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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>
23#include <linux/slow-work.h>
24
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65#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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 {
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
95 atomic_t usage;
96 unsigned debug_id; /* debugging ID */
97
98 /* operation processor callback
99 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
100 * the op in a non-pool thread */
101 fscache_operation_processor_t processor;
102
103 /* operation releaser */
104 fscache_operation_release_t release;
105};
106
107extern atomic_t fscache_op_debug_id;
108extern const struct slow_work_ops fscache_op_slow_work_ops;
109
110extern void fscache_enqueue_operation(struct fscache_operation *);
111extern void fscache_put_operation(struct fscache_operation *);
112
113/**
114 * fscache_operation_init - Do basic initialisation of an operation
115 * @op: The operation to initialise
116 * @release: The release function to assign
117 *
118 * Do basic initialisation of an operation. The caller must still set flags,
119 * object, either fast_work or slow_work if necessary, and processor if needed.
120 */
121static inline void fscache_operation_init(struct fscache_operation *op,
122 fscache_operation_release_t release)
123{
124 atomic_set(&op->usage, 1);
125 op->debug_id = atomic_inc_return(&fscache_op_debug_id);
126 op->release = release;
127 INIT_LIST_HEAD(&op->pend_link);
128}
129
130/**
131 * fscache_operation_init_slow - Do additional initialisation of a slow op
132 * @op: The operation to initialise
133 * @processor: The processor function to assign
134 *
135 * Do additional initialisation of an operation as required for slow work.
136 */
137static inline
138void fscache_operation_init_slow(struct fscache_operation *op,
139 fscache_operation_processor_t processor)
140{
141 op->processor = processor;
142 slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
143}
144
145/*
146 * data read operation
147 */
148struct fscache_retrieval {
149 struct fscache_operation op;
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};
156
157typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
158 struct page *page,
159 gfp_t gfp);
160
161typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
162 struct list_head *pages,
163 unsigned *nr_pages,
164 gfp_t gfp);
165
166/**
167 * fscache_get_retrieval - Get an extra reference on a retrieval operation
168 * @op: The retrieval operation to get a reference on
169 *
170 * Get an extra reference on a retrieval operation.
171 */
172static inline
173struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
174{
175 atomic_inc(&op->op.usage);
176 return op;
177}
178
179/**
180 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
181 * @op: The retrieval operation affected
182 *
183 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
184 */
185static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
186{
187 fscache_enqueue_operation(&op->op);
188}
189
190/**
191 * fscache_put_retrieval - Drop a reference to a retrieval operation
192 * @op: The retrieval operation affected
193 *
194 * Drop a reference to a retrieval operation.
195 */
196static inline void fscache_put_retrieval(struct fscache_retrieval *op)
197{
198 fscache_put_operation(&op->op);
199}
200
201/*
202 * cached page storage work item
203 * - used to do three things:
204 * - batch writes to the cache
205 * - do cache writes asynchronously
206 * - defer writes until cache object lookup completion
207 */
208struct fscache_storage {
209 struct fscache_operation op;
210 pgoff_t store_limit; /* don't write more than this */
211};
212
213/*
214 * cache operations
215 */
216struct fscache_cache_ops {
217 /* name of cache provider */
218 const char *name;
219
220 /* allocate an object record for a cookie */
221 struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
222 struct fscache_cookie *cookie);
223
224 /* look up the object for a cookie */
225 void (*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 auxilliary 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 */
296struct 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 struct hlist_head backing_objects; /* object(s) backing this file/index */
301 const struct fscache_cookie_def *def; /* definition */
302 struct fscache_cookie *parent; /* parent of this entry */
303 void *netfs_data; /* back pointer to netfs */
304 struct radix_tree_root stores; /* pages to be stored on this cookie */
305#define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
306
307 unsigned long flags;
308#define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
309#define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
310#define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
311#define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
312#define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
313#define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
314};
315
316extern struct fscache_cookie fscache_fsdef_index;
317
318/*
319 * on-disk cache file or index handle
320 */
321struct fscache_object {
322 enum fscache_object_state {
323 FSCACHE_OBJECT_INIT, /* object in initial unbound state */
324 FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
325 FSCACHE_OBJECT_CREATING, /* creating object */
326
327 /* active states */
328 FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
329 FSCACHE_OBJECT_ACTIVE, /* object is usable */
330 FSCACHE_OBJECT_UPDATING, /* object is updating */
331
332 /* terminal states */
333 FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
334 FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
335 FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
336 FSCACHE_OBJECT_RELEASING, /* releasing object */
337 FSCACHE_OBJECT_RECYCLING, /* retiring object */
338 FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
339 FSCACHE_OBJECT_DEAD, /* object is now dead */
340 } state;
341
342 int debug_id; /* debugging ID */
343 int n_children; /* number of child objects */
344 int n_ops; /* number of ops outstanding on object */
345 int n_obj_ops; /* number of object ops outstanding on object */
346 int n_in_progress; /* number of ops in progress */
347 int n_exclusive; /* number of exclusive ops queued */
348 spinlock_t lock; /* state and operations lock */
349
350 unsigned long lookup_jif; /* time at which lookup started */
351 unsigned long event_mask; /* events this object is interested in */
352 unsigned long events; /* events to be processed by this object
353 * (order is important - using fls) */
354#define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
355#define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
356#define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
357#define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
358#define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
359#define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
360#define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
361
362 unsigned long flags;
363#define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
364#define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
365#define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
366
367 struct list_head cache_link; /* link in cache->object_list */
368 struct hlist_node cookie_link; /* link in cookie->backing_objects */
369 struct fscache_cache *cache; /* cache that supplied this object */
370 struct fscache_cookie *cookie; /* netfs's file/index object */
371 struct fscache_object *parent; /* parent object */
372 struct slow_work work; /* attention scheduling record */
373 struct list_head dependents; /* FIFO of dependent objects */
374 struct list_head dep_link; /* link in parent's dependents list */
375 struct list_head pending_ops; /* unstarted operations on this object */
376 pgoff_t store_limit; /* current storage limit */
377};
378
379extern const char *fscache_object_states[];
380
381#define fscache_object_is_active(obj) \
382 (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
383 (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
384 (obj)->state < FSCACHE_OBJECT_DYING)
385
386extern const struct slow_work_ops fscache_object_slow_work_ops;
387
388/**
389 * fscache_object_init - Initialise a cache object description
390 * @object: Object description
391 *
392 * Initialise a cache object description to its basic values.
393 *
394 * See Documentation/filesystems/caching/backend-api.txt for a complete
395 * description.
396 */
397static inline
398void fscache_object_init(struct fscache_object *object,
399 struct fscache_cookie *cookie,
400 struct fscache_cache *cache)
401{
402 atomic_inc(&cache->object_count);
403
404 object->state = FSCACHE_OBJECT_INIT;
405 spin_lock_init(&object->lock);
406 INIT_LIST_HEAD(&object->cache_link);
407 INIT_HLIST_NODE(&object->cookie_link);
408 vslow_work_init(&object->work, &fscache_object_slow_work_ops);
409 INIT_LIST_HEAD(&object->dependents);
410 INIT_LIST_HEAD(&object->dep_link);
411 INIT_LIST_HEAD(&object->pending_ops);
412 object->n_children = 0;
413 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
414 object->events = object->event_mask = 0;
415 object->flags = 0;
416 object->store_limit = 0;
417 object->cache = cache;
418 object->cookie = cookie;
419 object->parent = NULL;
420}
421
422extern void fscache_object_lookup_negative(struct fscache_object *object);
423extern void fscache_obtained_object(struct fscache_object *object);
424
425/**
426 * fscache_object_destroyed - Note destruction of an object in a cache
427 * @cache: The cache from which the object came
428 *
429 * Note the destruction and deallocation of an object record in a cache.
430 */
431static inline void fscache_object_destroyed(struct fscache_cache *cache)
432{
433 if (atomic_dec_and_test(&cache->object_count))
434 wake_up_all(&fscache_cache_cleared_wq);
435}
436
437/**
438 * fscache_object_lookup_error - Note an object encountered an error
439 * @object: The object on which the error was encountered
440 *
441 * Note that an object encountered a fatal error (usually an I/O error) and
442 * that it should be withdrawn as soon as possible.
443 */
444static inline void fscache_object_lookup_error(struct fscache_object *object)
445{
446 set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
447}
448
449/**
450 * fscache_set_store_limit - Set the maximum size to be stored in an object
451 * @object: The object to set the maximum on
452 * @i_size: The limit to set in bytes
453 *
454 * Set the maximum size an object is permitted to reach, implying the highest
455 * byte that may be written. Intended to be called by the attr_changed() op.
456 *
457 * See Documentation/filesystems/caching/backend-api.txt for a complete
458 * description.
459 */
460static inline
461void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
462{
463 object->store_limit = i_size >> PAGE_SHIFT;
464 if (i_size & ~PAGE_MASK)
465 object->store_limit++;
466}
467
468/**
469 * fscache_end_io - End a retrieval operation on a page
470 * @op: The FS-Cache operation covering the retrieval
471 * @page: The page that was to be fetched
472 * @error: The error code (0 if successful)
473 *
474 * Note the end of an operation to retrieve a page, as covered by a particular
475 * operation record.
476 */
477static inline void fscache_end_io(struct fscache_retrieval *op,
478 struct page *page, int error)
479{
480 op->end_io_func(page, op->context, error);
481}
482
483/*
484 * out-of-line cache backend functions
485 */
486extern void fscache_init_cache(struct fscache_cache *cache,
487 const struct fscache_cache_ops *ops,
488 const char *idfmt,
489 ...) __attribute__ ((format (printf, 3, 4)));
490
491extern int fscache_add_cache(struct fscache_cache *cache,
492 struct fscache_object *fsdef,
493 const char *tagname);
494extern void fscache_withdraw_cache(struct fscache_cache *cache);
495
496extern void fscache_io_error(struct fscache_cache *cache);
497
498extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
499 struct pagevec *pagevec);
500
501extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
502 const void *data,
503 uint16_t datalen);
504
505#endif /* _LINUX_FSCACHE_CACHE_H */