1 /* General filesystem caching backing cache interface
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
13 * Documentation/filesystems/caching/backend-api.txt
15 * for a description of the cache backend interface declared here.
18 #ifndef _LINUX_FSCACHE_CACHE_H
19 #define _LINUX_FSCACHE_CACHE_H
21 #include <linux/fscache.h>
22 #include <linux/sched.h>
23 #include <linux/workqueue.h>
25 #define NR_MAXCACHES BITS_PER_LONG
28 struct fscache_cache_ops;
29 struct fscache_object;
30 struct fscache_operation;
33 * cache tag definition
35 struct fscache_cache_tag {
36 struct list_head link;
37 struct fscache_cache *cache; /* cache referred to by this tag */
39 #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
41 char name[0]; /* tag name */
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 */
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 */
64 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
68 extern wait_queue_head_t fscache_cache_cleared_wq;
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
75 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
76 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
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 */
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 */
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 */
103 enum fscache_operation_state state;
105 unsigned debug_id; /* debugging ID */
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;
112 /* operation releaser */
113 fscache_operation_release_t release;
116 extern atomic_t fscache_op_debug_id;
117 extern void fscache_op_work_func(struct work_struct *work);
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 extern void fscache_operation_init(struct fscache_operation *,
123 fscache_operation_processor_t,
124 fscache_operation_release_t);
127 * data read operation
129 struct fscache_retrieval {
130 struct fscache_operation op;
131 struct address_space *mapping; /* netfs pages */
132 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
133 void *context; /* netfs read context (pinned) */
134 struct list_head to_do; /* list of things to be done by the backend */
135 unsigned long start_time; /* time at which retrieval started */
136 atomic_t n_pages; /* number of pages to be retrieved */
139 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
143 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
144 struct list_head *pages,
149 * fscache_get_retrieval - Get an extra reference on a retrieval operation
150 * @op: The retrieval operation to get a reference on
152 * Get an extra reference on a retrieval operation.
155 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
157 atomic_inc(&op->op.usage);
162 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
163 * @op: The retrieval operation affected
165 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
167 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
169 fscache_enqueue_operation(&op->op);
173 * fscache_retrieval_complete - Record (partial) completion of a retrieval
174 * @op: The retrieval operation affected
175 * @n_pages: The number of pages to account for
177 static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
180 atomic_sub(n_pages, &op->n_pages);
181 if (atomic_read(&op->n_pages) <= 0)
182 fscache_op_complete(&op->op, true);
186 * fscache_put_retrieval - Drop a reference to a retrieval operation
187 * @op: The retrieval operation affected
189 * Drop a reference to a retrieval operation.
191 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
193 fscache_put_operation(&op->op);
197 * cached page storage work item
198 * - used to do three things:
199 * - batch writes to the cache
200 * - do cache writes asynchronously
201 * - defer writes until cache object lookup completion
203 struct fscache_storage {
204 struct fscache_operation op;
205 pgoff_t store_limit; /* don't write more than this */
211 struct fscache_cache_ops {
212 /* name of cache provider */
215 /* allocate an object record for a cookie */
216 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
217 struct fscache_cookie *cookie);
219 /* look up the object for a cookie
220 * - return -ETIMEDOUT to be requeued
222 int (*lookup_object)(struct fscache_object *object);
224 /* finished looking up */
225 void (*lookup_complete)(struct fscache_object *object);
227 /* increment the usage count on this object (may fail if unmounting) */
228 struct fscache_object *(*grab_object)(struct fscache_object *object);
230 /* pin an object in the cache */
231 int (*pin_object)(struct fscache_object *object);
233 /* unpin an object in the cache */
234 void (*unpin_object)(struct fscache_object *object);
236 /* check the consistency between the backing cache and the FS-Cache
238 bool (*check_consistency)(struct fscache_operation *op);
240 /* store the updated auxiliary data on an object */
241 void (*update_object)(struct fscache_object *object);
243 /* Invalidate an object */
244 void (*invalidate_object)(struct fscache_operation *op);
246 /* discard the resources pinned by an object and effect retirement if
248 void (*drop_object)(struct fscache_object *object);
250 /* dispose of a reference to an object */
251 void (*put_object)(struct fscache_object *object);
254 void (*sync_cache)(struct fscache_cache *cache);
256 /* notification that the attributes of a non-index object (such as
257 * i_size) have changed */
258 int (*attr_changed)(struct fscache_object *object);
260 /* reserve space for an object's data and associated metadata */
261 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
263 /* request a backing block for a page be read or allocated in the
265 fscache_page_retrieval_func_t read_or_alloc_page;
267 /* request backing blocks for a list of pages be read or allocated in
269 fscache_pages_retrieval_func_t read_or_alloc_pages;
271 /* request a backing block for a page be allocated in the cache so that
272 * it can be written directly */
273 fscache_page_retrieval_func_t allocate_page;
275 /* request backing blocks for pages be allocated in the cache so that
276 * they can be written directly */
277 fscache_pages_retrieval_func_t allocate_pages;
279 /* write a page to its backing block in the cache */
280 int (*write_page)(struct fscache_storage *op, struct page *page);
282 /* detach backing block from a page (optional)
283 * - must release the cookie lock before returning
286 void (*uncache_page)(struct fscache_object *object,
289 /* dissociate a cache from all the pages it was backing */
290 void (*dissociate_pages)(struct fscache_cache *cache);
293 extern struct fscache_cookie fscache_fsdef_index;
296 * Event list for fscache_object::{event_mask,events}
299 FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */
300 FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
301 FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */
302 FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */
303 FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */
304 FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */
305 FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */
306 NR_FSCACHE_OBJECT_EVENTS
309 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
312 * States for object state machine.
314 struct fscache_transition {
315 unsigned long events;
316 const struct fscache_state *transit_to;
319 struct fscache_state {
322 const struct fscache_state *(*work)(struct fscache_object *object,
324 const struct fscache_transition transitions[];
328 * on-disk cache file or index handle
330 struct fscache_object {
331 const struct fscache_state *state; /* Object state machine state */
332 const struct fscache_transition *oob_table; /* OOB state transition table */
333 int debug_id; /* debugging ID */
334 int n_children; /* number of child objects */
335 int n_ops; /* number of extant ops 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 or in progress */
339 atomic_t n_reads; /* number of read ops in progress */
340 spinlock_t lock; /* state and operations lock */
342 unsigned long lookup_jif; /* time at which lookup started */
343 unsigned long oob_event_mask; /* OOB events this object is interested in */
344 unsigned long event_mask; /* events this object is interested in */
345 unsigned long events; /* events to be processed by this object
346 * (order is important - using fls) */
349 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
350 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
351 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
352 #define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
353 #define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
354 #define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
355 #define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */
356 #define FSCACHE_OBJECT_KILLED_BY_CACHE 7 /* T if object was killed by the cache */
358 struct list_head cache_link; /* link in cache->object_list */
359 struct hlist_node cookie_link; /* link in cookie->backing_objects */
360 struct fscache_cache *cache; /* cache that supplied this object */
361 struct fscache_cookie *cookie; /* netfs's file/index object */
362 struct fscache_object *parent; /* parent object */
363 struct work_struct work; /* attention scheduling record */
364 struct list_head dependents; /* FIFO of dependent objects */
365 struct list_head dep_link; /* link in parent's dependents list */
366 struct list_head pending_ops; /* unstarted operations on this object */
367 #ifdef CONFIG_FSCACHE_OBJECT_LIST
368 struct rb_node objlist_link; /* link in global object list */
370 pgoff_t store_limit; /* current storage limit */
371 loff_t store_limit_l; /* current storage limit */
374 extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
375 struct fscache_cache *);
376 extern void fscache_object_destroy(struct fscache_object *);
378 extern void fscache_object_lookup_negative(struct fscache_object *object);
379 extern void fscache_obtained_object(struct fscache_object *object);
381 static inline bool fscache_object_is_live(struct fscache_object *object)
383 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
386 static inline bool fscache_object_is_dying(struct fscache_object *object)
388 return !fscache_object_is_live(object);
391 static inline bool fscache_object_is_available(struct fscache_object *object)
393 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
396 static inline bool fscache_cache_is_broken(struct fscache_object *object)
398 return test_bit(FSCACHE_IOERROR, &object->cache->flags);
401 static inline bool fscache_object_is_active(struct fscache_object *object)
403 return fscache_object_is_available(object) &&
404 fscache_object_is_live(object) &&
405 !fscache_cache_is_broken(object);
409 * fscache_object_destroyed - Note destruction of an object in a cache
410 * @cache: The cache from which the object came
412 * Note the destruction and deallocation of an object record in a cache.
414 static inline void fscache_object_destroyed(struct fscache_cache *cache)
416 if (atomic_dec_and_test(&cache->object_count))
417 wake_up_all(&fscache_cache_cleared_wq);
421 * fscache_object_lookup_error - Note an object encountered an error
422 * @object: The object on which the error was encountered
424 * Note that an object encountered a fatal error (usually an I/O error) and
425 * that it should be withdrawn as soon as possible.
427 static inline void fscache_object_lookup_error(struct fscache_object *object)
429 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
433 * fscache_set_store_limit - Set the maximum size to be stored in an object
434 * @object: The object to set the maximum on
435 * @i_size: The limit to set in bytes
437 * Set the maximum size an object is permitted to reach, implying the highest
438 * byte that may be written. Intended to be called by the attr_changed() op.
440 * See Documentation/filesystems/caching/backend-api.txt for a complete
444 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
446 object->store_limit_l = i_size;
447 object->store_limit = i_size >> PAGE_SHIFT;
448 if (i_size & ~PAGE_MASK)
449 object->store_limit++;
453 * fscache_end_io - End a retrieval operation on a page
454 * @op: The FS-Cache operation covering the retrieval
455 * @page: The page that was to be fetched
456 * @error: The error code (0 if successful)
458 * Note the end of an operation to retrieve a page, as covered by a particular
461 static inline void fscache_end_io(struct fscache_retrieval *op,
462 struct page *page, int error)
464 op->end_io_func(page, op->context, error);
467 static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
469 atomic_inc(&cookie->n_active);
473 * fscache_use_cookie - Request usage of cookie attached to an object
474 * @object: Object description
476 * Request usage of the cookie attached to an object. NULL is returned if the
477 * relinquishment had reduced the cookie usage count to 0.
479 static inline bool fscache_use_cookie(struct fscache_object *object)
481 struct fscache_cookie *cookie = object->cookie;
482 return atomic_inc_not_zero(&cookie->n_active) != 0;
485 static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
487 return atomic_dec_and_test(&cookie->n_active);
490 static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
492 wake_up_atomic_t(&cookie->n_active);
496 * fscache_unuse_cookie - Cease usage of cookie attached to an object
497 * @object: Object description
499 * Cease usage of the cookie attached to an object. When the users count
500 * reaches zero then the cookie relinquishment will be permitted to proceed.
502 static inline void fscache_unuse_cookie(struct fscache_object *object)
504 struct fscache_cookie *cookie = object->cookie;
505 if (__fscache_unuse_cookie(cookie))
506 __fscache_wake_unused_cookie(cookie);
510 * out-of-line cache backend functions
512 extern __printf(3, 4)
513 void fscache_init_cache(struct fscache_cache *cache,
514 const struct fscache_cache_ops *ops,
515 const char *idfmt, ...);
517 extern int fscache_add_cache(struct fscache_cache *cache,
518 struct fscache_object *fsdef,
519 const char *tagname);
520 extern void fscache_withdraw_cache(struct fscache_cache *cache);
522 extern void fscache_io_error(struct fscache_cache *cache);
524 extern void fscache_mark_page_cached(struct fscache_retrieval *op,
527 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
528 struct pagevec *pagevec);
530 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
532 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
536 extern void fscache_object_retrying_stale(struct fscache_object *object);
538 enum fscache_why_object_killed {
539 FSCACHE_OBJECT_IS_STALE,
540 FSCACHE_OBJECT_NO_SPACE,
541 FSCACHE_OBJECT_WAS_RETIRED,
542 FSCACHE_OBJECT_WAS_CULLED,
544 extern void fscache_object_mark_killed(struct fscache_object *object,
545 enum fscache_why_object_killed why);
547 #endif /* _LINUX_FSCACHE_CACHE_H */