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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* General filesystem caching backing cache interface
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* NOTE!!! See:
*
* Documentation/filesystems/caching/backend-api.rst
*
* for a description of the cache backend interface declared here.
*/
#ifndef _LINUX_FSCACHE_CACHE_H
#define _LINUX_FSCACHE_CACHE_H
#include <linux/fscache.h>
enum fscache_cache_trace;
enum fscache_cookie_trace;
enum fscache_access_trace;
enum fscache_cache_state {
FSCACHE_CACHE_IS_NOT_PRESENT, /* No cache is present for this name */
FSCACHE_CACHE_IS_PREPARING, /* A cache is preparing to come live */
FSCACHE_CACHE_IS_ACTIVE, /* Attached cache is active and can be used */
FSCACHE_CACHE_GOT_IOERROR, /* Attached cache stopped on I/O error */
FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */
#define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1)
};
/*
* Cache cookie.
*/
struct fscache_cache {
const struct fscache_cache_ops *ops;
struct list_head cache_link; /* Link in cache list */
void *cache_priv; /* Private cache data (or NULL) */
refcount_t ref;
atomic_t n_volumes; /* Number of active volumes; */
atomic_t n_accesses; /* Number of in-progress accesses on the cache */
atomic_t object_count; /* no. of live objects in this cache */
unsigned int debug_id;
enum fscache_cache_state state;
char *name;
};
/*
* cache operations
*/
struct fscache_cache_ops {
/* name of cache provider */
const char *name;
/* Acquire a volume */
void (*acquire_volume)(struct fscache_volume *volume);
/* Free the cache's data attached to a volume */
void (*free_volume)(struct fscache_volume *volume);
/* Look up a cookie in the cache */
bool (*lookup_cookie)(struct fscache_cookie *cookie);
/* Withdraw an object without any cookie access counts held */
void (*withdraw_cookie)(struct fscache_cookie *cookie);
/* Change the size of a data object */
void (*resize_cookie)(struct netfs_cache_resources *cres,
loff_t new_size);
/* Invalidate an object */
bool (*invalidate_cookie)(struct fscache_cookie *cookie);
/* Begin an operation for the netfs lib */
bool (*begin_operation)(struct netfs_cache_resources *cres,
enum fscache_want_state want_state);
/* Prepare to write to a live cache object */
void (*prepare_to_write)(struct fscache_cookie *cookie);
};
extern struct workqueue_struct *fscache_wq;
extern wait_queue_head_t fscache_clearance_waiters;
/*
* out-of-line cache backend functions
*/
extern struct rw_semaphore fscache_addremove_sem;
extern struct fscache_cache *fscache_acquire_cache(const char *name);
extern void fscache_relinquish_cache(struct fscache_cache *cache);
extern int fscache_add_cache(struct fscache_cache *cache,
const struct fscache_cache_ops *ops,
void *cache_priv);
extern void fscache_withdraw_cache(struct fscache_cache *cache);
extern void fscache_withdraw_volume(struct fscache_volume *volume);
extern void fscache_withdraw_cookie(struct fscache_cookie *cookie);
extern void fscache_io_error(struct fscache_cache *cache);
extern void fscache_end_volume_access(struct fscache_volume *volume,
struct fscache_cookie *cookie,
enum fscache_access_trace why);
extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
enum fscache_cookie_trace where);
extern void fscache_put_cookie(struct fscache_cookie *cookie,
enum fscache_cookie_trace where);
extern void fscache_end_cookie_access(struct fscache_cookie *cookie,
enum fscache_access_trace why);
extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie);
extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie);
extern void fscache_caching_failed(struct fscache_cookie *cookie);
extern bool fscache_wait_for_operation(struct netfs_cache_resources *cred,
enum fscache_want_state state);
/**
* fscache_cookie_state - Read the state of a cookie
* @cookie: The cookie to query
*
* Get the state of a cookie, imposing an ordering between the cookie contents
* and the state value. Paired with fscache_set_cookie_state().
*/
static inline
enum fscache_cookie_state fscache_cookie_state(struct fscache_cookie *cookie)
{
return smp_load_acquire(&cookie->state);
}
/**
* fscache_get_key - Get a pointer to the cookie key
* @cookie: The cookie to query
*
* Return a pointer to the where a cookie's key is stored.
*/
static inline void *fscache_get_key(struct fscache_cookie *cookie)
{
if (cookie->key_len <= sizeof(cookie->inline_key))
return cookie->inline_key;
else
return cookie->key;
}
static inline struct fscache_cookie *fscache_cres_cookie(struct netfs_cache_resources *cres)
{
return cres->cache_priv;
}
/**
* fscache_count_object - Tell fscache that an object has been added
* @cache: The cache to account to
*
* Tell fscache that an object has been added to the cache. This prevents the
* cache from tearing down the cache structure until the object is uncounted.
*/
static inline void fscache_count_object(struct fscache_cache *cache)
{
atomic_inc(&cache->object_count);
}
/**
* fscache_uncount_object - Tell fscache that an object has been removed
* @cache: The cache to account to
*
* Tell fscache that an object has been removed from the cache and will no
* longer be accessed. After this point, the cache cookie may be destroyed.
*/
static inline void fscache_uncount_object(struct fscache_cache *cache)
{
if (atomic_dec_and_test(&cache->object_count))
wake_up_all(&fscache_clearance_waiters);
}
/**
* fscache_wait_for_objects - Wait for all objects to be withdrawn
* @cache: The cache to query
*
* Wait for all extant objects in a cache to finish being withdrawn
* and go away.
*/
static inline void fscache_wait_for_objects(struct fscache_cache *cache)
{
wait_event(fscache_clearance_waiters,
atomic_read(&cache->object_count) == 0);
}
#ifdef CONFIG_FSCACHE_STATS
extern atomic_t fscache_n_read;
extern atomic_t fscache_n_write;
extern atomic_t fscache_n_no_write_space;
extern atomic_t fscache_n_no_create_space;
#define fscache_count_read() atomic_inc(&fscache_n_read)
#define fscache_count_write() atomic_inc(&fscache_n_write)
#define fscache_count_no_write_space() atomic_inc(&fscache_n_no_write_space)
#define fscache_count_no_create_space() atomic_inc(&fscache_n_no_create_space)
#else
#define fscache_count_read() do {} while(0)
#define fscache_count_write() do {} while(0)
#define fscache_count_no_write_space() do {} while(0)
#define fscache_count_no_create_space() do {} while(0)
#endif
#endif /* _LINUX_FSCACHE_CACHE_H */
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