1/* General filesystem caching backing cache interface 2 * 3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 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 27struct fscache_cache; 28struct fscache_cache_ops; 29struct fscache_object; 30struct fscache_operation; 31 32/* 33 * cache tag definition 34 */ 35struct 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 */ 47struct 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64#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ 65#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ 66}; 67 68extern wait_queue_head_t fscache_cache_cleared_wq; 69 70/* 71 * operation to be applied to a cache object 72 * - retrieval initiation operations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 */ 75typedef void (*fscache_operation_release_t)(struct fscache_operation *op); 76typedef void (*fscache_operation_processor_t)(struct fscache_operation *op); 77typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op); 78 79enum 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 89struct 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 120extern atomic_t fscache_op_debug_id; 121extern void fscache_op_work_func(struct work_struct *work); 122 123extern void fscache_enqueue_operation(struct fscache_operation *); 124extern void fscache_op_complete(struct fscache_operation *, bool); 125extern void fscache_put_operation(struct fscache_operation *); 126extern 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 */ 134struct 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 145typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, 146 struct page *page, 147 gfp_t gfp); 148 149typedef 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 */ 160static inline 161struct 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 */ 173static 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 */ 183static 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 */ 197static 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 */ 209struct 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 */ 217struct 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 bool (*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 299extern struct fscache_cookie fscache_fsdef_index; 300 301/* 302 * Event list for fscache_object::{event_mask,events} 303 */ 304enum { 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 */ 320struct fscache_transition { 321 unsigned long events; 322 const struct fscache_state *transit_to; 323}; 324 325struct 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 */ 336struct 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 */ 363 364 struct list_head cache_link; /* link in cache->object_list */ 365 struct hlist_node cookie_link; /* link in cookie->backing_objects */ 366 struct fscache_cache *cache; /* cache that supplied this object */ 367 struct fscache_cookie *cookie; /* netfs's file/index object */ 368 struct fscache_object *parent; /* parent object */ 369 struct work_struct work; /* attention scheduling record */ 370 struct list_head dependents; /* FIFO of dependent objects */ 371 struct list_head dep_link; /* link in parent's dependents list */ 372 struct list_head pending_ops; /* unstarted operations on this object */ 373#ifdef CONFIG_FSCACHE_OBJECT_LIST 374 struct rb_node objlist_link; /* link in global object list */ 375#endif 376 pgoff_t store_limit; /* current storage limit */ 377 loff_t store_limit_l; /* current storage limit */ 378}; 379 380extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *, 381 struct fscache_cache *); 382extern void fscache_object_destroy(struct fscache_object *); 383 384extern void fscache_object_lookup_negative(struct fscache_object *object); 385extern void fscache_obtained_object(struct fscache_object *object); 386 387static inline bool fscache_object_is_live(struct fscache_object *object) 388{ 389 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); 390} 391 392static inline bool fscache_object_is_dying(struct fscache_object *object) 393{ 394 return !fscache_object_is_live(object); 395} 396 397static inline bool fscache_object_is_available(struct fscache_object *object) 398{ 399 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags); 400} 401 402static inline bool fscache_cache_is_broken(struct fscache_object *object) 403{ 404 return test_bit(FSCACHE_IOERROR, &object->cache->flags); 405} 406 407static inline bool fscache_object_is_active(struct fscache_object *object) 408{ 409 return fscache_object_is_available(object) && 410 fscache_object_is_live(object) && 411 !fscache_cache_is_broken(object); 412} 413 414/** 415 * fscache_object_destroyed - Note destruction of an object in a cache 416 * @cache: The cache from which the object came 417 * 418 * Note the destruction and deallocation of an object record in a cache. 419 */ 420static inline void fscache_object_destroyed(struct fscache_cache *cache) 421{ 422 if (atomic_dec_and_test(&cache->object_count)) 423 wake_up_all(&fscache_cache_cleared_wq); 424} 425 426/** 427 * fscache_object_lookup_error - Note an object encountered an error 428 * @object: The object on which the error was encountered 429 * 430 * Note that an object encountered a fatal error (usually an I/O error) and 431 * that it should be withdrawn as soon as possible. 432 */ 433static inline void fscache_object_lookup_error(struct fscache_object *object) 434{ 435 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); 436} 437 438/** 439 * fscache_set_store_limit - Set the maximum size to be stored in an object 440 * @object: The object to set the maximum on 441 * @i_size: The limit to set in bytes 442 * 443 * Set the maximum size an object is permitted to reach, implying the highest 444 * byte that may be written. Intended to be called by the attr_changed() op. 445 * 446 * See Documentation/filesystems/caching/backend-api.txt for a complete 447 * description. 448 */ 449static inline 450void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) 451{ 452 object->store_limit_l = i_size; 453 object->store_limit = i_size >> PAGE_SHIFT; 454 if (i_size & ~PAGE_MASK) 455 object->store_limit++; 456} 457 458/** 459 * fscache_end_io - End a retrieval operation on a page 460 * @op: The FS-Cache operation covering the retrieval 461 * @page: The page that was to be fetched 462 * @error: The error code (0 if successful) 463 * 464 * Note the end of an operation to retrieve a page, as covered by a particular 465 * operation record. 466 */ 467static inline void fscache_end_io(struct fscache_retrieval *op, 468 struct page *page, int error) 469{ 470 op->end_io_func(page, op->context, error); 471} 472 473static inline void __fscache_use_cookie(struct fscache_cookie *cookie) 474{ 475 atomic_inc(&cookie->n_active); 476} 477 478/** 479 * fscache_use_cookie - Request usage of cookie attached to an object 480 * @object: Object description 481 * 482 * Request usage of the cookie attached to an object. NULL is returned if the 483 * relinquishment had reduced the cookie usage count to 0. 484 */ 485static inline bool fscache_use_cookie(struct fscache_object *object) 486{ 487 struct fscache_cookie *cookie = object->cookie; 488 return atomic_inc_not_zero(&cookie->n_active) != 0; 489} 490 491static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie) 492{ 493 return atomic_dec_and_test(&cookie->n_active); 494} 495 496static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie) 497{ 498 wake_up_atomic_t(&cookie->n_active); 499} 500 501/** 502 * fscache_unuse_cookie - Cease usage of cookie attached to an object 503 * @object: Object description 504 * 505 * Cease usage of the cookie attached to an object. When the users count 506 * reaches zero then the cookie relinquishment will be permitted to proceed. 507 */ 508static inline void fscache_unuse_cookie(struct fscache_object *object) 509{ 510 struct fscache_cookie *cookie = object->cookie; 511 if (__fscache_unuse_cookie(cookie)) 512 __fscache_wake_unused_cookie(cookie); 513} 514 515/* 516 * out-of-line cache backend functions 517 */ 518extern __printf(3, 4) 519void fscache_init_cache(struct fscache_cache *cache, 520 const struct fscache_cache_ops *ops, 521 const char *idfmt, ...); 522 523extern int fscache_add_cache(struct fscache_cache *cache, 524 struct fscache_object *fsdef, 525 const char *tagname); 526extern void fscache_withdraw_cache(struct fscache_cache *cache); 527 528extern void fscache_io_error(struct fscache_cache *cache); 529 530extern void fscache_mark_page_cached(struct fscache_retrieval *op, 531 struct page *page); 532 533extern void fscache_mark_pages_cached(struct fscache_retrieval *op, 534 struct pagevec *pagevec); 535 536extern bool fscache_object_sleep_till_congested(signed long *timeoutp); 537 538extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, 539 const void *data, 540 uint16_t datalen); 541 542extern void fscache_object_retrying_stale(struct fscache_object *object); 543 544enum fscache_why_object_killed { 545 FSCACHE_OBJECT_IS_STALE, 546 FSCACHE_OBJECT_NO_SPACE, 547 FSCACHE_OBJECT_WAS_RETIRED, 548 FSCACHE_OBJECT_WAS_CULLED, 549}; 550extern void fscache_object_mark_killed(struct fscache_object *object, 551 enum fscache_why_object_killed why); 552 553#endif /* _LINUX_FSCACHE_CACHE_H */ 554