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1/* General filesystem caching interface
2 *
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * NOTE!!! See:
12 *
13 * Documentation/filesystems/caching/netfs-api.txt
14 *
15 * for a description of the network filesystem interface declared here.
16 */
17
18#ifndef _LINUX_FSCACHE_H
19#define _LINUX_FSCACHE_H
20
21#include <linux/fs.h>
22#include <linux/list.h>
23#include <linux/pagemap.h>
24#include <linux/pagevec.h>
25
26#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
27#define fscache_available() (1)
28#define fscache_cookie_valid(cookie) (cookie)
29#else
30#define fscache_available() (0)
31#define fscache_cookie_valid(cookie) (0)
32#endif
33
34
35/*
36 * overload PG_private_2 to give us PG_fscache - this is used to indicate that
37 * a page is currently backed by a local disk cache
38 */
39#define PageFsCache(page) PagePrivate2((page))
40#define SetPageFsCache(page) SetPagePrivate2((page))
41#define ClearPageFsCache(page) ClearPagePrivate2((page))
42#define TestSetPageFsCache(page) TestSetPagePrivate2((page))
43#define TestClearPageFsCache(page) TestClearPagePrivate2((page))
44
45/* pattern used to fill dead space in an index entry */
46#define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
47
48struct pagevec;
49struct fscache_cache_tag;
50struct fscache_cookie;
51struct fscache_netfs;
52
53typedef void (*fscache_rw_complete_t)(struct page *page,
54 void *context,
55 int error);
56
57/* result of index entry consultation */
58enum fscache_checkaux {
59 FSCACHE_CHECKAUX_OKAY, /* entry okay as is */
60 FSCACHE_CHECKAUX_NEEDS_UPDATE, /* entry requires update */
61 FSCACHE_CHECKAUX_OBSOLETE, /* entry requires deletion */
62};
63
64/*
65 * fscache cookie definition
66 */
67struct fscache_cookie_def {
68 /* name of cookie type */
69 char name[16];
70
71 /* cookie type */
72 uint8_t type;
73#define FSCACHE_COOKIE_TYPE_INDEX 0
74#define FSCACHE_COOKIE_TYPE_DATAFILE 1
75
76 /* select the cache into which to insert an entry in this index
77 * - optional
78 * - should return a cache identifier or NULL to cause the cache to be
79 * inherited from the parent if possible or the first cache picked
80 * for a non-index file if not
81 */
82 struct fscache_cache_tag *(*select_cache)(
83 const void *parent_netfs_data,
84 const void *cookie_netfs_data);
85
86 /* get an index key
87 * - should store the key data in the buffer
88 * - should return the amount of amount stored
89 * - not permitted to return an error
90 * - the netfs data from the cookie being used as the source is
91 * presented
92 */
93 uint16_t (*get_key)(const void *cookie_netfs_data,
94 void *buffer,
95 uint16_t bufmax);
96
97 /* get certain file attributes from the netfs data
98 * - this function can be absent for an index
99 * - not permitted to return an error
100 * - the netfs data from the cookie being used as the source is
101 * presented
102 */
103 void (*get_attr)(const void *cookie_netfs_data, uint64_t *size);
104
105 /* get the auxilliary data from netfs data
106 * - this function can be absent if the index carries no state data
107 * - should store the auxilliary data in the buffer
108 * - should return the amount of amount stored
109 * - not permitted to return an error
110 * - the netfs data from the cookie being used as the source is
111 * presented
112 */
113 uint16_t (*get_aux)(const void *cookie_netfs_data,
114 void *buffer,
115 uint16_t bufmax);
116
117 /* consult the netfs about the state of an object
118 * - this function can be absent if the index carries no state data
119 * - the netfs data from the cookie being used as the target is
120 * presented, as is the auxilliary data
121 */
122 enum fscache_checkaux (*check_aux)(void *cookie_netfs_data,
123 const void *data,
124 uint16_t datalen);
125
126 /* get an extra reference on a read context
127 * - this function can be absent if the completion function doesn't
128 * require a context
129 */
130 void (*get_context)(void *cookie_netfs_data, void *context);
131
132 /* release an extra reference on a read context
133 * - this function can be absent if the completion function doesn't
134 * require a context
135 */
136 void (*put_context)(void *cookie_netfs_data, void *context);
137
138 /* indicate pages that now have cache metadata retained
139 * - this function should mark the specified pages as now being cached
140 * - the pages will have been marked with PG_fscache before this is
141 * called, so this is optional
142 */
143 void (*mark_pages_cached)(void *cookie_netfs_data,
144 struct address_space *mapping,
145 struct pagevec *cached_pvec);
146
147 /* indicate the cookie is no longer cached
148 * - this function is called when the backing store currently caching
149 * a cookie is removed
150 * - the netfs should use this to clean up any markers indicating
151 * cached pages
152 * - this is mandatory for any object that may have data
153 */
154 void (*now_uncached)(void *cookie_netfs_data);
155};
156
157/*
158 * fscache cached network filesystem type
159 * - name, version and ops must be filled in before registration
160 * - all other fields will be set during registration
161 */
162struct fscache_netfs {
163 uint32_t version; /* indexing version */
164 const char *name; /* filesystem name */
165 struct fscache_cookie *primary_index;
166 struct list_head link; /* internal link */
167};
168
169/*
170 * slow-path functions for when there is actually caching available, and the
171 * netfs does actually have a valid token
172 * - these are not to be called directly
173 * - these are undefined symbols when FS-Cache is not configured and the
174 * optimiser takes care of not using them
175 */
176extern int __fscache_register_netfs(struct fscache_netfs *);
177extern void __fscache_unregister_netfs(struct fscache_netfs *);
178extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
179extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
180
181extern struct fscache_cookie *__fscache_acquire_cookie(
182 struct fscache_cookie *,
183 const struct fscache_cookie_def *,
184 void *);
185extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
186extern void __fscache_update_cookie(struct fscache_cookie *);
187extern int __fscache_attr_changed(struct fscache_cookie *);
188extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
189 struct page *,
190 fscache_rw_complete_t,
191 void *,
192 gfp_t);
193extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
194 struct address_space *,
195 struct list_head *,
196 unsigned *,
197 fscache_rw_complete_t,
198 void *,
199 gfp_t);
200extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
201extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
202extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
203extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
204extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
205
206/**
207 * fscache_register_netfs - Register a filesystem as desiring caching services
208 * @netfs: The description of the filesystem
209 *
210 * Register a filesystem as desiring caching services if they're available.
211 *
212 * See Documentation/filesystems/caching/netfs-api.txt for a complete
213 * description.
214 */
215static inline
216int fscache_register_netfs(struct fscache_netfs *netfs)
217{
218 if (fscache_available())
219 return __fscache_register_netfs(netfs);
220 else
221 return 0;
222}
223
224/**
225 * fscache_unregister_netfs - Indicate that a filesystem no longer desires
226 * caching services
227 * @netfs: The description of the filesystem
228 *
229 * Indicate that a filesystem no longer desires caching services for the
230 * moment.
231 *
232 * See Documentation/filesystems/caching/netfs-api.txt for a complete
233 * description.
234 */
235static inline
236void fscache_unregister_netfs(struct fscache_netfs *netfs)
237{
238 if (fscache_available())
239 __fscache_unregister_netfs(netfs);
240}
241
242/**
243 * fscache_lookup_cache_tag - Look up a cache tag
244 * @name: The name of the tag to search for
245 *
246 * Acquire a specific cache referral tag that can be used to select a specific
247 * cache in which to cache an index.
248 *
249 * See Documentation/filesystems/caching/netfs-api.txt for a complete
250 * description.
251 */
252static inline
253struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
254{
255 if (fscache_available())
256 return __fscache_lookup_cache_tag(name);
257 else
258 return NULL;
259}
260
261/**
262 * fscache_release_cache_tag - Release a cache tag
263 * @tag: The tag to release
264 *
265 * Release a reference to a cache referral tag previously looked up.
266 *
267 * See Documentation/filesystems/caching/netfs-api.txt for a complete
268 * description.
269 */
270static inline
271void fscache_release_cache_tag(struct fscache_cache_tag *tag)
272{
273 if (fscache_available())
274 __fscache_release_cache_tag(tag);
275}
276
277/**
278 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
279 * @parent: The cookie that's to be the parent of this one
280 * @def: A description of the cache object, including callback operations
281 * @netfs_data: An arbitrary piece of data to be kept in the cookie to
282 * represent the cache object to the netfs
283 *
284 * This function is used to inform FS-Cache about part of an index hierarchy
285 * that can be used to locate files. This is done by requesting a cookie for
286 * each index in the path to the file.
287 *
288 * See Documentation/filesystems/caching/netfs-api.txt for a complete
289 * description.
290 */
291static inline
292struct fscache_cookie *fscache_acquire_cookie(
293 struct fscache_cookie *parent,
294 const struct fscache_cookie_def *def,
295 void *netfs_data)
296{
297 if (fscache_cookie_valid(parent))
298 return __fscache_acquire_cookie(parent, def, netfs_data);
299 else
300 return NULL;
301}
302
303/**
304 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
305 * it
306 * @cookie: The cookie being returned
307 * @retire: True if the cache object the cookie represents is to be discarded
308 *
309 * This function returns a cookie to the cache, forcibly discarding the
310 * associated cache object if retire is set to true.
311 *
312 * See Documentation/filesystems/caching/netfs-api.txt for a complete
313 * description.
314 */
315static inline
316void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
317{
318 if (fscache_cookie_valid(cookie))
319 __fscache_relinquish_cookie(cookie, retire);
320}
321
322/**
323 * fscache_update_cookie - Request that a cache object be updated
324 * @cookie: The cookie representing the cache object
325 *
326 * Request an update of the index data for the cache object associated with the
327 * cookie.
328 *
329 * See Documentation/filesystems/caching/netfs-api.txt for a complete
330 * description.
331 */
332static inline
333void fscache_update_cookie(struct fscache_cookie *cookie)
334{
335 if (fscache_cookie_valid(cookie))
336 __fscache_update_cookie(cookie);
337}
338
339/**
340 * fscache_pin_cookie - Pin a data-storage cache object in its cache
341 * @cookie: The cookie representing the cache object
342 *
343 * Permit data-storage cache objects to be pinned in the cache.
344 *
345 * See Documentation/filesystems/caching/netfs-api.txt for a complete
346 * description.
347 */
348static inline
349int fscache_pin_cookie(struct fscache_cookie *cookie)
350{
351 return -ENOBUFS;
352}
353
354/**
355 * fscache_pin_cookie - Unpin a data-storage cache object in its cache
356 * @cookie: The cookie representing the cache object
357 *
358 * Permit data-storage cache objects to be unpinned from the cache.
359 *
360 * See Documentation/filesystems/caching/netfs-api.txt for a complete
361 * description.
362 */
363static inline
364void fscache_unpin_cookie(struct fscache_cookie *cookie)
365{
366}
367
368/**
369 * fscache_attr_changed - Notify cache that an object's attributes changed
370 * @cookie: The cookie representing the cache object
371 *
372 * Send a notification to the cache indicating that an object's attributes have
373 * changed. This includes the data size. These attributes will be obtained
374 * through the get_attr() cookie definition op.
375 *
376 * See Documentation/filesystems/caching/netfs-api.txt for a complete
377 * description.
378 */
379static inline
380int fscache_attr_changed(struct fscache_cookie *cookie)
381{
382 if (fscache_cookie_valid(cookie))
383 return __fscache_attr_changed(cookie);
384 else
385 return -ENOBUFS;
386}
387
388/**
389 * fscache_reserve_space - Reserve data space for a cached object
390 * @cookie: The cookie representing the cache object
391 * @i_size: The amount of space to be reserved
392 *
393 * Reserve an amount of space in the cache for the cache object attached to a
394 * cookie so that a write to that object within the space can always be
395 * honoured.
396 *
397 * See Documentation/filesystems/caching/netfs-api.txt for a complete
398 * description.
399 */
400static inline
401int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
402{
403 return -ENOBUFS;
404}
405
406/**
407 * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
408 * in which to store it
409 * @cookie: The cookie representing the cache object
410 * @page: The netfs page to fill if possible
411 * @end_io_func: The callback to invoke when and if the page is filled
412 * @context: An arbitrary piece of data to pass on to end_io_func()
413 * @gfp: The conditions under which memory allocation should be made
414 *
415 * Read a page from the cache, or if that's not possible make a potential
416 * one-block reservation in the cache into which the page may be stored once
417 * fetched from the server.
418 *
419 * If the page is not backed by the cache object, or if it there's some reason
420 * it can't be, -ENOBUFS will be returned and nothing more will be done for
421 * that page.
422 *
423 * Else, if that page is backed by the cache, a read will be initiated directly
424 * to the netfs's page and 0 will be returned by this function. The
425 * end_io_func() callback will be invoked when the operation terminates on a
426 * completion or failure. Note that the callback may be invoked before the
427 * return.
428 *
429 * Else, if the page is unbacked, -ENODATA is returned and a block may have
430 * been allocated in the cache.
431 *
432 * See Documentation/filesystems/caching/netfs-api.txt for a complete
433 * description.
434 */
435static inline
436int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
437 struct page *page,
438 fscache_rw_complete_t end_io_func,
439 void *context,
440 gfp_t gfp)
441{
442 if (fscache_cookie_valid(cookie))
443 return __fscache_read_or_alloc_page(cookie, page, end_io_func,
444 context, gfp);
445 else
446 return -ENOBUFS;
447}
448
449/**
450 * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
451 * blocks in which to store them
452 * @cookie: The cookie representing the cache object
453 * @mapping: The netfs inode mapping to which the pages will be attached
454 * @pages: A list of potential netfs pages to be filled
455 * @end_io_func: The callback to invoke when and if each page is filled
456 * @context: An arbitrary piece of data to pass on to end_io_func()
457 * @gfp: The conditions under which memory allocation should be made
458 *
459 * Read a set of pages from the cache, or if that's not possible, attempt to
460 * make a potential one-block reservation for each page in the cache into which
461 * that page may be stored once fetched from the server.
462 *
463 * If some pages are not backed by the cache object, or if it there's some
464 * reason they can't be, -ENOBUFS will be returned and nothing more will be
465 * done for that pages.
466 *
467 * Else, if some of the pages are backed by the cache, a read will be initiated
468 * directly to the netfs's page and 0 will be returned by this function. The
469 * end_io_func() callback will be invoked when the operation terminates on a
470 * completion or failure. Note that the callback may be invoked before the
471 * return.
472 *
473 * Else, if a page is unbacked, -ENODATA is returned and a block may have
474 * been allocated in the cache.
475 *
476 * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
477 * regard to different pages, the return values are prioritised in that order.
478 * Any pages submitted for reading are removed from the pages list.
479 *
480 * See Documentation/filesystems/caching/netfs-api.txt for a complete
481 * description.
482 */
483static inline
484int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
485 struct address_space *mapping,
486 struct list_head *pages,
487 unsigned *nr_pages,
488 fscache_rw_complete_t end_io_func,
489 void *context,
490 gfp_t gfp)
491{
492 if (fscache_cookie_valid(cookie))
493 return __fscache_read_or_alloc_pages(cookie, mapping, pages,
494 nr_pages, end_io_func,
495 context, gfp);
496 else
497 return -ENOBUFS;
498}
499
500/**
501 * fscache_alloc_page - Allocate a block in which to store a page
502 * @cookie: The cookie representing the cache object
503 * @page: The netfs page to allocate a page for
504 * @gfp: The conditions under which memory allocation should be made
505 *
506 * Request Allocation a block in the cache in which to store a netfs page
507 * without retrieving any contents from the cache.
508 *
509 * If the page is not backed by a file then -ENOBUFS will be returned and
510 * nothing more will be done, and no reservation will be made.
511 *
512 * Else, a block will be allocated if one wasn't already, and 0 will be
513 * returned
514 *
515 * See Documentation/filesystems/caching/netfs-api.txt for a complete
516 * description.
517 */
518static inline
519int fscache_alloc_page(struct fscache_cookie *cookie,
520 struct page *page,
521 gfp_t gfp)
522{
523 if (fscache_cookie_valid(cookie))
524 return __fscache_alloc_page(cookie, page, gfp);
525 else
526 return -ENOBUFS;
527}
528
529/**
530 * fscache_write_page - Request storage of a page in the cache
531 * @cookie: The cookie representing the cache object
532 * @page: The netfs page to store
533 * @gfp: The conditions under which memory allocation should be made
534 *
535 * Request the contents of the netfs page be written into the cache. This
536 * request may be ignored if no cache block is currently allocated, in which
537 * case it will return -ENOBUFS.
538 *
539 * If a cache block was already allocated, a write will be initiated and 0 will
540 * be returned. The PG_fscache_write page bit is set immediately and will then
541 * be cleared at the completion of the write to indicate the success or failure
542 * of the operation. Note that the completion may happen before the return.
543 *
544 * See Documentation/filesystems/caching/netfs-api.txt for a complete
545 * description.
546 */
547static inline
548int fscache_write_page(struct fscache_cookie *cookie,
549 struct page *page,
550 gfp_t gfp)
551{
552 if (fscache_cookie_valid(cookie))
553 return __fscache_write_page(cookie, page, gfp);
554 else
555 return -ENOBUFS;
556}
557
558/**
559 * fscache_uncache_page - Indicate that caching is no longer required on a page
560 * @cookie: The cookie representing the cache object
561 * @page: The netfs page that was being cached.
562 *
563 * Tell the cache that we no longer want a page to be cached and that it should
564 * remove any knowledge of the netfs page it may have.
565 *
566 * Note that this cannot cancel any outstanding I/O operations between this
567 * page and the cache.
568 *
569 * See Documentation/filesystems/caching/netfs-api.txt for a complete
570 * description.
571 */
572static inline
573void fscache_uncache_page(struct fscache_cookie *cookie,
574 struct page *page)
575{
576 if (fscache_cookie_valid(cookie))
577 __fscache_uncache_page(cookie, page);
578}
579
580/**
581 * fscache_check_page_write - Ask if a page is being writing to the cache
582 * @cookie: The cookie representing the cache object
583 * @page: The netfs page that is being cached.
584 *
585 * Ask the cache if a page is being written to the cache.
586 *
587 * See Documentation/filesystems/caching/netfs-api.txt for a complete
588 * description.
589 */
590static inline
591bool fscache_check_page_write(struct fscache_cookie *cookie,
592 struct page *page)
593{
594 if (fscache_cookie_valid(cookie))
595 return __fscache_check_page_write(cookie, page);
596 return false;
597}
598
599/**
600 * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
601 * @cookie: The cookie representing the cache object
602 * @page: The netfs page that is being cached.
603 *
604 * Ask the cache to wake us up when a page is no longer being written to the
605 * cache.
606 *
607 * See Documentation/filesystems/caching/netfs-api.txt for a complete
608 * description.
609 */
610static inline
611void fscache_wait_on_page_write(struct fscache_cookie *cookie,
612 struct page *page)
613{
614 if (fscache_cookie_valid(cookie))
615 __fscache_wait_on_page_write(cookie, page);
616}
617
618#endif /* _LINUX_FSCACHE_H */