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 */
43 #define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */
45 enum fscache_want_state {
54 enum fscache_cookie_state {
55 FSCACHE_COOKIE_STATE_QUIESCENT, /* The cookie is uncached */
56 FSCACHE_COOKIE_STATE_LOOKING_UP, /* The cache object is being looked up */
57 FSCACHE_COOKIE_STATE_CREATING, /* The cache object is being created */
58 FSCACHE_COOKIE_STATE_ACTIVE, /* The cache is active, readable and writable */
59 FSCACHE_COOKIE_STATE_INVALIDATING, /* The cache is being invalidated */
60 FSCACHE_COOKIE_STATE_FAILED, /* The cache failed, withdraw to clear */
61 FSCACHE_COOKIE_STATE_LRU_DISCARDING, /* The cookie is being discarded by the LRU */
62 FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */
63 FSCACHE_COOKIE_STATE_RELINQUISHING, /* The cookie is being relinquished */
64 FSCACHE_COOKIE_STATE_DROPPED, /* The cookie has been dropped */
65 #define FSCACHE_COOKIE_STATE__NR (FSCACHE_COOKIE_STATE_DROPPED + 1)
66 } __attribute__((mode(byte)));
69 * Volume representation cookie.
71 struct fscache_volume {
73 atomic_t n_cookies; /* Number of data cookies in volume */
74 atomic_t n_accesses; /* Number of cache accesses in progress */
75 unsigned int debug_id;
76 unsigned int key_hash; /* Hash of key string */
77 char *key; /* Volume ID, eg. "afs@example.com@1234" */
78 struct list_head proc_link; /* Link in /proc/fs/fscache/volumes */
79 struct hlist_bl_node hash_link; /* Link in hash table */
80 struct work_struct work;
81 struct fscache_cache *cache; /* The cache in which this resides */
82 void *cache_priv; /* Cache private data */
85 #define FSCACHE_VOLUME_RELINQUISHED 0 /* Volume is being cleaned up */
86 #define FSCACHE_VOLUME_INVALIDATE 1 /* Volume was invalidated */
87 #define FSCACHE_VOLUME_COLLIDED_WITH 2 /* Volume was collided with */
88 #define FSCACHE_VOLUME_ACQUIRE_PENDING 3 /* Volume is waiting to complete acquisition */
89 #define FSCACHE_VOLUME_CREATING 4 /* Volume is being created on disk */
90 u8 coherency_len; /* Length of the coherency data */
91 u8 coherency[]; /* Coherency data */
95 * Data file representation cookie.
96 * - a file will only appear in one cache
97 * - a request to cache a file may or may not be honoured, subject to
98 * constraints such as disk space
99 * - indices are created on disk just-in-time
101 struct fscache_cookie {
103 atomic_t n_active; /* number of active users of cookie */
104 atomic_t n_accesses; /* Number of cache accesses in progress */
105 unsigned int debug_id;
106 unsigned int inval_counter; /* Number of invalidations made */
108 struct fscache_volume *volume; /* Parent volume of this file. */
109 void *cache_priv; /* Cache-side representation */
110 struct hlist_bl_node hash_link; /* Link in hash table */
111 struct list_head proc_link; /* Link in proc list */
112 struct list_head commit_link; /* Link in commit queue */
113 struct work_struct work; /* Commit/relinq/withdraw work */
114 loff_t object_size; /* Size of the netfs object */
115 unsigned long unused_at; /* Time at which unused (jiffies) */
117 #define FSCACHE_COOKIE_RELINQUISHED 0 /* T if cookie has been relinquished */
118 #define FSCACHE_COOKIE_RETIRED 1 /* T if this cookie has retired on relinq */
119 #define FSCACHE_COOKIE_IS_CACHING 2 /* T if this cookie is cached */
120 #define FSCACHE_COOKIE_NO_DATA_TO_READ 3 /* T if this cookie has nothing to read */
121 #define FSCACHE_COOKIE_NEEDS_UPDATE 4 /* T if attrs have been updated */
122 #define FSCACHE_COOKIE_HAS_BEEN_CACHED 5 /* T if cookie needs withdraw-on-relinq */
123 #define FSCACHE_COOKIE_DISABLED 6 /* T if cookie has been disabled */
124 #define FSCACHE_COOKIE_LOCAL_WRITE 7 /* T if cookie has been modified locally */
125 #define FSCACHE_COOKIE_NO_ACCESS_WAKE 8 /* T if no wake when n_accesses goes 0 */
126 #define FSCACHE_COOKIE_DO_RELINQUISH 9 /* T if this cookie needs relinquishment */
127 #define FSCACHE_COOKIE_DO_WITHDRAW 10 /* T if this cookie needs withdrawing */
128 #define FSCACHE_COOKIE_DO_LRU_DISCARD 11 /* T if this cookie needs LRU discard */
129 #define FSCACHE_COOKIE_DO_PREP_TO_WRITE 12 /* T if cookie needs write preparation */
130 #define FSCACHE_COOKIE_HAVE_DATA 13 /* T if this cookie has data stored */
131 #define FSCACHE_COOKIE_IS_HASHED 14 /* T if this cookie is hashed */
133 enum fscache_cookie_state state;
134 u8 advice; /* FSCACHE_ADV_* */
135 u8 key_len; /* Length of index key */
136 u8 aux_len; /* Length of auxiliary data */
137 u32 key_hash; /* Hash of volume, key, len */
139 void *key; /* Index key */
140 u8 inline_key[16]; /* - If the key is short enough */
143 void *aux; /* Auxiliary data */
144 u8 inline_aux[8]; /* - If the aux data is short enough */
149 * slow-path functions for when there is actually caching available, and the
150 * netfs does actually have a valid token
151 * - these are not to be called directly
152 * - these are undefined symbols when FS-Cache is not configured and the
153 * optimiser takes care of not using them
155 extern struct fscache_volume *__fscache_acquire_volume(const char *, const char *,
156 const void *, size_t);
157 extern void __fscache_relinquish_volume(struct fscache_volume *, const void *, bool);
159 extern struct fscache_cookie *__fscache_acquire_cookie(
160 struct fscache_volume *,
162 const void *, size_t,
163 const void *, size_t,
165 extern void __fscache_use_cookie(struct fscache_cookie *, bool);
166 extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *);
167 extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
168 extern void __fscache_resize_cookie(struct fscache_cookie *, loff_t);
169 extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);
170 extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
171 extern int __fscache_begin_write_operation(struct netfs_cache_resources *, struct fscache_cookie *);
173 extern void __fscache_write_to_cache(struct fscache_cookie *, struct address_space *,
174 loff_t, size_t, loff_t, netfs_io_terminated_t, void *,
176 extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t);
179 * fscache_acquire_volume - Register a volume as desiring caching services
180 * @volume_key: An identification string for the volume
181 * @cache_name: The name of the cache to use (or NULL for the default)
182 * @coherency_data: Piece of arbitrary coherency data to check (or NULL)
183 * @coherency_len: The size of the coherency data
185 * Register a volume as desiring caching services if they're available. The
186 * caller must provide an identifier for the volume and may also indicate which
187 * cache it should be in. If a preexisting volume entry is found in the cache,
188 * the coherency data must match otherwise the entry will be invalidated.
190 * Returns a cookie pointer on success, -ENOMEM if out of memory or -EBUSY if a
191 * cache volume of that name is already acquired. Note that "NULL" is a valid
192 * cookie pointer and can be returned if caching is refused.
195 struct fscache_volume *fscache_acquire_volume(const char *volume_key,
196 const char *cache_name,
197 const void *coherency_data,
198 size_t coherency_len)
200 if (!fscache_available())
202 return __fscache_acquire_volume(volume_key, cache_name,
203 coherency_data, coherency_len);
207 * fscache_relinquish_volume - Cease caching a volume
208 * @volume: The volume cookie
209 * @coherency_data: Piece of arbitrary coherency data to set (or NULL)
210 * @invalidate: True if the volume should be invalidated
212 * Indicate that a filesystem no longer desires caching services for a volume.
213 * The caller must have relinquished all file cookies prior to calling this.
214 * The stored coherency data is updated.
217 void fscache_relinquish_volume(struct fscache_volume *volume,
218 const void *coherency_data,
221 if (fscache_volume_valid(volume))
222 __fscache_relinquish_volume(volume, coherency_data, invalidate);
226 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
227 * @volume: The volume in which to locate/create this cookie
228 * @advice: Advice flags (FSCACHE_COOKIE_ADV_*)
229 * @index_key: The index key for this cookie
230 * @index_key_len: Size of the index key
231 * @aux_data: The auxiliary data for the cookie (may be NULL)
232 * @aux_data_len: Size of the auxiliary data buffer
233 * @object_size: The initial size of object
235 * Acquire a cookie to represent a data file within the given cache volume.
237 * See Documentation/filesystems/caching/netfs-api.rst for a complete
241 struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume,
243 const void *index_key,
244 size_t index_key_len,
245 const void *aux_data,
249 if (!fscache_volume_valid(volume))
251 return __fscache_acquire_cookie(volume, advice,
252 index_key, index_key_len,
253 aux_data, aux_data_len,
258 * fscache_use_cookie - Request usage of cookie attached to an object
259 * @object: Object description
260 * @will_modify: If cache is expected to be modified locally
262 * Request usage of the cookie attached to an object. The caller should tell
263 * the cache if the object's contents are about to be modified locally and then
264 * the cache can apply the policy that has been set to handle this case.
266 static inline void fscache_use_cookie(struct fscache_cookie *cookie,
269 if (fscache_cookie_valid(cookie))
270 __fscache_use_cookie(cookie, will_modify);
274 * fscache_unuse_cookie - Cease usage of cookie attached to an object
275 * @object: Object description
276 * @aux_data: Updated auxiliary data (or NULL)
277 * @object_size: Revised size of the object (or NULL)
279 * Cease usage of the cookie attached to an object. When the users count
280 * reaches zero then the cookie relinquishment will be permitted to proceed.
282 static inline void fscache_unuse_cookie(struct fscache_cookie *cookie,
283 const void *aux_data,
284 const loff_t *object_size)
286 if (fscache_cookie_valid(cookie))
287 __fscache_unuse_cookie(cookie, aux_data, object_size);
291 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
293 * @cookie: The cookie being returned
294 * @retire: True if the cache object the cookie represents is to be discarded
296 * This function returns a cookie to the cache, forcibly discarding the
297 * associated cache object if retire is set to true.
299 * See Documentation/filesystems/caching/netfs-api.rst for a complete
303 void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
305 if (fscache_cookie_valid(cookie))
306 __fscache_relinquish_cookie(cookie, retire);
310 * Find the auxiliary data on a cookie.
312 static inline void *fscache_get_aux(struct fscache_cookie *cookie)
314 if (cookie->aux_len <= sizeof(cookie->inline_aux))
315 return cookie->inline_aux;
321 * Update the auxiliary data on a cookie.
324 void fscache_update_aux(struct fscache_cookie *cookie,
325 const void *aux_data, const loff_t *object_size)
327 void *p = fscache_get_aux(cookie);
330 memcpy(p, aux_data, cookie->aux_len);
332 cookie->object_size = *object_size;
335 #ifdef CONFIG_FSCACHE_STATS
336 extern atomic_t fscache_n_updates;
340 void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
341 const loff_t *object_size)
343 #ifdef CONFIG_FSCACHE_STATS
344 atomic_inc(&fscache_n_updates);
346 fscache_update_aux(cookie, aux_data, object_size);
348 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
352 * fscache_update_cookie - Request that a cache object be updated
353 * @cookie: The cookie representing the cache object
354 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
355 * @object_size: The current size of the object (may be NULL)
357 * Request an update of the index data for the cache object associated with the
358 * cookie. The auxiliary data on the cookie will be updated first if @aux_data
359 * is set and the object size will be updated and the object possibly trimmed
360 * if @object_size is set.
362 * See Documentation/filesystems/caching/netfs-api.rst for a complete
366 void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
367 const loff_t *object_size)
369 if (fscache_cookie_enabled(cookie))
370 __fscache_update_cookie(cookie, aux_data, object_size);
374 * fscache_resize_cookie - Request that a cache object be resized
375 * @cookie: The cookie representing the cache object
376 * @new_size: The new size of the object (may be NULL)
378 * Request that the size of an object be changed.
380 * See Documentation/filesystems/caching/netfs-api.txt for a complete
384 void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
386 if (fscache_cookie_enabled(cookie))
387 __fscache_resize_cookie(cookie, new_size);
391 * fscache_invalidate - Notify cache that an object needs invalidation
392 * @cookie: The cookie representing the cache object
393 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
394 * @size: The revised size of the object.
395 * @flags: Invalidation flags (FSCACHE_INVAL_*)
397 * Notify the cache that an object is needs to be invalidated and that it
398 * should abort any retrievals or stores it is doing on the cache. This
399 * increments inval_counter on the cookie which can be used by the caller to
400 * reconsider I/O requests as they complete.
402 * If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due
403 * to a direct I/O write and will cause caching to be disabled on this cookie
404 * until it is completely unused.
406 * See Documentation/filesystems/caching/netfs-api.rst for a complete
410 void fscache_invalidate(struct fscache_cookie *cookie,
411 const void *aux_data, loff_t size, unsigned int flags)
413 if (fscache_cookie_enabled(cookie))
414 __fscache_invalidate(cookie, aux_data, size, flags);
418 * fscache_operation_valid - Return true if operations resources are usable
419 * @cres: The resources to check.
421 * Returns a pointer to the operations table if usable or NULL if not.
424 const struct netfs_cache_ops *fscache_operation_valid(const struct netfs_cache_resources *cres)
426 return fscache_resources_valid(cres) ? cres->ops : NULL;
430 * fscache_begin_read_operation - Begin a read operation for the netfs lib
431 * @cres: The cache resources for the read being performed
432 * @cookie: The cookie representing the cache object
434 * Begin a read operation on behalf of the netfs helper library. @cres
435 * indicates the cache resources to which the operation state should be
436 * attached; @cookie indicates the cache object that will be accessed.
438 * This is intended to be called from the ->begin_cache_operation() netfs lib
439 * operation as implemented by the network filesystem.
441 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
442 * the end of the operation. This allows invalidation during the operation to
443 * be detected by the caller.
447 * * -ENOBUFS - No caching available
448 * * Other error code from the cache, such as -ENOMEM.
451 int fscache_begin_read_operation(struct netfs_cache_resources *cres,
452 struct fscache_cookie *cookie)
454 if (fscache_cookie_enabled(cookie))
455 return __fscache_begin_read_operation(cres, cookie);
460 * fscache_read - Start a read from the cache.
461 * @cres: The cache resources to use
462 * @start_pos: The beginning file offset in the cache file
463 * @iter: The buffer to fill - and also the length
464 * @read_hole: How to handle a hole in the data.
465 * @term_func: The function to call upon completion
466 * @term_func_priv: The private data for @term_func
468 * Start a read from the cache. @cres indicates the cache object to read from
469 * and must be obtained by a call to fscache_begin_operation() beforehand.
471 * The data is read into the iterator, @iter, and that also indicates the size
472 * of the operation. @start_pos is the start position in the file, though if
473 * @seek_data is set appropriately, the cache can use SEEK_DATA to find the
474 * next piece of data, writing zeros for the hole into the iterator.
476 * Upon termination of the operation, @term_func will be called and supplied
477 * with @term_func_priv plus the amount of data written, if successful, or the
478 * error code otherwise.
480 * @read_hole indicates how a partially populated region in the cache should be
481 * handled. It can be one of a number of settings:
483 * NETFS_READ_HOLE_IGNORE - Just try to read (may return a short read).
485 * NETFS_READ_HOLE_CLEAR - Seek for data, clearing the part of the buffer
486 * skipped over, then do as for IGNORE.
488 * NETFS_READ_HOLE_FAIL - Give ENODATA if we encounter a hole.
491 int fscache_read(struct netfs_cache_resources *cres,
493 struct iov_iter *iter,
494 enum netfs_read_from_hole read_hole,
495 netfs_io_terminated_t term_func,
496 void *term_func_priv)
498 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
499 return ops->read(cres, start_pos, iter, read_hole,
500 term_func, term_func_priv);
504 * fscache_begin_write_operation - Begin a write operation for the netfs lib
505 * @cres: The cache resources for the write being performed
506 * @cookie: The cookie representing the cache object
508 * Begin a write operation on behalf of the netfs helper library. @cres
509 * indicates the cache resources to which the operation state should be
510 * attached; @cookie indicates the cache object that will be accessed.
512 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
513 * the end of the operation. This allows invalidation during the operation to
514 * be detected by the caller.
518 * * -ENOBUFS - No caching available
519 * * Other error code from the cache, such as -ENOMEM.
522 int fscache_begin_write_operation(struct netfs_cache_resources *cres,
523 struct fscache_cookie *cookie)
525 if (fscache_cookie_enabled(cookie))
526 return __fscache_begin_write_operation(cres, cookie);
531 * fscache_write - Start a write to the cache.
532 * @cres: The cache resources to use
533 * @start_pos: The beginning file offset in the cache file
534 * @iter: The data to write - and also the length
535 * @term_func: The function to call upon completion
536 * @term_func_priv: The private data for @term_func
538 * Start a write to the cache. @cres indicates the cache object to write to and
539 * must be obtained by a call to fscache_begin_operation() beforehand.
541 * The data to be written is obtained from the iterator, @iter, and that also
542 * indicates the size of the operation. @start_pos is the start position in
545 * Upon termination of the operation, @term_func will be called and supplied
546 * with @term_func_priv plus the amount of data written, if successful, or the
547 * error code otherwise.
550 int fscache_write(struct netfs_cache_resources *cres,
552 struct iov_iter *iter,
553 netfs_io_terminated_t term_func,
554 void *term_func_priv)
556 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
557 return ops->write(cres, start_pos, iter, term_func, term_func_priv);
561 * fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages
562 * @cookie: The cookie representing the cache object
563 * @mapping: The netfs inode to use as the source
564 * @start: The start position in @mapping
565 * @len: The amount of data to unlock
566 * @caching: If PG_fscache has been set
568 * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's
571 static inline void fscache_clear_page_bits(struct fscache_cookie *cookie,
572 struct address_space *mapping,
573 loff_t start, size_t len,
577 __fscache_clear_page_bits(mapping, start, len);
581 * fscache_write_to_cache - Save a write to the cache and clear PG_fscache
582 * @cookie: The cookie representing the cache object
583 * @mapping: The netfs inode to use as the source
584 * @start: The start position in @mapping
585 * @len: The amount of data to write back
586 * @i_size: The new size of the inode
587 * @term_func: The function to call upon completion
588 * @term_func_priv: The private data for @term_func
589 * @caching: If PG_fscache has been set
591 * Helper function for a netfs to write dirty data from an inode into the cache
592 * object that's backing it.
594 * @start and @len describe the range of the data. This does not need to be
595 * page-aligned, but to satisfy DIO requirements, the cache may expand it up to
596 * the page boundaries on either end. All the pages covering the range must be
597 * marked with PG_fscache.
599 * If given, @term_func will be called upon completion and supplied with
600 * @term_func_priv. Note that the PG_fscache flags will have been cleared by
601 * this point, so the netfs must retain its own pin on the mapping.
603 static inline void fscache_write_to_cache(struct fscache_cookie *cookie,
604 struct address_space *mapping,
605 loff_t start, size_t len, loff_t i_size,
606 netfs_io_terminated_t term_func,
607 void *term_func_priv,
611 __fscache_write_to_cache(cookie, mapping, start, len, i_size,
612 term_func, term_func_priv, caching);
614 term_func(term_func_priv, -ENOBUFS, false);
618 #if __fscache_available
619 bool fscache_dirty_folio(struct address_space *mapping, struct folio *folio,
620 struct fscache_cookie *cookie);
622 #define fscache_dirty_folio(MAPPING, FOLIO, COOKIE) \
623 filemap_dirty_folio(MAPPING, FOLIO)
627 * fscache_unpin_writeback - Unpin writeback resources
628 * @wbc: The writeback control
629 * @cookie: The cookie referring to the cache object
631 * Unpin the writeback resources pinned by fscache_dirty_folio(). This is
632 * intended to be called by the netfs's ->write_inode() method.
634 static inline void fscache_unpin_writeback(struct writeback_control *wbc,
635 struct fscache_cookie *cookie)
637 if (wbc->unpinned_fscache_wb)
638 fscache_unuse_cookie(cookie, NULL, NULL);
642 * fscache_clear_inode_writeback - Clear writeback resources pinned by an inode
643 * @cookie: The cookie referring to the cache object
644 * @inode: The inode to clean up
645 * @aux: Auxiliary data to apply to the inode
647 * Clear any writeback resources held by an inode when the inode is evicted.
648 * This must be called before clear_inode() is called.
650 static inline void fscache_clear_inode_writeback(struct fscache_cookie *cookie,
654 if (inode->i_state & I_PINNING_FSCACHE_WB) {
655 loff_t i_size = i_size_read(inode);
656 fscache_unuse_cookie(cookie, aux, &i_size);
661 * fscache_note_page_release - Note that a netfs page got released
662 * @cookie: The cookie corresponding to the file
664 * Note that a page that has been copied to the cache has been released. This
665 * means that future reads will need to look in the cache to see if it's there.
668 void fscache_note_page_release(struct fscache_cookie *cookie)
670 /* If we've written data to the cache (HAVE_DATA) and there wasn't any
671 * data in the cache when we started (NO_DATA_TO_READ), it may no
672 * longer be true that we can skip reading from the cache - so clear
673 * the flag that causes reads to be skipped.
676 test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) &&
677 test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags))
678 clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
681 #endif /* _LINUX_FSCACHE_H */