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linux/fs/nfs/fscache.h
David Howells 2ff1e97587 netfs: Replace PG_fscache by setting folio->private and marking dirty 
When dirty data is being written to the cache, setting/waiting on/clearing
the fscache flag is always done in tandem with setting/waiting on/clearing
the writeback flag.  The netfslib buffered write routines wait on and set
both flags and the write request cleanup clears both flags, so the fscache
flag is almost superfluous.

The reason it isn't superfluous is because the fscache flag is also used to
indicate that data just read from the server is being written to the cache.
The flag is used to prevent a race involving overlapping direct-I/O writes
to the cache.

Change this to indicate that a page is in need of being copied to the cache
by placing a magic value in folio->private and marking the folios dirty.
Then when the writeback code sees a folio marked in this way, it only
writes it to the cache and not to the server.

If a folio that has this magic value set is modified, the value is just
replaced and the folio will then be uplodaded too.

With this, PG_fscache is no longer required by the netfslib core, 9p and
afs.

Ceph and nfs, however, still need to use the old PG_fscache-based tracking.
To deal with this, a flag, NETFS_ICTX_USE_PGPRIV2, now has to be set on the
flags in the netfs_inode struct for those filesystems.  This reenables the
use of PG_fscache in that inode.  9p and afs use the netfslib write helpers
so get switched over; cifs, for the moment, does page-by-page manual access
to the cache, so doesn't use PG_fscache and is unaffected.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Eric Van Hensbergen <ericvh@kernel.org>
cc: Latchesar Ionkov <lucho@ionkov.net>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Christian Schoenebeck <linux_oss@crudebyte.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Xiubo Li <xiubli@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: Tom Talpey <tom@talpey.com>
cc: Bharath SM <bharathsm@microsoft.com>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Anna Schumaker <anna@kernel.org>
cc: netfs@lists.linux.dev
cc: v9fs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
2024-04-29 15:01:42 +01:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* NFS filesystem cache interface definitions
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#ifndef _NFS_FSCACHE_H
#define _NFS_FSCACHE_H
#include <linux/swap.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/nfs4_mount.h>
#include <linux/fscache.h>
#include <linux/iversion.h>
#ifdef CONFIG_NFS_FSCACHE
/*
* Definition of the auxiliary data attached to NFS inode storage objects
* within the cache.
*
* The contents of this struct are recorded in the on-disk local cache in the
* auxiliary data attached to the data storage object backing an inode. This
* permits coherency to be managed when a new inode binds to an already extant
* cache object.
*/
struct nfs_fscache_inode_auxdata {
s64 mtime_sec;
s64 mtime_nsec;
s64 ctime_sec;
s64 ctime_nsec;
u64 change_attr;
};
struct nfs_netfs_io_data {
/*
* NFS may split a netfs_io_subrequest into multiple RPCs, each
* with their own read completion. In netfs, we can only call
* netfs_subreq_terminated() once for each subrequest. Use the
* refcount here to double as a marker of the last RPC completion,
* and only call netfs via netfs_subreq_terminated() once.
*/
refcount_t refcount;
struct netfs_io_subrequest *sreq;
/*
* Final disposition of the netfs_io_subrequest, sent in
* netfs_subreq_terminated()
*/
atomic64_t transferred;
int error;
};
static inline void nfs_netfs_get(struct nfs_netfs_io_data *netfs)
{
refcount_inc(&netfs->refcount);
}
static inline void nfs_netfs_put(struct nfs_netfs_io_data *netfs)
{
ssize_t final_len;
/* Only the last RPC completion should call netfs_subreq_terminated() */
if (!refcount_dec_and_test(&netfs->refcount))
return;
/*
* The NFS pageio interface may read a complete page, even when netfs
* only asked for a partial page. Specifically, this may be seen when
* one thread is truncating a file while another one is reading the last
* page of the file.
* Correct the final length here to be no larger than the netfs subrequest
* length, and thus avoid netfs's "Subreq overread" warning message.
*/
final_len = min_t(s64, netfs->sreq->len, atomic64_read(&netfs->transferred));
netfs_subreq_terminated(netfs->sreq, netfs->error ?: final_len, false);
kfree(netfs);
}
static inline void nfs_netfs_inode_init(struct nfs_inode *nfsi)
{
netfs_inode_init(&nfsi->netfs, &nfs_netfs_ops, false);
/* [DEPRECATED] Use PG_private_2 to mark folio being written to the cache. */
__set_bit(NETFS_ICTX_USE_PGPRIV2, &nfsi->netfs.flags);
}
extern void nfs_netfs_initiate_read(struct nfs_pgio_header *hdr);
extern void nfs_netfs_read_completion(struct nfs_pgio_header *hdr);
extern int nfs_netfs_folio_unlock(struct folio *folio);
/*
* fscache.c
*/
extern int nfs_fscache_get_super_cookie(struct super_block *, const char *, int);
extern void nfs_fscache_release_super_cookie(struct super_block *);
extern void nfs_fscache_init_inode(struct inode *);
extern void nfs_fscache_clear_inode(struct inode *);
extern void nfs_fscache_open_file(struct inode *, struct file *);
extern void nfs_fscache_release_file(struct inode *, struct file *);
extern int nfs_netfs_readahead(struct readahead_control *ractl);
extern int nfs_netfs_read_folio(struct file *file, struct folio *folio);
static inline bool nfs_fscache_release_folio(struct folio *folio, gfp_t gfp)
{
if (folio_test_fscache(folio)) {
if (current_is_kswapd() || !(gfp & __GFP_FS))
return false;
folio_wait_fscache(folio);
}
fscache_note_page_release(netfs_i_cookie(netfs_inode(folio->mapping->host)));
return true;
}
static inline void nfs_fscache_update_auxdata(struct nfs_fscache_inode_auxdata *auxdata,
struct inode *inode)
{
memset(auxdata, 0, sizeof(*auxdata));
auxdata->mtime_sec = inode_get_mtime(inode).tv_sec;
auxdata->mtime_nsec = inode_get_mtime(inode).tv_nsec;
auxdata->ctime_sec = inode_get_ctime(inode).tv_sec;
auxdata->ctime_nsec = inode_get_ctime(inode).tv_nsec;
if (NFS_SERVER(inode)->nfs_client->rpc_ops->version == 4)
auxdata->change_attr = inode_peek_iversion_raw(inode);
}
/*
* Invalidate the contents of fscache for this inode. This will not sleep.
*/
static inline void nfs_fscache_invalidate(struct inode *inode, int flags)
{
struct nfs_fscache_inode_auxdata auxdata;
struct fscache_cookie *cookie = netfs_i_cookie(&NFS_I(inode)->netfs);
nfs_fscache_update_auxdata(&auxdata, inode);
fscache_invalidate(cookie, &auxdata, i_size_read(inode), flags);
}
/*
* indicate the client caching state as readable text
*/
static inline const char *nfs_server_fscache_state(struct nfs_server *server)
{
if (server->fscache)
return "yes";
return "no ";
}
static inline void nfs_netfs_set_pgio_header(struct nfs_pgio_header *hdr,
struct nfs_pageio_descriptor *desc)
{
hdr->netfs = desc->pg_netfs;
}
static inline void nfs_netfs_set_pageio_descriptor(struct nfs_pageio_descriptor *desc,
struct nfs_pgio_header *hdr)
{
desc->pg_netfs = hdr->netfs;
}
static inline void nfs_netfs_reset_pageio_descriptor(struct nfs_pageio_descriptor *desc)
{
desc->pg_netfs = NULL;
}
#else /* CONFIG_NFS_FSCACHE */
static inline void nfs_netfs_inode_init(struct nfs_inode *nfsi) {}
static inline void nfs_netfs_initiate_read(struct nfs_pgio_header *hdr) {}
static inline void nfs_netfs_read_completion(struct nfs_pgio_header *hdr) {}
static inline int nfs_netfs_folio_unlock(struct folio *folio)
{
return 1;
}
static inline void nfs_fscache_release_super_cookie(struct super_block *sb) {}
static inline void nfs_fscache_init_inode(struct inode *inode) {}
static inline void nfs_fscache_clear_inode(struct inode *inode) {}
static inline void nfs_fscache_open_file(struct inode *inode,
struct file *filp) {}
static inline void nfs_fscache_release_file(struct inode *inode, struct file *file) {}
static inline int nfs_netfs_readahead(struct readahead_control *ractl)
{
return -ENOBUFS;
}
static inline int nfs_netfs_read_folio(struct file *file, struct folio *folio)
{
return -ENOBUFS;
}
static inline bool nfs_fscache_release_folio(struct folio *folio, gfp_t gfp)
{
return true; /* may release folio */
}
static inline void nfs_fscache_invalidate(struct inode *inode, int flags) {}
static inline const char *nfs_server_fscache_state(struct nfs_server *server)
{
return "no ";
}
static inline void nfs_netfs_set_pgio_header(struct nfs_pgio_header *hdr,
struct nfs_pageio_descriptor *desc) {}
static inline void nfs_netfs_set_pageio_descriptor(struct nfs_pageio_descriptor *desc,
struct nfs_pgio_header *hdr) {}
static inline void nfs_netfs_reset_pageio_descriptor(struct nfs_pageio_descriptor *desc) {}
#endif /* CONFIG_NFS_FSCACHE */
#endif /* _NFS_FSCACHE_H */
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