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/* SPDX-License-Identifier: GPL-2.0-or-later */ /* General filesystem caching interface * * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * NOTE!!! See: * * Documentation/filesystems/caching/netfs-api.rst * * for a description of the network filesystem interface declared here. */ #ifndef _LINUX_FSCACHE_H #define _LINUX_FSCACHE_H #include <linux/fs.h> #include <linux/netfs.h> #include <linux/writeback.h> #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE) #define __fscache_available (1) #define fscache_available() (1) #define fscache_volume_valid(volume) (volume) #define fscache_cookie_valid(cookie) (cookie) #define fscache_resources_valid(cres) ((cres)->cache_priv) #define fscache_cookie_enabled(cookie) (cookie && !test_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags)) #else #define __fscache_available (0) #define fscache_available() (0) #define fscache_volume_valid(volume) (0) #define fscache_cookie_valid(cookie) (0) #define fscache_resources_valid(cres) (false) #define fscache_cookie_enabled(cookie) (0) #endif struct fscache_cookie; #define FSCACHE_ADV_SINGLE_CHUNK 0x01 /* The object is a single chunk of data */ #define FSCACHE_ADV_WRITE_CACHE 0x00 /* Do cache if written to locally */ #define FSCACHE_ADV_WRITE_NOCACHE 0x02 /* Don't cache if written to locally */ #define FSCACHE_ADV_WANT_CACHE_SIZE 0x04 /* Retrieve cache size at runtime */ #define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */ enum fscache_want_state { FSCACHE_WANT_PARAMS, FSCACHE_WANT_WRITE, FSCACHE_WANT_READ, }; /* * Data object state. */ enum fscache_cookie_state { FSCACHE_COOKIE_STATE_QUIESCENT, /* The cookie is uncached */ FSCACHE_COOKIE_STATE_LOOKING_UP, /* The cache object is being looked up */ FSCACHE_COOKIE_STATE_CREATING, /* The cache object is being created */ FSCACHE_COOKIE_STATE_ACTIVE, /* The cache is active, readable and writable */ FSCACHE_COOKIE_STATE_INVALIDATING, /* The cache is being invalidated */ FSCACHE_COOKIE_STATE_FAILED, /* The cache failed, withdraw to clear */ FSCACHE_COOKIE_STATE_LRU_DISCARDING, /* The cookie is being discarded by the LRU */ FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */ FSCACHE_COOKIE_STATE_RELINQUISHING, /* The cookie is being relinquished */ FSCACHE_COOKIE_STATE_DROPPED, /* The cookie has been dropped */ #define FSCACHE_COOKIE_STATE__NR (FSCACHE_COOKIE_STATE_DROPPED + 1) } __attribute__((mode(byte))); /* * Volume representation cookie. */ struct fscache_volume { refcount_t ref; atomic_t n_cookies; /* Number of data cookies in volume */ atomic_t n_accesses; /* Number of cache accesses in progress */ unsigned int debug_id; unsigned int key_hash; /* Hash of key string */ u8 *key; /* Volume ID, eg. "afs@example.com@1234" */ struct list_head proc_link; /* Link in /proc/fs/fscache/volumes */ struct hlist_bl_node hash_link; /* Link in hash table */ struct work_struct work; struct fscache_cache *cache; /* The cache in which this resides */ void *cache_priv; /* Cache private data */ spinlock_t lock; unsigned long flags; #define FSCACHE_VOLUME_RELINQUISHED 0 /* Volume is being cleaned up */ #define FSCACHE_VOLUME_INVALIDATE 1 /* Volume was invalidated */ #define FSCACHE_VOLUME_COLLIDED_WITH 2 /* Volume was collided with */ #define FSCACHE_VOLUME_ACQUIRE_PENDING 3 /* Volume is waiting to complete acquisition */ #define FSCACHE_VOLUME_CREATING 4 /* Volume is being created on disk */ u8 coherency_len; /* Length of the coherency data */ u8 coherency[]; /* Coherency data */ }; /* * Data file representation cookie. * - a file will only appear in one cache * - a request to cache a file may or may not be honoured, subject to * constraints such as disk space * - indices are created on disk just-in-time */ struct fscache_cookie { refcount_t ref; atomic_t n_active; /* number of active users of cookie */ atomic_t n_accesses; /* Number of cache accesses in progress */ unsigned int debug_id; unsigned int inval_counter; /* Number of invalidations made */ spinlock_t lock; struct fscache_volume *volume; /* Parent volume of this file. */ void *cache_priv; /* Cache-side representation */ struct hlist_bl_node hash_link; /* Link in hash table */ struct list_head proc_link; /* Link in proc list */ struct list_head commit_link; /* Link in commit queue */ struct work_struct work; /* Commit/relinq/withdraw work */ loff_t object_size; /* Size of the netfs object */ unsigned long unused_at; /* Time at which unused (jiffies) */ unsigned long flags; #define FSCACHE_COOKIE_RELINQUISHED 0 /* T if cookie has been relinquished */ #define FSCACHE_COOKIE_RETIRED 1 /* T if this cookie has retired on relinq */ #define FSCACHE_COOKIE_IS_CACHING 2 /* T if this cookie is cached */ #define FSCACHE_COOKIE_NO_DATA_TO_READ 3 /* T if this cookie has nothing to read */ #define FSCACHE_COOKIE_NEEDS_UPDATE 4 /* T if attrs have been updated */ #define FSCACHE_COOKIE_HAS_BEEN_CACHED 5 /* T if cookie needs withdraw-on-relinq */ #define FSCACHE_COOKIE_DISABLED 6 /* T if cookie has been disabled */ #define FSCACHE_COOKIE_LOCAL_WRITE 7 /* T if cookie has been modified locally */ #define FSCACHE_COOKIE_NO_ACCESS_WAKE 8 /* T if no wake when n_accesses goes 0 */ #define FSCACHE_COOKIE_DO_RELINQUISH 9 /* T if this cookie needs relinquishment */ #define FSCACHE_COOKIE_DO_WITHDRAW 10 /* T if this cookie needs withdrawing */ #define FSCACHE_COOKIE_DO_LRU_DISCARD 11 /* T if this cookie needs LRU discard */ #define FSCACHE_COOKIE_DO_PREP_TO_WRITE 12 /* T if cookie needs write preparation */ #define FSCACHE_COOKIE_HAVE_DATA 13 /* T if this cookie has data stored */ #define FSCACHE_COOKIE_IS_HASHED 14 /* T if this cookie is hashed */ #define FSCACHE_COOKIE_DO_INVALIDATE 15 /* T if cookie needs invalidation */ enum fscache_cookie_state state; u8 advice; /* FSCACHE_ADV_* */ u8 key_len; /* Length of index key */ u8 aux_len; /* Length of auxiliary data */ u32 key_hash; /* Hash of volume, key, len */ union { void *key; /* Index key */ u8 inline_key[16]; /* - If the key is short enough */ }; union { void *aux; /* Auxiliary data */ u8 inline_aux[8]; /* - If the aux data is short enough */ }; }; /* * slow-path functions for when there is actually caching available, and the * netfs does actually have a valid token * - these are not to be called directly * - these are undefined symbols when FS-Cache is not configured and the * optimiser takes care of not using them */ extern struct fscache_volume *__fscache_acquire_volume(const char *, const char *, const void *, size_t); extern void __fscache_relinquish_volume(struct fscache_volume *, const void *, bool); extern struct fscache_cookie *__fscache_acquire_cookie( struct fscache_volume *, u8, const void *, size_t, const void *, size_t, loff_t); extern void __fscache_use_cookie(struct fscache_cookie *, bool); extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *); extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool); extern void __fscache_resize_cookie(struct fscache_cookie *, loff_t); extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int); extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *); extern int __fscache_begin_write_operation(struct netfs_cache_resources *, struct fscache_cookie *); void __fscache_write_to_cache(struct fscache_cookie *cookie, struct address_space *mapping, loff_t start, size_t len, loff_t i_size, netfs_io_terminated_t term_func, void *term_func_priv, bool using_pgpriv2, bool cond); extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t); /** * fscache_acquire_volume - Register a volume as desiring caching services * @volume_key: An identification string for the volume * @cache_name: The name of the cache to use (or NULL for the default) * @coherency_data: Piece of arbitrary coherency data to check (or NULL) * @coherency_len: The size of the coherency data * * Register a volume as desiring caching services if they're available. The * caller must provide an identifier for the volume and may also indicate which * cache it should be in. If a preexisting volume entry is found in the cache, * the coherency data must match otherwise the entry will be invalidated. * * Returns a cookie pointer on success, -ENOMEM if out of memory or -EBUSY if a * cache volume of that name is already acquired. Note that "NULL" is a valid * cookie pointer and can be returned if caching is refused. */ static inline struct fscache_volume *fscache_acquire_volume(const char *volume_key, const char *cache_name, const void *coherency_data, size_t coherency_len) { if (!fscache_available()) return NULL; return __fscache_acquire_volume(volume_key, cache_name, coherency_data, coherency_len); } /** * fscache_relinquish_volume - Cease caching a volume * @volume: The volume cookie * @coherency_data: Piece of arbitrary coherency data to set (or NULL) * @invalidate: True if the volume should be invalidated * * Indicate that a filesystem no longer desires caching services for a volume. * The caller must have relinquished all file cookies prior to calling this. * The stored coherency data is updated. */ static inline void fscache_relinquish_volume(struct fscache_volume *volume, const void *coherency_data, bool invalidate) { if (fscache_volume_valid(volume)) __fscache_relinquish_volume(volume, coherency_data, invalidate); } /** * fscache_acquire_cookie - Acquire a cookie to represent a cache object * @volume: The volume in which to locate/create this cookie * @advice: Advice flags (FSCACHE_COOKIE_ADV_*) * @index_key: The index key for this cookie * @index_key_len: Size of the index key * @aux_data: The auxiliary data for the cookie (may be NULL) * @aux_data_len: Size of the auxiliary data buffer * @object_size: The initial size of object * * Acquire a cookie to represent a data file within the given cache volume. * * See Documentation/filesystems/caching/netfs-api.rst for a complete * description. */ static inline struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume, u8 advice, const void *index_key, size_t index_key_len, const void *aux_data, size_t aux_data_len, loff_t object_size) { if (!fscache_volume_valid(volume)) return NULL; return __fscache_acquire_cookie(volume, advice, index_key, index_key_len, aux_data, aux_data_len, object_size); } /** * fscache_use_cookie - Request usage of cookie attached to an object * @cookie: The cookie representing the cache object * @will_modify: If cache is expected to be modified locally * * Request usage of the cookie attached to an object. The caller should tell * the cache if the object's contents are about to be modified locally and then * the cache can apply the policy that has been set to handle this case. */ static inline void fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) { if (fscache_cookie_valid(cookie)) __fscache_use_cookie(cookie, will_modify); } /** * fscache_unuse_cookie - Cease usage of cookie attached to an object * @cookie: The cookie representing the cache object * @aux_data: Updated auxiliary data (or NULL) * @object_size: Revised size of the object (or NULL) * * Cease usage of the cookie attached to an object. When the users count * reaches zero then the cookie relinquishment will be permitted to proceed. */ static inline void fscache_unuse_cookie(struct fscache_cookie *cookie, const void *aux_data, const loff_t *object_size) { if (fscache_cookie_valid(cookie)) __fscache_unuse_cookie(cookie, aux_data, object_size); } /** * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding * it * @cookie: The cookie being returned * @retire: True if the cache object the cookie represents is to be discarded * * This function returns a cookie to the cache, forcibly discarding the * associated cache object if retire is set to true. * * See Documentation/filesystems/caching/netfs-api.rst for a complete * description. */ static inline void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire) { if (fscache_cookie_valid(cookie)) __fscache_relinquish_cookie(cookie, retire); } /* * Find the auxiliary data on a cookie. */ static inline void *fscache_get_aux(struct fscache_cookie *cookie) { if (cookie->aux_len <= sizeof(cookie->inline_aux)) return cookie->inline_aux; else return cookie->aux; } /* * Update the auxiliary data on a cookie. */ static inline void fscache_update_aux(struct fscache_cookie *cookie, const void *aux_data, const loff_t *object_size) { void *p = fscache_get_aux(cookie); if (aux_data && p) memcpy(p, aux_data, cookie->aux_len); if (object_size) cookie->object_size = *object_size; } #ifdef CONFIG_FSCACHE_STATS extern atomic_t fscache_n_updates; #endif static inline void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data, const loff_t *object_size) { #ifdef CONFIG_FSCACHE_STATS atomic_inc(&fscache_n_updates); #endif fscache_update_aux(cookie, aux_data, object_size); smp_wmb(); set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags); } /** * fscache_update_cookie - Request that a cache object be updated * @cookie: The cookie representing the cache object * @aux_data: The updated auxiliary data for the cookie (may be NULL) * @object_size: The current size of the object (may be NULL) * * Request an update of the index data for the cache object associated with the * cookie. The auxiliary data on the cookie will be updated first if @aux_data * is set and the object size will be updated and the object possibly trimmed * if @object_size is set. * * See Documentation/filesystems/caching/netfs-api.rst for a complete * description. */ static inline void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data, const loff_t *object_size) { if (fscache_cookie_enabled(cookie)) __fscache_update_cookie(cookie, aux_data, object_size); } /** * fscache_resize_cookie - Request that a cache object be resized * @cookie: The cookie representing the cache object * @new_size: The new size of the object (may be NULL) * * Request that the size of an object be changed. * * See Documentation/filesystems/caching/netfs-api.rst for a complete * description. */ static inline void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size) { if (fscache_cookie_enabled(cookie)) __fscache_resize_cookie(cookie, new_size); } /** * fscache_invalidate - Notify cache that an object needs invalidation * @cookie: The cookie representing the cache object * @aux_data: The updated auxiliary data for the cookie (may be NULL) * @size: The revised size of the object. * @flags: Invalidation flags (FSCACHE_INVAL_*) * * Notify the cache that an object is needs to be invalidated and that it * should abort any retrievals or stores it is doing on the cache. This * increments inval_counter on the cookie which can be used by the caller to * reconsider I/O requests as they complete. * * If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due * to a direct I/O write and will cause caching to be disabled on this cookie * until it is completely unused. * * See Documentation/filesystems/caching/netfs-api.rst for a complete * description. */ static inline void fscache_invalidate(struct fscache_cookie *cookie, const void *aux_data, loff_t size, unsigned int flags) { if (fscache_cookie_enabled(cookie)) __fscache_invalidate(cookie, aux_data, size, flags); } /** * fscache_operation_valid - Return true if operations resources are usable * @cres: The resources to check. * * Returns a pointer to the operations table if usable or NULL if not. */ static inline const struct netfs_cache_ops *fscache_operation_valid(const struct netfs_cache_resources *cres) { return fscache_resources_valid(cres) ? cres->ops : NULL; } /** * fscache_begin_read_operation - Begin a read operation for the netfs lib * @cres: The cache resources for the read being performed * @cookie: The cookie representing the cache object * * Begin a read operation on behalf of the netfs helper library. @cres * indicates the cache resources to which the operation state should be * attached; @cookie indicates the cache object that will be accessed. * * @cres->inval_counter is set from @cookie->inval_counter for comparison at * the end of the operation. This allows invalidation during the operation to * be detected by the caller. * * Returns: * * 0 - Success * * -ENOBUFS - No caching available * * Other error code from the cache, such as -ENOMEM. */ static inline int fscache_begin_read_operation(struct netfs_cache_resources *cres, struct fscache_cookie *cookie) { if (fscache_cookie_enabled(cookie)) return __fscache_begin_read_operation(cres, cookie); return -ENOBUFS; } /** * fscache_end_operation - End the read operation for the netfs lib * @cres: The cache resources for the read operation * * Clean up the resources at the end of the read request. */ static inline void fscache_end_operation(struct netfs_cache_resources *cres) { const struct netfs_cache_ops *ops = fscache_operation_valid(cres); if (ops) ops->end_operation(cres); } /** * fscache_read - Start a read from the cache. * @cres: The cache resources to use * @start_pos: The beginning file offset in the cache file * @iter: The buffer to fill - and also the length * @read_hole: How to handle a hole in the data. * @term_func: The function to call upon completion * @term_func_priv: The private data for @term_func * * Start a read from the cache. @cres indicates the cache object to read from * and must be obtained by a call to fscache_begin_operation() beforehand. * * The data is read into the iterator, @iter, and that also indicates the size * of the operation. @start_pos is the start position in the file, though if * @seek_data is set appropriately, the cache can use SEEK_DATA to find the * next piece of data, writing zeros for the hole into the iterator. * * Upon termination of the operation, @term_func will be called and supplied * with @term_func_priv plus the amount of data written, if successful, or the * error code otherwise. * * @read_hole indicates how a partially populated region in the cache should be * handled. It can be one of a number of settings: * * NETFS_READ_HOLE_IGNORE - Just try to read (may return a short read). * * NETFS_READ_HOLE_CLEAR - Seek for data, clearing the part of the buffer * skipped over, then do as for IGNORE. * * NETFS_READ_HOLE_FAIL - Give ENODATA if we encounter a hole. */ static inline int fscache_read(struct netfs_cache_resources *cres, loff_t start_pos, struct iov_iter *iter, enum netfs_read_from_hole read_hole, netfs_io_terminated_t term_func, void *term_func_priv) { const struct netfs_cache_ops *ops = fscache_operation_valid(cres); return ops->read(cres, start_pos, iter, read_hole, term_func, term_func_priv); } /** * fscache_begin_write_operation - Begin a write operation for the netfs lib * @cres: The cache resources for the write being performed * @cookie: The cookie representing the cache object * * Begin a write operation on behalf of the netfs helper library. @cres * indicates the cache resources to which the operation state should be * attached; @cookie indicates the cache object that will be accessed. * * @cres->inval_counter is set from @cookie->inval_counter for comparison at * the end of the operation. This allows invalidation during the operation to * be detected by the caller. * * Returns: * * 0 - Success * * -ENOBUFS - No caching available * * Other error code from the cache, such as -ENOMEM. */ static inline int fscache_begin_write_operation(struct netfs_cache_resources *cres, struct fscache_cookie *cookie) { if (fscache_cookie_enabled(cookie)) return __fscache_begin_write_operation(cres, cookie); return -ENOBUFS; } /** * fscache_write - Start a write to the cache. * @cres: The cache resources to use * @start_pos: The beginning file offset in the cache file * @iter: The data to write - and also the length * @term_func: The function to call upon completion * @term_func_priv: The private data for @term_func * * Start a write to the cache. @cres indicates the cache object to write to and * must be obtained by a call to fscache_begin_operation() beforehand. * * The data to be written is obtained from the iterator, @iter, and that also * indicates the size of the operation. @start_pos is the start position in * the file. * * Upon termination of the operation, @term_func will be called and supplied * with @term_func_priv plus the amount of data written, if successful, or the * error code otherwise. */ static inline int fscache_write(struct netfs_cache_resources *cres, loff_t start_pos, struct iov_iter *iter, netfs_io_terminated_t term_func, void *term_func_priv) { const struct netfs_cache_ops *ops = fscache_operation_valid(cres); return ops->write(cres, start_pos, iter, term_func, term_func_priv); } /** * fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages * @mapping: The netfs inode to use as the source * @start: The start position in @mapping * @len: The amount of data to unlock * @caching: If PG_fscache has been set * * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's * waiting. */ static inline void fscache_clear_page_bits(struct address_space *mapping, loff_t start, size_t len, bool caching) { if (caching) __fscache_clear_page_bits(mapping, start, len); } /** * fscache_write_to_cache - Save a write to the cache and clear PG_fscache * @cookie: The cookie representing the cache object * @mapping: The netfs inode to use as the source * @start: The start position in @mapping * @len: The amount of data to write back * @i_size: The new size of the inode * @term_func: The function to call upon completion * @term_func_priv: The private data for @term_func * @using_pgpriv2: If we're using PG_private_2 to mark in-progress write * @caching: If we actually want to do the caching * * Helper function for a netfs to write dirty data from an inode into the cache * object that's backing it. * * @start and @len describe the range of the data. This does not need to be * page-aligned, but to satisfy DIO requirements, the cache may expand it up to * the page boundaries on either end. All the pages covering the range must be * marked with PG_fscache. * * If given, @term_func will be called upon completion and supplied with * @term_func_priv. Note that if @using_pgpriv2 is set, the PG_private_2 flags * will have been cleared by this point, so the netfs must retain its own pin * on the mapping. */ static inline void fscache_write_to_cache(struct fscache_cookie *cookie, struct address_space *mapping, loff_t start, size_t len, loff_t i_size, netfs_io_terminated_t term_func, void *term_func_priv, bool using_pgpriv2, bool caching) { if (caching) __fscache_write_to_cache(cookie, mapping, start, len, i_size, term_func, term_func_priv, using_pgpriv2, caching); else if (term_func) term_func(term_func_priv, -ENOBUFS); } /** * fscache_note_page_release - Note that a netfs page got released * @cookie: The cookie corresponding to the file * * Note that a page that has been copied to the cache has been released. This * means that future reads will need to look in the cache to see if it's there. */ static inline void fscache_note_page_release(struct fscache_cookie *cookie) { /* If we've written data to the cache (HAVE_DATA) and there wasn't any * data in the cache when we started (NO_DATA_TO_READ), it may no * longer be true that we can skip reading from the cache - so clear * the flag that causes reads to be skipped. */ if (cookie && test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) && test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags); } #endif /* _LINUX_FSCACHE_H */