summaryrefslogtreecommitdiff
path: root/drivers/md/dm-region-hash.c
blob: 462cb24ba92e444a5efb720eb3df98ad21626938 (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
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2003 Sistina Software Limited.
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include <linux/dm-dirty-log.h>
#include <linux/dm-region-hash.h>

#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include "dm.h"

#define	DM_MSG_PREFIX	"region hash"

/*-----------------------------------------------------------------
 * Region hash
 *
 * The mirror splits itself up into discrete regions.  Each
 * region can be in one of three states: clean, dirty,
 * nosync.  There is no need to put clean regions in the hash.
 *
 * In addition to being present in the hash table a region _may_
 * be present on one of three lists.
 *
 *   clean_regions: Regions on this list have no io pending to
 *   them, they are in sync, we are no longer interested in them,
 *   they are dull.  dm_rh_update_states() will remove them from the
 *   hash table.
 *
 *   quiesced_regions: These regions have been spun down, ready
 *   for recovery.  rh_recovery_start() will remove regions from
 *   this list and hand them to kmirrord, which will schedule the
 *   recovery io with kcopyd.
 *
 *   recovered_regions: Regions that kcopyd has successfully
 *   recovered.  dm_rh_update_states() will now schedule any delayed
 *   io, up the recovery_count, and remove the region from the
 *   hash.
 *
 * There are 2 locks:
 *   A rw spin lock 'hash_lock' protects just the hash table,
 *   this is never held in write mode from interrupt context,
 *   which I believe means that we only have to disable irqs when
 *   doing a write lock.
 *
 *   An ordinary spin lock 'region_lock' that protects the three
 *   lists in the region_hash, with the 'state', 'list' and
 *   'delayed_bios' fields of the regions.  This is used from irq
 *   context, so all other uses will have to suspend local irqs.
 *---------------------------------------------------------------*/
struct dm_region_hash {
	uint32_t region_size;
	unsigned int region_shift;

	/* holds persistent region state */
	struct dm_dirty_log *log;

	/* hash table */
	rwlock_t hash_lock;
	unsigned int mask;
	unsigned int nr_buckets;
	unsigned int prime;
	unsigned int shift;
	struct list_head *buckets;

	/*
	 * If there was a flush failure no regions can be marked clean.
	 */
	int flush_failure;

	unsigned int max_recovery; /* Max # of regions to recover in parallel */

	spinlock_t region_lock;
	atomic_t recovery_in_flight;
	struct list_head clean_regions;
	struct list_head quiesced_regions;
	struct list_head recovered_regions;
	struct list_head failed_recovered_regions;
	struct semaphore recovery_count;

	mempool_t region_pool;

	void *context;
	sector_t target_begin;

	/* Callback function to schedule bios writes */
	void (*dispatch_bios)(void *context, struct bio_list *bios);

	/* Callback function to wakeup callers worker thread. */
	void (*wakeup_workers)(void *context);

	/* Callback function to wakeup callers recovery waiters. */
	void (*wakeup_all_recovery_waiters)(void *context);
};

struct dm_region {
	struct dm_region_hash *rh;	/* FIXME: can we get rid of this ? */
	region_t key;
	int state;

	struct list_head hash_list;
	struct list_head list;

	atomic_t pending;
	struct bio_list delayed_bios;
};

/*
 * Conversion fns
 */
static region_t dm_rh_sector_to_region(struct dm_region_hash *rh, sector_t sector)
{
	return sector >> rh->region_shift;
}

sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region)
{
	return region << rh->region_shift;
}
EXPORT_SYMBOL_GPL(dm_rh_region_to_sector);

region_t dm_rh_bio_to_region(struct dm_region_hash *rh, struct bio *bio)
{
	return dm_rh_sector_to_region(rh, bio->bi_iter.bi_sector -
				      rh->target_begin);
}
EXPORT_SYMBOL_GPL(dm_rh_bio_to_region);

void *dm_rh_region_context(struct dm_region *reg)
{
	return reg->rh->context;
}
EXPORT_SYMBOL_GPL(dm_rh_region_context);

region_t dm_rh_get_region_key(struct dm_region *reg)
{
	return reg->key;
}
EXPORT_SYMBOL_GPL(dm_rh_get_region_key);

sector_t dm_rh_get_region_size(struct dm_region_hash *rh)
{
	return rh->region_size;
}
EXPORT_SYMBOL_GPL(dm_rh_get_region_size);

/*
 * FIXME: shall we pass in a structure instead of all these args to
 * dm_region_hash_create()????
 */
#define RH_HASH_MULT 2654435387U
#define RH_HASH_SHIFT 12

#define MIN_REGIONS 64
struct dm_region_hash *dm_region_hash_create(
		void *context, void (*dispatch_bios)(void *context,
						     struct bio_list *bios),
		void (*wakeup_workers)(void *context),
		void (*wakeup_all_recovery_waiters)(void *context),
		sector_t target_begin, unsigned int max_recovery,
		struct dm_dirty_log *log, uint32_t region_size,
		region_t nr_regions)
{
	struct dm_region_hash *rh;
	unsigned int nr_buckets, max_buckets;
	size_t i;
	int ret;

	/*
	 * Calculate a suitable number of buckets for our hash
	 * table.
	 */
	max_buckets = nr_regions >> 6;
	for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1)
		;
	nr_buckets >>= 1;

	rh = kzalloc(sizeof(*rh), GFP_KERNEL);
	if (!rh) {
		DMERR("unable to allocate region hash memory");
		return ERR_PTR(-ENOMEM);
	}

	rh->context = context;
	rh->dispatch_bios = dispatch_bios;
	rh->wakeup_workers = wakeup_workers;
	rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters;
	rh->target_begin = target_begin;
	rh->max_recovery = max_recovery;
	rh->log = log;
	rh->region_size = region_size;
	rh->region_shift = __ffs(region_size);
	rwlock_init(&rh->hash_lock);
	rh->mask = nr_buckets - 1;
	rh->nr_buckets = nr_buckets;

	rh->shift = RH_HASH_SHIFT;
	rh->prime = RH_HASH_MULT;

	rh->buckets = vmalloc(array_size(nr_buckets, sizeof(*rh->buckets)));
	if (!rh->buckets) {
		DMERR("unable to allocate region hash bucket memory");
		kfree(rh);
		return ERR_PTR(-ENOMEM);
	}

	for (i = 0; i < nr_buckets; i++)
		INIT_LIST_HEAD(rh->buckets + i);

	spin_lock_init(&rh->region_lock);
	sema_init(&rh->recovery_count, 0);
	atomic_set(&rh->recovery_in_flight, 0);
	INIT_LIST_HEAD(&rh->clean_regions);
	INIT_LIST_HEAD(&rh->quiesced_regions);
	INIT_LIST_HEAD(&rh->recovered_regions);
	INIT_LIST_HEAD(&rh->failed_recovered_regions);
	rh->flush_failure = 0;

	ret = mempool_init_kmalloc_pool(&rh->region_pool, MIN_REGIONS,
					sizeof(struct dm_region));
	if (ret) {
		vfree(rh->buckets);
		kfree(rh);
		rh = ERR_PTR(-ENOMEM);
	}

	return rh;
}
EXPORT_SYMBOL_GPL(dm_region_hash_create);

void dm_region_hash_destroy(struct dm_region_hash *rh)
{
	unsigned int h;
	struct dm_region *reg, *nreg;

	BUG_ON(!list_empty(&rh->quiesced_regions));
	for (h = 0; h < rh->nr_buckets; h++) {
		list_for_each_entry_safe(reg, nreg, rh->buckets + h,
					 hash_list) {
			BUG_ON(atomic_read(&reg->pending));
			mempool_free(reg, &rh->region_pool);
		}
	}

	if (rh->log)
		dm_dirty_log_destroy(rh->log);

	mempool_exit(&rh->region_pool);
	vfree(rh->buckets);
	kfree(rh);
}
EXPORT_SYMBOL_GPL(dm_region_hash_destroy);

struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh)
{
	return rh->log;
}
EXPORT_SYMBOL_GPL(dm_rh_dirty_log);

static unsigned int rh_hash(struct dm_region_hash *rh, region_t region)
{
	return (unsigned int) ((region * rh->prime) >> rh->shift) & rh->mask;
}

static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region)
{
	struct dm_region *reg;
	struct list_head *bucket = rh->buckets + rh_hash(rh, region);

	list_for_each_entry(reg, bucket, hash_list)
		if (reg->key == region)
			return reg;

	return NULL;
}

static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg)
{
	list_add(&reg->hash_list, rh->buckets + rh_hash(rh, reg->key));
}

static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
{
	struct dm_region *reg, *nreg;

	nreg = mempool_alloc(&rh->region_pool, GFP_ATOMIC);
	if (unlikely(!nreg))
		nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);

	nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
		      DM_RH_CLEAN : DM_RH_NOSYNC;
	nreg->rh = rh;
	nreg->key = region;
	INIT_LIST_HEAD(&nreg->list);
	atomic_set(&nreg->pending, 0);
	bio_list_init(&nreg->delayed_bios);

	write_lock_irq(&rh->hash_lock);
	reg = __rh_lookup(rh, region);
	if (reg)
		/* We lost the race. */
		mempool_free(nreg, &rh->region_pool);
	else {
		__rh_insert(rh, nreg);
		if (nreg->state == DM_RH_CLEAN) {
			spin_lock(&rh->region_lock);
			list_add(&nreg->list, &rh->clean_regions);
			spin_unlock(&rh->region_lock);
		}

		reg = nreg;
	}
	write_unlock_irq(&rh->hash_lock);

	return reg;
}

static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region)
{
	struct dm_region *reg;

	reg = __rh_lookup(rh, region);
	if (!reg) {
		read_unlock(&rh->hash_lock);
		reg = __rh_alloc(rh, region);
		read_lock(&rh->hash_lock);
	}

	return reg;
}

int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block)
{
	int r;
	struct dm_region *reg;

	read_lock(&rh->hash_lock);
	reg = __rh_lookup(rh, region);
	read_unlock(&rh->hash_lock);

	if (reg)
		return reg->state;

	/*
	 * The region wasn't in the hash, so we fall back to the
	 * dirty log.
	 */
	r = rh->log->type->in_sync(rh->log, region, may_block);

	/*
	 * Any error from the dirty log (eg. -EWOULDBLOCK) gets
	 * taken as a DM_RH_NOSYNC
	 */
	return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC;
}
EXPORT_SYMBOL_GPL(dm_rh_get_state);

static void complete_resync_work(struct dm_region *reg, int success)
{
	struct dm_region_hash *rh = reg->rh;

	rh->log->type->set_region_sync(rh->log, reg->key, success);

	/*
	 * Dispatch the bios before we call 'wake_up_all'.
	 * This is important because if we are suspending,
	 * we want to know that recovery is complete and
	 * the work queue is flushed.  If we wake_up_all
	 * before we dispatch_bios (queue bios and call wake()),
	 * then we risk suspending before the work queue
	 * has been properly flushed.
	 */
	rh->dispatch_bios(rh->context, &reg->delayed_bios);
	if (atomic_dec_and_test(&rh->recovery_in_flight))
		rh->wakeup_all_recovery_waiters(rh->context);
	up(&rh->recovery_count);
}

/* dm_rh_mark_nosync
 * @ms
 * @bio
 *
 * The bio was written on some mirror(s) but failed on other mirror(s).
 * We can successfully endio the bio but should avoid the region being
 * marked clean by setting the state DM_RH_NOSYNC.
 *
 * This function is _not_ safe in interrupt context!
 */
void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio)
{
	unsigned long flags;
	struct dm_dirty_log *log = rh->log;
	struct dm_region *reg;
	region_t region = dm_rh_bio_to_region(rh, bio);
	int recovering = 0;

	if (bio->bi_opf & REQ_PREFLUSH) {
		rh->flush_failure = 1;
		return;
	}

	if (bio_op(bio) == REQ_OP_DISCARD)
		return;

	/* We must inform the log that the sync count has changed. */
	log->type->set_region_sync(log, region, 0);

	read_lock(&rh->hash_lock);
	reg = __rh_find(rh, region);
	read_unlock(&rh->hash_lock);

	/* region hash entry should exist because write was in-flight */
	BUG_ON(!reg);
	BUG_ON(!list_empty(&reg->list));

	spin_lock_irqsave(&rh->region_lock, flags);
	/*
	 * Possible cases:
	 *   1) DM_RH_DIRTY
	 *   2) DM_RH_NOSYNC: was dirty, other preceding writes failed
	 *   3) DM_RH_RECOVERING: flushing pending writes
	 * Either case, the region should have not been connected to list.
	 */
	recovering = (reg->state == DM_RH_RECOVERING);
	reg->state = DM_RH_NOSYNC;
	BUG_ON(!list_empty(&reg->list));
	spin_unlock_irqrestore(&rh->region_lock, flags);

	if (recovering)
		complete_resync_work(reg, 0);
}
EXPORT_SYMBOL_GPL(dm_rh_mark_nosync);

void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled)
{
	struct dm_region *reg, *next;

	LIST_HEAD(clean);
	LIST_HEAD(recovered);
	LIST_HEAD(failed_recovered);

	/*
	 * Quickly grab the lists.
	 */
	write_lock_irq(&rh->hash_lock);
	spin_lock(&rh->region_lock);
	if (!list_empty(&rh->clean_regions)) {
		list_splice_init(&rh->clean_regions, &clean);

		list_for_each_entry(reg, &clean, list)
			list_del(&reg->hash_list);
	}

	if (!list_empty(&rh->recovered_regions)) {
		list_splice_init(&rh->recovered_regions, &recovered);

		list_for_each_entry(reg, &recovered, list)
			list_del(&reg->hash_list);
	}

	if (!list_empty(&rh->failed_recovered_regions)) {
		list_splice_init(&rh->failed_recovered_regions,
				 &failed_recovered);

		list_for_each_entry(reg, &failed_recovered, list)
			list_del(&reg->hash_list);
	}

	spin_unlock(&rh->region_lock);
	write_unlock_irq(&rh->hash_lock);

	/*
	 * All the regions on the recovered and clean lists have
	 * now been pulled out of the system, so no need to do
	 * any more locking.
	 */
	list_for_each_entry_safe(reg, next, &recovered, list) {
		rh->log->type->clear_region(rh->log, reg->key);
		complete_resync_work(reg, 1);
		mempool_free(reg, &rh->region_pool);
	}

	list_for_each_entry_safe(reg, next, &failed_recovered, list) {
		complete_resync_work(reg, errors_handled ? 0 : 1);
		mempool_free(reg, &rh->region_pool);
	}

	list_for_each_entry_safe(reg, next, &clean, list) {
		rh->log->type->clear_region(rh->log, reg->key);
		mempool_free(reg, &rh->region_pool);
	}

	rh->log->type->flush(rh->log);
}
EXPORT_SYMBOL_GPL(dm_rh_update_states);

static void rh_inc(struct dm_region_hash *rh, region_t region)
{
	struct dm_region *reg;

	read_lock(&rh->hash_lock);
	reg = __rh_find(rh, region);

	spin_lock_irq(&rh->region_lock);
	atomic_inc(&reg->pending);

	if (reg->state == DM_RH_CLEAN) {
		reg->state = DM_RH_DIRTY;
		list_del_init(&reg->list);	/* take off the clean list */
		spin_unlock_irq(&rh->region_lock);

		rh->log->type->mark_region(rh->log, reg->key);
	} else
		spin_unlock_irq(&rh->region_lock);


	read_unlock(&rh->hash_lock);
}

void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios)
{
	struct bio *bio;

	for (bio = bios->head; bio; bio = bio->bi_next) {
		if (bio->bi_opf & REQ_PREFLUSH || bio_op(bio) == REQ_OP_DISCARD)
			continue;
		rh_inc(rh, dm_rh_bio_to_region(rh, bio));
	}
}
EXPORT_SYMBOL_GPL(dm_rh_inc_pending);

void dm_rh_dec(struct dm_region_hash *rh, region_t region)
{
	unsigned long flags;
	struct dm_region *reg;
	int should_wake = 0;

	read_lock(&rh->hash_lock);
	reg = __rh_lookup(rh, region);
	read_unlock(&rh->hash_lock);

	spin_lock_irqsave(&rh->region_lock, flags);
	if (atomic_dec_and_test(&reg->pending)) {
		/*
		 * There is no pending I/O for this region.
		 * We can move the region to corresponding list for next action.
		 * At this point, the region is not yet connected to any list.
		 *
		 * If the state is DM_RH_NOSYNC, the region should be kept off
		 * from clean list.
		 * The hash entry for DM_RH_NOSYNC will remain in memory
		 * until the region is recovered or the map is reloaded.
		 */

		/* do nothing for DM_RH_NOSYNC */
		if (unlikely(rh->flush_failure)) {
			/*
			 * If a write flush failed some time ago, we
			 * don't know whether or not this write made it
			 * to the disk, so we must resync the device.
			 */
			reg->state = DM_RH_NOSYNC;
		} else if (reg->state == DM_RH_RECOVERING) {
			list_add_tail(&reg->list, &rh->quiesced_regions);
		} else if (reg->state == DM_RH_DIRTY) {
			reg->state = DM_RH_CLEAN;
			list_add(&reg->list, &rh->clean_regions);
		}
		should_wake = 1;
	}
	spin_unlock_irqrestore(&rh->region_lock, flags);

	if (should_wake)
		rh->wakeup_workers(rh->context);
}
EXPORT_SYMBOL_GPL(dm_rh_dec);

/*
 * Starts quiescing a region in preparation for recovery.
 */
static int __rh_recovery_prepare(struct dm_region_hash *rh)
{
	int r;
	region_t region;
	struct dm_region *reg;

	/*
	 * Ask the dirty log what's next.
	 */
	r = rh->log->type->get_resync_work(rh->log, &region);
	if (r <= 0)
		return r;

	/*
	 * Get this region, and start it quiescing by setting the
	 * recovering flag.
	 */
	read_lock(&rh->hash_lock);
	reg = __rh_find(rh, region);
	read_unlock(&rh->hash_lock);

	spin_lock_irq(&rh->region_lock);
	reg->state = DM_RH_RECOVERING;

	/* Already quiesced ? */
	if (atomic_read(&reg->pending))
		list_del_init(&reg->list);
	else
		list_move(&reg->list, &rh->quiesced_regions);

	spin_unlock_irq(&rh->region_lock);

	return 1;
}

void dm_rh_recovery_prepare(struct dm_region_hash *rh)
{
	/* Extra reference to avoid race with dm_rh_stop_recovery */
	atomic_inc(&rh->recovery_in_flight);

	while (!down_trylock(&rh->recovery_count)) {
		atomic_inc(&rh->recovery_in_flight);
		if (__rh_recovery_prepare(rh) <= 0) {
			atomic_dec(&rh->recovery_in_flight);
			up(&rh->recovery_count);
			break;
		}
	}

	/* Drop the extra reference */
	if (atomic_dec_and_test(&rh->recovery_in_flight))
		rh->wakeup_all_recovery_waiters(rh->context);
}
EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare);

/*
 * Returns any quiesced regions.
 */
struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh)
{
	struct dm_region *reg = NULL;

	spin_lock_irq(&rh->region_lock);
	if (!list_empty(&rh->quiesced_regions)) {
		reg = list_entry(rh->quiesced_regions.next,
				 struct dm_region, list);
		list_del_init(&reg->list);  /* remove from the quiesced list */
	}
	spin_unlock_irq(&rh->region_lock);

	return reg;
}
EXPORT_SYMBOL_GPL(dm_rh_recovery_start);

void dm_rh_recovery_end(struct dm_region *reg, int success)
{
	struct dm_region_hash *rh = reg->rh;

	spin_lock_irq(&rh->region_lock);
	if (success)
		list_add(&reg->list, &reg->rh->recovered_regions);
	else
		list_add(&reg->list, &reg->rh->failed_recovered_regions);

	spin_unlock_irq(&rh->region_lock);

	rh->wakeup_workers(rh->context);
}
EXPORT_SYMBOL_GPL(dm_rh_recovery_end);

/* Return recovery in flight count. */
int dm_rh_recovery_in_flight(struct dm_region_hash *rh)
{
	return atomic_read(&rh->recovery_in_flight);
}
EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight);

int dm_rh_flush(struct dm_region_hash *rh)
{
	return rh->log->type->flush(rh->log);
}
EXPORT_SYMBOL_GPL(dm_rh_flush);

void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio)
{
	struct dm_region *reg;

	read_lock(&rh->hash_lock);
	reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio));
	bio_list_add(&reg->delayed_bios, bio);
	read_unlock(&rh->hash_lock);
}
EXPORT_SYMBOL_GPL(dm_rh_delay);

void dm_rh_stop_recovery(struct dm_region_hash *rh)
{
	int i;

	/* wait for any recovering regions */
	for (i = 0; i < rh->max_recovery; i++)
		down(&rh->recovery_count);
}
EXPORT_SYMBOL_GPL(dm_rh_stop_recovery);

void dm_rh_start_recovery(struct dm_region_hash *rh)
{
	int i;

	for (i = 0; i < rh->max_recovery; i++)
		up(&rh->recovery_count);

	rh->wakeup_workers(rh->context);
}
EXPORT_SYMBOL_GPL(dm_rh_start_recovery);

MODULE_DESCRIPTION(DM_NAME " region hash");
MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");