1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/* General filesystem caching interface
3 *
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * NOTE!!! See:
8 *
9 * Documentation/filesystems/caching/netfs-api.rst
10 *
11 * for a description of the network filesystem interface declared here.
12 */
13
14#ifndef _LINUX_FSCACHE_H
15#define _LINUX_FSCACHE_H
16
17#include <linux/fs.h>
18#include <linux/netfs.h>
19#include <linux/writeback.h>
20
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))
28#else
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)
35#endif
36
37struct fscache_cookie;
38
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 */
43
44#define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */
45
46enum fscache_want_state {
47 FSCACHE_WANT_PARAMS,
48 FSCACHE_WANT_WRITE,
49 FSCACHE_WANT_READ,
50};
51
52/*
53 * Data object state.
54 */
55enum 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63 FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */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)));
68
69/*
70 * Volume representation cookie.
71 */
72struct fscache_volume {
73 refcount_t ref;
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 u8 *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 */
84 spinlock_t lock;
85 unsigned long flags;
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 */
93};
94
95/*
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
101 */
102struct fscache_cookie {
103 refcount_t ref;
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 */
108 spinlock_t lock;
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) */
117 unsigned long flags;
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 */
133#define FSCACHE_COOKIE_DO_INVALIDATE 15 /* T if cookie needs invalidation */
134
135 enum fscache_cookie_state state;
136 u8 advice; /* FSCACHE_ADV_* */
137 u8 key_len; /* Length of index key */
138 u8 aux_len; /* Length of auxiliary data */
139 u32 key_hash; /* Hash of volume, key, len */
140 union {
141 void *key; /* Index key */
142 u8 inline_key[16]; /* - If the key is short enough */
143 };
144 union {
145 void *aux; /* Auxiliary data */
146 u8 inline_aux[8]; /* - If the aux data is short enough */
147 };
148};
149
150/*
151 * slow-path functions for when there is actually caching available, and the
152 * netfs does actually have a valid token
153 * - these are not to be called directly
154 * - these are undefined symbols when FS-Cache is not configured and the
155 * optimiser takes care of not using them
156 */
157extern struct fscache_volume *__fscache_acquire_volume(const char *, const char *,
158 const void *, size_t);
159extern void __fscache_relinquish_volume(struct fscache_volume *, const void *, bool);
160
161extern struct fscache_cookie *__fscache_acquire_cookie(
162 struct fscache_volume *,
163 u8,
164 const void *, size_t,
165 const void *, size_t,
166 loff_t);
167extern void __fscache_use_cookie(struct fscache_cookie *, bool);
168extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *);
169extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
170extern void __fscache_resize_cookie(struct fscache_cookie *, loff_t);
171extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);
172extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
173extern int __fscache_begin_write_operation(struct netfs_cache_resources *, struct fscache_cookie *);
174
175void __fscache_write_to_cache(struct fscache_cookie *cookie,
176 struct address_space *mapping,
177 loff_t start, size_t len, loff_t i_size,
178 netfs_io_terminated_t term_func,
179 void *term_func_priv,
180 bool using_pgpriv2, bool cond);
181extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t);
182
183/**
184 * fscache_acquire_volume - Register a volume as desiring caching services
185 * @volume_key: An identification string for the volume
186 * @cache_name: The name of the cache to use (or NULL for the default)
187 * @coherency_data: Piece of arbitrary coherency data to check (or NULL)
188 * @coherency_len: The size of the coherency data
189 *
190 * Register a volume as desiring caching services if they're available. The
191 * caller must provide an identifier for the volume and may also indicate which
192 * cache it should be in. If a preexisting volume entry is found in the cache,
193 * the coherency data must match otherwise the entry will be invalidated.
194 *
195 * Returns a cookie pointer on success, -ENOMEM if out of memory or -EBUSY if a
196 * cache volume of that name is already acquired. Note that "NULL" is a valid
197 * cookie pointer and can be returned if caching is refused.
198 */
199static inline
200struct fscache_volume *fscache_acquire_volume(const char *volume_key,
201 const char *cache_name,
202 const void *coherency_data,
203 size_t coherency_len)
204{
205 if (!fscache_available())
206 return NULL;
207 return __fscache_acquire_volume(volume_key, cache_name,
208 coherency_data, coherency_len);
209}
210
211/**
212 * fscache_relinquish_volume - Cease caching a volume
213 * @volume: The volume cookie
214 * @coherency_data: Piece of arbitrary coherency data to set (or NULL)
215 * @invalidate: True if the volume should be invalidated
216 *
217 * Indicate that a filesystem no longer desires caching services for a volume.
218 * The caller must have relinquished all file cookies prior to calling this.
219 * The stored coherency data is updated.
220 */
221static inline
222void fscache_relinquish_volume(struct fscache_volume *volume,
223 const void *coherency_data,
224 bool invalidate)
225{
226 if (fscache_volume_valid(volume))
227 __fscache_relinquish_volume(volume, coherency_data, invalidate);
228}
229
230/**
231 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
232 * @volume: The volume in which to locate/create this cookie
233 * @advice: Advice flags (FSCACHE_COOKIE_ADV_*)
234 * @index_key: The index key for this cookie
235 * @index_key_len: Size of the index key
236 * @aux_data: The auxiliary data for the cookie (may be NULL)
237 * @aux_data_len: Size of the auxiliary data buffer
238 * @object_size: The initial size of object
239 *
240 * Acquire a cookie to represent a data file within the given cache volume.
241 *
242 * See Documentation/filesystems/caching/netfs-api.rst for a complete
243 * description.
244 */
245static inline
246struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume,
247 u8 advice,
248 const void *index_key,
249 size_t index_key_len,
250 const void *aux_data,
251 size_t aux_data_len,
252 loff_t object_size)
253{
254 if (!fscache_volume_valid(volume))
255 return NULL;
256 return __fscache_acquire_cookie(volume, advice,
257 index_key, index_key_len,
258 aux_data, aux_data_len,
259 object_size);
260}
261
262/**
263 * fscache_use_cookie - Request usage of cookie attached to an object
264 * @cookie: The cookie representing the cache object
265 * @will_modify: If cache is expected to be modified locally
266 *
267 * Request usage of the cookie attached to an object. The caller should tell
268 * the cache if the object's contents are about to be modified locally and then
269 * the cache can apply the policy that has been set to handle this case.
270 */
271static inline void fscache_use_cookie(struct fscache_cookie *cookie,
272 bool will_modify)
273{
274 if (fscache_cookie_valid(cookie))
275 __fscache_use_cookie(cookie, will_modify);
276}
277
278/**
279 * fscache_unuse_cookie - Cease usage of cookie attached to an object
280 * @cookie: The cookie representing the cache object
281 * @aux_data: Updated auxiliary data (or NULL)
282 * @object_size: Revised size of the object (or NULL)
283 *
284 * Cease usage of the cookie attached to an object. When the users count
285 * reaches zero then the cookie relinquishment will be permitted to proceed.
286 */
287static inline void fscache_unuse_cookie(struct fscache_cookie *cookie,
288 const void *aux_data,
289 const loff_t *object_size)
290{
291 if (fscache_cookie_valid(cookie))
292 __fscache_unuse_cookie(cookie, aux_data, object_size);
293}
294
295/**
296 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
297 * it
298 * @cookie: The cookie being returned
299 * @retire: True if the cache object the cookie represents is to be discarded
300 *
301 * This function returns a cookie to the cache, forcibly discarding the
302 * associated cache object if retire is set to true.
303 *
304 * See Documentation/filesystems/caching/netfs-api.rst for a complete
305 * description.
306 */
307static inline
308void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
309{
310 if (fscache_cookie_valid(cookie))
311 __fscache_relinquish_cookie(cookie, retire);
312}
313
314/*
315 * Find the auxiliary data on a cookie.
316 */
317static inline void *fscache_get_aux(struct fscache_cookie *cookie)
318{
319 if (cookie->aux_len <= sizeof(cookie->inline_aux))
320 return cookie->inline_aux;
321 else
322 return cookie->aux;
323}
324
325/*
326 * Update the auxiliary data on a cookie.
327 */
328static inline
329void fscache_update_aux(struct fscache_cookie *cookie,
330 const void *aux_data, const loff_t *object_size)
331{
332 void *p = fscache_get_aux(cookie);
333
334 if (aux_data && p)
335 memcpy(p, aux_data, cookie->aux_len);
336 if (object_size)
337 cookie->object_size = *object_size;
338}
339
340#ifdef CONFIG_FSCACHE_STATS
341extern atomic_t fscache_n_updates;
342#endif
343
344static inline
345void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
346 const loff_t *object_size)
347{
348#ifdef CONFIG_FSCACHE_STATS
349 atomic_inc(v: &fscache_n_updates);
350#endif
351 fscache_update_aux(cookie, aux_data, object_size);
352 smp_wmb();
353 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, addr: &cookie->flags);
354}
355
356/**
357 * fscache_update_cookie - Request that a cache object be updated
358 * @cookie: The cookie representing the cache object
359 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
360 * @object_size: The current size of the object (may be NULL)
361 *
362 * Request an update of the index data for the cache object associated with the
363 * cookie. The auxiliary data on the cookie will be updated first if @aux_data
364 * is set and the object size will be updated and the object possibly trimmed
365 * if @object_size is set.
366 *
367 * See Documentation/filesystems/caching/netfs-api.rst for a complete
368 * description.
369 */
370static inline
371void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
372 const loff_t *object_size)
373{
374 if (fscache_cookie_enabled(cookie))
375 __fscache_update_cookie(cookie, aux_data, object_size);
376}
377
378/**
379 * fscache_resize_cookie - Request that a cache object be resized
380 * @cookie: The cookie representing the cache object
381 * @new_size: The new size of the object (may be NULL)
382 *
383 * Request that the size of an object be changed.
384 *
385 * See Documentation/filesystems/caching/netfs-api.rst for a complete
386 * description.
387 */
388static inline
389void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
390{
391 if (fscache_cookie_enabled(cookie))
392 __fscache_resize_cookie(cookie, new_size);
393}
394
395/**
396 * fscache_invalidate - Notify cache that an object needs invalidation
397 * @cookie: The cookie representing the cache object
398 * @aux_data: The updated auxiliary data for the cookie (may be NULL)
399 * @size: The revised size of the object.
400 * @flags: Invalidation flags (FSCACHE_INVAL_*)
401 *
402 * Notify the cache that an object is needs to be invalidated and that it
403 * should abort any retrievals or stores it is doing on the cache. This
404 * increments inval_counter on the cookie which can be used by the caller to
405 * reconsider I/O requests as they complete.
406 *
407 * If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due
408 * to a direct I/O write and will cause caching to be disabled on this cookie
409 * until it is completely unused.
410 *
411 * See Documentation/filesystems/caching/netfs-api.rst for a complete
412 * description.
413 */
414static inline
415void fscache_invalidate(struct fscache_cookie *cookie,
416 const void *aux_data, loff_t size, unsigned int flags)
417{
418 if (fscache_cookie_enabled(cookie))
419 __fscache_invalidate(cookie, aux_data, size, flags);
420}
421
422/**
423 * fscache_operation_valid - Return true if operations resources are usable
424 * @cres: The resources to check.
425 *
426 * Returns a pointer to the operations table if usable or NULL if not.
427 */
428static inline
429const struct netfs_cache_ops *fscache_operation_valid(const struct netfs_cache_resources *cres)
430{
431 return fscache_resources_valid(cres) ? cres->ops : NULL;
432}
433
434/**
435 * fscache_begin_read_operation - Begin a read operation for the netfs lib
436 * @cres: The cache resources for the read being performed
437 * @cookie: The cookie representing the cache object
438 *
439 * Begin a read operation on behalf of the netfs helper library. @cres
440 * indicates the cache resources to which the operation state should be
441 * attached; @cookie indicates the cache object that will be accessed.
442 *
443 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
444 * the end of the operation. This allows invalidation during the operation to
445 * be detected by the caller.
446 *
447 * Returns:
448 * * 0 - Success
449 * * -ENOBUFS - No caching available
450 * * Other error code from the cache, such as -ENOMEM.
451 */
452static inline
453int fscache_begin_read_operation(struct netfs_cache_resources *cres,
454 struct fscache_cookie *cookie)
455{
456 if (fscache_cookie_enabled(cookie))
457 return __fscache_begin_read_operation(cres, cookie);
458 return -ENOBUFS;
459}
460
461/**
462 * fscache_end_operation - End the read operation for the netfs lib
463 * @cres: The cache resources for the read operation
464 *
465 * Clean up the resources at the end of the read request.
466 */
467static inline void fscache_end_operation(struct netfs_cache_resources *cres)
468{
469 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
470
471 if (ops)
472 ops->end_operation(cres);
473}
474
475/**
476 * fscache_read - Start a read from the cache.
477 * @cres: The cache resources to use
478 * @start_pos: The beginning file offset in the cache file
479 * @iter: The buffer to fill - and also the length
480 * @read_hole: How to handle a hole in the data.
481 * @term_func: The function to call upon completion
482 * @term_func_priv: The private data for @term_func
483 *
484 * Start a read from the cache. @cres indicates the cache object to read from
485 * and must be obtained by a call to fscache_begin_operation() beforehand.
486 *
487 * The data is read into the iterator, @iter, and that also indicates the size
488 * of the operation. @start_pos is the start position in the file, though if
489 * @seek_data is set appropriately, the cache can use SEEK_DATA to find the
490 * next piece of data, writing zeros for the hole into the iterator.
491 *
492 * Upon termination of the operation, @term_func will be called and supplied
493 * with @term_func_priv plus the amount of data written, if successful, or the
494 * error code otherwise.
495 *
496 * @read_hole indicates how a partially populated region in the cache should be
497 * handled. It can be one of a number of settings:
498 *
499 * NETFS_READ_HOLE_IGNORE - Just try to read (may return a short read).
500 *
501 * NETFS_READ_HOLE_FAIL - Give ENODATA if we encounter a hole.
502 */
503static inline
504int fscache_read(struct netfs_cache_resources *cres,
505 loff_t start_pos,
506 struct iov_iter *iter,
507 enum netfs_read_from_hole read_hole,
508 netfs_io_terminated_t term_func,
509 void *term_func_priv)
510{
511 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
512 return ops->read(cres, start_pos, iter, read_hole,
513 term_func, term_func_priv);
514}
515
516/**
517 * fscache_begin_write_operation - Begin a write operation for the netfs lib
518 * @cres: The cache resources for the write being performed
519 * @cookie: The cookie representing the cache object
520 *
521 * Begin a write operation on behalf of the netfs helper library. @cres
522 * indicates the cache resources to which the operation state should be
523 * attached; @cookie indicates the cache object that will be accessed.
524 *
525 * @cres->inval_counter is set from @cookie->inval_counter for comparison at
526 * the end of the operation. This allows invalidation during the operation to
527 * be detected by the caller.
528 *
529 * Returns:
530 * * 0 - Success
531 * * -ENOBUFS - No caching available
532 * * Other error code from the cache, such as -ENOMEM.
533 */
534static inline
535int fscache_begin_write_operation(struct netfs_cache_resources *cres,
536 struct fscache_cookie *cookie)
537{
538 if (fscache_cookie_enabled(cookie))
539 return __fscache_begin_write_operation(cres, cookie);
540 return -ENOBUFS;
541}
542
543/**
544 * fscache_write - Start a write to the cache.
545 * @cres: The cache resources to use
546 * @start_pos: The beginning file offset in the cache file
547 * @iter: The data to write - and also the length
548 * @term_func: The function to call upon completion
549 * @term_func_priv: The private data for @term_func
550 *
551 * Start a write to the cache. @cres indicates the cache object to write to and
552 * must be obtained by a call to fscache_begin_operation() beforehand.
553 *
554 * The data to be written is obtained from the iterator, @iter, and that also
555 * indicates the size of the operation. @start_pos is the start position in
556 * the file.
557 *
558 * Upon termination of the operation, @term_func will be called and supplied
559 * with @term_func_priv plus the amount of data written, if successful, or the
560 * error code otherwise.
561 */
562static inline
563int fscache_write(struct netfs_cache_resources *cres,
564 loff_t start_pos,
565 struct iov_iter *iter,
566 netfs_io_terminated_t term_func,
567 void *term_func_priv)
568{
569 const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
570 return ops->write(cres, start_pos, iter, term_func, term_func_priv);
571}
572
573/**
574 * fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages
575 * @mapping: The netfs inode to use as the source
576 * @start: The start position in @mapping
577 * @len: The amount of data to unlock
578 * @caching: If PG_fscache has been set
579 *
580 * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's
581 * waiting.
582 */
583static inline void fscache_clear_page_bits(struct address_space *mapping,
584 loff_t start, size_t len,
585 bool caching)
586{
587 if (caching)
588 __fscache_clear_page_bits(mapping, start, len);
589}
590
591/**
592 * fscache_write_to_cache - Save a write to the cache and clear PG_fscache
593 * @cookie: The cookie representing the cache object
594 * @mapping: The netfs inode to use as the source
595 * @start: The start position in @mapping
596 * @len: The amount of data to write back
597 * @i_size: The new size of the inode
598 * @term_func: The function to call upon completion
599 * @term_func_priv: The private data for @term_func
600 * @using_pgpriv2: If we're using PG_private_2 to mark in-progress write
601 * @caching: If we actually want to do the caching
602 *
603 * Helper function for a netfs to write dirty data from an inode into the cache
604 * object that's backing it.
605 *
606 * @start and @len describe the range of the data. This does not need to be
607 * page-aligned, but to satisfy DIO requirements, the cache may expand it up to
608 * the page boundaries on either end. All the pages covering the range must be
609 * marked with PG_fscache.
610 *
611 * If given, @term_func will be called upon completion and supplied with
612 * @term_func_priv. Note that if @using_pgpriv2 is set, the PG_private_2 flags
613 * will have been cleared by this point, so the netfs must retain its own pin
614 * on the mapping.
615 */
616static 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,
621 bool using_pgpriv2, bool caching)
622{
623 if (caching)
624 __fscache_write_to_cache(cookie, mapping, start, len, i_size,
625 term_func, term_func_priv,
626 using_pgpriv2, cond: caching);
627 else if (term_func)
628 term_func(term_func_priv, -ENOBUFS);
629
630}
631
632/**
633 * fscache_note_page_release - Note that a netfs page got released
634 * @cookie: The cookie corresponding to the file
635 *
636 * Note that a page that has been copied to the cache has been released. This
637 * means that future reads will need to look in the cache to see if it's there.
638 */
639static inline
640void fscache_note_page_release(struct fscache_cookie *cookie)
641{
642 /* If we've written data to the cache (HAVE_DATA) and there wasn't any
643 * data in the cache when we started (NO_DATA_TO_READ), it may no
644 * longer be true that we can skip reading from the cache - so clear
645 * the flag that causes reads to be skipped.
646 */
647 if (cookie &&
648 test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) &&
649 test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags))
650 clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, addr: &cookie->flags);
651}
652
653#endif /* _LINUX_FSCACHE_H */
654

source code of linux/include/linux/fscache.h