linux/fs/nfs/fscache.c
David Howells b4fa966f03 mm, netfs, fscache: stop read optimisation when folio removed from pagecache
Fscache has an optimisation by which reads from the cache are skipped
until we know that (a) there's data there to be read and (b) that data
isn't entirely covered by pages resident in the netfs pagecache.  This is
done with two flags manipulated by fscache_note_page_release():

	if (...
	    test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) &&
	    test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags))
		clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);

where the NO_DATA_TO_READ flag causes cachefiles_prepare_read() to
indicate that netfslib should download from the server or clear the page
instead.

The fscache_note_page_release() function is intended to be called from
->releasepage() - but that only gets called if PG_private or PG_private_2
is set - and currently the former is at the discretion of the network
filesystem and the latter is only set whilst a page is being written to
the cache, so sometimes we miss clearing the optimisation.

Fix this by following Willy's suggestion[1] and adding an address_space
flag, AS_RELEASE_ALWAYS, that causes filemap_release_folio() to always call
->release_folio() if it's set, even if PG_private or PG_private_2 aren't
set.

Note that this would require folio_test_private() and page_has_private() to
become more complicated.  To avoid that, in the places[*] where these are
used to conditionalise calls to filemap_release_folio() and
try_to_release_page(), the tests are removed the those functions just
jumped to unconditionally and the test is performed there.

[*] There are some exceptions in vmscan.c where the check guards more than
just a call to the releaser.  I've added a function, folio_needs_release()
to wrap all the checks for that.

AS_RELEASE_ALWAYS should be set if a non-NULL cookie is obtained from
fscache and cleared in ->evict_inode() before truncate_inode_pages_final()
is called.

Additionally, the FSCACHE_COOKIE_NO_DATA_TO_READ flag needs to be cleared
and the optimisation cancelled if a cachefiles object already contains data
when we open it.

[dwysocha@redhat.com: call folio_mapping() inside folio_needs_release()]
  Link: 902c990e31
Link: https://lkml.kernel.org/r/20230628104852.3391651-3-dhowells@redhat.com
Fixes: 1f67e6d0b1 ("fscache: Provide a function to note the release of a page")
Fixes: 047487c947 ("cachefiles: Implement the I/O routines")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Reported-by: Rohith Surabattula <rohiths.msft@gmail.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Tested-by: SeongJae Park <sj@kernel.org>
Cc: Daire Byrne <daire.byrne@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steve French <sfrench@samba.org>
Cc: Shyam Prasad N <nspmangalore@gmail.com>
Cc: Rohith Surabattula <rohiths.msft@gmail.com>
Cc: Dave Wysochanski <dwysocha@redhat.com>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jingbo Xu <jefflexu@linux.alibaba.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-08-18 10:12:13 -07:00

394 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 <linux/xarray.h>
#include <linux/fscache.h>
#include <linux/netfs.h>
#include "internal.h"
#include "iostat.h"
#include "fscache.h"
#include "nfstrace.h"
#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 */);
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);
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);
netfs_inode(inode)->cache = NULL;
if (!(nfss->fscache && S_ISREG(inode->i_mode)))
return;
nfs_fscache_update_auxdata(&auxdata, inode);
netfs_inode(inode)->cache = fscache_acquire_cookie(
nfss->fscache,
0,
nfsi->fh.data, /* index_key */
nfsi->fh.size,
&auxdata, /* aux_data */
sizeof(auxdata),
i_size_read(inode));
if (netfs_inode(inode)->cache)
mapping_set_release_always(inode->i_mapping);
}
/*
* Release a per-inode cookie.
*/
void nfs_fscache_clear_inode(struct inode *inode)
{
fscache_relinquish_cookie(netfs_i_cookie(netfs_inode(inode)), false);
netfs_inode(inode)->cache = 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 fscache_cookie *cookie = netfs_i_cookie(netfs_inode(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) {
nfs_fscache_update_auxdata(&auxdata, inode);
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 fscache_cookie *cookie = netfs_i_cookie(netfs_inode(inode));
loff_t i_size = i_size_read(inode);
nfs_fscache_update_auxdata(&auxdata, inode);
fscache_unuse_cookie(cookie, &auxdata, &i_size);
}
int nfs_netfs_read_folio(struct file *file, struct folio *folio)
{
if (!netfs_inode(folio_inode(folio))->cache)
return -ENOBUFS;
return netfs_read_folio(file, folio);
}
int nfs_netfs_readahead(struct readahead_control *ractl)
{
struct inode *inode = ractl->mapping->host;
if (!netfs_inode(inode)->cache)
return -ENOBUFS;
netfs_readahead(ractl);
return 0;
}
static atomic_t nfs_netfs_debug_id;
static int nfs_netfs_init_request(struct netfs_io_request *rreq, struct file *file)
{
rreq->netfs_priv = get_nfs_open_context(nfs_file_open_context(file));
rreq->debug_id = atomic_inc_return(&nfs_netfs_debug_id);
return 0;
}
static void nfs_netfs_free_request(struct netfs_io_request *rreq)
{
put_nfs_open_context(rreq->netfs_priv);
}
static inline int nfs_netfs_begin_cache_operation(struct netfs_io_request *rreq)
{
return fscache_begin_read_operation(&rreq->cache_resources,
netfs_i_cookie(netfs_inode(rreq->inode)));
}
static struct nfs_netfs_io_data *nfs_netfs_alloc(struct netfs_io_subrequest *sreq)
{
struct nfs_netfs_io_data *netfs;
netfs = kzalloc(sizeof(*netfs), GFP_KERNEL_ACCOUNT);
if (!netfs)
return NULL;
netfs->sreq = sreq;
refcount_set(&netfs->refcount, 1);
return netfs;
}
static bool nfs_netfs_clamp_length(struct netfs_io_subrequest *sreq)
{
size_t rsize = NFS_SB(sreq->rreq->inode->i_sb)->rsize;
sreq->len = min(sreq->len, rsize);
return true;
}
static void nfs_netfs_issue_read(struct netfs_io_subrequest *sreq)
{
struct nfs_netfs_io_data *netfs;
struct nfs_pageio_descriptor pgio;
struct inode *inode = sreq->rreq->inode;
struct nfs_open_context *ctx = sreq->rreq->netfs_priv;
struct page *page;
int err;
pgoff_t start = (sreq->start + sreq->transferred) >> PAGE_SHIFT;
pgoff_t last = ((sreq->start + sreq->len -
sreq->transferred - 1) >> PAGE_SHIFT);
XA_STATE(xas, &sreq->rreq->mapping->i_pages, start);
nfs_pageio_init_read(&pgio, inode, false,
&nfs_async_read_completion_ops);
netfs = nfs_netfs_alloc(sreq);
if (!netfs)
return netfs_subreq_terminated(sreq, -ENOMEM, false);
pgio.pg_netfs = netfs; /* used in completion */
xas_lock(&xas);
xas_for_each(&xas, page, last) {
/* nfs_read_add_folio() may schedule() due to pNFS layout and other RPCs */
xas_pause(&xas);
xas_unlock(&xas);
err = nfs_read_add_folio(&pgio, ctx, page_folio(page));
if (err < 0) {
netfs->error = err;
goto out;
}
xas_lock(&xas);
}
xas_unlock(&xas);
out:
nfs_pageio_complete_read(&pgio);
nfs_netfs_put(netfs);
}
void nfs_netfs_initiate_read(struct nfs_pgio_header *hdr)
{
struct nfs_netfs_io_data *netfs = hdr->netfs;
if (!netfs)
return;
nfs_netfs_get(netfs);
}
int nfs_netfs_folio_unlock(struct folio *folio)
{
struct inode *inode = folio_file_mapping(folio)->host;
/*
* If fscache is enabled, netfs will unlock pages.
*/
if (netfs_inode(inode)->cache)
return 0;
return 1;
}
void nfs_netfs_read_completion(struct nfs_pgio_header *hdr)
{
struct nfs_netfs_io_data *netfs = hdr->netfs;
struct netfs_io_subrequest *sreq;
if (!netfs)
return;
sreq = netfs->sreq;
if (test_bit(NFS_IOHDR_EOF, &hdr->flags))
__set_bit(NETFS_SREQ_CLEAR_TAIL, &sreq->flags);
if (hdr->error)
netfs->error = hdr->error;
else
atomic64_add(hdr->res.count, &netfs->transferred);
nfs_netfs_put(netfs);
hdr->netfs = NULL;
}
const struct netfs_request_ops nfs_netfs_ops = {
.init_request = nfs_netfs_init_request,
.free_request = nfs_netfs_free_request,
.begin_cache_operation = nfs_netfs_begin_cache_operation,
.issue_read = nfs_netfs_issue_read,
.clamp_length = nfs_netfs_clamp_length
};