1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* General filesystem caching backing cache interface 3 * 4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells ([email protected]) 6 * 7 * NOTE!!! See: 8 * 9 * Documentation/filesystems/caching/backend-api.rst 10 * 11 * for a description of the cache backend interface declared here. 12 */ 13 14 #ifndef _LINUX_FSCACHE_CACHE_H 15 #define _LINUX_FSCACHE_CACHE_H 16 17 #include <linux/fscache.h> 18 19 enum fscache_cache_trace; 20 enum fscache_cookie_trace; 21 enum fscache_access_trace; 22 23 enum fscache_cache_state { 24 FSCACHE_CACHE_IS_NOT_PRESENT, /* No cache is present for this name */ 25 FSCACHE_CACHE_IS_PREPARING, /* A cache is preparing to come live */ 26 FSCACHE_CACHE_IS_ACTIVE, /* Attached cache is active and can be used */ 27 FSCACHE_CACHE_GOT_IOERROR, /* Attached cache stopped on I/O error */ 28 FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */ 29 #define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1) 30 }; 31 32 /* 33 * Cache cookie. 34 */ 35 struct fscache_cache { 36 const struct fscache_cache_ops *ops; 37 struct list_head cache_link; /* Link in cache list */ 38 void *cache_priv; /* Private cache data (or NULL) */ 39 refcount_t ref; 40 atomic_t n_volumes; /* Number of active volumes; */ 41 atomic_t n_accesses; /* Number of in-progress accesses on the cache */ 42 atomic_t object_count; /* no. of live objects in this cache */ 43 unsigned int debug_id; 44 enum fscache_cache_state state; 45 char *name; 46 }; 47 48 /* 49 * cache operations 50 */ 51 struct fscache_cache_ops { 52 /* name of cache provider */ 53 const char *name; 54 }; 55 56 extern struct workqueue_struct *fscache_wq; 57 58 /* 59 * out-of-line cache backend functions 60 */ 61 extern struct rw_semaphore fscache_addremove_sem; 62 extern struct fscache_cache *fscache_acquire_cache(const char *name); 63 extern void fscache_relinquish_cache(struct fscache_cache *cache); 64 extern int fscache_add_cache(struct fscache_cache *cache, 65 const struct fscache_cache_ops *ops, 66 void *cache_priv); 67 extern void fscache_withdraw_cache(struct fscache_cache *cache); 68 69 extern void fscache_end_volume_access(struct fscache_volume *volume, 70 struct fscache_cookie *cookie, 71 enum fscache_access_trace why); 72 73 extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, 74 enum fscache_cookie_trace where); 75 extern void fscache_put_cookie(struct fscache_cookie *cookie, 76 enum fscache_cookie_trace where); 77 extern void fscache_end_cookie_access(struct fscache_cookie *cookie, 78 enum fscache_access_trace why); 79 extern void fscache_set_cookie_state(struct fscache_cookie *cookie, 80 enum fscache_cookie_state state); 81 82 /** 83 * fscache_get_key - Get a pointer to the cookie key 84 * @cookie: The cookie to query 85 * 86 * Return a pointer to the where a cookie's key is stored. 87 */ 88 static inline void *fscache_get_key(struct fscache_cookie *cookie) 89 { 90 if (cookie->key_len <= sizeof(cookie->inline_key)) 91 return cookie->inline_key; 92 else 93 return cookie->key; 94 } 95 96 #endif /* _LINUX_FSCACHE_CACHE_H */ 97