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Linux/include/linux/fscache.h

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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 
 48 struct pagevec;
 49 struct fscache_cache_tag;
 50 struct fscache_cookie;
 51 struct fscache_netfs;
 52 
 53 typedef void (*fscache_rw_complete_t)(struct page *page,
 54                                       void *context,
 55                                       int error);
 56 
 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 */
 62 };
 63 
 64 /*
 65  * fscache cookie definition
 66  */
 67 struct 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 data 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 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
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 auxiliary 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 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
142          */
143         void (*mark_page_cached)(void *cookie_netfs_data,
144                                  struct address_space *mapping,
145                                  struct page *page);
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  */
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 */
167 };
168 
169 /*
170  * data file or index object cookie
171  * - a file will only appear in one cache
172  * - a request to cache a file may or may not be honoured, subject to
173  *   constraints such as disk space
174  * - indices are created on disk just-in-time
175  */
176 struct fscache_cookie {
177         atomic_t                        usage;          /* number of users of this cookie */
178         atomic_t                        n_children;     /* number of children of this cookie */
179         atomic_t                        n_active;       /* number of active users of netfs ptrs */
180         spinlock_t                      lock;
181         spinlock_t                      stores_lock;    /* lock on page store tree */
182         struct hlist_head               backing_objects; /* object(s) backing this file/index */
183         const struct fscache_cookie_def *def;           /* definition */
184         struct fscache_cookie           *parent;        /* parent of this entry */
185         void                            *netfs_data;    /* back pointer to netfs */
186         struct radix_tree_root          stores;         /* pages to be stored on this cookie */
187 #define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
188 #define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
189 
190         unsigned long                   flags;
191 #define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
192 #define FSCACHE_COOKIE_NO_DATA_YET      1       /* T if new object with no cached data yet */
193 #define FSCACHE_COOKIE_UNAVAILABLE      2       /* T if cookie is unavailable (error, etc) */
194 #define FSCACHE_COOKIE_INVALIDATING     3       /* T if cookie is being invalidated */
195 #define FSCACHE_COOKIE_RELINQUISHED     4       /* T if cookie has been relinquished */
196 #define FSCACHE_COOKIE_ENABLED          5       /* T if cookie is enabled */
197 #define FSCACHE_COOKIE_ENABLEMENT_LOCK  6       /* T if cookie is being en/disabled */
198 };
199 
200 static inline bool fscache_cookie_enabled(struct fscache_cookie *cookie)
201 {
202         return test_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
203 }
204 
205 /*
206  * slow-path functions for when there is actually caching available, and the
207  * netfs does actually have a valid token
208  * - these are not to be called directly
209  * - these are undefined symbols when FS-Cache is not configured and the
210  *   optimiser takes care of not using them
211  */
212 extern int __fscache_register_netfs(struct fscache_netfs *);
213 extern void __fscache_unregister_netfs(struct fscache_netfs *);
214 extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
215 extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
216 
217 extern struct fscache_cookie *__fscache_acquire_cookie(
218         struct fscache_cookie *,
219         const struct fscache_cookie_def *,
220         void *, bool);
221 extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
222 extern int __fscache_check_consistency(struct fscache_cookie *);
223 extern void __fscache_update_cookie(struct fscache_cookie *);
224 extern int __fscache_attr_changed(struct fscache_cookie *);
225 extern void __fscache_invalidate(struct fscache_cookie *);
226 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
227 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
228                                         struct page *,
229                                         fscache_rw_complete_t,
230                                         void *,
231                                         gfp_t);
232 extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
233                                          struct address_space *,
234                                          struct list_head *,
235                                          unsigned *,
236                                          fscache_rw_complete_t,
237                                          void *,
238                                          gfp_t);
239 extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
240 extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
241 extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
242 extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
243 extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
244 extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *,
245                                          gfp_t);
246 extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
247                                               struct inode *);
248 extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
249                                        struct list_head *pages);
250 extern void __fscache_disable_cookie(struct fscache_cookie *, bool);
251 extern void __fscache_enable_cookie(struct fscache_cookie *,
252                                     bool (*)(void *), void *);
253 
254 /**
255  * fscache_register_netfs - Register a filesystem as desiring caching services
256  * @netfs: The description of the filesystem
257  *
258  * Register a filesystem as desiring caching services if they're available.
259  *
260  * See Documentation/filesystems/caching/netfs-api.txt for a complete
261  * description.
262  */
263 static inline
264 int fscache_register_netfs(struct fscache_netfs *netfs)
265 {
266         if (fscache_available())
267                 return __fscache_register_netfs(netfs);
268         else
269                 return 0;
270 }
271 
272 /**
273  * fscache_unregister_netfs - Indicate that a filesystem no longer desires
274  * caching services
275  * @netfs: The description of the filesystem
276  *
277  * Indicate that a filesystem no longer desires caching services for the
278  * moment.
279  *
280  * See Documentation/filesystems/caching/netfs-api.txt for a complete
281  * description.
282  */
283 static inline
284 void fscache_unregister_netfs(struct fscache_netfs *netfs)
285 {
286         if (fscache_available())
287                 __fscache_unregister_netfs(netfs);
288 }
289 
290 /**
291  * fscache_lookup_cache_tag - Look up a cache tag
292  * @name: The name of the tag to search for
293  *
294  * Acquire a specific cache referral tag that can be used to select a specific
295  * cache in which to cache an index.
296  *
297  * See Documentation/filesystems/caching/netfs-api.txt for a complete
298  * description.
299  */
300 static inline
301 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
302 {
303         if (fscache_available())
304                 return __fscache_lookup_cache_tag(name);
305         else
306                 return NULL;
307 }
308 
309 /**
310  * fscache_release_cache_tag - Release a cache tag
311  * @tag: The tag to release
312  *
313  * Release a reference to a cache referral tag previously looked up.
314  *
315  * See Documentation/filesystems/caching/netfs-api.txt for a complete
316  * description.
317  */
318 static inline
319 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
320 {
321         if (fscache_available())
322                 __fscache_release_cache_tag(tag);
323 }
324 
325 /**
326  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
327  * @parent: The cookie that's to be the parent of this one
328  * @def: A description of the cache object, including callback operations
329  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
330  * represent the cache object to the netfs
331  * @enable: Whether or not to enable a data cookie immediately
332  *
333  * This function is used to inform FS-Cache about part of an index hierarchy
334  * that can be used to locate files.  This is done by requesting a cookie for
335  * each index in the path to the file.
336  *
337  * See Documentation/filesystems/caching/netfs-api.txt for a complete
338  * description.
339  */
340 static inline
341 struct fscache_cookie *fscache_acquire_cookie(
342         struct fscache_cookie *parent,
343         const struct fscache_cookie_def *def,
344         void *netfs_data,
345         bool enable)
346 {
347         if (fscache_cookie_valid(parent) && fscache_cookie_enabled(parent))
348                 return __fscache_acquire_cookie(parent, def, netfs_data,
349                                                 enable);
350         else
351                 return NULL;
352 }
353 
354 /**
355  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
356  * it
357  * @cookie: The cookie being returned
358  * @retire: True if the cache object the cookie represents is to be discarded
359  *
360  * This function returns a cookie to the cache, forcibly discarding the
361  * associated cache object if retire is set to true.
362  *
363  * See Documentation/filesystems/caching/netfs-api.txt for a complete
364  * description.
365  */
366 static inline
367 void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
368 {
369         if (fscache_cookie_valid(cookie))
370                 __fscache_relinquish_cookie(cookie, retire);
371 }
372 
373 /**
374  * fscache_check_consistency - Request that if the cache is updated
375  * @cookie: The cookie representing the cache object
376  *
377  * Request an consistency check from fscache, which passes the request
378  * to the backing cache.
379  *
380  * Returns 0 if consistent and -ESTALE if inconsistent.  May also
381  * return -ENOMEM and -ERESTARTSYS.
382  */
383 static inline
384 int fscache_check_consistency(struct fscache_cookie *cookie)
385 {
386         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
387                 return __fscache_check_consistency(cookie);
388         else
389                 return 0;
390 }
391 
392 /**
393  * fscache_update_cookie - Request that a cache object be updated
394  * @cookie: The cookie representing the cache object
395  *
396  * Request an update of the index data for the cache object associated with the
397  * cookie.
398  *
399  * See Documentation/filesystems/caching/netfs-api.txt for a complete
400  * description.
401  */
402 static inline
403 void fscache_update_cookie(struct fscache_cookie *cookie)
404 {
405         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
406                 __fscache_update_cookie(cookie);
407 }
408 
409 /**
410  * fscache_pin_cookie - Pin a data-storage cache object in its cache
411  * @cookie: The cookie representing the cache object
412  *
413  * Permit data-storage cache objects to be pinned in the cache.
414  *
415  * See Documentation/filesystems/caching/netfs-api.txt for a complete
416  * description.
417  */
418 static inline
419 int fscache_pin_cookie(struct fscache_cookie *cookie)
420 {
421         return -ENOBUFS;
422 }
423 
424 /**
425  * fscache_pin_cookie - Unpin a data-storage cache object in its cache
426  * @cookie: The cookie representing the cache object
427  *
428  * Permit data-storage cache objects to be unpinned from the cache.
429  *
430  * See Documentation/filesystems/caching/netfs-api.txt for a complete
431  * description.
432  */
433 static inline
434 void fscache_unpin_cookie(struct fscache_cookie *cookie)
435 {
436 }
437 
438 /**
439  * fscache_attr_changed - Notify cache that an object's attributes changed
440  * @cookie: The cookie representing the cache object
441  *
442  * Send a notification to the cache indicating that an object's attributes have
443  * changed.  This includes the data size.  These attributes will be obtained
444  * through the get_attr() cookie definition op.
445  *
446  * See Documentation/filesystems/caching/netfs-api.txt for a complete
447  * description.
448  */
449 static inline
450 int fscache_attr_changed(struct fscache_cookie *cookie)
451 {
452         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
453                 return __fscache_attr_changed(cookie);
454         else
455                 return -ENOBUFS;
456 }
457 
458 /**
459  * fscache_invalidate - Notify cache that an object needs invalidation
460  * @cookie: The cookie representing the cache object
461  *
462  * Notify the cache that an object is needs to be invalidated and that it
463  * should abort any retrievals or stores it is doing on the cache.  The object
464  * is then marked non-caching until such time as the invalidation is complete.
465  *
466  * This can be called with spinlocks held.
467  *
468  * See Documentation/filesystems/caching/netfs-api.txt for a complete
469  * description.
470  */
471 static inline
472 void fscache_invalidate(struct fscache_cookie *cookie)
473 {
474         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
475                 __fscache_invalidate(cookie);
476 }
477 
478 /**
479  * fscache_wait_on_invalidate - Wait for invalidation to complete
480  * @cookie: The cookie representing the cache object
481  *
482  * Wait for the invalidation of an object to complete.
483  *
484  * See Documentation/filesystems/caching/netfs-api.txt for a complete
485  * description.
486  */
487 static inline
488 void fscache_wait_on_invalidate(struct fscache_cookie *cookie)
489 {
490         if (fscache_cookie_valid(cookie))
491                 __fscache_wait_on_invalidate(cookie);
492 }
493 
494 /**
495  * fscache_reserve_space - Reserve data space for a cached object
496  * @cookie: The cookie representing the cache object
497  * @i_size: The amount of space to be reserved
498  *
499  * Reserve an amount of space in the cache for the cache object attached to a
500  * cookie so that a write to that object within the space can always be
501  * honoured.
502  *
503  * See Documentation/filesystems/caching/netfs-api.txt for a complete
504  * description.
505  */
506 static inline
507 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
508 {
509         return -ENOBUFS;
510 }
511 
512 /**
513  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
514  * in which to store it
515  * @cookie: The cookie representing the cache object
516  * @page: The netfs page to fill if possible
517  * @end_io_func: The callback to invoke when and if the page is filled
518  * @context: An arbitrary piece of data to pass on to end_io_func()
519  * @gfp: The conditions under which memory allocation should be made
520  *
521  * Read a page from the cache, or if that's not possible make a potential
522  * one-block reservation in the cache into which the page may be stored once
523  * fetched from the server.
524  *
525  * If the page is not backed by the cache object, or if it there's some reason
526  * it can't be, -ENOBUFS will be returned and nothing more will be done for
527  * that page.
528  *
529  * Else, if that page is backed by the cache, a read will be initiated directly
530  * to the netfs's page and 0 will be returned by this function.  The
531  * end_io_func() callback will be invoked when the operation terminates on a
532  * completion or failure.  Note that the callback may be invoked before the
533  * return.
534  *
535  * Else, if the page is unbacked, -ENODATA is returned and a block may have
536  * been allocated in the cache.
537  *
538  * See Documentation/filesystems/caching/netfs-api.txt for a complete
539  * description.
540  */
541 static inline
542 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
543                                struct page *page,
544                                fscache_rw_complete_t end_io_func,
545                                void *context,
546                                gfp_t gfp)
547 {
548         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
549                 return __fscache_read_or_alloc_page(cookie, page, end_io_func,
550                                                     context, gfp);
551         else
552                 return -ENOBUFS;
553 }
554 
555 /**
556  * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
557  * blocks in which to store them
558  * @cookie: The cookie representing the cache object
559  * @mapping: The netfs inode mapping to which the pages will be attached
560  * @pages: A list of potential netfs pages to be filled
561  * @nr_pages: Number of pages to be read and/or allocated
562  * @end_io_func: The callback to invoke when and if each page is filled
563  * @context: An arbitrary piece of data to pass on to end_io_func()
564  * @gfp: The conditions under which memory allocation should be made
565  *
566  * Read a set of pages from the cache, or if that's not possible, attempt to
567  * make a potential one-block reservation for each page in the cache into which
568  * that page may be stored once fetched from the server.
569  *
570  * If some pages are not backed by the cache object, or if it there's some
571  * reason they can't be, -ENOBUFS will be returned and nothing more will be
572  * done for that pages.
573  *
574  * Else, if some of the pages are backed by the cache, a read will be initiated
575  * directly to the netfs's page and 0 will be returned by this function.  The
576  * end_io_func() callback will be invoked when the operation terminates on a
577  * completion or failure.  Note that the callback may be invoked before the
578  * return.
579  *
580  * Else, if a page is unbacked, -ENODATA is returned and a block may have
581  * been allocated in the cache.
582  *
583  * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
584  * regard to different pages, the return values are prioritised in that order.
585  * Any pages submitted for reading are removed from the pages list.
586  *
587  * See Documentation/filesystems/caching/netfs-api.txt for a complete
588  * description.
589  */
590 static inline
591 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
592                                 struct address_space *mapping,
593                                 struct list_head *pages,
594                                 unsigned *nr_pages,
595                                 fscache_rw_complete_t end_io_func,
596                                 void *context,
597                                 gfp_t gfp)
598 {
599         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
600                 return __fscache_read_or_alloc_pages(cookie, mapping, pages,
601                                                      nr_pages, end_io_func,
602                                                      context, gfp);
603         else
604                 return -ENOBUFS;
605 }
606 
607 /**
608  * fscache_alloc_page - Allocate a block in which to store a page
609  * @cookie: The cookie representing the cache object
610  * @page: The netfs page to allocate a page for
611  * @gfp: The conditions under which memory allocation should be made
612  *
613  * Request Allocation a block in the cache in which to store a netfs page
614  * without retrieving any contents from the cache.
615  *
616  * If the page is not backed by a file then -ENOBUFS will be returned and
617  * nothing more will be done, and no reservation will be made.
618  *
619  * Else, a block will be allocated if one wasn't already, and 0 will be
620  * returned
621  *
622  * See Documentation/filesystems/caching/netfs-api.txt for a complete
623  * description.
624  */
625 static inline
626 int fscache_alloc_page(struct fscache_cookie *cookie,
627                        struct page *page,
628                        gfp_t gfp)
629 {
630         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
631                 return __fscache_alloc_page(cookie, page, gfp);
632         else
633                 return -ENOBUFS;
634 }
635 
636 /**
637  * fscache_readpages_cancel - Cancel read/alloc on pages
638  * @cookie: The cookie representing the inode's cache object.
639  * @pages: The netfs pages that we canceled write on in readpages()
640  *
641  * Uncache/unreserve the pages reserved earlier in readpages() via
642  * fscache_readpages_or_alloc() and similar.  In most successful caches in
643  * readpages() this doesn't do anything.  In cases when the underlying netfs's
644  * readahead failed we need to clean up the pagelist (unmark and uncache).
645  *
646  * This function may sleep as it may have to clean up disk state.
647  */
648 static inline
649 void fscache_readpages_cancel(struct fscache_cookie *cookie,
650                               struct list_head *pages)
651 {
652         if (fscache_cookie_valid(cookie))
653                 __fscache_readpages_cancel(cookie, pages);
654 }
655 
656 /**
657  * fscache_write_page - Request storage of a page in the cache
658  * @cookie: The cookie representing the cache object
659  * @page: The netfs page to store
660  * @gfp: The conditions under which memory allocation should be made
661  *
662  * Request the contents of the netfs page be written into the cache.  This
663  * request may be ignored if no cache block is currently allocated, in which
664  * case it will return -ENOBUFS.
665  *
666  * If a cache block was already allocated, a write will be initiated and 0 will
667  * be returned.  The PG_fscache_write page bit is set immediately and will then
668  * be cleared at the completion of the write to indicate the success or failure
669  * of the operation.  Note that the completion may happen before the return.
670  *
671  * See Documentation/filesystems/caching/netfs-api.txt for a complete
672  * description.
673  */
674 static inline
675 int fscache_write_page(struct fscache_cookie *cookie,
676                        struct page *page,
677                        gfp_t gfp)
678 {
679         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
680                 return __fscache_write_page(cookie, page, gfp);
681         else
682                 return -ENOBUFS;
683 }
684 
685 /**
686  * fscache_uncache_page - Indicate that caching is no longer required on a page
687  * @cookie: The cookie representing the cache object
688  * @page: The netfs page that was being cached.
689  *
690  * Tell the cache that we no longer want a page to be cached and that it should
691  * remove any knowledge of the netfs page it may have.
692  *
693  * Note that this cannot cancel any outstanding I/O operations between this
694  * page and the cache.
695  *
696  * See Documentation/filesystems/caching/netfs-api.txt for a complete
697  * description.
698  */
699 static inline
700 void fscache_uncache_page(struct fscache_cookie *cookie,
701                           struct page *page)
702 {
703         if (fscache_cookie_valid(cookie))
704                 __fscache_uncache_page(cookie, page);
705 }
706 
707 /**
708  * fscache_check_page_write - Ask if a page is being writing to the cache
709  * @cookie: The cookie representing the cache object
710  * @page: The netfs page that is being cached.
711  *
712  * Ask the cache if a page is being written to the cache.
713  *
714  * See Documentation/filesystems/caching/netfs-api.txt for a complete
715  * description.
716  */
717 static inline
718 bool fscache_check_page_write(struct fscache_cookie *cookie,
719                               struct page *page)
720 {
721         if (fscache_cookie_valid(cookie))
722                 return __fscache_check_page_write(cookie, page);
723         return false;
724 }
725 
726 /**
727  * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
728  * @cookie: The cookie representing the cache object
729  * @page: The netfs page that is being cached.
730  *
731  * Ask the cache to wake us up when a page is no longer being written to the
732  * cache.
733  *
734  * See Documentation/filesystems/caching/netfs-api.txt for a complete
735  * description.
736  */
737 static inline
738 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
739                                 struct page *page)
740 {
741         if (fscache_cookie_valid(cookie))
742                 __fscache_wait_on_page_write(cookie, page);
743 }
744 
745 /**
746  * fscache_maybe_release_page - Consider releasing a page, cancelling a store
747  * @cookie: The cookie representing the cache object
748  * @page: The netfs page that is being cached.
749  * @gfp: The gfp flags passed to releasepage()
750  *
751  * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
752  * releasepage() call.  A storage request on the page may cancelled if it is
753  * not currently being processed.
754  *
755  * The function returns true if the page no longer has a storage request on it,
756  * and false if a storage request is left in place.  If true is returned, the
757  * page will have been passed to fscache_uncache_page().  If false is returned
758  * the page cannot be freed yet.
759  */
760 static inline
761 bool fscache_maybe_release_page(struct fscache_cookie *cookie,
762                                 struct page *page,
763                                 gfp_t gfp)
764 {
765         if (fscache_cookie_valid(cookie) && PageFsCache(page))
766                 return __fscache_maybe_release_page(cookie, page, gfp);
767         return false;
768 }
769 
770 /**
771  * fscache_uncache_all_inode_pages - Uncache all an inode's pages
772  * @cookie: The cookie representing the inode's cache object.
773  * @inode: The inode to uncache pages from.
774  *
775  * Uncache all the pages in an inode that are marked PG_fscache, assuming them
776  * to be associated with the given cookie.
777  *
778  * This function may sleep.  It will wait for pages that are being written out
779  * and will wait whilst the PG_fscache mark is removed by the cache.
780  */
781 static inline
782 void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
783                                      struct inode *inode)
784 {
785         if (fscache_cookie_valid(cookie))
786                 __fscache_uncache_all_inode_pages(cookie, inode);
787 }
788 
789 /**
790  * fscache_disable_cookie - Disable a cookie
791  * @cookie: The cookie representing the cache object
792  * @invalidate: Invalidate the backing object
793  *
794  * Disable a cookie from accepting further alloc, read, write, invalidate,
795  * update or acquire operations.  Outstanding operations can still be waited
796  * upon and pages can still be uncached and the cookie relinquished.
797  *
798  * This will not return until all outstanding operations have completed.
799  *
800  * If @invalidate is set, then the backing object will be invalidated and
801  * detached, otherwise it will just be detached.
802  */
803 static inline
804 void fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate)
805 {
806         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
807                 __fscache_disable_cookie(cookie, invalidate);
808 }
809 
810 /**
811  * fscache_enable_cookie - Reenable a cookie
812  * @cookie: The cookie representing the cache object
813  * @can_enable: A function to permit enablement once lock is held
814  * @data: Data for can_enable()
815  *
816  * Reenable a previously disabled cookie, allowing it to accept further alloc,
817  * read, write, invalidate, update or acquire operations.  An attempt will be
818  * made to immediately reattach the cookie to a backing object.
819  *
820  * The can_enable() function is called (if not NULL) once the enablement lock
821  * is held to rule on whether enablement is still permitted to go ahead.
822  */
823 static inline
824 void fscache_enable_cookie(struct fscache_cookie *cookie,
825                            bool (*can_enable)(void *data),
826                            void *data)
827 {
828         if (fscache_cookie_valid(cookie) && !fscache_cookie_enabled(cookie))
829                 __fscache_enable_cookie(cookie, can_enable, data);
830 }
831 
832 #endif /* _LINUX_FSCACHE_H */
833 

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