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1/* General filesystem caching backing cache interface
2 *
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells ([email protected])
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
32/*
33 * cache tag definition
34 */
35struct fscache_cache_tag {
36 struct list_head link;
37 struct fscache_cache *cache; /* cache referred to by this tag */
38 unsigned long flags;
39#define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
40 atomic_t usage;
41 char name[0]; /* tag name */
42};
43
44/*
45 * cache definition
46 */
47struct 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 */
54
55 /* node management */
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 */
63 unsigned long flags;
64#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
65#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
66};
67
68extern wait_queue_head_t fscache_cache_cleared_wq;
69
70/*
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
74 */
75typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
76typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
77typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op);
78
79enum fscache_operation_state {
80 FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */
81 FSCACHE_OP_ST_INITIALISED, /* Op is initialised */
82 FSCACHE_OP_ST_PENDING, /* Op is blocked from running */
83 FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */
84 FSCACHE_OP_ST_COMPLETE, /* Op is complete */
85 FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */
86 FSCACHE_OP_ST_DEAD /* Op is now dead */
87};
88
89struct fscache_operation {
90 struct work_struct work; /* record for async ops */
91 struct list_head pend_link; /* link in object->pending_ops */
92 struct fscache_object *object; /* object to be operated upon */
93
94 unsigned long flags;
95#define FSCACHE_OP_TYPE 0x000f /* operation type */
96#define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
97#define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
98#define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
99#define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
100#define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */
101#define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */
102#define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */
103
104 enum fscache_operation_state state;
105 atomic_t usage;
106 unsigned debug_id; /* debugging ID */
107
108 /* operation processor callback
109 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
110 * the op in a non-pool thread */
111 fscache_operation_processor_t processor;
112
113 /* Operation cancellation cleanup (optional) */
114 fscache_operation_cancel_t cancel;
115
116 /* operation releaser */
117 fscache_operation_release_t release;
118};
119
120extern atomic_t fscache_op_debug_id;
121extern void fscache_op_work_func(struct work_struct *work);
122
123extern void fscache_enqueue_operation(struct fscache_operation *);
124extern void fscache_op_complete(struct fscache_operation *, bool);
125extern void fscache_put_operation(struct fscache_operation *);
126extern void fscache_operation_init(struct fscache_operation *,
127 fscache_operation_processor_t,
128 fscache_operation_cancel_t,
129 fscache_operation_release_t);
130
131/*
132 * data read operation
133 */
134struct fscache_retrieval {
135 struct fscache_operation op;
136 struct fscache_cookie *cookie; /* The netfs cookie */
137 struct address_space *mapping; /* netfs pages */
138 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
139 void *context; /* netfs read context (pinned) */
140 struct list_head to_do; /* list of things to be done by the backend */
141 unsigned long start_time; /* time at which retrieval started */
142 atomic_t n_pages; /* number of pages to be retrieved */
143};
144
145typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
146 struct page *page,
147 gfp_t gfp);
148
149typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
150 struct list_head *pages,
151 unsigned *nr_pages,
152 gfp_t gfp);
153
154/**
155 * fscache_get_retrieval - Get an extra reference on a retrieval operation
156 * @op: The retrieval operation to get a reference on
157 *
158 * Get an extra reference on a retrieval operation.
159 */
160static inline
161struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
162{
163 atomic_inc(&op->op.usage);
164 return op;
165}
166
167/**
168 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
169 * @op: The retrieval operation affected
170 *
171 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
172 */
173static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
174{
175 fscache_enqueue_operation(&op->op);
176}
177
178/**
179 * fscache_retrieval_complete - Record (partial) completion of a retrieval
180 * @op: The retrieval operation affected
181 * @n_pages: The number of pages to account for
182 */
183static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
184 int n_pages)
185{
186 atomic_sub(n_pages, &op->n_pages);
187 if (atomic_read(&op->n_pages) <= 0)
188 fscache_op_complete(&op->op, true);
189}
190
191/**
192 * fscache_put_retrieval - Drop a reference to a retrieval operation
193 * @op: The retrieval operation affected
194 *
195 * Drop a reference to a retrieval operation.
196 */
197static inline void fscache_put_retrieval(struct fscache_retrieval *op)
198{
199 fscache_put_operation(&op->op);
200}
201
202/*
203 * cached page storage work item
204 * - used to do three things:
205 * - batch writes to the cache
206 * - do cache writes asynchronously
207 * - defer writes until cache object lookup completion
208 */
209struct fscache_storage {
210 struct fscache_operation op;
211 pgoff_t store_limit; /* don't write more than this */
212};
213
214/*
215 * cache operations
216 */
217struct fscache_cache_ops {
218 /* name of cache provider */
219 const char *name;
220
221 /* allocate an object record for a cookie */
222 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
223 struct fscache_cookie *cookie);
224
225 /* look up the object for a cookie
226 * - return -ETIMEDOUT to be requeued
227 */
228 int (*lookup_object)(struct fscache_object *object);
229
230 /* finished looking up */
231 void (*lookup_complete)(struct fscache_object *object);
232
233 /* increment the usage count on this object (may fail if unmounting) */
234 struct fscache_object *(*grab_object)(struct fscache_object *object);
235
236 /* pin an object in the cache */
237 int (*pin_object)(struct fscache_object *object);
238
239 /* unpin an object in the cache */
240 void (*unpin_object)(struct fscache_object *object);
241
242 /* check the consistency between the backing cache and the FS-Cache
243 * cookie */
244 int (*check_consistency)(struct fscache_operation *op);
245
246 /* store the updated auxiliary data on an object */
247 void (*update_object)(struct fscache_object *object);
248
249 /* Invalidate an object */
250 void (*invalidate_object)(struct fscache_operation *op);
251
252 /* discard the resources pinned by an object and effect retirement if
253 * necessary */
254 void (*drop_object)(struct fscache_object *object);
255
256 /* dispose of a reference to an object */
257 void (*put_object)(struct fscache_object *object);
258
259 /* sync a cache */
260 void (*sync_cache)(struct fscache_cache *cache);
261
262 /* notification that the attributes of a non-index object (such as
263 * i_size) have changed */
264 int (*attr_changed)(struct fscache_object *object);
265
266 /* reserve space for an object's data and associated metadata */
267 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
268
269 /* request a backing block for a page be read or allocated in the
270 * cache */
271 fscache_page_retrieval_func_t read_or_alloc_page;
272
273 /* request backing blocks for a list of pages be read or allocated in
274 * the cache */
275 fscache_pages_retrieval_func_t read_or_alloc_pages;
276
277 /* request a backing block for a page be allocated in the cache so that
278 * it can be written directly */
279 fscache_page_retrieval_func_t allocate_page;
280
281 /* request backing blocks for pages be allocated in the cache so that
282 * they can be written directly */
283 fscache_pages_retrieval_func_t allocate_pages;
284
285 /* write a page to its backing block in the cache */
286 int (*write_page)(struct fscache_storage *op, struct page *page);
287
288 /* detach backing block from a page (optional)
289 * - must release the cookie lock before returning
290 * - may sleep
291 */
292 void (*uncache_page)(struct fscache_object *object,
293 struct page *page);
294
295 /* dissociate a cache from all the pages it was backing */
296 void (*dissociate_pages)(struct fscache_cache *cache);
297};
298
299extern struct fscache_cookie fscache_fsdef_index;
300
301/*
302 * Event list for fscache_object::{event_mask,events}
303 */
304enum {
305 FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */
306 FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
307 FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */
308 FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */
309 FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */
310 FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */
311 FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */
312 NR_FSCACHE_OBJECT_EVENTS
313};
314
315#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
316
317/*
318 * States for object state machine.
319 */
320struct fscache_transition {
321 unsigned long events;
322 const struct fscache_state *transit_to;
323};
324
325struct fscache_state {
326 char name[24];
327 char short_name[8];
328 const struct fscache_state *(*work)(struct fscache_object *object,
329 int event);
330 const struct fscache_transition transitions[];
331};
332
333/*
334 * on-disk cache file or index handle
335 */
336struct fscache_object {
337 const struct fscache_state *state; /* Object state machine state */
338 const struct fscache_transition *oob_table; /* OOB state transition table */
339 int debug_id; /* debugging ID */
340 int n_children; /* number of child objects */
341 int n_ops; /* number of extant ops on object */
342 int n_obj_ops; /* number of object ops outstanding on object */
343 int n_in_progress; /* number of ops in progress */
344 int n_exclusive; /* number of exclusive ops queued or in progress */
345 atomic_t n_reads; /* number of read ops in progress */
346 spinlock_t lock; /* state and operations lock */
347
348 unsigned long lookup_jif; /* time at which lookup started */
349 unsigned long oob_event_mask; /* OOB events this object is interested in */
350 unsigned long event_mask; /* events this object is interested in */
351 unsigned long events; /* events to be processed by this object
352 * (order is important - using fls) */
353
354 unsigned long flags;
355#define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
356#define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
357#define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
358#define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
359#define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
360#define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
361#define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */
362#define FSCACHE_OBJECT_KILLED_BY_CACHE 7 /* T if object was killed by the cache */
363#define FSCACHE_OBJECT_RUN_AFTER_DEAD 8 /* T if object has been dispatched after death */
364
365 struct list_head cache_link; /* link in cache->object_list */
366 struct hlist_node cookie_link; /* link in cookie->backing_objects */
367 struct fscache_cache *cache; /* cache that supplied this object */
368 struct fscache_cookie *cookie; /* netfs's file/index object */
369 struct fscache_object *parent; /* parent object */
370 struct work_struct work; /* attention scheduling record */
371 struct list_head dependents; /* FIFO of dependent objects */
372 struct list_head dep_link; /* link in parent's dependents list */
373 struct list_head pending_ops; /* unstarted operations on this object */
374#ifdef CONFIG_FSCACHE_OBJECT_LIST
375 struct rb_node objlist_link; /* link in global object list */
376#endif
377 pgoff_t store_limit; /* current storage limit */
378 loff_t store_limit_l; /* current storage limit */
379};
380
381extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
382 struct fscache_cache *);
383extern void fscache_object_destroy(struct fscache_object *);
384
385extern void fscache_object_lookup_negative(struct fscache_object *object);
386extern void fscache_obtained_object(struct fscache_object *object);
387
388static inline bool fscache_object_is_live(struct fscache_object *object)
389{
390 return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
391}
392
393static inline bool fscache_object_is_dying(struct fscache_object *object)
394{
395 return !fscache_object_is_live(object);
396}
397
398static inline bool fscache_object_is_available(struct fscache_object *object)
399{
400 return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
401}
402
403static inline bool fscache_cache_is_broken(struct fscache_object *object)
404{
405 return test_bit(FSCACHE_IOERROR, &object->cache->flags);
406}
407
408static inline bool fscache_object_is_active(struct fscache_object *object)
409{
410 return fscache_object_is_available(object) &&
411 fscache_object_is_live(object) &&
412 !fscache_cache_is_broken(object);
413}
414
415/**
416 * fscache_object_destroyed - Note destruction of an object in a cache
417 * @cache: The cache from which the object came
418 *
419 * Note the destruction and deallocation of an object record in a cache.
420 */
421static inline void fscache_object_destroyed(struct fscache_cache *cache)
422{
423 if (atomic_dec_and_test(&cache->object_count))
424 wake_up_all(&fscache_cache_cleared_wq);
425}
426
427/**
428 * fscache_object_lookup_error - Note an object encountered an error
429 * @object: The object on which the error was encountered
430 *
431 * Note that an object encountered a fatal error (usually an I/O error) and
432 * that it should be withdrawn as soon as possible.
433 */
434static inline void fscache_object_lookup_error(struct fscache_object *object)
435{
436 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
437}
438
439/**
440 * fscache_set_store_limit - Set the maximum size to be stored in an object
441 * @object: The object to set the maximum on
442 * @i_size: The limit to set in bytes
443 *
444 * Set the maximum size an object is permitted to reach, implying the highest
445 * byte that may be written. Intended to be called by the attr_changed() op.
446 *
447 * See Documentation/filesystems/caching/backend-api.txt for a complete
448 * description.
449 */
450static inline
451void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
452{
453 object->store_limit_l = i_size;
454 object->store_limit = i_size >> PAGE_SHIFT;
455 if (i_size & ~PAGE_MASK)
456 object->store_limit++;
457}
458
459/**
460 * fscache_end_io - End a retrieval operation on a page
461 * @op: The FS-Cache operation covering the retrieval
462 * @page: The page that was to be fetched
463 * @error: The error code (0 if successful)
464 *
465 * Note the end of an operation to retrieve a page, as covered by a particular
466 * operation record.
467 */
468static inline void fscache_end_io(struct fscache_retrieval *op,
469 struct page *page, int error)
470{
471 op->end_io_func(page, op->context, error);
472}
473
474static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
475{
476 atomic_inc(&cookie->n_active);
477}
478
479/**
480 * fscache_use_cookie - Request usage of cookie attached to an object
481 * @object: Object description
482 *
483 * Request usage of the cookie attached to an object. NULL is returned if the
484 * relinquishment had reduced the cookie usage count to 0.
485 */
486static inline bool fscache_use_cookie(struct fscache_object *object)
487{
488 struct fscache_cookie *cookie = object->cookie;
489 return atomic_inc_not_zero(&cookie->n_active) != 0;
490}
491
492static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
493{
494 return atomic_dec_and_test(&cookie->n_active);
495}
496
497static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
498{
499 wake_up_atomic_t(&cookie->n_active);
500}
501
502/**
503 * fscache_unuse_cookie - Cease usage of cookie attached to an object
504 * @object: Object description
505 *
506 * Cease usage of the cookie attached to an object. When the users count
507 * reaches zero then the cookie relinquishment will be permitted to proceed.
508 */
509static inline void fscache_unuse_cookie(struct fscache_object *object)
510{
511 struct fscache_cookie *cookie = object->cookie;
512 if (__fscache_unuse_cookie(cookie))
513 __fscache_wake_unused_cookie(cookie);
514}
515
516/*
517 * out-of-line cache backend functions
518 */
519extern __printf(3, 4)
520void fscache_init_cache(struct fscache_cache *cache,
521 const struct fscache_cache_ops *ops,
522 const char *idfmt, ...);
523
524extern int fscache_add_cache(struct fscache_cache *cache,
525 struct fscache_object *fsdef,
526 const char *tagname);
527extern void fscache_withdraw_cache(struct fscache_cache *cache);
528
529extern void fscache_io_error(struct fscache_cache *cache);
530
531extern void fscache_mark_page_cached(struct fscache_retrieval *op,
532 struct page *page);
533
534extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
535 struct pagevec *pagevec);
536
537extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
538
539extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
540 const void *data,
541 uint16_t datalen);
542
543extern void fscache_object_retrying_stale(struct fscache_object *object);
544
545enum fscache_why_object_killed {
546 FSCACHE_OBJECT_IS_STALE,
547 FSCACHE_OBJECT_NO_SPACE,
548 FSCACHE_OBJECT_WAS_RETIRED,
549 FSCACHE_OBJECT_WAS_CULLED,
550};
551extern void fscache_object_mark_killed(struct fscache_object *object,
552 enum fscache_why_object_killed why);
553
554#endif /* _LINUX_FSCACHE_CACHE_H */