1 /* General filesystem caching interface
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
13 * Documentation/filesystems/caching/netfs-api.txt
15 * for a description of the network filesystem interface declared here.
18 #ifndef _LINUX_FSCACHE_H
19 #define _LINUX_FSCACHE_H
22 #include <linux/list.h>
23 #include <linux/pagemap.h>
24 #include <linux/pagevec.h>
26 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
27 #define fscache_available() (1)
28 #define fscache_cookie_valid(cookie) (cookie)
30 #define fscache_available() (0)
31 #define fscache_cookie_valid(cookie) (0)
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
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))
45 /* pattern used to fill dead space in an index entry */
46 #define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
49 struct fscache_cache_tag
;
50 struct fscache_cookie
;
53 typedef void (*fscache_rw_complete_t
)(struct page
*page
,
57 /* result of index entry consultation */
58 enum 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 */
65 * fscache cookie definition
67 struct fscache_cookie_def
{
68 /* name of cookie type */
73 #define FSCACHE_COOKIE_TYPE_INDEX 0
74 #define FSCACHE_COOKIE_TYPE_DATAFILE 1
76 /* select the cache into which to insert an entry in this index
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
82 struct fscache_cache_tag
*(*select_cache
)(
83 const void *parent_netfs_data
,
84 const void *cookie_netfs_data
);
87 * - should store the key data in the buffer
88 * - should return the amount of data stored
89 * - not permitted to return an error
90 * - the netfs data from the cookie being used as the source is
93 uint16_t (*get_key
)(const void *cookie_netfs_data
,
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
103 void (*get_attr
)(const void *cookie_netfs_data
, uint64_t *size
);
105 /* get the auxiliary data from netfs data
106 * - this function can be absent if the index carries no state data
107 * - should store the auxiliary 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
113 uint16_t (*get_aux
)(const void *cookie_netfs_data
,
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 auxiliary data
122 enum fscache_checkaux (*check_aux
)(void *cookie_netfs_data
,
126 /* get an extra reference on a read context
127 * - this function can be absent if the completion function doesn't
130 void (*get_context
)(void *cookie_netfs_data
, void *context
);
132 /* release an extra reference on a read context
133 * - this function can be absent if the completion function doesn't
136 void (*put_context
)(void *cookie_netfs_data
, void *context
);
138 /* indicate page that now have cache metadata retained
139 * - this function should mark the specified page as now being cached
140 * - the page will have been marked with PG_fscache before this is
141 * called, so this is optional
143 void (*mark_page_cached
)(void *cookie_netfs_data
,
144 struct address_space
*mapping
,
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
152 * - this is mandatory for any object that may have data
154 void (*now_uncached
)(void *cookie_netfs_data
);
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
162 struct 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 */
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
176 extern int __fscache_register_netfs(struct fscache_netfs
*);
177 extern void __fscache_unregister_netfs(struct fscache_netfs
*);
178 extern struct fscache_cache_tag
*__fscache_lookup_cache_tag(const char *);
179 extern void __fscache_release_cache_tag(struct fscache_cache_tag
*);
181 extern struct fscache_cookie
*__fscache_acquire_cookie(
182 struct fscache_cookie
*,
183 const struct fscache_cookie_def
*,
185 extern void __fscache_relinquish_cookie(struct fscache_cookie
*, int);
186 extern int __fscache_check_consistency(struct fscache_cookie
*);
187 extern void __fscache_update_cookie(struct fscache_cookie
*);
188 extern int __fscache_attr_changed(struct fscache_cookie
*);
189 extern void __fscache_invalidate(struct fscache_cookie
*);
190 extern void __fscache_wait_on_invalidate(struct fscache_cookie
*);
191 extern int __fscache_read_or_alloc_page(struct fscache_cookie
*,
193 fscache_rw_complete_t
,
196 extern int __fscache_read_or_alloc_pages(struct fscache_cookie
*,
197 struct address_space
*,
200 fscache_rw_complete_t
,
203 extern int __fscache_alloc_page(struct fscache_cookie
*, struct page
*, gfp_t
);
204 extern int __fscache_write_page(struct fscache_cookie
*, struct page
*, gfp_t
);
205 extern void __fscache_uncache_page(struct fscache_cookie
*, struct page
*);
206 extern bool __fscache_check_page_write(struct fscache_cookie
*, struct page
*);
207 extern void __fscache_wait_on_page_write(struct fscache_cookie
*, struct page
*);
208 extern bool __fscache_maybe_release_page(struct fscache_cookie
*, struct page
*,
210 extern void __fscache_uncache_all_inode_pages(struct fscache_cookie
*,
214 * fscache_register_netfs - Register a filesystem as desiring caching services
215 * @netfs: The description of the filesystem
217 * Register a filesystem as desiring caching services if they're available.
219 * See Documentation/filesystems/caching/netfs-api.txt for a complete
223 int fscache_register_netfs(struct fscache_netfs
*netfs
)
225 if (fscache_available())
226 return __fscache_register_netfs(netfs
);
232 * fscache_unregister_netfs - Indicate that a filesystem no longer desires
234 * @netfs: The description of the filesystem
236 * Indicate that a filesystem no longer desires caching services for the
239 * See Documentation/filesystems/caching/netfs-api.txt for a complete
243 void fscache_unregister_netfs(struct fscache_netfs
*netfs
)
245 if (fscache_available())
246 __fscache_unregister_netfs(netfs
);
250 * fscache_lookup_cache_tag - Look up a cache tag
251 * @name: The name of the tag to search for
253 * Acquire a specific cache referral tag that can be used to select a specific
254 * cache in which to cache an index.
256 * See Documentation/filesystems/caching/netfs-api.txt for a complete
260 struct fscache_cache_tag
*fscache_lookup_cache_tag(const char *name
)
262 if (fscache_available())
263 return __fscache_lookup_cache_tag(name
);
269 * fscache_release_cache_tag - Release a cache tag
270 * @tag: The tag to release
272 * Release a reference to a cache referral tag previously looked up.
274 * See Documentation/filesystems/caching/netfs-api.txt for a complete
278 void fscache_release_cache_tag(struct fscache_cache_tag
*tag
)
280 if (fscache_available())
281 __fscache_release_cache_tag(tag
);
285 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
286 * @parent: The cookie that's to be the parent of this one
287 * @def: A description of the cache object, including callback operations
288 * @netfs_data: An arbitrary piece of data to be kept in the cookie to
289 * represent the cache object to the netfs
291 * This function is used to inform FS-Cache about part of an index hierarchy
292 * that can be used to locate files. This is done by requesting a cookie for
293 * each index in the path to the file.
295 * See Documentation/filesystems/caching/netfs-api.txt for a complete
299 struct fscache_cookie
*fscache_acquire_cookie(
300 struct fscache_cookie
*parent
,
301 const struct fscache_cookie_def
*def
,
304 if (fscache_cookie_valid(parent
))
305 return __fscache_acquire_cookie(parent
, def
, netfs_data
);
311 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
313 * @cookie: The cookie being returned
314 * @retire: True if the cache object the cookie represents is to be discarded
316 * This function returns a cookie to the cache, forcibly discarding the
317 * associated cache object if retire is set to true.
319 * See Documentation/filesystems/caching/netfs-api.txt for a complete
323 void fscache_relinquish_cookie(struct fscache_cookie
*cookie
, int retire
)
325 if (fscache_cookie_valid(cookie
))
326 __fscache_relinquish_cookie(cookie
, retire
);
330 * fscache_check_consistency - Request that if the cache is updated
331 * @cookie: The cookie representing the cache object
333 * Request an consistency check from fscache, which passes the request
334 * to the backing cache.
336 * Returns 0 if consistent and -ESTALE if inconsistent. May also
337 * return -ENOMEM and -ERESTARTSYS.
340 int fscache_check_consistency(struct fscache_cookie
*cookie
)
342 if (fscache_cookie_valid(cookie
))
343 return __fscache_check_consistency(cookie
);
349 * fscache_update_cookie - Request that a cache object be updated
350 * @cookie: The cookie representing the cache object
352 * Request an update of the index data for the cache object associated with the
355 * See Documentation/filesystems/caching/netfs-api.txt for a complete
359 void fscache_update_cookie(struct fscache_cookie
*cookie
)
361 if (fscache_cookie_valid(cookie
))
362 __fscache_update_cookie(cookie
);
366 * fscache_pin_cookie - Pin a data-storage cache object in its cache
367 * @cookie: The cookie representing the cache object
369 * Permit data-storage cache objects to be pinned in the cache.
371 * See Documentation/filesystems/caching/netfs-api.txt for a complete
375 int fscache_pin_cookie(struct fscache_cookie
*cookie
)
381 * fscache_pin_cookie - Unpin a data-storage cache object in its cache
382 * @cookie: The cookie representing the cache object
384 * Permit data-storage cache objects to be unpinned from the cache.
386 * See Documentation/filesystems/caching/netfs-api.txt for a complete
390 void fscache_unpin_cookie(struct fscache_cookie
*cookie
)
395 * fscache_attr_changed - Notify cache that an object's attributes changed
396 * @cookie: The cookie representing the cache object
398 * Send a notification to the cache indicating that an object's attributes have
399 * changed. This includes the data size. These attributes will be obtained
400 * through the get_attr() cookie definition op.
402 * See Documentation/filesystems/caching/netfs-api.txt for a complete
406 int fscache_attr_changed(struct fscache_cookie
*cookie
)
408 if (fscache_cookie_valid(cookie
))
409 return __fscache_attr_changed(cookie
);
415 * fscache_invalidate - Notify cache that an object needs invalidation
416 * @cookie: The cookie representing the cache object
418 * Notify the cache that an object is needs to be invalidated and that it
419 * should abort any retrievals or stores it is doing on the cache. The object
420 * is then marked non-caching until such time as the invalidation is complete.
422 * This can be called with spinlocks held.
424 * See Documentation/filesystems/caching/netfs-api.txt for a complete
428 void fscache_invalidate(struct fscache_cookie
*cookie
)
430 if (fscache_cookie_valid(cookie
))
431 __fscache_invalidate(cookie
);
435 * fscache_wait_on_invalidate - Wait for invalidation to complete
436 * @cookie: The cookie representing the cache object
438 * Wait for the invalidation of an object to complete.
440 * See Documentation/filesystems/caching/netfs-api.txt for a complete
444 void fscache_wait_on_invalidate(struct fscache_cookie
*cookie
)
446 if (fscache_cookie_valid(cookie
))
447 __fscache_wait_on_invalidate(cookie
);
451 * fscache_reserve_space - Reserve data space for a cached object
452 * @cookie: The cookie representing the cache object
453 * @i_size: The amount of space to be reserved
455 * Reserve an amount of space in the cache for the cache object attached to a
456 * cookie so that a write to that object within the space can always be
459 * See Documentation/filesystems/caching/netfs-api.txt for a complete
463 int fscache_reserve_space(struct fscache_cookie
*cookie
, loff_t size
)
469 * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
470 * in which to store it
471 * @cookie: The cookie representing the cache object
472 * @page: The netfs page to fill if possible
473 * @end_io_func: The callback to invoke when and if the page is filled
474 * @context: An arbitrary piece of data to pass on to end_io_func()
475 * @gfp: The conditions under which memory allocation should be made
477 * Read a page from the cache, or if that's not possible make a potential
478 * one-block reservation in the cache into which the page may be stored once
479 * fetched from the server.
481 * If the page is not backed by the cache object, or if it there's some reason
482 * it can't be, -ENOBUFS will be returned and nothing more will be done for
485 * Else, if that page is backed by the cache, a read will be initiated directly
486 * to the netfs's page and 0 will be returned by this function. The
487 * end_io_func() callback will be invoked when the operation terminates on a
488 * completion or failure. Note that the callback may be invoked before the
491 * Else, if the page is unbacked, -ENODATA is returned and a block may have
492 * been allocated in the cache.
494 * See Documentation/filesystems/caching/netfs-api.txt for a complete
498 int fscache_read_or_alloc_page(struct fscache_cookie
*cookie
,
500 fscache_rw_complete_t end_io_func
,
504 if (fscache_cookie_valid(cookie
))
505 return __fscache_read_or_alloc_page(cookie
, page
, end_io_func
,
512 * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
513 * blocks in which to store them
514 * @cookie: The cookie representing the cache object
515 * @mapping: The netfs inode mapping to which the pages will be attached
516 * @pages: A list of potential netfs pages to be filled
517 * @nr_pages: Number of pages to be read and/or allocated
518 * @end_io_func: The callback to invoke when and if each page is filled
519 * @context: An arbitrary piece of data to pass on to end_io_func()
520 * @gfp: The conditions under which memory allocation should be made
522 * Read a set of pages from the cache, or if that's not possible, attempt to
523 * make a potential one-block reservation for each page in the cache into which
524 * that page may be stored once fetched from the server.
526 * If some pages are not backed by the cache object, or if it there's some
527 * reason they can't be, -ENOBUFS will be returned and nothing more will be
528 * done for that pages.
530 * Else, if some of the pages are backed by the cache, a read will be initiated
531 * directly to the netfs's page and 0 will be returned by this function. The
532 * end_io_func() callback will be invoked when the operation terminates on a
533 * completion or failure. Note that the callback may be invoked before the
536 * Else, if a page is unbacked, -ENODATA is returned and a block may have
537 * been allocated in the cache.
539 * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
540 * regard to different pages, the return values are prioritised in that order.
541 * Any pages submitted for reading are removed from the pages list.
543 * See Documentation/filesystems/caching/netfs-api.txt for a complete
547 int fscache_read_or_alloc_pages(struct fscache_cookie
*cookie
,
548 struct address_space
*mapping
,
549 struct list_head
*pages
,
551 fscache_rw_complete_t end_io_func
,
555 if (fscache_cookie_valid(cookie
))
556 return __fscache_read_or_alloc_pages(cookie
, mapping
, pages
,
557 nr_pages
, end_io_func
,
564 * fscache_alloc_page - Allocate a block in which to store a page
565 * @cookie: The cookie representing the cache object
566 * @page: The netfs page to allocate a page for
567 * @gfp: The conditions under which memory allocation should be made
569 * Request Allocation a block in the cache in which to store a netfs page
570 * without retrieving any contents from the cache.
572 * If the page is not backed by a file then -ENOBUFS will be returned and
573 * nothing more will be done, and no reservation will be made.
575 * Else, a block will be allocated if one wasn't already, and 0 will be
578 * See Documentation/filesystems/caching/netfs-api.txt for a complete
582 int fscache_alloc_page(struct fscache_cookie
*cookie
,
586 if (fscache_cookie_valid(cookie
))
587 return __fscache_alloc_page(cookie
, page
, gfp
);
593 * fscache_write_page - Request storage of a page in the cache
594 * @cookie: The cookie representing the cache object
595 * @page: The netfs page to store
596 * @gfp: The conditions under which memory allocation should be made
598 * Request the contents of the netfs page be written into the cache. This
599 * request may be ignored if no cache block is currently allocated, in which
600 * case it will return -ENOBUFS.
602 * If a cache block was already allocated, a write will be initiated and 0 will
603 * be returned. The PG_fscache_write page bit is set immediately and will then
604 * be cleared at the completion of the write to indicate the success or failure
605 * of the operation. Note that the completion may happen before the return.
607 * See Documentation/filesystems/caching/netfs-api.txt for a complete
611 int fscache_write_page(struct fscache_cookie
*cookie
,
615 if (fscache_cookie_valid(cookie
))
616 return __fscache_write_page(cookie
, page
, gfp
);
622 * fscache_uncache_page - Indicate that caching is no longer required on a page
623 * @cookie: The cookie representing the cache object
624 * @page: The netfs page that was being cached.
626 * Tell the cache that we no longer want a page to be cached and that it should
627 * remove any knowledge of the netfs page it may have.
629 * Note that this cannot cancel any outstanding I/O operations between this
630 * page and the cache.
632 * See Documentation/filesystems/caching/netfs-api.txt for a complete
636 void fscache_uncache_page(struct fscache_cookie
*cookie
,
639 if (fscache_cookie_valid(cookie
))
640 __fscache_uncache_page(cookie
, page
);
644 * fscache_check_page_write - Ask if a page is being writing to the cache
645 * @cookie: The cookie representing the cache object
646 * @page: The netfs page that is being cached.
648 * Ask the cache if a page is being written to the cache.
650 * See Documentation/filesystems/caching/netfs-api.txt for a complete
654 bool fscache_check_page_write(struct fscache_cookie
*cookie
,
657 if (fscache_cookie_valid(cookie
))
658 return __fscache_check_page_write(cookie
, page
);
663 * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
664 * @cookie: The cookie representing the cache object
665 * @page: The netfs page that is being cached.
667 * Ask the cache to wake us up when a page is no longer being written to the
670 * See Documentation/filesystems/caching/netfs-api.txt for a complete
674 void fscache_wait_on_page_write(struct fscache_cookie
*cookie
,
677 if (fscache_cookie_valid(cookie
))
678 __fscache_wait_on_page_write(cookie
, page
);
682 * fscache_maybe_release_page - Consider releasing a page, cancelling a store
683 * @cookie: The cookie representing the cache object
684 * @page: The netfs page that is being cached.
685 * @gfp: The gfp flags passed to releasepage()
687 * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
688 * releasepage() call. A storage request on the page may cancelled if it is
689 * not currently being processed.
691 * The function returns true if the page no longer has a storage request on it,
692 * and false if a storage request is left in place. If true is returned, the
693 * page will have been passed to fscache_uncache_page(). If false is returned
694 * the page cannot be freed yet.
697 bool fscache_maybe_release_page(struct fscache_cookie
*cookie
,
701 if (fscache_cookie_valid(cookie
) && PageFsCache(page
))
702 return __fscache_maybe_release_page(cookie
, page
, gfp
);
707 * fscache_uncache_all_inode_pages - Uncache all an inode's pages
708 * @cookie: The cookie representing the inode's cache object.
709 * @inode: The inode to uncache pages from.
711 * Uncache all the pages in an inode that are marked PG_fscache, assuming them
712 * to be associated with the given cookie.
714 * This function may sleep. It will wait for pages that are being written out
715 * and will wait whilst the PG_fscache mark is removed by the cache.
718 void fscache_uncache_all_inode_pages(struct fscache_cookie
*cookie
,
721 if (fscache_cookie_valid(cookie
))
722 __fscache_uncache_all_inode_pages(cookie
, inode
);
725 #endif /* _LINUX_FSCACHE_H */