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 amount 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 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
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 auxilliary 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 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
143 void (*mark_pages_cached)(void *cookie_netfs_data,
144 struct address_space *mapping,
145 struct pagevec *cached_pvec);
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 *);
182 * fscache_register_netfs - Register a filesystem as desiring caching services
183 * @netfs: The description of the filesystem
185 * Register a filesystem as desiring caching services if they're available.
187 * See Documentation/filesystems/caching/netfs-api.txt for a complete
191 int fscache_register_netfs(struct fscache_netfs *netfs)
193 if (fscache_available())
194 return __fscache_register_netfs(netfs);
200 * fscache_unregister_netfs - Indicate that a filesystem no longer desires
202 * @netfs: The description of the filesystem
204 * Indicate that a filesystem no longer desires caching services for the
207 * See Documentation/filesystems/caching/netfs-api.txt for a complete
211 void fscache_unregister_netfs(struct fscache_netfs *netfs)
213 if (fscache_available())
214 __fscache_unregister_netfs(netfs);
218 * fscache_lookup_cache_tag - Look up a cache tag
219 * @name: The name of the tag to search for
221 * Acquire a specific cache referral tag that can be used to select a specific
222 * cache in which to cache an index.
224 * See Documentation/filesystems/caching/netfs-api.txt for a complete
228 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
230 if (fscache_available())
231 return __fscache_lookup_cache_tag(name);
237 * fscache_release_cache_tag - Release a cache tag
238 * @tag: The tag to release
240 * Release a reference to a cache referral tag previously looked up.
242 * See Documentation/filesystems/caching/netfs-api.txt for a complete
246 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
248 if (fscache_available())
249 __fscache_release_cache_tag(tag);
253 * fscache_acquire_cookie - Acquire a cookie to represent a cache object
254 * @parent: The cookie that's to be the parent of this one
255 * @def: A description of the cache object, including callback operations
256 * @netfs_data: An arbitrary piece of data to be kept in the cookie to
257 * represent the cache object to the netfs
259 * This function is used to inform FS-Cache about part of an index hierarchy
260 * that can be used to locate files. This is done by requesting a cookie for
261 * each index in the path to the file.
263 * See Documentation/filesystems/caching/netfs-api.txt for a complete
267 struct fscache_cookie *fscache_acquire_cookie(
268 struct fscache_cookie *parent,
269 const struct fscache_cookie_def *def,
276 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
278 * @cookie: The cookie being returned
279 * @retire: True if the cache object the cookie represents is to be discarded
281 * This function returns a cookie to the cache, forcibly discarding the
282 * associated cache object if retire is set to true.
284 * See Documentation/filesystems/caching/netfs-api.txt for a complete
288 void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
293 * fscache_update_cookie - Request that a cache object be updated
294 * @cookie: The cookie representing the cache object
296 * Request an update of the index data for the cache object associated with the
299 * See Documentation/filesystems/caching/netfs-api.txt for a complete
303 void fscache_update_cookie(struct fscache_cookie *cookie)
308 * fscache_pin_cookie - Pin a data-storage cache object in its cache
309 * @cookie: The cookie representing the cache object
311 * Permit data-storage cache objects to be pinned in the cache.
313 * See Documentation/filesystems/caching/netfs-api.txt for a complete
317 int fscache_pin_cookie(struct fscache_cookie *cookie)
323 * fscache_pin_cookie - Unpin a data-storage cache object in its cache
324 * @cookie: The cookie representing the cache object
326 * Permit data-storage cache objects to be unpinned from the cache.
328 * See Documentation/filesystems/caching/netfs-api.txt for a complete
332 void fscache_unpin_cookie(struct fscache_cookie *cookie)
337 * fscache_attr_changed - Notify cache that an object's attributes changed
338 * @cookie: The cookie representing the cache object
340 * Send a notification to the cache indicating that an object's attributes have
341 * changed. This includes the data size. These attributes will be obtained
342 * through the get_attr() cookie definition op.
344 * See Documentation/filesystems/caching/netfs-api.txt for a complete
348 int fscache_attr_changed(struct fscache_cookie *cookie)
354 * fscache_reserve_space - Reserve data space for a cached object
355 * @cookie: The cookie representing the cache object
356 * @i_size: The amount of space to be reserved
358 * Reserve an amount of space in the cache for the cache object attached to a
359 * cookie so that a write to that object within the space can always be
362 * See Documentation/filesystems/caching/netfs-api.txt for a complete
366 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
372 * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
373 * in which to store it
374 * @cookie: The cookie representing the cache object
375 * @page: The netfs page to fill if possible
376 * @end_io_func: The callback to invoke when and if the page is filled
377 * @context: An arbitrary piece of data to pass on to end_io_func()
378 * @gfp: The conditions under which memory allocation should be made
380 * Read a page from the cache, or if that's not possible make a potential
381 * one-block reservation in the cache into which the page may be stored once
382 * fetched from the server.
384 * If the page is not backed by the cache object, or if it there's some reason
385 * it can't be, -ENOBUFS will be returned and nothing more will be done for
388 * Else, if that page is backed by the cache, a read will be initiated directly
389 * to the netfs's page and 0 will be returned by this function. The
390 * end_io_func() callback will be invoked when the operation terminates on a
391 * completion or failure. Note that the callback may be invoked before the
394 * Else, if the page is unbacked, -ENODATA is returned and a block may have
395 * been allocated in the cache.
397 * See Documentation/filesystems/caching/netfs-api.txt for a complete
401 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
403 fscache_rw_complete_t end_io_func,
411 * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
412 * blocks in which to store them
413 * @cookie: The cookie representing the cache object
414 * @mapping: The netfs inode mapping to which the pages will be attached
415 * @pages: A list of potential netfs pages to be filled
416 * @end_io_func: The callback to invoke when and if each page is filled
417 * @context: An arbitrary piece of data to pass on to end_io_func()
418 * @gfp: The conditions under which memory allocation should be made
420 * Read a set of pages from the cache, or if that's not possible, attempt to
421 * make a potential one-block reservation for each page in the cache into which
422 * that page may be stored once fetched from the server.
424 * If some pages are not backed by the cache object, or if it there's some
425 * reason they can't be, -ENOBUFS will be returned and nothing more will be
426 * done for that pages.
428 * Else, if some of the pages are backed by the cache, a read will be initiated
429 * directly to the netfs's page and 0 will be returned by this function. The
430 * end_io_func() callback will be invoked when the operation terminates on a
431 * completion or failure. Note that the callback may be invoked before the
434 * Else, if a page is unbacked, -ENODATA is returned and a block may have
435 * been allocated in the cache.
437 * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
438 * regard to different pages, the return values are prioritised in that order.
439 * Any pages submitted for reading are removed from the pages list.
441 * See Documentation/filesystems/caching/netfs-api.txt for a complete
445 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
446 struct address_space *mapping,
447 struct list_head *pages,
449 fscache_rw_complete_t end_io_func,
457 * fscache_alloc_page - Allocate a block in which to store a page
458 * @cookie: The cookie representing the cache object
459 * @page: The netfs page to allocate a page for
460 * @gfp: The conditions under which memory allocation should be made
462 * Request Allocation a block in the cache in which to store a netfs page
463 * without retrieving any contents from the cache.
465 * If the page is not backed by a file then -ENOBUFS will be returned and
466 * nothing more will be done, and no reservation will be made.
468 * Else, a block will be allocated if one wasn't already, and 0 will be
471 * See Documentation/filesystems/caching/netfs-api.txt for a complete
475 int fscache_alloc_page(struct fscache_cookie *cookie,
483 * fscache_write_page - Request storage of a page in the cache
484 * @cookie: The cookie representing the cache object
485 * @page: The netfs page to store
486 * @gfp: The conditions under which memory allocation should be made
488 * Request the contents of the netfs page be written into the cache. This
489 * request may be ignored if no cache block is currently allocated, in which
490 * case it will return -ENOBUFS.
492 * If a cache block was already allocated, a write will be initiated and 0 will
493 * be returned. The PG_fscache_write page bit is set immediately and will then
494 * be cleared at the completion of the write to indicate the success or failure
495 * of the operation. Note that the completion may happen before the return.
497 * See Documentation/filesystems/caching/netfs-api.txt for a complete
501 int fscache_write_page(struct fscache_cookie *cookie,
509 * fscache_uncache_page - Indicate that caching is no longer required on a page
510 * @cookie: The cookie representing the cache object
511 * @page: The netfs page that was being cached.
513 * Tell the cache that we no longer want a page to be cached and that it should
514 * remove any knowledge of the netfs page it may have.
516 * Note that this cannot cancel any outstanding I/O operations between this
517 * page and the cache.
519 * See Documentation/filesystems/caching/netfs-api.txt for a complete
523 void fscache_uncache_page(struct fscache_cookie *cookie,
529 * fscache_check_page_write - Ask if a page is being writing to the cache
530 * @cookie: The cookie representing the cache object
531 * @page: The netfs page that is being cached.
533 * Ask the cache if a page is being written to the cache.
535 * See Documentation/filesystems/caching/netfs-api.txt for a complete
539 bool fscache_check_page_write(struct fscache_cookie *cookie,
546 * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
547 * @cookie: The cookie representing the cache object
548 * @page: The netfs page that is being cached.
550 * Ask the cache to wake us up when a page is no longer being written to the
553 * See Documentation/filesystems/caching/netfs-api.txt for a complete
557 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
562 #endif /* _LINUX_FSCACHE_H */