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 (dhowells@redhat.com) 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/* Attached cache stopped on I/O error */ 28 FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */ 29 #define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1) 30 }; 31 32 /* 33 * Cache cookie. 34 */ 35 struct fscache_cache { 36 const struct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 /* Acquire a volume */ 56 void (*acquire_volume)(struct fscache_volume *volume); 57 58 /* Free the cache's data attached to a volume */ 59 void (*free_volume)(struct fscache_volume *volume); 60 61 /* Look up a cookie in the cache */ 62 bool (*lookup_cookie)(struct fscache_cookie *cookie); 63 64 /* Withdraw an object without any cookie access counts held */ 65 void (*withdraw_cookie)(struct fscache_cookie *cookie); 66 67 /* Change the size of a data object */ 68 void (*resize_cookie)(struct netfs_cache_resources *cres, 69 loff_t new_size); 70 71 /* Invalidate an object */ 72 bool (*invalidate_cookie)(struct fscache_cookie *cookie); 73 74 /* Begin an operation for the netfs lib */ 75 bool (*begin_operation)(struct netfs_cache_resources *cres, 76 enum fscache_want_state want_state); 77 78 /* Prepare to write to a live cache object */ 79 void (*prepare_to_write)(struct fscache_cookie *cookie); 80 }; 81 82 extern struct workqueue_struct *fscache_wq; 83 extern wait_queue_head_t fscache_clearance_waiters; 84 85 /* 86 * out-of-line cache backend functions 87 */ 88 extern struct rw_semaphore fscache_addremove_sem; 89 extern struct fscache_cache *fscache_acquire_cache(const char *name); 90 extern void fscache_relinquish_cache(struct fscache_cache *cache); 91 extern int fscache_add_cache(struct fscache_cache *cache, 92 const struct fscache_cache_ops *ops, 93 void *cache_priv); 94 extern void fscache_withdraw_cache(struct fscache_cache *cache); 95 extern void fscache_withdraw_volume(struct fscache_volume *volume); 96 extern void fscache_withdraw_cookie(struct fscache_cookie *cookie); 97 98 extern void fscache_io_error(struct fscache_cache *cache); 99 100 extern void fscache_end_volume_access(struct fscache_volume *volume, 101 struct fscache_cookie *cookie, 102 enum fscache_access_trace why); 103 104 extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, 105 enum fscache_cookie_trace where); 106 extern void fscache_put_cookie(struct fscache_cookie *cookie, 107 enum fscache_cookie_trace where); 108 extern void fscache_end_cookie_access(struct fscache_cookie *cookie, 109 enum fscache_access_trace why); 110 extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie); 111 extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie); 112 extern void fscache_caching_failed(struct fscache_cookie *cookie); 113 extern bool fscache_wait_for_operation(struct netfs_cache_resources *cred, 114 enum fscache_want_state state); 115 116 /** 117 * fscache_cookie_state - Read the state of a cookie 118 * @cookie: The cookie to query 119 * 120 * Get the state of a cookie, imposing an ordering between the cookie contents 121 * and the state value. Paired with fscache_set_cookie_state(). 122 */ 123 static inline 124 enum fscache_cookie_state fscache_cookie_state(struct fscache_cookie *cookie) 125 { 126 return smp_load_acquire(&cookie->state); 127 } 128 129 /** 130 * fscache_get_key - Get a pointer to the cookie key 131 * @cookie: The cookie to query 132 * 133 * Return a pointer to the where a cookie's key is stored. 134 */ 135 static inline void *fscache_get_key(struct fscache_cookie *cookie) 136 { 137 if (cookie->key_len <= sizeof(cookie->inline_key)) 138 return cookie->inline_key; 139 else 140 return cookie->key; 141 } 142 143 static inline struct fscache_cookie *fscache_cres_cookie(struct netfs_cache_resources *cres) 144 { 145 return cres->cache_priv; 146 } 147 148 /** 149 * fscache_count_object - Tell fscache that an object has been added 150 * @cache: The cache to account to 151 * 152 * Tell fscache that an object has been added to the cache. This prevents the 153 * cache from tearing down the cache structure until the object is uncounted. 154 */ 155 static inline void fscache_count_object(struct fscache_cache *cache) 156 { 157 atomic_inc(&cache->object_count); 158 } 159 160 /** 161 * fscache_uncount_object - Tell fscache that an object has been removed 162 * @cache: The cache to account to 163 * 164 * Tell fscache that an object has been removed from the cache and will no 165 * longer be accessed. After this point, the cache cookie may be destroyed. 166 */ 167 static inline void fscache_uncount_object(struct fscache_cache *cache) 168 { 169 if (atomic_dec_and_test(&cache->object_count)) 170 wake_up_all(&fscache_clearance_waiters); 171 } 172 173 /** 174 * fscache_wait_for_objects - Wait for all objects to be withdrawn 175 * @cache: The cache to query 176 * 177 * Wait for all extant objects in a cache to finish being withdrawn 178 * and go away. 179 */ 180 static inline void fscache_wait_for_objects(struct fscache_cache *cache) 181 { 182 wait_event(fscache_clearance_waiters, 183 atomic_read(&cache->object_count) == 0); 184 } 185 186 #ifdef CONFIG_FSCACHE_STATS 187 extern atomic_t fscache_n_read; 188 extern atomic_t fscache_n_write; 189 extern atomic_t fscache_n_no_write_space; 190 extern atomic_t fscache_n_no_create_space; 191 extern atomic_t fscache_n_culled; 192 #define fscache_count_read() atomic_inc(&fscache_n_read) 193 #define fscache_count_write() atomic_inc(&fscache_n_write) 194 #define fscache_count_no_write_space() atomic_inc(&fscache_n_no_write_space) 195 #define fscache_count_no_create_space() atomic_inc(&fscache_n_no_create_space) 196 #define fscache_count_culled() atomic_inc(&fscache_n_culled) 197 #else 198 #define fscache_count_read() do {} while(0) 199 #define fscache_count_write() do {} while(0) 200 #define fscache_count_no_write_space() do {} while(0) 201 #define fscache_count_no_create_space() do {} while(0) 202 #define fscache_count_culled() do {} while(0) 203 #endif 204 205 #endif /* _LINUX_FSCACHE_CACHE_H */ 206