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
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65 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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 struct work_struct work; /* record for async ops */
80 struct list_head pend_link; /* link in object->pending_ops */
81 struct fscache_object *object; /* object to be operated upon */
82
83 unsigned long flags;
84 #define FSCACHE_OP_TYPE 0x000f /* operation type */
85 #define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
86 #define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
87 #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
88 #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
89 #define FSCACHE_OP_DEAD 6 /* op is now dead */
90 #define FSCACHE_OP_DEC_READ_CNT 7 /* decrement object->n_reads on destruction */
91 #define FSCACHE_OP_KEEP_FLAGS 0xc0 /* flags to keep when repurposing an op */
92
93 atomic_t usage;
94 unsigned debug_id; /* debugging ID */
95
96 /* operation processor callback
97 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
98 * the op in a non-pool thread */
99 fscache_operation_processor_t processor;
100
101 /* operation releaser */
102 fscache_operation_release_t release;
103
104 #ifdef CONFIG_WORKQUEUE_DEBUGFS
105 struct work_struct put_work; /* work to delay operation put */
106 const char *name; /* operation name */
107 const char *state; /* operation state */
108 #define fscache_set_op_name(OP, N) do { (OP)->name = (N); } while(0)
109 #define fscache_set_op_state(OP, S) do { (OP)->state = (S); } while(0)
110 #else
111 #define fscache_set_op_name(OP, N) do { } while(0)
112 #define fscache_set_op_state(OP, S) do { } while(0)
113 #endif
114 };
115
116 extern atomic_t fscache_op_debug_id;
117 extern void fscache_op_work_func(struct work_struct *work);
118
119 extern void fscache_enqueue_operation(struct fscache_operation *);
120 extern void fscache_put_operation(struct fscache_operation *);
121
122 /**
123 * fscache_operation_init - Do basic initialisation of an operation
124 * @op: The operation to initialise
125 * @release: The release function to assign
126 *
127 * Do basic initialisation of an operation. The caller must still set flags,
128 * object and processor if needed.
129 */
fscache_operation_init(struct fscache_operation * op,fscache_operation_processor_t processor,fscache_operation_release_t release)130 static inline void fscache_operation_init(struct fscache_operation *op,
131 fscache_operation_processor_t processor,
132 fscache_operation_release_t release)
133 {
134 INIT_WORK(&op->work, fscache_op_work_func);
135 atomic_set(&op->usage, 1);
136 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
137 op->processor = processor;
138 op->release = release;
139 INIT_LIST_HEAD(&op->pend_link);
140 fscache_set_op_state(op, "Init");
141 }
142
143 /*
144 * data read operation
145 */
146 struct fscache_retrieval {
147 struct fscache_operation op;
148 struct address_space *mapping; /* netfs pages */
149 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
150 void *context; /* netfs read context (pinned) */
151 struct list_head to_do; /* list of things to be done by the backend */
152 unsigned long start_time; /* time at which retrieval started */
153 };
154
155 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
156 struct page *page,
157 gfp_t gfp);
158
159 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
160 struct list_head *pages,
161 unsigned *nr_pages,
162 gfp_t gfp);
163
164 /**
165 * fscache_get_retrieval - Get an extra reference on a retrieval operation
166 * @op: The retrieval operation to get a reference on
167 *
168 * Get an extra reference on a retrieval operation.
169 */
170 static inline
fscache_get_retrieval(struct fscache_retrieval * op)171 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
172 {
173 atomic_inc(&op->op.usage);
174 return op;
175 }
176
177 /**
178 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
179 * @op: The retrieval operation affected
180 *
181 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
182 */
fscache_enqueue_retrieval(struct fscache_retrieval * op)183 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
184 {
185 fscache_enqueue_operation(&op->op);
186 }
187
188 /**
189 * fscache_put_retrieval - Drop a reference to a retrieval operation
190 * @op: The retrieval operation affected
191 *
192 * Drop a reference to a retrieval operation.
193 */
fscache_put_retrieval(struct fscache_retrieval * op)194 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
195 {
196 fscache_put_operation(&op->op);
197 }
198
199 /*
200 * cached page storage work item
201 * - used to do three things:
202 * - batch writes to the cache
203 * - do cache writes asynchronously
204 * - defer writes until cache object lookup completion
205 */
206 struct fscache_storage {
207 struct fscache_operation op;
208 pgoff_t store_limit; /* don't write more than this */
209 };
210
211 /*
212 * cache operations
213 */
214 struct fscache_cache_ops {
215 /* name of cache provider */
216 const char *name;
217
218 /* allocate an object record for a cookie */
219 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
220 struct fscache_cookie *cookie);
221
222 /* look up the object for a cookie
223 * - return -ETIMEDOUT to be requeued
224 */
225 int (*lookup_object)(struct fscache_object *object);
226
227 /* finished looking up */
228 void (*lookup_complete)(struct fscache_object *object);
229
230 /* increment the usage count on this object (may fail if unmounting) */
231 struct fscache_object *(*grab_object)(struct fscache_object *object);
232
233 /* pin an object in the cache */
234 int (*pin_object)(struct fscache_object *object);
235
236 /* unpin an object in the cache */
237 void (*unpin_object)(struct fscache_object *object);
238
239 /* store the updated auxiliary data on an object */
240 void (*update_object)(struct fscache_object *object);
241
242 /* discard the resources pinned by an object and effect retirement if
243 * necessary */
244 void (*drop_object)(struct fscache_object *object);
245
246 /* dispose of a reference to an object */
247 void (*put_object)(struct fscache_object *object);
248
249 /* sync a cache */
250 void (*sync_cache)(struct fscache_cache *cache);
251
252 /* notification that the attributes of a non-index object (such as
253 * i_size) have changed */
254 int (*attr_changed)(struct fscache_object *object);
255
256 /* reserve space for an object's data and associated metadata */
257 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
258
259 /* request a backing block for a page be read or allocated in the
260 * cache */
261 fscache_page_retrieval_func_t read_or_alloc_page;
262
263 /* request backing blocks for a list of pages be read or allocated in
264 * the cache */
265 fscache_pages_retrieval_func_t read_or_alloc_pages;
266
267 /* request a backing block for a page be allocated in the cache so that
268 * it can be written directly */
269 fscache_page_retrieval_func_t allocate_page;
270
271 /* request backing blocks for pages be allocated in the cache so that
272 * they can be written directly */
273 fscache_pages_retrieval_func_t allocate_pages;
274
275 /* write a page to its backing block in the cache */
276 int (*write_page)(struct fscache_storage *op, struct page *page);
277
278 /* detach backing block from a page (optional)
279 * - must release the cookie lock before returning
280 * - may sleep
281 */
282 void (*uncache_page)(struct fscache_object *object,
283 struct page *page);
284
285 /* dissociate a cache from all the pages it was backing */
286 void (*dissociate_pages)(struct fscache_cache *cache);
287 };
288
289 /*
290 * data file or index object cookie
291 * - a file will only appear in one cache
292 * - a request to cache a file may or may not be honoured, subject to
293 * constraints such as disk space
294 * - indices are created on disk just-in-time
295 */
296 struct fscache_cookie {
297 atomic_t usage; /* number of users of this cookie */
298 atomic_t n_children; /* number of children of this cookie */
299 spinlock_t lock;
300 spinlock_t stores_lock; /* lock on page store tree */
301 struct hlist_head backing_objects; /* object(s) backing this file/index */
302 const struct fscache_cookie_def *def; /* definition */
303 struct fscache_cookie *parent; /* parent of this entry */
304 void *netfs_data; /* back pointer to netfs */
305 struct radix_tree_root stores; /* pages to be stored on this cookie */
306 #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
307 #define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
308
309 unsigned long flags;
310 #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
311 #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
312 #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
313 #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
314 #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
315 #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
316 };
317
318 extern struct fscache_cookie fscache_fsdef_index;
319
320 /*
321 * on-disk cache file or index handle
322 */
323 struct fscache_object {
324 enum fscache_object_state {
325 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
326 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
327 FSCACHE_OBJECT_CREATING, /* creating object */
328
329 /* active states */
330 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
331 FSCACHE_OBJECT_ACTIVE, /* object is usable */
332 FSCACHE_OBJECT_UPDATING, /* object is updating */
333
334 /* terminal states */
335 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
336 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
337 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
338 FSCACHE_OBJECT_RELEASING, /* releasing object */
339 FSCACHE_OBJECT_RECYCLING, /* retiring object */
340 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
341 FSCACHE_OBJECT_DEAD, /* object is now dead */
342 FSCACHE_OBJECT__NSTATES
343 } state;
344
345 int debug_id; /* debugging ID */
346 int n_children; /* number of child objects */
347 int n_ops; /* number of ops outstanding on object */
348 int n_obj_ops; /* number of object ops outstanding on object */
349 int n_in_progress; /* number of ops in progress */
350 int n_exclusive; /* number of exclusive ops queued */
351 atomic_t n_reads; /* number of read ops in progress */
352 spinlock_t lock; /* state and operations lock */
353
354 unsigned long lookup_jif; /* time at which lookup started */
355 unsigned long event_mask; /* events this object is interested in */
356 unsigned long events; /* events to be processed by this object
357 * (order is important - using fls) */
358 #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
359 #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
360 #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
361 #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
362 #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
363 #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
364 #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
365 #define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
366
367 unsigned long flags;
368 #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
369 #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
370 #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
371
372 struct list_head cache_link; /* link in cache->object_list */
373 struct hlist_node cookie_link; /* link in cookie->backing_objects */
374 struct fscache_cache *cache; /* cache that supplied this object */
375 struct fscache_cookie *cookie; /* netfs's file/index object */
376 struct fscache_object *parent; /* parent object */
377 struct work_struct work; /* attention scheduling record */
378 struct list_head dependents; /* FIFO of dependent objects */
379 struct list_head dep_link; /* link in parent's dependents list */
380 struct list_head pending_ops; /* unstarted operations on this object */
381 #ifdef CONFIG_FSCACHE_OBJECT_LIST
382 struct rb_node objlist_link; /* link in global object list */
383 #endif
384 pgoff_t store_limit; /* current storage limit */
385 loff_t store_limit_l; /* current storage limit */
386 };
387
388 extern const char *fscache_object_states[];
389
390 #define fscache_object_is_active(obj) \
391 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
392 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
393 (obj)->state < FSCACHE_OBJECT_DYING)
394
395 #define fscache_object_is_dead(obj) \
396 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
397 (obj)->state >= FSCACHE_OBJECT_DYING)
398
399 extern void fscache_object_work_func(struct work_struct *work);
400
401 /**
402 * fscache_object_init - Initialise a cache object description
403 * @object: Object description
404 *
405 * Initialise a cache object description to its basic values.
406 *
407 * See Documentation/filesystems/caching/backend-api.txt for a complete
408 * description.
409 */
410 static inline
fscache_object_init(struct fscache_object * object,struct fscache_cookie * cookie,struct fscache_cache * cache)411 void fscache_object_init(struct fscache_object *object,
412 struct fscache_cookie *cookie,
413 struct fscache_cache *cache)
414 {
415 atomic_inc(&cache->object_count);
416
417 object->state = FSCACHE_OBJECT_INIT;
418 spin_lock_init(&object->lock);
419 INIT_LIST_HEAD(&object->cache_link);
420 INIT_HLIST_NODE(&object->cookie_link);
421 INIT_WORK(&object->work, fscache_object_work_func);
422 INIT_LIST_HEAD(&object->dependents);
423 INIT_LIST_HEAD(&object->dep_link);
424 INIT_LIST_HEAD(&object->pending_ops);
425 object->n_children = 0;
426 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
427 object->events = object->event_mask = 0;
428 object->flags = 0;
429 object->store_limit = 0;
430 object->store_limit_l = 0;
431 object->cache = cache;
432 object->cookie = cookie;
433 object->parent = NULL;
434 }
435
436 extern void fscache_object_lookup_negative(struct fscache_object *object);
437 extern void fscache_obtained_object(struct fscache_object *object);
438
439 #ifdef CONFIG_FSCACHE_OBJECT_LIST
440 extern void fscache_object_destroy(struct fscache_object *object);
441 #else
442 #define fscache_object_destroy(object) do {} while(0)
443 #endif
444
445 /**
446 * fscache_object_destroyed - Note destruction of an object in a cache
447 * @cache: The cache from which the object came
448 *
449 * Note the destruction and deallocation of an object record in a cache.
450 */
fscache_object_destroyed(struct fscache_cache * cache)451 static inline void fscache_object_destroyed(struct fscache_cache *cache)
452 {
453 if (atomic_dec_and_test(&cache->object_count))
454 wake_up_all(&fscache_cache_cleared_wq);
455 }
456
457 /**
458 * fscache_object_lookup_error - Note an object encountered an error
459 * @object: The object on which the error was encountered
460 *
461 * Note that an object encountered a fatal error (usually an I/O error) and
462 * that it should be withdrawn as soon as possible.
463 */
fscache_object_lookup_error(struct fscache_object * object)464 static inline void fscache_object_lookup_error(struct fscache_object *object)
465 {
466 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
467 }
468
469 /**
470 * fscache_set_store_limit - Set the maximum size to be stored in an object
471 * @object: The object to set the maximum on
472 * @i_size: The limit to set in bytes
473 *
474 * Set the maximum size an object is permitted to reach, implying the highest
475 * byte that may be written. Intended to be called by the attr_changed() op.
476 *
477 * See Documentation/filesystems/caching/backend-api.txt for a complete
478 * description.
479 */
480 static inline
fscache_set_store_limit(struct fscache_object * object,loff_t i_size)481 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
482 {
483 object->store_limit_l = i_size;
484 object->store_limit = i_size >> PAGE_SHIFT;
485 if (i_size & ~PAGE_MASK)
486 object->store_limit++;
487 }
488
489 /**
490 * fscache_end_io - End a retrieval operation on a page
491 * @op: The FS-Cache operation covering the retrieval
492 * @page: The page that was to be fetched
493 * @error: The error code (0 if successful)
494 *
495 * Note the end of an operation to retrieve a page, as covered by a particular
496 * operation record.
497 */
fscache_end_io(struct fscache_retrieval * op,struct page * page,int error)498 static inline void fscache_end_io(struct fscache_retrieval *op,
499 struct page *page, int error)
500 {
501 op->end_io_func(page, op->context, error);
502 }
503
504 /*
505 * out-of-line cache backend functions
506 */
507 extern void fscache_init_cache(struct fscache_cache *cache,
508 const struct fscache_cache_ops *ops,
509 const char *idfmt,
510 ...) __attribute__ ((format (printf, 3, 4)));
511
512 extern int fscache_add_cache(struct fscache_cache *cache,
513 struct fscache_object *fsdef,
514 const char *tagname);
515 extern void fscache_withdraw_cache(struct fscache_cache *cache);
516
517 extern void fscache_io_error(struct fscache_cache *cache);
518
519 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
520 struct pagevec *pagevec);
521
522 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
523
524 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
525 const void *data,
526 uint16_t datalen);
527
528 #endif /* _LINUX_FSCACHE_CACHE_H */
529