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66 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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 {
80 struct work_struct work; /* record for async ops */
81 struct list_head pend_link; /* link in object->pending_ops */
82 struct fscache_object *object; /* object to be operated upon */
85 #define FSCACHE_OP_TYPE 0x000f /* operation type */
86 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
87 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
88 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
89 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
90 #define FSCACHE_OP_DEAD 6 /* op is now dead */
91 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */
92 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */
95 unsigned debug_id; /* debugging ID */
97 /* operation processor callback
98 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
99 * the op in a non-pool thread */
100 fscache_operation_processor_t processor;
102 /* operation releaser */
103 fscache_operation_release_t release;
105 #ifdef CONFIG_WORKQUEUE_DEBUGFS
106 struct work_struct put_work; /* work to delay operation put */
107 const char *name; /* operation name */
108 const char *state; /* operation state */
109 #define fscache_set_op_name(OP, N) do { (OP)->name = (N); } while(0)
110 #define fscache_set_op_state(OP, S) do { (OP)->state = (S); } while(0)
112 #define fscache_set_op_name(OP, N) do { } while(0)
113 #define fscache_set_op_state(OP, S) do { } while(0)
117 extern atomic_t fscache_op_debug_id;
118 extern void fscache_op_work_func(struct work_struct *work);
120 extern void fscache_enqueue_operation(struct fscache_operation *);
121 extern void fscache_put_operation(struct fscache_operation *);
124 * fscache_operation_init - Do basic initialisation of an operation
125 * @op: The operation to initialise
126 * @release: The release function to assign
128 * Do basic initialisation of an operation. The caller must still set flags,
129 * object and processor if needed.
131 static inline void fscache_operation_init(struct fscache_operation *op,
132 fscache_operation_processor_t processor,
133 fscache_operation_release_t release)
135 INIT_WORK(&op->work, fscache_op_work_func);
136 atomic_set(&op->usage, 1);
137 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
138 op->processor = processor;
139 op->release = release;
140 INIT_LIST_HEAD(&op->pend_link);
141 fscache_set_op_state(op, "Init");
145 * data read operation
147 struct fscache_retrieval {
148 struct fscache_operation op;
149 struct address_space *mapping; /* netfs pages */
150 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
151 void *context; /* netfs read context (pinned) */
152 struct list_head to_do; /* list of things to be done by the backend */
153 unsigned long start_time; /* time at which retrieval started */
156 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
160 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
161 struct list_head *pages,
166 * fscache_get_retrieval - Get an extra reference on a retrieval operation
167 * @op: The retrieval operation to get a reference on
169 * Get an extra reference on a retrieval operation.
172 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
174 atomic_inc(&op->op.usage);
179 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
180 * @op: The retrieval operation affected
182 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
184 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
186 fscache_enqueue_operation(&op->op);
190 * fscache_put_retrieval - Drop a reference to a retrieval operation
191 * @op: The retrieval operation affected
193 * Drop a reference to a retrieval operation.
195 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
197 fscache_put_operation(&op->op);
201 * cached page storage work item
202 * - used to do three things:
203 * - batch writes to the cache
204 * - do cache writes asynchronously
205 * - defer writes until cache object lookup completion
207 struct fscache_storage {
208 struct fscache_operation op;
209 pgoff_t store_limit; /* don't write more than this */
215 struct fscache_cache_ops {
216 /* name of cache provider */
219 /* allocate an object record for a cookie */
220 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
221 struct fscache_cookie *cookie);
223 /* look up the object for a cookie
224 * - return -ETIMEDOUT to be requeued
226 int (*lookup_object)(struct fscache_object *object);
228 /* finished looking up */
229 void (*lookup_complete)(struct fscache_object *object);
231 /* increment the usage count on this object (may fail if unmounting) */
232 struct fscache_object *(*grab_object)(struct fscache_object *object);
234 /* pin an object in the cache */
235 int (*pin_object)(struct fscache_object *object);
237 /* unpin an object in the cache */
238 void (*unpin_object)(struct fscache_object *object);
240 /* store the updated auxilliary data on an object */
241 void (*update_object)(struct fscache_object *object);
243 /* discard the resources pinned by an object and effect retirement if
245 void (*drop_object)(struct fscache_object *object);
247 /* dispose of a reference to an object */
248 void (*put_object)(struct fscache_object *object);
251 void (*sync_cache)(struct fscache_cache *cache);
253 /* notification that the attributes of a non-index object (such as
254 * i_size) have changed */
255 int (*attr_changed)(struct fscache_object *object);
257 /* reserve space for an object's data and associated metadata */
258 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
260 /* request a backing block for a page be read or allocated in the
262 fscache_page_retrieval_func_t read_or_alloc_page;
264 /* request backing blocks for a list of pages be read or allocated in
266 fscache_pages_retrieval_func_t read_or_alloc_pages;
268 /* request a backing block for a page be allocated in the cache so that
269 * it can be written directly */
270 fscache_page_retrieval_func_t allocate_page;
272 /* request backing blocks for pages be allocated in the cache so that
273 * they can be written directly */
274 fscache_pages_retrieval_func_t allocate_pages;
276 /* write a page to its backing block in the cache */
277 int (*write_page)(struct fscache_storage *op, struct page *page);
279 /* detach backing block from a page (optional)
280 * - must release the cookie lock before returning
283 void (*uncache_page)(struct fscache_object *object,
286 /* dissociate a cache from all the pages it was backing */
287 void (*dissociate_pages)(struct fscache_cache *cache);
291 * data file or index object cookie
292 * - a file will only appear in one cache
293 * - a request to cache a file may or may not be honoured, subject to
294 * constraints such as disk space
295 * - indices are created on disk just-in-time
297 struct fscache_cookie {
298 atomic_t usage; /* number of users of this cookie */
299 atomic_t n_children; /* number of children of this cookie */
301 spinlock_t stores_lock; /* lock on page store tree */
302 struct hlist_head backing_objects; /* object(s) backing this file/index */
303 const struct fscache_cookie_def *def; /* definition */
304 struct fscache_cookie *parent; /* parent of this entry */
305 void *netfs_data; /* back pointer to netfs */
306 struct radix_tree_root stores; /* pages to be stored on this cookie */
307 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
308 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
311 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
312 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
313 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
314 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
315 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
316 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
319 extern struct fscache_cookie fscache_fsdef_index;
322 * on-disk cache file or index handle
324 struct fscache_object {
325 enum fscache_object_state {
326 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
327 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
328 FSCACHE_OBJECT_CREATING, /* creating object */
331 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
332 FSCACHE_OBJECT_ACTIVE, /* object is usable */
333 FSCACHE_OBJECT_UPDATING, /* object is updating */
335 /* terminal states */
336 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
337 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
338 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
339 FSCACHE_OBJECT_RELEASING, /* releasing object */
340 FSCACHE_OBJECT_RECYCLING, /* retiring object */
341 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
342 FSCACHE_OBJECT_DEAD, /* object is now dead */
343 FSCACHE_OBJECT__NSTATES
346 int debug_id; /* debugging ID */
347 int n_children; /* number of child objects */
348 int n_ops; /* number of ops outstanding on object */
349 int n_obj_ops; /* number of object ops outstanding on object */
350 int n_in_progress; /* number of ops in progress */
351 int n_exclusive; /* number of exclusive ops queued */
352 atomic_t n_reads; /* number of read ops in progress */
353 spinlock_t lock; /* state and operations lock */
355 unsigned long lookup_jif; /* time at which lookup started */
356 unsigned long event_mask; /* events this object is interested in */
357 unsigned long events; /* events to be processed by this object
358 * (order is important - using fls) */
359 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
360 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
361 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
362 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
363 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
364 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
365 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
366 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
369 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
370 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
371 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
373 struct list_head cache_link; /* link in cache->object_list */
374 struct hlist_node cookie_link; /* link in cookie->backing_objects */
375 struct fscache_cache *cache; /* cache that supplied this object */
376 struct fscache_cookie *cookie; /* netfs's file/index object */
377 struct fscache_object *parent; /* parent object */
378 struct work_struct work; /* attention scheduling record */
379 struct list_head dependents; /* FIFO of dependent objects */
380 struct list_head dep_link; /* link in parent's dependents list */
381 struct list_head pending_ops; /* unstarted operations on this object */
382 #ifdef CONFIG_FSCACHE_OBJECT_LIST
383 struct rb_node objlist_link; /* link in global object list */
385 pgoff_t store_limit; /* current storage limit */
386 loff_t store_limit_l; /* current storage limit */
389 extern const char *fscache_object_states[];
391 #define fscache_object_is_active(obj) \
392 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
393 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
394 (obj)->state < FSCACHE_OBJECT_DYING)
396 #define fscache_object_is_dead(obj) \
397 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
398 (obj)->state >= FSCACHE_OBJECT_DYING)
400 extern void fscache_object_work_func(struct work_struct *work);
403 * fscache_object_init - Initialise a cache object description
404 * @object: Object description
406 * Initialise a cache object description to its basic values.
408 * See Documentation/filesystems/caching/backend-api.txt for a complete
412 void fscache_object_init(struct fscache_object *object,
413 struct fscache_cookie *cookie,
414 struct fscache_cache *cache)
416 atomic_inc(&cache->object_count);
418 object->state = FSCACHE_OBJECT_INIT;
419 spin_lock_init(&object->lock);
420 INIT_LIST_HEAD(&object->cache_link);
421 INIT_HLIST_NODE(&object->cookie_link);
422 INIT_WORK(&object->work, fscache_object_work_func);
423 INIT_LIST_HEAD(&object->dependents);
424 INIT_LIST_HEAD(&object->dep_link);
425 INIT_LIST_HEAD(&object->pending_ops);
426 object->n_children = 0;
427 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
428 object->events = object->event_mask = 0;
430 object->store_limit = 0;
431 object->store_limit_l = 0;
432 object->cache = cache;
433 object->cookie = cookie;
434 object->parent = NULL;
437 extern void fscache_object_lookup_negative(struct fscache_object *object);
438 extern void fscache_obtained_object(struct fscache_object *object);
440 #ifdef CONFIG_FSCACHE_OBJECT_LIST
441 extern void fscache_object_destroy(struct fscache_object *object);
443 #define fscache_object_destroy(object) do {} while(0)
447 * fscache_object_destroyed - Note destruction of an object in a cache
448 * @cache: The cache from which the object came
450 * Note the destruction and deallocation of an object record in a cache.
452 static inline void fscache_object_destroyed(struct fscache_cache *cache)
454 if (atomic_dec_and_test(&cache->object_count))
455 wake_up_all(&fscache_cache_cleared_wq);
459 * fscache_object_lookup_error - Note an object encountered an error
460 * @object: The object on which the error was encountered
462 * Note that an object encountered a fatal error (usually an I/O error) and
463 * that it should be withdrawn as soon as possible.
465 static inline void fscache_object_lookup_error(struct fscache_object *object)
467 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
471 * fscache_set_store_limit - Set the maximum size to be stored in an object
472 * @object: The object to set the maximum on
473 * @i_size: The limit to set in bytes
475 * Set the maximum size an object is permitted to reach, implying the highest
476 * byte that may be written. Intended to be called by the attr_changed() op.
478 * See Documentation/filesystems/caching/backend-api.txt for a complete
482 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
484 object->store_limit_l = i_size;
485 object->store_limit = i_size >> PAGE_SHIFT;
486 if (i_size & ~PAGE_MASK)
487 object->store_limit++;
491 * fscache_end_io - End a retrieval operation on a page
492 * @op: The FS-Cache operation covering the retrieval
493 * @page: The page that was to be fetched
494 * @error: The error code (0 if successful)
496 * Note the end of an operation to retrieve a page, as covered by a particular
499 static inline void fscache_end_io(struct fscache_retrieval *op,
500 struct page *page, int error)
502 op->end_io_func(page, op->context, error);
506 * out-of-line cache backend functions
508 extern void fscache_init_cache(struct fscache_cache *cache,
509 const struct fscache_cache_ops *ops,
511 ...) __attribute__ ((format (printf, 3, 4)));
513 extern int fscache_add_cache(struct fscache_cache *cache,
514 struct fscache_object *fsdef,
515 const char *tagname);
516 extern void fscache_withdraw_cache(struct fscache_cache *cache);
518 extern void fscache_io_error(struct fscache_cache *cache);
520 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
521 struct pagevec *pagevec);
523 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
525 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
529 #endif /* _LINUX_FSCACHE_CACHE_H */