1/* General filesystem caching backing cache interface
2 *
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
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.
10 *
11 * NOTE!!! See:
12 *
13 * Documentation/filesystems/caching/backend-api.txt
14 *
15 * for a description of the cache backend interface declared here.
16 */
17
18#ifndef _LINUX_FSCACHE_CACHE_H
19#define _LINUX_FSCACHE_CACHE_H
20
21#include <linux/fscache.h>
22#include <linux/sched.h>
23#include <linux/workqueue.h>
24
25#define NR_MAXCACHES BITS_PER_LONG
26
27struct fscache_cache;
28struct fscache_cache_ops;
29struct fscache_object;
30struct fscache_operation;
31
32enum 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,
40 fscache_obj_put_work,
41 fscache_obj_ref__nr_traces
42};
43
44/*
45 * cache tag definition
46 */
47struct fscache_cache_tag {
48 struct list_head link;
49 struct fscache_cache *cache; /* cache referred to by this tag */
50 unsigned long flags;
51#define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
52 atomic_t usage;
53 char name[0]; /* tag name */
54};
55
56/*
57 * cache definition
58 */
59struct 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 */
66
67 /* node management */
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 */
75 unsigned long flags;
76#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
77#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
78};
79
80extern wait_queue_head_t fscache_cache_cleared_wq;
81
82/*
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
86 */
87typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
88typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
89typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op);
90
91enum 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 */
99};
100
101struct 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 */
105
106 unsigned long flags;
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 */
115
116 enum fscache_operation_state state;
117 atomic_t usage;
118 unsigned debug_id; /* debugging ID */
119
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;
124
125 /* Operation cancellation cleanup (optional) */
126 fscache_operation_cancel_t cancel;
127
128 /* operation releaser */
129 fscache_operation_release_t release;
130};
131
132extern atomic_t fscache_op_debug_id;
133extern void fscache_op_work_func(struct work_struct *work);
134
135extern void fscache_enqueue_operation(struct fscache_operation *);
136extern void fscache_op_complete(struct fscache_operation *, bool);
137extern void fscache_put_operation(struct fscache_operation *);
138extern 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);
143
144/*
145 * data read operation
146 */
147struct 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 */
156};
157
158typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
159 struct page *page,
160 gfp_t gfp);
161
162typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
163 struct list_head *pages,
164 unsigned *nr_pages,
165 gfp_t gfp);
166
167/**
168 * fscache_get_retrieval - Get an extra reference on a retrieval operation
169 * @op: The retrieval operation to get a reference on
170 *
171 * Get an extra reference on a retrieval operation.
172 */
173static inline
174struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
175{
176 atomic_inc(&op->op.usage);
177 return op;
178}
179
180/**
181 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
182 * @op: The retrieval operation affected
183 *
184 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
185 */
186static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
187{
188 fscache_enqueue_operation(&op->op);
189}
190
191/**
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
195 */
196static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
197 int n_pages)
198{
199 if (atomic_sub_return_relaxed(n_pages, &op->n_pages) <= 0)
200 fscache_op_complete(&op->op, false);
201}
202
203/**
204 * fscache_put_retrieval - Drop a reference to a retrieval operation
205 * @op: The retrieval operation affected
206 *
207 * Drop a reference to a retrieval operation.
208 */
209static inline void fscache_put_retrieval(struct fscache_retrieval *op)
210{
211 fscache_put_operation(&op->op);
212}
213
214/*
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
220 */
221struct fscache_storage {
222 struct fscache_operation op;
223 pgoff_t store_limit; /* don't write more than this */
224};
225
226/*
227 * cache operations
228 */
229struct fscache_cache_ops {
230 /* name of cache provider */
231 const char *name;
232
233 /* allocate an object record for a cookie */
234 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
235 struct fscache_cookie *cookie);
236
237 /* look up the object for a cookie
238 * - return -ETIMEDOUT to be requeued
239 */
240 int (*lookup_object)(struct fscache_object *object);
241
242 /* finished looking up */
243 void (*lookup_complete)(struct fscache_object *object);
244
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);
248
249 /* pin an object in the cache */
250 int (*pin_object)(struct fscache_object *object);
251
252 /* unpin an object in the cache */
253 void (*unpin_object)(struct fscache_object *object);
254
255 /* check the consistency between the backing cache and the FS-Cache
256 * cookie */
257 int (*check_consistency)(struct fscache_operation *op);
258
259 /* store the updated auxiliary data on an object */
260 void (*update_object)(struct fscache_object *object);
261
262 /* Invalidate an object */
263 void (*invalidate_object)(struct fscache_operation *op);
264
265 /* discard the resources pinned by an object and effect retirement if
266 * necessary */
267 void (*drop_object)(struct fscache_object *object);
268
269 /* dispose of a reference to an object */
270 void (*put_object)(struct fscache_object *object,
271 enum fscache_obj_ref_trace why);
272
273 /* sync a cache */
274 void (*sync_cache)(struct fscache_cache *cache);
275
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);
279
280 /* reserve space for an object's data and associated metadata */
281 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
282
283 /* request a backing block for a page be read or allocated in the
284 * cache */
285 fscache_page_retrieval_func_t read_or_alloc_page;
286
287 /* request backing blocks for a list of pages be read or allocated in
288 * the cache */
289 fscache_pages_retrieval_func_t read_or_alloc_pages;
290
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;
294
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;
298
299 /* write a page to its backing block in the cache */
300 int (*write_page)(struct fscache_storage *op, struct page *page);
301
302 /* detach backing block from a page (optional)
303 * - must release the cookie lock before returning
304 * - may sleep
305 */
306 void (*uncache_page)(struct fscache_object *object,
307 struct page *page);
308
309 /* dissociate a cache from all the pages it was backing */
310 void (*dissociate_pages)(struct fscache_cache *cache);
311};
312
313extern struct fscache_cookie fscache_fsdef_index;
314
315/*
316 * Event list for fscache_object::{event_mask,events}
317 */
318enum {
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
327};
328
329#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
330
331/*
332 * States for object state machine.
333 */
334struct fscache_transition {
335 unsigned long events;
336 const struct fscache_state *transit_to;
337};
338
339struct fscache_state {
340 char name[24];
341 char short_name[8];
342 const struct fscache_state *(*work)(struct fscache_object *object,
343 int event);
344 const struct fscache_transition transitions[];
345};
346
347/*
348 * on-disk cache file or index handle
349 */
350struct 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 */
361
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) */
367
368 unsigned long flags;
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 */
378
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 */
390#endif
391 pgoff_t store_limit; /* current storage limit */
392 loff_t store_limit_l; /* current storage limit */
393};
394
395extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
396 struct fscache_cache *);
397extern void fscache_object_destroy(struct fscache_object *);
398
399extern void fscache_object_lookup_negative(struct fscache_object *object);
400extern void fscache_obtained_object(struct fscache_object *object);
401
402static inline bool fscache_object_is_live(struct fscache_object *object)
403{
404 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
405}
406
407static inline bool fscache_object_is_dying(struct fscache_object *object)
408{
409 return !fscache_object_is_live(object);
410}
411
412static inline bool fscache_object_is_available(struct fscache_object *object)
413{
414 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
415}
416
417static inline bool fscache_cache_is_broken(struct fscache_object *object)
418{
419 return test_bit(FSCACHE_IOERROR, &object->cache->flags);
420}
421
422static inline bool fscache_object_is_active(struct fscache_object *object)
423{
424 return fscache_object_is_available(object) &&
425 fscache_object_is_live(object) &&
426 !fscache_cache_is_broken(object);
427}
428
429/**
430 * fscache_object_destroyed - Note destruction of an object in a cache
431 * @cache: The cache from which the object came
432 *
433 * Note the destruction and deallocation of an object record in a cache.
434 */
435static inline void fscache_object_destroyed(struct fscache_cache *cache)
436{
437 if (atomic_dec_and_test(&cache->object_count))
438 wake_up_all(&fscache_cache_cleared_wq);
439}
440
441/**
442 * fscache_object_lookup_error - Note an object encountered an error
443 * @object: The object on which the error was encountered
444 *
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.
447 */
448static inline void fscache_object_lookup_error(struct fscache_object *object)
449{
450 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
451}
452
453/**
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
457 *
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.
460 *
461 * See Documentation/filesystems/caching/backend-api.txt for a complete
462 * description.
463 */
464static inline
465void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
466{
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++;
471}
472
473/**
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)
478 *
479 * Note the end of an operation to retrieve a page, as covered by a particular
480 * operation record.
481 */
482static inline void fscache_end_io(struct fscache_retrieval *op,
483 struct page *page, int error)
484{
485 op->end_io_func(page, op->context, error);
486}
487
488static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
489{
490 atomic_inc(&cookie->n_active);
491}
492
493/**
494 * fscache_use_cookie - Request usage of cookie attached to an object
495 * @object: Object description
496 *
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.
499 */
500static inline bool fscache_use_cookie(struct fscache_object *object)
501{
502 struct fscache_cookie *cookie = object->cookie;
503 return atomic_inc_not_zero(&cookie->n_active) != 0;
504}
505
506static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
507{
508 return atomic_dec_and_test(&cookie->n_active);
509}
510
511static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
512{
513 wake_up_var(&cookie->n_active);
514}
515
516/**
517 * fscache_unuse_cookie - Cease usage of cookie attached to an object
518 * @object: Object description
519 *
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.
522 */
523static inline void fscache_unuse_cookie(struct fscache_object *object)
524{
525 struct fscache_cookie *cookie = object->cookie;
526 if (__fscache_unuse_cookie(cookie))
527 __fscache_wake_unused_cookie(cookie);
528}
529
530/*
531 * out-of-line cache backend functions
532 */
533extern __printf(3, 4)
534void fscache_init_cache(struct fscache_cache *cache,
535 const struct fscache_cache_ops *ops,
536 const char *idfmt, ...);
537
538extern int fscache_add_cache(struct fscache_cache *cache,
539 struct fscache_object *fsdef,
540 const char *tagname);
541extern void fscache_withdraw_cache(struct fscache_cache *cache);
542
543extern void fscache_io_error(struct fscache_cache *cache);
544
545extern void fscache_mark_page_cached(struct fscache_retrieval *op,
546 struct page *page);
547
548extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
549 struct pagevec *pagevec);
550
551extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
552
553extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
554 const void *data,
555 uint16_t datalen,
556 loff_t object_size);
557
558extern void fscache_object_retrying_stale(struct fscache_object *object);
559
560enum fscache_why_object_killed {
561 FSCACHE_OBJECT_IS_STALE,
562 FSCACHE_OBJECT_NO_SPACE,
563 FSCACHE_OBJECT_WAS_RETIRED,
564 FSCACHE_OBJECT_WAS_CULLED,
565};
566extern void fscache_object_mark_killed(struct fscache_object *object,
567 enum fscache_why_object_killed why);
568
569#endif /* _LINUX_FSCACHE_CACHE_H */
570