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  * 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 */