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linux/fs/netfs/internal.h
David Howells 92a714d727 netfs: Fix interaction between write-streaming and cachefiles culling 
An issue can occur between write-streaming (storing dirty data in partial
non-uptodate pages) and a cachefiles object being culled to make space.
The problem occurs because the cache object is only marked in use while
there are files open using it.  Once it has been released, it can be culled
and the cookie marked disabled.

At this point, a streaming write is permitted to occur (if the cache is
active, we require pages to be prefetched and cached), but the cache can
become active again before this gets flushed out - and then two effects can
occur:

 (1) The cache may be asked to write out a region that's less than its DIO
     block size (assumed by cachefiles to be PAGE_SIZE) - and this causes
     one of two debugging statements to be emitted.

 (2) netfs_how_to_modify() gets confused because it sees a page that isn't
     allowed to be non-uptodate being uptodate and tries to prefetch it -
     leading to a warning that PG_fscache is set twice.

Fix this by the following means:

 (1) Add a netfs_inode flag to disallow write-streaming to an inode and set
     it if we ever do local caching of that inode.  It remains set for the
     lifetime of that inode - even if the cookie becomes disabled.

 (2) If the no-write-streaming flag is set, then make netfs_how_to_modify()
     always want to prefetch instead.

 (3) If netfs_how_to_modify() decides it wants to prefetch a folio, but
     that folio has write-streamed data in it, then it requires the folio
     be flushed first.

 (4) Export a counter of the number of times we wanted to prefetch a
     non-uptodate page, but found it had write-streamed data in it.

 (5) Export a counter of the number of times we cancelled a write to the
     cache because it didn't DIO align and remove the debug statements.

Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-erofs@lists.ozlabs.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
2024-01-05 15:42:25 +00:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Internal definitions for network filesystem support
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/netfs.h>
#include <linux/fscache.h>
#include <linux/fscache-cache.h>
#include <trace/events/netfs.h>
#include <trace/events/fscache.h>
#ifdef pr_fmt
#undef pr_fmt
#endif
#define pr_fmt(fmt) "netfs: " fmt
/*
* buffered_read.c
*/
void netfs_rreq_unlock_folios(struct netfs_io_request *rreq);
int netfs_prefetch_for_write(struct file *file, struct folio *folio,
size_t offset, size_t len);
/*
* io.c
*/
int netfs_begin_read(struct netfs_io_request *rreq, bool sync);
/*
* main.c
*/
extern unsigned int netfs_debug;
extern struct list_head netfs_io_requests;
extern spinlock_t netfs_proc_lock;
#ifdef CONFIG_PROC_FS
static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq)
{
spin_lock(&netfs_proc_lock);
list_add_tail_rcu(&rreq->proc_link, &netfs_io_requests);
spin_unlock(&netfs_proc_lock);
}
static inline void netfs_proc_del_rreq(struct netfs_io_request *rreq)
{
if (!list_empty(&rreq->proc_link)) {
spin_lock(&netfs_proc_lock);
list_del_rcu(&rreq->proc_link);
spin_unlock(&netfs_proc_lock);
}
}
#else
static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq) {}
static inline void netfs_proc_del_rreq(struct netfs_io_request *rreq) {}
#endif
/*
* misc.c
*/
#define NETFS_FLAG_PUT_MARK BIT(0)
#define NETFS_FLAG_PAGECACHE_MARK BIT(1)
int netfs_xa_store_and_mark(struct xarray *xa, unsigned long index,
struct folio *folio, unsigned int flags,
gfp_t gfp_mask);
int netfs_add_folios_to_buffer(struct xarray *buffer,
struct address_space *mapping,
pgoff_t index, pgoff_t to, gfp_t gfp_mask);
void netfs_clear_buffer(struct xarray *buffer);
/*
* objects.c
*/
struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
struct file *file,
loff_t start, size_t len,
enum netfs_io_origin origin);
void netfs_get_request(struct netfs_io_request *rreq, enum netfs_rreq_ref_trace what);
void netfs_clear_subrequests(struct netfs_io_request *rreq, bool was_async);
void netfs_put_request(struct netfs_io_request *rreq, bool was_async,
enum netfs_rreq_ref_trace what);
struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq);
static inline void netfs_see_request(struct netfs_io_request *rreq,
enum netfs_rreq_ref_trace what)
{
trace_netfs_rreq_ref(rreq->debug_id, refcount_read(&rreq->ref), what);
}
/*
* output.c
*/
int netfs_begin_write(struct netfs_io_request *wreq, bool may_wait,
enum netfs_write_trace what);
struct netfs_io_request *netfs_begin_writethrough(struct kiocb *iocb, size_t len);
int netfs_advance_writethrough(struct netfs_io_request *wreq, size_t copied, bool to_page_end);
int netfs_end_writethrough(struct netfs_io_request *wreq, struct kiocb *iocb);
/*
* stats.c
*/
#ifdef CONFIG_NETFS_STATS
extern atomic_t netfs_n_rh_dio_read;
extern atomic_t netfs_n_rh_dio_write;
extern atomic_t netfs_n_rh_readahead;
extern atomic_t netfs_n_rh_readpage;
extern atomic_t netfs_n_rh_rreq;
extern atomic_t netfs_n_rh_sreq;
extern atomic_t netfs_n_rh_download;
extern atomic_t netfs_n_rh_download_done;
extern atomic_t netfs_n_rh_download_failed;
extern atomic_t netfs_n_rh_download_instead;
extern atomic_t netfs_n_rh_read;
extern atomic_t netfs_n_rh_read_done;
extern atomic_t netfs_n_rh_read_failed;
extern atomic_t netfs_n_rh_zero;
extern atomic_t netfs_n_rh_short_read;
extern atomic_t netfs_n_rh_write;
extern atomic_t netfs_n_rh_write_begin;
extern atomic_t netfs_n_rh_write_done;
extern atomic_t netfs_n_rh_write_failed;
extern atomic_t netfs_n_rh_write_zskip;
extern atomic_t netfs_n_wh_wstream_conflict;
extern atomic_t netfs_n_wh_upload;
extern atomic_t netfs_n_wh_upload_done;
extern atomic_t netfs_n_wh_upload_failed;
extern atomic_t netfs_n_wh_write;
extern atomic_t netfs_n_wh_write_done;
extern atomic_t netfs_n_wh_write_failed;
int netfs_stats_show(struct seq_file *m, void *v);
static inline void netfs_stat(atomic_t *stat)
{
atomic_inc(stat);
}
static inline void netfs_stat_d(atomic_t *stat)
{
atomic_dec(stat);
}
#else
#define netfs_stat(x) do {} while(0)
#define netfs_stat_d(x) do {} while(0)
#endif
/*
* Miscellaneous functions.
*/
static inline bool netfs_is_cache_enabled(struct netfs_inode *ctx)
{
#if IS_ENABLED(CONFIG_FSCACHE)
struct fscache_cookie *cookie = ctx->cache;
return fscache_cookie_valid(cookie) && cookie->cache_priv &&
fscache_cookie_enabled(cookie);
#else
return false;
#endif
}
/*
* Get a ref on a netfs group attached to a dirty page (e.g. a ceph snap).
*/
static inline struct netfs_group *netfs_get_group(struct netfs_group *netfs_group)
{
if (netfs_group)
refcount_inc(&netfs_group->ref);
return netfs_group;
}
/*
* Dispose of a netfs group attached to a dirty page (e.g. a ceph snap).
*/
static inline void netfs_put_group(struct netfs_group *netfs_group)
{
if (netfs_group && refcount_dec_and_test(&netfs_group->ref))
netfs_group->free(netfs_group);
}
/*
* Dispose of a netfs group attached to a dirty page (e.g. a ceph snap).
*/
static inline void netfs_put_group_many(struct netfs_group *netfs_group, int nr)
{
if (netfs_group && refcount_sub_and_test(nr, &netfs_group->ref))
netfs_group->free(netfs_group);
}
/*
* fscache-cache.c
*/
#ifdef CONFIG_PROC_FS
extern const struct seq_operations fscache_caches_seq_ops;
#endif
bool fscache_begin_cache_access(struct fscache_cache *cache, enum fscache_access_trace why);
void fscache_end_cache_access(struct fscache_cache *cache, enum fscache_access_trace why);
struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache);
void fscache_put_cache(struct fscache_cache *cache, enum fscache_cache_trace where);
static inline enum fscache_cache_state fscache_cache_state(const struct fscache_cache *cache)
{
return smp_load_acquire(&cache->state);
}
static inline bool fscache_cache_is_live(const struct fscache_cache *cache)
{
return fscache_cache_state(cache) == FSCACHE_CACHE_IS_ACTIVE;
}
static inline void fscache_set_cache_state(struct fscache_cache *cache,
enum fscache_cache_state new_state)
{
smp_store_release(&cache->state, new_state);
}
static inline bool fscache_set_cache_state_maybe(struct fscache_cache *cache,
enum fscache_cache_state old_state,
enum fscache_cache_state new_state)
{
return try_cmpxchg_release(&cache->state, &old_state, new_state);
}
/*
* fscache-cookie.c
*/
extern struct kmem_cache *fscache_cookie_jar;
#ifdef CONFIG_PROC_FS
extern const struct seq_operations fscache_cookies_seq_ops;
#endif
extern struct timer_list fscache_cookie_lru_timer;
extern void fscache_print_cookie(struct fscache_cookie *cookie, char prefix);
extern bool fscache_begin_cookie_access(struct fscache_cookie *cookie,
enum fscache_access_trace why);
static inline void fscache_see_cookie(struct fscache_cookie *cookie,
enum fscache_cookie_trace where)
{
trace_fscache_cookie(cookie->debug_id, refcount_read(&cookie->ref),
where);
}
/*
* fscache-main.c
*/
extern unsigned int fscache_hash(unsigned int salt, const void *data, size_t len);
#ifdef CONFIG_FSCACHE
int __init fscache_init(void);
void __exit fscache_exit(void);
#else
static inline int fscache_init(void) { return 0; }
static inline void fscache_exit(void) {}
#endif
/*
* fscache-proc.c
*/
#ifdef CONFIG_PROC_FS
extern int __init fscache_proc_init(void);
extern void fscache_proc_cleanup(void);
#else
#define fscache_proc_init() (0)
#define fscache_proc_cleanup() do {} while (0)
#endif
/*
* fscache-stats.c
*/
#ifdef CONFIG_FSCACHE_STATS
extern atomic_t fscache_n_volumes;
extern atomic_t fscache_n_volumes_collision;
extern atomic_t fscache_n_volumes_nomem;
extern atomic_t fscache_n_cookies;
extern atomic_t fscache_n_cookies_lru;
extern atomic_t fscache_n_cookies_lru_expired;
extern atomic_t fscache_n_cookies_lru_removed;
extern atomic_t fscache_n_cookies_lru_dropped;
extern atomic_t fscache_n_acquires;
extern atomic_t fscache_n_acquires_ok;
extern atomic_t fscache_n_acquires_oom;
extern atomic_t fscache_n_invalidates;
extern atomic_t fscache_n_relinquishes;
extern atomic_t fscache_n_relinquishes_retire;
extern atomic_t fscache_n_relinquishes_dropped;
extern atomic_t fscache_n_resizes;
extern atomic_t fscache_n_resizes_null;
static inline void fscache_stat(atomic_t *stat)
{
atomic_inc(stat);
}
static inline void fscache_stat_d(atomic_t *stat)
{
atomic_dec(stat);
}
#define __fscache_stat(stat) (stat)
int fscache_stats_show(struct seq_file *m);
#else
#define __fscache_stat(stat) (NULL)
#define fscache_stat(stat) do {} while (0)
#define fscache_stat_d(stat) do {} while (0)
static inline int fscache_stats_show(struct seq_file *m) { return 0; }
#endif
/*
* fscache-volume.c
*/
#ifdef CONFIG_PROC_FS
extern const struct seq_operations fscache_volumes_seq_ops;
#endif
struct fscache_volume *fscache_get_volume(struct fscache_volume *volume,
enum fscache_volume_trace where);
void fscache_put_volume(struct fscache_volume *volume,
enum fscache_volume_trace where);
bool fscache_begin_volume_access(struct fscache_volume *volume,
struct fscache_cookie *cookie,
enum fscache_access_trace why);
void fscache_create_volume(struct fscache_volume *volume, bool wait);
/*****************************************************************************/
/*
* debug tracing
*/
#define dbgprintk(FMT, ...) \
printk("[%-6.6s] "FMT"\n", current->comm, ##__VA_ARGS__)
#define kenter(FMT, ...) dbgprintk("==> %s("FMT")", __func__, ##__VA_ARGS__)
#define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
#define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__)
#ifdef __KDEBUG
#define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__)
#define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__)
#define _debug(FMT, ...) kdebug(FMT, ##__VA_ARGS__)
#elif defined(CONFIG_NETFS_DEBUG)
#define _enter(FMT, ...) \
do { \
if (netfs_debug) \
kenter(FMT, ##__VA_ARGS__); \
} while (0)
#define _leave(FMT, ...) \
do { \
if (netfs_debug) \
kleave(FMT, ##__VA_ARGS__); \
} while (0)
#define _debug(FMT, ...) \
do { \
if (netfs_debug) \
kdebug(FMT, ##__VA_ARGS__); \
} while (0)
#else
#define _enter(FMT, ...) no_printk("==> %s("FMT")", __func__, ##__VA_ARGS__)
#define _leave(FMT, ...) no_printk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
#define _debug(FMT, ...) no_printk(FMT, ##__VA_ARGS__)
#endif
/*
* assertions
*/
#if 1 /* defined(__KDEBUGALL) */
#define ASSERT(X) \
do { \
if (unlikely(!(X))) { \
pr_err("\n"); \
pr_err("Assertion failed\n"); \
BUG(); \
} \
} while (0)
#define ASSERTCMP(X, OP, Y) \
do { \
if (unlikely(!((X) OP (Y)))) { \
pr_err("\n"); \
pr_err("Assertion failed\n"); \
pr_err("%lx " #OP " %lx is false\n", \
(unsigned long)(X), (unsigned long)(Y)); \
BUG(); \
} \
} while (0)
#define ASSERTIF(C, X) \
do { \
if (unlikely((C) && !(X))) { \
pr_err("\n"); \
pr_err("Assertion failed\n"); \
BUG(); \
} \
} while (0)
#define ASSERTIFCMP(C, X, OP, Y) \
do { \
if (unlikely((C) && !((X) OP (Y)))) { \
pr_err("\n"); \
pr_err("Assertion failed\n"); \
pr_err("%lx " #OP " %lx is false\n", \
(unsigned long)(X), (unsigned long)(Y)); \
BUG(); \
} \
} while (0)
#else
#define ASSERT(X) do {} while (0)
#define ASSERTCMP(X, OP, Y) do {} while (0)
#define ASSERTIF(C, X) do {} while (0)
#define ASSERTIFCMP(C, X, OP, Y) do {} while (0)
#endif /* assert or not */
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