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>
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65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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 struct fscache_operation
{
80 struct work_struct fast_work
; /* record for fast ops */
81 struct slow_work slow_work
; /* record for (very) slow ops */
83 struct list_head pend_link
; /* link in object->pending_ops */
84 struct fscache_object
*object
; /* object to be operated upon */
87 #define FSCACHE_OP_TYPE 0x000f /* operation type */
88 #define FSCACHE_OP_FAST 0x0001 /* - fast op, processor may not sleep for disk */
89 #define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */
90 #define FSCACHE_OP_MYTHREAD 0x0003 /* - processing is done be issuing thread, not pool */
91 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
92 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
93 #define FSCACHE_OP_DEAD 6 /* op is now dead */
94 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */
95 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */
98 unsigned debug_id
; /* debugging ID */
100 /* operation processor callback
101 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
102 * the op in a non-pool thread */
103 fscache_operation_processor_t processor
;
105 /* operation releaser */
106 fscache_operation_release_t release
;
108 #ifdef CONFIG_SLOW_WORK_PROC
109 const char *name
; /* operation name */
110 const char *state
; /* operation state */
111 #define fscache_set_op_name(OP, N) do { (OP)->name = (N); } while(0)
112 #define fscache_set_op_state(OP, S) do { (OP)->state = (S); } while(0)
114 #define fscache_set_op_name(OP, N) do { } while(0)
115 #define fscache_set_op_state(OP, S) do { } while(0)
119 extern atomic_t fscache_op_debug_id
;
120 extern const struct slow_work_ops fscache_op_slow_work_ops
;
122 extern void fscache_enqueue_operation(struct fscache_operation
*);
123 extern void fscache_put_operation(struct fscache_operation
*);
126 * fscache_operation_init - Do basic initialisation of an operation
127 * @op: The operation to initialise
128 * @release: The release function to assign
130 * Do basic initialisation of an operation. The caller must still set flags,
131 * object, either fast_work or slow_work if necessary, and processor if needed.
133 static inline void fscache_operation_init(struct fscache_operation
*op
,
134 fscache_operation_release_t release
)
136 atomic_set(&op
->usage
, 1);
137 op
->debug_id
= atomic_inc_return(&fscache_op_debug_id
);
138 op
->release
= release
;
139 INIT_LIST_HEAD(&op
->pend_link
);
140 fscache_set_op_state(op
, "Init");
144 * fscache_operation_init_slow - Do additional initialisation of a slow op
145 * @op: The operation to initialise
146 * @processor: The processor function to assign
148 * Do additional initialisation of an operation as required for slow work.
151 void fscache_operation_init_slow(struct fscache_operation
*op
,
152 fscache_operation_processor_t processor
)
154 op
->processor
= processor
;
155 slow_work_init(&op
->slow_work
, &fscache_op_slow_work_ops
);
159 * data read operation
161 struct fscache_retrieval
{
162 struct fscache_operation op
;
163 struct address_space
*mapping
; /* netfs pages */
164 fscache_rw_complete_t end_io_func
; /* function to call on I/O completion */
165 void *context
; /* netfs read context (pinned) */
166 struct list_head to_do
; /* list of things to be done by the backend */
167 unsigned long start_time
; /* time at which retrieval started */
170 typedef int (*fscache_page_retrieval_func_t
)(struct fscache_retrieval
*op
,
174 typedef int (*fscache_pages_retrieval_func_t
)(struct fscache_retrieval
*op
,
175 struct list_head
*pages
,
180 * fscache_get_retrieval - Get an extra reference on a retrieval operation
181 * @op: The retrieval operation to get a reference on
183 * Get an extra reference on a retrieval operation.
186 struct fscache_retrieval
*fscache_get_retrieval(struct fscache_retrieval
*op
)
188 atomic_inc(&op
->op
.usage
);
193 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
194 * @op: The retrieval operation affected
196 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
198 static inline void fscache_enqueue_retrieval(struct fscache_retrieval
*op
)
200 fscache_enqueue_operation(&op
->op
);
204 * fscache_put_retrieval - Drop a reference to a retrieval operation
205 * @op: The retrieval operation affected
207 * Drop a reference to a retrieval operation.
209 static inline void fscache_put_retrieval(struct fscache_retrieval
*op
)
211 fscache_put_operation(&op
->op
);
215 * cached page storage work item
216 * - used to do three things:
217 * - batch writes to the cache
218 * - do cache writes asynchronously
219 * - defer writes until cache object lookup completion
221 struct fscache_storage
{
222 struct fscache_operation op
;
223 pgoff_t store_limit
; /* don't write more than this */
229 struct fscache_cache_ops
{
230 /* name of cache provider */
233 /* allocate an object record for a cookie */
234 struct fscache_object
*(*alloc_object
)(struct fscache_cache
*cache
,
235 struct fscache_cookie
*cookie
);
237 /* look up the object for a cookie */
238 void (*lookup_object
)(struct fscache_object
*object
);
240 /* finished looking up */
241 void (*lookup_complete
)(struct fscache_object
*object
);
243 /* increment the usage count on this object (may fail if unmounting) */
244 struct fscache_object
*(*grab_object
)(struct fscache_object
*object
);
246 /* pin an object in the cache */
247 int (*pin_object
)(struct fscache_object
*object
);
249 /* unpin an object in the cache */
250 void (*unpin_object
)(struct fscache_object
*object
);
252 /* store the updated auxilliary data on an object */
253 void (*update_object
)(struct fscache_object
*object
);
255 /* discard the resources pinned by an object and effect retirement if
257 void (*drop_object
)(struct fscache_object
*object
);
259 /* dispose of a reference to an object */
260 void (*put_object
)(struct fscache_object
*object
);
263 void (*sync_cache
)(struct fscache_cache
*cache
);
265 /* notification that the attributes of a non-index object (such as
266 * i_size) have changed */
267 int (*attr_changed
)(struct fscache_object
*object
);
269 /* reserve space for an object's data and associated metadata */
270 int (*reserve_space
)(struct fscache_object
*object
, loff_t i_size
);
272 /* request a backing block for a page be read or allocated in the
274 fscache_page_retrieval_func_t read_or_alloc_page
;
276 /* request backing blocks for a list of pages be read or allocated in
278 fscache_pages_retrieval_func_t read_or_alloc_pages
;
280 /* request a backing block for a page be allocated in the cache so that
281 * it can be written directly */
282 fscache_page_retrieval_func_t allocate_page
;
284 /* request backing blocks for pages be allocated in the cache so that
285 * they can be written directly */
286 fscache_pages_retrieval_func_t allocate_pages
;
288 /* write a page to its backing block in the cache */
289 int (*write_page
)(struct fscache_storage
*op
, struct page
*page
);
291 /* detach backing block from a page (optional)
292 * - must release the cookie lock before returning
295 void (*uncache_page
)(struct fscache_object
*object
,
298 /* dissociate a cache from all the pages it was backing */
299 void (*dissociate_pages
)(struct fscache_cache
*cache
);
303 * data file or index object cookie
304 * - a file will only appear in one cache
305 * - a request to cache a file may or may not be honoured, subject to
306 * constraints such as disk space
307 * - indices are created on disk just-in-time
309 struct fscache_cookie
{
310 atomic_t usage
; /* number of users of this cookie */
311 atomic_t n_children
; /* number of children of this cookie */
313 spinlock_t stores_lock
; /* lock on page store tree */
314 struct hlist_head backing_objects
; /* object(s) backing this file/index */
315 const struct fscache_cookie_def
*def
; /* definition */
316 struct fscache_cookie
*parent
; /* parent of this entry */
317 void *netfs_data
; /* back pointer to netfs */
318 struct radix_tree_root stores
; /* pages to be stored on this cookie */
319 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
320 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
323 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
324 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
325 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
326 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
327 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
328 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
331 extern struct fscache_cookie fscache_fsdef_index
;
334 * on-disk cache file or index handle
336 struct fscache_object
{
337 enum fscache_object_state
{
338 FSCACHE_OBJECT_INIT
, /* object in initial unbound state */
339 FSCACHE_OBJECT_LOOKING_UP
, /* looking up object */
340 FSCACHE_OBJECT_CREATING
, /* creating object */
343 FSCACHE_OBJECT_AVAILABLE
, /* cleaning up object after creation */
344 FSCACHE_OBJECT_ACTIVE
, /* object is usable */
345 FSCACHE_OBJECT_UPDATING
, /* object is updating */
347 /* terminal states */
348 FSCACHE_OBJECT_DYING
, /* object waiting for accessors to finish */
349 FSCACHE_OBJECT_LC_DYING
, /* object cleaning up after lookup/create */
350 FSCACHE_OBJECT_ABORT_INIT
, /* abort the init state */
351 FSCACHE_OBJECT_RELEASING
, /* releasing object */
352 FSCACHE_OBJECT_RECYCLING
, /* retiring object */
353 FSCACHE_OBJECT_WITHDRAWING
, /* withdrawing object */
354 FSCACHE_OBJECT_DEAD
, /* object is now dead */
355 FSCACHE_OBJECT__NSTATES
358 int debug_id
; /* debugging ID */
359 int n_children
; /* number of child objects */
360 int n_ops
; /* number of ops outstanding on object */
361 int n_obj_ops
; /* number of object ops outstanding on object */
362 int n_in_progress
; /* number of ops in progress */
363 int n_exclusive
; /* number of exclusive ops queued */
364 atomic_t n_reads
; /* number of read ops in progress */
365 spinlock_t lock
; /* state and operations lock */
367 unsigned long lookup_jif
; /* time at which lookup started */
368 unsigned long event_mask
; /* events this object is interested in */
369 unsigned long events
; /* events to be processed by this object
370 * (order is important - using fls) */
371 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
372 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
373 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
374 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
375 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
376 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
377 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
378 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
381 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
382 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
383 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
385 struct list_head cache_link
; /* link in cache->object_list */
386 struct hlist_node cookie_link
; /* link in cookie->backing_objects */
387 struct fscache_cache
*cache
; /* cache that supplied this object */
388 struct fscache_cookie
*cookie
; /* netfs's file/index object */
389 struct fscache_object
*parent
; /* parent object */
390 struct slow_work work
; /* attention scheduling record */
391 struct list_head dependents
; /* FIFO of dependent objects */
392 struct list_head dep_link
; /* link in parent's dependents list */
393 struct list_head pending_ops
; /* unstarted operations on this object */
394 #ifdef CONFIG_FSCACHE_OBJECT_LIST
395 struct rb_node objlist_link
; /* link in global object list */
397 pgoff_t store_limit
; /* current storage limit */
400 extern const char *fscache_object_states
[];
402 #define fscache_object_is_active(obj) \
403 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
404 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
405 (obj)->state < FSCACHE_OBJECT_DYING)
407 extern const struct slow_work_ops fscache_object_slow_work_ops
;
410 * fscache_object_init - Initialise a cache object description
411 * @object: Object description
413 * Initialise a cache object description to its basic values.
415 * See Documentation/filesystems/caching/backend-api.txt for a complete
419 void fscache_object_init(struct fscache_object
*object
,
420 struct fscache_cookie
*cookie
,
421 struct fscache_cache
*cache
)
423 atomic_inc(&cache
->object_count
);
425 object
->state
= FSCACHE_OBJECT_INIT
;
426 spin_lock_init(&object
->lock
);
427 INIT_LIST_HEAD(&object
->cache_link
);
428 INIT_HLIST_NODE(&object
->cookie_link
);
429 vslow_work_init(&object
->work
, &fscache_object_slow_work_ops
);
430 INIT_LIST_HEAD(&object
->dependents
);
431 INIT_LIST_HEAD(&object
->dep_link
);
432 INIT_LIST_HEAD(&object
->pending_ops
);
433 object
->n_children
= 0;
434 object
->n_ops
= object
->n_in_progress
= object
->n_exclusive
= 0;
435 object
->events
= object
->event_mask
= 0;
437 object
->store_limit
= 0;
438 object
->cache
= cache
;
439 object
->cookie
= cookie
;
440 object
->parent
= NULL
;
443 extern void fscache_object_lookup_negative(struct fscache_object
*object
);
444 extern void fscache_obtained_object(struct fscache_object
*object
);
446 #ifdef CONFIG_FSCACHE_OBJECT_LIST
447 extern void fscache_object_destroy(struct fscache_object
*object
);
449 #define fscache_object_destroy(object) do {} while(0)
453 * fscache_object_destroyed - Note destruction of an object in a cache
454 * @cache: The cache from which the object came
456 * Note the destruction and deallocation of an object record in a cache.
458 static inline void fscache_object_destroyed(struct fscache_cache
*cache
)
460 if (atomic_dec_and_test(&cache
->object_count
))
461 wake_up_all(&fscache_cache_cleared_wq
);
465 * fscache_object_lookup_error - Note an object encountered an error
466 * @object: The object on which the error was encountered
468 * Note that an object encountered a fatal error (usually an I/O error) and
469 * that it should be withdrawn as soon as possible.
471 static inline void fscache_object_lookup_error(struct fscache_object
*object
)
473 set_bit(FSCACHE_OBJECT_EV_ERROR
, &object
->events
);
477 * fscache_set_store_limit - Set the maximum size to be stored in an object
478 * @object: The object to set the maximum on
479 * @i_size: The limit to set in bytes
481 * Set the maximum size an object is permitted to reach, implying the highest
482 * byte that may be written. Intended to be called by the attr_changed() op.
484 * See Documentation/filesystems/caching/backend-api.txt for a complete
488 void fscache_set_store_limit(struct fscache_object
*object
, loff_t i_size
)
490 object
->store_limit
= i_size
>> PAGE_SHIFT
;
491 if (i_size
& ~PAGE_MASK
)
492 object
->store_limit
++;
496 * fscache_end_io - End a retrieval operation on a page
497 * @op: The FS-Cache operation covering the retrieval
498 * @page: The page that was to be fetched
499 * @error: The error code (0 if successful)
501 * Note the end of an operation to retrieve a page, as covered by a particular
504 static inline void fscache_end_io(struct fscache_retrieval
*op
,
505 struct page
*page
, int error
)
507 op
->end_io_func(page
, op
->context
, error
);
511 * out-of-line cache backend functions
513 extern void fscache_init_cache(struct fscache_cache
*cache
,
514 const struct fscache_cache_ops
*ops
,
516 ...) __attribute__ ((format (printf
, 3, 4)));
518 extern int fscache_add_cache(struct fscache_cache
*cache
,
519 struct fscache_object
*fsdef
,
520 const char *tagname
);
521 extern void fscache_withdraw_cache(struct fscache_cache
*cache
);
523 extern void fscache_io_error(struct fscache_cache
*cache
);
525 extern void fscache_mark_pages_cached(struct fscache_retrieval
*op
,
526 struct pagevec
*pagevec
);
528 extern enum fscache_checkaux
fscache_check_aux(struct fscache_object
*object
,
532 #endif /* _LINUX_FSCACHE_CACHE_H */