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65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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_KEEP_FLAGS 0x0070 /* flags to keep when repurposing an op */
102 enum fscache_operation_state state
;
104 unsigned debug_id
; /* debugging ID */
106 /* operation processor callback
107 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
108 * the op in a non-pool thread */
109 fscache_operation_processor_t processor
;
111 /* operation releaser */
112 fscache_operation_release_t release
;
115 extern atomic_t fscache_op_debug_id
;
116 extern void fscache_op_work_func(struct work_struct
*work
);
118 extern void fscache_enqueue_operation(struct fscache_operation
*);
119 extern void fscache_op_complete(struct fscache_operation
*, bool);
120 extern void fscache_put_operation(struct fscache_operation
*);
123 * fscache_operation_init - Do basic initialisation of an operation
124 * @op: The operation to initialise
125 * @release: The release function to assign
127 * Do basic initialisation of an operation. The caller must still set flags,
128 * object and processor if needed.
130 static inline void fscache_operation_init(struct fscache_operation
*op
,
131 fscache_operation_processor_t processor
,
132 fscache_operation_release_t release
)
134 INIT_WORK(&op
->work
, fscache_op_work_func
);
135 atomic_set(&op
->usage
, 1);
136 op
->state
= FSCACHE_OP_ST_INITIALISED
;
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
);
144 * data read operation
146 struct fscache_retrieval
{
147 struct fscache_operation op
;
148 struct address_space
*mapping
; /* netfs pages */
149 fscache_rw_complete_t end_io_func
; /* function to call on I/O completion */
150 void *context
; /* netfs read context (pinned) */
151 struct list_head to_do
; /* list of things to be done by the backend */
152 unsigned long start_time
; /* time at which retrieval started */
153 unsigned n_pages
; /* number of pages to be retrieved */
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_retrieval_complete - Record (partial) completion of a retrieval
191 * @op: The retrieval operation affected
192 * @n_pages: The number of pages to account for
194 static inline void fscache_retrieval_complete(struct fscache_retrieval
*op
,
197 op
->n_pages
-= n_pages
;
198 if (op
->n_pages
<= 0)
199 fscache_op_complete(&op
->op
, true);
203 * fscache_put_retrieval - Drop a reference to a retrieval operation
204 * @op: The retrieval operation affected
205 * @n_pages: The number of pages to account for
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 /* store the updated auxiliary data on an object */
255 void (*update_object
)(struct fscache_object
*object
);
257 /* Invalidate an object */
258 void (*invalidate_object
)(struct fscache_operation
*op
);
260 /* discard the resources pinned by an object and effect retirement if
262 void (*drop_object
)(struct fscache_object
*object
);
264 /* dispose of a reference to an object */
265 void (*put_object
)(struct fscache_object
*object
);
268 void (*sync_cache
)(struct fscache_cache
*cache
);
270 /* notification that the attributes of a non-index object (such as
271 * i_size) have changed */
272 int (*attr_changed
)(struct fscache_object
*object
);
274 /* reserve space for an object's data and associated metadata */
275 int (*reserve_space
)(struct fscache_object
*object
, loff_t i_size
);
277 /* request a backing block for a page be read or allocated in the
279 fscache_page_retrieval_func_t read_or_alloc_page
;
281 /* request backing blocks for a list of pages be read or allocated in
283 fscache_pages_retrieval_func_t read_or_alloc_pages
;
285 /* request a backing block for a page be allocated in the cache so that
286 * it can be written directly */
287 fscache_page_retrieval_func_t allocate_page
;
289 /* request backing blocks for pages be allocated in the cache so that
290 * they can be written directly */
291 fscache_pages_retrieval_func_t allocate_pages
;
293 /* write a page to its backing block in the cache */
294 int (*write_page
)(struct fscache_storage
*op
, struct page
*page
);
296 /* detach backing block from a page (optional)
297 * - must release the cookie lock before returning
300 void (*uncache_page
)(struct fscache_object
*object
,
303 /* dissociate a cache from all the pages it was backing */
304 void (*dissociate_pages
)(struct fscache_cache
*cache
);
308 * data file or index object cookie
309 * - a file will only appear in one cache
310 * - a request to cache a file may or may not be honoured, subject to
311 * constraints such as disk space
312 * - indices are created on disk just-in-time
314 struct fscache_cookie
{
315 atomic_t usage
; /* number of users of this cookie */
316 atomic_t n_children
; /* number of children of this cookie */
318 spinlock_t stores_lock
; /* lock on page store tree */
319 struct hlist_head backing_objects
; /* object(s) backing this file/index */
320 const struct fscache_cookie_def
*def
; /* definition */
321 struct fscache_cookie
*parent
; /* parent of this entry */
322 void *netfs_data
; /* back pointer to netfs */
323 struct radix_tree_root stores
; /* pages to be stored on this cookie */
324 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
325 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
328 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
329 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
330 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
331 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
332 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
333 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
334 #define FSCACHE_COOKIE_WAITING_ON_READS 6 /* T if cookie is waiting on reads */
335 #define FSCACHE_COOKIE_INVALIDATING 7 /* T if cookie is being invalidated */
338 extern struct fscache_cookie fscache_fsdef_index
;
341 * Event list for fscache_object::{event_mask,events}
344 FSCACHE_OBJECT_EV_REQUEUE
, /* T if object should be requeued */
345 FSCACHE_OBJECT_EV_UPDATE
, /* T if object should be updated */
346 FSCACHE_OBJECT_EV_INVALIDATE
, /* T if cache requested object invalidation */
347 FSCACHE_OBJECT_EV_CLEARED
, /* T if accessors all gone */
348 FSCACHE_OBJECT_EV_ERROR
, /* T if fatal error occurred during processing */
349 FSCACHE_OBJECT_EV_RELEASE
, /* T if netfs requested object release */
350 FSCACHE_OBJECT_EV_RETIRE
, /* T if netfs requested object retirement */
351 FSCACHE_OBJECT_EV_WITHDRAW
, /* T if cache requested object withdrawal */
352 NR_FSCACHE_OBJECT_EVENTS
355 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
358 * on-disk cache file or index handle
360 struct fscache_object
{
361 enum fscache_object_state
{
362 FSCACHE_OBJECT_INIT
, /* object in initial unbound state */
363 FSCACHE_OBJECT_LOOKING_UP
, /* looking up object */
364 FSCACHE_OBJECT_CREATING
, /* creating object */
367 FSCACHE_OBJECT_AVAILABLE
, /* cleaning up object after creation */
368 FSCACHE_OBJECT_ACTIVE
, /* object is usable */
369 FSCACHE_OBJECT_INVALIDATING
, /* object is invalidating */
370 FSCACHE_OBJECT_UPDATING
, /* object is updating */
372 /* terminal states */
373 FSCACHE_OBJECT_DYING
, /* object waiting for accessors to finish */
374 FSCACHE_OBJECT_LC_DYING
, /* object cleaning up after lookup/create */
375 FSCACHE_OBJECT_ABORT_INIT
, /* abort the init state */
376 FSCACHE_OBJECT_RELEASING
, /* releasing object */
377 FSCACHE_OBJECT_RECYCLING
, /* retiring object */
378 FSCACHE_OBJECT_WITHDRAWING
, /* withdrawing object */
379 FSCACHE_OBJECT_DEAD
, /* object is now dead */
380 FSCACHE_OBJECT__NSTATES
383 int debug_id
; /* debugging ID */
384 int n_children
; /* number of child objects */
385 int n_ops
; /* number of extant ops on object */
386 int n_obj_ops
; /* number of object ops outstanding on object */
387 int n_in_progress
; /* number of ops in progress */
388 int n_exclusive
; /* number of exclusive ops queued or in progress */
389 atomic_t n_reads
; /* number of read ops in progress */
390 spinlock_t lock
; /* state and operations lock */
392 unsigned long lookup_jif
; /* time at which lookup started */
393 unsigned long event_mask
; /* events this object is interested in */
394 unsigned long events
; /* events to be processed by this object
395 * (order is important - using fls) */
398 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
399 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
400 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
402 struct list_head cache_link
; /* link in cache->object_list */
403 struct hlist_node cookie_link
; /* link in cookie->backing_objects */
404 struct fscache_cache
*cache
; /* cache that supplied this object */
405 struct fscache_cookie
*cookie
; /* netfs's file/index object */
406 struct fscache_object
*parent
; /* parent object */
407 struct work_struct work
; /* attention scheduling record */
408 struct list_head dependents
; /* FIFO of dependent objects */
409 struct list_head dep_link
; /* link in parent's dependents list */
410 struct list_head pending_ops
; /* unstarted operations on this object */
411 #ifdef CONFIG_FSCACHE_OBJECT_LIST
412 struct rb_node objlist_link
; /* link in global object list */
414 pgoff_t store_limit
; /* current storage limit */
415 loff_t store_limit_l
; /* current storage limit */
418 extern const char *fscache_object_states
[];
420 #define fscache_object_is_active(obj) \
421 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
422 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
423 (obj)->state < FSCACHE_OBJECT_DYING)
425 #define fscache_object_is_dead(obj) \
426 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
427 (obj)->state >= FSCACHE_OBJECT_DYING)
429 extern void fscache_object_work_func(struct work_struct
*work
);
432 * fscache_object_init - Initialise a cache object description
433 * @object: Object description
435 * Initialise a cache object description to its basic values.
437 * See Documentation/filesystems/caching/backend-api.txt for a complete
441 void fscache_object_init(struct fscache_object
*object
,
442 struct fscache_cookie
*cookie
,
443 struct fscache_cache
*cache
)
445 atomic_inc(&cache
->object_count
);
447 object
->state
= FSCACHE_OBJECT_INIT
;
448 spin_lock_init(&object
->lock
);
449 INIT_LIST_HEAD(&object
->cache_link
);
450 INIT_HLIST_NODE(&object
->cookie_link
);
451 INIT_WORK(&object
->work
, fscache_object_work_func
);
452 INIT_LIST_HEAD(&object
->dependents
);
453 INIT_LIST_HEAD(&object
->dep_link
);
454 INIT_LIST_HEAD(&object
->pending_ops
);
455 object
->n_children
= 0;
456 object
->n_ops
= object
->n_in_progress
= object
->n_exclusive
= 0;
457 object
->events
= object
->event_mask
= 0;
459 object
->store_limit
= 0;
460 object
->store_limit_l
= 0;
461 object
->cache
= cache
;
462 object
->cookie
= cookie
;
463 object
->parent
= NULL
;
466 extern void fscache_object_lookup_negative(struct fscache_object
*object
);
467 extern void fscache_obtained_object(struct fscache_object
*object
);
469 #ifdef CONFIG_FSCACHE_OBJECT_LIST
470 extern void fscache_object_destroy(struct fscache_object
*object
);
472 #define fscache_object_destroy(object) do {} while(0)
476 * fscache_object_destroyed - Note destruction of an object in a cache
477 * @cache: The cache from which the object came
479 * Note the destruction and deallocation of an object record in a cache.
481 static inline void fscache_object_destroyed(struct fscache_cache
*cache
)
483 if (atomic_dec_and_test(&cache
->object_count
))
484 wake_up_all(&fscache_cache_cleared_wq
);
488 * fscache_object_lookup_error - Note an object encountered an error
489 * @object: The object on which the error was encountered
491 * Note that an object encountered a fatal error (usually an I/O error) and
492 * that it should be withdrawn as soon as possible.
494 static inline void fscache_object_lookup_error(struct fscache_object
*object
)
496 set_bit(FSCACHE_OBJECT_EV_ERROR
, &object
->events
);
500 * fscache_set_store_limit - Set the maximum size to be stored in an object
501 * @object: The object to set the maximum on
502 * @i_size: The limit to set in bytes
504 * Set the maximum size an object is permitted to reach, implying the highest
505 * byte that may be written. Intended to be called by the attr_changed() op.
507 * See Documentation/filesystems/caching/backend-api.txt for a complete
511 void fscache_set_store_limit(struct fscache_object
*object
, loff_t i_size
)
513 object
->store_limit_l
= i_size
;
514 object
->store_limit
= i_size
>> PAGE_SHIFT
;
515 if (i_size
& ~PAGE_MASK
)
516 object
->store_limit
++;
520 * fscache_end_io - End a retrieval operation on a page
521 * @op: The FS-Cache operation covering the retrieval
522 * @page: The page that was to be fetched
523 * @error: The error code (0 if successful)
525 * Note the end of an operation to retrieve a page, as covered by a particular
528 static inline void fscache_end_io(struct fscache_retrieval
*op
,
529 struct page
*page
, int error
)
531 op
->end_io_func(page
, op
->context
, error
);
535 * out-of-line cache backend functions
537 extern __printf(3, 4)
538 void fscache_init_cache(struct fscache_cache
*cache
,
539 const struct fscache_cache_ops
*ops
,
540 const char *idfmt
, ...);
542 extern int fscache_add_cache(struct fscache_cache
*cache
,
543 struct fscache_object
*fsdef
,
544 const char *tagname
);
545 extern void fscache_withdraw_cache(struct fscache_cache
*cache
);
547 extern void fscache_io_error(struct fscache_cache
*cache
);
549 extern void fscache_mark_page_cached(struct fscache_retrieval
*op
,
552 extern void fscache_mark_pages_cached(struct fscache_retrieval
*op
,
553 struct pagevec
*pagevec
);
555 extern bool fscache_object_sleep_till_congested(signed long *timeoutp
);
557 extern enum fscache_checkaux
fscache_check_aux(struct fscache_object
*object
,
561 #endif /* _LINUX_FSCACHE_CACHE_H */