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64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66 }; 67 68 extern wait_queue_head_t fscache_cache_cleared_wq; 69 70 /* 71 * operation to be applied to a cache object 72 * - retrieval initiation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_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */ 101 #define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */ 102 103 enum fscache_operation_state state; 104 atomic_t usage; 105 unsigned debug_id; /* debugging ID */ 106 107 /* operation processor callback 108 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform 109 * the op in a non-pool thread */ 110 fscache_operation_processor_t processor; 111 112 /* operation releaser */ 113 fscache_operation_release_t release; 114 }; 115 116 extern atomic_t fscache_op_debug_id; 117 extern void fscache_op_work_func(struct work_struct *work); 118 119 extern void fscache_enqueue_operation(struct fscache_operation *); 120 extern void fscache_op_complete(struct fscache_operation *, bool); 121 extern void fscache_put_operation(struct fscache_operation *); 122 123 /** 124 * fscache_operation_init - Do basic initialisation of an operation 125 * @op: The operation to initialise 126 * @release: The release function to assign 127 * 128 * Do basic initialisation of an operation. The caller must still set flags, 129 * object and processor if needed. 130 */ 131 static inline void fscache_operation_init(struct fscache_operation *op, 132 fscache_operation_processor_t processor, 133 fscache_operation_release_t release) 134 { 135 INIT_WORK(&op->work, fscache_op_work_func); 136 atomic_set(&op->usage, 1); 137 op->state = FSCACHE_OP_ST_INITIALISED; 138 op->debug_id = atomic_inc_return(&fscache_op_debug_id); 139 op->processor = processor; 140 op->release = release; 141 INIT_LIST_HEAD(&op->pend_link); 142 } 143 144 /* 145 * data read operation 146 */ 147 struct fscache_retrieval { 148 struct fscache_operation op; 149 struct address_space *mapping; /* netfs pages */ 150 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ 151 void *context; /* netfs read context (pinned) */ 152 struct list_head to_do; /* list of things to be done by the backend */ 153 unsigned long start_time; /* time at which retrieval started */ 154 atomic_t n_pages; /* number of pages to be retrieved */ 155 }; 156 157 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, 158 struct page *page, 159 gfp_t gfp); 160 161 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, 162 struct list_head *pages, 163 unsigned *nr_pages, 164 gfp_t gfp); 165 166 /** 167 * fscache_get_retrieval - Get an extra reference on a retrieval operation 168 * @op: The retrieval operation to get a reference on 169 * 170 * Get an extra reference on a retrieval operation. 171 */ 172 static inline 173 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) 174 { 175 atomic_inc(&op->op.usage); 176 return op; 177 } 178 179 /** 180 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing 181 * @op: The retrieval operation affected 182 * 183 * Enqueue a retrieval operation for processing by the FS-Cache thread pool. 184 */ 185 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) 186 { 187 fscache_enqueue_operation(&op->op); 188 } 189 190 /** 191 * fscache_retrieval_complete - Record (partial) completion of a retrieval 192 * @op: The retrieval operation affected 193 * @n_pages: The number of pages to account for 194 */ 195 static inline void fscache_retrieval_complete(struct fscache_retrieval *op, 196 int n_pages) 197 { 198 atomic_sub(n_pages, &op->n_pages); 199 if (atomic_read(&op->n_pages) <= 0) 200 fscache_op_complete(&op->op, true); 201 } 202 203 /** 204 * fscache_put_retrieval - Drop a reference to a retrieval operation 205 * @op: The retrieval operation affected 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 /* check the consistency between the backing cache and the FS-Cache 255 * cookie */ 256 bool (*check_consistency)(struct fscache_operation *op); 257 258 /* store the updated auxiliary data on an object */ 259 void (*update_object)(struct fscache_object *object); 260 261 /* Invalidate an object */ 262 void (*invalidate_object)(struct fscache_operation *op); 263 264 /* discard the resources pinned by an object and effect retirement if 265 * necessary */ 266 void (*drop_object)(struct fscache_object *object); 267 268 /* dispose of a reference to an object */ 269 void (*put_object)(struct fscache_object *object); 270 271 /* sync a cache */ 272 void (*sync_cache)(struct fscache_cache *cache); 273 274 /* notification that the attributes of a non-index object (such as 275 * i_size) have changed */ 276 int (*attr_changed)(struct fscache_object *object); 277 278 /* reserve space for an object's data and associated metadata */ 279 int (*reserve_space)(struct fscache_object *object, loff_t i_size); 280 281 /* request a backing block for a page be read or allocated in the 282 * cache */ 283 fscache_page_retrieval_func_t read_or_alloc_page; 284 285 /* request backing blocks for a list of pages be read or allocated in 286 * the cache */ 287 fscache_pages_retrieval_func_t read_or_alloc_pages; 288 289 /* request a backing block for a page be allocated in the cache so that 290 * it can be written directly */ 291 fscache_page_retrieval_func_t allocate_page; 292 293 /* request backing blocks for pages be allocated in the cache so that 294 * they can be written directly */ 295 fscache_pages_retrieval_func_t allocate_pages; 296 297 /* write a page to its backing block in the cache */ 298 int (*write_page)(struct fscache_storage *op, struct page *page); 299 300 /* detach backing block from a page (optional) 301 * - must release the cookie lock before returning 302 * - may sleep 303 */ 304 void (*uncache_page)(struct fscache_object *object, 305 struct page *page); 306 307 /* dissociate a cache from all the pages it was backing */ 308 void (*dissociate_pages)(struct fscache_cache *cache); 309 }; 310 311 /* 312 * data file or index object cookie 313 * - a file will only appear in one cache 314 * - a request to cache a file may or may not be honoured, subject to 315 * constraints such as disk space 316 * - indices are created on disk just-in-time 317 */ 318 struct fscache_cookie { 319 atomic_t usage; /* number of users of this cookie */ 320 atomic_t n_children; /* number of children of this cookie */ 321 atomic_t n_active; /* number of active users of netfs ptrs */ 322 spinlock_t lock; 323 spinlock_t stores_lock; /* lock on page store tree */ 324 struct hlist_head backing_objects; /* object(s) backing this file/index */ 325 const struct fscache_cookie_def *def; /* definition */ 326 struct fscache_cookie *parent; /* parent of this entry */ 327 void *netfs_data; /* back pointer to netfs */ 328 struct radix_tree_root stores; /* pages to be stored on this cookie */ 329 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */ 330 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */ 331 332 unsigned long flags; 333 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */ 334 #define FSCACHE_COOKIE_NO_DATA_YET 1 /* T if new object with no cached data yet */ 335 #define FSCACHE_COOKIE_UNAVAILABLE 2 /* T if cookie is unavailable (error, etc) */ 336 #define FSCACHE_COOKIE_INVALIDATING 3 /* T if cookie is being invalidated */ 337 #define FSCACHE_COOKIE_RELINQUISHED 4 /* T if cookie has been relinquished */ 338 #define FSCACHE_COOKIE_RETIRED 5 /* T if cookie was retired */ 339 }; 340 341 extern struct fscache_cookie fscache_fsdef_index; 342 343 /* 344 * Event list for fscache_object::{event_mask,events} 345 */ 346 enum { 347 FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */ 348 FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */ 349 FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */ 350 FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */ 351 FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */ 352 FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */ 353 FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */ 354 NR_FSCACHE_OBJECT_EVENTS 355 }; 356 357 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1) 358 359 /* 360 * States for object state machine. 361 */ 362 struct fscache_transition { 363 unsigned long events; 364 const struct fscache_state *transit_to; 365 }; 366 367 struct fscache_state { 368 char name[24]; 369 char short_name[8]; 370 const struct fscache_state *(*work)(struct fscache_object *object, 371 int event); 372 const struct fscache_transition transitions[]; 373 }; 374 375 /* 376 * on-disk cache file or index handle 377 */ 378 struct fscache_object { 379 const struct fscache_state *state; /* Object state machine state */ 380 const struct fscache_transition *oob_table; /* OOB state transition table */ 381 int debug_id; /* debugging ID */ 382 int n_children; /* number of child objects */ 383 int n_ops; /* number of extant ops on object */ 384 int n_obj_ops; /* number of object ops outstanding on object */ 385 int n_in_progress; /* number of ops in progress */ 386 int n_exclusive; /* number of exclusive ops queued or in progress */ 387 atomic_t n_reads; /* number of read ops in progress */ 388 spinlock_t lock; /* state and operations lock */ 389 390 unsigned long lookup_jif; /* time at which lookup started */ 391 unsigned long oob_event_mask; /* OOB events this object is interested in */ 392 unsigned long event_mask; /* events this object is interested in */ 393 unsigned long events; /* events to be processed by this object 394 * (order is important - using fls) */ 395 396 unsigned long flags; 397 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ 398 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ 399 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ 400 #define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */ 401 #define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */ 402 #define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */ 403 404 struct list_head cache_link; /* link in cache->object_list */ 405 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 406 struct fscache_cache *cache; /* cache that supplied this object */ 407 struct fscache_cookie *cookie; /* netfs's file/index object */ 408 struct fscache_object *parent; /* parent object */ 409 struct work_struct work; /* attention scheduling record */ 410 struct list_head dependents; /* FIFO of dependent objects */ 411 struct list_head dep_link; /* link in parent's dependents list */ 412 struct list_head pending_ops; /* unstarted operations on this object */ 413 #ifdef CONFIG_FSCACHE_OBJECT_LIST 414 struct rb_node objlist_link; /* link in global object list */ 415 #endif 416 pgoff_t store_limit; /* current storage limit */ 417 loff_t store_limit_l; /* current storage limit */ 418 }; 419 420 extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *, 421 struct fscache_cache *); 422 extern void fscache_object_destroy(struct fscache_object *); 423 424 extern void fscache_object_lookup_negative(struct fscache_object *object); 425 extern void fscache_obtained_object(struct fscache_object *object); 426 427 static inline bool fscache_object_is_live(struct fscache_object *object) 428 { 429 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); 430 } 431 432 static inline bool fscache_object_is_dying(struct fscache_object *object) 433 { 434 return !fscache_object_is_live(object); 435 } 436 437 static inline bool fscache_object_is_available(struct fscache_object *object) 438 { 439 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags); 440 } 441 442 static inline bool fscache_object_is_active(struct fscache_object *object) 443 { 444 return fscache_object_is_available(object) && 445 fscache_object_is_live(object) && 446 !test_bit(FSCACHE_IOERROR, &object->cache->flags); 447 } 448 449 static inline bool fscache_object_is_dead(struct fscache_object *object) 450 { 451 return fscache_object_is_dying(object) && 452 test_bit(FSCACHE_IOERROR, &object->cache->flags); 453 } 454 455 /** 456 * fscache_object_destroyed - Note destruction of an object in a cache 457 * @cache: The cache from which the object came 458 * 459 * Note the destruction and deallocation of an object record in a cache. 460 */ 461 static inline void fscache_object_destroyed(struct fscache_cache *cache) 462 { 463 if (atomic_dec_and_test(&cache->object_count)) 464 wake_up_all(&fscache_cache_cleared_wq); 465 } 466 467 /** 468 * fscache_object_lookup_error - Note an object encountered an error 469 * @object: The object on which the error was encountered 470 * 471 * Note that an object encountered a fatal error (usually an I/O error) and 472 * that it should be withdrawn as soon as possible. 473 */ 474 static inline void fscache_object_lookup_error(struct fscache_object *object) 475 { 476 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 477 } 478 479 /** 480 * fscache_set_store_limit - Set the maximum size to be stored in an object 481 * @object: The object to set the maximum on 482 * @i_size: The limit to set in bytes 483 * 484 * Set the maximum size an object is permitted to reach, implying the highest 485 * byte that may be written. Intended to be called by the attr_changed() op. 486 * 487 * See Documentation/filesystems/caching/backend-api.txt for a complete 488 * description. 489 */ 490 static inline 491 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 492 { 493 object->store_limit_l = i_size; 494 object->store_limit = i_size >> PAGE_SHIFT; 495 if (i_size & ~PAGE_MASK) 496 object->store_limit++; 497 } 498 499 /** 500 * fscache_end_io - End a retrieval operation on a page 501 * @op: The FS-Cache operation covering the retrieval 502 * @page: The page that was to be fetched 503 * @error: The error code (0 if successful) 504 * 505 * Note the end of an operation to retrieve a page, as covered by a particular 506 * operation record. 507 */ 508 static inline void fscache_end_io(struct fscache_retrieval *op, 509 struct page *page, int error) 510 { 511 op->end_io_func(page, op->context, error); 512 } 513 514 /** 515 * fscache_use_cookie - Request usage of cookie attached to an object 516 * @object: Object description 517 * 518 * Request usage of the cookie attached to an object. NULL is returned if the 519 * relinquishment had reduced the cookie usage count to 0. 520 */ 521 static inline bool fscache_use_cookie(struct fscache_object *object) 522 { 523 struct fscache_cookie *cookie = object->cookie; 524 return atomic_inc_not_zero(&cookie->n_active) != 0; 525 } 526 527 /** 528 * fscache_unuse_cookie - Cease usage of cookie attached to an object 529 * @object: Object description 530 * 531 * Cease usage of the cookie attached to an object. When the users count 532 * reaches zero then the cookie relinquishment will be permitted to proceed. 533 */ 534 static inline void fscache_unuse_cookie(struct fscache_object *object) 535 { 536 struct fscache_cookie *cookie = object->cookie; 537 if (atomic_dec_and_test(&cookie->n_active)) 538 wake_up_atomic_t(&cookie->n_active); 539 } 540 541 /* 542 * out-of-line cache backend functions 543 */ 544 extern __printf(3, 4) 545 void fscache_init_cache(struct fscache_cache *cache, 546 const struct fscache_cache_ops *ops, 547 const char *idfmt, ...); 548 549 extern int fscache_add_cache(struct fscache_cache *cache, 550 struct fscache_object *fsdef, 551 const char *tagname); 552 extern void fscache_withdraw_cache(struct fscache_cache *cache); 553 554 extern void fscache_io_error(struct fscache_cache *cache); 555 556 extern void fscache_mark_page_cached(struct fscache_retrieval *op, 557 struct page *page); 558 559 extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 560 struct pagevec *pagevec); 561 562 extern bool fscache_object_sleep_till_congested(signed long *timeoutp); 563 564 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 565 const void *data, 566 uint16_t datalen); 567 568 #endif /* _LINUX_FSCACHE_CACHE_H */ 569