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David Howells0dfc41d2009-04-03 16:42:36 +01001/* 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>
Tejun Heo8b8edef2010-07-20 22:09:01 +020023#include <linux/workqueue.h>
David Howells0dfc41d2009-04-03 16:42:36 +010024
25#define NR_MAXCACHES BITS_PER_LONG
26
27struct fscache_cache;
28struct fscache_cache_ops;
29struct fscache_object;
30struct fscache_operation;
31
David Howells0dfc41d2009-04-03 16:42:36 +010032/*
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65#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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);
77
78struct fscache_operation {
Tejun Heo8af7c122010-07-20 22:09:01 +020079 struct work_struct work; /* record for async ops */
David Howells0dfc41d2009-04-03 16:42:36 +010080 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 */
Tejun Heo8af7c122010-07-20 22:09:01 +020085#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 */
David Howells0dfc41d2009-04-03 16:42:36 +010087#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 */
David Howells4fbf4292009-11-19 18:11:04 +000090#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 */
David Howells0dfc41d2009-04-03 16:42:36 +010092
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
105extern atomic_t fscache_op_debug_id;
Tejun Heo8af7c122010-07-20 22:09:01 +0200106extern void fscache_op_work_func(struct work_struct *work);
David Howells0dfc41d2009-04-03 16:42:36 +0100107
108extern void fscache_enqueue_operation(struct fscache_operation *);
109extern void fscache_put_operation(struct fscache_operation *);
110
111/**
112 * fscache_operation_init - Do basic initialisation of an operation
113 * @op: The operation to initialise
114 * @release: The release function to assign
115 *
116 * Do basic initialisation of an operation. The caller must still set flags,
Tejun Heo8af7c122010-07-20 22:09:01 +0200117 * object and processor if needed.
David Howells0dfc41d2009-04-03 16:42:36 +0100118 */
119static inline void fscache_operation_init(struct fscache_operation *op,
Tejun Heo8af7c122010-07-20 22:09:01 +0200120 fscache_operation_processor_t processor,
121 fscache_operation_release_t release)
David Howells0dfc41d2009-04-03 16:42:36 +0100122{
Tejun Heo8af7c122010-07-20 22:09:01 +0200123 INIT_WORK(&op->work, fscache_op_work_func);
David Howells0dfc41d2009-04-03 16:42:36 +0100124 atomic_set(&op->usage, 1);
125 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
Tejun Heo8af7c122010-07-20 22:09:01 +0200126 op->processor = processor;
David Howells0dfc41d2009-04-03 16:42:36 +0100127 op->release = release;
128 INIT_LIST_HEAD(&op->pend_link);
129}
130
David Howells0dfc41d2009-04-03 16:42:36 +0100131/*
132 * data read operation
133 */
134struct fscache_retrieval {
135 struct fscache_operation op;
136 struct address_space *mapping; /* netfs pages */
137 fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
138 void *context; /* netfs read context (pinned) */
139 struct list_head to_do; /* list of things to be done by the backend */
140 unsigned long start_time; /* time at which retrieval started */
141};
142
143typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
144 struct page *page,
145 gfp_t gfp);
146
147typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
148 struct list_head *pages,
149 unsigned *nr_pages,
150 gfp_t gfp);
151
152/**
153 * fscache_get_retrieval - Get an extra reference on a retrieval operation
154 * @op: The retrieval operation to get a reference on
155 *
156 * Get an extra reference on a retrieval operation.
157 */
158static inline
159struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
160{
161 atomic_inc(&op->op.usage);
162 return op;
163}
164
165/**
166 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
167 * @op: The retrieval operation affected
168 *
169 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
170 */
171static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
172{
173 fscache_enqueue_operation(&op->op);
174}
175
176/**
177 * fscache_put_retrieval - Drop a reference to a retrieval operation
178 * @op: The retrieval operation affected
179 *
180 * Drop a reference to a retrieval operation.
181 */
182static inline void fscache_put_retrieval(struct fscache_retrieval *op)
183{
184 fscache_put_operation(&op->op);
185}
186
187/*
188 * cached page storage work item
189 * - used to do three things:
190 * - batch writes to the cache
191 * - do cache writes asynchronously
192 * - defer writes until cache object lookup completion
193 */
194struct fscache_storage {
195 struct fscache_operation op;
196 pgoff_t store_limit; /* don't write more than this */
197};
198
199/*
200 * cache operations
201 */
202struct fscache_cache_ops {
203 /* name of cache provider */
204 const char *name;
205
206 /* allocate an object record for a cookie */
207 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
208 struct fscache_cookie *cookie);
209
David Howellsfee096d2009-11-19 18:12:05 +0000210 /* look up the object for a cookie
211 * - return -ETIMEDOUT to be requeued
212 */
213 int (*lookup_object)(struct fscache_object *object);
David Howells0dfc41d2009-04-03 16:42:36 +0100214
215 /* finished looking up */
216 void (*lookup_complete)(struct fscache_object *object);
217
218 /* increment the usage count on this object (may fail if unmounting) */
219 struct fscache_object *(*grab_object)(struct fscache_object *object);
220
221 /* pin an object in the cache */
222 int (*pin_object)(struct fscache_object *object);
223
224 /* unpin an object in the cache */
225 void (*unpin_object)(struct fscache_object *object);
226
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300227 /* store the updated auxiliary data on an object */
David Howells0dfc41d2009-04-03 16:42:36 +0100228 void (*update_object)(struct fscache_object *object);
229
230 /* discard the resources pinned by an object and effect retirement if
231 * necessary */
232 void (*drop_object)(struct fscache_object *object);
233
234 /* dispose of a reference to an object */
235 void (*put_object)(struct fscache_object *object);
236
237 /* sync a cache */
238 void (*sync_cache)(struct fscache_cache *cache);
239
240 /* notification that the attributes of a non-index object (such as
241 * i_size) have changed */
242 int (*attr_changed)(struct fscache_object *object);
243
244 /* reserve space for an object's data and associated metadata */
245 int (*reserve_space)(struct fscache_object *object, loff_t i_size);
246
247 /* request a backing block for a page be read or allocated in the
248 * cache */
249 fscache_page_retrieval_func_t read_or_alloc_page;
250
251 /* request backing blocks for a list of pages be read or allocated in
252 * the cache */
253 fscache_pages_retrieval_func_t read_or_alloc_pages;
254
255 /* request a backing block for a page be allocated in the cache so that
256 * it can be written directly */
257 fscache_page_retrieval_func_t allocate_page;
258
259 /* request backing blocks for pages be allocated in the cache so that
260 * they can be written directly */
261 fscache_pages_retrieval_func_t allocate_pages;
262
263 /* write a page to its backing block in the cache */
264 int (*write_page)(struct fscache_storage *op, struct page *page);
265
266 /* detach backing block from a page (optional)
267 * - must release the cookie lock before returning
268 * - may sleep
269 */
270 void (*uncache_page)(struct fscache_object *object,
271 struct page *page);
272
273 /* dissociate a cache from all the pages it was backing */
274 void (*dissociate_pages)(struct fscache_cache *cache);
275};
276
277/*
278 * data file or index object cookie
279 * - a file will only appear in one cache
280 * - a request to cache a file may or may not be honoured, subject to
281 * constraints such as disk space
282 * - indices are created on disk just-in-time
283 */
284struct fscache_cookie {
285 atomic_t usage; /* number of users of this cookie */
286 atomic_t n_children; /* number of children of this cookie */
287 spinlock_t lock;
David Howells1bccf512009-11-19 18:11:25 +0000288 spinlock_t stores_lock; /* lock on page store tree */
David Howells0dfc41d2009-04-03 16:42:36 +0100289 struct hlist_head backing_objects; /* object(s) backing this file/index */
290 const struct fscache_cookie_def *def; /* definition */
291 struct fscache_cookie *parent; /* parent of this entry */
292 void *netfs_data; /* back pointer to netfs */
293 struct radix_tree_root stores; /* pages to be stored on this cookie */
294#define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
David Howells201a1542009-11-19 18:11:35 +0000295#define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
David Howells0dfc41d2009-04-03 16:42:36 +0100296
297 unsigned long flags;
298#define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
299#define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
300#define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
301#define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
302#define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
303#define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
304};
305
306extern struct fscache_cookie fscache_fsdef_index;
307
308/*
309 * on-disk cache file or index handle
310 */
311struct fscache_object {
312 enum fscache_object_state {
313 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
314 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
315 FSCACHE_OBJECT_CREATING, /* creating object */
316
317 /* active states */
318 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
319 FSCACHE_OBJECT_ACTIVE, /* object is usable */
320 FSCACHE_OBJECT_UPDATING, /* object is updating */
321
322 /* terminal states */
323 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
324 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
325 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
326 FSCACHE_OBJECT_RELEASING, /* releasing object */
327 FSCACHE_OBJECT_RECYCLING, /* retiring object */
328 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
329 FSCACHE_OBJECT_DEAD, /* object is now dead */
David Howells440f0af2009-11-19 18:11:01 +0000330 FSCACHE_OBJECT__NSTATES
David Howells0dfc41d2009-04-03 16:42:36 +0100331 } state;
332
333 int debug_id; /* debugging ID */
334 int n_children; /* number of child objects */
335 int n_ops; /* number of ops outstanding on object */
336 int n_obj_ops; /* number of object ops outstanding on object */
337 int n_in_progress; /* number of ops in progress */
338 int n_exclusive; /* number of exclusive ops queued */
David Howells4fbf4292009-11-19 18:11:04 +0000339 atomic_t n_reads; /* number of read ops in progress */
David Howells0dfc41d2009-04-03 16:42:36 +0100340 spinlock_t lock; /* state and operations lock */
341
342 unsigned long lookup_jif; /* time at which lookup started */
343 unsigned long event_mask; /* events this object is interested in */
344 unsigned long events; /* events to be processed by this object
345 * (order is important - using fls) */
346#define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
347#define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
348#define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
349#define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
350#define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
351#define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
352#define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
David Howells4fbf4292009-11-19 18:11:04 +0000353#define FSCACHE_OBJECT_EVENTS_MASK 0x7f /* mask of all events*/
David Howells0dfc41d2009-04-03 16:42:36 +0100354
355 unsigned long flags;
356#define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
357#define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
358#define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
359
360 struct list_head cache_link; /* link in cache->object_list */
361 struct hlist_node cookie_link; /* link in cookie->backing_objects */
362 struct fscache_cache *cache; /* cache that supplied this object */
363 struct fscache_cookie *cookie; /* netfs's file/index object */
364 struct fscache_object *parent; /* parent object */
Tejun Heo8b8edef2010-07-20 22:09:01 +0200365 struct work_struct work; /* attention scheduling record */
David Howells0dfc41d2009-04-03 16:42:36 +0100366 struct list_head dependents; /* FIFO of dependent objects */
367 struct list_head dep_link; /* link in parent's dependents list */
368 struct list_head pending_ops; /* unstarted operations on this object */
David Howells4fbf4292009-11-19 18:11:04 +0000369#ifdef CONFIG_FSCACHE_OBJECT_LIST
370 struct rb_node objlist_link; /* link in global object list */
371#endif
David Howells0dfc41d2009-04-03 16:42:36 +0100372 pgoff_t store_limit; /* current storage limit */
David Howellsa17754f2009-11-19 18:11:52 +0000373 loff_t store_limit_l; /* current storage limit */
David Howells0dfc41d2009-04-03 16:42:36 +0100374};
375
376extern const char *fscache_object_states[];
377
378#define fscache_object_is_active(obj) \
379 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
380 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
381 (obj)->state < FSCACHE_OBJECT_DYING)
382
David Howells60d543c2009-11-19 18:11:45 +0000383#define fscache_object_is_dead(obj) \
384 (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
385 (obj)->state >= FSCACHE_OBJECT_DYING)
386
Tejun Heo8b8edef2010-07-20 22:09:01 +0200387extern void fscache_object_work_func(struct work_struct *work);
David Howells0dfc41d2009-04-03 16:42:36 +0100388
389/**
390 * fscache_object_init - Initialise a cache object description
391 * @object: Object description
392 *
393 * Initialise a cache object description to its basic values.
394 *
395 * See Documentation/filesystems/caching/backend-api.txt for a complete
396 * description.
397 */
398static inline
399void fscache_object_init(struct fscache_object *object,
400 struct fscache_cookie *cookie,
401 struct fscache_cache *cache)
402{
403 atomic_inc(&cache->object_count);
404
405 object->state = FSCACHE_OBJECT_INIT;
406 spin_lock_init(&object->lock);
407 INIT_LIST_HEAD(&object->cache_link);
408 INIT_HLIST_NODE(&object->cookie_link);
Tejun Heo8b8edef2010-07-20 22:09:01 +0200409 INIT_WORK(&object->work, fscache_object_work_func);
David Howells0dfc41d2009-04-03 16:42:36 +0100410 INIT_LIST_HEAD(&object->dependents);
411 INIT_LIST_HEAD(&object->dep_link);
412 INIT_LIST_HEAD(&object->pending_ops);
413 object->n_children = 0;
414 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
415 object->events = object->event_mask = 0;
416 object->flags = 0;
417 object->store_limit = 0;
David Howellsa17754f2009-11-19 18:11:52 +0000418 object->store_limit_l = 0;
David Howells0dfc41d2009-04-03 16:42:36 +0100419 object->cache = cache;
420 object->cookie = cookie;
421 object->parent = NULL;
422}
423
424extern void fscache_object_lookup_negative(struct fscache_object *object);
425extern void fscache_obtained_object(struct fscache_object *object);
426
David Howells4fbf4292009-11-19 18:11:04 +0000427#ifdef CONFIG_FSCACHE_OBJECT_LIST
428extern void fscache_object_destroy(struct fscache_object *object);
429#else
430#define fscache_object_destroy(object) do {} while(0)
431#endif
432
David Howells0dfc41d2009-04-03 16:42:36 +0100433/**
434 * fscache_object_destroyed - Note destruction of an object in a cache
435 * @cache: The cache from which the object came
436 *
437 * Note the destruction and deallocation of an object record in a cache.
438 */
439static inline void fscache_object_destroyed(struct fscache_cache *cache)
440{
441 if (atomic_dec_and_test(&cache->object_count))
442 wake_up_all(&fscache_cache_cleared_wq);
443}
444
445/**
446 * fscache_object_lookup_error - Note an object encountered an error
447 * @object: The object on which the error was encountered
448 *
449 * Note that an object encountered a fatal error (usually an I/O error) and
450 * that it should be withdrawn as soon as possible.
451 */
452static inline void fscache_object_lookup_error(struct fscache_object *object)
453{
454 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
455}
456
457/**
458 * fscache_set_store_limit - Set the maximum size to be stored in an object
459 * @object: The object to set the maximum on
460 * @i_size: The limit to set in bytes
461 *
462 * Set the maximum size an object is permitted to reach, implying the highest
463 * byte that may be written. Intended to be called by the attr_changed() op.
464 *
465 * See Documentation/filesystems/caching/backend-api.txt for a complete
466 * description.
467 */
468static inline
469void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
470{
David Howellsa17754f2009-11-19 18:11:52 +0000471 object->store_limit_l = i_size;
David Howells0dfc41d2009-04-03 16:42:36 +0100472 object->store_limit = i_size >> PAGE_SHIFT;
473 if (i_size & ~PAGE_MASK)
474 object->store_limit++;
475}
476
477/**
478 * fscache_end_io - End a retrieval operation on a page
479 * @op: The FS-Cache operation covering the retrieval
480 * @page: The page that was to be fetched
481 * @error: The error code (0 if successful)
482 *
483 * Note the end of an operation to retrieve a page, as covered by a particular
484 * operation record.
485 */
486static inline void fscache_end_io(struct fscache_retrieval *op,
487 struct page *page, int error)
488{
489 op->end_io_func(page, op->context, error);
490}
491
492/*
493 * out-of-line cache backend functions
494 */
495extern void fscache_init_cache(struct fscache_cache *cache,
496 const struct fscache_cache_ops *ops,
497 const char *idfmt,
498 ...) __attribute__ ((format (printf, 3, 4)));
499
500extern int fscache_add_cache(struct fscache_cache *cache,
501 struct fscache_object *fsdef,
502 const char *tagname);
503extern void fscache_withdraw_cache(struct fscache_cache *cache);
504
505extern void fscache_io_error(struct fscache_cache *cache);
506
507extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
508 struct pagevec *pagevec);
509
Tejun Heo8b8edef2010-07-20 22:09:01 +0200510extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
511
David Howells0dfc41d2009-04-03 16:42:36 +0100512extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
513 const void *data,
514 uint16_t datalen);
515
516#endif /* _LINUX_FSCACHE_CACHE_H */