include/linux/fscache.h

   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  * 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  */
 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 *);
 180
 181 extern struct fscache_cookie *__fscache_acquire_cookie(
 182         struct fscache_cookie *,
 183         const struct fscache_cookie_def *,
 184         void *);
 185 extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
 186 extern void __fscache_update_cookie(struct fscache_cookie *);
 187 extern int __fscache_attr_changed(struct fscache_cookie *);
 188 extern void __fscache_invalidate(struct fscache_cookie *);
 189 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
 190 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
 191                                         struct page *,
 192                                         fscache_rw_complete_t,
 193                                         void *,
 194                                         gfp_t);
 195 extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
 196                                          struct address_space *,
 197                                          struct list_head *,
 198                                          unsigned *,
 199                                          fscache_rw_complete_t,
 200                                          void *,
 201                                          gfp_t);
 202 extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
 203 extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
 204 extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
 205 extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
 206 extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
 207 extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *,
 208                                          gfp_t);
 209 extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
 210                                               struct inode *);
 211
 212 /**
 213  * fscache_register_netfs - Register a filesystem as desiring caching services
 214  * @netfs: The description of the filesystem
 215  *
 216  * Register a filesystem as desiring caching services if they're available.
 217  *
 218  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 219  * description.
 220  */
 221 static inline
 222 int fscache_register_netfs(struct fscache_netfs *netfs)
 223 {
 224         if (fscache_available())
 225                 return __fscache_register_netfs(netfs);
 226         else
 227                 return 0;
 228 }
 229
 230 /**
 231  * fscache_unregister_netfs - Indicate that a filesystem no longer desires
 232  * caching services
 233  * @netfs: The description of the filesystem
 234  *
 235  * Indicate that a filesystem no longer desires caching services for the
 236  * moment.
 237  *
 238  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 239  * description.
 240  */
 241 static inline
 242 void fscache_unregister_netfs(struct fscache_netfs *netfs)
 243 {
 244         if (fscache_available())
 245                 __fscache_unregister_netfs(netfs);
 246 }
 247
 248 /**
 249  * fscache_lookup_cache_tag - Look up a cache tag
 250  * @name: The name of the tag to search for
 251  *
 252  * Acquire a specific cache referral tag that can be used to select a specific
 253  * cache in which to cache an index.
 254  *
 255  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 256  * description.
 257  */
 258 static inline
 259 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
 260 {
 261         if (fscache_available())
 262                 return __fscache_lookup_cache_tag(name);
 263         else
 264                 return NULL;
 265 }
 266
 267 /**
 268  * fscache_release_cache_tag - Release a cache tag
 269  * @tag: The tag to release
 270  *
 271  * Release a reference to a cache referral tag previously looked up.
 272  *
 273  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 274  * description.
 275  */
 276 static inline
 277 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
 278 {
 279         if (fscache_available())
 280                 __fscache_release_cache_tag(tag);
 281 }
 282
 283 /**
 284  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
 285  * @parent: The cookie that's to be the parent of this one
 286  * @def: A description of the cache object, including callback operations
 287  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
 288  * represent the cache object to the netfs
 289  *
 290  * This function is used to inform FS-Cache about part of an index hierarchy
 291  * that can be used to locate files.  This is done by requesting a cookie for
 292  * each index in the path to the file.
 293  *
 294  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 295  * description.
 296  */
 297 static inline
 298 struct fscache_cookie *fscache_acquire_cookie(
 299         struct fscache_cookie *parent,
 300         const struct fscache_cookie_def *def,
 301         void *netfs_data)
 302 {
 303         if (fscache_cookie_valid(parent))
 304                 return __fscache_acquire_cookie(parent, def, netfs_data);
 305         else
 306                 return NULL;
 307 }
 308
 309 /**
 310  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
 311  * it
 312  * @cookie: The cookie being returned
 313  * @retire: True if the cache object the cookie represents is to be discarded
 314  *
 315  * This function returns a cookie to the cache, forcibly discarding the
 316  * associated cache object if retire is set to true.
 317  *
 318  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 319  * description.
 320  */
 321 static inline
 322 void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 323 {
 324         if (fscache_cookie_valid(cookie))
 325                 __fscache_relinquish_cookie(cookie, retire);
 326 }
 327
 328 /**
 329  * fscache_update_cookie - Request that a cache object be updated
 330  * @cookie: The cookie representing the cache object
 331  *
 332  * Request an update of the index data for the cache object associated with the
 333  * cookie.
 334  *
 335  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 336  * description.
 337  */
 338 static inline
 339 void fscache_update_cookie(struct fscache_cookie *cookie)
 340 {
 341         if (fscache_cookie_valid(cookie))
 342                 __fscache_update_cookie(cookie);
 343 }
 344
 345 /**
 346  * fscache_pin_cookie - Pin a data-storage cache object in its cache
 347  * @cookie: The cookie representing the cache object
 348  *
 349  * Permit data-storage cache objects to be pinned in the cache.
 350  *
 351  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 352  * description.
 353  */
 354 static inline
 355 int fscache_pin_cookie(struct fscache_cookie *cookie)
 356 {
 357         return -ENOBUFS;
 358 }
 359
 360 /**
 361  * fscache_pin_cookie - Unpin a data-storage cache object in its cache
 362  * @cookie: The cookie representing the cache object
 363  *
 364  * Permit data-storage cache objects to be unpinned from the cache.
 365  *
 366  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 367  * description.
 368  */
 369 static inline
 370 void fscache_unpin_cookie(struct fscache_cookie *cookie)
 371 {
 372 }
 373
 374 /**
 375  * fscache_attr_changed - Notify cache that an object's attributes changed
 376  * @cookie: The cookie representing the cache object
 377  *
 378  * Send a notification to the cache indicating that an object's attributes have
 379  * changed.  This includes the data size.  These attributes will be obtained
 380  * through the get_attr() cookie definition op.
 381  *
 382  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 383  * description.
 384  */
 385 static inline
 386 int fscache_attr_changed(struct fscache_cookie *cookie)
 387 {
 388         if (fscache_cookie_valid(cookie))
 389                 return __fscache_attr_changed(cookie);
 390         else
 391                 return -ENOBUFS;
 392 }
 393
 394 /**
 395  * fscache_invalidate - Notify cache that an object needs invalidation
 396  * @cookie: The cookie representing the cache object
 397  *
 398  * Notify the cache that an object is needs to be invalidated and that it
 399  * should abort any retrievals or stores it is doing on the cache.  The object
 400  * is then marked non-caching until such time as the invalidation is complete.
 401  *
 402  * This can be called with spinlocks held.
 403  *
 404  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 405  * description.
 406  */
 407 static inline
 408 void fscache_invalidate(struct fscache_cookie *cookie)
 409 {
 410         if (fscache_cookie_valid(cookie))
 411                 __fscache_invalidate(cookie);
 412 }
 413
 414 /**
 415  * fscache_wait_on_invalidate - Wait for invalidation to complete
 416  * @cookie: The cookie representing the cache object
 417  *
 418  * Wait for the invalidation of an object to complete.
 419  *
 420  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 421  * description.
 422  */
 423 static inline
 424 void fscache_wait_on_invalidate(struct fscache_cookie *cookie)
 425 {
 426         if (fscache_cookie_valid(cookie))
 427                 __fscache_wait_on_invalidate(cookie);
 428 }
 429
 430 /**
 431  * fscache_reserve_space - Reserve data space for a cached object
 432  * @cookie: The cookie representing the cache object
 433  * @i_size: The amount of space to be reserved
 434  *
 435  * Reserve an amount of space in the cache for the cache object attached to a
 436  * cookie so that a write to that object within the space can always be
 437  * honoured.
 438  *
 439  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 440  * description.
 441  */
 442 static inline
 443 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 444 {
 445         return -ENOBUFS;
 446 }
 447
 448 /**
 449  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
 450  * in which to store it
 451  * @cookie: The cookie representing the cache object
 452  * @page: The netfs page to fill if possible
 453  * @end_io_func: The callback to invoke when and if the page is filled
 454  * @context: An arbitrary piece of data to pass on to end_io_func()
 455  * @gfp: The conditions under which memory allocation should be made
 456  *
 457  * Read a page from the cache, or if that's not possible make a potential
 458  * one-block reservation in the cache into which the page may be stored once
 459  * fetched from the server.
 460  *
 461  * If the page is not backed by the cache object, or if it there's some reason
 462  * it can't be, -ENOBUFS will be returned and nothing more will be done for
 463  * that page.
 464  *
 465  * Else, if that page is backed by the cache, a read will be initiated directly
 466  * to the netfs's page and 0 will be returned by this function.  The
 467  * end_io_func() callback will be invoked when the operation terminates on a
 468  * completion or failure.  Note that the callback may be invoked before the
 469  * return.
 470  *
 471  * Else, if the page is unbacked, -ENODATA is returned and a block may have
 472  * been allocated in the cache.
 473  *
 474  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 475  * description.
 476  */
 477 static inline
 478 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 479                                struct page *page,
 480                                fscache_rw_complete_t end_io_func,
 481                                void *context,
 482                                gfp_t gfp)
 483 {
 484         if (fscache_cookie_valid(cookie))
 485                 return __fscache_read_or_alloc_page(cookie, page, end_io_func,
 486                                                     context, gfp);
 487         else
 488                 return -ENOBUFS;
 489 }
 490
 491 /**
 492  * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
 493  * blocks in which to store them
 494  * @cookie: The cookie representing the cache object
 495  * @mapping: The netfs inode mapping to which the pages will be attached
 496  * @pages: A list of potential netfs pages to be filled
 497  * @nr_pages: Number of pages to be read and/or allocated
 498  * @end_io_func: The callback to invoke when and if each page is filled
 499  * @context: An arbitrary piece of data to pass on to end_io_func()
 500  * @gfp: The conditions under which memory allocation should be made
 501  *
 502  * Read a set of pages from the cache, or if that's not possible, attempt to
 503  * make a potential one-block reservation for each page in the cache into which
 504  * that page may be stored once fetched from the server.
 505  *
 506  * If some pages are not backed by the cache object, or if it there's some
 507  * reason they can't be, -ENOBUFS will be returned and nothing more will be
 508  * done for that pages.
 509  *
 510  * Else, if some of the pages are backed by the cache, a read will be initiated
 511  * directly to the netfs's page and 0 will be returned by this function.  The
 512  * end_io_func() callback will be invoked when the operation terminates on a
 513  * completion or failure.  Note that the callback may be invoked before the
 514  * return.
 515  *
 516  * Else, if a page is unbacked, -ENODATA is returned and a block may have
 517  * been allocated in the cache.
 518  *
 519  * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
 520  * regard to different pages, the return values are prioritised in that order.
 521  * Any pages submitted for reading are removed from the pages list.
 522  *
 523  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 524  * description.
 525  */
 526 static inline
 527 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 528                                 struct address_space *mapping,
 529                                 struct list_head *pages,
 530                                 unsigned *nr_pages,
 531                                 fscache_rw_complete_t end_io_func,
 532                                 void *context,
 533                                 gfp_t gfp)
 534 {
 535         if (fscache_cookie_valid(cookie))
 536                 return __fscache_read_or_alloc_pages(cookie, mapping, pages,
 537                                                      nr_pages, end_io_func,
 538                                                      context, gfp);
 539         else
 540                 return -ENOBUFS;
 541 }
 542
 543 /**
 544  * fscache_alloc_page - Allocate a block in which to store a page
 545  * @cookie: The cookie representing the cache object
 546  * @page: The netfs page to allocate a page for
 547  * @gfp: The conditions under which memory allocation should be made
 548  *
 549  * Request Allocation a block in the cache in which to store a netfs page
 550  * without retrieving any contents from the cache.
 551  *
 552  * If the page is not backed by a file then -ENOBUFS will be returned and
 553  * nothing more will be done, and no reservation will be made.
 554  *
 555  * Else, a block will be allocated if one wasn't already, and 0 will be
 556  * returned
 557  *
 558  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 559  * description.
 560  */
 561 static inline
 562 int fscache_alloc_page(struct fscache_cookie *cookie,
 563                        struct page *page,
 564                        gfp_t gfp)
 565 {
 566         if (fscache_cookie_valid(cookie))
 567                 return __fscache_alloc_page(cookie, page, gfp);
 568         else
 569                 return -ENOBUFS;
 570 }
 571
 572 /**
 573  * fscache_write_page - Request storage of a page in the cache
 574  * @cookie: The cookie representing the cache object
 575  * @page: The netfs page to store
 576  * @gfp: The conditions under which memory allocation should be made
 577  *
 578  * Request the contents of the netfs page be written into the cache.  This
 579  * request may be ignored if no cache block is currently allocated, in which
 580  * case it will return -ENOBUFS.
 581  *
 582  * If a cache block was already allocated, a write will be initiated and 0 will
 583  * be returned.  The PG_fscache_write page bit is set immediately and will then
 584  * be cleared at the completion of the write to indicate the success or failure
 585  * of the operation.  Note that the completion may happen before the return.
 586  *
 587  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 588  * description.
 589  */
 590 static inline
 591 int fscache_write_page(struct fscache_cookie *cookie,
 592                        struct page *page,
 593                        gfp_t gfp)
 594 {
 595         if (fscache_cookie_valid(cookie))
 596                 return __fscache_write_page(cookie, page, gfp);
 597         else
 598                 return -ENOBUFS;
 599 }
 600
 601 /**
 602  * fscache_uncache_page - Indicate that caching is no longer required on a page
 603  * @cookie: The cookie representing the cache object
 604  * @page: The netfs page that was being cached.
 605  *
 606  * Tell the cache that we no longer want a page to be cached and that it should
 607  * remove any knowledge of the netfs page it may have.
 608  *
 609  * Note that this cannot cancel any outstanding I/O operations between this
 610  * page and the cache.
 611  *
 612  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 613  * description.
 614  */
 615 static inline
 616 void fscache_uncache_page(struct fscache_cookie *cookie,
 617                           struct page *page)
 618 {
 619         if (fscache_cookie_valid(cookie))
 620                 __fscache_uncache_page(cookie, page);
 621 }
 622
 623 /**
 624  * fscache_check_page_write - Ask if a page is being writing to the cache
 625  * @cookie: The cookie representing the cache object
 626  * @page: The netfs page that is being cached.
 627  *
 628  * Ask the cache if a page is being written to the cache.
 629  *
 630  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 631  * description.
 632  */
 633 static inline
 634 bool fscache_check_page_write(struct fscache_cookie *cookie,
 635                               struct page *page)
 636 {
 637         if (fscache_cookie_valid(cookie))
 638                 return __fscache_check_page_write(cookie, page);
 639         return false;
 640 }
 641
 642 /**
 643  * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
 644  * @cookie: The cookie representing the cache object
 645  * @page: The netfs page that is being cached.
 646  *
 647  * Ask the cache to wake us up when a page is no longer being written to the
 648  * cache.
 649  *
 650  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 651  * description.
 652  */
 653 static inline
 654 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
 655                                 struct page *page)
 656 {
 657         if (fscache_cookie_valid(cookie))
 658                 __fscache_wait_on_page_write(cookie, page);
 659 }
 660
 661 /**
 662  * fscache_maybe_release_page - Consider releasing a page, cancelling a store
 663  * @cookie: The cookie representing the cache object
 664  * @page: The netfs page that is being cached.
 665  * @gfp: The gfp flags passed to releasepage()
 666  *
 667  * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
 668  * releasepage() call.  A storage request on the page may cancelled if it is
 669  * not currently being processed.
 670  *
 671  * The function returns true if the page no longer has a storage request on it,
 672  * and false if a storage request is left in place.  If true is returned, the
 673  * page will have been passed to fscache_uncache_page().  If false is returned
 674  * the page cannot be freed yet.
 675  */
 676 static inline
 677 bool fscache_maybe_release_page(struct fscache_cookie *cookie,
 678                                 struct page *page,
 679                                 gfp_t gfp)
 680 {
 681         if (fscache_cookie_valid(cookie) && PageFsCache(page))
 682                 return __fscache_maybe_release_page(cookie, page, gfp);
 683         return false;
 684 }
 685
 686 /**
 687  * fscache_uncache_all_inode_pages - Uncache all an inode's pages
 688  * @cookie: The cookie representing the inode's cache object.
 689  * @inode: The inode to uncache pages from.
 690  *
 691  * Uncache all the pages in an inode that are marked PG_fscache, assuming them
 692  * to be associated with the given cookie.
 693  *
 694  * This function may sleep.  It will wait for pages that are being written out
 695  * and will wait whilst the PG_fscache mark is removed by the cache.
 696  */
 697 static inline
 698 void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 699                                      struct inode *inode)
 700 {
 701         if (fscache_cookie_valid(cookie))
 702                 __fscache_uncache_all_inode_pages(cookie, inode);
 703 }
 704
 705 #endif /* _LINUX_FSCACHE_H */