fscache-cache.h (6844B)
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 19enum fscache_cache_trace; 20enum fscache_cookie_trace; 21enum fscache_access_trace; 22 23enum 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/* Attached cache stopped on I/O error */ 28 FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */ 29#define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1) 30}; 31 32/* 33 * Cache cookie. 34 */ 35struct fscache_cache { 36 const struct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 */ 51struct 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 82extern struct workqueue_struct *fscache_wq; 83extern wait_queue_head_t fscache_clearance_waiters; 84 85/* 86 * out-of-line cache backend functions 87 */ 88extern struct rw_semaphore fscache_addremove_sem; 89extern struct fscache_cache *fscache_acquire_cache(const char *name); 90extern void fscache_relinquish_cache(struct fscache_cache *cache); 91extern int fscache_add_cache(struct fscache_cache *cache, 92 const struct fscache_cache_ops *ops, 93 void *cache_priv); 94extern void fscache_withdraw_cache(struct fscache_cache *cache); 95extern void fscache_withdraw_volume(struct fscache_volume *volume); 96extern void fscache_withdraw_cookie(struct fscache_cookie *cookie); 97 98extern void fscache_io_error(struct fscache_cache *cache); 99 100extern void fscache_end_volume_access(struct fscache_volume *volume, 101 struct fscache_cookie *cookie, 102 enum fscache_access_trace why); 103 104extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, 105 enum fscache_cookie_trace where); 106extern void fscache_put_cookie(struct fscache_cookie *cookie, 107 enum fscache_cookie_trace where); 108extern void fscache_end_cookie_access(struct fscache_cookie *cookie, 109 enum fscache_access_trace why); 110extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie); 111extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie); 112extern void fscache_caching_failed(struct fscache_cookie *cookie); 113extern 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 */ 123static inline 124enum 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 */ 135static 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 143static 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 */ 155static 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 */ 167static 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 */ 180static 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 187extern atomic_t fscache_n_read; 188extern atomic_t fscache_n_write; 189extern atomic_t fscache_n_no_write_space; 190extern atomic_t fscache_n_no_create_space; 191extern 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 */