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/* Attached cache stopped on I/O error */ 28 FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */ 29 #define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1) 30 }; 31 32 /* 33 * Cache cookie. 34 */ 35 struct fscache_cache { 36 const struct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 /* 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 /* Invalidate an object */ 68 bool (*invalidate_cookie)(struct fscache_cookie *cookie); 69 70 /* Prepare to write to a live cache object */ 71 void (*prepare_to_write)(struct fscache_cookie *cookie); 72 }; 73 74 extern struct workqueue_struct *fscache_wq; 75 76 /* 77 * out-of-line cache backend functions 78 */ 79 extern struct rw_semaphore fscache_addremove_sem; 80 extern struct fscache_cache *fscache_acquire_cache(const char *name); 81 extern void fscache_relinquish_cache(struct fscache_cache *cache); 82 extern int fscache_add_cache(struct fscache_cache *cache, 83 const struct fscache_cache_ops *ops, 84 void *cache_priv); 85 extern void fscache_withdraw_cache(struct fscache_cache *cache); 86 extern void fscache_withdraw_volume(struct fscache_volume *volume); 87 extern void fscache_withdraw_cookie(struct fscache_cookie *cookie); 88 89 extern void fscache_io_error(struct fscache_cache *cache); 90 91 extern void fscache_end_volume_access(struct fscache_volume *volume, 92 struct fscache_cookie *cookie, 93 enum fscache_access_trace why); 94 95 extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, 96 enum fscache_cookie_trace where); 97 extern void fscache_put_cookie(struct fscache_cookie *cookie, 98 enum fscache_cookie_trace where); 99 extern void fscache_end_cookie_access(struct fscache_cookie *cookie, 100 enum fscache_access_trace why); 101 extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie); 102 extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie); 103 extern void fscache_caching_failed(struct fscache_cookie *cookie); 104 105 /** 106 * fscache_cookie_state - Read the state of a cookie 107 * @cookie: The cookie to query 108 * 109 * Get the state of a cookie, imposing an ordering between the cookie contents 110 * and the state value. Paired with fscache_set_cookie_state(). 111 */ 112 static inline 113 enum fscache_cookie_state fscache_cookie_state(struct fscache_cookie *cookie) 114 { 115 return smp_load_acquire(&cookie->state); 116 } 117 118 /** 119 * fscache_get_key - Get a pointer to the cookie key 120 * @cookie: The cookie to query 121 * 122 * Return a pointer to the where a cookie's key is stored. 123 */ 124 static inline void *fscache_get_key(struct fscache_cookie *cookie) 125 { 126 if (cookie->key_len <= sizeof(cookie->inline_key)) 127 return cookie->inline_key; 128 else 129 return cookie->key; 130 } 131 132 #endif /* _LINUX_FSCACHE_CACHE_H */ 133