206 lines
6.7 KiB
C
206 lines
6.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/* General filesystem caching backing cache interface
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* NOTE!!! See:
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*
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* Documentation/filesystems/caching/backend-api.rst
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*
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* for a description of the cache backend interface declared here.
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*/
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#ifndef _LINUX_FSCACHE_CACHE_H
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#define _LINUX_FSCACHE_CACHE_H
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#include <linux/fscache.h>
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enum fscache_cache_trace;
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enum fscache_cookie_trace;
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enum fscache_access_trace;
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enum fscache_cache_state {
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FSCACHE_CACHE_IS_NOT_PRESENT, /* No cache is present for this name */
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FSCACHE_CACHE_IS_PREPARING, /* A cache is preparing to come live */
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FSCACHE_CACHE_IS_ACTIVE, /* Attached cache is active and can be used */
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FSCACHE_CACHE_GOT_IOERROR, /* Attached cache stopped on I/O error */
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FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */
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#define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1)
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};
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/*
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* Cache cookie.
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*/
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struct fscache_cache {
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const struct fscache_cache_ops *ops;
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struct list_head cache_link; /* Link in cache list */
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void *cache_priv; /* Private cache data (or NULL) */
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refcount_t ref;
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atomic_t n_volumes; /* Number of active volumes; */
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atomic_t n_accesses; /* Number of in-progress accesses on the cache */
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atomic_t object_count; /* no. of live objects in this cache */
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unsigned int debug_id;
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enum fscache_cache_state state;
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char *name;
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};
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/*
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* cache operations
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*/
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struct fscache_cache_ops {
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/* name of cache provider */
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const char *name;
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/* Acquire a volume */
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void (*acquire_volume)(struct fscache_volume *volume);
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/* Free the cache's data attached to a volume */
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void (*free_volume)(struct fscache_volume *volume);
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/* Look up a cookie in the cache */
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bool (*lookup_cookie)(struct fscache_cookie *cookie);
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/* Withdraw an object without any cookie access counts held */
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void (*withdraw_cookie)(struct fscache_cookie *cookie);
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/* Change the size of a data object */
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void (*resize_cookie)(struct netfs_cache_resources *cres,
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loff_t new_size);
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/* Invalidate an object */
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bool (*invalidate_cookie)(struct fscache_cookie *cookie);
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/* Begin an operation for the netfs lib */
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bool (*begin_operation)(struct netfs_cache_resources *cres,
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enum fscache_want_state want_state);
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/* Prepare to write to a live cache object */
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void (*prepare_to_write)(struct fscache_cookie *cookie);
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};
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extern struct workqueue_struct *fscache_wq;
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extern wait_queue_head_t fscache_clearance_waiters;
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/*
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* out-of-line cache backend functions
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*/
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extern struct rw_semaphore fscache_addremove_sem;
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extern struct fscache_cache *fscache_acquire_cache(const char *name);
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extern void fscache_relinquish_cache(struct fscache_cache *cache);
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extern int fscache_add_cache(struct fscache_cache *cache,
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const struct fscache_cache_ops *ops,
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void *cache_priv);
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extern void fscache_withdraw_cache(struct fscache_cache *cache);
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extern void fscache_withdraw_volume(struct fscache_volume *volume);
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extern void fscache_withdraw_cookie(struct fscache_cookie *cookie);
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extern void fscache_io_error(struct fscache_cache *cache);
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extern void fscache_end_volume_access(struct fscache_volume *volume,
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struct fscache_cookie *cookie,
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enum fscache_access_trace why);
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extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
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enum fscache_cookie_trace where);
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extern void fscache_put_cookie(struct fscache_cookie *cookie,
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enum fscache_cookie_trace where);
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extern void fscache_end_cookie_access(struct fscache_cookie *cookie,
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enum fscache_access_trace why);
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extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie);
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extern void fscache_resume_after_invalidation(struct fscache_cookie *cookie);
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extern void fscache_caching_failed(struct fscache_cookie *cookie);
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extern bool fscache_wait_for_operation(struct netfs_cache_resources *cred,
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enum fscache_want_state state);
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/**
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* fscache_cookie_state - Read the state of a cookie
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* @cookie: The cookie to query
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*
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* Get the state of a cookie, imposing an ordering between the cookie contents
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* and the state value. Paired with fscache_set_cookie_state().
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*/
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static inline
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enum fscache_cookie_state fscache_cookie_state(struct fscache_cookie *cookie)
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{
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return smp_load_acquire(&cookie->state);
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}
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/**
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* fscache_get_key - Get a pointer to the cookie key
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* @cookie: The cookie to query
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*
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* Return a pointer to the where a cookie's key is stored.
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*/
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static inline void *fscache_get_key(struct fscache_cookie *cookie)
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{
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if (cookie->key_len <= sizeof(cookie->inline_key))
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return cookie->inline_key;
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else
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return cookie->key;
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}
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static inline struct fscache_cookie *fscache_cres_cookie(struct netfs_cache_resources *cres)
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{
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return cres->cache_priv;
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}
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/**
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* fscache_count_object - Tell fscache that an object has been added
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* @cache: The cache to account to
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*
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* Tell fscache that an object has been added to the cache. This prevents the
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* cache from tearing down the cache structure until the object is uncounted.
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*/
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static inline void fscache_count_object(struct fscache_cache *cache)
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{
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atomic_inc(&cache->object_count);
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}
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/**
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* fscache_uncount_object - Tell fscache that an object has been removed
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* @cache: The cache to account to
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*
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* Tell fscache that an object has been removed from the cache and will no
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* longer be accessed. After this point, the cache cookie may be destroyed.
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*/
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static inline void fscache_uncount_object(struct fscache_cache *cache)
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{
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if (atomic_dec_and_test(&cache->object_count))
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wake_up_all(&fscache_clearance_waiters);
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}
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/**
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* fscache_wait_for_objects - Wait for all objects to be withdrawn
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* @cache: The cache to query
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*
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* Wait for all extant objects in a cache to finish being withdrawn
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* and go away.
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*/
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static inline void fscache_wait_for_objects(struct fscache_cache *cache)
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{
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wait_event(fscache_clearance_waiters,
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atomic_read(&cache->object_count) == 0);
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}
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#ifdef CONFIG_FSCACHE_STATS
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extern atomic_t fscache_n_read;
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extern atomic_t fscache_n_write;
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extern atomic_t fscache_n_no_write_space;
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extern atomic_t fscache_n_no_create_space;
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extern atomic_t fscache_n_culled;
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#define fscache_count_read() atomic_inc(&fscache_n_read)
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#define fscache_count_write() atomic_inc(&fscache_n_write)
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#define fscache_count_no_write_space() atomic_inc(&fscache_n_no_write_space)
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#define fscache_count_no_create_space() atomic_inc(&fscache_n_no_create_space)
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#define fscache_count_culled() atomic_inc(&fscache_n_culled)
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#else
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#define fscache_count_read() do {} while(0)
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#define fscache_count_write() do {} while(0)
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#define fscache_count_no_write_space() do {} while(0)
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#define fscache_count_no_create_space() do {} while(0)
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#define fscache_count_culled() do {} while(0)
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#endif
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#endif /* _LINUX_FSCACHE_CACHE_H */
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