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
;
32 enum fscache_obj_ref_trace
{
33 fscache_obj_get_add_to_deps
,
34 fscache_obj_get_queue
,
35 fscache_obj_put_alloc_fail
,
36 fscache_obj_put_attach_fail
,
37 fscache_obj_put_drop_obj
,
38 fscache_obj_put_enq_dep
,
39 fscache_obj_put_queue
,
41 fscache_obj_ref__nr_traces
45 * cache tag definition
47 struct fscache_cache_tag
{
48 struct list_head link
;
49 struct fscache_cache
*cache
; /* cache referred to by this tag */
51 #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
53 char name
[0]; /* tag name */
59 struct fscache_cache
{
60 const struct fscache_cache_ops
*ops
;
61 struct fscache_cache_tag
*tag
; /* tag representing this cache */
62 struct kobject
*kobj
; /* system representation of this cache */
63 struct list_head link
; /* link in list of caches */
64 size_t max_index_size
; /* maximum size of index data */
65 char identifier
[36]; /* cache label */
68 struct work_struct op_gc
; /* operation garbage collector */
69 struct list_head object_list
; /* list of data/index objects */
70 struct list_head op_gc_list
; /* list of ops to be deleted */
71 spinlock_t object_list_lock
;
72 spinlock_t op_gc_list_lock
;
73 atomic_t object_count
; /* no. of live objects in this cache */
74 struct fscache_object
*fsdef
; /* object for the fsdef index */
76 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
77 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
80 extern wait_queue_head_t fscache_cache_cleared_wq
;
83 * operation to be applied to a cache object
84 * - retrieval initiation operations are done in the context of the process
85 * that issued them, and not in an async thread pool
87 typedef void (*fscache_operation_release_t
)(struct fscache_operation
*op
);
88 typedef void (*fscache_operation_processor_t
)(struct fscache_operation
*op
);
89 typedef void (*fscache_operation_cancel_t
)(struct fscache_operation
*op
);
91 enum fscache_operation_state
{
92 FSCACHE_OP_ST_BLANK
, /* Op is not yet submitted */
93 FSCACHE_OP_ST_INITIALISED
, /* Op is initialised */
94 FSCACHE_OP_ST_PENDING
, /* Op is blocked from running */
95 FSCACHE_OP_ST_IN_PROGRESS
, /* Op is in progress */
96 FSCACHE_OP_ST_COMPLETE
, /* Op is complete */
97 FSCACHE_OP_ST_CANCELLED
, /* Op has been cancelled */
98 FSCACHE_OP_ST_DEAD
/* Op is now dead */
101 struct fscache_operation
{
102 struct work_struct work
; /* record for async ops */
103 struct list_head pend_link
; /* link in object->pending_ops */
104 struct fscache_object
*object
; /* object to be operated upon */
107 #define FSCACHE_OP_TYPE 0x000f /* operation type */
108 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
109 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
110 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
111 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
112 #define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */
113 #define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */
114 #define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */
116 enum fscache_operation_state state
;
118 unsigned debug_id
; /* debugging ID */
120 /* operation processor callback
121 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
122 * the op in a non-pool thread */
123 fscache_operation_processor_t processor
;
125 /* Operation cancellation cleanup (optional) */
126 fscache_operation_cancel_t cancel
;
128 /* operation releaser */
129 fscache_operation_release_t release
;
132 extern atomic_t fscache_op_debug_id
;
133 extern void fscache_op_work_func(struct work_struct
*work
);
135 extern void fscache_enqueue_operation(struct fscache_operation
*);
136 extern void fscache_op_complete(struct fscache_operation
*, bool);
137 extern void fscache_put_operation(struct fscache_operation
*);
138 extern void fscache_operation_init(struct fscache_cookie
*,
139 struct fscache_operation
*,
140 fscache_operation_processor_t
,
141 fscache_operation_cancel_t
,
142 fscache_operation_release_t
);
145 * data read operation
147 struct fscache_retrieval
{
148 struct fscache_operation op
;
149 struct fscache_cookie
*cookie
; /* The netfs cookie */
150 struct address_space
*mapping
; /* netfs pages */
151 fscache_rw_complete_t end_io_func
; /* function to call on I/O completion */
152 void *context
; /* netfs read context (pinned) */
153 struct list_head to_do
; /* list of things to be done by the backend */
154 unsigned long start_time
; /* time at which retrieval started */
155 atomic_t n_pages
; /* number of pages to be retrieved */
158 typedef int (*fscache_page_retrieval_func_t
)(struct fscache_retrieval
*op
,
162 typedef int (*fscache_pages_retrieval_func_t
)(struct fscache_retrieval
*op
,
163 struct list_head
*pages
,
168 * fscache_get_retrieval - Get an extra reference on a retrieval operation
169 * @op: The retrieval operation to get a reference on
171 * Get an extra reference on a retrieval operation.
174 struct fscache_retrieval
*fscache_get_retrieval(struct fscache_retrieval
*op
)
176 atomic_inc(&op
->op
.usage
);
181 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
182 * @op: The retrieval operation affected
184 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
186 static inline void fscache_enqueue_retrieval(struct fscache_retrieval
*op
)
188 fscache_enqueue_operation(&op
->op
);
192 * fscache_retrieval_complete - Record (partial) completion of a retrieval
193 * @op: The retrieval operation affected
194 * @n_pages: The number of pages to account for
196 static inline void fscache_retrieval_complete(struct fscache_retrieval
*op
,
199 if (atomic_sub_return_relaxed(n_pages
, &op
->n_pages
) <= 0)
200 fscache_op_complete(&op
->op
, false);
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
,
247 enum fscache_obj_ref_trace why
);
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 /* check the consistency between the backing cache and the FS-Cache
257 int (*check_consistency
)(struct fscache_operation
*op
);
259 /* store the updated auxiliary data on an object */
260 void (*update_object
)(struct fscache_object
*object
);
262 /* Invalidate an object */
263 void (*invalidate_object
)(struct fscache_operation
*op
);
265 /* discard the resources pinned by an object and effect retirement if
267 void (*drop_object
)(struct fscache_object
*object
);
269 /* dispose of a reference to an object */
270 void (*put_object
)(struct fscache_object
*object
,
271 enum fscache_obj_ref_trace why
);
274 void (*sync_cache
)(struct fscache_cache
*cache
);
276 /* notification that the attributes of a non-index object (such as
277 * i_size) have changed */
278 int (*attr_changed
)(struct fscache_object
*object
);
280 /* reserve space for an object's data and associated metadata */
281 int (*reserve_space
)(struct fscache_object
*object
, loff_t i_size
);
283 /* request a backing block for a page be read or allocated in the
285 fscache_page_retrieval_func_t read_or_alloc_page
;
287 /* request backing blocks for a list of pages be read or allocated in
289 fscache_pages_retrieval_func_t read_or_alloc_pages
;
291 /* request a backing block for a page be allocated in the cache so that
292 * it can be written directly */
293 fscache_page_retrieval_func_t allocate_page
;
295 /* request backing blocks for pages be allocated in the cache so that
296 * they can be written directly */
297 fscache_pages_retrieval_func_t allocate_pages
;
299 /* write a page to its backing block in the cache */
300 int (*write_page
)(struct fscache_storage
*op
, struct page
*page
);
302 /* detach backing block from a page (optional)
303 * - must release the cookie lock before returning
306 void (*uncache_page
)(struct fscache_object
*object
,
309 /* dissociate a cache from all the pages it was backing */
310 void (*dissociate_pages
)(struct fscache_cache
*cache
);
313 extern struct fscache_cookie fscache_fsdef_index
;
316 * Event list for fscache_object::{event_mask,events}
319 FSCACHE_OBJECT_EV_NEW_CHILD
, /* T if object has a new child */
320 FSCACHE_OBJECT_EV_PARENT_READY
, /* T if object's parent is ready */
321 FSCACHE_OBJECT_EV_UPDATE
, /* T if object should be updated */
322 FSCACHE_OBJECT_EV_INVALIDATE
, /* T if cache requested object invalidation */
323 FSCACHE_OBJECT_EV_CLEARED
, /* T if accessors all gone */
324 FSCACHE_OBJECT_EV_ERROR
, /* T if fatal error occurred during processing */
325 FSCACHE_OBJECT_EV_KILL
, /* T if netfs relinquished or cache withdrew object */
326 NR_FSCACHE_OBJECT_EVENTS
329 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
332 * States for object state machine.
334 struct fscache_transition
{
335 unsigned long events
;
336 const struct fscache_state
*transit_to
;
339 struct fscache_state
{
342 const struct fscache_state
*(*work
)(struct fscache_object
*object
,
344 const struct fscache_transition transitions
[];
348 * on-disk cache file or index handle
350 struct fscache_object
{
351 const struct fscache_state
*state
; /* Object state machine state */
352 const struct fscache_transition
*oob_table
; /* OOB state transition table */
353 int debug_id
; /* debugging ID */
354 int n_children
; /* number of child objects */
355 int n_ops
; /* number of extant ops on object */
356 int n_obj_ops
; /* number of object ops outstanding on object */
357 int n_in_progress
; /* number of ops in progress */
358 int n_exclusive
; /* number of exclusive ops queued or in progress */
359 atomic_t n_reads
; /* number of read ops in progress */
360 spinlock_t lock
; /* state and operations lock */
362 unsigned long lookup_jif
; /* time at which lookup started */
363 unsigned long oob_event_mask
; /* OOB events this object is interested in */
364 unsigned long event_mask
; /* events this object is interested in */
365 unsigned long events
; /* events to be processed by this object
366 * (order is important - using fls) */
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 */
372 #define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
373 #define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
374 #define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
375 #define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */
376 #define FSCACHE_OBJECT_KILLED_BY_CACHE 7 /* T if object was killed by the cache */
377 #define FSCACHE_OBJECT_RUN_AFTER_DEAD 8 /* T if object has been dispatched after death */
379 struct list_head cache_link
; /* link in cache->object_list */
380 struct hlist_node cookie_link
; /* link in cookie->backing_objects */
381 struct fscache_cache
*cache
; /* cache that supplied this object */
382 struct fscache_cookie
*cookie
; /* netfs's file/index object */
383 struct fscache_object
*parent
; /* parent object */
384 struct work_struct work
; /* attention scheduling record */
385 struct list_head dependents
; /* FIFO of dependent objects */
386 struct list_head dep_link
; /* link in parent's dependents list */
387 struct list_head pending_ops
; /* unstarted operations on this object */
388 #ifdef CONFIG_FSCACHE_OBJECT_LIST
389 struct rb_node objlist_link
; /* link in global object list */
391 pgoff_t store_limit
; /* current storage limit */
392 loff_t store_limit_l
; /* current storage limit */
395 extern void fscache_object_init(struct fscache_object
*, struct fscache_cookie
*,
396 struct fscache_cache
*);
397 extern void fscache_object_destroy(struct fscache_object
*);
399 extern void fscache_object_lookup_negative(struct fscache_object
*object
);
400 extern void fscache_obtained_object(struct fscache_object
*object
);
402 static inline bool fscache_object_is_live(struct fscache_object
*object
)
404 return test_bit(FSCACHE_OBJECT_IS_LIVE
, &object
->flags
);
407 static inline bool fscache_object_is_dying(struct fscache_object
*object
)
409 return !fscache_object_is_live(object
);
412 static inline bool fscache_object_is_available(struct fscache_object
*object
)
414 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE
, &object
->flags
);
417 static inline bool fscache_cache_is_broken(struct fscache_object
*object
)
419 return test_bit(FSCACHE_IOERROR
, &object
->cache
->flags
);
422 static inline bool fscache_object_is_active(struct fscache_object
*object
)
424 return fscache_object_is_available(object
) &&
425 fscache_object_is_live(object
) &&
426 !fscache_cache_is_broken(object
);
430 * fscache_object_destroyed - Note destruction of an object in a cache
431 * @cache: The cache from which the object came
433 * Note the destruction and deallocation of an object record in a cache.
435 static inline void fscache_object_destroyed(struct fscache_cache
*cache
)
437 if (atomic_dec_and_test(&cache
->object_count
))
438 wake_up_all(&fscache_cache_cleared_wq
);
442 * fscache_object_lookup_error - Note an object encountered an error
443 * @object: The object on which the error was encountered
445 * Note that an object encountered a fatal error (usually an I/O error) and
446 * that it should be withdrawn as soon as possible.
448 static inline void fscache_object_lookup_error(struct fscache_object
*object
)
450 set_bit(FSCACHE_OBJECT_EV_ERROR
, &object
->events
);
454 * fscache_set_store_limit - Set the maximum size to be stored in an object
455 * @object: The object to set the maximum on
456 * @i_size: The limit to set in bytes
458 * Set the maximum size an object is permitted to reach, implying the highest
459 * byte that may be written. Intended to be called by the attr_changed() op.
461 * See Documentation/filesystems/caching/backend-api.txt for a complete
465 void fscache_set_store_limit(struct fscache_object
*object
, loff_t i_size
)
467 object
->store_limit_l
= i_size
;
468 object
->store_limit
= i_size
>> PAGE_SHIFT
;
469 if (i_size
& ~PAGE_MASK
)
470 object
->store_limit
++;
474 * fscache_end_io - End a retrieval operation on a page
475 * @op: The FS-Cache operation covering the retrieval
476 * @page: The page that was to be fetched
477 * @error: The error code (0 if successful)
479 * Note the end of an operation to retrieve a page, as covered by a particular
482 static inline void fscache_end_io(struct fscache_retrieval
*op
,
483 struct page
*page
, int error
)
485 op
->end_io_func(page
, op
->context
, error
);
488 static inline void __fscache_use_cookie(struct fscache_cookie
*cookie
)
490 atomic_inc(&cookie
->n_active
);
494 * fscache_use_cookie - Request usage of cookie attached to an object
495 * @object: Object description
497 * Request usage of the cookie attached to an object. NULL is returned if the
498 * relinquishment had reduced the cookie usage count to 0.
500 static inline bool fscache_use_cookie(struct fscache_object
*object
)
502 struct fscache_cookie
*cookie
= object
->cookie
;
503 return atomic_inc_not_zero(&cookie
->n_active
) != 0;
506 static inline bool __fscache_unuse_cookie(struct fscache_cookie
*cookie
)
508 return atomic_dec_and_test(&cookie
->n_active
);
511 static inline void __fscache_wake_unused_cookie(struct fscache_cookie
*cookie
)
513 wake_up_var(&cookie
->n_active
);
517 * fscache_unuse_cookie - Cease usage of cookie attached to an object
518 * @object: Object description
520 * Cease usage of the cookie attached to an object. When the users count
521 * reaches zero then the cookie relinquishment will be permitted to proceed.
523 static inline void fscache_unuse_cookie(struct fscache_object
*object
)
525 struct fscache_cookie
*cookie
= object
->cookie
;
526 if (__fscache_unuse_cookie(cookie
))
527 __fscache_wake_unused_cookie(cookie
);
531 * out-of-line cache backend functions
533 extern __printf(3, 4)
534 void fscache_init_cache(struct fscache_cache
*cache
,
535 const struct fscache_cache_ops
*ops
,
536 const char *idfmt
, ...);
538 extern int fscache_add_cache(struct fscache_cache
*cache
,
539 struct fscache_object
*fsdef
,
540 const char *tagname
);
541 extern void fscache_withdraw_cache(struct fscache_cache
*cache
);
543 extern void fscache_io_error(struct fscache_cache
*cache
);
545 extern void fscache_mark_page_cached(struct fscache_retrieval
*op
,
548 extern void fscache_mark_pages_cached(struct fscache_retrieval
*op
,
549 struct pagevec
*pagevec
);
551 extern bool fscache_object_sleep_till_congested(signed long *timeoutp
);
553 extern enum fscache_checkaux
fscache_check_aux(struct fscache_object
*object
,
558 extern void fscache_object_retrying_stale(struct fscache_object
*object
);
560 enum fscache_why_object_killed
{
561 FSCACHE_OBJECT_IS_STALE
,
562 FSCACHE_OBJECT_NO_SPACE
,
563 FSCACHE_OBJECT_WAS_RETIRED
,
564 FSCACHE_OBJECT_WAS_CULLED
,
566 extern void fscache_object_mark_killed(struct fscache_object
*object
,
567 enum fscache_why_object_killed why
);
569 #endif /* _LINUX_FSCACHE_CACHE_H */