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/slow-work.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64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66 }; 67 68 extern wait_queue_head_t fscache_cache_cleared_wq; 69 70 /* 71 * operation to be applied to a cache object 72 * - retrieval initiation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 union { 80 struct work_struct fast_work; /* record for fast ops */ 81 struct slow_work slow_work; /* record for (very) slow ops */ 82 }; 83 struct list_head pend_link; /* link in object->pending_ops */ 84 struct fscache_object *object; /* object to be operated upon */ 85 86 unsigned long flags; 87 #define FSCACHE_OP_TYPE 0x000f /* operation type */ 88 #define FSCACHE_OP_FAST 0x0001 /* - fast op, processor may not sleep for disk */ 89 #define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */ 90 #define FSCACHE_OP_MYTHREAD 0x0003 /* - processing is done be issuing thread, not pool */ 91 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ 92 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ 93 #define FSCACHE_OP_DEAD 6 /* op is now dead */ 94 95 atomic_t usage; 96 unsigned debug_id; /* debugging ID */ 97 98 /* operation processor callback 99 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform 100 * the op in a non-pool thread */ 101 fscache_operation_processor_t processor; 102 103 /* operation releaser */ 104 fscache_operation_release_t release; 105 }; 106 107 extern atomic_t fscache_op_debug_id; 108 extern const struct slow_work_ops fscache_op_slow_work_ops; 109 110 extern void fscache_enqueue_operation(struct fscache_operation *); 111 extern void fscache_put_operation(struct fscache_operation *); 112 113 /** 114 * fscache_operation_init - Do basic initialisation of an operation 115 * @op: The operation to initialise 116 * @release: The release function to assign 117 * 118 * Do basic initialisation of an operation. The caller must still set flags, 119 * object, either fast_work or slow_work if necessary, and processor if needed. 120 */ 121 static inline void fscache_operation_init(struct fscache_operation *op, 122 fscache_operation_release_t release) 123 { 124 atomic_set(&op->usage, 1); 125 op->debug_id = atomic_inc_return(&fscache_op_debug_id); 126 op->release = release; 127 INIT_LIST_HEAD(&op->pend_link); 128 } 129 130 /** 131 * fscache_operation_init_slow - Do additional initialisation of a slow op 132 * @op: The operation to initialise 133 * @processor: The processor function to assign 134 * 135 * Do additional initialisation of an operation as required for slow work. 136 */ 137 static inline 138 void fscache_operation_init_slow(struct fscache_operation *op, 139 fscache_operation_processor_t processor) 140 { 141 op->processor = processor; 142 slow_work_init(&op->slow_work, &fscache_op_slow_work_ops); 143 } 144 145 /* 146 * data read operation 147 */ 148 struct fscache_retrieval { 149 struct fscache_operation op; 150 struct address_space *mapping; /* netfs pages */ 151 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ 152 void *context; /* netfs read context (pinned) */ 153 struct list_head to_do; /* list of things to be done by the backend */ 154 unsigned long start_time; /* time at which retrieval started */ 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_put_retrieval - Drop a reference to a retrieval operation 192 * @op: The retrieval operation affected 193 * 194 * Drop a reference to a retrieval operation. 195 */ 196 static inline void fscache_put_retrieval(struct fscache_retrieval *op) 197 { 198 fscache_put_operation(&op->op); 199 } 200 201 /* 202 * cached page storage work item 203 * - used to do three things: 204 * - batch writes to the cache 205 * - do cache writes asynchronously 206 * - defer writes until cache object lookup completion 207 */ 208 struct fscache_storage { 209 struct fscache_operation op; 210 pgoff_t store_limit; /* don't write more than this */ 211 }; 212 213 /* 214 * cache operations 215 */ 216 struct fscache_cache_ops { 217 /* name of cache provider */ 218 const char *name; 219 220 /* allocate an object record for a cookie */ 221 struct fscache_object *(*alloc_object)(struct fscache_cache *cache, 222 struct fscache_cookie *cookie); 223 224 /* look up the object for a cookie */ 225 void (*lookup_object)(struct fscache_object *object); 226 227 /* finished looking up */ 228 void (*lookup_complete)(struct fscache_object *object); 229 230 /* increment the usage count on this object (may fail if unmounting) */ 231 struct fscache_object *(*grab_object)(struct fscache_object *object); 232 233 /* pin an object in the cache */ 234 int (*pin_object)(struct fscache_object *object); 235 236 /* unpin an object in the cache */ 237 void (*unpin_object)(struct fscache_object *object); 238 239 /* store the updated auxilliary data on an object */ 240 void (*update_object)(struct fscache_object *object); 241 242 /* discard the resources pinned by an object and effect retirement if 243 * necessary */ 244 void (*drop_object)(struct fscache_object *object); 245 246 /* dispose of a reference to an object */ 247 void (*put_object)(struct fscache_object *object); 248 249 /* sync a cache */ 250 void (*sync_cache)(struct fscache_cache *cache); 251 252 /* notification that the attributes of a non-index object (such as 253 * i_size) have changed */ 254 int (*attr_changed)(struct fscache_object *object); 255 256 /* reserve space for an object's data and associated metadata */ 257 int (*reserve_space)(struct fscache_object *object, loff_t i_size); 258 259 /* request a backing block for a page be read or allocated in the 260 * cache */ 261 fscache_page_retrieval_func_t read_or_alloc_page; 262 263 /* request backing blocks for a list of pages be read or allocated in 264 * the cache */ 265 fscache_pages_retrieval_func_t read_or_alloc_pages; 266 267 /* request a backing block for a page be allocated in the cache so that 268 * it can be written directly */ 269 fscache_page_retrieval_func_t allocate_page; 270 271 /* request backing blocks for pages be allocated in the cache so that 272 * they can be written directly */ 273 fscache_pages_retrieval_func_t allocate_pages; 274 275 /* write a page to its backing block in the cache */ 276 int (*write_page)(struct fscache_storage *op, struct page *page); 277 278 /* detach backing block from a page (optional) 279 * - must release the cookie lock before returning 280 * - may sleep 281 */ 282 void (*uncache_page)(struct fscache_object *object, 283 struct page *page); 284 285 /* dissociate a cache from all the pages it was backing */ 286 void (*dissociate_pages)(struct fscache_cache *cache); 287 }; 288 289 /* 290 * data file or index object cookie 291 * - a file will only appear in one cache 292 * - a request to cache a file may or may not be honoured, subject to 293 * constraints such as disk space 294 * - indices are created on disk just-in-time 295 */ 296 struct fscache_cookie { 297 atomic_t usage; /* number of users of this cookie */ 298 atomic_t n_children; /* number of children of this cookie */ 299 spinlock_t lock; 300 struct hlist_head backing_objects; /* object(s) backing this file/index */ 301 const struct fscache_cookie_def *def; /* definition */ 302 struct fscache_cookie *parent; /* parent of this entry */ 303 void *netfs_data; /* back pointer to netfs */ 304 struct radix_tree_root stores; /* pages to be stored on this cookie */ 305 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */ 306 307 unsigned long flags; 308 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */ 309 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */ 310 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */ 311 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */ 312 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */ 313 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */ 314 }; 315 316 extern struct fscache_cookie fscache_fsdef_index; 317 318 /* 319 * on-disk cache file or index handle 320 */ 321 struct fscache_object { 322 enum fscache_object_state { 323 FSCACHE_OBJECT_INIT, /* object in initial unbound state */ 324 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */ 325 FSCACHE_OBJECT_CREATING, /* creating object */ 326 327 /* active states */ 328 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */ 329 FSCACHE_OBJECT_ACTIVE, /* object is usable */ 330 FSCACHE_OBJECT_UPDATING, /* object is updating */ 331 332 /* terminal states */ 333 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */ 334 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */ 335 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */ 336 FSCACHE_OBJECT_RELEASING, /* releasing object */ 337 FSCACHE_OBJECT_RECYCLING, /* retiring object */ 338 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */ 339 FSCACHE_OBJECT_DEAD, /* object is now dead */ 340 } state; 341 342 int debug_id; /* debugging ID */ 343 int n_children; /* number of child objects */ 344 int n_ops; /* number of ops outstanding on object */ 345 int n_obj_ops; /* number of object ops outstanding on object */ 346 int n_in_progress; /* number of ops in progress */ 347 int n_exclusive; /* number of exclusive ops queued */ 348 spinlock_t lock; /* state and operations lock */ 349 350 unsigned long lookup_jif; /* time at which lookup started */ 351 unsigned long event_mask; /* events this object is interested in */ 352 unsigned long events; /* events to be processed by this object 353 * (order is important - using fls) */ 354 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */ 355 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */ 356 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */ 357 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */ 358 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */ 359 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */ 360 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */ 361 362 unsigned long flags; 363 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ 364 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ 365 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ 366 367 struct list_head cache_link; /* link in cache->object_list */ 368 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 369 struct fscache_cache *cache; /* cache that supplied this object */ 370 struct fscache_cookie *cookie; /* netfs's file/index object */ 371 struct fscache_object *parent; /* parent object */ 372 struct slow_work work; /* attention scheduling record */ 373 struct list_head dependents; /* FIFO of dependent objects */ 374 struct list_head dep_link; /* link in parent's dependents list */ 375 struct list_head pending_ops; /* unstarted operations on this object */ 376 pgoff_t store_limit; /* current storage limit */ 377 }; 378 379 extern const char *fscache_object_states[]; 380 381 #define fscache_object_is_active(obj) \ 382 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ 383 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \ 384 (obj)->state < FSCACHE_OBJECT_DYING) 385 386 extern const struct slow_work_ops fscache_object_slow_work_ops; 387 388 /** 389 * fscache_object_init - Initialise a cache object description 390 * @object: Object description 391 * 392 * Initialise a cache object description to its basic values. 393 * 394 * See Documentation/filesystems/caching/backend-api.txt for a complete 395 * description. 396 */ 397 static inline 398 void fscache_object_init(struct fscache_object *object, 399 struct fscache_cookie *cookie, 400 struct fscache_cache *cache) 401 { 402 atomic_inc(&cache->object_count); 403 404 object->state = FSCACHE_OBJECT_INIT; 405 spin_lock_init(&object->lock); 406 INIT_LIST_HEAD(&object->cache_link); 407 INIT_HLIST_NODE(&object->cookie_link); 408 vslow_work_init(&object->work, &fscache_object_slow_work_ops); 409 INIT_LIST_HEAD(&object->dependents); 410 INIT_LIST_HEAD(&object->dep_link); 411 INIT_LIST_HEAD(&object->pending_ops); 412 object->n_children = 0; 413 object->n_ops = object->n_in_progress = object->n_exclusive = 0; 414 object->events = object->event_mask = 0; 415 object->flags = 0; 416 object->store_limit = 0; 417 object->cache = cache; 418 object->cookie = cookie; 419 object->parent = NULL; 420 } 421 422 extern void fscache_object_lookup_negative(struct fscache_object *object); 423 extern void fscache_obtained_object(struct fscache_object *object); 424 425 /** 426 * fscache_object_destroyed - Note destruction of an object in a cache 427 * @cache: The cache from which the object came 428 * 429 * Note the destruction and deallocation of an object record in a cache. 430 */ 431 static inline void fscache_object_destroyed(struct fscache_cache *cache) 432 { 433 if (atomic_dec_and_test(&cache->object_count)) 434 wake_up_all(&fscache_cache_cleared_wq); 435 } 436 437 /** 438 * fscache_object_lookup_error - Note an object encountered an error 439 * @object: The object on which the error was encountered 440 * 441 * Note that an object encountered a fatal error (usually an I/O error) and 442 * that it should be withdrawn as soon as possible. 443 */ 444 static inline void fscache_object_lookup_error(struct fscache_object *object) 445 { 446 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 447 } 448 449 /** 450 * fscache_set_store_limit - Set the maximum size to be stored in an object 451 * @object: The object to set the maximum on 452 * @i_size: The limit to set in bytes 453 * 454 * Set the maximum size an object is permitted to reach, implying the highest 455 * byte that may be written. Intended to be called by the attr_changed() op. 456 * 457 * See Documentation/filesystems/caching/backend-api.txt for a complete 458 * description. 459 */ 460 static inline 461 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 462 { 463 object->store_limit = i_size >> PAGE_SHIFT; 464 if (i_size & ~PAGE_MASK) 465 object->store_limit++; 466 } 467 468 /** 469 * fscache_end_io - End a retrieval operation on a page 470 * @op: The FS-Cache operation covering the retrieval 471 * @page: The page that was to be fetched 472 * @error: The error code (0 if successful) 473 * 474 * Note the end of an operation to retrieve a page, as covered by a particular 475 * operation record. 476 */ 477 static inline void fscache_end_io(struct fscache_retrieval *op, 478 struct page *page, int error) 479 { 480 op->end_io_func(page, op->context, error); 481 } 482 483 /* 484 * out-of-line cache backend functions 485 */ 486 extern void fscache_init_cache(struct fscache_cache *cache, 487 const struct fscache_cache_ops *ops, 488 const char *idfmt, 489 ...) __attribute__ ((format (printf, 3, 4))); 490 491 extern int fscache_add_cache(struct fscache_cache *cache, 492 struct fscache_object *fsdef, 493 const char *tagname); 494 extern void fscache_withdraw_cache(struct fscache_cache *cache); 495 496 extern void fscache_io_error(struct fscache_cache *cache); 497 498 extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 499 struct pagevec *pagevec); 500 501 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 502 const void *data, 503 uint16_t datalen); 504 505 #endif /* _LINUX_FSCACHE_CACHE_H */ 506