1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /* General filesystem caching interface
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
9 * Documentation/filesystems/caching/netfs-api.rst
11 * for a description of the network filesystem interface declared here.
14 #ifndef _LINUX_FSCACHE_H
15 #define _LINUX_FSCACHE_H
18 #include <linux/netfs.h>
19 #include <linux/writeback.h>
21 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
22 #define __fscache_available (1)
23 #define fscache_available() (1)
24 #define fscache_volume_valid(volume) (volume)
25 #define fscache_cookie_valid(cookie) (cookie)
26 #define fscache_resources_valid(cres) ((cres)->cache_priv)
27 #define fscache_cookie_enabled(cookie) (cookie && !test_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
29 #define __fscache_available (0)
30 #define fscache_available() (0)
31 #define fscache_volume_valid(volume) (0)
32 #define fscache_cookie_valid(cookie) (0)
33 #define fscache_resources_valid(cres) (false)
34 #define fscache_cookie_enabled(cookie) (0)
37 struct fscache_cookie;
39 #define FSCACHE_ADV_SINGLE_CHUNK 0x01 /* The object is a single chunk of data */
40 #define FSCACHE_ADV_WRITE_CACHE 0x00 /* Do cache if written to locally */
41 #define FSCACHE_ADV_WRITE_NOCACHE 0x02 /* Don't cache if written to locally */
42 #define FSCACHE_ADV_WANT_CACHE_SIZE 0x04 /* Retrieve cache size at runtime */
44 #define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */
46 enum fscache_want_state {
55 enum fscache_cookie_state {
56 FSCACHE_COOKIE_STATE_QUIESCENT, /* The cookie is uncached */
57 FSCACHE_COOKIE_STATE_LOOKING_UP, /* The cache object is being looked up */
58 FSCACHE_COOKIE_STATE_CREATING, /* The cache object is being created */
59 FSCACHE_COOKIE_STATE_ACTIVE, /* The cache is active, readable and writable */
60 FSCACHE_COOKIE_STATE_INVALIDATING, /* The cache is being invalidated */
61 FSCACHE_COOKIE_STATE_FAILED, /* The cache failed, withdraw to clear */
62 FSCACHE_COOKIE_STATE_LRU_DISCARDING, /* The cookie is being discarded by the LRU */
63 FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */
64 FSCACHE_COOKIE_STATE_RELINQUISHING, /* The cookie is being relinquished */
65 FSCACHE_COOKIE_STATE_DROPPED, /* The cookie has been dropped */
66 #define FSCACHE_COOKIE_STATE__NR (FSCACHE_COOKIE_STATE_DROPPED + 1)
67 } __attribute__((mode(byte)));
70 * Volume representation cookie.
72 struct fscache_volume {
74 atomic_t n_cookies; /* Number of data cookies in volume */
75 atomic_t n_accesses; /* Number of cache accesses in progress */
76 unsigned int debug_id;
77 unsigned int key_hash; /* Hash of key string */
78 char *key; /* Volume ID, eg. "afs@example.com@1234" */
79 struct list_head proc_link; /* Link in /proc/fs/fscache/volumes */
80 struct hlist_bl_node hash_link; /* Link in hash table */
81 struct work_struct work;
82 struct fscache_cache *cache; /* The cache in which this resides */
83 void *cache_priv; /* Cache private data */
86 #define FSCACHE_VOLUME_RELINQUISHED 0 /* Volume is being cleaned up */
87 #define FSCACHE_VOLUME_INVALIDATE 1 /* Volume was invalidated */
88 #define FSCACHE_VOLUME_COLLIDED_WITH 2 /* Volume was collided with */
89 #define FSCACHE_VOLUME_ACQUIRE_PENDING 3 /* Volume is waiting to complete acquisition */
90 #define FSCACHE_VOLUME_CREATING 4 /* Volume is being created on disk */
91 u8 coherency_len; /* Length of the coherency data */
92 u8 coherency[]; /* Coherency data */
96 * Data file representation cookie.
97 * - a file will only appear in one cache
98 * - a request to cache a file may or may not be honoured, subject to
99 * constraints such as disk space
100 * - indices are created on disk just-in-time
102 struct fscache_cookie {
104 atomic_t n_active; /* number of active users of cookie */
105 atomic_t n_accesses; /* Number of cache accesses in progress */
106 unsigned int debug_id;
107 unsigned int inval_counter; /* Number of invalidations made */
109 struct fscache_volume *volume; /* Parent volume of this file. */
110 void *cache_priv; /* Cache-side representation */
111 struct hlist_bl_node hash_link; /* Link in hash table */
112 struct list_head proc_link; /* Link in proc list */
113 struct list_head commit_link; /* Link in commit queue */
114 struct work_struct work; /* Commit/relinq/withdraw work */
115 loff_t object_size; /* Size of the netfs object */
116 unsigned long unused_at; /* Time at which unused (jiffies) */
118 #define FSCACHE_COOKIE_RELINQUISHED 0 /* T if cookie has been relinquished */
119 #define FSCACHE_COOKIE_RETIRED 1 /* T if this cookie has retired on relinq */
120 #define FSCACHE_COOKIE_IS_CACHING 2 /* T if this cookie is cached */
121 #define FSCACHE_COOKIE_NO_DATA_TO_READ 3 /* T if this cookie has nothing to read */
122 #define FSCACHE_COOKIE_NEEDS_UPDATE 4 /* T if attrs have been updated */
123 #define FSCACHE_COOKIE_HAS_BEEN_CACHED 5 /* T if cookie needs withdraw-on-relinq */
124 #define FSCACHE_COOKIE_DISABLED 6 /* T if cookie has been disabled */
125 #define FSCACHE_COOKIE_LOCAL_WRITE 7 /* T if cookie has been modified locally */
126 #define FSCACHE_COOKIE_NO_ACCESS_WAKE 8 /* T if no wake when n_accesses goes 0 */
127 #define FSCACHE_COOKIE_DO_RELINQUISH 9 /* T if this cookie needs relinquishment */
128 #define FSCACHE_COOKIE_DO_WITHDRAW 10 /* T if this cookie needs withdrawing */
129 #define FSCACHE_COOKIE_DO_LRU_DISCARD 11 /* T if this cookie needs LRU discard */
130 #define FSCACHE_COOKIE_DO_PREP_TO_WRITE 12 /* T if cookie needs write preparation */
131 #define FSCACHE_COOKIE_HAVE_DATA 13 /* T if this cookie has data stored */
132 #define FSCACHE_COOKIE_IS_HASHED 14 /* T if this cookie is hashed */
134 enum fscache_cookie_state state;
135 u8 advice; /* FSCACHE_ADV_* */
136 u8 key_len; /* Length of index key */
137 u8 aux_len; /* Length of auxiliary data */
138 u32 key_hash; /* Hash of volume, key, len */
140 void *key; /* Index key */
141 u8 inline_key[16]; /* - If the key is short enough */
144 void *aux; /* Auxiliary data */
145 u8 inline_aux[8]; /* - If the aux data is short enough */
150 * slow-path functions for when there is actually caching available, and the
151 * netfs does actually have a valid token
152 * - these are not to be called directly
153 * - these are undefined symbols when FS-Cache is not configured and the
154 * optimiser takes care of not using them
156 extern struct fscache_volume *__fscache_acquire_volume(const char *, const char *,
157 const void *, size_t);
158 extern void __fscache_relinquish_volume(struct fscache_volume *, const void *, bool);
160 extern struct fscache_cookie *__fscache_acquire_cookie(
161 struct fscache_volume *,
163 const void *, size_t,
164 const void *, size_t,
166 extern void __fscache_use_cookie(struct fscache_cookie *, bool);
167 extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *);
168 extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
169 extern void __fscache_resize_cookie(struct fscache_cookie *, loff_t);
170 extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);
171 extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
172 extern int __fscache_begin_write_operation(struct netfs_cache_resources *, struct fscache_cookie *);
174 extern void __fscache_write_to_cache(struct fscache_cookie *, struct address_space *,
175 loff_t, size_t, loff_t, netfs_io_terminated_t, void *,
177 extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t);
180 * fscache_acquire_volume - Register a volume as desiring caching services
181 * @volume_key: An identification string for the volume
182 * @cache_name: The name of the cache to use (or NULL for the default)
183 * @coherency_data: Piece of arbitrary coherency data to check (or NULL)
184 * @coherency_len: The size of the coherency data
186 * Register a volume as desiring caching services if they're available. The
187 * caller must provide an identifier for the volume and may also indicate which
188 * cache it should be in. If a preexisting volume entry is found in the cache,
189 * the coherency data must match otherwise the entry will be invalidated.
191 * Returns a cookie pointer on success, -ENOMEM if out of memory or -EBUSY if a
192 * cache volume of that name is already acquired. Note that "NULL" is a valid
193 * cookie pointer and can be returned if caching is refused.
196 struct fscache_volume *fscache_acquire_volume(const char *volume_key,
197 const char *cache_name,
198 const void *coherency_data,
199 size_t coherency_len)
201 if (!fscache_available())
203 return __fscache_acquire_volume(volume_key, cache_name,
204 coherency_data, coherency_len);
208 * fscache_relinquish_volume - Cease caching a volume
209 * @volume: The volume cookie
210 * @coherency_data: Piece of arbitrary coherency data to set (or NULL)
211 * @invalidate: True if the volume should be invalidated
213 * Indicate that a filesystem no longer desires caching services for a volume.
214 * The caller must have relinquished all file cookies prior to calling this.
215 * The stored coherency data is updated.
218 void fscache_relinquish_volume(struct fscache_volume *volume,
219 const void *coherency_data,
222 if (fscache_volume_valid(volume))
223 __fscache_relinquish_volume(volume, coherency_data, invalidate);
227 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
228 * @volume: The volume in which to locate/create this cookie
229 * @advice: Advice flags (FSCACHE_COOKIE_ADV_*)
230 * @index_key: The index key for this cookie
231 * @index_key_len: Size of the index key
232 * @aux_data: The auxiliary data for the cookie (may be NULL)
233 * @aux_data_len: Size of the auxiliary data buffer
234 * @object_size: The initial size of object
236 * Acquire a cookie to represent a data file within the given cache volume.
238 * See Documentation/filesystems/caching/netfs-api.rst for a complete
242 struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume,
244 const void *index_key,
245 size_t index_key_len,
246 const void *aux_data,
250 if (!fscache_volume_valid(volume))
252 return __fscache_acquire_cookie(volume, advice,
253 index_key, index_key_len,
254 aux_data, aux_data_len,
259 * fscache_use_cookie - Request usage of cookie attached to an object
260 * @object: Object description
261 * @will_modify: If cache is expected to be modified locally
263 * Request usage of the cookie attached to an object. The caller should tell
264 * the cache if the object's contents are about to be modified locally and then
265 * the cache can apply the policy that has been set to handle this case.
267 static inline void fscache_use_cookie(struct fscache_cookie *cookie,
270 if (fscache_cookie_valid(cookie))
271 __fscache_use_cookie(cookie, will_modify);
275 * fscache_unuse_cookie - Cease usage of cookie attached to an object
276 * @object: Object description
277 * @aux_data: Updated auxiliary data (or NULL)
278 * @object_size: Revised size of the object (or NULL)
280 * Cease usage of the cookie attached to an object. When the users count
281 * reaches zero then the cookie relinquishment will be permitted to proceed.
283 static inline void fscache_unuse_cookie(struct fscache_cookie *cookie,
284 const void *aux_data,
285 const loff_t *object_size)
287 if (fscache_cookie_valid(cookie))
288 __fscache_unuse_cookie(cookie, aux_data, object_size);
292 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
294 * @cookie: The cookie being returned
295 * @retire: True if the cache object the cookie represents is to be discarded
297 * This function returns a cookie to the cache, forcibly discarding the
298 * associated cache object if retire is set to true.
300 * See Documentation/filesystems/caching/netfs-api.rst for a complete
304 void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
306 if (fscache_cookie_valid(cookie))
307 __fscache_relinquish_cookie(cookie, retire);
311 * Find the auxiliary data on a cookie.
313 static inline void *fscache_get_aux(struct fscache_cookie *cookie)
315 if (cookie->aux_len <= sizeof(cookie->inline_aux))
316 return cookie->inline_aux;
322 * Update the auxiliary data on a cookie.
325 void fscache_update_aux(struct fscache_cookie *cookie,
326 const void *aux_data, const loff_t *object_size)
328 void *p = fscache_get_aux(cookie);
331 memcpy(p, aux_data, cookie->aux_len);
333 cookie->object_size = *object_size;
336 #ifdef CONFIG_FSCACHE_STATS
337 extern atomic_t fscache_n_updates;
341 void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
342 const loff_t *object_size)
344 #ifdef CONFIG_FSCACHE_STATS
345 atomic_inc(&fscache_n_updates);
347 fscache_update_aux(cookie, aux_data, object_size);
349 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
353 * fscache_update_cookie - Request that a cache object be updated
354 * @cookie: The cookie representing the cache object
355 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
356 * @object_size: The current size of the object (may be NULL)
358 * Request an update of the index data for the cache object associated with the
359 * cookie. The auxiliary data on the cookie will be updated first if @aux_data
360 * is set and the object size will be updated and the object possibly trimmed
361 * if @object_size is set.
363 * See Documentation/filesystems/caching/netfs-api.rst for a complete
367 void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
368 const loff_t *object_size)
370 if (fscache_cookie_enabled(cookie))
371 __fscache_update_cookie(cookie, aux_data, object_size);
375 * fscache_resize_cookie - Request that a cache object be resized
376 * @cookie: The cookie representing the cache object
377 * @new_size: The new size of the object (may be NULL)
379 * Request that the size of an object be changed.
381 * See Documentation/filesystems/caching/netfs-api.txt for a complete
385 void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
387 if (fscache_cookie_enabled(cookie))
388 __fscache_resize_cookie(cookie, new_size);
392 * fscache_invalidate - Notify cache that an object needs invalidation
393 * @cookie: The cookie representing the cache object
394 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
395 * @size: The revised size of the object.
396 * @flags: Invalidation flags (FSCACHE_INVAL_*)
398 * Notify the cache that an object is needs to be invalidated and that it
399 * should abort any retrievals or stores it is doing on the cache. This
400 * increments inval_counter on the cookie which can be used by the caller to
401 * reconsider I/O requests as they complete.
403 * If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due
404 * to a direct I/O write and will cause caching to be disabled on this cookie
405 * until it is completely unused.
407 * See Documentation/filesystems/caching/netfs-api.rst for a complete
411 void fscache_invalidate(struct fscache_cookie *cookie,
412 const void *aux_data, loff_t size, unsigned int flags)
414 if (fscache_cookie_enabled(cookie))
415 __fscache_invalidate(cookie, aux_data, size, flags);
419 * fscache_operation_valid - Return true if operations resources are usable
420 * @cres: The resources to check.
422 * Returns a pointer to the operations table if usable or NULL if not.
425 const struct netfs_cache_ops *fscache_operation_valid(const struct netfs_cache_resources *cres)
427 return fscache_resources_valid(cres) ? cres->ops : NULL;
431 * fscache_begin_read_operation - Begin a read operation for the netfs lib
432 * @cres: The cache resources for the read being performed
433 * @cookie: The cookie representing the cache object
435 * Begin a read operation on behalf of the netfs helper library. @cres
436 * indicates the cache resources to which the operation state should be
437 * attached; @cookie indicates the cache object that will be accessed.
439 * This is intended to be called from the ->begin_cache_operation() netfs lib
440 * operation as implemented by the network filesystem.
442 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
443 * the end of the operation. This allows invalidation during the operation to
444 * be detected by the caller.
448 * * -ENOBUFS - No caching available
449 * * Other error code from the cache, such as -ENOMEM.
452 int fscache_begin_read_operation(struct netfs_cache_resources *cres,
453 struct fscache_cookie *cookie)
455 if (fscache_cookie_enabled(cookie))
456 return __fscache_begin_read_operation(cres, cookie);
461 * fscache_end_operation - End the read operation for the netfs lib
462 * @cres: The cache resources for the read operation
464 * Clean up the resources at the end of the read request.
466 static inline void fscache_end_operation(struct netfs_cache_resources *cres)
468 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
471 ops->end_operation(cres);
475 * fscache_read - Start a read from the cache.
476 * @cres: The cache resources to use
477 * @start_pos: The beginning file offset in the cache file
478 * @iter: The buffer to fill - and also the length
479 * @read_hole: How to handle a hole in the data.
480 * @term_func: The function to call upon completion
481 * @term_func_priv: The private data for @term_func
483 * Start a read from the cache. @cres indicates the cache object to read from
484 * and must be obtained by a call to fscache_begin_operation() beforehand.
486 * The data is read into the iterator, @iter, and that also indicates the size
487 * of the operation. @start_pos is the start position in the file, though if
488 * @seek_data is set appropriately, the cache can use SEEK_DATA to find the
489 * next piece of data, writing zeros for the hole into the iterator.
491 * Upon termination of the operation, @term_func will be called and supplied
492 * with @term_func_priv plus the amount of data written, if successful, or the
493 * error code otherwise.
495 * @read_hole indicates how a partially populated region in the cache should be
496 * handled. It can be one of a number of settings:
498 * NETFS_READ_HOLE_IGNORE - Just try to read (may return a short read).
500 * NETFS_READ_HOLE_CLEAR - Seek for data, clearing the part of the buffer
501 * skipped over, then do as for IGNORE.
503 * NETFS_READ_HOLE_FAIL - Give ENODATA if we encounter a hole.
506 int fscache_read(struct netfs_cache_resources *cres,
508 struct iov_iter *iter,
509 enum netfs_read_from_hole read_hole,
510 netfs_io_terminated_t term_func,
511 void *term_func_priv)
513 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
514 return ops->read(cres, start_pos, iter, read_hole,
515 term_func, term_func_priv);
519 * fscache_begin_write_operation - Begin a write operation for the netfs lib
520 * @cres: The cache resources for the write being performed
521 * @cookie: The cookie representing the cache object
523 * Begin a write operation on behalf of the netfs helper library. @cres
524 * indicates the cache resources to which the operation state should be
525 * attached; @cookie indicates the cache object that will be accessed.
527 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
528 * the end of the operation. This allows invalidation during the operation to
529 * be detected by the caller.
533 * * -ENOBUFS - No caching available
534 * * Other error code from the cache, such as -ENOMEM.
537 int fscache_begin_write_operation(struct netfs_cache_resources *cres,
538 struct fscache_cookie *cookie)
540 if (fscache_cookie_enabled(cookie))
541 return __fscache_begin_write_operation(cres, cookie);
546 * fscache_write - Start a write to the cache.
547 * @cres: The cache resources to use
548 * @start_pos: The beginning file offset in the cache file
549 * @iter: The data to write - and also the length
550 * @term_func: The function to call upon completion
551 * @term_func_priv: The private data for @term_func
553 * Start a write to the cache. @cres indicates the cache object to write to and
554 * must be obtained by a call to fscache_begin_operation() beforehand.
556 * The data to be written is obtained from the iterator, @iter, and that also
557 * indicates the size of the operation. @start_pos is the start position in
560 * Upon termination of the operation, @term_func will be called and supplied
561 * with @term_func_priv plus the amount of data written, if successful, or the
562 * error code otherwise.
565 int fscache_write(struct netfs_cache_resources *cres,
567 struct iov_iter *iter,
568 netfs_io_terminated_t term_func,
569 void *term_func_priv)
571 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
572 return ops->write(cres, start_pos, iter, term_func, term_func_priv);
576 * fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages
577 * @mapping: The netfs inode to use as the source
578 * @start: The start position in @mapping
579 * @len: The amount of data to unlock
580 * @caching: If PG_fscache has been set
582 * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's
585 static inline void fscache_clear_page_bits(struct address_space *mapping,
586 loff_t start, size_t len,
590 __fscache_clear_page_bits(mapping, start, len);
594 * fscache_write_to_cache - Save a write to the cache and clear PG_fscache
595 * @cookie: The cookie representing the cache object
596 * @mapping: The netfs inode to use as the source
597 * @start: The start position in @mapping
598 * @len: The amount of data to write back
599 * @i_size: The new size of the inode
600 * @term_func: The function to call upon completion
601 * @term_func_priv: The private data for @term_func
602 * @caching: If PG_fscache has been set
604 * Helper function for a netfs to write dirty data from an inode into the cache
605 * object that's backing it.
607 * @start and @len describe the range of the data. This does not need to be
608 * page-aligned, but to satisfy DIO requirements, the cache may expand it up to
609 * the page boundaries on either end. All the pages covering the range must be
610 * marked with PG_fscache.
612 * If given, @term_func will be called upon completion and supplied with
613 * @term_func_priv. Note that the PG_fscache flags will have been cleared by
614 * this point, so the netfs must retain its own pin on the mapping.
616 static inline void fscache_write_to_cache(struct fscache_cookie *cookie,
617 struct address_space *mapping,
618 loff_t start, size_t len, loff_t i_size,
619 netfs_io_terminated_t term_func,
620 void *term_func_priv,
624 __fscache_write_to_cache(cookie, mapping, start, len, i_size,
625 term_func, term_func_priv, caching);
627 term_func(term_func_priv, -ENOBUFS, false);
631 #if __fscache_available
632 bool fscache_dirty_folio(struct address_space *mapping, struct folio *folio,
633 struct fscache_cookie *cookie);
635 #define fscache_dirty_folio(MAPPING, FOLIO, COOKIE) \
636 filemap_dirty_folio(MAPPING, FOLIO)
640 * fscache_unpin_writeback - Unpin writeback resources
641 * @wbc: The writeback control
642 * @cookie: The cookie referring to the cache object
644 * Unpin the writeback resources pinned by fscache_dirty_folio(). This is
645 * intended to be called by the netfs's ->write_inode() method.
647 static inline void fscache_unpin_writeback(struct writeback_control *wbc,
648 struct fscache_cookie *cookie)
650 if (wbc->unpinned_fscache_wb)
651 fscache_unuse_cookie(cookie, NULL, NULL);
655 * fscache_clear_inode_writeback - Clear writeback resources pinned by an inode
656 * @cookie: The cookie referring to the cache object
657 * @inode: The inode to clean up
658 * @aux: Auxiliary data to apply to the inode
660 * Clear any writeback resources held by an inode when the inode is evicted.
661 * This must be called before clear_inode() is called.
663 static inline void fscache_clear_inode_writeback(struct fscache_cookie *cookie,
667 if (inode->i_state & I_PINNING_FSCACHE_WB) {
668 loff_t i_size = i_size_read(inode);
669 fscache_unuse_cookie(cookie, aux, &i_size);
674 * fscache_note_page_release - Note that a netfs page got released
675 * @cookie: The cookie corresponding to the file
677 * Note that a page that has been copied to the cache has been released. This
678 * means that future reads will need to look in the cache to see if it's there.
681 void fscache_note_page_release(struct fscache_cookie *cookie)
683 /* If we've written data to the cache (HAVE_DATA) and there wasn't any
684 * data in the cache when we started (NO_DATA_TO_READ), it may no
685 * longer be true that we can skip reading from the cache - so clear
686 * the flag that causes reads to be skipped.
689 test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) &&
690 test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags))
691 clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
694 #endif /* _LINUX_FSCACHE_H */