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편집 파일: fscache-cache.h

/* 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/* Attached cache stopped on I/O error */ FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */ #define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1) }; /* * Cache cookie.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; extern atomic_t fscache_n_culled; #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) #define fscache_count_culled() atomic_inc(&fscache_n_culled) #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) #define fscache_count_culled() do {} while(0) #endif #endif /* _LINUX_FSCACHE_CACHE_H */