xref: /openbmc/linux/drivers/md/dm-region-hash.c (revision 0edbfea5)
1 /*
2  * Copyright (C) 2003 Sistina Software Limited.
3  * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
4  *
5  * This file is released under the GPL.
6  */
7 
8 #include <linux/dm-dirty-log.h>
9 #include <linux/dm-region-hash.h>
10 
11 #include <linux/ctype.h>
12 #include <linux/init.h>
13 #include <linux/module.h>
14 #include <linux/slab.h>
15 #include <linux/vmalloc.h>
16 
17 #include "dm.h"
18 
19 #define	DM_MSG_PREFIX	"region hash"
20 
21 /*-----------------------------------------------------------------
22  * Region hash
23  *
24  * The mirror splits itself up into discrete regions.  Each
25  * region can be in one of three states: clean, dirty,
26  * nosync.  There is no need to put clean regions in the hash.
27  *
28  * In addition to being present in the hash table a region _may_
29  * be present on one of three lists.
30  *
31  *   clean_regions: Regions on this list have no io pending to
32  *   them, they are in sync, we are no longer interested in them,
33  *   they are dull.  dm_rh_update_states() will remove them from the
34  *   hash table.
35  *
36  *   quiesced_regions: These regions have been spun down, ready
37  *   for recovery.  rh_recovery_start() will remove regions from
38  *   this list and hand them to kmirrord, which will schedule the
39  *   recovery io with kcopyd.
40  *
41  *   recovered_regions: Regions that kcopyd has successfully
42  *   recovered.  dm_rh_update_states() will now schedule any delayed
43  *   io, up the recovery_count, and remove the region from the
44  *   hash.
45  *
46  * There are 2 locks:
47  *   A rw spin lock 'hash_lock' protects just the hash table,
48  *   this is never held in write mode from interrupt context,
49  *   which I believe means that we only have to disable irqs when
50  *   doing a write lock.
51  *
52  *   An ordinary spin lock 'region_lock' that protects the three
53  *   lists in the region_hash, with the 'state', 'list' and
54  *   'delayed_bios' fields of the regions.  This is used from irq
55  *   context, so all other uses will have to suspend local irqs.
56  *---------------------------------------------------------------*/
57 struct dm_region_hash {
58 	uint32_t region_size;
59 	unsigned region_shift;
60 
61 	/* holds persistent region state */
62 	struct dm_dirty_log *log;
63 
64 	/* hash table */
65 	rwlock_t hash_lock;
66 	mempool_t *region_pool;
67 	unsigned mask;
68 	unsigned nr_buckets;
69 	unsigned prime;
70 	unsigned shift;
71 	struct list_head *buckets;
72 
73 	unsigned max_recovery; /* Max # of regions to recover in parallel */
74 
75 	spinlock_t region_lock;
76 	atomic_t recovery_in_flight;
77 	struct semaphore recovery_count;
78 	struct list_head clean_regions;
79 	struct list_head quiesced_regions;
80 	struct list_head recovered_regions;
81 	struct list_head failed_recovered_regions;
82 
83 	/*
84 	 * If there was a flush failure no regions can be marked clean.
85 	 */
86 	int flush_failure;
87 
88 	void *context;
89 	sector_t target_begin;
90 
91 	/* Callback function to schedule bios writes */
92 	void (*dispatch_bios)(void *context, struct bio_list *bios);
93 
94 	/* Callback function to wakeup callers worker thread. */
95 	void (*wakeup_workers)(void *context);
96 
97 	/* Callback function to wakeup callers recovery waiters. */
98 	void (*wakeup_all_recovery_waiters)(void *context);
99 };
100 
101 struct dm_region {
102 	struct dm_region_hash *rh;	/* FIXME: can we get rid of this ? */
103 	region_t key;
104 	int state;
105 
106 	struct list_head hash_list;
107 	struct list_head list;
108 
109 	atomic_t pending;
110 	struct bio_list delayed_bios;
111 };
112 
113 /*
114  * Conversion fns
115  */
116 static region_t dm_rh_sector_to_region(struct dm_region_hash *rh, sector_t sector)
117 {
118 	return sector >> rh->region_shift;
119 }
120 
121 sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region)
122 {
123 	return region << rh->region_shift;
124 }
125 EXPORT_SYMBOL_GPL(dm_rh_region_to_sector);
126 
127 region_t dm_rh_bio_to_region(struct dm_region_hash *rh, struct bio *bio)
128 {
129 	return dm_rh_sector_to_region(rh, bio->bi_iter.bi_sector -
130 				      rh->target_begin);
131 }
132 EXPORT_SYMBOL_GPL(dm_rh_bio_to_region);
133 
134 void *dm_rh_region_context(struct dm_region *reg)
135 {
136 	return reg->rh->context;
137 }
138 EXPORT_SYMBOL_GPL(dm_rh_region_context);
139 
140 region_t dm_rh_get_region_key(struct dm_region *reg)
141 {
142 	return reg->key;
143 }
144 EXPORT_SYMBOL_GPL(dm_rh_get_region_key);
145 
146 sector_t dm_rh_get_region_size(struct dm_region_hash *rh)
147 {
148 	return rh->region_size;
149 }
150 EXPORT_SYMBOL_GPL(dm_rh_get_region_size);
151 
152 /*
153  * FIXME: shall we pass in a structure instead of all these args to
154  * dm_region_hash_create()????
155  */
156 #define RH_HASH_MULT 2654435387U
157 #define RH_HASH_SHIFT 12
158 
159 #define MIN_REGIONS 64
160 struct dm_region_hash *dm_region_hash_create(
161 		void *context, void (*dispatch_bios)(void *context,
162 						     struct bio_list *bios),
163 		void (*wakeup_workers)(void *context),
164 		void (*wakeup_all_recovery_waiters)(void *context),
165 		sector_t target_begin, unsigned max_recovery,
166 		struct dm_dirty_log *log, uint32_t region_size,
167 		region_t nr_regions)
168 {
169 	struct dm_region_hash *rh;
170 	unsigned nr_buckets, max_buckets;
171 	size_t i;
172 
173 	/*
174 	 * Calculate a suitable number of buckets for our hash
175 	 * table.
176 	 */
177 	max_buckets = nr_regions >> 6;
178 	for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1)
179 		;
180 	nr_buckets >>= 1;
181 
182 	rh = kmalloc(sizeof(*rh), GFP_KERNEL);
183 	if (!rh) {
184 		DMERR("unable to allocate region hash memory");
185 		return ERR_PTR(-ENOMEM);
186 	}
187 
188 	rh->context = context;
189 	rh->dispatch_bios = dispatch_bios;
190 	rh->wakeup_workers = wakeup_workers;
191 	rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters;
192 	rh->target_begin = target_begin;
193 	rh->max_recovery = max_recovery;
194 	rh->log = log;
195 	rh->region_size = region_size;
196 	rh->region_shift = __ffs(region_size);
197 	rwlock_init(&rh->hash_lock);
198 	rh->mask = nr_buckets - 1;
199 	rh->nr_buckets = nr_buckets;
200 
201 	rh->shift = RH_HASH_SHIFT;
202 	rh->prime = RH_HASH_MULT;
203 
204 	rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets));
205 	if (!rh->buckets) {
206 		DMERR("unable to allocate region hash bucket memory");
207 		kfree(rh);
208 		return ERR_PTR(-ENOMEM);
209 	}
210 
211 	for (i = 0; i < nr_buckets; i++)
212 		INIT_LIST_HEAD(rh->buckets + i);
213 
214 	spin_lock_init(&rh->region_lock);
215 	sema_init(&rh->recovery_count, 0);
216 	atomic_set(&rh->recovery_in_flight, 0);
217 	INIT_LIST_HEAD(&rh->clean_regions);
218 	INIT_LIST_HEAD(&rh->quiesced_regions);
219 	INIT_LIST_HEAD(&rh->recovered_regions);
220 	INIT_LIST_HEAD(&rh->failed_recovered_regions);
221 	rh->flush_failure = 0;
222 
223 	rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
224 						      sizeof(struct dm_region));
225 	if (!rh->region_pool) {
226 		vfree(rh->buckets);
227 		kfree(rh);
228 		rh = ERR_PTR(-ENOMEM);
229 	}
230 
231 	return rh;
232 }
233 EXPORT_SYMBOL_GPL(dm_region_hash_create);
234 
235 void dm_region_hash_destroy(struct dm_region_hash *rh)
236 {
237 	unsigned h;
238 	struct dm_region *reg, *nreg;
239 
240 	BUG_ON(!list_empty(&rh->quiesced_regions));
241 	for (h = 0; h < rh->nr_buckets; h++) {
242 		list_for_each_entry_safe(reg, nreg, rh->buckets + h,
243 					 hash_list) {
244 			BUG_ON(atomic_read(&reg->pending));
245 			mempool_free(reg, rh->region_pool);
246 		}
247 	}
248 
249 	if (rh->log)
250 		dm_dirty_log_destroy(rh->log);
251 
252 	mempool_destroy(rh->region_pool);
253 	vfree(rh->buckets);
254 	kfree(rh);
255 }
256 EXPORT_SYMBOL_GPL(dm_region_hash_destroy);
257 
258 struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh)
259 {
260 	return rh->log;
261 }
262 EXPORT_SYMBOL_GPL(dm_rh_dirty_log);
263 
264 static unsigned rh_hash(struct dm_region_hash *rh, region_t region)
265 {
266 	return (unsigned) ((region * rh->prime) >> rh->shift) & rh->mask;
267 }
268 
269 static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region)
270 {
271 	struct dm_region *reg;
272 	struct list_head *bucket = rh->buckets + rh_hash(rh, region);
273 
274 	list_for_each_entry(reg, bucket, hash_list)
275 		if (reg->key == region)
276 			return reg;
277 
278 	return NULL;
279 }
280 
281 static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg)
282 {
283 	list_add(&reg->hash_list, rh->buckets + rh_hash(rh, reg->key));
284 }
285 
286 static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
287 {
288 	struct dm_region *reg, *nreg;
289 
290 	nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC);
291 	if (unlikely(!nreg))
292 		nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
293 
294 	nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
295 		      DM_RH_CLEAN : DM_RH_NOSYNC;
296 	nreg->rh = rh;
297 	nreg->key = region;
298 	INIT_LIST_HEAD(&nreg->list);
299 	atomic_set(&nreg->pending, 0);
300 	bio_list_init(&nreg->delayed_bios);
301 
302 	write_lock_irq(&rh->hash_lock);
303 	reg = __rh_lookup(rh, region);
304 	if (reg)
305 		/* We lost the race. */
306 		mempool_free(nreg, rh->region_pool);
307 	else {
308 		__rh_insert(rh, nreg);
309 		if (nreg->state == DM_RH_CLEAN) {
310 			spin_lock(&rh->region_lock);
311 			list_add(&nreg->list, &rh->clean_regions);
312 			spin_unlock(&rh->region_lock);
313 		}
314 
315 		reg = nreg;
316 	}
317 	write_unlock_irq(&rh->hash_lock);
318 
319 	return reg;
320 }
321 
322 static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region)
323 {
324 	struct dm_region *reg;
325 
326 	reg = __rh_lookup(rh, region);
327 	if (!reg) {
328 		read_unlock(&rh->hash_lock);
329 		reg = __rh_alloc(rh, region);
330 		read_lock(&rh->hash_lock);
331 	}
332 
333 	return reg;
334 }
335 
336 int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block)
337 {
338 	int r;
339 	struct dm_region *reg;
340 
341 	read_lock(&rh->hash_lock);
342 	reg = __rh_lookup(rh, region);
343 	read_unlock(&rh->hash_lock);
344 
345 	if (reg)
346 		return reg->state;
347 
348 	/*
349 	 * The region wasn't in the hash, so we fall back to the
350 	 * dirty log.
351 	 */
352 	r = rh->log->type->in_sync(rh->log, region, may_block);
353 
354 	/*
355 	 * Any error from the dirty log (eg. -EWOULDBLOCK) gets
356 	 * taken as a DM_RH_NOSYNC
357 	 */
358 	return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC;
359 }
360 EXPORT_SYMBOL_GPL(dm_rh_get_state);
361 
362 static void complete_resync_work(struct dm_region *reg, int success)
363 {
364 	struct dm_region_hash *rh = reg->rh;
365 
366 	rh->log->type->set_region_sync(rh->log, reg->key, success);
367 
368 	/*
369 	 * Dispatch the bios before we call 'wake_up_all'.
370 	 * This is important because if we are suspending,
371 	 * we want to know that recovery is complete and
372 	 * the work queue is flushed.  If we wake_up_all
373 	 * before we dispatch_bios (queue bios and call wake()),
374 	 * then we risk suspending before the work queue
375 	 * has been properly flushed.
376 	 */
377 	rh->dispatch_bios(rh->context, &reg->delayed_bios);
378 	if (atomic_dec_and_test(&rh->recovery_in_flight))
379 		rh->wakeup_all_recovery_waiters(rh->context);
380 	up(&rh->recovery_count);
381 }
382 
383 /* dm_rh_mark_nosync
384  * @ms
385  * @bio
386  *
387  * The bio was written on some mirror(s) but failed on other mirror(s).
388  * We can successfully endio the bio but should avoid the region being
389  * marked clean by setting the state DM_RH_NOSYNC.
390  *
391  * This function is _not_ safe in interrupt context!
392  */
393 void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio)
394 {
395 	unsigned long flags;
396 	struct dm_dirty_log *log = rh->log;
397 	struct dm_region *reg;
398 	region_t region = dm_rh_bio_to_region(rh, bio);
399 	int recovering = 0;
400 
401 	if (bio->bi_rw & REQ_FLUSH) {
402 		rh->flush_failure = 1;
403 		return;
404 	}
405 
406 	if (bio->bi_rw & REQ_DISCARD)
407 		return;
408 
409 	/* We must inform the log that the sync count has changed. */
410 	log->type->set_region_sync(log, region, 0);
411 
412 	read_lock(&rh->hash_lock);
413 	reg = __rh_find(rh, region);
414 	read_unlock(&rh->hash_lock);
415 
416 	/* region hash entry should exist because write was in-flight */
417 	BUG_ON(!reg);
418 	BUG_ON(!list_empty(&reg->list));
419 
420 	spin_lock_irqsave(&rh->region_lock, flags);
421 	/*
422 	 * Possible cases:
423 	 *   1) DM_RH_DIRTY
424 	 *   2) DM_RH_NOSYNC: was dirty, other preceding writes failed
425 	 *   3) DM_RH_RECOVERING: flushing pending writes
426 	 * Either case, the region should have not been connected to list.
427 	 */
428 	recovering = (reg->state == DM_RH_RECOVERING);
429 	reg->state = DM_RH_NOSYNC;
430 	BUG_ON(!list_empty(&reg->list));
431 	spin_unlock_irqrestore(&rh->region_lock, flags);
432 
433 	if (recovering)
434 		complete_resync_work(reg, 0);
435 }
436 EXPORT_SYMBOL_GPL(dm_rh_mark_nosync);
437 
438 void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled)
439 {
440 	struct dm_region *reg, *next;
441 
442 	LIST_HEAD(clean);
443 	LIST_HEAD(recovered);
444 	LIST_HEAD(failed_recovered);
445 
446 	/*
447 	 * Quickly grab the lists.
448 	 */
449 	write_lock_irq(&rh->hash_lock);
450 	spin_lock(&rh->region_lock);
451 	if (!list_empty(&rh->clean_regions)) {
452 		list_splice_init(&rh->clean_regions, &clean);
453 
454 		list_for_each_entry(reg, &clean, list)
455 			list_del(&reg->hash_list);
456 	}
457 
458 	if (!list_empty(&rh->recovered_regions)) {
459 		list_splice_init(&rh->recovered_regions, &recovered);
460 
461 		list_for_each_entry(reg, &recovered, list)
462 			list_del(&reg->hash_list);
463 	}
464 
465 	if (!list_empty(&rh->failed_recovered_regions)) {
466 		list_splice_init(&rh->failed_recovered_regions,
467 				 &failed_recovered);
468 
469 		list_for_each_entry(reg, &failed_recovered, list)
470 			list_del(&reg->hash_list);
471 	}
472 
473 	spin_unlock(&rh->region_lock);
474 	write_unlock_irq(&rh->hash_lock);
475 
476 	/*
477 	 * All the regions on the recovered and clean lists have
478 	 * now been pulled out of the system, so no need to do
479 	 * any more locking.
480 	 */
481 	list_for_each_entry_safe(reg, next, &recovered, list) {
482 		rh->log->type->clear_region(rh->log, reg->key);
483 		complete_resync_work(reg, 1);
484 		mempool_free(reg, rh->region_pool);
485 	}
486 
487 	list_for_each_entry_safe(reg, next, &failed_recovered, list) {
488 		complete_resync_work(reg, errors_handled ? 0 : 1);
489 		mempool_free(reg, rh->region_pool);
490 	}
491 
492 	list_for_each_entry_safe(reg, next, &clean, list) {
493 		rh->log->type->clear_region(rh->log, reg->key);
494 		mempool_free(reg, rh->region_pool);
495 	}
496 
497 	rh->log->type->flush(rh->log);
498 }
499 EXPORT_SYMBOL_GPL(dm_rh_update_states);
500 
501 static void rh_inc(struct dm_region_hash *rh, region_t region)
502 {
503 	struct dm_region *reg;
504 
505 	read_lock(&rh->hash_lock);
506 	reg = __rh_find(rh, region);
507 
508 	spin_lock_irq(&rh->region_lock);
509 	atomic_inc(&reg->pending);
510 
511 	if (reg->state == DM_RH_CLEAN) {
512 		reg->state = DM_RH_DIRTY;
513 		list_del_init(&reg->list);	/* take off the clean list */
514 		spin_unlock_irq(&rh->region_lock);
515 
516 		rh->log->type->mark_region(rh->log, reg->key);
517 	} else
518 		spin_unlock_irq(&rh->region_lock);
519 
520 
521 	read_unlock(&rh->hash_lock);
522 }
523 
524 void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios)
525 {
526 	struct bio *bio;
527 
528 	for (bio = bios->head; bio; bio = bio->bi_next) {
529 		if (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD))
530 			continue;
531 		rh_inc(rh, dm_rh_bio_to_region(rh, bio));
532 	}
533 }
534 EXPORT_SYMBOL_GPL(dm_rh_inc_pending);
535 
536 void dm_rh_dec(struct dm_region_hash *rh, region_t region)
537 {
538 	unsigned long flags;
539 	struct dm_region *reg;
540 	int should_wake = 0;
541 
542 	read_lock(&rh->hash_lock);
543 	reg = __rh_lookup(rh, region);
544 	read_unlock(&rh->hash_lock);
545 
546 	spin_lock_irqsave(&rh->region_lock, flags);
547 	if (atomic_dec_and_test(&reg->pending)) {
548 		/*
549 		 * There is no pending I/O for this region.
550 		 * We can move the region to corresponding list for next action.
551 		 * At this point, the region is not yet connected to any list.
552 		 *
553 		 * If the state is DM_RH_NOSYNC, the region should be kept off
554 		 * from clean list.
555 		 * The hash entry for DM_RH_NOSYNC will remain in memory
556 		 * until the region is recovered or the map is reloaded.
557 		 */
558 
559 		/* do nothing for DM_RH_NOSYNC */
560 		if (unlikely(rh->flush_failure)) {
561 			/*
562 			 * If a write flush failed some time ago, we
563 			 * don't know whether or not this write made it
564 			 * to the disk, so we must resync the device.
565 			 */
566 			reg->state = DM_RH_NOSYNC;
567 		} else if (reg->state == DM_RH_RECOVERING) {
568 			list_add_tail(&reg->list, &rh->quiesced_regions);
569 		} else if (reg->state == DM_RH_DIRTY) {
570 			reg->state = DM_RH_CLEAN;
571 			list_add(&reg->list, &rh->clean_regions);
572 		}
573 		should_wake = 1;
574 	}
575 	spin_unlock_irqrestore(&rh->region_lock, flags);
576 
577 	if (should_wake)
578 		rh->wakeup_workers(rh->context);
579 }
580 EXPORT_SYMBOL_GPL(dm_rh_dec);
581 
582 /*
583  * Starts quiescing a region in preparation for recovery.
584  */
585 static int __rh_recovery_prepare(struct dm_region_hash *rh)
586 {
587 	int r;
588 	region_t region;
589 	struct dm_region *reg;
590 
591 	/*
592 	 * Ask the dirty log what's next.
593 	 */
594 	r = rh->log->type->get_resync_work(rh->log, &region);
595 	if (r <= 0)
596 		return r;
597 
598 	/*
599 	 * Get this region, and start it quiescing by setting the
600 	 * recovering flag.
601 	 */
602 	read_lock(&rh->hash_lock);
603 	reg = __rh_find(rh, region);
604 	read_unlock(&rh->hash_lock);
605 
606 	spin_lock_irq(&rh->region_lock);
607 	reg->state = DM_RH_RECOVERING;
608 
609 	/* Already quiesced ? */
610 	if (atomic_read(&reg->pending))
611 		list_del_init(&reg->list);
612 	else
613 		list_move(&reg->list, &rh->quiesced_regions);
614 
615 	spin_unlock_irq(&rh->region_lock);
616 
617 	return 1;
618 }
619 
620 void dm_rh_recovery_prepare(struct dm_region_hash *rh)
621 {
622 	/* Extra reference to avoid race with dm_rh_stop_recovery */
623 	atomic_inc(&rh->recovery_in_flight);
624 
625 	while (!down_trylock(&rh->recovery_count)) {
626 		atomic_inc(&rh->recovery_in_flight);
627 		if (__rh_recovery_prepare(rh) <= 0) {
628 			atomic_dec(&rh->recovery_in_flight);
629 			up(&rh->recovery_count);
630 			break;
631 		}
632 	}
633 
634 	/* Drop the extra reference */
635 	if (atomic_dec_and_test(&rh->recovery_in_flight))
636 		rh->wakeup_all_recovery_waiters(rh->context);
637 }
638 EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare);
639 
640 /*
641  * Returns any quiesced regions.
642  */
643 struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh)
644 {
645 	struct dm_region *reg = NULL;
646 
647 	spin_lock_irq(&rh->region_lock);
648 	if (!list_empty(&rh->quiesced_regions)) {
649 		reg = list_entry(rh->quiesced_regions.next,
650 				 struct dm_region, list);
651 		list_del_init(&reg->list);  /* remove from the quiesced list */
652 	}
653 	spin_unlock_irq(&rh->region_lock);
654 
655 	return reg;
656 }
657 EXPORT_SYMBOL_GPL(dm_rh_recovery_start);
658 
659 void dm_rh_recovery_end(struct dm_region *reg, int success)
660 {
661 	struct dm_region_hash *rh = reg->rh;
662 
663 	spin_lock_irq(&rh->region_lock);
664 	if (success)
665 		list_add(&reg->list, &reg->rh->recovered_regions);
666 	else
667 		list_add(&reg->list, &reg->rh->failed_recovered_regions);
668 
669 	spin_unlock_irq(&rh->region_lock);
670 
671 	rh->wakeup_workers(rh->context);
672 }
673 EXPORT_SYMBOL_GPL(dm_rh_recovery_end);
674 
675 /* Return recovery in flight count. */
676 int dm_rh_recovery_in_flight(struct dm_region_hash *rh)
677 {
678 	return atomic_read(&rh->recovery_in_flight);
679 }
680 EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight);
681 
682 int dm_rh_flush(struct dm_region_hash *rh)
683 {
684 	return rh->log->type->flush(rh->log);
685 }
686 EXPORT_SYMBOL_GPL(dm_rh_flush);
687 
688 void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio)
689 {
690 	struct dm_region *reg;
691 
692 	read_lock(&rh->hash_lock);
693 	reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio));
694 	bio_list_add(&reg->delayed_bios, bio);
695 	read_unlock(&rh->hash_lock);
696 }
697 EXPORT_SYMBOL_GPL(dm_rh_delay);
698 
699 void dm_rh_stop_recovery(struct dm_region_hash *rh)
700 {
701 	int i;
702 
703 	/* wait for any recovering regions */
704 	for (i = 0; i < rh->max_recovery; i++)
705 		down(&rh->recovery_count);
706 }
707 EXPORT_SYMBOL_GPL(dm_rh_stop_recovery);
708 
709 void dm_rh_start_recovery(struct dm_region_hash *rh)
710 {
711 	int i;
712 
713 	for (i = 0; i < rh->max_recovery; i++)
714 		up(&rh->recovery_count);
715 
716 	rh->wakeup_workers(rh->context);
717 }
718 EXPORT_SYMBOL_GPL(dm_rh_start_recovery);
719 
720 MODULE_DESCRIPTION(DM_NAME " region hash");
721 MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@redhat.com>");
722 MODULE_LICENSE("GPL");
723