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
 148 /*
 149  * fscache cached network filesystem type
 150  * - name, version and ops must be filled in before registration
 151  * - all other fields will be set during registration
 152  */
 153 struct fscache_netfs {
 154         uint32_t                        version;        /* indexing version */
 155         const char                      *name;          /* filesystem name */
 156         struct fscache_cookie           *primary_index;
 157         struct list_head                link;           /* internal link */
 158 };
 159
 160 /*
 161  * data file or index object cookie
 162  * - a file will only appear in one cache
 163  * - a request to cache a file may or may not be honoured, subject to
 164  *   constraints such as disk space
 165  * - indices are created on disk just-in-time
 166  */
 167 struct fscache_cookie {
 168         atomic_t                        usage;          /* number of users of this cookie */
 169         atomic_t                        n_children;     /* number of children of this cookie */
 170         atomic_t                        n_active;       /* number of active users of netfs ptrs */
 171         spinlock_t                      lock;
 172         spinlock_t                      stores_lock;    /* lock on page store tree */
 173         struct hlist_head               backing_objects; /* object(s) backing this file/index */
 174         const struct fscache_cookie_def *def;           /* definition */
 175         struct fscache_cookie           *parent;        /* parent of this entry */
 176         void                            *netfs_data;    /* back pointer to netfs */
 177         struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 178 #define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 179 #define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
 180
 181         unsigned long                   flags;
 182 #define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 183 #define FSCACHE_COOKIE_NO_DATA_YET      1       /* T if new object with no cached data yet */
 184 #define FSCACHE_COOKIE_UNAVAILABLE      2       /* T if cookie is unavailable (error, etc) */
 185 #define FSCACHE_COOKIE_INVALIDATING     3       /* T if cookie is being invalidated */
 186 #define FSCACHE_COOKIE_RELINQUISHED     4       /* T if cookie has been relinquished */
 187 #define FSCACHE_COOKIE_ENABLED          5       /* T if cookie is enabled */
 188 #define FSCACHE_COOKIE_ENABLEMENT_LOCK  6       /* T if cookie is being en/disabled */
 189 };
 190
 191 static inline bool fscache_cookie_enabled(struct fscache_cookie *cookie)
 192 {
 193         return test_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 194 }
 195
 196 /*
 197  * slow-path functions for when there is actually caching available, and the
 198  * netfs does actually have a valid token
 199  * - these are not to be called directly
 200  * - these are undefined symbols when FS-Cache is not configured and the
 201  *   optimiser takes care of not using them
 202  */
 203 extern int __fscache_register_netfs(struct fscache_netfs *);
 204 extern void __fscache_unregister_netfs(struct fscache_netfs *);
 205 extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
 206 extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
 207
 208 extern struct fscache_cookie *__fscache_acquire_cookie(
 209         struct fscache_cookie *,
 210         const struct fscache_cookie_def *,
 211         void *, bool);
 212 extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
 213 extern int __fscache_check_consistency(struct fscache_cookie *);
 214 extern void __fscache_update_cookie(struct fscache_cookie *);
 215 extern int __fscache_attr_changed(struct fscache_cookie *);
 216 extern void __fscache_invalidate(struct fscache_cookie *);
 217 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
 218 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
 219                                         struct page *,
 220                                         fscache_rw_complete_t,
 221                                         void *,
 222                                         gfp_t);
 223 extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
 224                                          struct address_space *,
 225                                          struct list_head *,
 226                                          unsigned *,
 227                                          fscache_rw_complete_t,
 228                                          void *,
 229                                          gfp_t);
 230 extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
 231 extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
 232 extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
 233 extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
 234 extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
 235 extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *,
 236                                          gfp_t);
 237 extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
 238                                               struct inode *);
 239 extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 240                                        struct list_head *pages);
 241 extern void __fscache_disable_cookie(struct fscache_cookie *, bool);
 242 extern void __fscache_enable_cookie(struct fscache_cookie *,
 243                                     bool (*)(void *), void *);
 244
 245 /**
 246  * fscache_register_netfs - Register a filesystem as desiring caching services
 247  * @netfs: The description of the filesystem
 248  *
 249  * Register a filesystem as desiring caching services if they're available.
 250  *
 251  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 252  * description.
 253  */
 254 static inline
 255 int fscache_register_netfs(struct fscache_netfs *netfs)
 256 {
 257         if (fscache_available())
 258                 return __fscache_register_netfs(netfs);
 259         else
 260                 return 0;
 261 }
 262
 263 /**
 264  * fscache_unregister_netfs - Indicate that a filesystem no longer desires
 265  * caching services
 266  * @netfs: The description of the filesystem
 267  *
 268  * Indicate that a filesystem no longer desires caching services for the
 269  * moment.
 270  *
 271  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 272  * description.
 273  */
 274 static inline
 275 void fscache_unregister_netfs(struct fscache_netfs *netfs)
 276 {
 277         if (fscache_available())
 278                 __fscache_unregister_netfs(netfs);
 279 }
 280
 281 /**
 282  * fscache_lookup_cache_tag - Look up a cache tag
 283  * @name: The name of the tag to search for
 284  *
 285  * Acquire a specific cache referral tag that can be used to select a specific
 286  * cache in which to cache an index.
 287  *
 288  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 289  * description.
 290  */
 291 static inline
 292 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
 293 {
 294         if (fscache_available())
 295                 return __fscache_lookup_cache_tag(name);
 296         else
 297                 return NULL;
 298 }
 299
 300 /**
 301  * fscache_release_cache_tag - Release a cache tag
 302  * @tag: The tag to release
 303  *
 304  * Release a reference to a cache referral tag previously looked up.
 305  *
 306  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 307  * description.
 308  */
 309 static inline
 310 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
 311 {
 312         if (fscache_available())
 313                 __fscache_release_cache_tag(tag);
 314 }
 315
 316 /**
 317  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
 318  * @parent: The cookie that's to be the parent of this one
 319  * @def: A description of the cache object, including callback operations
 320  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
 321  * represent the cache object to the netfs
 322  * @enable: Whether or not to enable a data cookie immediately
 323  *
 324  * This function is used to inform FS-Cache about part of an index hierarchy
 325  * that can be used to locate files.  This is done by requesting a cookie for
 326  * each index in the path to the file.
 327  *
 328  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 329  * description.
 330  */
 331 static inline
 332 struct fscache_cookie *fscache_acquire_cookie(
 333         struct fscache_cookie *parent,
 334         const struct fscache_cookie_def *def,
 335         void *netfs_data,
 336         bool enable)
 337 {
 338         if (fscache_cookie_valid(parent) && fscache_cookie_enabled(parent))
 339                 return __fscache_acquire_cookie(parent, def, netfs_data,
 340                                                 enable);
 341         else
 342                 return NULL;
 343 }
 344
 345 /**
 346  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
 347  * it
 348  * @cookie: The cookie being returned
 349  * @retire: True if the cache object the cookie represents is to be discarded
 350  *
 351  * This function returns a cookie to the cache, forcibly discarding the
 352  * associated cache object if retire is set to true.
 353  *
 354  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 355  * description.
 356  */
 357 static inline
 358 void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
 359 {
 360         if (fscache_cookie_valid(cookie))
 361                 __fscache_relinquish_cookie(cookie, retire);
 362 }
 363
 364 /**
 365  * fscache_check_consistency - Request that if the cache is updated
 366  * @cookie: The cookie representing the cache object
 367  *
 368  * Request an consistency check from fscache, which passes the request
 369  * to the backing cache.
 370  *
 371  * Returns 0 if consistent and -ESTALE if inconsistent.  May also
 372  * return -ENOMEM and -ERESTARTSYS.
 373  */
 374 static inline
 375 int fscache_check_consistency(struct fscache_cookie *cookie)
 376 {
 377         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 378                 return __fscache_check_consistency(cookie);
 379         else
 380                 return 0;
 381 }
 382
 383 /**
 384  * fscache_update_cookie - Request that a cache object be updated
 385  * @cookie: The cookie representing the cache object
 386  *
 387  * Request an update of the index data for the cache object associated with the
 388  * cookie.
 389  *
 390  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 391  * description.
 392  */
 393 static inline
 394 void fscache_update_cookie(struct fscache_cookie *cookie)
 395 {
 396         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 397                 __fscache_update_cookie(cookie);
 398 }
 399
 400 /**
 401  * fscache_pin_cookie - Pin a data-storage cache object in its cache
 402  * @cookie: The cookie representing the cache object
 403  *
 404  * Permit data-storage cache objects to be pinned in the cache.
 405  *
 406  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 407  * description.
 408  */
 409 static inline
 410 int fscache_pin_cookie(struct fscache_cookie *cookie)
 411 {
 412         return -ENOBUFS;
 413 }
 414
 415 /**
 416  * fscache_pin_cookie - Unpin a data-storage cache object in its cache
 417  * @cookie: The cookie representing the cache object
 418  *
 419  * Permit data-storage cache objects to be unpinned from the cache.
 420  *
 421  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 422  * description.
 423  */
 424 static inline
 425 void fscache_unpin_cookie(struct fscache_cookie *cookie)
 426 {
 427 }
 428
 429 /**
 430  * fscache_attr_changed - Notify cache that an object's attributes changed
 431  * @cookie: The cookie representing the cache object
 432  *
 433  * Send a notification to the cache indicating that an object's attributes have
 434  * changed.  This includes the data size.  These attributes will be obtained
 435  * through the get_attr() cookie definition op.
 436  *
 437  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 438  * description.
 439  */
 440 static inline
 441 int fscache_attr_changed(struct fscache_cookie *cookie)
 442 {
 443         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 444                 return __fscache_attr_changed(cookie);
 445         else
 446                 return -ENOBUFS;
 447 }
 448
 449 /**
 450  * fscache_invalidate - Notify cache that an object needs invalidation
 451  * @cookie: The cookie representing the cache object
 452  *
 453  * Notify the cache that an object is needs to be invalidated and that it
 454  * should abort any retrievals or stores it is doing on the cache.  The object
 455  * is then marked non-caching until such time as the invalidation is complete.
 456  *
 457  * This can be called with spinlocks held.
 458  *
 459  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 460  * description.
 461  */
 462 static inline
 463 void fscache_invalidate(struct fscache_cookie *cookie)
 464 {
 465         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 466                 __fscache_invalidate(cookie);
 467 }
 468
 469 /**
 470  * fscache_wait_on_invalidate - Wait for invalidation to complete
 471  * @cookie: The cookie representing the cache object
 472  *
 473  * Wait for the invalidation of an object to complete.
 474  *
 475  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 476  * description.
 477  */
 478 static inline
 479 void fscache_wait_on_invalidate(struct fscache_cookie *cookie)
 480 {
 481         if (fscache_cookie_valid(cookie))
 482                 __fscache_wait_on_invalidate(cookie);
 483 }
 484
 485 /**
 486  * fscache_reserve_space - Reserve data space for a cached object
 487  * @cookie: The cookie representing the cache object
 488  * @i_size: The amount of space to be reserved
 489  *
 490  * Reserve an amount of space in the cache for the cache object attached to a
 491  * cookie so that a write to that object within the space can always be
 492  * honoured.
 493  *
 494  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 495  * description.
 496  */
 497 static inline
 498 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 499 {
 500         return -ENOBUFS;
 501 }
 502
 503 /**
 504  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
 505  * in which to store it
 506  * @cookie: The cookie representing the cache object
 507  * @page: The netfs page to fill if possible
 508  * @end_io_func: The callback to invoke when and if the page is filled
 509  * @context: An arbitrary piece of data to pass on to end_io_func()
 510  * @gfp: The conditions under which memory allocation should be made
 511  *
 512  * Read a page from the cache, or if that's not possible make a potential
 513  * one-block reservation in the cache into which the page may be stored once
 514  * fetched from the server.
 515  *
 516  * If the page is not backed by the cache object, or if it there's some reason
 517  * it can't be, -ENOBUFS will be returned and nothing more will be done for
 518  * that page.
 519  *
 520  * Else, if that page is backed by the cache, a read will be initiated directly
 521  * to the netfs's page and 0 will be returned by this function.  The
 522  * end_io_func() callback will be invoked when the operation terminates on a
 523  * completion or failure.  Note that the callback may be invoked before the
 524  * return.
 525  *
 526  * Else, if the page is unbacked, -ENODATA is returned and a block may have
 527  * been allocated in the cache.
 528  *
 529  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 530  * description.
 531  */
 532 static inline
 533 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 534                                struct page *page,
 535                                fscache_rw_complete_t end_io_func,
 536                                void *context,
 537                                gfp_t gfp)
 538 {
 539         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 540                 return __fscache_read_or_alloc_page(cookie, page, end_io_func,
 541                                                     context, gfp);
 542         else
 543                 return -ENOBUFS;
 544 }
 545
 546 /**
 547  * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
 548  * blocks in which to store them
 549  * @cookie: The cookie representing the cache object
 550  * @mapping: The netfs inode mapping to which the pages will be attached
 551  * @pages: A list of potential netfs pages to be filled
 552  * @nr_pages: Number of pages to be read and/or allocated
 553  * @end_io_func: The callback to invoke when and if each page is filled
 554  * @context: An arbitrary piece of data to pass on to end_io_func()
 555  * @gfp: The conditions under which memory allocation should be made
 556  *
 557  * Read a set of pages from the cache, or if that's not possible, attempt to
 558  * make a potential one-block reservation for each page in the cache into which
 559  * that page may be stored once fetched from the server.
 560  *
 561  * If some pages are not backed by the cache object, or if it there's some
 562  * reason they can't be, -ENOBUFS will be returned and nothing more will be
 563  * done for that pages.
 564  *
 565  * Else, if some of the pages are backed by the cache, a read will be initiated
 566  * directly to the netfs's page and 0 will be returned by this function.  The
 567  * end_io_func() callback will be invoked when the operation terminates on a
 568  * completion or failure.  Note that the callback may be invoked before the
 569  * return.
 570  *
 571  * Else, if a page is unbacked, -ENODATA is returned and a block may have
 572  * been allocated in the cache.
 573  *
 574  * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
 575  * regard to different pages, the return values are prioritised in that order.
 576  * Any pages submitted for reading are removed from the pages list.
 577  *
 578  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 579  * description.
 580  */
 581 static inline
 582 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 583                                 struct address_space *mapping,
 584                                 struct list_head *pages,
 585                                 unsigned *nr_pages,
 586                                 fscache_rw_complete_t end_io_func,
 587                                 void *context,
 588                                 gfp_t gfp)
 589 {
 590         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 591                 return __fscache_read_or_alloc_pages(cookie, mapping, pages,
 592                                                      nr_pages, end_io_func,
 593                                                      context, gfp);
 594         else
 595                 return -ENOBUFS;
 596 }
 597
 598 /**
 599  * fscache_alloc_page - Allocate a block in which to store a page
 600  * @cookie: The cookie representing the cache object
 601  * @page: The netfs page to allocate a page for
 602  * @gfp: The conditions under which memory allocation should be made
 603  *
 604  * Request Allocation a block in the cache in which to store a netfs page
 605  * without retrieving any contents from the cache.
 606  *
 607  * If the page is not backed by a file then -ENOBUFS will be returned and
 608  * nothing more will be done, and no reservation will be made.
 609  *
 610  * Else, a block will be allocated if one wasn't already, and 0 will be
 611  * returned
 612  *
 613  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 614  * description.
 615  */
 616 static inline
 617 int fscache_alloc_page(struct fscache_cookie *cookie,
 618                        struct page *page,
 619                        gfp_t gfp)
 620 {
 621         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 622                 return __fscache_alloc_page(cookie, page, gfp);
 623         else
 624                 return -ENOBUFS;
 625 }
 626
 627 /**
 628  * fscache_readpages_cancel - Cancel read/alloc on pages
 629  * @cookie: The cookie representing the inode's cache object.
 630  * @pages: The netfs pages that we canceled write on in readpages()
 631  *
 632  * Uncache/unreserve the pages reserved earlier in readpages() via
 633  * fscache_readpages_or_alloc() and similar.  In most successful caches in
 634  * readpages() this doesn't do anything.  In cases when the underlying netfs's
 635  * readahead failed we need to clean up the pagelist (unmark and uncache).
 636  *
 637  * This function may sleep as it may have to clean up disk state.
 638  */
 639 static inline
 640 void fscache_readpages_cancel(struct fscache_cookie *cookie,
 641                               struct list_head *pages)
 642 {
 643         if (fscache_cookie_valid(cookie))
 644                 __fscache_readpages_cancel(cookie, pages);
 645 }
 646
 647 /**
 648  * fscache_write_page - Request storage of a page in the cache
 649  * @cookie: The cookie representing the cache object
 650  * @page: The netfs page to store
 651  * @gfp: The conditions under which memory allocation should be made
 652  *
 653  * Request the contents of the netfs page be written into the cache.  This
 654  * request may be ignored if no cache block is currently allocated, in which
 655  * case it will return -ENOBUFS.
 656  *
 657  * If a cache block was already allocated, a write will be initiated and 0 will
 658  * be returned.  The PG_fscache_write page bit is set immediately and will then
 659  * be cleared at the completion of the write to indicate the success or failure
 660  * of the operation.  Note that the completion may happen before the return.
 661  *
 662  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 663  * description.
 664  */
 665 static inline
 666 int fscache_write_page(struct fscache_cookie *cookie,
 667                        struct page *page,
 668                        gfp_t gfp)
 669 {
 670         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 671                 return __fscache_write_page(cookie, page, gfp);
 672         else
 673                 return -ENOBUFS;
 674 }
 675
 676 /**
 677  * fscache_uncache_page - Indicate that caching is no longer required on a page
 678  * @cookie: The cookie representing the cache object
 679  * @page: The netfs page that was being cached.
 680  *
 681  * Tell the cache that we no longer want a page to be cached and that it should
 682  * remove any knowledge of the netfs page it may have.
 683  *
 684  * Note that this cannot cancel any outstanding I/O operations between this
 685  * page and the cache.
 686  *
 687  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 688  * description.
 689  */
 690 static inline
 691 void fscache_uncache_page(struct fscache_cookie *cookie,
 692                           struct page *page)
 693 {
 694         if (fscache_cookie_valid(cookie))
 695                 __fscache_uncache_page(cookie, page);
 696 }
 697
 698 /**
 699  * fscache_check_page_write - Ask if a page is being writing to the cache
 700  * @cookie: The cookie representing the cache object
 701  * @page: The netfs page that is being cached.
 702  *
 703  * Ask the cache if a page is being written to the cache.
 704  *
 705  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 706  * description.
 707  */
 708 static inline
 709 bool fscache_check_page_write(struct fscache_cookie *cookie,
 710                               struct page *page)
 711 {
 712         if (fscache_cookie_valid(cookie))
 713                 return __fscache_check_page_write(cookie, page);
 714         return false;
 715 }
 716
 717 /**
 718  * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
 719  * @cookie: The cookie representing the cache object
 720  * @page: The netfs page that is being cached.
 721  *
 722  * Ask the cache to wake us up when a page is no longer being written to the
 723  * cache.
 724  *
 725  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 726  * description.
 727  */
 728 static inline
 729 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
 730                                 struct page *page)
 731 {
 732         if (fscache_cookie_valid(cookie))
 733                 __fscache_wait_on_page_write(cookie, page);
 734 }
 735
 736 /**
 737  * fscache_maybe_release_page - Consider releasing a page, cancelling a store
 738  * @cookie: The cookie representing the cache object
 739  * @page: The netfs page that is being cached.
 740  * @gfp: The gfp flags passed to releasepage()
 741  *
 742  * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
 743  * releasepage() call.  A storage request on the page may cancelled if it is
 744  * not currently being processed.
 745  *
 746  * The function returns true if the page no longer has a storage request on it,
 747  * and false if a storage request is left in place.  If true is returned, the
 748  * page will have been passed to fscache_uncache_page().  If false is returned
 749  * the page cannot be freed yet.
 750  */
 751 static inline
 752 bool fscache_maybe_release_page(struct fscache_cookie *cookie,
 753                                 struct page *page,
 754                                 gfp_t gfp)
 755 {
 756         if (fscache_cookie_valid(cookie) && PageFsCache(page))
 757                 return __fscache_maybe_release_page(cookie, page, gfp);
 758         return true;
 759 }
 760
 761 /**
 762  * fscache_uncache_all_inode_pages - Uncache all an inode's pages
 763  * @cookie: The cookie representing the inode's cache object.
 764  * @inode: The inode to uncache pages from.
 765  *
 766  * Uncache all the pages in an inode that are marked PG_fscache, assuming them
 767  * to be associated with the given cookie.
 768  *
 769  * This function may sleep.  It will wait for pages that are being written out
 770  * and will wait whilst the PG_fscache mark is removed by the cache.
 771  */
 772 static inline
 773 void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 774                                      struct inode *inode)
 775 {
 776         if (fscache_cookie_valid(cookie))
 777                 __fscache_uncache_all_inode_pages(cookie, inode);
 778 }
 779
 780 /**
 781  * fscache_disable_cookie - Disable a cookie
 782  * @cookie: The cookie representing the cache object
 783  * @invalidate: Invalidate the backing object
 784  *
 785  * Disable a cookie from accepting further alloc, read, write, invalidate,
 786  * update or acquire operations.  Outstanding operations can still be waited
 787  * upon and pages can still be uncached and the cookie relinquished.
 788  *
 789  * This will not return until all outstanding operations have completed.
 790  *
 791  * If @invalidate is set, then the backing object will be invalidated and
 792  * detached, otherwise it will just be detached.
 793  */
 794 static inline
 795 void fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate)
 796 {
 797         if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
 798                 __fscache_disable_cookie(cookie, invalidate);
 799 }
 800
 801 /**
 802  * fscache_enable_cookie - Reenable a cookie
 803  * @cookie: The cookie representing the cache object
 804  * @can_enable: A function to permit enablement once lock is held
 805  * @data: Data for can_enable()
 806  *
 807  * Reenable a previously disabled cookie, allowing it to accept further alloc,
 808  * read, write, invalidate, update or acquire operations.  An attempt will be
 809  * made to immediately reattach the cookie to a backing object.
 810  *
 811  * The can_enable() function is called (if not NULL) once the enablement lock
 812  * is held to rule on whether enablement is still permitted to go ahead.
 813  */
 814 static inline
 815 void fscache_enable_cookie(struct fscache_cookie *cookie,
 816                            bool (*can_enable)(void *data),
 817                            void *data)
 818 {
 819         if (fscache_cookie_valid(cookie) && !fscache_cookie_enabled(cookie))
 820                 __fscache_enable_cookie(cookie, can_enable, data);
 821 }
 822
 823 #endif /* _LINUX_FSCACHE_H */