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 amount 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 auxilliary data from netfs data
 106          * - this function can be absent if the index carries no state data
 107          * - should store the auxilliary data in the buffer
 108          * - should return the amount of amount stored
 109          * - not permitted to return an error
 110          * - the netfs data from the cookie being used as the source is
 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 auxilliary 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 pages that now have cache metadata retained
 139          * - this function should mark the specified pages as now being cached
 140          * - the pages will have been marked with PG_fscache before this is
 141          *   called, so this is optional
 142          */
 143         void (*mark_pages_cached)(void *cookie_netfs_data,
 144                                   struct address_space *mapping,
 145                                   struct pagevec *cached_pvec);
 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 int __fscache_read_or_alloc_page(struct fscache_cookie *,
 189                                         struct page *,
 190                                         fscache_rw_complete_t,
 191                                         void *,
 192                                         gfp_t);
 193 extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
 194                                          struct address_space *,
 195                                          struct list_head *,
 196                                          unsigned *,
 197                                          fscache_rw_complete_t,
 198                                          void *,
 199                                          gfp_t);
 200 extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
 201 extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
 202 extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
 203 extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
 204 extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
 205
 206 /**
 207  * fscache_register_netfs - Register a filesystem as desiring caching services
 208  * @netfs: The description of the filesystem
 209  *
 210  * Register a filesystem as desiring caching services if they're available.
 211  *
 212  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 213  * description.
 214  */
 215 static inline
 216 int fscache_register_netfs(struct fscache_netfs *netfs)
 217 {
 218         if (fscache_available())
 219                 return __fscache_register_netfs(netfs);
 220         else
 221                 return 0;
 222 }
 223
 224 /**
 225  * fscache_unregister_netfs - Indicate that a filesystem no longer desires
 226  * caching services
 227  * @netfs: The description of the filesystem
 228  *
 229  * Indicate that a filesystem no longer desires caching services for the
 230  * moment.
 231  *
 232  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 233  * description.
 234  */
 235 static inline
 236 void fscache_unregister_netfs(struct fscache_netfs *netfs)
 237 {
 238         if (fscache_available())
 239                 __fscache_unregister_netfs(netfs);
 240 }
 241
 242 /**
 243  * fscache_lookup_cache_tag - Look up a cache tag
 244  * @name: The name of the tag to search for
 245  *
 246  * Acquire a specific cache referral tag that can be used to select a specific
 247  * cache in which to cache an index.
 248  *
 249  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 250  * description.
 251  */
 252 static inline
 253 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
 254 {
 255         if (fscache_available())
 256                 return __fscache_lookup_cache_tag(name);
 257         else
 258                 return NULL;
 259 }
 260
 261 /**
 262  * fscache_release_cache_tag - Release a cache tag
 263  * @tag: The tag to release
 264  *
 265  * Release a reference to a cache referral tag previously looked up.
 266  *
 267  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 268  * description.
 269  */
 270 static inline
 271 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
 272 {
 273         if (fscache_available())
 274                 __fscache_release_cache_tag(tag);
 275 }
 276
 277 /**
 278  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
 279  * @parent: The cookie that's to be the parent of this one
 280  * @def: A description of the cache object, including callback operations
 281  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
 282  * represent the cache object to the netfs
 283  *
 284  * This function is used to inform FS-Cache about part of an index hierarchy
 285  * that can be used to locate files.  This is done by requesting a cookie for
 286  * each index in the path to the file.
 287  *
 288  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 289  * description.
 290  */
 291 static inline
 292 struct fscache_cookie *fscache_acquire_cookie(
 293         struct fscache_cookie *parent,
 294         const struct fscache_cookie_def *def,
 295         void *netfs_data)
 296 {
 297         if (fscache_cookie_valid(parent))
 298                 return __fscache_acquire_cookie(parent, def, netfs_data);
 299         else
 300                 return NULL;
 301 }
 302
 303 /**
 304  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
 305  * it
 306  * @cookie: The cookie being returned
 307  * @retire: True if the cache object the cookie represents is to be discarded
 308  *
 309  * This function returns a cookie to the cache, forcibly discarding the
 310  * associated cache object if retire is set to true.
 311  *
 312  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 313  * description.
 314  */
 315 static inline
 316 void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 317 {
 318         if (fscache_cookie_valid(cookie))
 319                 __fscache_relinquish_cookie(cookie, retire);
 320 }
 321
 322 /**
 323  * fscache_update_cookie - Request that a cache object be updated
 324  * @cookie: The cookie representing the cache object
 325  *
 326  * Request an update of the index data for the cache object associated with the
 327  * cookie.
 328  *
 329  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 330  * description.
 331  */
 332 static inline
 333 void fscache_update_cookie(struct fscache_cookie *cookie)
 334 {
 335         if (fscache_cookie_valid(cookie))
 336                 __fscache_update_cookie(cookie);
 337 }
 338
 339 /**
 340  * fscache_pin_cookie - Pin a data-storage cache object in its cache
 341  * @cookie: The cookie representing the cache object
 342  *
 343  * Permit data-storage cache objects to be pinned in the cache.
 344  *
 345  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 346  * description.
 347  */
 348 static inline
 349 int fscache_pin_cookie(struct fscache_cookie *cookie)
 350 {
 351         return -ENOBUFS;
 352 }
 353
 354 /**
 355  * fscache_pin_cookie - Unpin a data-storage cache object in its cache
 356  * @cookie: The cookie representing the cache object
 357  *
 358  * Permit data-storage cache objects to be unpinned from the cache.
 359  *
 360  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 361  * description.
 362  */
 363 static inline
 364 void fscache_unpin_cookie(struct fscache_cookie *cookie)
 365 {
 366 }
 367
 368 /**
 369  * fscache_attr_changed - Notify cache that an object's attributes changed
 370  * @cookie: The cookie representing the cache object
 371  *
 372  * Send a notification to the cache indicating that an object's attributes have
 373  * changed.  This includes the data size.  These attributes will be obtained
 374  * through the get_attr() cookie definition op.
 375  *
 376  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 377  * description.
 378  */
 379 static inline
 380 int fscache_attr_changed(struct fscache_cookie *cookie)
 381 {
 382         if (fscache_cookie_valid(cookie))
 383                 return __fscache_attr_changed(cookie);
 384         else
 385                 return -ENOBUFS;
 386 }
 387
 388 /**
 389  * fscache_reserve_space - Reserve data space for a cached object
 390  * @cookie: The cookie representing the cache object
 391  * @i_size: The amount of space to be reserved
 392  *
 393  * Reserve an amount of space in the cache for the cache object attached to a
 394  * cookie so that a write to that object within the space can always be
 395  * honoured.
 396  *
 397  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 398  * description.
 399  */
 400 static inline
 401 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 402 {
 403         return -ENOBUFS;
 404 }
 405
 406 /**
 407  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
 408  * in which to store it
 409  * @cookie: The cookie representing the cache object
 410  * @page: The netfs page to fill if possible
 411  * @end_io_func: The callback to invoke when and if the page is filled
 412  * @context: An arbitrary piece of data to pass on to end_io_func()
 413  * @gfp: The conditions under which memory allocation should be made
 414  *
 415  * Read a page from the cache, or if that's not possible make a potential
 416  * one-block reservation in the cache into which the page may be stored once
 417  * fetched from the server.
 418  *
 419  * If the page is not backed by the cache object, or if it there's some reason
 420  * it can't be, -ENOBUFS will be returned and nothing more will be done for
 421  * that page.
 422  *
 423  * Else, if that page is backed by the cache, a read will be initiated directly
 424  * to the netfs's page and 0 will be returned by this function.  The
 425  * end_io_func() callback will be invoked when the operation terminates on a
 426  * completion or failure.  Note that the callback may be invoked before the
 427  * return.
 428  *
 429  * Else, if the page is unbacked, -ENODATA is returned and a block may have
 430  * been allocated in the cache.
 431  *
 432  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 433  * description.
 434  */
 435 static inline
 436 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 437                                struct page *page,
 438                                fscache_rw_complete_t end_io_func,
 439                                void *context,
 440                                gfp_t gfp)
 441 {
 442         if (fscache_cookie_valid(cookie))
 443                 return __fscache_read_or_alloc_page(cookie, page, end_io_func,
 444                                                     context, gfp);
 445         else
 446                 return -ENOBUFS;
 447 }
 448
 449 /**
 450  * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
 451  * blocks in which to store them
 452  * @cookie: The cookie representing the cache object
 453  * @mapping: The netfs inode mapping to which the pages will be attached
 454  * @pages: A list of potential netfs pages to be filled
 455  * @end_io_func: The callback to invoke when and if each page is filled
 456  * @context: An arbitrary piece of data to pass on to end_io_func()
 457  * @gfp: The conditions under which memory allocation should be made
 458  *
 459  * Read a set of pages from the cache, or if that's not possible, attempt to
 460  * make a potential one-block reservation for each page in the cache into which
 461  * that page may be stored once fetched from the server.
 462  *
 463  * If some pages are not backed by the cache object, or if it there's some
 464  * reason they can't be, -ENOBUFS will be returned and nothing more will be
 465  * done for that pages.
 466  *
 467  * Else, if some of the pages are backed by the cache, a read will be initiated
 468  * directly to the netfs's page and 0 will be returned by this function.  The
 469  * end_io_func() callback will be invoked when the operation terminates on a
 470  * completion or failure.  Note that the callback may be invoked before the
 471  * return.
 472  *
 473  * Else, if a page is unbacked, -ENODATA is returned and a block may have
 474  * been allocated in the cache.
 475  *
 476  * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
 477  * regard to different pages, the return values are prioritised in that order.
 478  * Any pages submitted for reading are removed from the pages list.
 479  *
 480  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 481  * description.
 482  */
 483 static inline
 484 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 485                                 struct address_space *mapping,
 486                                 struct list_head *pages,
 487                                 unsigned *nr_pages,
 488                                 fscache_rw_complete_t end_io_func,
 489                                 void *context,
 490                                 gfp_t gfp)
 491 {
 492         if (fscache_cookie_valid(cookie))
 493                 return __fscache_read_or_alloc_pages(cookie, mapping, pages,
 494                                                      nr_pages, end_io_func,
 495                                                      context, gfp);
 496         else
 497                 return -ENOBUFS;
 498 }
 499
 500 /**
 501  * fscache_alloc_page - Allocate a block in which to store a page
 502  * @cookie: The cookie representing the cache object
 503  * @page: The netfs page to allocate a page for
 504  * @gfp: The conditions under which memory allocation should be made
 505  *
 506  * Request Allocation a block in the cache in which to store a netfs page
 507  * without retrieving any contents from the cache.
 508  *
 509  * If the page is not backed by a file then -ENOBUFS will be returned and
 510  * nothing more will be done, and no reservation will be made.
 511  *
 512  * Else, a block will be allocated if one wasn't already, and 0 will be
 513  * returned
 514  *
 515  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 516  * description.
 517  */
 518 static inline
 519 int fscache_alloc_page(struct fscache_cookie *cookie,
 520                        struct page *page,
 521                        gfp_t gfp)
 522 {
 523         if (fscache_cookie_valid(cookie))
 524                 return __fscache_alloc_page(cookie, page, gfp);
 525         else
 526                 return -ENOBUFS;
 527 }
 528
 529 /**
 530  * fscache_write_page - Request storage of a page in the cache
 531  * @cookie: The cookie representing the cache object
 532  * @page: The netfs page to store
 533  * @gfp: The conditions under which memory allocation should be made
 534  *
 535  * Request the contents of the netfs page be written into the cache.  This
 536  * request may be ignored if no cache block is currently allocated, in which
 537  * case it will return -ENOBUFS.
 538  *
 539  * If a cache block was already allocated, a write will be initiated and 0 will
 540  * be returned.  The PG_fscache_write page bit is set immediately and will then
 541  * be cleared at the completion of the write to indicate the success or failure
 542  * of the operation.  Note that the completion may happen before the return.
 543  *
 544  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 545  * description.
 546  */
 547 static inline
 548 int fscache_write_page(struct fscache_cookie *cookie,
 549                        struct page *page,
 550                        gfp_t gfp)
 551 {
 552         if (fscache_cookie_valid(cookie))
 553                 return __fscache_write_page(cookie, page, gfp);
 554         else
 555                 return -ENOBUFS;
 556 }
 557
 558 /**
 559  * fscache_uncache_page - Indicate that caching is no longer required on a page
 560  * @cookie: The cookie representing the cache object
 561  * @page: The netfs page that was being cached.
 562  *
 563  * Tell the cache that we no longer want a page to be cached and that it should
 564  * remove any knowledge of the netfs page it may have.
 565  *
 566  * Note that this cannot cancel any outstanding I/O operations between this
 567  * page and the cache.
 568  *
 569  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 570  * description.
 571  */
 572 static inline
 573 void fscache_uncache_page(struct fscache_cookie *cookie,
 574                           struct page *page)
 575 {
 576         if (fscache_cookie_valid(cookie))
 577                 __fscache_uncache_page(cookie, page);
 578 }
 579
 580 /**
 581  * fscache_check_page_write - Ask if a page is being writing to the cache
 582  * @cookie: The cookie representing the cache object
 583  * @page: The netfs page that is being cached.
 584  *
 585  * Ask the cache if a page is being written to the cache.
 586  *
 587  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 588  * description.
 589  */
 590 static inline
 591 bool fscache_check_page_write(struct fscache_cookie *cookie,
 592                               struct page *page)
 593 {
 594         if (fscache_cookie_valid(cookie))
 595                 return __fscache_check_page_write(cookie, page);
 596         return false;
 597 }
 598
 599 /**
 600  * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
 601  * @cookie: The cookie representing the cache object
 602  * @page: The netfs page that is being cached.
 603  *
 604  * Ask the cache to wake us up when a page is no longer being written to the
 605  * cache.
 606  *
 607  * See Documentation/filesystems/caching/netfs-api.txt for a complete
 608  * description.
 609  */
 610 static inline
 611 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
 612                                 struct page *page)
 613 {
 614         if (fscache_cookie_valid(cookie))
 615                 __fscache_wait_on_page_write(cookie, page);
 616 }
 617
 618 #endif /* _LINUX_FSCACHE_H */