1 /* General filesystem caching backing cache interface 2 * 3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells ([email protected]) 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/backend-api.txt 14 * 15 * for a description of the cache backend interface declared here. 16 */ 17 18 #ifndef _LINUX_FSCACHE_CACHE_H 19 #define _LINUX_FSCACHE_CACHE_H 20 21 #include <linux/fscache.h> 22 #include <linux/sched.h> 23 #include <linux/workqueue.h> 24 25 #define NR_MAXCACHES BITS_PER_LONG 26 27 struct fscache_cache; 28 struct fscache_cache_ops; 29 struct fscache_object; 30 struct fscache_operation; 31 32 /* 33 * cache tag definition 34 */ 35 struct fscache_cache_tag { 36 struct list_head link; 37 struct fscache_cache *cache; /* cache referred to by this tag */ 38 unsigned long flags; 39 #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */ 40 atomic_t usage; 41 char name[0]; /* tag name */ 42 }; 43 44 /* 45 * cache definition 46 */ 47 struct fscache_cache { 48 const struct fscache_cache_ops *ops; 49 struct fscache_cache_tag *tag; /* tag representing this cache */ 50 struct kobject *kobj; /* system representation of this cache */ 51 struct list_head link; /* link in list of caches */ 52 size_t max_index_size; /* maximum size of index data */ 53 char identifier[36]; /* cache label */ 54 55 /* node management */ 56 struct work_struct op_gc; /* operation garbage collector */ 57 struct list_head object_list; /* list of data/index objects */ 58 struct list_head op_gc_list; /* list of ops to be deleted */ 59 spinlock_t object_list_lock; 60 spinlock_t op_gc_list_lock; 61 atomic_t object_count; /* no. of live objects in this cache */ 62 struct fscache_object *fsdef; /* object for the fsdef index */ 63 unsigned long flags; 64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66 }; 67 68 extern wait_queue_head_t fscache_cache_cleared_wq; 69 70 /* 71 * operation to be applied to a cache object 72 * - retrieval initiation operations are done in the context of the process 73 * that issued them, and not in an async thread pool 74 */ 75 typedef void (*fscache_operation_release_t)(struct fscache_operation *op); 76 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op); 77 78 enum fscache_operation_state { 79 FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */ 80 FSCACHE_OP_ST_INITIALISED, /* Op is initialised */ 81 FSCACHE_OP_ST_PENDING, /* Op is blocked from running */ 82 FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */ 83 FSCACHE_OP_ST_COMPLETE, /* Op is complete */ 84 FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */ 85 FSCACHE_OP_ST_DEAD /* Op is now dead */ 86 }; 87 88 struct fscache_operation { 89 struct work_struct work; /* record for async ops */ 90 struct list_head pend_link; /* link in object->pending_ops */ 91 struct fscache_object *object; /* object to be operated upon */ 92 93 unsigned long flags; 94 #define FSCACHE_OP_TYPE 0x000f /* operation type */ 95 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */ 96 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */ 97 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ 98 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ 99 #define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */ 100 #define FSCACHE_OP_KEEP_FLAGS 0x0070 /* flags to keep when repurposing an op */ 101 102 enum fscache_operation_state state; 103 atomic_t usage; 104 unsigned debug_id; /* debugging ID */ 105 106 /* operation processor callback 107 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform 108 * the op in a non-pool thread */ 109 fscache_operation_processor_t processor; 110 111 /* operation releaser */ 112 fscache_operation_release_t release; 113 }; 114 115 extern atomic_t fscache_op_debug_id; 116 extern void fscache_op_work_func(struct work_struct *work); 117 118 extern void fscache_enqueue_operation(struct fscache_operation *); 119 extern void fscache_op_complete(struct fscache_operation *, bool); 120 extern void fscache_put_operation(struct fscache_operation *); 121 122 /** 123 * fscache_operation_init - Do basic initialisation of an operation 124 * @op: The operation to initialise 125 * @release: The release function to assign 126 * 127 * Do basic initialisation of an operation. The caller must still set flags, 128 * object and processor if needed. 129 */ 130 static inline void fscache_operation_init(struct fscache_operation *op, 131 fscache_operation_processor_t processor, 132 fscache_operation_release_t release) 133 { 134 INIT_WORK(&op->work, fscache_op_work_func); 135 atomic_set(&op->usage, 1); 136 op->state = FSCACHE_OP_ST_INITIALISED; 137 op->debug_id = atomic_inc_return(&fscache_op_debug_id); 138 op->processor = processor; 139 op->release = release; 140 INIT_LIST_HEAD(&op->pend_link); 141 } 142 143 /* 144 * data read operation 145 */ 146 struct fscache_retrieval { 147 struct fscache_operation op; 148 struct address_space *mapping; /* netfs pages */ 149 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ 150 void *context; /* netfs read context (pinned) */ 151 struct list_head to_do; /* list of things to be done by the backend */ 152 unsigned long start_time; /* time at which retrieval started */ 153 unsigned n_pages; /* number of pages to be retrieved */ 154 }; 155 156 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, 157 struct page *page, 158 gfp_t gfp); 159 160 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, 161 struct list_head *pages, 162 unsigned *nr_pages, 163 gfp_t gfp); 164 165 /** 166 * fscache_get_retrieval - Get an extra reference on a retrieval operation 167 * @op: The retrieval operation to get a reference on 168 * 169 * Get an extra reference on a retrieval operation. 170 */ 171 static inline 172 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) 173 { 174 atomic_inc(&op->op.usage); 175 return op; 176 } 177 178 /** 179 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing 180 * @op: The retrieval operation affected 181 * 182 * Enqueue a retrieval operation for processing by the FS-Cache thread pool. 183 */ 184 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) 185 { 186 fscache_enqueue_operation(&op->op); 187 } 188 189 /** 190 * fscache_retrieval_complete - Record (partial) completion of a retrieval 191 * @op: The retrieval operation affected 192 * @n_pages: The number of pages to account for 193 */ 194 static inline void fscache_retrieval_complete(struct fscache_retrieval *op, 195 int n_pages) 196 { 197 op->n_pages -= n_pages; 198 if (op->n_pages <= 0) 199 fscache_op_complete(&op->op, true); 200 } 201 202 /** 203 * fscache_put_retrieval - Drop a reference to a retrieval operation 204 * @op: The retrieval operation affected 205 * @n_pages: The number of pages to account for 206 * 207 * Drop a reference to a retrieval operation. 208 */ 209 static inline void fscache_put_retrieval(struct fscache_retrieval *op) 210 { 211 fscache_put_operation(&op->op); 212 } 213 214 /* 215 * cached page storage work item 216 * - used to do three things: 217 * - batch writes to the cache 218 * - do cache writes asynchronously 219 * - defer writes until cache object lookup completion 220 */ 221 struct fscache_storage { 222 struct fscache_operation op; 223 pgoff_t store_limit; /* don't write more than this */ 224 }; 225 226 /* 227 * cache operations 228 */ 229 struct fscache_cache_ops { 230 /* name of cache provider */ 231 const char *name; 232 233 /* allocate an object record for a cookie */ 234 struct fscache_object *(*alloc_object)(struct fscache_cache *cache, 235 struct fscache_cookie *cookie); 236 237 /* look up the object for a cookie 238 * - return -ETIMEDOUT to be requeued 239 */ 240 int (*lookup_object)(struct fscache_object *object); 241 242 /* finished looking up */ 243 void (*lookup_complete)(struct fscache_object *object); 244 245 /* increment the usage count on this object (may fail if unmounting) */ 246 struct fscache_object *(*grab_object)(struct fscache_object *object); 247 248 /* pin an object in the cache */ 249 int (*pin_object)(struct fscache_object *object); 250 251 /* unpin an object in the cache */ 252 void (*unpin_object)(struct fscache_object *object); 253 254 /* store the updated auxiliary data on an object */ 255 void (*update_object)(struct fscache_object *object); 256 257 /* Invalidate an object */ 258 void (*invalidate_object)(struct fscache_operation *op); 259 260 /* discard the resources pinned by an object and effect retirement if 261 * necessary */ 262 void (*drop_object)(struct fscache_object *object); 263 264 /* dispose of a reference to an object */ 265 void (*put_object)(struct fscache_object *object); 266 267 /* sync a cache */ 268 void (*sync_cache)(struct fscache_cache *cache); 269 270 /* notification that the attributes of a non-index object (such as 271 * i_size) have changed */ 272 int (*attr_changed)(struct fscache_object *object); 273 274 /* reserve space for an object's data and associated metadata */ 275 int (*reserve_space)(struct fscache_object *object, loff_t i_size); 276 277 /* request a backing block for a page be read or allocated in the 278 * cache */ 279 fscache_page_retrieval_func_t read_or_alloc_page; 280 281 /* request backing blocks for a list of pages be read or allocated in 282 * the cache */ 283 fscache_pages_retrieval_func_t read_or_alloc_pages; 284 285 /* request a backing block for a page be allocated in the cache so that 286 * it can be written directly */ 287 fscache_page_retrieval_func_t allocate_page; 288 289 /* request backing blocks for pages be allocated in the cache so that 290 * they can be written directly */ 291 fscache_pages_retrieval_func_t allocate_pages; 292 293 /* write a page to its backing block in the cache */ 294 int (*write_page)(struct fscache_storage *op, struct page *page); 295 296 /* detach backing block from a page (optional) 297 * - must release the cookie lock before returning 298 * - may sleep 299 */ 300 void (*uncache_page)(struct fscache_object *object, 301 struct page *page); 302 303 /* dissociate a cache from all the pages it was backing */ 304 void (*dissociate_pages)(struct fscache_cache *cache); 305 }; 306 307 /* 308 * data file or index object cookie 309 * - a file will only appear in one cache 310 * - a request to cache a file may or may not be honoured, subject to 311 * constraints such as disk space 312 * - indices are created on disk just-in-time 313 */ 314 struct fscache_cookie { 315 atomic_t usage; /* number of users of this cookie */ 316 atomic_t n_children; /* number of children of this cookie */ 317 spinlock_t lock; 318 spinlock_t stores_lock; /* lock on page store tree */ 319 struct hlist_head backing_objects; /* object(s) backing this file/index */ 320 const struct fscache_cookie_def *def; /* definition */ 321 struct fscache_cookie *parent; /* parent of this entry */ 322 void *netfs_data; /* back pointer to netfs */ 323 struct radix_tree_root stores; /* pages to be stored on this cookie */ 324 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */ 325 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */ 326 327 unsigned long flags; 328 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */ 329 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */ 330 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */ 331 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */ 332 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */ 333 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */ 334 #define FSCACHE_COOKIE_WAITING_ON_READS 6 /* T if cookie is waiting on reads */ 335 #define FSCACHE_COOKIE_INVALIDATING 7 /* T if cookie is being invalidated */ 336 }; 337 338 extern struct fscache_cookie fscache_fsdef_index; 339 340 /* 341 * Event list for fscache_object::{event_mask,events} 342 */ 343 enum { 344 FSCACHE_OBJECT_EV_REQUEUE, /* T if object should be requeued */ 345 FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */ 346 FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */ 347 FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */ 348 FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */ 349 FSCACHE_OBJECT_EV_RELEASE, /* T if netfs requested object release */ 350 FSCACHE_OBJECT_EV_RETIRE, /* T if netfs requested object retirement */ 351 FSCACHE_OBJECT_EV_WITHDRAW, /* T if cache requested object withdrawal */ 352 NR_FSCACHE_OBJECT_EVENTS 353 }; 354 355 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1) 356 357 /* 358 * on-disk cache file or index handle 359 */ 360 struct fscache_object { 361 enum fscache_object_state { 362 FSCACHE_OBJECT_INIT, /* object in initial unbound state */ 363 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */ 364 FSCACHE_OBJECT_CREATING, /* creating object */ 365 366 /* active states */ 367 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */ 368 FSCACHE_OBJECT_ACTIVE, /* object is usable */ 369 FSCACHE_OBJECT_INVALIDATING, /* object is invalidating */ 370 FSCACHE_OBJECT_UPDATING, /* object is updating */ 371 372 /* terminal states */ 373 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */ 374 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */ 375 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */ 376 FSCACHE_OBJECT_RELEASING, /* releasing object */ 377 FSCACHE_OBJECT_RECYCLING, /* retiring object */ 378 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */ 379 FSCACHE_OBJECT_DEAD, /* object is now dead */ 380 FSCACHE_OBJECT__NSTATES 381 } state; 382 383 int debug_id; /* debugging ID */ 384 int n_children; /* number of child objects */ 385 int n_ops; /* number of extant ops on object */ 386 int n_obj_ops; /* number of object ops outstanding on object */ 387 int n_in_progress; /* number of ops in progress */ 388 int n_exclusive; /* number of exclusive ops queued or in progress */ 389 atomic_t n_reads; /* number of read ops in progress */ 390 spinlock_t lock; /* state and operations lock */ 391 392 unsigned long lookup_jif; /* time at which lookup started */ 393 unsigned long event_mask; /* events this object is interested in */ 394 unsigned long events; /* events to be processed by this object 395 * (order is important - using fls) */ 396 397 unsigned long flags; 398 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ 399 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ 400 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ 401 402 struct list_head cache_link; /* link in cache->object_list */ 403 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 404 struct fscache_cache *cache; /* cache that supplied this object */ 405 struct fscache_cookie *cookie; /* netfs's file/index object */ 406 struct fscache_object *parent; /* parent object */ 407 struct work_struct work; /* attention scheduling record */ 408 struct list_head dependents; /* FIFO of dependent objects */ 409 struct list_head dep_link; /* link in parent's dependents list */ 410 struct list_head pending_ops; /* unstarted operations on this object */ 411 #ifdef CONFIG_FSCACHE_OBJECT_LIST 412 struct rb_node objlist_link; /* link in global object list */ 413 #endif 414 pgoff_t store_limit; /* current storage limit */ 415 loff_t store_limit_l; /* current storage limit */ 416 }; 417 418 extern const char *fscache_object_states[]; 419 420 #define fscache_object_is_active(obj) \ 421 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ 422 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \ 423 (obj)->state < FSCACHE_OBJECT_DYING) 424 425 #define fscache_object_is_dead(obj) \ 426 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ 427 (obj)->state >= FSCACHE_OBJECT_DYING) 428 429 extern void fscache_object_work_func(struct work_struct *work); 430 431 /** 432 * fscache_object_init - Initialise a cache object description 433 * @object: Object description 434 * 435 * Initialise a cache object description to its basic values. 436 * 437 * See Documentation/filesystems/caching/backend-api.txt for a complete 438 * description. 439 */ 440 static inline 441 void fscache_object_init(struct fscache_object *object, 442 struct fscache_cookie *cookie, 443 struct fscache_cache *cache) 444 { 445 atomic_inc(&cache->object_count); 446 447 object->state = FSCACHE_OBJECT_INIT; 448 spin_lock_init(&object->lock); 449 INIT_LIST_HEAD(&object->cache_link); 450 INIT_HLIST_NODE(&object->cookie_link); 451 INIT_WORK(&object->work, fscache_object_work_func); 452 INIT_LIST_HEAD(&object->dependents); 453 INIT_LIST_HEAD(&object->dep_link); 454 INIT_LIST_HEAD(&object->pending_ops); 455 object->n_children = 0; 456 object->n_ops = object->n_in_progress = object->n_exclusive = 0; 457 object->events = object->event_mask = 0; 458 object->flags = 0; 459 object->store_limit = 0; 460 object->store_limit_l = 0; 461 object->cache = cache; 462 object->cookie = cookie; 463 object->parent = NULL; 464 } 465 466 extern void fscache_object_lookup_negative(struct fscache_object *object); 467 extern void fscache_obtained_object(struct fscache_object *object); 468 469 #ifdef CONFIG_FSCACHE_OBJECT_LIST 470 extern void fscache_object_destroy(struct fscache_object *object); 471 #else 472 #define fscache_object_destroy(object) do {} while(0) 473 #endif 474 475 /** 476 * fscache_object_destroyed - Note destruction of an object in a cache 477 * @cache: The cache from which the object came 478 * 479 * Note the destruction and deallocation of an object record in a cache. 480 */ 481 static inline void fscache_object_destroyed(struct fscache_cache *cache) 482 { 483 if (atomic_dec_and_test(&cache->object_count)) 484 wake_up_all(&fscache_cache_cleared_wq); 485 } 486 487 /** 488 * fscache_object_lookup_error - Note an object encountered an error 489 * @object: The object on which the error was encountered 490 * 491 * Note that an object encountered a fatal error (usually an I/O error) and 492 * that it should be withdrawn as soon as possible. 493 */ 494 static inline void fscache_object_lookup_error(struct fscache_object *object) 495 { 496 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 497 } 498 499 /** 500 * fscache_set_store_limit - Set the maximum size to be stored in an object 501 * @object: The object to set the maximum on 502 * @i_size: The limit to set in bytes 503 * 504 * Set the maximum size an object is permitted to reach, implying the highest 505 * byte that may be written. Intended to be called by the attr_changed() op. 506 * 507 * See Documentation/filesystems/caching/backend-api.txt for a complete 508 * description. 509 */ 510 static inline 511 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 512 { 513 object->store_limit_l = i_size; 514 object->store_limit = i_size >> PAGE_SHIFT; 515 if (i_size & ~PAGE_MASK) 516 object->store_limit++; 517 } 518 519 /** 520 * fscache_end_io - End a retrieval operation on a page 521 * @op: The FS-Cache operation covering the retrieval 522 * @page: The page that was to be fetched 523 * @error: The error code (0 if successful) 524 * 525 * Note the end of an operation to retrieve a page, as covered by a particular 526 * operation record. 527 */ 528 static inline void fscache_end_io(struct fscache_retrieval *op, 529 struct page *page, int error) 530 { 531 op->end_io_func(page, op->context, error); 532 } 533 534 /* 535 * out-of-line cache backend functions 536 */ 537 extern __printf(3, 4) 538 void fscache_init_cache(struct fscache_cache *cache, 539 const struct fscache_cache_ops *ops, 540 const char *idfmt, ...); 541 542 extern int fscache_add_cache(struct fscache_cache *cache, 543 struct fscache_object *fsdef, 544 const char *tagname); 545 extern void fscache_withdraw_cache(struct fscache_cache *cache); 546 547 extern void fscache_io_error(struct fscache_cache *cache); 548 549 extern void fscache_mark_page_cached(struct fscache_retrieval *op, 550 struct page *page); 551 552 extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 553 struct pagevec *pagevec); 554 555 extern bool fscache_object_sleep_till_congested(signed long *timeoutp); 556 557 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 558 const void *data, 559 uint16_t datalen); 560 561 #endif /* _LINUX_FSCACHE_CACHE_H */ 562