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/slow-work.h>
24 #include <linux/workqueue.h>
26 #define NR_MAXCACHES BITS_PER_LONG
29 struct fscache_cache_ops;
30 struct fscache_object;
31 struct fscache_operation;
34 * cache tag definition
36 struct fscache_cache_tag {
37 struct list_head link;
38 struct fscache_cache *cache; /* cache referred to by this tag */
40 #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
42 char name[0]; /* tag name */
48 struct fscache_cache {
49 const struct fscache_cache_ops *ops;
50 struct fscache_cache_tag *tag; /* tag representing this cache */
51 struct kobject *kobj; /* system representation of this cache */
52 struct list_head link; /* link in list of caches */
53 size_t max_index_size; /* maximum size of index data */
54 char identifier[36]; /* cache label */
57 struct work_struct op_gc; /* operation garbage collector */
58 struct list_head object_list; /* list of data/index objects */
59 struct list_head op_gc_list; /* list of ops to be deleted */
60 spinlock_t object_list_lock;
61 spinlock_t op_gc_list_lock;
62 atomic_t object_count; /* no. of live objects in this cache */
63 struct fscache_object *fsdef; /* object for the fsdef index */
65 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
66 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
69 extern wait_queue_head_t fscache_cache_cleared_wq;
72 * operation to be applied to a cache object
73 * - retrieval initiation operations are done in the context of the process
74 * that issued them, and not in an async thread pool
76 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
77 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
79 struct fscache_operation {
81 struct work_struct fast_work; /* record for fast ops */
82 struct slow_work slow_work; /* record for (very) slow ops */
84 struct list_head pend_link; /* link in object->pending_ops */
85 struct fscache_object *object; /* object to be operated upon */
88 #define FSCACHE_OP_TYPE 0x000f /* operation type */
89 #define FSCACHE_OP_FAST 0x0001 /* - fast op, processor may not sleep for disk */
90 #define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */
91 #define FSCACHE_OP_MYTHREAD 0x0003 /* - processing is done be issuing thread, not pool */
92 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
93 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
94 #define FSCACHE_OP_DEAD 6 /* op is now dead */
95 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */
96 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */
99 unsigned debug_id; /* debugging ID */
101 /* operation processor callback
102 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
103 * the op in a non-pool thread */
104 fscache_operation_processor_t processor;
106 /* operation releaser */
107 fscache_operation_release_t release;
109 #ifdef CONFIG_SLOW_WORK_DEBUG
110 const char *name; /* operation name */
111 const char *state; /* operation state */
112 #define fscache_set_op_name(OP, N) do { (OP)->name = (N); } while(0)
113 #define fscache_set_op_state(OP, S) do { (OP)->state = (S); } while(0)
115 #define fscache_set_op_name(OP, N) do { } while(0)
116 #define fscache_set_op_state(OP, S) do { } while(0)
120 extern atomic_t fscache_op_debug_id;
121 extern const struct slow_work_ops fscache_op_slow_work_ops;
123 extern void fscache_enqueue_operation(struct fscache_operation *);
124 extern void fscache_put_operation(struct fscache_operation *);
127 * fscache_operation_init - Do basic initialisation of an operation
128 * @op: The operation to initialise
129 * @release: The release function to assign
131 * Do basic initialisation of an operation. The caller must still set flags,
132 * object, either fast_work or slow_work if necessary, and processor if needed.
134 static inline void fscache_operation_init(struct fscache_operation *op,
135 fscache_operation_release_t release)
137 atomic_set(&op->usage, 1);
138 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
139 op->release = release;
140 INIT_LIST_HEAD(&op->pend_link);
141 fscache_set_op_state(op, "Init");
145 * fscache_operation_init_slow - Do additional initialisation of a slow op
146 * @op: The operation to initialise
147 * @processor: The processor function to assign
149 * Do additional initialisation of an operation as required for slow work.
152 void fscache_operation_init_slow(struct fscache_operation *op,
153 fscache_operation_processor_t processor)
155 op->processor = processor;
156 slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
160 * data read operation
162 struct fscache_retrieval {
163 struct fscache_operation op;
164 struct address_space *mapping; /* netfs pages */
165 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
166 void *context; /* netfs read context (pinned) */
167 struct list_head to_do; /* list of things to be done by the backend */
168 unsigned long start_time; /* time at which retrieval started */
171 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
175 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
176 struct list_head *pages,
181 * fscache_get_retrieval - Get an extra reference on a retrieval operation
182 * @op: The retrieval operation to get a reference on
184 * Get an extra reference on a retrieval operation.
187 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
189 atomic_inc(&op->op.usage);
194 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
195 * @op: The retrieval operation affected
197 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
199 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
201 fscache_enqueue_operation(&op->op);
205 * fscache_put_retrieval - Drop a reference to a retrieval operation
206 * @op: The retrieval operation affected
208 * Drop a reference to a retrieval operation.
210 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
212 fscache_put_operation(&op->op);
216 * cached page storage work item
217 * - used to do three things:
218 * - batch writes to the cache
219 * - do cache writes asynchronously
220 * - defer writes until cache object lookup completion
222 struct fscache_storage {
223 struct fscache_operation op;
224 pgoff_t store_limit; /* don't write more than this */
230 struct fscache_cache_ops {
231 /* name of cache provider */
234 /* allocate an object record for a cookie */
235 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
236 struct fscache_cookie *cookie);
238 /* look up the object for a cookie
239 * - return -ETIMEDOUT to be requeued
241 int (*lookup_object)(struct fscache_object *object);
243 /* finished looking up */
244 void (*lookup_complete)(struct fscache_object *object);
246 /* increment the usage count on this object (may fail if unmounting) */
247 struct fscache_object *(*grab_object)(struct fscache_object *object);
249 /* pin an object in the cache */
250 int (*pin_object)(struct fscache_object *object);
252 /* unpin an object in the cache */
253 void (*unpin_object)(struct fscache_object *object);
255 /* store the updated auxilliary data on an object */
256 void (*update_object)(struct fscache_object *object);
258 /* discard the resources pinned by an object and effect retirement if
260 void (*drop_object)(struct fscache_object *object);
262 /* dispose of a reference to an object */
263 void (*put_object)(struct fscache_object *object);
266 void (*sync_cache)(struct fscache_cache *cache);
268 /* notification that the attributes of a non-index object (such as
269 * i_size) have changed */
270 int (*attr_changed)(struct fscache_object *object);
272 /* reserve space for an object's data and associated metadata */
273 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
275 /* request a backing block for a page be read or allocated in the
277 fscache_page_retrieval_func_t read_or_alloc_page;
279 /* request backing blocks for a list of pages be read or allocated in
281 fscache_pages_retrieval_func_t read_or_alloc_pages;
283 /* request a backing block for a page be allocated in the cache so that
284 * it can be written directly */
285 fscache_page_retrieval_func_t allocate_page;
287 /* request backing blocks for pages be allocated in the cache so that
288 * they can be written directly */
289 fscache_pages_retrieval_func_t allocate_pages;
291 /* write a page to its backing block in the cache */
292 int (*write_page)(struct fscache_storage *op, struct page *page);
294 /* detach backing block from a page (optional)
295 * - must release the cookie lock before returning
298 void (*uncache_page)(struct fscache_object *object,
301 /* dissociate a cache from all the pages it was backing */
302 void (*dissociate_pages)(struct fscache_cache *cache);
306 * data file or index object cookie
307 * - a file will only appear in one cache
308 * - a request to cache a file may or may not be honoured, subject to
309 * constraints such as disk space
310 * - indices are created on disk just-in-time
312 struct fscache_cookie {
313 atomic_t usage; /* number of users of this cookie */
314 atomic_t n_children; /* number of children of this cookie */
316 spinlock_t stores_lock; /* lock on page store tree */
317 struct hlist_head backing_objects; /* object(s) backing this file/index */
318 const struct fscache_cookie_def *def; /* definition */
319 struct fscache_cookie *parent; /* parent of this entry */
320 void *netfs_data; /* back pointer to netfs */
321 struct radix_tree_root stores; /* pages to be stored on this cookie */
322 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
323 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
326 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
327 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
328 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
329 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
330 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
331 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
334 extern struct fscache_cookie fscache_fsdef_index;
337 * on-disk cache file or index handle
339 struct fscache_object {
340 enum fscache_object_state {
341 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
342 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
343 FSCACHE_OBJECT_CREATING, /* creating object */
346 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
347 FSCACHE_OBJECT_ACTIVE, /* object is usable */
348 FSCACHE_OBJECT_UPDATING, /* object is updating */
350 /* terminal states */
351 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
352 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
353 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
354 FSCACHE_OBJECT_RELEASING, /* releasing object */
355 FSCACHE_OBJECT_RECYCLING, /* retiring object */
356 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
357 FSCACHE_OBJECT_DEAD, /* object is now dead */
358 FSCACHE_OBJECT__NSTATES
361 int debug_id; /* debugging ID */
362 int n_children; /* number of child objects */
363 int n_ops; /* number of ops outstanding on object */
364 int n_obj_ops; /* number of object ops outstanding on object */
365 int n_in_progress; /* number of ops in progress */
366 int n_exclusive; /* number of exclusive ops queued */
367 atomic_t n_reads; /* number of read ops in progress */
368 spinlock_t lock; /* state and operations lock */
370 unsigned long lookup_jif; /* time at which lookup started */
371 unsigned long event_mask; /* events this object is interested in */
372 unsigned long events; /* events to be processed by this object
373 * (order is important - using fls) */
374 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
375 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
376 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
377 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
378 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
379 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
380 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
381 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
384 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
385 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
386 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
388 struct list_head cache_link; /* link in cache->object_list */
389 struct hlist_node cookie_link; /* link in cookie->backing_objects */
390 struct fscache_cache *cache; /* cache that supplied this object */
391 struct fscache_cookie *cookie; /* netfs's file/index object */
392 struct fscache_object *parent; /* parent object */
393 struct work_struct work; /* attention scheduling record */
394 struct list_head dependents; /* FIFO of dependent objects */
395 struct list_head dep_link; /* link in parent's dependents list */
396 struct list_head pending_ops; /* unstarted operations on this object */
397 #ifdef CONFIG_FSCACHE_OBJECT_LIST
398 struct rb_node objlist_link; /* link in global object list */
400 pgoff_t store_limit; /* current storage limit */
401 loff_t store_limit_l; /* current storage limit */
404 extern const char *fscache_object_states[];
406 #define fscache_object_is_active(obj) \
407 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
408 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
409 (obj)->state < FSCACHE_OBJECT_DYING)
411 #define fscache_object_is_dead(obj) \
412 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
413 (obj)->state >= FSCACHE_OBJECT_DYING)
415 extern void fscache_object_work_func(struct work_struct *work);
418 * fscache_object_init - Initialise a cache object description
419 * @object: Object description
421 * Initialise a cache object description to its basic values.
423 * See Documentation/filesystems/caching/backend-api.txt for a complete
427 void fscache_object_init(struct fscache_object *object,
428 struct fscache_cookie *cookie,
429 struct fscache_cache *cache)
431 atomic_inc(&cache->object_count);
433 object->state = FSCACHE_OBJECT_INIT;
434 spin_lock_init(&object->lock);
435 INIT_LIST_HEAD(&object->cache_link);
436 INIT_HLIST_NODE(&object->cookie_link);
437 INIT_WORK(&object->work, fscache_object_work_func);
438 INIT_LIST_HEAD(&object->dependents);
439 INIT_LIST_HEAD(&object->dep_link);
440 INIT_LIST_HEAD(&object->pending_ops);
441 object->n_children = 0;
442 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
443 object->events = object->event_mask = 0;
445 object->store_limit = 0;
446 object->store_limit_l = 0;
447 object->cache = cache;
448 object->cookie = cookie;
449 object->parent = NULL;
452 extern void fscache_object_lookup_negative(struct fscache_object *object);
453 extern void fscache_obtained_object(struct fscache_object *object);
455 #ifdef CONFIG_FSCACHE_OBJECT_LIST
456 extern void fscache_object_destroy(struct fscache_object *object);
458 #define fscache_object_destroy(object) do {} while(0)
462 * fscache_object_destroyed - Note destruction of an object in a cache
463 * @cache: The cache from which the object came
465 * Note the destruction and deallocation of an object record in a cache.
467 static inline void fscache_object_destroyed(struct fscache_cache *cache)
469 if (atomic_dec_and_test(&cache->object_count))
470 wake_up_all(&fscache_cache_cleared_wq);
474 * fscache_object_lookup_error - Note an object encountered an error
475 * @object: The object on which the error was encountered
477 * Note that an object encountered a fatal error (usually an I/O error) and
478 * that it should be withdrawn as soon as possible.
480 static inline void fscache_object_lookup_error(struct fscache_object *object)
482 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
486 * fscache_set_store_limit - Set the maximum size to be stored in an object
487 * @object: The object to set the maximum on
488 * @i_size: The limit to set in bytes
490 * Set the maximum size an object is permitted to reach, implying the highest
491 * byte that may be written. Intended to be called by the attr_changed() op.
493 * See Documentation/filesystems/caching/backend-api.txt for a complete
497 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
499 object->store_limit_l = i_size;
500 object->store_limit = i_size >> PAGE_SHIFT;
501 if (i_size & ~PAGE_MASK)
502 object->store_limit++;
506 * fscache_end_io - End a retrieval operation on a page
507 * @op: The FS-Cache operation covering the retrieval
508 * @page: The page that was to be fetched
509 * @error: The error code (0 if successful)
511 * Note the end of an operation to retrieve a page, as covered by a particular
514 static inline void fscache_end_io(struct fscache_retrieval *op,
515 struct page *page, int error)
517 op->end_io_func(page, op->context, error);
521 * out-of-line cache backend functions
523 extern void fscache_init_cache(struct fscache_cache *cache,
524 const struct fscache_cache_ops *ops,
526 ...) __attribute__ ((format (printf, 3, 4)));
528 extern int fscache_add_cache(struct fscache_cache *cache,
529 struct fscache_object *fsdef,
530 const char *tagname);
531 extern void fscache_withdraw_cache(struct fscache_cache *cache);
533 extern void fscache_io_error(struct fscache_cache *cache);
535 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
536 struct pagevec *pagevec);
538 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
540 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
544 #endif /* _LINUX_FSCACHE_CACHE_H */