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 48struct pagevec; 49struct fscache_cache_tag; 50struct fscache_cookie; 51struct fscache_netfs; 52 53typedef void (*fscache_rw_complete_t)(struct page *page, 54 void *context, 55 int error); 56 57/* result of index entry consultation */ 58enum 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 */ 67struct 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 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 */ 162struct 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 */ 176extern int __fscache_register_netfs(struct fscache_netfs *); 177extern void __fscache_unregister_netfs(struct fscache_netfs *); 178extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *); 179extern void __fscache_release_cache_tag(struct fscache_cache_tag *); 180 181extern struct fscache_cookie *__fscache_acquire_cookie( 182 struct fscache_cookie *, 183 const struct fscache_cookie_def *, 184 void *); 185extern void __fscache_relinquish_cookie(struct fscache_cookie *, int); 186extern void __fscache_update_cookie(struct fscache_cookie *); 187extern int __fscache_attr_changed(struct fscache_cookie *); 188extern int __fscache_read_or_alloc_page(struct fscache_cookie *, 189 struct page *, 190 fscache_rw_complete_t, 191 void *, 192 gfp_t); 193extern 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); 200extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t); 201extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t); 202extern void __fscache_uncache_page(struct fscache_cookie *, struct page *); 203extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *); 204extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *); 205extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *, 206 gfp_t); 207 208/** 209 * fscache_register_netfs - Register a filesystem as desiring caching services 210 * @netfs: The description of the filesystem 211 * 212 * Register a filesystem as desiring caching services if they're available. 213 * 214 * See Documentation/filesystems/caching/netfs-api.txt for a complete 215 * description. 216 */ 217static inline 218int fscache_register_netfs(struct fscache_netfs *netfs) 219{ 220 if (fscache_available()) 221 return __fscache_register_netfs(netfs); 222 else 223 return 0; 224} 225 226/** 227 * fscache_unregister_netfs - Indicate that a filesystem no longer desires 228 * caching services 229 * @netfs: The description of the filesystem 230 * 231 * Indicate that a filesystem no longer desires caching services for the 232 * moment. 233 * 234 * See Documentation/filesystems/caching/netfs-api.txt for a complete 235 * description. 236 */ 237static inline 238void fscache_unregister_netfs(struct fscache_netfs *netfs) 239{ 240 if (fscache_available()) 241 __fscache_unregister_netfs(netfs); 242} 243 244/** 245 * fscache_lookup_cache_tag - Look up a cache tag 246 * @name: The name of the tag to search for 247 * 248 * Acquire a specific cache referral tag that can be used to select a specific 249 * cache in which to cache an index. 250 * 251 * See Documentation/filesystems/caching/netfs-api.txt for a complete 252 * description. 253 */ 254static inline 255struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name) 256{ 257 if (fscache_available()) 258 return __fscache_lookup_cache_tag(name); 259 else 260 return NULL; 261} 262 263/** 264 * fscache_release_cache_tag - Release a cache tag 265 * @tag: The tag to release 266 * 267 * Release a reference to a cache referral tag previously looked up. 268 * 269 * See Documentation/filesystems/caching/netfs-api.txt for a complete 270 * description. 271 */ 272static inline 273void fscache_release_cache_tag(struct fscache_cache_tag *tag) 274{ 275 if (fscache_available()) 276 __fscache_release_cache_tag(tag); 277} 278 279/** 280 * fscache_acquire_cookie - Acquire a cookie to represent a cache object 281 * @parent: The cookie that's to be the parent of this one 282 * @def: A description of the cache object, including callback operations 283 * @netfs_data: An arbitrary piece of data to be kept in the cookie to 284 * represent the cache object to the netfs 285 * 286 * This function is used to inform FS-Cache about part of an index hierarchy 287 * that can be used to locate files. This is done by requesting a cookie for 288 * each index in the path to the file. 289 * 290 * See Documentation/filesystems/caching/netfs-api.txt for a complete 291 * description. 292 */ 293static inline 294struct fscache_cookie *fscache_acquire_cookie( 295 struct fscache_cookie *parent, 296 const struct fscache_cookie_def *def, 297 void *netfs_data) 298{ 299 if (fscache_cookie_valid(parent)) 300 return __fscache_acquire_cookie(parent, def, netfs_data); 301 else 302 return NULL; 303} 304 305/** 306 * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding 307 * it 308 * @cookie: The cookie being returned 309 * @retire: True if the cache object the cookie represents is to be discarded 310 * 311 * This function returns a cookie to the cache, forcibly discarding the 312 * associated cache object if retire is set to true. 313 * 314 * See Documentation/filesystems/caching/netfs-api.txt for a complete 315 * description. 316 */ 317static inline 318void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire) 319{ 320 if (fscache_cookie_valid(cookie)) 321 __fscache_relinquish_cookie(cookie, retire); 322} 323 324/** 325 * fscache_update_cookie - Request that a cache object be updated 326 * @cookie: The cookie representing the cache object 327 * 328 * Request an update of the index data for the cache object associated with the 329 * cookie. 330 * 331 * See Documentation/filesystems/caching/netfs-api.txt for a complete 332 * description. 333 */ 334static inline 335void fscache_update_cookie(struct fscache_cookie *cookie) 336{ 337 if (fscache_cookie_valid(cookie)) 338 __fscache_update_cookie(cookie); 339} 340 341/** 342 * fscache_pin_cookie - Pin a data-storage cache object in its cache 343 * @cookie: The cookie representing the cache object 344 * 345 * Permit data-storage cache objects to be pinned in the cache. 346 * 347 * See Documentation/filesystems/caching/netfs-api.txt for a complete 348 * description. 349 */ 350static inline 351int fscache_pin_cookie(struct fscache_cookie *cookie) 352{ 353 return -ENOBUFS; 354} 355 356/** 357 * fscache_pin_cookie - Unpin a data-storage cache object in its cache 358 * @cookie: The cookie representing the cache object 359 * 360 * Permit data-storage cache objects to be unpinned from the cache. 361 * 362 * See Documentation/filesystems/caching/netfs-api.txt for a complete 363 * description. 364 */ 365static inline 366void fscache_unpin_cookie(struct fscache_cookie *cookie) 367{ 368} 369 370/** 371 * fscache_attr_changed - Notify cache that an object's attributes changed 372 * @cookie: The cookie representing the cache object 373 * 374 * Send a notification to the cache indicating that an object's attributes have 375 * changed. This includes the data size. These attributes will be obtained 376 * through the get_attr() cookie definition op. 377 * 378 * See Documentation/filesystems/caching/netfs-api.txt for a complete 379 * description. 380 */ 381static inline 382int fscache_attr_changed(struct fscache_cookie *cookie) 383{ 384 if (fscache_cookie_valid(cookie)) 385 return __fscache_attr_changed(cookie); 386 else 387 return -ENOBUFS; 388} 389 390/** 391 * fscache_reserve_space - Reserve data space for a cached object 392 * @cookie: The cookie representing the cache object 393 * @i_size: The amount of space to be reserved 394 * 395 * Reserve an amount of space in the cache for the cache object attached to a 396 * cookie so that a write to that object within the space can always be 397 * honoured. 398 * 399 * See Documentation/filesystems/caching/netfs-api.txt for a complete 400 * description. 401 */ 402static inline 403int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size) 404{ 405 return -ENOBUFS; 406} 407 408/** 409 * fscache_read_or_alloc_page - Read a page from the cache or allocate a block 410 * in which to store it 411 * @cookie: The cookie representing the cache object 412 * @page: The netfs page to fill if possible 413 * @end_io_func: The callback to invoke when and if the page is filled 414 * @context: An arbitrary piece of data to pass on to end_io_func() 415 * @gfp: The conditions under which memory allocation should be made 416 * 417 * Read a page from the cache, or if that's not possible make a potential 418 * one-block reservation in the cache into which the page may be stored once 419 * fetched from the server. 420 * 421 * If the page is not backed by the cache object, or if it there's some reason 422 * it can't be, -ENOBUFS will be returned and nothing more will be done for 423 * that page. 424 * 425 * Else, if that page is backed by the cache, a read will be initiated directly 426 * to the netfs's page and 0 will be returned by this function. The 427 * end_io_func() callback will be invoked when the operation terminates on a 428 * completion or failure. Note that the callback may be invoked before the 429 * return. 430 * 431 * Else, if the page is unbacked, -ENODATA is returned and a block may have 432 * been allocated in the cache. 433 * 434 * See Documentation/filesystems/caching/netfs-api.txt for a complete 435 * description. 436 */ 437static inline 438int fscache_read_or_alloc_page(struct fscache_cookie *cookie, 439 struct page *page, 440 fscache_rw_complete_t end_io_func, 441 void *context, 442 gfp_t gfp) 443{ 444 if (fscache_cookie_valid(cookie)) 445 return __fscache_read_or_alloc_page(cookie, page, end_io_func, 446 context, gfp); 447 else 448 return -ENOBUFS; 449} 450 451/** 452 * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate 453 * blocks in which to store them 454 * @cookie: The cookie representing the cache object 455 * @mapping: The netfs inode mapping to which the pages will be attached 456 * @pages: A list of potential netfs pages to be filled 457 * @nr_pages: Number of pages to be read and/or allocated 458 * @end_io_func: The callback to invoke when and if each page is filled 459 * @context: An arbitrary piece of data to pass on to end_io_func() 460 * @gfp: The conditions under which memory allocation should be made 461 * 462 * Read a set of pages from the cache, or if that's not possible, attempt to 463 * make a potential one-block reservation for each page in the cache into which 464 * that page may be stored once fetched from the server. 465 * 466 * If some pages are not backed by the cache object, or if it there's some 467 * reason they can't be, -ENOBUFS will be returned and nothing more will be 468 * done for that pages. 469 * 470 * Else, if some of the pages are backed by the cache, a read will be initiated 471 * directly to the netfs's page and 0 will be returned by this function. The 472 * end_io_func() callback will be invoked when the operation terminates on a 473 * completion or failure. Note that the callback may be invoked before the 474 * return. 475 * 476 * Else, if a page is unbacked, -ENODATA is returned and a block may have 477 * been allocated in the cache. 478 * 479 * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in 480 * regard to different pages, the return values are prioritised in that order. 481 * Any pages submitted for reading are removed from the pages list. 482 * 483 * See Documentation/filesystems/caching/netfs-api.txt for a complete 484 * description. 485 */ 486static inline 487int fscache_read_or_alloc_pages(struct fscache_cookie *cookie, 488 struct address_space *mapping, 489 struct list_head *pages, 490 unsigned *nr_pages, 491 fscache_rw_complete_t end_io_func, 492 void *context, 493 gfp_t gfp) 494{ 495 if (fscache_cookie_valid(cookie)) 496 return __fscache_read_or_alloc_pages(cookie, mapping, pages, 497 nr_pages, end_io_func, 498 context, gfp); 499 else 500 return -ENOBUFS; 501} 502 503/** 504 * fscache_alloc_page - Allocate a block in which to store a page 505 * @cookie: The cookie representing the cache object 506 * @page: The netfs page to allocate a page for 507 * @gfp: The conditions under which memory allocation should be made 508 * 509 * Request Allocation a block in the cache in which to store a netfs page 510 * without retrieving any contents from the cache. 511 * 512 * If the page is not backed by a file then -ENOBUFS will be returned and 513 * nothing more will be done, and no reservation will be made. 514 * 515 * Else, a block will be allocated if one wasn't already, and 0 will be 516 * returned 517 * 518 * See Documentation/filesystems/caching/netfs-api.txt for a complete 519 * description. 520 */ 521static inline 522int fscache_alloc_page(struct fscache_cookie *cookie, 523 struct page *page, 524 gfp_t gfp) 525{ 526 if (fscache_cookie_valid(cookie)) 527 return __fscache_alloc_page(cookie, page, gfp); 528 else 529 return -ENOBUFS; 530} 531 532/** 533 * fscache_write_page - Request storage of a page in the cache 534 * @cookie: The cookie representing the cache object 535 * @page: The netfs page to store 536 * @gfp: The conditions under which memory allocation should be made 537 * 538 * Request the contents of the netfs page be written into the cache. This 539 * request may be ignored if no cache block is currently allocated, in which 540 * case it will return -ENOBUFS. 541 * 542 * If a cache block was already allocated, a write will be initiated and 0 will 543 * be returned. The PG_fscache_write page bit is set immediately and will then 544 * be cleared at the completion of the write to indicate the success or failure 545 * of the operation. Note that the completion may happen before the return. 546 * 547 * See Documentation/filesystems/caching/netfs-api.txt for a complete 548 * description. 549 */ 550static inline 551int fscache_write_page(struct fscache_cookie *cookie, 552 struct page *page, 553 gfp_t gfp) 554{ 555 if (fscache_cookie_valid(cookie)) 556 return __fscache_write_page(cookie, page, gfp); 557 else 558 return -ENOBUFS; 559} 560 561/** 562 * fscache_uncache_page - Indicate that caching is no longer required on a page 563 * @cookie: The cookie representing the cache object 564 * @page: The netfs page that was being cached. 565 * 566 * Tell the cache that we no longer want a page to be cached and that it should 567 * remove any knowledge of the netfs page it may have. 568 * 569 * Note that this cannot cancel any outstanding I/O operations between this 570 * page and the cache. 571 * 572 * See Documentation/filesystems/caching/netfs-api.txt for a complete 573 * description. 574 */ 575static inline 576void fscache_uncache_page(struct fscache_cookie *cookie, 577 struct page *page) 578{ 579 if (fscache_cookie_valid(cookie)) 580 __fscache_uncache_page(cookie, page); 581} 582 583/** 584 * fscache_check_page_write - Ask if a page is being writing to the cache 585 * @cookie: The cookie representing the cache object 586 * @page: The netfs page that is being cached. 587 * 588 * Ask the cache if a page is being written to the cache. 589 * 590 * See Documentation/filesystems/caching/netfs-api.txt for a complete 591 * description. 592 */ 593static inline 594bool fscache_check_page_write(struct fscache_cookie *cookie, 595 struct page *page) 596{ 597 if (fscache_cookie_valid(cookie)) 598 return __fscache_check_page_write(cookie, page); 599 return false; 600} 601 602/** 603 * fscache_wait_on_page_write - Wait for a page to complete writing to the cache 604 * @cookie: The cookie representing the cache object 605 * @page: The netfs page that is being cached. 606 * 607 * Ask the cache to wake us up when a page is no longer being written to the 608 * cache. 609 * 610 * See Documentation/filesystems/caching/netfs-api.txt for a complete 611 * description. 612 */ 613static inline 614void fscache_wait_on_page_write(struct fscache_cookie *cookie, 615 struct page *page) 616{ 617 if (fscache_cookie_valid(cookie)) 618 __fscache_wait_on_page_write(cookie, page); 619} 620 621/** 622 * fscache_maybe_release_page - Consider releasing a page, cancelling a store 623 * @cookie: The cookie representing the cache object 624 * @page: The netfs page that is being cached. 625 * @gfp: The gfp flags passed to releasepage() 626 * 627 * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's 628 * releasepage() call. A storage request on the page may cancelled if it is 629 * not currently being processed. 630 * 631 * The function returns true if the page no longer has a storage request on it, 632 * and false if a storage request is left in place. If true is returned, the 633 * page will have been passed to fscache_uncache_page(). If false is returned 634 * the page cannot be freed yet. 635 */ 636static inline 637bool fscache_maybe_release_page(struct fscache_cookie *cookie, 638 struct page *page, 639 gfp_t gfp) 640{ 641 if (fscache_cookie_valid(cookie) && PageFsCache(page)) 642 return __fscache_maybe_release_page(cookie, page, gfp); 643 return false; 644} 645 646#endif /* _LINUX_FSCACHE_H */ 647