aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/fscache-cache.h
blob: 184cbdfbcc992cc5e2dd234d8cc9a96162dcb68e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
/* General filesystem caching backing cache interface
 *
 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * NOTE!!! See:
 *
 *	Documentation/filesystems/caching/backend-api.txt
 *
 * for a description of the cache backend interface declared here.
 */

#ifndef _LINUX_FSCACHE_CACHE_H
#define _LINUX_FSCACHE_CACHE_H

#include <linux/fscache.h>
#include <linux/sched.h>
#include <linux/slow-work.h>

#define NR_MAXCACHES BITS_PER_LONG

struct fscache_cache;
struct fscache_cache_ops;
struct fscache_object;
struct fscache_operation;

/*
 * cache tag definition
 */
struct fscache_cache_tag {
	struct list_head	link;
	struct fscache_cache	*cache;		/* cache referred to by this tag */
	unsigned long		flags;
#define FSCACHE_TAG_RESERVED	0		/* T if tag is reserved for a cache */
	atomic_t		usage;
	char			name[0];	/* tag name */
};

/*
 * cache definition
 */
struct fscache_cache {
	const struct fscache_cache_ops *ops;
	struct fscache_cache_tag *tag;		/* tag representing this cache */
	struct kobject		*kobj;		/* system representation of this cache */
	struct list_head	link;		/* link in list of caches */
	size_t			max_index_size;	/* maximum size of index data */
	char			identifier[36];	/* cache label */

	/* node management */
	struct work_struct	op_gc;		/* operation garbage collector */
	struct list_head	object_list;	/* list of data/index objects */
	struct list_head	op_gc_list;	/* list of ops to be deleted */
	spinlock_t		object_list_lock;
	spinlock_t		op_gc_list_lock;
	atomic_t		object_count;	/* no. of live objects in this cache */
	struct fscache_object	*fsdef;		/* object for the fsdef index */
	unsigned long		flags;
#define FSCACHE_IOERROR		0	/* cache stopped on I/O error */
#define FSCACHE_CACHE_WITHDRAWN	1	/* cache has been withdrawn */
};

extern wait_queue_head_t fscache_cache_cleared_wq;

/*
 * operation to be applied to a cache object
 * - retrieval initiation operations are done in the context of the process
 *   that issued them, and not in an async thread pool
 */
typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);

struct fscache_operation {
	union {
		struct work_struct fast_work;	/* record for fast ops */
		struct slow_work slow_work;	/* record for (very) slow ops */
	};
	struct list_head	pend_link;	/* link in object->pending_ops */
	struct fscache_object	*object;	/* object to be operated upon */

	unsigned long		flags;
#define FSCACHE_OP_TYPE		0x000f	/* operation type */
#define FSCACHE_OP_FAST		0x0001	/* - fast op, processor may not sleep for disk */
#define FSCACHE_OP_SLOW		0x0002	/* - (very) slow op, processor may sleep for disk */
#define FSCACHE_OP_MYTHREAD	0x0003	/* - processing is done be issuing thread, not pool */
#define FSCACHE_OP_WAITING	4	/* cleared when op is woken */
#define FSCACHE_OP_EXCLUSIVE	5	/* exclusive op, other ops must wait */
#define FSCACHE_OP_DEAD		6	/* op is now dead */
#define FSCACHE_OP_DEC_READ_CNT	7	/* decrement object->n_reads on destruction */
#define FSCACHE_OP_KEEP_FLAGS	0xc0	/* flags to keep when repurposing an op */

	atomic_t		usage;
	unsigned		debug_id;	/* debugging ID */

	/* operation processor callback
	 * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
	 *   the op in a non-pool thread */
	fscache_operation_processor_t processor;

	/* operation releaser */
	fscache_operation_release_t release;

#ifdef CONFIG_SLOW_WORK_PROC
	const char *name;		/* operation name */
	const char *state;		/* operation state */
#define fscache_set_op_name(OP, N)	do { (OP)->name  = (N); } while(0)
#define fscache_set_op_state(OP, S)	do { (OP)->state = (S); } while(0)
#else
#define fscache_set_op_name(OP, N)	do { } while(0)
#define fscache_set_op_state(OP, S)	do { } while(0)
#endif
};

extern atomic_t fscache_op_debug_id;
extern const struct slow_work_ops fscache_op_slow_work_ops;

extern void fscache_enqueue_operation(struct fscache_operation *);
extern void fscache_put_operation(struct fscache_operation *);

/**
 * fscache_operation_init - Do basic initialisation of an operation
 * @op: The operation to initialise
 * @release: The release function to assign
 *
 * Do basic initialisation of an operation.  The caller must still set flags,
 * object, either fast_work or slow_work if necessary, and processor if needed.
 */
static inline void fscache_operation_init(struct fscache_operation *op,
					  fscache_operation_release_t release)
{
	atomic_set(&op->usage, 1);
	op->debug_id = atomic_inc_return(&fscache_op_debug_id);
	op->release = release;
	INIT_LIST_HEAD(&op->pend_link);
	fscache_set_op_state(op, "Init");
}

/**
 * fscache_operation_init_slow - Do additional initialisation of a slow op
 * @op: The operation to initialise
 * @processor: The processor function to assign
 *
 * Do additional initialisation of an operation as required for slow work.
 */
static inline
void fscache_operation_init_slow(struct fscache_operation *op,
				 fscache_operation_processor_t processor)
{
	op->processor = processor;
	slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
}

/*
 * data read operation
 */
struct fscache_retrieval {
	struct fscache_operation op;
	struct address_space	*mapping;	/* netfs pages */
	fscache_rw_complete_t	end_io_func;	/* function to call on I/O completion */
	void			*context;	/* netfs read context (pinned) */
	struct list_head	to_do;		/* list of things to be done by the backend */
	unsigned long		start_time;	/* time at which retrieval started */
};

typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
					     struct page *page,
					     gfp_t gfp);

typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
					      struct list_head *pages,
					      unsigned *nr_pages,
					      gfp_t gfp);

/**
 * fscache_get_retrieval - Get an extra reference on a retrieval operation
 * @op: The retrieval operation to get a reference on
 *
 * Get an extra reference on a retrieval operation.
 */
static inline
struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
{
	atomic_inc(&op->op.usage);
	return op;
}

/**
 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 * @op: The retrieval operation affected
 *
 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 */
static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
{
	fscache_enqueue_operation(&op->op);
}

/**
 * fscache_put_retrieval - Drop a reference to a retrieval operation
 * @op: The retrieval operation affected
 *
 * Drop a reference to a retrieval operation.
 */
static inline void fscache_put_retrieval(struct fscache_retrieval *op)
{
	fscache_put_operation(&op->op);
}

/*
 * cached page storage work item
 * - used to do three things:
 *   - batch writes to the cache
 *   - do cache writes asynchronously
 *   - defer writes until cache object lookup completion
 */
struct fscache_storage {
	struct fscache_operation op;
	pgoff_t			store_limit;	/* don't write more than this */
};

/*
 * cache operations
 */
struct fscache_cache_ops {
	/* name of cache provider */
	const char *name;

	/* allocate an object record for a cookie */
	struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
					       struct fscache_cookie *cookie);

	/* look up the object for a cookie */
	void (*lookup_object)(struct fscache_object *object);

	/* finished looking up */
	void (*lookup_complete)(struct fscache_object *object);

	/* increment the usage count on this object (may fail if unmounting) */
	struct fscache_object *(*grab_object)(struct fscache_object *object);

	/* pin an object in the cache */
	int (*pin_object)(struct fscache_object *object);

	/* unpin an object in the cache */
	void (*unpin_object)(struct fscache_object *object);

	/* store the updated auxilliary data on an object */
	void (*update_object)(struct fscache_object *object);

	/* discard the resources pinned by an object and effect retirement if
	 * necessary */
	void (*drop_object)(struct fscache_object *object);

	/* dispose of a reference to an object */
	void (*put_object)(struct fscache_object *object);

	/* sync a cache */
	void (*sync_cache)(struct fscache_cache *cache);

	/* notification that the attributes of a non-index object (such as
	 * i_size) have changed */
	int (*attr_changed)(struct fscache_object *object);

	/* reserve space for an object's data and associated metadata */
	int (*reserve_space)(struct fscache_object *object, loff_t i_size);

	/* request a backing block for a page be read or allocated in the
	 * cache */
	fscache_page_retrieval_func_t read_or_alloc_page;

	/* request backing blocks for a list of pages be read or allocated in
	 * the cache */
	fscache_pages_retrieval_func_t read_or_alloc_pages;

	/* request a backing block for a page be allocated in the cache so that
	 * it can be written directly */
	fscache_page_retrieval_func_t allocate_page;

	/* request backing blocks for pages be allocated in the cache so that
	 * they can be written directly */
	fscache_pages_retrieval_func_t allocate_pages;

	/* write a page to its backing block in the cache */
	int (*write_page)(struct fscache_storage *op, struct page *page);

	/* detach backing block from a page (optional)
	 * - must release the cookie lock before returning
	 * - may sleep
	 */
	void (*uncache_page)(struct fscache_object *object,
			     struct page *page);

	/* dissociate a cache from all the pages it was backing */
	void (*dissociate_pages)(struct fscache_cache *cache);
};

/*
 * data file or index object cookie
 * - a file will only appear in one cache
 * - a request to cache a file may or may not be honoured, subject to
 *   constraints such as disk space
 * - indices are created on disk just-in-time
 */
struct fscache_cookie {
	atomic_t			usage;		/* number of users of this cookie */
	atomic_t			n_children;	/* number of children of this cookie */
	spinlock_t			lock;
	struct hlist_head		backing_objects; /* object(s) backing this file/index */
	const struct fscache_cookie_def	*def;		/* definition */
	struct fscache_cookie		*parent;	/* parent of this entry */
	void				*netfs_data;	/* back pointer to netfs */
	struct radix_tree_root		stores;		/* pages to be stored on this cookie */
#define FSCACHE_COOKIE_PENDING_TAG	0		/* pages tag: pending write to cache */

	unsigned long			flags;
#define FSCACHE_COOKIE_LOOKING_UP	0	/* T if non-index cookie being looked up still */
#define FSCACHE_COOKIE_CREATING		1	/* T if non-index object being created still */
#define FSCACHE_COOKIE_NO_DATA_YET	2	/* T if new object with no cached data yet */
#define FSCACHE_COOKIE_PENDING_FILL	3	/* T if pending initial fill on object */
#define FSCACHE_COOKIE_FILLING		4	/* T if filling object incrementally */
#define FSCACHE_COOKIE_UNAVAILABLE	5	/* T if cookie is unavailable (error, etc) */
};

extern struct fscache_cookie fscache_fsdef_index;

/*
 * on-disk cache file or index handle
 */
struct fscache_object {
	enum fscache_object_state {
		FSCACHE_OBJECT_INIT,		/* object in initial unbound state */
		FSCACHE_OBJECT_LOOKING_UP,	/* looking up object */
		FSCACHE_OBJECT_CREATING,	/* creating object */

		/* active states */
		FSCACHE_OBJECT_AVAILABLE,	/* cleaning up object after creation */
		FSCACHE_OBJECT_ACTIVE,		/* object is usable */
		FSCACHE_OBJECT_UPDATING,	/* object is updating */

		/* terminal states */
		FSCACHE_OBJECT_DYING,		/* object waiting for accessors to finish */
		FSCACHE_OBJECT_LC_DYING,	/* object cleaning up after lookup/create */
		FSCACHE_OBJECT_ABORT_INIT,	/* abort the init state */
		FSCACHE_OBJECT_RELEASING,	/* releasing object */
		FSCACHE_OBJECT_RECYCLING,	/* retiring object */
		FSCACHE_OBJECT_WITHDRAWING,	/* withdrawing object */
		FSCACHE_OBJECT_DEAD,		/* object is now dead */
		FSCACHE_OBJECT__NSTATES
	} state;

	int			debug_id;	/* debugging ID */
	int			n_children;	/* number of child objects */
	int			n_ops;		/* number of ops outstanding on object */
	int			n_obj_ops;	/* number of object ops outstanding on object */
	int			n_in_progress;	/* number of ops in progress */
	int			n_exclusive;	/* number of exclusive ops queued */
	atomic_t		n_reads;	/* number of read ops in progress */
	spinlock_t		lock;		/* state and operations lock */

	unsigned long		lookup_jif;	/* time at which lookup started */
	unsigned long		event_mask;	/* events this object is interested in */
	unsigned long		events;		/* events to be processed by this object
						 * (order is important - using fls) */
#define FSCACHE_OBJECT_EV_REQUEUE	0	/* T if object should be requeued */
#define FSCACHE_OBJECT_EV_UPDATE	1	/* T if object should be updated */
#define FSCACHE_OBJECT_EV_CLEARED	2	/* T if accessors all gone */
#define FSCACHE_OBJECT_EV_ERROR		3	/* T if fatal error occurred during processing */
#define FSCACHE_OBJECT_EV_RELEASE	4	/* T if netfs requested object release */
#define FSCACHE_OBJECT_EV_RETIRE	5	/* T if netfs requested object retirement */
#define FSCACHE_OBJECT_EV_WITHDRAW	6	/* T if cache requested object withdrawal */
#define FSCACHE_OBJECT_EVENTS_MASK	0x7f	/* mask of all events*/

	unsigned long		flags;
#define FSCACHE_OBJECT_LOCK		0	/* T if object is busy being processed */
#define FSCACHE_OBJECT_PENDING_WRITE	1	/* T if object has pending write */
#define FSCACHE_OBJECT_WAITING		2	/* T if object is waiting on its parent */

	struct list_head	cache_link;	/* link in cache->object_list */
	struct hlist_node	cookie_link;	/* link in cookie->backing_objects */
	struct fscache_cache	*cache;		/* cache that supplied this object */
	struct fscache_cookie	*cookie;	/* netfs's file/index object */
	struct fscache_object	*parent;	/* parent object */
	struct slow_work	work;		/* attention scheduling record */
	struct list_head	dependents;	/* FIFO of dependent objects */
	struct list_head	dep_link;	/* link in parent's dependents list */
	struct list_head	pending_ops;	/* unstarted operations on this object */
#ifdef CONFIG_FSCACHE_OBJECT_LIST
	struct rb_node		objlist_link;	/* link in global object list */
#endif
	pgoff_t			store_limit;	/* current storage limit */
};

extern const char *fscache_object_states[];

#define fscache_object_is_active(obj)			      \
	(!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
	 (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&	      \
	 (obj)->state < FSCACHE_OBJECT_DYING)

extern const struct slow_work_ops fscache_object_slow_work_ops;

/**
 * fscache_object_init - Initialise a cache object description
 * @object: Object description
 *
 * Initialise a cache object description to its basic values.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
static inline
void fscache_object_init(struct fscache_object *object,
			 struct fscache_cookie *cookie,
			 struct fscache_cache *cache)
{
	atomic_inc(&cache->object_count);

	object->state = FSCACHE_OBJECT_INIT;
	spin_lock_init(&object->lock);
	INIT_LIST_HEAD(&object->cache_link);
	INIT_HLIST_NODE(&object->cookie_link);
	vslow_work_init(&object->work, &fscache_object_slow_work_ops);
	INIT_LIST_HEAD(&object->dependents);
	INIT_LIST_HEAD(&object->dep_link);
	INIT_LIST_HEAD(&object->pending_ops);
	object->n_children = 0;
	object->n_ops = object->n_in_progress = object->n_exclusive = 0;
	object->events = object->event_mask = 0;
	object->flags = 0;
	object->store_limit = 0;
	object->cache = cache;
	object->cookie = cookie;
	object->parent = NULL;
}

extern void fscache_object_lookup_negative(struct fscache_object *object);
extern void fscache_obtained_object(struct fscache_object *object);

#ifdef CONFIG_FSCACHE_OBJECT_LIST
extern void fscache_object_destroy(struct fscache_object *object);
#else
#define fscache_object_destroy(object) do {} while(0)
#endif

/**
 * fscache_object_destroyed - Note destruction of an object in a cache
 * @cache: The cache from which the object came
 *
 * Note the destruction and deallocation of an object record in a cache.
 */
static inline void fscache_object_destroyed(struct fscache_cache *cache)
{
	if (atomic_dec_and_test(&cache->object_count))
		wake_up_all(&fscache_cache_cleared_wq);
}

/**
 * fscache_object_lookup_error - Note an object encountered an error
 * @object: The object on which the error was encountered
 *
 * Note that an object encountered a fatal error (usually an I/O error) and
 * that it should be withdrawn as soon as possible.
 */
static inline void fscache_object_lookup_error(struct fscache_object *object)
{
	set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
}

/**
 * fscache_set_store_limit - Set the maximum size to be stored in an object
 * @object: The object to set the maximum on
 * @i_size: The limit to set in bytes
 *
 * Set the maximum size an object is permitted to reach, implying the highest
 * byte that may be written.  Intended to be called by the attr_changed() op.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
static inline
void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
{
	object->store_limit = i_size >> PAGE_SHIFT;
	if (i_size & ~PAGE_MASK)
		object->store_limit++;
}

/**
 * fscache_end_io - End a retrieval operation on a page
 * @op: The FS-Cache operation covering the retrieval
 * @page: The page that was to be fetched
 * @error: The error code (0 if successful)
 *
 * Note the end of an operation to retrieve a page, as covered by a particular
 * operation record.
 */
static inline void fscache_end_io(struct fscache_retrieval *op,
				  struct page *page, int error)
{
	op->end_io_func(page, op->context, error);
}

/*
 * out-of-line cache backend functions
 */
extern void fscache_init_cache(struct fscache_cache *cache,
			       const struct fscache_cache_ops *ops,
			       const char *idfmt,
			       ...) __attribute__ ((format (printf, 3, 4)));

extern int fscache_add_cache(struct fscache_cache *cache,
			     struct fscache_object *fsdef,
			     const char *tagname);
extern void fscache_withdraw_cache(struct fscache_cache *cache);

extern void fscache_io_error(struct fscache_cache *cache);

extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
				      struct pagevec *pagevec);

extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
					       const void *data,
					       uint16_t datalen);

#endif /* _LINUX_FSCACHE_CACHE_H */