1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /* General filesystem caching backing cache interface
4 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
9 * Documentation/filesystems/caching/backend-api.rst
11 * for a description of the cache backend interface declared here.
14 #ifndef _LINUX_FSCACHE_CACHE_H
15 #define _LINUX_FSCACHE_CACHE_H
17 #include <linux/fscache.h>
18 #include <linux/sched.h>
19 #include <linux/workqueue.h>
21 #define NR_MAXCACHES BITS_PER_LONG
24 struct fscache_cache_ops
;
25 struct fscache_object
;
26 struct fscache_operation
;
28 enum fscache_obj_ref_trace
{
29 fscache_obj_get_add_to_deps
,
30 fscache_obj_get_queue
,
31 fscache_obj_put_alloc_fail
,
32 fscache_obj_put_attach_fail
,
33 fscache_obj_put_drop_obj
,
34 fscache_obj_put_enq_dep
,
35 fscache_obj_put_queue
,
37 fscache_obj_ref__nr_traces
41 * cache tag definition
43 struct fscache_cache_tag
{
44 struct list_head link
;
45 struct fscache_cache
*cache
; /* cache referred to by this tag */
47 #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
49 char name
[]; /* tag name */
55 struct fscache_cache
{
56 const struct fscache_cache_ops
*ops
;
57 struct fscache_cache_tag
*tag
; /* tag representing this cache */
58 struct kobject
*kobj
; /* system representation of this cache */
59 struct list_head link
; /* link in list of caches */
60 size_t max_index_size
; /* maximum size of index data */
61 char identifier
[36]; /* cache label */
64 struct work_struct op_gc
; /* operation garbage collector */
65 struct list_head object_list
; /* list of data/index objects */
66 struct list_head op_gc_list
; /* list of ops to be deleted */
67 spinlock_t object_list_lock
;
68 spinlock_t op_gc_list_lock
;
69 atomic_t object_count
; /* no. of live objects in this cache */
70 struct fscache_object
*fsdef
; /* object for the fsdef index */
72 #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
73 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
76 extern wait_queue_head_t fscache_cache_cleared_wq
;
79 * operation to be applied to a cache object
80 * - retrieval initiation operations are done in the context of the process
81 * that issued them, and not in an async thread pool
83 typedef void (*fscache_operation_release_t
)(struct fscache_operation
*op
);
84 typedef void (*fscache_operation_processor_t
)(struct fscache_operation
*op
);
85 typedef void (*fscache_operation_cancel_t
)(struct fscache_operation
*op
);
87 enum fscache_operation_state
{
88 FSCACHE_OP_ST_BLANK
, /* Op is not yet submitted */
89 FSCACHE_OP_ST_INITIALISED
, /* Op is initialised */
90 FSCACHE_OP_ST_PENDING
, /* Op is blocked from running */
91 FSCACHE_OP_ST_IN_PROGRESS
, /* Op is in progress */
92 FSCACHE_OP_ST_COMPLETE
, /* Op is complete */
93 FSCACHE_OP_ST_CANCELLED
, /* Op has been cancelled */
94 FSCACHE_OP_ST_DEAD
/* Op is now dead */
97 struct fscache_operation
{
98 struct work_struct work
; /* record for async ops */
99 struct list_head pend_link
; /* link in object->pending_ops */
100 struct fscache_object
*object
; /* object to be operated upon */
103 #define FSCACHE_OP_TYPE 0x000f /* operation type */
104 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
105 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
106 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
107 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
108 #define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */
109 #define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */
110 #define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */
112 enum fscache_operation_state state
;
114 unsigned debug_id
; /* debugging ID */
116 /* operation processor callback
117 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
118 * the op in a non-pool thread */
119 fscache_operation_processor_t processor
;
121 /* Operation cancellation cleanup (optional) */
122 fscache_operation_cancel_t cancel
;
124 /* operation releaser */
125 fscache_operation_release_t release
;
128 extern atomic_t fscache_op_debug_id
;
129 extern void fscache_op_work_func(struct work_struct
*work
);
131 extern void fscache_enqueue_operation(struct fscache_operation
*);
132 extern void fscache_op_complete(struct fscache_operation
*, bool);
133 extern void fscache_put_operation(struct fscache_operation
*);
134 extern void fscache_operation_init(struct fscache_cookie
*,
135 struct fscache_operation
*,
136 fscache_operation_processor_t
,
137 fscache_operation_cancel_t
,
138 fscache_operation_release_t
);
141 * data read operation
143 struct fscache_retrieval
{
144 struct fscache_operation op
;
145 struct fscache_cookie
*cookie
; /* The netfs cookie */
146 struct address_space
*mapping
; /* netfs pages */
147 fscache_rw_complete_t end_io_func
; /* function to call on I/O completion */
148 void *context
; /* netfs read context (pinned) */
149 struct list_head to_do
; /* list of things to be done by the backend */
150 unsigned long start_time
; /* time at which retrieval started */
151 atomic_t n_pages
; /* number of pages to be retrieved */
154 typedef int (*fscache_page_retrieval_func_t
)(struct fscache_retrieval
*op
,
158 typedef int (*fscache_pages_retrieval_func_t
)(struct fscache_retrieval
*op
,
159 struct list_head
*pages
,
164 * fscache_get_retrieval - Get an extra reference on a retrieval operation
165 * @op: The retrieval operation to get a reference on
167 * Get an extra reference on a retrieval operation.
170 struct fscache_retrieval
*fscache_get_retrieval(struct fscache_retrieval
*op
)
172 atomic_inc(&op
->op
.usage
);
177 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
178 * @op: The retrieval operation affected
180 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
182 static inline void fscache_enqueue_retrieval(struct fscache_retrieval
*op
)
184 fscache_enqueue_operation(&op
->op
);
188 * fscache_retrieval_complete - Record (partial) completion of a retrieval
189 * @op: The retrieval operation affected
190 * @n_pages: The number of pages to account for
192 static inline void fscache_retrieval_complete(struct fscache_retrieval
*op
,
195 if (atomic_sub_return_relaxed(n_pages
, &op
->n_pages
) <= 0)
196 fscache_op_complete(&op
->op
, false);
200 * fscache_put_retrieval - Drop a reference to a retrieval operation
201 * @op: The retrieval operation affected
203 * Drop a reference to a retrieval operation.
205 static inline void fscache_put_retrieval(struct fscache_retrieval
*op
)
207 fscache_put_operation(&op
->op
);
211 * cached page storage work item
212 * - used to do three things:
213 * - batch writes to the cache
214 * - do cache writes asynchronously
215 * - defer writes until cache object lookup completion
217 struct fscache_storage
{
218 struct fscache_operation op
;
219 pgoff_t store_limit
; /* don't write more than this */
225 struct fscache_cache_ops
{
226 /* name of cache provider */
229 /* allocate an object record for a cookie */
230 struct fscache_object
*(*alloc_object
)(struct fscache_cache
*cache
,
231 struct fscache_cookie
*cookie
);
233 /* look up the object for a cookie
234 * - return -ETIMEDOUT to be requeued
236 int (*lookup_object
)(struct fscache_object
*object
);
238 /* finished looking up */
239 void (*lookup_complete
)(struct fscache_object
*object
);
241 /* increment the usage count on this object (may fail if unmounting) */
242 struct fscache_object
*(*grab_object
)(struct fscache_object
*object
,
243 enum fscache_obj_ref_trace why
);
245 /* pin an object in the cache */
246 int (*pin_object
)(struct fscache_object
*object
);
248 /* unpin an object in the cache */
249 void (*unpin_object
)(struct fscache_object
*object
);
251 /* check the consistency between the backing cache and the FS-Cache
253 int (*check_consistency
)(struct fscache_operation
*op
);
255 /* store the updated auxiliary data on an object */
256 void (*update_object
)(struct fscache_object
*object
);
258 /* Invalidate an object */
259 void (*invalidate_object
)(struct fscache_operation
*op
);
261 /* discard the resources pinned by an object and effect retirement if
263 void (*drop_object
)(struct fscache_object
*object
);
265 /* dispose of a reference to an object */
266 void (*put_object
)(struct fscache_object
*object
,
267 enum fscache_obj_ref_trace why
);
270 void (*sync_cache
)(struct fscache_cache
*cache
);
272 /* notification that the attributes of a non-index object (such as
273 * i_size) have changed */
274 int (*attr_changed
)(struct fscache_object
*object
);
276 /* reserve space for an object's data and associated metadata */
277 int (*reserve_space
)(struct fscache_object
*object
, loff_t i_size
);
279 /* request a backing block for a page be read or allocated in the
281 fscache_page_retrieval_func_t read_or_alloc_page
;
283 /* request backing blocks for a list of pages be read or allocated in
285 fscache_pages_retrieval_func_t read_or_alloc_pages
;
287 /* request a backing block for a page be allocated in the cache so that
288 * it can be written directly */
289 fscache_page_retrieval_func_t allocate_page
;
291 /* request backing blocks for pages be allocated in the cache so that
292 * they can be written directly */
293 fscache_pages_retrieval_func_t allocate_pages
;
295 /* write a page to its backing block in the cache */
296 int (*write_page
)(struct fscache_storage
*op
, struct page
*page
);
298 /* detach backing block from a page (optional)
299 * - must release the cookie lock before returning
302 void (*uncache_page
)(struct fscache_object
*object
,
305 /* dissociate a cache from all the pages it was backing */
306 void (*dissociate_pages
)(struct fscache_cache
*cache
);
308 /* Begin a read operation for the netfs lib */
309 int (*begin_read_operation
)(struct netfs_read_request
*rreq
,
310 struct fscache_retrieval
*op
);
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.rst 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 */