1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /* General filesystem caching backing cache interface
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
9 * Documentation/filesystems/caching/backend-api.rst
11 * for a description of the cache backend interface declared here.
14 #ifndef _LINUX_FSCACHE_CACHE_H
15 #define _LINUX_FSCACHE_CACHE_H
17 #include <linux/fscache.h>
19 enum fscache_cache_trace;
20 enum fscache_cookie_trace;
21 enum fscache_access_trace;
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28 FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */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)
35 struct fscache_cache {
36 struct list_head cache_link; /* Link in cache list */
37 void *cache_priv; /* Private cache data (or NULL) */
39 atomic_t n_volumes; /* Number of active volumes; */
40 atomic_t n_accesses; /* Number of in-progress accesses on the cache */
41 atomic_t object_count; /* no. of live objects in this cache */
42 unsigned int debug_id;
43 enum fscache_cache_state state;
47 extern struct workqueue_struct *fscache_wq;
50 * out-of-line cache backend functions
52 extern struct rw_semaphore fscache_addremove_sem;
53 extern struct fscache_cache *fscache_acquire_cache(const char *name);
54 extern void fscache_relinquish_cache(struct fscache_cache *cache);
56 extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
57 enum fscache_cookie_trace where);
58 extern void fscache_put_cookie(struct fscache_cookie *cookie,
59 enum fscache_cookie_trace where);
60 extern void fscache_set_cookie_state(struct fscache_cookie *cookie,
61 enum fscache_cookie_state state);
64 * fscache_get_key - Get a pointer to the cookie key
65 * @cookie: The cookie to query
67 * Return a pointer to the where a cookie's key is stored.
69 static inline void *fscache_get_key(struct fscache_cookie *cookie)
71 if (cookie->key_len <= sizeof(cookie->inline_key))
72 return cookie->inline_key;
77 #endif /* _LINUX_FSCACHE_CACHE_H */