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65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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
*);
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
->state
= FSCACHE_OP_ST_INITIALISED
;
138 op
->debug_id
= atomic_inc_return(&fscache_op_debug_id
);
139 op
->processor
= processor
;
140 op
->release
= release
;
141 INIT_LIST_HEAD(&op
->pend_link
);
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 */
154 atomic_t n_pages
; /* number of pages to be retrieved */
157 typedef int (*fscache_page_retrieval_func_t
)(struct fscache_retrieval
*op
,
161 typedef int (*fscache_pages_retrieval_func_t
)(struct fscache_retrieval
*op
,
162 struct list_head
*pages
,
167 * fscache_get_retrieval - Get an extra reference on a retrieval operation
168 * @op: The retrieval operation to get a reference on
170 * Get an extra reference on a retrieval operation.
173 struct fscache_retrieval
*fscache_get_retrieval(struct fscache_retrieval
*op
)
175 atomic_inc(&op
->op
.usage
);
180 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
181 * @op: The retrieval operation affected
183 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
185 static inline void fscache_enqueue_retrieval(struct fscache_retrieval
*op
)
187 fscache_enqueue_operation(&op
->op
);
191 * fscache_retrieval_complete - Record (partial) completion of a retrieval
192 * @op: The retrieval operation affected
193 * @n_pages: The number of pages to account for
195 static inline void fscache_retrieval_complete(struct fscache_retrieval
*op
,
198 atomic_sub(n_pages
, &op
->n_pages
);
199 if (atomic_read(&op
->n_pages
) <= 0)
200 fscache_op_complete(&op
->op
, true);
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 * - return -ETIMEDOUT to be requeued
240 int (*lookup_object
)(struct fscache_object
*object
);
242 /* finished looking up */
243 void (*lookup_complete
)(struct fscache_object
*object
);
245 /* increment the usage count on this object (may fail if unmounting) */
246 struct fscache_object
*(*grab_object
)(struct fscache_object
*object
);
248 /* pin an object in the cache */
249 int (*pin_object
)(struct fscache_object
*object
);
251 /* unpin an object in the cache */
252 void (*unpin_object
)(struct fscache_object
*object
);
254 /* check the consistency between the backing cache and the FS-Cache
256 bool (*check_consistency
)(struct fscache_operation
*op
);
258 /* store the updated auxiliary data on an object */
259 void (*update_object
)(struct fscache_object
*object
);
261 /* Invalidate an object */
262 void (*invalidate_object
)(struct fscache_operation
*op
);
264 /* discard the resources pinned by an object and effect retirement if
266 void (*drop_object
)(struct fscache_object
*object
);
268 /* dispose of a reference to an object */
269 void (*put_object
)(struct fscache_object
*object
);
272 void (*sync_cache
)(struct fscache_cache
*cache
);
274 /* notification that the attributes of a non-index object (such as
275 * i_size) have changed */
276 int (*attr_changed
)(struct fscache_object
*object
);
278 /* reserve space for an object's data and associated metadata */
279 int (*reserve_space
)(struct fscache_object
*object
, loff_t i_size
);
281 /* request a backing block for a page be read or allocated in the
283 fscache_page_retrieval_func_t read_or_alloc_page
;
285 /* request backing blocks for a list of pages be read or allocated in
287 fscache_pages_retrieval_func_t read_or_alloc_pages
;
289 /* request a backing block for a page be allocated in the cache so that
290 * it can be written directly */
291 fscache_page_retrieval_func_t allocate_page
;
293 /* request backing blocks for pages be allocated in the cache so that
294 * they can be written directly */
295 fscache_pages_retrieval_func_t allocate_pages
;
297 /* write a page to its backing block in the cache */
298 int (*write_page
)(struct fscache_storage
*op
, struct page
*page
);
300 /* detach backing block from a page (optional)
301 * - must release the cookie lock before returning
304 void (*uncache_page
)(struct fscache_object
*object
,
307 /* dissociate a cache from all the pages it was backing */
308 void (*dissociate_pages
)(struct fscache_cache
*cache
);
311 extern struct fscache_cookie fscache_fsdef_index
;
314 * Event list for fscache_object::{event_mask,events}
317 FSCACHE_OBJECT_EV_NEW_CHILD
, /* T if object has a new child */
318 FSCACHE_OBJECT_EV_PARENT_READY
, /* T if object's parent is ready */
319 FSCACHE_OBJECT_EV_UPDATE
, /* T if object should be updated */
320 FSCACHE_OBJECT_EV_INVALIDATE
, /* T if cache requested object invalidation */
321 FSCACHE_OBJECT_EV_CLEARED
, /* T if accessors all gone */
322 FSCACHE_OBJECT_EV_ERROR
, /* T if fatal error occurred during processing */
323 FSCACHE_OBJECT_EV_KILL
, /* T if netfs relinquished or cache withdrew object */
324 NR_FSCACHE_OBJECT_EVENTS
327 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
330 * States for object state machine.
332 struct fscache_transition
{
333 unsigned long events
;
334 const struct fscache_state
*transit_to
;
337 struct fscache_state
{
340 const struct fscache_state
*(*work
)(struct fscache_object
*object
,
342 const struct fscache_transition transitions
[];
346 * on-disk cache file or index handle
348 struct fscache_object
{
349 const struct fscache_state
*state
; /* Object state machine state */
350 const struct fscache_transition
*oob_table
; /* OOB state transition table */
351 int debug_id
; /* debugging ID */
352 int n_children
; /* number of child objects */
353 int n_ops
; /* number of extant ops on object */
354 int n_obj_ops
; /* number of object ops outstanding on object */
355 int n_in_progress
; /* number of ops in progress */
356 int n_exclusive
; /* number of exclusive ops queued or in progress */
357 atomic_t n_reads
; /* number of read ops in progress */
358 spinlock_t lock
; /* state and operations lock */
360 unsigned long lookup_jif
; /* time at which lookup started */
361 unsigned long oob_event_mask
; /* OOB events this object is interested in */
362 unsigned long event_mask
; /* events this object is interested in */
363 unsigned long events
; /* events to be processed by this object
364 * (order is important - using fls) */
367 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
368 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
369 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
370 #define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
371 #define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
372 #define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
373 #define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */
375 struct list_head cache_link
; /* link in cache->object_list */
376 struct hlist_node cookie_link
; /* link in cookie->backing_objects */
377 struct fscache_cache
*cache
; /* cache that supplied this object */
378 struct fscache_cookie
*cookie
; /* netfs's file/index object */
379 struct fscache_object
*parent
; /* parent object */
380 struct work_struct work
; /* attention scheduling record */
381 struct list_head dependents
; /* FIFO of dependent objects */
382 struct list_head dep_link
; /* link in parent's dependents list */
383 struct list_head pending_ops
; /* unstarted operations on this object */
384 #ifdef CONFIG_FSCACHE_OBJECT_LIST
385 struct rb_node objlist_link
; /* link in global object list */
387 pgoff_t store_limit
; /* current storage limit */
388 loff_t store_limit_l
; /* current storage limit */
391 extern void fscache_object_init(struct fscache_object
*, struct fscache_cookie
*,
392 struct fscache_cache
*);
393 extern void fscache_object_destroy(struct fscache_object
*);
395 extern void fscache_object_lookup_negative(struct fscache_object
*object
);
396 extern void fscache_obtained_object(struct fscache_object
*object
);
398 static inline bool fscache_object_is_live(struct fscache_object
*object
)
400 return test_bit(FSCACHE_OBJECT_IS_LIVE
, &object
->flags
);
403 static inline bool fscache_object_is_dying(struct fscache_object
*object
)
405 return !fscache_object_is_live(object
);
408 static inline bool fscache_object_is_available(struct fscache_object
*object
)
410 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE
, &object
->flags
);
413 static inline bool fscache_object_is_active(struct fscache_object
*object
)
415 return fscache_object_is_available(object
) &&
416 fscache_object_is_live(object
) &&
417 !test_bit(FSCACHE_IOERROR
, &object
->cache
->flags
);
420 static inline bool fscache_object_is_dead(struct fscache_object
*object
)
422 return fscache_object_is_dying(object
) &&
423 test_bit(FSCACHE_IOERROR
, &object
->cache
->flags
);
427 * fscache_object_destroyed - Note destruction of an object in a cache
428 * @cache: The cache from which the object came
430 * Note the destruction and deallocation of an object record in a cache.
432 static inline void fscache_object_destroyed(struct fscache_cache
*cache
)
434 if (atomic_dec_and_test(&cache
->object_count
))
435 wake_up_all(&fscache_cache_cleared_wq
);
439 * fscache_object_lookup_error - Note an object encountered an error
440 * @object: The object on which the error was encountered
442 * Note that an object encountered a fatal error (usually an I/O error) and
443 * that it should be withdrawn as soon as possible.
445 static inline void fscache_object_lookup_error(struct fscache_object
*object
)
447 set_bit(FSCACHE_OBJECT_EV_ERROR
, &object
->events
);
451 * fscache_set_store_limit - Set the maximum size to be stored in an object
452 * @object: The object to set the maximum on
453 * @i_size: The limit to set in bytes
455 * Set the maximum size an object is permitted to reach, implying the highest
456 * byte that may be written. Intended to be called by the attr_changed() op.
458 * See Documentation/filesystems/caching/backend-api.txt for a complete
462 void fscache_set_store_limit(struct fscache_object
*object
, loff_t i_size
)
464 object
->store_limit_l
= i_size
;
465 object
->store_limit
= i_size
>> PAGE_SHIFT
;
466 if (i_size
& ~PAGE_MASK
)
467 object
->store_limit
++;
471 * fscache_end_io - End a retrieval operation on a page
472 * @op: The FS-Cache operation covering the retrieval
473 * @page: The page that was to be fetched
474 * @error: The error code (0 if successful)
476 * Note the end of an operation to retrieve a page, as covered by a particular
479 static inline void fscache_end_io(struct fscache_retrieval
*op
,
480 struct page
*page
, int error
)
482 op
->end_io_func(page
, op
->context
, error
);
485 static inline void __fscache_use_cookie(struct fscache_cookie
*cookie
)
487 atomic_inc(&cookie
->n_active
);
491 * fscache_use_cookie - Request usage of cookie attached to an object
492 * @object: Object description
494 * Request usage of the cookie attached to an object. NULL is returned if the
495 * relinquishment had reduced the cookie usage count to 0.
497 static inline bool fscache_use_cookie(struct fscache_object
*object
)
499 struct fscache_cookie
*cookie
= object
->cookie
;
500 return atomic_inc_not_zero(&cookie
->n_active
) != 0;
503 static inline bool __fscache_unuse_cookie(struct fscache_cookie
*cookie
)
505 return atomic_dec_and_test(&cookie
->n_active
);
508 static inline void __fscache_wake_unused_cookie(struct fscache_cookie
*cookie
)
510 wake_up_atomic_t(&cookie
->n_active
);
514 * fscache_unuse_cookie - Cease usage of cookie attached to an object
515 * @object: Object description
517 * Cease usage of the cookie attached to an object. When the users count
518 * reaches zero then the cookie relinquishment will be permitted to proceed.
520 static inline void fscache_unuse_cookie(struct fscache_object
*object
)
522 struct fscache_cookie
*cookie
= object
->cookie
;
523 if (__fscache_unuse_cookie(cookie
))
524 __fscache_wake_unused_cookie(cookie
);
528 * out-of-line cache backend functions
530 extern __printf(3, 4)
531 void fscache_init_cache(struct fscache_cache
*cache
,
532 const struct fscache_cache_ops
*ops
,
533 const char *idfmt
, ...);
535 extern int fscache_add_cache(struct fscache_cache
*cache
,
536 struct fscache_object
*fsdef
,
537 const char *tagname
);
538 extern void fscache_withdraw_cache(struct fscache_cache
*cache
);
540 extern void fscache_io_error(struct fscache_cache
*cache
);
542 extern void fscache_mark_page_cached(struct fscache_retrieval
*op
,
545 extern void fscache_mark_pages_cached(struct fscache_retrieval
*op
,
546 struct pagevec
*pagevec
);
548 extern bool fscache_object_sleep_till_congested(signed long *timeoutp
);
550 extern enum fscache_checkaux
fscache_check_aux(struct fscache_object
*object
,
554 #endif /* _LINUX_FSCACHE_CACHE_H */