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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 (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/slow-work.h>
24
25 #define NR_MAXCACHES BITS_PER_LONG
26
27 struct fscache_cache;
28 struct fscache_cache_ops;
29 struct fscache_object;
30 struct fscache_operation;
31
32 /*
33 * cache tag definition
34 */
35 struct 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 */
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 */
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65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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
68 extern 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 */
75 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
76 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
77
78 struct fscache_operation {
79 union {
80 struct work_struct fast_work; /* record for fast ops */
81 struct slow_work slow_work; /* record for (very) slow ops */
82 };
83 struct list_head pend_link; /* link in object->pending_ops */
84 struct fscache_object *object; /* object to be operated upon */
85
86 unsigned long flags;
87 #define FSCACHE_OP_TYPE 0x000f /* operation type */
88 #define FSCACHE_OP_FAST 0x0001 /* - fast op, processor may not sleep for disk */
89 #define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */
90 #define FSCACHE_OP_MYTHREAD 0x0003 /* - processing is done be issuing thread, not pool */
91 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
92 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
93 #define FSCACHE_OP_DEAD 6 /* op is now dead */
94 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */
95 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */
96
97 atomic_t usage;
98 unsigned debug_id; /* debugging ID */
99
100 /* operation processor callback
101 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
102 * the op in a non-pool thread */
103 fscache_operation_processor_t processor;
104
105 /* operation releaser */
106 fscache_operation_release_t release;
107
108 #ifdef CONFIG_SLOW_WORK_PROC
109 const char *name; /* operation name */
110 const char *state; /* operation state */
111 #define fscache_set_op_name(OP, N) do { (OP)->name = (N); } while(0)
112 #define fscache_set_op_state(OP, S) do { (OP)->state = (S); } while(0)
113 #else
114 #define fscache_set_op_name(OP, N) do { } while(0)
115 #define fscache_set_op_state(OP, S) do { } while(0)
116 #endif
117 };
118
119 extern atomic_t fscache_op_debug_id;
120 extern const struct slow_work_ops fscache_op_slow_work_ops;
121
122 extern void fscache_enqueue_operation(struct fscache_operation *);
123 extern void fscache_put_operation(struct fscache_operation *);
124
125 /**
126 * fscache_operation_init - Do basic initialisation of an operation
127 * @op: The operation to initialise
128 * @release: The release function to assign
129 *
130 * Do basic initialisation of an operation. The caller must still set flags,
131 * object, either fast_work or slow_work if necessary, and processor if needed.
132 */
133 static inline void fscache_operation_init(struct fscache_operation *op,
134 fscache_operation_release_t release)
135 {
136 atomic_set(&op->usage, 1);
137 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
138 op->release = release;
139 INIT_LIST_HEAD(&op->pend_link);
140 fscache_set_op_state(op, "Init");
141 }
142
143 /**
144 * fscache_operation_init_slow - Do additional initialisation of a slow op
145 * @op: The operation to initialise
146 * @processor: The processor function to assign
147 *
148 * Do additional initialisation of an operation as required for slow work.
149 */
150 static inline
151 void fscache_operation_init_slow(struct fscache_operation *op,
152 fscache_operation_processor_t processor)
153 {
154 op->processor = processor;
155 slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
156 }
157
158 /*
159 * data read operation
160 */
161 struct fscache_retrieval {
162 struct fscache_operation op;
163 struct address_space *mapping; /* netfs pages */
164 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
165 void *context; /* netfs read context (pinned) */
166 struct list_head to_do; /* list of things to be done by the backend */
167 unsigned long start_time; /* time at which retrieval started */
168 };
169
170 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
171 struct page *page,
172 gfp_t gfp);
173
174 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
175 struct list_head *pages,
176 unsigned *nr_pages,
177 gfp_t gfp);
178
179 /**
180 * fscache_get_retrieval - Get an extra reference on a retrieval operation
181 * @op: The retrieval operation to get a reference on
182 *
183 * Get an extra reference on a retrieval operation.
184 */
185 static inline
186 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
187 {
188 atomic_inc(&op->op.usage);
189 return op;
190 }
191
192 /**
193 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
194 * @op: The retrieval operation affected
195 *
196 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
197 */
198 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
199 {
200 fscache_enqueue_operation(&op->op);
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 */
209 static 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 */
221 struct 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 */
229 struct 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
248 /* pin an object in the cache */
249 int (*pin_object)(struct fscache_object *object);
250
251 /* unpin an object in the cache */
252 void (*unpin_object)(struct fscache_object *object);
253
254 /* store the updated auxilliary data on an object */
255 void (*update_object)(struct fscache_object *object);
256
257 /* discard the resources pinned by an object and effect retirement if
258 * necessary */
259 void (*drop_object)(struct fscache_object *object);
260
261 /* dispose of a reference to an object */
262 void (*put_object)(struct fscache_object *object);
263
264 /* sync a cache */
265 void (*sync_cache)(struct fscache_cache *cache);
266
267 /* notification that the attributes of a non-index object (such as
268 * i_size) have changed */
269 int (*attr_changed)(struct fscache_object *object);
270
271 /* reserve space for an object's data and associated metadata */
272 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
273
274 /* request a backing block for a page be read or allocated in the
275 * cache */
276 fscache_page_retrieval_func_t read_or_alloc_page;
277
278 /* request backing blocks for a list of pages be read or allocated in
279 * the cache */
280 fscache_pages_retrieval_func_t read_or_alloc_pages;
281
282 /* request a backing block for a page be allocated in the cache so that
283 * it can be written directly */
284 fscache_page_retrieval_func_t allocate_page;
285
286 /* request backing blocks for pages be allocated in the cache so that
287 * they can be written directly */
288 fscache_pages_retrieval_func_t allocate_pages;
289
290 /* write a page to its backing block in the cache */
291 int (*write_page)(struct fscache_storage *op, struct page *page);
292
293 /* detach backing block from a page (optional)
294 * - must release the cookie lock before returning
295 * - may sleep
296 */
297 void (*uncache_page)(struct fscache_object *object,
298 struct page *page);
299
300 /* dissociate a cache from all the pages it was backing */
301 void (*dissociate_pages)(struct fscache_cache *cache);
302 };
303
304 /*
305 * data file or index object cookie
306 * - a file will only appear in one cache
307 * - a request to cache a file may or may not be honoured, subject to
308 * constraints such as disk space
309 * - indices are created on disk just-in-time
310 */
311 struct fscache_cookie {
312 atomic_t usage; /* number of users of this cookie */
313 atomic_t n_children; /* number of children of this cookie */
314 spinlock_t lock;
315 spinlock_t stores_lock; /* lock on page store tree */
316 struct hlist_head backing_objects; /* object(s) backing this file/index */
317 const struct fscache_cookie_def *def; /* definition */
318 struct fscache_cookie *parent; /* parent of this entry */
319 void *netfs_data; /* back pointer to netfs */
320 struct radix_tree_root stores; /* pages to be stored on this cookie */
321 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
322 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
323
324 unsigned long flags;
325 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
326 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
327 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
328 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
329 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
330 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
331 };
332
333 extern struct fscache_cookie fscache_fsdef_index;
334
335 /*
336 * on-disk cache file or index handle
337 */
338 struct fscache_object {
339 enum fscache_object_state {
340 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
341 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
342 FSCACHE_OBJECT_CREATING, /* creating object */
343
344 /* active states */
345 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
346 FSCACHE_OBJECT_ACTIVE, /* object is usable */
347 FSCACHE_OBJECT_UPDATING, /* object is updating */
348
349 /* terminal states */
350 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
351 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
352 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
353 FSCACHE_OBJECT_RELEASING, /* releasing object */
354 FSCACHE_OBJECT_RECYCLING, /* retiring object */
355 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
356 FSCACHE_OBJECT_DEAD, /* object is now dead */
357 FSCACHE_OBJECT__NSTATES
358 } state;
359
360 int debug_id; /* debugging ID */
361 int n_children; /* number of child objects */
362 int n_ops; /* number of ops outstanding on object */
363 int n_obj_ops; /* number of object ops outstanding on object */
364 int n_in_progress; /* number of ops in progress */
365 int n_exclusive; /* number of exclusive ops queued */
366 atomic_t n_reads; /* number of read ops in progress */
367 spinlock_t lock; /* state and operations lock */
368
369 unsigned long lookup_jif; /* time at which lookup started */
370 unsigned long event_mask; /* events this object is interested in */
371 unsigned long events; /* events to be processed by this object
372 * (order is important - using fls) */
373 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
374 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
375 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
376 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
377 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
378 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
379 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
380 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
381
382 unsigned long flags;
383 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
384 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
385 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
386
387 struct list_head cache_link; /* link in cache->object_list */
388 struct hlist_node cookie_link; /* link in cookie->backing_objects */
389 struct fscache_cache *cache; /* cache that supplied this object */
390 struct fscache_cookie *cookie; /* netfs's file/index object */
391 struct fscache_object *parent; /* parent object */
392 struct slow_work work; /* attention scheduling record */
393 struct list_head dependents; /* FIFO of dependent objects */
394 struct list_head dep_link; /* link in parent's dependents list */
395 struct list_head pending_ops; /* unstarted operations on this object */
396 #ifdef CONFIG_FSCACHE_OBJECT_LIST
397 struct rb_node objlist_link; /* link in global object list */
398 #endif
399 pgoff_t store_limit; /* current storage limit */
400 loff_t store_limit_l; /* current storage limit */
401 };
402
403 extern const char *fscache_object_states[];
404
405 #define fscache_object_is_active(obj) \
406 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
407 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
408 (obj)->state < FSCACHE_OBJECT_DYING)
409
410 #define fscache_object_is_dead(obj) \
411 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
412 (obj)->state >= FSCACHE_OBJECT_DYING)
413
414 extern const struct slow_work_ops fscache_object_slow_work_ops;
415
416 /**
417 * fscache_object_init - Initialise a cache object description
418 * @object: Object description
419 *
420 * Initialise a cache object description to its basic values.
421 *
422 * See Documentation/filesystems/caching/backend-api.txt for a complete
423 * description.
424 */
425 static inline
426 void fscache_object_init(struct fscache_object *object,
427 struct fscache_cookie *cookie,
428 struct fscache_cache *cache)
429 {
430 atomic_inc(&cache->object_count);
431
432 object->state = FSCACHE_OBJECT_INIT;
433 spin_lock_init(&object->lock);
434 INIT_LIST_HEAD(&object->cache_link);
435 INIT_HLIST_NODE(&object->cookie_link);
436 vslow_work_init(&object->work, &fscache_object_slow_work_ops);
437 INIT_LIST_HEAD(&object->dependents);
438 INIT_LIST_HEAD(&object->dep_link);
439 INIT_LIST_HEAD(&object->pending_ops);
440 object->n_children = 0;
441 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
442 object->events = object->event_mask = 0;
443 object->flags = 0;
444 object->store_limit = 0;
445 object->store_limit_l = 0;
446 object->cache = cache;
447 object->cookie = cookie;
448 object->parent = NULL;
449 }
450
451 extern void fscache_object_lookup_negative(struct fscache_object *object);
452 extern void fscache_obtained_object(struct fscache_object *object);
453
454 #ifdef CONFIG_FSCACHE_OBJECT_LIST
455 extern void fscache_object_destroy(struct fscache_object *object);
456 #else
457 #define fscache_object_destroy(object) do {} while(0)
458 #endif
459
460 /**
461 * fscache_object_destroyed - Note destruction of an object in a cache
462 * @cache: The cache from which the object came
463 *
464 * Note the destruction and deallocation of an object record in a cache.
465 */
466 static inline void fscache_object_destroyed(struct fscache_cache *cache)
467 {
468 if (atomic_dec_and_test(&cache->object_count))
469 wake_up_all(&fscache_cache_cleared_wq);
470 }
471
472 /**
473 * fscache_object_lookup_error - Note an object encountered an error
474 * @object: The object on which the error was encountered
475 *
476 * Note that an object encountered a fatal error (usually an I/O error) and
477 * that it should be withdrawn as soon as possible.
478 */
479 static inline void fscache_object_lookup_error(struct fscache_object *object)
480 {
481 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
482 }
483
484 /**
485 * fscache_set_store_limit - Set the maximum size to be stored in an object
486 * @object: The object to set the maximum on
487 * @i_size: The limit to set in bytes
488 *
489 * Set the maximum size an object is permitted to reach, implying the highest
490 * byte that may be written. Intended to be called by the attr_changed() op.
491 *
492 * See Documentation/filesystems/caching/backend-api.txt for a complete
493 * description.
494 */
495 static inline
496 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
497 {
498 object->store_limit_l = i_size;
499 object->store_limit = i_size >> PAGE_SHIFT;
500 if (i_size & ~PAGE_MASK)
501 object->store_limit++;
502 }
503
504 /**
505 * fscache_end_io - End a retrieval operation on a page
506 * @op: The FS-Cache operation covering the retrieval
507 * @page: The page that was to be fetched
508 * @error: The error code (0 if successful)
509 *
510 * Note the end of an operation to retrieve a page, as covered by a particular
511 * operation record.
512 */
513 static inline void fscache_end_io(struct fscache_retrieval *op,
514 struct page *page, int error)
515 {
516 op->end_io_func(page, op->context, error);
517 }
518
519 /*
520 * out-of-line cache backend functions
521 */
522 extern void fscache_init_cache(struct fscache_cache *cache,
523 const struct fscache_cache_ops *ops,
524 const char *idfmt,
525 ...) __attribute__ ((format (printf, 3, 4)));
526
527 extern int fscache_add_cache(struct fscache_cache *cache,
528 struct fscache_object *fsdef,
529 const char *tagname);
530 extern void fscache_withdraw_cache(struct fscache_cache *cache);
531
532 extern void fscache_io_error(struct fscache_cache *cache);
533
534 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
535 struct pagevec *pagevec);
536
537 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
538 const void *data,
539 uint16_t datalen);
540
541 #endif /* _LINUX_FSCACHE_CACHE_H */