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64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66 }; 67 68 extern wait_queue_head_t fscache_cache_cleared_wq; 69 70 /* 71 * operation to be applied to a cache object 72 * - retrieval initiation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 struct fscache_operation { 79 struct work_struct work; /* record for async ops */ 80 struct list_head pend_link; /* link in object->pending_ops */ 81 struct fscache_object *object; /* object to be operated upon */ 82 83 unsigned long flags; 84 #define FSCACHE_OP_TYPE 0x000f /* operation type */ 85 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */ 86 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */ 87 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ 88 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ 89 #define FSCACHE_OP_DEAD 6 /* op is now dead */ 90 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */ 91 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */ 92 93 atomic_t usage; 94 unsigned debug_id; /* debugging ID */ 95 96 /* operation processor callback 97 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform 98 * the op in a non-pool thread */ 99 fscache_operation_processor_t processor; 100 101 /* operation releaser */ 102 fscache_operation_release_t release; 103 }; 104 105 extern atomic_t fscache_op_debug_id; 106 extern void fscache_op_work_func(struct work_struct *work); 107 108 extern void fscache_enqueue_operation(struct fscache_operation *); 109 extern void fscache_put_operation(struct fscache_operation *); 110 111 /** 112 * fscache_operation_init - Do basic initialisation of an operation 113 * @op: The operation to initialise 114 * @release: The release function to assign 115 * 116 * Do basic initialisation of an operation. The caller must still set flags, 117 * object and processor if needed. 118 */ 119 static inline void fscache_operation_init(struct fscache_operation *op, 120 fscache_operation_processor_t processor, 121 fscache_operation_release_t release) 122 { 123 INIT_WORK(&op->work, fscache_op_work_func); 124 atomic_set(&op->usage, 1); 125 op->debug_id = atomic_inc_return(&fscache_op_debug_id); 126 op->processor = processor; 127 op->release = release; 128 INIT_LIST_HEAD(&op->pend_link); 129 } 130 131 /* 132 * data read operation 133 */ 134 struct fscache_retrieval { 135 struct fscache_operation op; 136 struct address_space *mapping; /* netfs pages */ 137 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ 138 void *context; /* netfs read context (pinned) */ 139 struct list_head to_do; /* list of things to be done by the backend */ 140 unsigned long start_time; /* time at which retrieval started */ 141 }; 142 143 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, 144 struct page *page, 145 gfp_t gfp); 146 147 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, 148 struct list_head *pages, 149 unsigned *nr_pages, 150 gfp_t gfp); 151 152 /** 153 * fscache_get_retrieval - Get an extra reference on a retrieval operation 154 * @op: The retrieval operation to get a reference on 155 * 156 * Get an extra reference on a retrieval operation. 157 */ 158 static inline 159 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) 160 { 161 atomic_inc(&op->op.usage); 162 return op; 163 } 164 165 /** 166 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing 167 * @op: The retrieval operation affected 168 * 169 * Enqueue a retrieval operation for processing by the FS-Cache thread pool. 170 */ 171 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) 172 { 173 fscache_enqueue_operation(&op->op); 174 } 175 176 /** 177 * fscache_put_retrieval - Drop a reference to a retrieval operation 178 * @op: The retrieval operation affected 179 * 180 * Drop a reference to a retrieval operation. 181 */ 182 static inline void fscache_put_retrieval(struct fscache_retrieval *op) 183 { 184 fscache_put_operation(&op->op); 185 } 186 187 /* 188 * cached page storage work item 189 * - used to do three things: 190 * - batch writes to the cache 191 * - do cache writes asynchronously 192 * - defer writes until cache object lookup completion 193 */ 194 struct fscache_storage { 195 struct fscache_operation op; 196 pgoff_t store_limit; /* don't write more than this */ 197 }; 198 199 /* 200 * cache operations 201 */ 202 struct fscache_cache_ops { 203 /* name of cache provider */ 204 const char *name; 205 206 /* allocate an object record for a cookie */ 207 struct fscache_object *(*alloc_object)(struct fscache_cache *cache, 208 struct fscache_cookie *cookie); 209 210 /* look up the object for a cookie 211 * - return -ETIMEDOUT to be requeued 212 */ 213 int (*lookup_object)(struct fscache_object *object); 214 215 /* finished looking up */ 216 void (*lookup_complete)(struct fscache_object *object); 217 218 /* increment the usage count on this object (may fail if unmounting) */ 219 struct fscache_object *(*grab_object)(struct fscache_object *object); 220 221 /* pin an object in the cache */ 222 int (*pin_object)(struct fscache_object *object); 223 224 /* unpin an object in the cache */ 225 void (*unpin_object)(struct fscache_object *object); 226 227 /* store the updated auxiliary data on an object */ 228 void (*update_object)(struct fscache_object *object); 229 230 /* discard the resources pinned by an object and effect retirement if 231 * necessary */ 232 void (*drop_object)(struct fscache_object *object); 233 234 /* dispose of a reference to an object */ 235 void (*put_object)(struct fscache_object *object); 236 237 /* sync a cache */ 238 void (*sync_cache)(struct fscache_cache *cache); 239 240 /* notification that the attributes of a non-index object (such as 241 * i_size) have changed */ 242 int (*attr_changed)(struct fscache_object *object); 243 244 /* reserve space for an object's data and associated metadata */ 245 int (*reserve_space)(struct fscache_object *object, loff_t i_size); 246 247 /* request a backing block for a page be read or allocated in the 248 * cache */ 249 fscache_page_retrieval_func_t read_or_alloc_page; 250 251 /* request backing blocks for a list of pages be read or allocated in 252 * the cache */ 253 fscache_pages_retrieval_func_t read_or_alloc_pages; 254 255 /* request a backing block for a page be allocated in the cache so that 256 * it can be written directly */ 257 fscache_page_retrieval_func_t allocate_page; 258 259 /* request backing blocks for pages be allocated in the cache so that 260 * they can be written directly */ 261 fscache_pages_retrieval_func_t allocate_pages; 262 263 /* write a page to its backing block in the cache */ 264 int (*write_page)(struct fscache_storage *op, struct page *page); 265 266 /* detach backing block from a page (optional) 267 * - must release the cookie lock before returning 268 * - may sleep 269 */ 270 void (*uncache_page)(struct fscache_object *object, 271 struct page *page); 272 273 /* dissociate a cache from all the pages it was backing */ 274 void (*dissociate_pages)(struct fscache_cache *cache); 275 }; 276 277 /* 278 * data file or index object cookie 279 * - a file will only appear in one cache 280 * - a request to cache a file may or may not be honoured, subject to 281 * constraints such as disk space 282 * - indices are created on disk just-in-time 283 */ 284 struct fscache_cookie { 285 atomic_t usage; /* number of users of this cookie */ 286 atomic_t n_children; /* number of children of this cookie */ 287 spinlock_t lock; 288 spinlock_t stores_lock; /* lock on page store tree */ 289 struct hlist_head backing_objects; /* object(s) backing this file/index */ 290 const struct fscache_cookie_def *def; /* definition */ 291 struct fscache_cookie *parent; /* parent of this entry */ 292 void *netfs_data; /* back pointer to netfs */ 293 struct radix_tree_root stores; /* pages to be stored on this cookie */ 294 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */ 295 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */ 296 297 unsigned long flags; 298 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */ 299 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */ 300 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */ 301 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */ 302 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */ 303 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */ 304 }; 305 306 extern struct fscache_cookie fscache_fsdef_index; 307 308 /* 309 * on-disk cache file or index handle 310 */ 311 struct fscache_object { 312 enum fscache_object_state { 313 FSCACHE_OBJECT_INIT, /* object in initial unbound state */ 314 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */ 315 FSCACHE_OBJECT_CREATING, /* creating object */ 316 317 /* active states */ 318 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */ 319 FSCACHE_OBJECT_ACTIVE, /* object is usable */ 320 FSCACHE_OBJECT_UPDATING, /* object is updating */ 321 322 /* terminal states */ 323 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */ 324 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */ 325 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */ 326 FSCACHE_OBJECT_RELEASING, /* releasing object */ 327 FSCACHE_OBJECT_RECYCLING, /* retiring object */ 328 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */ 329 FSCACHE_OBJECT_DEAD, /* object is now dead */ 330 FSCACHE_OBJECT__NSTATES 331 } state; 332 333 int debug_id; /* debugging ID */ 334 int n_children; /* number of child objects */ 335 int n_ops; /* number of ops outstanding on object */ 336 int n_obj_ops; /* number of object ops outstanding on object */ 337 int n_in_progress; /* number of ops in progress */ 338 int n_exclusive; /* number of exclusive ops queued */ 339 atomic_t n_reads; /* number of read ops in progress */ 340 spinlock_t lock; /* state and operations lock */ 341 342 unsigned long lookup_jif; /* time at which lookup started */ 343 unsigned long event_mask; /* events this object is interested in */ 344 unsigned long events; /* events to be processed by this object 345 * (order is important - using fls) */ 346 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */ 347 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */ 348 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */ 349 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */ 350 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */ 351 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */ 352 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */ 353 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/ 354 355 unsigned long flags; 356 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ 357 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ 358 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ 359 360 struct list_head cache_link; /* link in cache->object_list */ 361 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 362 struct fscache_cache *cache; /* cache that supplied this object */ 363 struct fscache_cookie *cookie; /* netfs's file/index object */ 364 struct fscache_object *parent; /* parent object */ 365 struct work_struct work; /* attention scheduling record */ 366 struct list_head dependents; /* FIFO of dependent objects */ 367 struct list_head dep_link; /* link in parent's dependents list */ 368 struct list_head pending_ops; /* unstarted operations on this object */ 369 #ifdef CONFIG_FSCACHE_OBJECT_LIST 370 struct rb_node objlist_link; /* link in global object list */ 371 #endif 372 pgoff_t store_limit; /* current storage limit */ 373 loff_t store_limit_l; /* current storage limit */ 374 }; 375 376 extern const char *fscache_object_states[]; 377 378 #define fscache_object_is_active(obj) \ 379 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ 380 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \ 381 (obj)->state < FSCACHE_OBJECT_DYING) 382 383 #define fscache_object_is_dead(obj) \ 384 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ 385 (obj)->state >= FSCACHE_OBJECT_DYING) 386 387 extern void fscache_object_work_func(struct work_struct *work); 388 389 /** 390 * fscache_object_init - Initialise a cache object description 391 * @object: Object description 392 * 393 * Initialise a cache object description to its basic values. 394 * 395 * See Documentation/filesystems/caching/backend-api.txt for a complete 396 * description. 397 */ 398 static inline 399 void fscache_object_init(struct fscache_object *object, 400 struct fscache_cookie *cookie, 401 struct fscache_cache *cache) 402 { 403 atomic_inc(&cache->object_count); 404 405 object->state = FSCACHE_OBJECT_INIT; 406 spin_lock_init(&object->lock); 407 INIT_LIST_HEAD(&object->cache_link); 408 INIT_HLIST_NODE(&object->cookie_link); 409 INIT_WORK(&object->work, fscache_object_work_func); 410 INIT_LIST_HEAD(&object->dependents); 411 INIT_LIST_HEAD(&object->dep_link); 412 INIT_LIST_HEAD(&object->pending_ops); 413 object->n_children = 0; 414 object->n_ops = object->n_in_progress = object->n_exclusive = 0; 415 object->events = object->event_mask = 0; 416 object->flags = 0; 417 object->store_limit = 0; 418 object->store_limit_l = 0; 419 object->cache = cache; 420 object->cookie = cookie; 421 object->parent = NULL; 422 } 423 424 extern void fscache_object_lookup_negative(struct fscache_object *object); 425 extern void fscache_obtained_object(struct fscache_object *object); 426 427 #ifdef CONFIG_FSCACHE_OBJECT_LIST 428 extern void fscache_object_destroy(struct fscache_object *object); 429 #else 430 #define fscache_object_destroy(object) do {} while(0) 431 #endif 432 433 /** 434 * fscache_object_destroyed - Note destruction of an object in a cache 435 * @cache: The cache from which the object came 436 * 437 * Note the destruction and deallocation of an object record in a cache. 438 */ 439 static inline void fscache_object_destroyed(struct fscache_cache *cache) 440 { 441 if (atomic_dec_and_test(&cache->object_count)) 442 wake_up_all(&fscache_cache_cleared_wq); 443 } 444 445 /** 446 * fscache_object_lookup_error - Note an object encountered an error 447 * @object: The object on which the error was encountered 448 * 449 * Note that an object encountered a fatal error (usually an I/O error) and 450 * that it should be withdrawn as soon as possible. 451 */ 452 static inline void fscache_object_lookup_error(struct fscache_object *object) 453 { 454 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 455 } 456 457 /** 458 * fscache_set_store_limit - Set the maximum size to be stored in an object 459 * @object: The object to set the maximum on 460 * @i_size: The limit to set in bytes 461 * 462 * Set the maximum size an object is permitted to reach, implying the highest 463 * byte that may be written. Intended to be called by the attr_changed() op. 464 * 465 * See Documentation/filesystems/caching/backend-api.txt for a complete 466 * description. 467 */ 468 static inline 469 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 470 { 471 object->store_limit_l = i_size; 472 object->store_limit = i_size >> PAGE_SHIFT; 473 if (i_size & ~PAGE_MASK) 474 object->store_limit++; 475 } 476 477 /** 478 * fscache_end_io - End a retrieval operation on a page 479 * @op: The FS-Cache operation covering the retrieval 480 * @page: The page that was to be fetched 481 * @error: The error code (0 if successful) 482 * 483 * Note the end of an operation to retrieve a page, as covered by a particular 484 * operation record. 485 */ 486 static inline void fscache_end_io(struct fscache_retrieval *op, 487 struct page *page, int error) 488 { 489 op->end_io_func(page, op->context, error); 490 } 491 492 /* 493 * out-of-line cache backend functions 494 */ 495 extern __printf(3, 4) 496 void fscache_init_cache(struct fscache_cache *cache, 497 const struct fscache_cache_ops *ops, 498 const char *idfmt, ...); 499 500 extern int fscache_add_cache(struct fscache_cache *cache, 501 struct fscache_object *fsdef, 502 const char *tagname); 503 extern void fscache_withdraw_cache(struct fscache_cache *cache); 504 505 extern void fscache_io_error(struct fscache_cache *cache); 506 507 extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 508 struct pagevec *pagevec); 509 510 extern bool fscache_object_sleep_till_congested(signed long *timeoutp); 511 512 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 513 const void *data, 514 uint16_t datalen); 515 516 #endif /* _LINUX_FSCACHE_CACHE_H */ 517