 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].

Changes
=======
ver #3:
 - Restore lost =n fallback for nfs_fscache_release_page()[2].

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Dave Wysochanski <dwysocha@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Anna Schumaker <anna.schumaker@netapp.com>
cc: linux-nfs@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]
Link: https://lore.kernel.org/r/163189108292.2509237.12615909591150927232.stgit@warthog.procyon.org.uk/ [2]
Link: https://lore.kernel.org/r/163906981318.143852.17220018647843475985.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967184451.1823006.6450645559828329590.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021577632.640689.11069627070150063812.stgit@warthog.procyon.org.uk/ # v4
2022-01-10 11:53:25 +00:00

377 lines
10 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* NFS filesystem cache interface
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_fs_sb.h>
#include <linux/in6.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/iversion.h>
#include "internal.h"
#include "iostat.h"
#include "fscache.h"
#define NFSDBG_FACILITY NFSDBG_FSCACHE
#define NFS_MAX_KEY_LEN 1000
static bool nfs_append_int(char *key, int *_len, unsigned long long x)
{
if (*_len > NFS_MAX_KEY_LEN)
return false;
if (x == 0)
key[(*_len)++] = ',';
else
*_len += sprintf(key + *_len, ",%llx", x);
return true;
}
/*
* Get the per-client index cookie for an NFS client if the appropriate mount
* flag was set
* - We always try and get an index cookie for the client, but get filehandle
* cookies on a per-superblock basis, depending on the mount flags
*/
static bool nfs_fscache_get_client_key(struct nfs_client *clp,
char *key, int *_len)
{
const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &clp->cl_addr;
const struct sockaddr_in *sin = (struct sockaddr_in *) &clp->cl_addr;
*_len += snprintf(key + *_len, NFS_MAX_KEY_LEN - *_len,
",%u.%u,%x",
clp->rpc_ops->version,
clp->cl_minorversion,
clp->cl_addr.ss_family);
switch (clp->cl_addr.ss_family) {
case AF_INET:
if (!nfs_append_int(key, _len, sin->sin_port) ||
!nfs_append_int(key, _len, sin->sin_addr.s_addr))
return false;
return true;
case AF_INET6:
if (!nfs_append_int(key, _len, sin6->sin6_port) ||
!nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[0]) ||
!nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[1]) ||
!nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[2]) ||
!nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[3]))
return false;
return true;
default:
printk(KERN_WARNING "NFS: Unknown network family '%d'\n",
clp->cl_addr.ss_family);
return false;
}
}
/*
* Get the cache cookie for an NFS superblock.
*
* The default uniquifier is just an empty string, but it may be overridden
* either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
* superblock across an automount point of some nature.
*/
int nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int ulen)
{
struct fscache_volume *vcookie;
struct nfs_server *nfss = NFS_SB(sb);
unsigned int len = 3;
char *key;
if (uniq) {
nfss->fscache_uniq = kmemdup_nul(uniq, ulen, GFP_KERNEL);
if (!nfss->fscache_uniq)
return -ENOMEM;
}
key = kmalloc(NFS_MAX_KEY_LEN + 24, GFP_KERNEL);
if (!key)
return -ENOMEM;
memcpy(key, "nfs", 3);
if (!nfs_fscache_get_client_key(nfss->nfs_client, key, &len) ||
!nfs_append_int(key, &len, nfss->fsid.major) ||
!nfs_append_int(key, &len, nfss->fsid.minor) ||
!nfs_append_int(key, &len, sb->s_flags & NFS_SB_MASK) ||
!nfs_append_int(key, &len, nfss->flags) ||
!nfs_append_int(key, &len, nfss->rsize) ||
!nfs_append_int(key, &len, nfss->wsize) ||
!nfs_append_int(key, &len, nfss->acregmin) ||
!nfs_append_int(key, &len, nfss->acregmax) ||
!nfs_append_int(key, &len, nfss->acdirmin) ||
!nfs_append_int(key, &len, nfss->acdirmax) ||
!nfs_append_int(key, &len, nfss->client->cl_auth->au_flavor))
goto out;
if (ulen > 0) {
if (ulen > NFS_MAX_KEY_LEN - len)
goto out;
key[len++] = ',';
memcpy(key + len, uniq, ulen);
len += ulen;
}
key[len] = 0;
/* create a cache index for looking up filehandles */
vcookie = fscache_acquire_volume(key,
NULL, /* preferred_cache */
NULL, 0 /* coherency_data */);
dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",
nfss, vcookie);
if (IS_ERR(vcookie)) {
if (vcookie != ERR_PTR(-EBUSY)) {
kfree(key);
return PTR_ERR(vcookie);
}
pr_err("NFS: Cache volume key already in use (%s)\n", key);
vcookie = NULL;
}
nfss->fscache = vcookie;
out:
kfree(key);
return 0;
}
/*
* release a per-superblock cookie
*/
void nfs_fscache_release_super_cookie(struct super_block *sb)
{
struct nfs_server *nfss = NFS_SB(sb);
dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)\n",
nfss, nfss->fscache);
fscache_relinquish_volume(nfss->fscache, NULL, false);
nfss->fscache = NULL;
kfree(nfss->fscache_uniq);
}
/*
* Initialise the per-inode cache cookie pointer for an NFS inode.
*/
void nfs_fscache_init_inode(struct inode *inode)
{
struct nfs_fscache_inode_auxdata auxdata;
struct nfs_server *nfss = NFS_SERVER(inode);
struct nfs_inode *nfsi = NFS_I(inode);
nfsi->fscache = NULL;
if (!(nfss->fscache && S_ISREG(inode->i_mode)))
return;
nfs_fscache_update_auxdata(&auxdata, nfsi);
nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
0,
nfsi->fh.data, /* index_key */
nfsi->fh.size,
&auxdata, /* aux_data */
sizeof(auxdata),
i_size_read(&nfsi->vfs_inode));
}
/*
* Release a per-inode cookie.
*/
void nfs_fscache_clear_inode(struct inode *inode)
{
struct nfs_inode *nfsi = NFS_I(inode);
struct fscache_cookie *cookie = nfs_i_fscache(inode);
dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)\n", nfsi, cookie);
fscache_relinquish_cookie(cookie, false);
nfsi->fscache = NULL;
}
/*
* Enable or disable caching for a file that is being opened as appropriate.
* The cookie is allocated when the inode is initialised, but is not enabled at
* that time. Enablement is deferred to file-open time to avoid stat() and
* access() thrashing the cache.
*
* For now, with NFS, only regular files that are open read-only will be able
* to use the cache.
*
* We enable the cache for an inode if we open it read-only and it isn't
* currently open for writing. We disable the cache if the inode is open
* write-only.
*
* The caller uses the file struct to pin i_writecount on the inode before
* calling us when a file is opened for writing, so we can make use of that.
*
* Note that this may be invoked multiple times in parallel by parallel
* nfs_open() functions.
*/
void nfs_fscache_open_file(struct inode *inode, struct file *filp)
{
struct nfs_fscache_inode_auxdata auxdata;
struct nfs_inode *nfsi = NFS_I(inode);
struct fscache_cookie *cookie = nfs_i_fscache(inode);
bool open_for_write = inode_is_open_for_write(inode);
if (!fscache_cookie_valid(cookie))
return;
fscache_use_cookie(cookie, open_for_write);
if (open_for_write) {
dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache\n", nfsi);
nfs_fscache_update_auxdata(&auxdata, nfsi);
fscache_invalidate(cookie, &auxdata, i_size_read(inode),
FSCACHE_INVAL_DIO_WRITE);
}
}
EXPORT_SYMBOL_GPL(nfs_fscache_open_file);
void nfs_fscache_release_file(struct inode *inode, struct file *filp)
{
struct nfs_fscache_inode_auxdata auxdata;
struct nfs_inode *nfsi = NFS_I(inode);
struct fscache_cookie *cookie = nfs_i_fscache(inode);
if (fscache_cookie_valid(cookie)) {
nfs_fscache_update_auxdata(&auxdata, nfsi);
fscache_unuse_cookie(cookie, &auxdata, 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 = nfs_i_fscache(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 = nfs_i_fscache(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 fscache
*/
int __nfs_readpage_from_fscache(struct inode *inode, struct page *page)
{
int ret;
dfprintk(FSCACHE,
"NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
nfs_i_fscache(inode), page, page->index, page->flags, inode);
if (PageChecked(page)) {
dfprintk(FSCACHE, "NFS: readpage_from_fscache: PageChecked\n");
ClearPageChecked(page);
return 1;
}
ret = fscache_fallback_read_page(inode, page);
if (ret < 0) {
nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL);
dfprintk(FSCACHE,
"NFS: readpage_from_fscache failed %d\n", ret);
SetPageChecked(page);
return ret;
}
/* Read completed synchronously */
dfprintk(FSCACHE, "NFS: readpage_from_fscache: read successful\n");
nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK);
SetPageUptodate(page);
return 0;
}
/*
* Store a newly fetched page in fscache. We can be certain there's no page
* stored in the cache as yet otherwise we would've read it from there.
*/
void __nfs_readpage_to_fscache(struct inode *inode, struct page *page)
{
int ret;
dfprintk(FSCACHE,
"NFS: readpage_to_fscache(fsc:%p/p:%p(i:%lx f:%lx))\n",
nfs_i_fscache(inode), page, page->index, page->flags);
ret = fscache_fallback_write_page(inode, page, true);
dfprintk(FSCACHE,
"NFS: readpage_to_fscache: p:%p(i:%lu f:%lx) ret %d\n",
page, page->index, page->flags, ret);
if (ret != 0) {
nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL);
nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED);
} else {
nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_WRITTEN_OK);
}
}