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64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66 }; 67 68 extern wait_queue_head_t fscache_cache_cleared_wq; 69 70 /* 71 * operation to be applied to a cache object 72 * - retrieval initiation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 typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op); 78 79 enum fscache_operation_state { 80 FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */ 81 FSCACHE_OP_ST_INITIALISED, /* Op is initialised */ 82 FSCACHE_OP_ST_PENDING, /* Op is blocked from running */ 83 FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */ 84 FSCACHE_OP_ST_COMPLETE, /* Op is complete */ 85 FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */ 86 FSCACHE_OP_ST_DEAD /* Op is now dead */ 87 }; 88 89 struct fscache_operation { 90 struct work_struct work; /* record for async ops */ 91 struct list_head pend_link; /* link in object->pending_ops */ 92 struct fscache_object *object; /* object to be operated upon */ 93 94 unsigned long flags; 95 #define FSCACHE_OP_TYPE 0x000f /* operation type */ 96 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */ 97 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */ 98 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ 99 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ 100 #define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */ 101 #define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */ 102 #define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */ 103 104 enum fscache_operation_state state; 105 atomic_t usage; 106 unsigned debug_id; /* debugging ID */ 107 108 /* operation processor callback 109 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform 110 * the op in a non-pool thread */ 111 fscache_operation_processor_t processor; 112 113 /* Operation cancellation cleanup (optional) */ 114 fscache_operation_cancel_t cancel; 115 116 /* operation releaser */ 117 fscache_operation_release_t release; 118 }; 119 120 extern atomic_t fscache_op_debug_id; 121 extern void fscache_op_work_func(struct work_struct *work); 122 123 extern void fscache_enqueue_operation(struct fscache_operation *); 124 extern void fscache_op_complete(struct fscache_operation *, bool); 125 extern void fscache_put_operation(struct fscache_operation *); 126 extern void fscache_operation_init(struct fscache_operation *, 127 fscache_operation_processor_t, 128 fscache_operation_cancel_t, 129 fscache_operation_release_t); 130 131 /* 132 * data read operation 133 */ 134 struct fscache_retrieval { 135 struct fscache_operation op; 136 struct fscache_cookie *cookie; /* The netfs cookie */ 137 struct address_space *mapping; /* netfs pages */ 138 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ 139 void *context; /* netfs read context (pinned) */ 140 struct list_head to_do; /* list of things to be done by the backend */ 141 unsigned long start_time; /* time at which retrieval started */ 142 atomic_t n_pages; /* number of pages to be retrieved */ 143 }; 144 145 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, 146 struct page *page, 147 gfp_t gfp); 148 149 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, 150 struct list_head *pages, 151 unsigned *nr_pages, 152 gfp_t gfp); 153 154 /** 155 * fscache_get_retrieval - Get an extra reference on a retrieval operation 156 * @op: The retrieval operation to get a reference on 157 * 158 * Get an extra reference on a retrieval operation. 159 */ 160 static inline 161 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) 162 { 163 atomic_inc(&op->op.usage); 164 return op; 165 } 166 167 /** 168 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing 169 * @op: The retrieval operation affected 170 * 171 * Enqueue a retrieval operation for processing by the FS-Cache thread pool. 172 */ 173 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) 174 { 175 fscache_enqueue_operation(&op->op); 176 } 177 178 /** 179 * fscache_retrieval_complete - Record (partial) completion of a retrieval 180 * @op: The retrieval operation affected 181 * @n_pages: The number of pages to account for 182 */ 183 static inline void fscache_retrieval_complete(struct fscache_retrieval *op, 184 int n_pages) 185 { 186 atomic_sub(n_pages, &op->n_pages); 187 if (atomic_read(&op->n_pages) <= 0) 188 fscache_op_complete(&op->op, true); 189 } 190 191 /** 192 * fscache_put_retrieval - Drop a reference to a retrieval operation 193 * @op: The retrieval operation affected 194 * 195 * Drop a reference to a retrieval operation. 196 */ 197 static inline void fscache_put_retrieval(struct fscache_retrieval *op) 198 { 199 fscache_put_operation(&op->op); 200 } 201 202 /* 203 * cached page storage work item 204 * - used to do three things: 205 * - batch writes to the cache 206 * - do cache writes asynchronously 207 * - defer writes until cache object lookup completion 208 */ 209 struct fscache_storage { 210 struct fscache_operation op; 211 pgoff_t store_limit; /* don't write more than this */ 212 }; 213 214 /* 215 * cache operations 216 */ 217 struct fscache_cache_ops { 218 /* name of cache provider */ 219 const char *name; 220 221 /* allocate an object record for a cookie */ 222 struct fscache_object *(*alloc_object)(struct fscache_cache *cache, 223 struct fscache_cookie *cookie); 224 225 /* look up the object for a cookie 226 * - return -ETIMEDOUT to be requeued 227 */ 228 int (*lookup_object)(struct fscache_object *object); 229 230 /* finished looking up */ 231 void (*lookup_complete)(struct fscache_object *object); 232 233 /* increment the usage count on this object (may fail if unmounting) */ 234 struct fscache_object *(*grab_object)(struct fscache_object *object); 235 236 /* pin an object in the cache */ 237 int (*pin_object)(struct fscache_object *object); 238 239 /* unpin an object in the cache */ 240 void (*unpin_object)(struct fscache_object *object); 241 242 /* check the consistency between the backing cache and the FS-Cache 243 * cookie */ 244 int (*check_consistency)(struct fscache_operation *op); 245 246 /* store the updated auxiliary data on an object */ 247 void (*update_object)(struct fscache_object *object); 248 249 /* Invalidate an object */ 250 void (*invalidate_object)(struct fscache_operation *op); 251 252 /* discard the resources pinned by an object and effect retirement if 253 * necessary */ 254 void (*drop_object)(struct fscache_object *object); 255 256 /* dispose of a reference to an object */ 257 void (*put_object)(struct fscache_object *object); 258 259 /* sync a cache */ 260 void (*sync_cache)(struct fscache_cache *cache); 261 262 /* notification that the attributes of a non-index object (such as 263 * i_size) have changed */ 264 int (*attr_changed)(struct fscache_object *object); 265 266 /* reserve space for an object's data and associated metadata */ 267 int (*reserve_space)(struct fscache_object *object, loff_t i_size); 268 269 /* request a backing block for a page be read or allocated in the 270 * cache */ 271 fscache_page_retrieval_func_t read_or_alloc_page; 272 273 /* request backing blocks for a list of pages be read or allocated in 274 * the cache */ 275 fscache_pages_retrieval_func_t read_or_alloc_pages; 276 277 /* request a backing block for a page be allocated in the cache so that 278 * it can be written directly */ 279 fscache_page_retrieval_func_t allocate_page; 280 281 /* request backing blocks for pages be allocated in the cache so that 282 * they can be written directly */ 283 fscache_pages_retrieval_func_t allocate_pages; 284 285 /* write a page to its backing block in the cache */ 286 int (*write_page)(struct fscache_storage *op, struct page *page); 287 288 /* detach backing block from a page (optional) 289 * - must release the cookie lock before returning 290 * - may sleep 291 */ 292 void (*uncache_page)(struct fscache_object *object, 293 struct page *page); 294 295 /* dissociate a cache from all the pages it was backing */ 296 void (*dissociate_pages)(struct fscache_cache *cache); 297 }; 298 299 extern struct fscache_cookie fscache_fsdef_index; 300 301 /* 302 * Event list for fscache_object::{event_mask,events} 303 */ 304 enum { 305 FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */ 306 FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */ 307 FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */ 308 FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */ 309 FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */ 310 FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */ 311 FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */ 312 NR_FSCACHE_OBJECT_EVENTS 313 }; 314 315 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1) 316 317 /* 318 * States for object state machine. 319 */ 320 struct fscache_transition { 321 unsigned long events; 322 const struct fscache_state *transit_to; 323 }; 324 325 struct fscache_state { 326 char name[24]; 327 char short_name[8]; 328 const struct fscache_state *(*work)(struct fscache_object *object, 329 int event); 330 const struct fscache_transition transitions[]; 331 }; 332 333 /* 334 * on-disk cache file or index handle 335 */ 336 struct fscache_object { 337 const struct fscache_state *state; /* Object state machine state */ 338 const struct fscache_transition *oob_table; /* OOB state transition table */ 339 int debug_id; /* debugging ID */ 340 int n_children; /* number of child objects */ 341 int n_ops; /* number of extant ops on object */ 342 int n_obj_ops; /* number of object ops outstanding on object */ 343 int n_in_progress; /* number of ops in progress */ 344 int n_exclusive; /* number of exclusive ops queued or in progress */ 345 atomic_t n_reads; /* number of read ops in progress */ 346 spinlock_t lock; /* state and operations lock */ 347 348 unsigned long lookup_jif; /* time at which lookup started */ 349 unsigned long oob_event_mask; /* OOB events this object is interested in */ 350 unsigned long event_mask; /* events this object is interested in */ 351 unsigned long events; /* events to be processed by this object 352 * (order is important - using fls) */ 353 354 unsigned long flags; 355 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ 356 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ 357 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ 358 #define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */ 359 #define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */ 360 #define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */ 361 #define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */ 362 #define FSCACHE_OBJECT_KILLED_BY_CACHE 7 /* T if object was killed by the cache */ 363 #define FSCACHE_OBJECT_RUN_AFTER_DEAD 8 /* T if object has been dispatched after death */ 364 365 struct list_head cache_link; /* link in cache->object_list */ 366 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 367 struct fscache_cache *cache; /* cache that supplied this object */ 368 struct fscache_cookie *cookie; /* netfs's file/index object */ 369 struct fscache_object *parent; /* parent object */ 370 struct work_struct work; /* attention scheduling record */ 371 struct list_head dependents; /* FIFO of dependent objects */ 372 struct list_head dep_link; /* link in parent's dependents list */ 373 struct list_head pending_ops; /* unstarted operations on this object */ 374 #ifdef CONFIG_FSCACHE_OBJECT_LIST 375 struct rb_node objlist_link; /* link in global object list */ 376 #endif 377 pgoff_t store_limit; /* current storage limit */ 378 loff_t store_limit_l; /* current storage limit */ 379 }; 380 381 extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *, 382 struct fscache_cache *); 383 extern void fscache_object_destroy(struct fscache_object *); 384 385 extern void fscache_object_lookup_negative(struct fscache_object *object); 386 extern void fscache_obtained_object(struct fscache_object *object); 387 388 static inline bool fscache_object_is_live(struct fscache_object *object) 389 { 390 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); 391 } 392 393 static inline bool fscache_object_is_dying(struct fscache_object *object) 394 { 395 return !fscache_object_is_live(object); 396 } 397 398 static inline bool fscache_object_is_available(struct fscache_object *object) 399 { 400 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags); 401 } 402 403 static inline bool fscache_cache_is_broken(struct fscache_object *object) 404 { 405 return test_bit(FSCACHE_IOERROR, &object->cache->flags); 406 } 407 408 static inline bool fscache_object_is_active(struct fscache_object *object) 409 { 410 return fscache_object_is_available(object) && 411 fscache_object_is_live(object) && 412 !fscache_cache_is_broken(object); 413 } 414 415 /** 416 * fscache_object_destroyed - Note destruction of an object in a cache 417 * @cache: The cache from which the object came 418 * 419 * Note the destruction and deallocation of an object record in a cache. 420 */ 421 static inline void fscache_object_destroyed(struct fscache_cache *cache) 422 { 423 if (atomic_dec_and_test(&cache->object_count)) 424 wake_up_all(&fscache_cache_cleared_wq); 425 } 426 427 /** 428 * fscache_object_lookup_error - Note an object encountered an error 429 * @object: The object on which the error was encountered 430 * 431 * Note that an object encountered a fatal error (usually an I/O error) and 432 * that it should be withdrawn as soon as possible. 433 */ 434 static inline void fscache_object_lookup_error(struct fscache_object *object) 435 { 436 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 437 } 438 439 /** 440 * fscache_set_store_limit - Set the maximum size to be stored in an object 441 * @object: The object to set the maximum on 442 * @i_size: The limit to set in bytes 443 * 444 * Set the maximum size an object is permitted to reach, implying the highest 445 * byte that may be written. Intended to be called by the attr_changed() op. 446 * 447 * See Documentation/filesystems/caching/backend-api.txt for a complete 448 * description. 449 */ 450 static inline 451 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 452 { 453 object->store_limit_l = i_size; 454 object->store_limit = i_size >> PAGE_SHIFT; 455 if (i_size & ~PAGE_MASK) 456 object->store_limit++; 457 } 458 459 /** 460 * fscache_end_io - End a retrieval operation on a page 461 * @op: The FS-Cache operation covering the retrieval 462 * @page: The page that was to be fetched 463 * @error: The error code (0 if successful) 464 * 465 * Note the end of an operation to retrieve a page, as covered by a particular 466 * operation record. 467 */ 468 static inline void fscache_end_io(struct fscache_retrieval *op, 469 struct page *page, int error) 470 { 471 op->end_io_func(page, op->context, error); 472 } 473 474 static inline void __fscache_use_cookie(struct fscache_cookie *cookie) 475 { 476 atomic_inc(&cookie->n_active); 477 } 478 479 /** 480 * fscache_use_cookie - Request usage of cookie attached to an object 481 * @object: Object description 482 * 483 * Request usage of the cookie attached to an object. NULL is returned if the 484 * relinquishment had reduced the cookie usage count to 0. 485 */ 486 static inline bool fscache_use_cookie(struct fscache_object *object) 487 { 488 struct fscache_cookie *cookie = object->cookie; 489 return atomic_inc_not_zero(&cookie->n_active) != 0; 490 } 491 492 static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie) 493 { 494 return atomic_dec_and_test(&cookie->n_active); 495 } 496 497 static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie) 498 { 499 wake_up_atomic_t(&cookie->n_active); 500 } 501 502 /** 503 * fscache_unuse_cookie - Cease usage of cookie attached to an object 504 * @object: Object description 505 * 506 * Cease usage of the cookie attached to an object. When the users count 507 * reaches zero then the cookie relinquishment will be permitted to proceed. 508 */ 509 static inline void fscache_unuse_cookie(struct fscache_object *object) 510 { 511 struct fscache_cookie *cookie = object->cookie; 512 if (__fscache_unuse_cookie(cookie)) 513 __fscache_wake_unused_cookie(cookie); 514 } 515 516 /* 517 * out-of-line cache backend functions 518 */ 519 extern __printf(3, 4) 520 void fscache_init_cache(struct fscache_cache *cache, 521 const struct fscache_cache_ops *ops, 522 const char *idfmt, ...); 523 524 extern int fscache_add_cache(struct fscache_cache *cache, 525 struct fscache_object *fsdef, 526 const char *tagname); 527 extern void fscache_withdraw_cache(struct fscache_cache *cache); 528 529 extern void fscache_io_error(struct fscache_cache *cache); 530 531 extern void fscache_mark_page_cached(struct fscache_retrieval *op, 532 struct page *page); 533 534 extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 535 struct pagevec *pagevec); 536 537 extern bool fscache_object_sleep_till_congested(signed long *timeoutp); 538 539 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 540 const void *data, 541 uint16_t datalen); 542 543 extern void fscache_object_retrying_stale(struct fscache_object *object); 544 545 enum fscache_why_object_killed { 546 FSCACHE_OBJECT_IS_STALE, 547 FSCACHE_OBJECT_NO_SPACE, 548 FSCACHE_OBJECT_WAS_RETIRED, 549 FSCACHE_OBJECT_WAS_CULLED, 550 }; 551 extern void fscache_object_mark_killed(struct fscache_object *object, 552 enum fscache_why_object_killed why); 553 554 #endif /* _LINUX_FSCACHE_CACHE_H */ 555