xref: /openbmc/linux/drivers/md/dm-snap.c (revision 9d749629)
1 /*
2  * dm-snapshot.c
3  *
4  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
5  *
6  * This file is released under the GPL.
7  */
8 
9 #include <linux/blkdev.h>
10 #include <linux/device-mapper.h>
11 #include <linux/delay.h>
12 #include <linux/fs.h>
13 #include <linux/init.h>
14 #include <linux/kdev_t.h>
15 #include <linux/list.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/log2.h>
21 #include <linux/dm-kcopyd.h>
22 
23 #include "dm-exception-store.h"
24 
25 #define DM_MSG_PREFIX "snapshots"
26 
27 static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
28 
29 #define dm_target_is_snapshot_merge(ti) \
30 	((ti)->type->name == dm_snapshot_merge_target_name)
31 
32 /*
33  * The size of the mempool used to track chunks in use.
34  */
35 #define MIN_IOS 256
36 
37 #define DM_TRACKED_CHUNK_HASH_SIZE	16
38 #define DM_TRACKED_CHUNK_HASH(x)	((unsigned long)(x) & \
39 					 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
40 
41 struct dm_exception_table {
42 	uint32_t hash_mask;
43 	unsigned hash_shift;
44 	struct list_head *table;
45 };
46 
47 struct dm_snapshot {
48 	struct rw_semaphore lock;
49 
50 	struct dm_dev *origin;
51 	struct dm_dev *cow;
52 
53 	struct dm_target *ti;
54 
55 	/* List of snapshots per Origin */
56 	struct list_head list;
57 
58 	/*
59 	 * You can't use a snapshot if this is 0 (e.g. if full).
60 	 * A snapshot-merge target never clears this.
61 	 */
62 	int valid;
63 
64 	/* Origin writes don't trigger exceptions until this is set */
65 	int active;
66 
67 	atomic_t pending_exceptions_count;
68 
69 	mempool_t *pending_pool;
70 
71 	struct dm_exception_table pending;
72 	struct dm_exception_table complete;
73 
74 	/*
75 	 * pe_lock protects all pending_exception operations and access
76 	 * as well as the snapshot_bios list.
77 	 */
78 	spinlock_t pe_lock;
79 
80 	/* Chunks with outstanding reads */
81 	spinlock_t tracked_chunk_lock;
82 	struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
83 
84 	/* The on disk metadata handler */
85 	struct dm_exception_store *store;
86 
87 	struct dm_kcopyd_client *kcopyd_client;
88 
89 	/* Wait for events based on state_bits */
90 	unsigned long state_bits;
91 
92 	/* Range of chunks currently being merged. */
93 	chunk_t first_merging_chunk;
94 	int num_merging_chunks;
95 
96 	/*
97 	 * The merge operation failed if this flag is set.
98 	 * Failure modes are handled as follows:
99 	 * - I/O error reading the header
100 	 *   	=> don't load the target; abort.
101 	 * - Header does not have "valid" flag set
102 	 *   	=> use the origin; forget about the snapshot.
103 	 * - I/O error when reading exceptions
104 	 *   	=> don't load the target; abort.
105 	 *         (We can't use the intermediate origin state.)
106 	 * - I/O error while merging
107 	 *	=> stop merging; set merge_failed; process I/O normally.
108 	 */
109 	int merge_failed;
110 
111 	/*
112 	 * Incoming bios that overlap with chunks being merged must wait
113 	 * for them to be committed.
114 	 */
115 	struct bio_list bios_queued_during_merge;
116 };
117 
118 /*
119  * state_bits:
120  *   RUNNING_MERGE  - Merge operation is in progress.
121  *   SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
122  *                    cleared afterwards.
123  */
124 #define RUNNING_MERGE          0
125 #define SHUTDOWN_MERGE         1
126 
127 struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
128 {
129 	return s->origin;
130 }
131 EXPORT_SYMBOL(dm_snap_origin);
132 
133 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
134 {
135 	return s->cow;
136 }
137 EXPORT_SYMBOL(dm_snap_cow);
138 
139 static sector_t chunk_to_sector(struct dm_exception_store *store,
140 				chunk_t chunk)
141 {
142 	return chunk << store->chunk_shift;
143 }
144 
145 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
146 {
147 	/*
148 	 * There is only ever one instance of a particular block
149 	 * device so we can compare pointers safely.
150 	 */
151 	return lhs == rhs;
152 }
153 
154 struct dm_snap_pending_exception {
155 	struct dm_exception e;
156 
157 	/*
158 	 * Origin buffers waiting for this to complete are held
159 	 * in a bio list
160 	 */
161 	struct bio_list origin_bios;
162 	struct bio_list snapshot_bios;
163 
164 	/* Pointer back to snapshot context */
165 	struct dm_snapshot *snap;
166 
167 	/*
168 	 * 1 indicates the exception has already been sent to
169 	 * kcopyd.
170 	 */
171 	int started;
172 
173 	/*
174 	 * For writing a complete chunk, bypassing the copy.
175 	 */
176 	struct bio *full_bio;
177 	bio_end_io_t *full_bio_end_io;
178 	void *full_bio_private;
179 };
180 
181 /*
182  * Hash table mapping origin volumes to lists of snapshots and
183  * a lock to protect it
184  */
185 static struct kmem_cache *exception_cache;
186 static struct kmem_cache *pending_cache;
187 
188 struct dm_snap_tracked_chunk {
189 	struct hlist_node node;
190 	chunk_t chunk;
191 };
192 
193 static void init_tracked_chunk(struct bio *bio)
194 {
195 	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
196 	INIT_HLIST_NODE(&c->node);
197 }
198 
199 static bool is_bio_tracked(struct bio *bio)
200 {
201 	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
202 	return !hlist_unhashed(&c->node);
203 }
204 
205 static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
206 {
207 	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
208 
209 	c->chunk = chunk;
210 
211 	spin_lock_irq(&s->tracked_chunk_lock);
212 	hlist_add_head(&c->node,
213 		       &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
214 	spin_unlock_irq(&s->tracked_chunk_lock);
215 }
216 
217 static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
218 {
219 	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
220 	unsigned long flags;
221 
222 	spin_lock_irqsave(&s->tracked_chunk_lock, flags);
223 	hlist_del(&c->node);
224 	spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
225 }
226 
227 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
228 {
229 	struct dm_snap_tracked_chunk *c;
230 	struct hlist_node *hn;
231 	int found = 0;
232 
233 	spin_lock_irq(&s->tracked_chunk_lock);
234 
235 	hlist_for_each_entry(c, hn,
236 	    &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
237 		if (c->chunk == chunk) {
238 			found = 1;
239 			break;
240 		}
241 	}
242 
243 	spin_unlock_irq(&s->tracked_chunk_lock);
244 
245 	return found;
246 }
247 
248 /*
249  * This conflicting I/O is extremely improbable in the caller,
250  * so msleep(1) is sufficient and there is no need for a wait queue.
251  */
252 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
253 {
254 	while (__chunk_is_tracked(s, chunk))
255 		msleep(1);
256 }
257 
258 /*
259  * One of these per registered origin, held in the snapshot_origins hash
260  */
261 struct origin {
262 	/* The origin device */
263 	struct block_device *bdev;
264 
265 	struct list_head hash_list;
266 
267 	/* List of snapshots for this origin */
268 	struct list_head snapshots;
269 };
270 
271 /*
272  * Size of the hash table for origin volumes. If we make this
273  * the size of the minors list then it should be nearly perfect
274  */
275 #define ORIGIN_HASH_SIZE 256
276 #define ORIGIN_MASK      0xFF
277 static struct list_head *_origins;
278 static struct rw_semaphore _origins_lock;
279 
280 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
281 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
282 static uint64_t _pending_exceptions_done_count;
283 
284 static int init_origin_hash(void)
285 {
286 	int i;
287 
288 	_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
289 			   GFP_KERNEL);
290 	if (!_origins) {
291 		DMERR("unable to allocate memory");
292 		return -ENOMEM;
293 	}
294 
295 	for (i = 0; i < ORIGIN_HASH_SIZE; i++)
296 		INIT_LIST_HEAD(_origins + i);
297 	init_rwsem(&_origins_lock);
298 
299 	return 0;
300 }
301 
302 static void exit_origin_hash(void)
303 {
304 	kfree(_origins);
305 }
306 
307 static unsigned origin_hash(struct block_device *bdev)
308 {
309 	return bdev->bd_dev & ORIGIN_MASK;
310 }
311 
312 static struct origin *__lookup_origin(struct block_device *origin)
313 {
314 	struct list_head *ol;
315 	struct origin *o;
316 
317 	ol = &_origins[origin_hash(origin)];
318 	list_for_each_entry (o, ol, hash_list)
319 		if (bdev_equal(o->bdev, origin))
320 			return o;
321 
322 	return NULL;
323 }
324 
325 static void __insert_origin(struct origin *o)
326 {
327 	struct list_head *sl = &_origins[origin_hash(o->bdev)];
328 	list_add_tail(&o->hash_list, sl);
329 }
330 
331 /*
332  * _origins_lock must be held when calling this function.
333  * Returns number of snapshots registered using the supplied cow device, plus:
334  * snap_src - a snapshot suitable for use as a source of exception handover
335  * snap_dest - a snapshot capable of receiving exception handover.
336  * snap_merge - an existing snapshot-merge target linked to the same origin.
337  *   There can be at most one snapshot-merge target. The parameter is optional.
338  *
339  * Possible return values and states of snap_src and snap_dest.
340  *   0: NULL, NULL  - first new snapshot
341  *   1: snap_src, NULL - normal snapshot
342  *   2: snap_src, snap_dest  - waiting for handover
343  *   2: snap_src, NULL - handed over, waiting for old to be deleted
344  *   1: NULL, snap_dest - source got destroyed without handover
345  */
346 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
347 					struct dm_snapshot **snap_src,
348 					struct dm_snapshot **snap_dest,
349 					struct dm_snapshot **snap_merge)
350 {
351 	struct dm_snapshot *s;
352 	struct origin *o;
353 	int count = 0;
354 	int active;
355 
356 	o = __lookup_origin(snap->origin->bdev);
357 	if (!o)
358 		goto out;
359 
360 	list_for_each_entry(s, &o->snapshots, list) {
361 		if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
362 			*snap_merge = s;
363 		if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
364 			continue;
365 
366 		down_read(&s->lock);
367 		active = s->active;
368 		up_read(&s->lock);
369 
370 		if (active) {
371 			if (snap_src)
372 				*snap_src = s;
373 		} else if (snap_dest)
374 			*snap_dest = s;
375 
376 		count++;
377 	}
378 
379 out:
380 	return count;
381 }
382 
383 /*
384  * On success, returns 1 if this snapshot is a handover destination,
385  * otherwise returns 0.
386  */
387 static int __validate_exception_handover(struct dm_snapshot *snap)
388 {
389 	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
390 	struct dm_snapshot *snap_merge = NULL;
391 
392 	/* Does snapshot need exceptions handed over to it? */
393 	if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
394 					  &snap_merge) == 2) ||
395 	    snap_dest) {
396 		snap->ti->error = "Snapshot cow pairing for exception "
397 				  "table handover failed";
398 		return -EINVAL;
399 	}
400 
401 	/*
402 	 * If no snap_src was found, snap cannot become a handover
403 	 * destination.
404 	 */
405 	if (!snap_src)
406 		return 0;
407 
408 	/*
409 	 * Non-snapshot-merge handover?
410 	 */
411 	if (!dm_target_is_snapshot_merge(snap->ti))
412 		return 1;
413 
414 	/*
415 	 * Do not allow more than one merging snapshot.
416 	 */
417 	if (snap_merge) {
418 		snap->ti->error = "A snapshot is already merging.";
419 		return -EINVAL;
420 	}
421 
422 	if (!snap_src->store->type->prepare_merge ||
423 	    !snap_src->store->type->commit_merge) {
424 		snap->ti->error = "Snapshot exception store does not "
425 				  "support snapshot-merge.";
426 		return -EINVAL;
427 	}
428 
429 	return 1;
430 }
431 
432 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
433 {
434 	struct dm_snapshot *l;
435 
436 	/* Sort the list according to chunk size, largest-first smallest-last */
437 	list_for_each_entry(l, &o->snapshots, list)
438 		if (l->store->chunk_size < s->store->chunk_size)
439 			break;
440 	list_add_tail(&s->list, &l->list);
441 }
442 
443 /*
444  * Make a note of the snapshot and its origin so we can look it
445  * up when the origin has a write on it.
446  *
447  * Also validate snapshot exception store handovers.
448  * On success, returns 1 if this registration is a handover destination,
449  * otherwise returns 0.
450  */
451 static int register_snapshot(struct dm_snapshot *snap)
452 {
453 	struct origin *o, *new_o = NULL;
454 	struct block_device *bdev = snap->origin->bdev;
455 	int r = 0;
456 
457 	new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
458 	if (!new_o)
459 		return -ENOMEM;
460 
461 	down_write(&_origins_lock);
462 
463 	r = __validate_exception_handover(snap);
464 	if (r < 0) {
465 		kfree(new_o);
466 		goto out;
467 	}
468 
469 	o = __lookup_origin(bdev);
470 	if (o)
471 		kfree(new_o);
472 	else {
473 		/* New origin */
474 		o = new_o;
475 
476 		/* Initialise the struct */
477 		INIT_LIST_HEAD(&o->snapshots);
478 		o->bdev = bdev;
479 
480 		__insert_origin(o);
481 	}
482 
483 	__insert_snapshot(o, snap);
484 
485 out:
486 	up_write(&_origins_lock);
487 
488 	return r;
489 }
490 
491 /*
492  * Move snapshot to correct place in list according to chunk size.
493  */
494 static void reregister_snapshot(struct dm_snapshot *s)
495 {
496 	struct block_device *bdev = s->origin->bdev;
497 
498 	down_write(&_origins_lock);
499 
500 	list_del(&s->list);
501 	__insert_snapshot(__lookup_origin(bdev), s);
502 
503 	up_write(&_origins_lock);
504 }
505 
506 static void unregister_snapshot(struct dm_snapshot *s)
507 {
508 	struct origin *o;
509 
510 	down_write(&_origins_lock);
511 	o = __lookup_origin(s->origin->bdev);
512 
513 	list_del(&s->list);
514 	if (o && list_empty(&o->snapshots)) {
515 		list_del(&o->hash_list);
516 		kfree(o);
517 	}
518 
519 	up_write(&_origins_lock);
520 }
521 
522 /*
523  * Implementation of the exception hash tables.
524  * The lowest hash_shift bits of the chunk number are ignored, allowing
525  * some consecutive chunks to be grouped together.
526  */
527 static int dm_exception_table_init(struct dm_exception_table *et,
528 				   uint32_t size, unsigned hash_shift)
529 {
530 	unsigned int i;
531 
532 	et->hash_shift = hash_shift;
533 	et->hash_mask = size - 1;
534 	et->table = dm_vcalloc(size, sizeof(struct list_head));
535 	if (!et->table)
536 		return -ENOMEM;
537 
538 	for (i = 0; i < size; i++)
539 		INIT_LIST_HEAD(et->table + i);
540 
541 	return 0;
542 }
543 
544 static void dm_exception_table_exit(struct dm_exception_table *et,
545 				    struct kmem_cache *mem)
546 {
547 	struct list_head *slot;
548 	struct dm_exception *ex, *next;
549 	int i, size;
550 
551 	size = et->hash_mask + 1;
552 	for (i = 0; i < size; i++) {
553 		slot = et->table + i;
554 
555 		list_for_each_entry_safe (ex, next, slot, hash_list)
556 			kmem_cache_free(mem, ex);
557 	}
558 
559 	vfree(et->table);
560 }
561 
562 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
563 {
564 	return (chunk >> et->hash_shift) & et->hash_mask;
565 }
566 
567 static void dm_remove_exception(struct dm_exception *e)
568 {
569 	list_del(&e->hash_list);
570 }
571 
572 /*
573  * Return the exception data for a sector, or NULL if not
574  * remapped.
575  */
576 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
577 						chunk_t chunk)
578 {
579 	struct list_head *slot;
580 	struct dm_exception *e;
581 
582 	slot = &et->table[exception_hash(et, chunk)];
583 	list_for_each_entry (e, slot, hash_list)
584 		if (chunk >= e->old_chunk &&
585 		    chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
586 			return e;
587 
588 	return NULL;
589 }
590 
591 static struct dm_exception *alloc_completed_exception(void)
592 {
593 	struct dm_exception *e;
594 
595 	e = kmem_cache_alloc(exception_cache, GFP_NOIO);
596 	if (!e)
597 		e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
598 
599 	return e;
600 }
601 
602 static void free_completed_exception(struct dm_exception *e)
603 {
604 	kmem_cache_free(exception_cache, e);
605 }
606 
607 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
608 {
609 	struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
610 							     GFP_NOIO);
611 
612 	atomic_inc(&s->pending_exceptions_count);
613 	pe->snap = s;
614 
615 	return pe;
616 }
617 
618 static void free_pending_exception(struct dm_snap_pending_exception *pe)
619 {
620 	struct dm_snapshot *s = pe->snap;
621 
622 	mempool_free(pe, s->pending_pool);
623 	smp_mb__before_atomic_dec();
624 	atomic_dec(&s->pending_exceptions_count);
625 }
626 
627 static void dm_insert_exception(struct dm_exception_table *eh,
628 				struct dm_exception *new_e)
629 {
630 	struct list_head *l;
631 	struct dm_exception *e = NULL;
632 
633 	l = &eh->table[exception_hash(eh, new_e->old_chunk)];
634 
635 	/* Add immediately if this table doesn't support consecutive chunks */
636 	if (!eh->hash_shift)
637 		goto out;
638 
639 	/* List is ordered by old_chunk */
640 	list_for_each_entry_reverse(e, l, hash_list) {
641 		/* Insert after an existing chunk? */
642 		if (new_e->old_chunk == (e->old_chunk +
643 					 dm_consecutive_chunk_count(e) + 1) &&
644 		    new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
645 					 dm_consecutive_chunk_count(e) + 1)) {
646 			dm_consecutive_chunk_count_inc(e);
647 			free_completed_exception(new_e);
648 			return;
649 		}
650 
651 		/* Insert before an existing chunk? */
652 		if (new_e->old_chunk == (e->old_chunk - 1) &&
653 		    new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
654 			dm_consecutive_chunk_count_inc(e);
655 			e->old_chunk--;
656 			e->new_chunk--;
657 			free_completed_exception(new_e);
658 			return;
659 		}
660 
661 		if (new_e->old_chunk > e->old_chunk)
662 			break;
663 	}
664 
665 out:
666 	list_add(&new_e->hash_list, e ? &e->hash_list : l);
667 }
668 
669 /*
670  * Callback used by the exception stores to load exceptions when
671  * initialising.
672  */
673 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
674 {
675 	struct dm_snapshot *s = context;
676 	struct dm_exception *e;
677 
678 	e = alloc_completed_exception();
679 	if (!e)
680 		return -ENOMEM;
681 
682 	e->old_chunk = old;
683 
684 	/* Consecutive_count is implicitly initialised to zero */
685 	e->new_chunk = new;
686 
687 	dm_insert_exception(&s->complete, e);
688 
689 	return 0;
690 }
691 
692 /*
693  * Return a minimum chunk size of all snapshots that have the specified origin.
694  * Return zero if the origin has no snapshots.
695  */
696 static uint32_t __minimum_chunk_size(struct origin *o)
697 {
698 	struct dm_snapshot *snap;
699 	unsigned chunk_size = 0;
700 
701 	if (o)
702 		list_for_each_entry(snap, &o->snapshots, list)
703 			chunk_size = min_not_zero(chunk_size,
704 						  snap->store->chunk_size);
705 
706 	return (uint32_t) chunk_size;
707 }
708 
709 /*
710  * Hard coded magic.
711  */
712 static int calc_max_buckets(void)
713 {
714 	/* use a fixed size of 2MB */
715 	unsigned long mem = 2 * 1024 * 1024;
716 	mem /= sizeof(struct list_head);
717 
718 	return mem;
719 }
720 
721 /*
722  * Allocate room for a suitable hash table.
723  */
724 static int init_hash_tables(struct dm_snapshot *s)
725 {
726 	sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
727 
728 	/*
729 	 * Calculate based on the size of the original volume or
730 	 * the COW volume...
731 	 */
732 	cow_dev_size = get_dev_size(s->cow->bdev);
733 	origin_dev_size = get_dev_size(s->origin->bdev);
734 	max_buckets = calc_max_buckets();
735 
736 	hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
737 	hash_size = min(hash_size, max_buckets);
738 
739 	if (hash_size < 64)
740 		hash_size = 64;
741 	hash_size = rounddown_pow_of_two(hash_size);
742 	if (dm_exception_table_init(&s->complete, hash_size,
743 				    DM_CHUNK_CONSECUTIVE_BITS))
744 		return -ENOMEM;
745 
746 	/*
747 	 * Allocate hash table for in-flight exceptions
748 	 * Make this smaller than the real hash table
749 	 */
750 	hash_size >>= 3;
751 	if (hash_size < 64)
752 		hash_size = 64;
753 
754 	if (dm_exception_table_init(&s->pending, hash_size, 0)) {
755 		dm_exception_table_exit(&s->complete, exception_cache);
756 		return -ENOMEM;
757 	}
758 
759 	return 0;
760 }
761 
762 static void merge_shutdown(struct dm_snapshot *s)
763 {
764 	clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
765 	smp_mb__after_clear_bit();
766 	wake_up_bit(&s->state_bits, RUNNING_MERGE);
767 }
768 
769 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
770 {
771 	s->first_merging_chunk = 0;
772 	s->num_merging_chunks = 0;
773 
774 	return bio_list_get(&s->bios_queued_during_merge);
775 }
776 
777 /*
778  * Remove one chunk from the index of completed exceptions.
779  */
780 static int __remove_single_exception_chunk(struct dm_snapshot *s,
781 					   chunk_t old_chunk)
782 {
783 	struct dm_exception *e;
784 
785 	e = dm_lookup_exception(&s->complete, old_chunk);
786 	if (!e) {
787 		DMERR("Corruption detected: exception for block %llu is "
788 		      "on disk but not in memory",
789 		      (unsigned long long)old_chunk);
790 		return -EINVAL;
791 	}
792 
793 	/*
794 	 * If this is the only chunk using this exception, remove exception.
795 	 */
796 	if (!dm_consecutive_chunk_count(e)) {
797 		dm_remove_exception(e);
798 		free_completed_exception(e);
799 		return 0;
800 	}
801 
802 	/*
803 	 * The chunk may be either at the beginning or the end of a
804 	 * group of consecutive chunks - never in the middle.  We are
805 	 * removing chunks in the opposite order to that in which they
806 	 * were added, so this should always be true.
807 	 * Decrement the consecutive chunk counter and adjust the
808 	 * starting point if necessary.
809 	 */
810 	if (old_chunk == e->old_chunk) {
811 		e->old_chunk++;
812 		e->new_chunk++;
813 	} else if (old_chunk != e->old_chunk +
814 		   dm_consecutive_chunk_count(e)) {
815 		DMERR("Attempt to merge block %llu from the "
816 		      "middle of a chunk range [%llu - %llu]",
817 		      (unsigned long long)old_chunk,
818 		      (unsigned long long)e->old_chunk,
819 		      (unsigned long long)
820 		      e->old_chunk + dm_consecutive_chunk_count(e));
821 		return -EINVAL;
822 	}
823 
824 	dm_consecutive_chunk_count_dec(e);
825 
826 	return 0;
827 }
828 
829 static void flush_bios(struct bio *bio);
830 
831 static int remove_single_exception_chunk(struct dm_snapshot *s)
832 {
833 	struct bio *b = NULL;
834 	int r;
835 	chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
836 
837 	down_write(&s->lock);
838 
839 	/*
840 	 * Process chunks (and associated exceptions) in reverse order
841 	 * so that dm_consecutive_chunk_count_dec() accounting works.
842 	 */
843 	do {
844 		r = __remove_single_exception_chunk(s, old_chunk);
845 		if (r)
846 			goto out;
847 	} while (old_chunk-- > s->first_merging_chunk);
848 
849 	b = __release_queued_bios_after_merge(s);
850 
851 out:
852 	up_write(&s->lock);
853 	if (b)
854 		flush_bios(b);
855 
856 	return r;
857 }
858 
859 static int origin_write_extent(struct dm_snapshot *merging_snap,
860 			       sector_t sector, unsigned chunk_size);
861 
862 static void merge_callback(int read_err, unsigned long write_err,
863 			   void *context);
864 
865 static uint64_t read_pending_exceptions_done_count(void)
866 {
867 	uint64_t pending_exceptions_done;
868 
869 	spin_lock(&_pending_exceptions_done_spinlock);
870 	pending_exceptions_done = _pending_exceptions_done_count;
871 	spin_unlock(&_pending_exceptions_done_spinlock);
872 
873 	return pending_exceptions_done;
874 }
875 
876 static void increment_pending_exceptions_done_count(void)
877 {
878 	spin_lock(&_pending_exceptions_done_spinlock);
879 	_pending_exceptions_done_count++;
880 	spin_unlock(&_pending_exceptions_done_spinlock);
881 
882 	wake_up_all(&_pending_exceptions_done);
883 }
884 
885 static void snapshot_merge_next_chunks(struct dm_snapshot *s)
886 {
887 	int i, linear_chunks;
888 	chunk_t old_chunk, new_chunk;
889 	struct dm_io_region src, dest;
890 	sector_t io_size;
891 	uint64_t previous_count;
892 
893 	BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
894 	if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
895 		goto shut;
896 
897 	/*
898 	 * valid flag never changes during merge, so no lock required.
899 	 */
900 	if (!s->valid) {
901 		DMERR("Snapshot is invalid: can't merge");
902 		goto shut;
903 	}
904 
905 	linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
906 						      &new_chunk);
907 	if (linear_chunks <= 0) {
908 		if (linear_chunks < 0) {
909 			DMERR("Read error in exception store: "
910 			      "shutting down merge");
911 			down_write(&s->lock);
912 			s->merge_failed = 1;
913 			up_write(&s->lock);
914 		}
915 		goto shut;
916 	}
917 
918 	/* Adjust old_chunk and new_chunk to reflect start of linear region */
919 	old_chunk = old_chunk + 1 - linear_chunks;
920 	new_chunk = new_chunk + 1 - linear_chunks;
921 
922 	/*
923 	 * Use one (potentially large) I/O to copy all 'linear_chunks'
924 	 * from the exception store to the origin
925 	 */
926 	io_size = linear_chunks * s->store->chunk_size;
927 
928 	dest.bdev = s->origin->bdev;
929 	dest.sector = chunk_to_sector(s->store, old_chunk);
930 	dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
931 
932 	src.bdev = s->cow->bdev;
933 	src.sector = chunk_to_sector(s->store, new_chunk);
934 	src.count = dest.count;
935 
936 	/*
937 	 * Reallocate any exceptions needed in other snapshots then
938 	 * wait for the pending exceptions to complete.
939 	 * Each time any pending exception (globally on the system)
940 	 * completes we are woken and repeat the process to find out
941 	 * if we can proceed.  While this may not seem a particularly
942 	 * efficient algorithm, it is not expected to have any
943 	 * significant impact on performance.
944 	 */
945 	previous_count = read_pending_exceptions_done_count();
946 	while (origin_write_extent(s, dest.sector, io_size)) {
947 		wait_event(_pending_exceptions_done,
948 			   (read_pending_exceptions_done_count() !=
949 			    previous_count));
950 		/* Retry after the wait, until all exceptions are done. */
951 		previous_count = read_pending_exceptions_done_count();
952 	}
953 
954 	down_write(&s->lock);
955 	s->first_merging_chunk = old_chunk;
956 	s->num_merging_chunks = linear_chunks;
957 	up_write(&s->lock);
958 
959 	/* Wait until writes to all 'linear_chunks' drain */
960 	for (i = 0; i < linear_chunks; i++)
961 		__check_for_conflicting_io(s, old_chunk + i);
962 
963 	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
964 	return;
965 
966 shut:
967 	merge_shutdown(s);
968 }
969 
970 static void error_bios(struct bio *bio);
971 
972 static void merge_callback(int read_err, unsigned long write_err, void *context)
973 {
974 	struct dm_snapshot *s = context;
975 	struct bio *b = NULL;
976 
977 	if (read_err || write_err) {
978 		if (read_err)
979 			DMERR("Read error: shutting down merge.");
980 		else
981 			DMERR("Write error: shutting down merge.");
982 		goto shut;
983 	}
984 
985 	if (s->store->type->commit_merge(s->store,
986 					 s->num_merging_chunks) < 0) {
987 		DMERR("Write error in exception store: shutting down merge");
988 		goto shut;
989 	}
990 
991 	if (remove_single_exception_chunk(s) < 0)
992 		goto shut;
993 
994 	snapshot_merge_next_chunks(s);
995 
996 	return;
997 
998 shut:
999 	down_write(&s->lock);
1000 	s->merge_failed = 1;
1001 	b = __release_queued_bios_after_merge(s);
1002 	up_write(&s->lock);
1003 	error_bios(b);
1004 
1005 	merge_shutdown(s);
1006 }
1007 
1008 static void start_merge(struct dm_snapshot *s)
1009 {
1010 	if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1011 		snapshot_merge_next_chunks(s);
1012 }
1013 
1014 static int wait_schedule(void *ptr)
1015 {
1016 	schedule();
1017 
1018 	return 0;
1019 }
1020 
1021 /*
1022  * Stop the merging process and wait until it finishes.
1023  */
1024 static void stop_merge(struct dm_snapshot *s)
1025 {
1026 	set_bit(SHUTDOWN_MERGE, &s->state_bits);
1027 	wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule,
1028 		    TASK_UNINTERRUPTIBLE);
1029 	clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1030 }
1031 
1032 /*
1033  * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
1034  */
1035 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1036 {
1037 	struct dm_snapshot *s;
1038 	int i;
1039 	int r = -EINVAL;
1040 	char *origin_path, *cow_path;
1041 	unsigned args_used, num_flush_requests = 1;
1042 	fmode_t origin_mode = FMODE_READ;
1043 
1044 	if (argc != 4) {
1045 		ti->error = "requires exactly 4 arguments";
1046 		r = -EINVAL;
1047 		goto bad;
1048 	}
1049 
1050 	if (dm_target_is_snapshot_merge(ti)) {
1051 		num_flush_requests = 2;
1052 		origin_mode = FMODE_WRITE;
1053 	}
1054 
1055 	s = kmalloc(sizeof(*s), GFP_KERNEL);
1056 	if (!s) {
1057 		ti->error = "Cannot allocate private snapshot structure";
1058 		r = -ENOMEM;
1059 		goto bad;
1060 	}
1061 
1062 	origin_path = argv[0];
1063 	argv++;
1064 	argc--;
1065 
1066 	r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1067 	if (r) {
1068 		ti->error = "Cannot get origin device";
1069 		goto bad_origin;
1070 	}
1071 
1072 	cow_path = argv[0];
1073 	argv++;
1074 	argc--;
1075 
1076 	r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1077 	if (r) {
1078 		ti->error = "Cannot get COW device";
1079 		goto bad_cow;
1080 	}
1081 
1082 	r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1083 	if (r) {
1084 		ti->error = "Couldn't create exception store";
1085 		r = -EINVAL;
1086 		goto bad_store;
1087 	}
1088 
1089 	argv += args_used;
1090 	argc -= args_used;
1091 
1092 	s->ti = ti;
1093 	s->valid = 1;
1094 	s->active = 0;
1095 	atomic_set(&s->pending_exceptions_count, 0);
1096 	init_rwsem(&s->lock);
1097 	INIT_LIST_HEAD(&s->list);
1098 	spin_lock_init(&s->pe_lock);
1099 	s->state_bits = 0;
1100 	s->merge_failed = 0;
1101 	s->first_merging_chunk = 0;
1102 	s->num_merging_chunks = 0;
1103 	bio_list_init(&s->bios_queued_during_merge);
1104 
1105 	/* Allocate hash table for COW data */
1106 	if (init_hash_tables(s)) {
1107 		ti->error = "Unable to allocate hash table space";
1108 		r = -ENOMEM;
1109 		goto bad_hash_tables;
1110 	}
1111 
1112 	s->kcopyd_client = dm_kcopyd_client_create();
1113 	if (IS_ERR(s->kcopyd_client)) {
1114 		r = PTR_ERR(s->kcopyd_client);
1115 		ti->error = "Could not create kcopyd client";
1116 		goto bad_kcopyd;
1117 	}
1118 
1119 	s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1120 	if (!s->pending_pool) {
1121 		ti->error = "Could not allocate mempool for pending exceptions";
1122 		goto bad_pending_pool;
1123 	}
1124 
1125 	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1126 		INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1127 
1128 	spin_lock_init(&s->tracked_chunk_lock);
1129 
1130 	ti->private = s;
1131 	ti->num_flush_requests = num_flush_requests;
1132 	ti->per_bio_data_size = sizeof(struct dm_snap_tracked_chunk);
1133 
1134 	/* Add snapshot to the list of snapshots for this origin */
1135 	/* Exceptions aren't triggered till snapshot_resume() is called */
1136 	r = register_snapshot(s);
1137 	if (r == -ENOMEM) {
1138 		ti->error = "Snapshot origin struct allocation failed";
1139 		goto bad_load_and_register;
1140 	} else if (r < 0) {
1141 		/* invalid handover, register_snapshot has set ti->error */
1142 		goto bad_load_and_register;
1143 	}
1144 
1145 	/*
1146 	 * Metadata must only be loaded into one table at once, so skip this
1147 	 * if metadata will be handed over during resume.
1148 	 * Chunk size will be set during the handover - set it to zero to
1149 	 * ensure it's ignored.
1150 	 */
1151 	if (r > 0) {
1152 		s->store->chunk_size = 0;
1153 		return 0;
1154 	}
1155 
1156 	r = s->store->type->read_metadata(s->store, dm_add_exception,
1157 					  (void *)s);
1158 	if (r < 0) {
1159 		ti->error = "Failed to read snapshot metadata";
1160 		goto bad_read_metadata;
1161 	} else if (r > 0) {
1162 		s->valid = 0;
1163 		DMWARN("Snapshot is marked invalid.");
1164 	}
1165 
1166 	if (!s->store->chunk_size) {
1167 		ti->error = "Chunk size not set";
1168 		goto bad_read_metadata;
1169 	}
1170 
1171 	r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1172 	if (r)
1173 		goto bad_read_metadata;
1174 
1175 	return 0;
1176 
1177 bad_read_metadata:
1178 	unregister_snapshot(s);
1179 
1180 bad_load_and_register:
1181 	mempool_destroy(s->pending_pool);
1182 
1183 bad_pending_pool:
1184 	dm_kcopyd_client_destroy(s->kcopyd_client);
1185 
1186 bad_kcopyd:
1187 	dm_exception_table_exit(&s->pending, pending_cache);
1188 	dm_exception_table_exit(&s->complete, exception_cache);
1189 
1190 bad_hash_tables:
1191 	dm_exception_store_destroy(s->store);
1192 
1193 bad_store:
1194 	dm_put_device(ti, s->cow);
1195 
1196 bad_cow:
1197 	dm_put_device(ti, s->origin);
1198 
1199 bad_origin:
1200 	kfree(s);
1201 
1202 bad:
1203 	return r;
1204 }
1205 
1206 static void __free_exceptions(struct dm_snapshot *s)
1207 {
1208 	dm_kcopyd_client_destroy(s->kcopyd_client);
1209 	s->kcopyd_client = NULL;
1210 
1211 	dm_exception_table_exit(&s->pending, pending_cache);
1212 	dm_exception_table_exit(&s->complete, exception_cache);
1213 }
1214 
1215 static void __handover_exceptions(struct dm_snapshot *snap_src,
1216 				  struct dm_snapshot *snap_dest)
1217 {
1218 	union {
1219 		struct dm_exception_table table_swap;
1220 		struct dm_exception_store *store_swap;
1221 	} u;
1222 
1223 	/*
1224 	 * Swap all snapshot context information between the two instances.
1225 	 */
1226 	u.table_swap = snap_dest->complete;
1227 	snap_dest->complete = snap_src->complete;
1228 	snap_src->complete = u.table_swap;
1229 
1230 	u.store_swap = snap_dest->store;
1231 	snap_dest->store = snap_src->store;
1232 	snap_src->store = u.store_swap;
1233 
1234 	snap_dest->store->snap = snap_dest;
1235 	snap_src->store->snap = snap_src;
1236 
1237 	snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1238 	snap_dest->valid = snap_src->valid;
1239 
1240 	/*
1241 	 * Set source invalid to ensure it receives no further I/O.
1242 	 */
1243 	snap_src->valid = 0;
1244 }
1245 
1246 static void snapshot_dtr(struct dm_target *ti)
1247 {
1248 #ifdef CONFIG_DM_DEBUG
1249 	int i;
1250 #endif
1251 	struct dm_snapshot *s = ti->private;
1252 	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1253 
1254 	down_read(&_origins_lock);
1255 	/* Check whether exception handover must be cancelled */
1256 	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1257 	if (snap_src && snap_dest && (s == snap_src)) {
1258 		down_write(&snap_dest->lock);
1259 		snap_dest->valid = 0;
1260 		up_write(&snap_dest->lock);
1261 		DMERR("Cancelling snapshot handover.");
1262 	}
1263 	up_read(&_origins_lock);
1264 
1265 	if (dm_target_is_snapshot_merge(ti))
1266 		stop_merge(s);
1267 
1268 	/* Prevent further origin writes from using this snapshot. */
1269 	/* After this returns there can be no new kcopyd jobs. */
1270 	unregister_snapshot(s);
1271 
1272 	while (atomic_read(&s->pending_exceptions_count))
1273 		msleep(1);
1274 	/*
1275 	 * Ensure instructions in mempool_destroy aren't reordered
1276 	 * before atomic_read.
1277 	 */
1278 	smp_mb();
1279 
1280 #ifdef CONFIG_DM_DEBUG
1281 	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1282 		BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1283 #endif
1284 
1285 	__free_exceptions(s);
1286 
1287 	mempool_destroy(s->pending_pool);
1288 
1289 	dm_exception_store_destroy(s->store);
1290 
1291 	dm_put_device(ti, s->cow);
1292 
1293 	dm_put_device(ti, s->origin);
1294 
1295 	kfree(s);
1296 }
1297 
1298 /*
1299  * Flush a list of buffers.
1300  */
1301 static void flush_bios(struct bio *bio)
1302 {
1303 	struct bio *n;
1304 
1305 	while (bio) {
1306 		n = bio->bi_next;
1307 		bio->bi_next = NULL;
1308 		generic_make_request(bio);
1309 		bio = n;
1310 	}
1311 }
1312 
1313 static int do_origin(struct dm_dev *origin, struct bio *bio);
1314 
1315 /*
1316  * Flush a list of buffers.
1317  */
1318 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1319 {
1320 	struct bio *n;
1321 	int r;
1322 
1323 	while (bio) {
1324 		n = bio->bi_next;
1325 		bio->bi_next = NULL;
1326 		r = do_origin(s->origin, bio);
1327 		if (r == DM_MAPIO_REMAPPED)
1328 			generic_make_request(bio);
1329 		bio = n;
1330 	}
1331 }
1332 
1333 /*
1334  * Error a list of buffers.
1335  */
1336 static void error_bios(struct bio *bio)
1337 {
1338 	struct bio *n;
1339 
1340 	while (bio) {
1341 		n = bio->bi_next;
1342 		bio->bi_next = NULL;
1343 		bio_io_error(bio);
1344 		bio = n;
1345 	}
1346 }
1347 
1348 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1349 {
1350 	if (!s->valid)
1351 		return;
1352 
1353 	if (err == -EIO)
1354 		DMERR("Invalidating snapshot: Error reading/writing.");
1355 	else if (err == -ENOMEM)
1356 		DMERR("Invalidating snapshot: Unable to allocate exception.");
1357 
1358 	if (s->store->type->drop_snapshot)
1359 		s->store->type->drop_snapshot(s->store);
1360 
1361 	s->valid = 0;
1362 
1363 	dm_table_event(s->ti->table);
1364 }
1365 
1366 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
1367 {
1368 	struct dm_exception *e;
1369 	struct dm_snapshot *s = pe->snap;
1370 	struct bio *origin_bios = NULL;
1371 	struct bio *snapshot_bios = NULL;
1372 	struct bio *full_bio = NULL;
1373 	int error = 0;
1374 
1375 	if (!success) {
1376 		/* Read/write error - snapshot is unusable */
1377 		down_write(&s->lock);
1378 		__invalidate_snapshot(s, -EIO);
1379 		error = 1;
1380 		goto out;
1381 	}
1382 
1383 	e = alloc_completed_exception();
1384 	if (!e) {
1385 		down_write(&s->lock);
1386 		__invalidate_snapshot(s, -ENOMEM);
1387 		error = 1;
1388 		goto out;
1389 	}
1390 	*e = pe->e;
1391 
1392 	down_write(&s->lock);
1393 	if (!s->valid) {
1394 		free_completed_exception(e);
1395 		error = 1;
1396 		goto out;
1397 	}
1398 
1399 	/* Check for conflicting reads */
1400 	__check_for_conflicting_io(s, pe->e.old_chunk);
1401 
1402 	/*
1403 	 * Add a proper exception, and remove the
1404 	 * in-flight exception from the list.
1405 	 */
1406 	dm_insert_exception(&s->complete, e);
1407 
1408 out:
1409 	dm_remove_exception(&pe->e);
1410 	snapshot_bios = bio_list_get(&pe->snapshot_bios);
1411 	origin_bios = bio_list_get(&pe->origin_bios);
1412 	full_bio = pe->full_bio;
1413 	if (full_bio) {
1414 		full_bio->bi_end_io = pe->full_bio_end_io;
1415 		full_bio->bi_private = pe->full_bio_private;
1416 	}
1417 	free_pending_exception(pe);
1418 
1419 	increment_pending_exceptions_done_count();
1420 
1421 	up_write(&s->lock);
1422 
1423 	/* Submit any pending write bios */
1424 	if (error) {
1425 		if (full_bio)
1426 			bio_io_error(full_bio);
1427 		error_bios(snapshot_bios);
1428 	} else {
1429 		if (full_bio)
1430 			bio_endio(full_bio, 0);
1431 		flush_bios(snapshot_bios);
1432 	}
1433 
1434 	retry_origin_bios(s, origin_bios);
1435 }
1436 
1437 static void commit_callback(void *context, int success)
1438 {
1439 	struct dm_snap_pending_exception *pe = context;
1440 
1441 	pending_complete(pe, success);
1442 }
1443 
1444 /*
1445  * Called when the copy I/O has finished.  kcopyd actually runs
1446  * this code so don't block.
1447  */
1448 static void copy_callback(int read_err, unsigned long write_err, void *context)
1449 {
1450 	struct dm_snap_pending_exception *pe = context;
1451 	struct dm_snapshot *s = pe->snap;
1452 
1453 	if (read_err || write_err)
1454 		pending_complete(pe, 0);
1455 
1456 	else
1457 		/* Update the metadata if we are persistent */
1458 		s->store->type->commit_exception(s->store, &pe->e,
1459 						 commit_callback, pe);
1460 }
1461 
1462 /*
1463  * Dispatches the copy operation to kcopyd.
1464  */
1465 static void start_copy(struct dm_snap_pending_exception *pe)
1466 {
1467 	struct dm_snapshot *s = pe->snap;
1468 	struct dm_io_region src, dest;
1469 	struct block_device *bdev = s->origin->bdev;
1470 	sector_t dev_size;
1471 
1472 	dev_size = get_dev_size(bdev);
1473 
1474 	src.bdev = bdev;
1475 	src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1476 	src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1477 
1478 	dest.bdev = s->cow->bdev;
1479 	dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1480 	dest.count = src.count;
1481 
1482 	/* Hand over to kcopyd */
1483 	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1484 }
1485 
1486 static void full_bio_end_io(struct bio *bio, int error)
1487 {
1488 	void *callback_data = bio->bi_private;
1489 
1490 	dm_kcopyd_do_callback(callback_data, 0, error ? 1 : 0);
1491 }
1492 
1493 static void start_full_bio(struct dm_snap_pending_exception *pe,
1494 			   struct bio *bio)
1495 {
1496 	struct dm_snapshot *s = pe->snap;
1497 	void *callback_data;
1498 
1499 	pe->full_bio = bio;
1500 	pe->full_bio_end_io = bio->bi_end_io;
1501 	pe->full_bio_private = bio->bi_private;
1502 
1503 	callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1504 						   copy_callback, pe);
1505 
1506 	bio->bi_end_io = full_bio_end_io;
1507 	bio->bi_private = callback_data;
1508 
1509 	generic_make_request(bio);
1510 }
1511 
1512 static struct dm_snap_pending_exception *
1513 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1514 {
1515 	struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1516 
1517 	if (!e)
1518 		return NULL;
1519 
1520 	return container_of(e, struct dm_snap_pending_exception, e);
1521 }
1522 
1523 /*
1524  * Looks to see if this snapshot already has a pending exception
1525  * for this chunk, otherwise it allocates a new one and inserts
1526  * it into the pending table.
1527  *
1528  * NOTE: a write lock must be held on snap->lock before calling
1529  * this.
1530  */
1531 static struct dm_snap_pending_exception *
1532 __find_pending_exception(struct dm_snapshot *s,
1533 			 struct dm_snap_pending_exception *pe, chunk_t chunk)
1534 {
1535 	struct dm_snap_pending_exception *pe2;
1536 
1537 	pe2 = __lookup_pending_exception(s, chunk);
1538 	if (pe2) {
1539 		free_pending_exception(pe);
1540 		return pe2;
1541 	}
1542 
1543 	pe->e.old_chunk = chunk;
1544 	bio_list_init(&pe->origin_bios);
1545 	bio_list_init(&pe->snapshot_bios);
1546 	pe->started = 0;
1547 	pe->full_bio = NULL;
1548 
1549 	if (s->store->type->prepare_exception(s->store, &pe->e)) {
1550 		free_pending_exception(pe);
1551 		return NULL;
1552 	}
1553 
1554 	dm_insert_exception(&s->pending, &pe->e);
1555 
1556 	return pe;
1557 }
1558 
1559 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1560 			    struct bio *bio, chunk_t chunk)
1561 {
1562 	bio->bi_bdev = s->cow->bdev;
1563 	bio->bi_sector = chunk_to_sector(s->store,
1564 					 dm_chunk_number(e->new_chunk) +
1565 					 (chunk - e->old_chunk)) +
1566 					 (bio->bi_sector &
1567 					  s->store->chunk_mask);
1568 }
1569 
1570 static int snapshot_map(struct dm_target *ti, struct bio *bio)
1571 {
1572 	struct dm_exception *e;
1573 	struct dm_snapshot *s = ti->private;
1574 	int r = DM_MAPIO_REMAPPED;
1575 	chunk_t chunk;
1576 	struct dm_snap_pending_exception *pe = NULL;
1577 
1578 	init_tracked_chunk(bio);
1579 
1580 	if (bio->bi_rw & REQ_FLUSH) {
1581 		bio->bi_bdev = s->cow->bdev;
1582 		return DM_MAPIO_REMAPPED;
1583 	}
1584 
1585 	chunk = sector_to_chunk(s->store, bio->bi_sector);
1586 
1587 	/* Full snapshots are not usable */
1588 	/* To get here the table must be live so s->active is always set. */
1589 	if (!s->valid)
1590 		return -EIO;
1591 
1592 	/* FIXME: should only take write lock if we need
1593 	 * to copy an exception */
1594 	down_write(&s->lock);
1595 
1596 	if (!s->valid) {
1597 		r = -EIO;
1598 		goto out_unlock;
1599 	}
1600 
1601 	/* If the block is already remapped - use that, else remap it */
1602 	e = dm_lookup_exception(&s->complete, chunk);
1603 	if (e) {
1604 		remap_exception(s, e, bio, chunk);
1605 		goto out_unlock;
1606 	}
1607 
1608 	/*
1609 	 * Write to snapshot - higher level takes care of RW/RO
1610 	 * flags so we should only get this if we are
1611 	 * writeable.
1612 	 */
1613 	if (bio_rw(bio) == WRITE) {
1614 		pe = __lookup_pending_exception(s, chunk);
1615 		if (!pe) {
1616 			up_write(&s->lock);
1617 			pe = alloc_pending_exception(s);
1618 			down_write(&s->lock);
1619 
1620 			if (!s->valid) {
1621 				free_pending_exception(pe);
1622 				r = -EIO;
1623 				goto out_unlock;
1624 			}
1625 
1626 			e = dm_lookup_exception(&s->complete, chunk);
1627 			if (e) {
1628 				free_pending_exception(pe);
1629 				remap_exception(s, e, bio, chunk);
1630 				goto out_unlock;
1631 			}
1632 
1633 			pe = __find_pending_exception(s, pe, chunk);
1634 			if (!pe) {
1635 				__invalidate_snapshot(s, -ENOMEM);
1636 				r = -EIO;
1637 				goto out_unlock;
1638 			}
1639 		}
1640 
1641 		remap_exception(s, &pe->e, bio, chunk);
1642 
1643 		r = DM_MAPIO_SUBMITTED;
1644 
1645 		if (!pe->started &&
1646 		    bio->bi_size == (s->store->chunk_size << SECTOR_SHIFT)) {
1647 			pe->started = 1;
1648 			up_write(&s->lock);
1649 			start_full_bio(pe, bio);
1650 			goto out;
1651 		}
1652 
1653 		bio_list_add(&pe->snapshot_bios, bio);
1654 
1655 		if (!pe->started) {
1656 			/* this is protected by snap->lock */
1657 			pe->started = 1;
1658 			up_write(&s->lock);
1659 			start_copy(pe);
1660 			goto out;
1661 		}
1662 	} else {
1663 		bio->bi_bdev = s->origin->bdev;
1664 		track_chunk(s, bio, chunk);
1665 	}
1666 
1667 out_unlock:
1668 	up_write(&s->lock);
1669 out:
1670 	return r;
1671 }
1672 
1673 /*
1674  * A snapshot-merge target behaves like a combination of a snapshot
1675  * target and a snapshot-origin target.  It only generates new
1676  * exceptions in other snapshots and not in the one that is being
1677  * merged.
1678  *
1679  * For each chunk, if there is an existing exception, it is used to
1680  * redirect I/O to the cow device.  Otherwise I/O is sent to the origin,
1681  * which in turn might generate exceptions in other snapshots.
1682  * If merging is currently taking place on the chunk in question, the
1683  * I/O is deferred by adding it to s->bios_queued_during_merge.
1684  */
1685 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
1686 {
1687 	struct dm_exception *e;
1688 	struct dm_snapshot *s = ti->private;
1689 	int r = DM_MAPIO_REMAPPED;
1690 	chunk_t chunk;
1691 
1692 	init_tracked_chunk(bio);
1693 
1694 	if (bio->bi_rw & REQ_FLUSH) {
1695 		if (!dm_bio_get_target_request_nr(bio))
1696 			bio->bi_bdev = s->origin->bdev;
1697 		else
1698 			bio->bi_bdev = s->cow->bdev;
1699 		return DM_MAPIO_REMAPPED;
1700 	}
1701 
1702 	chunk = sector_to_chunk(s->store, bio->bi_sector);
1703 
1704 	down_write(&s->lock);
1705 
1706 	/* Full merging snapshots are redirected to the origin */
1707 	if (!s->valid)
1708 		goto redirect_to_origin;
1709 
1710 	/* If the block is already remapped - use that */
1711 	e = dm_lookup_exception(&s->complete, chunk);
1712 	if (e) {
1713 		/* Queue writes overlapping with chunks being merged */
1714 		if (bio_rw(bio) == WRITE &&
1715 		    chunk >= s->first_merging_chunk &&
1716 		    chunk < (s->first_merging_chunk +
1717 			     s->num_merging_chunks)) {
1718 			bio->bi_bdev = s->origin->bdev;
1719 			bio_list_add(&s->bios_queued_during_merge, bio);
1720 			r = DM_MAPIO_SUBMITTED;
1721 			goto out_unlock;
1722 		}
1723 
1724 		remap_exception(s, e, bio, chunk);
1725 
1726 		if (bio_rw(bio) == WRITE)
1727 			track_chunk(s, bio, chunk);
1728 		goto out_unlock;
1729 	}
1730 
1731 redirect_to_origin:
1732 	bio->bi_bdev = s->origin->bdev;
1733 
1734 	if (bio_rw(bio) == WRITE) {
1735 		up_write(&s->lock);
1736 		return do_origin(s->origin, bio);
1737 	}
1738 
1739 out_unlock:
1740 	up_write(&s->lock);
1741 
1742 	return r;
1743 }
1744 
1745 static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error)
1746 {
1747 	struct dm_snapshot *s = ti->private;
1748 
1749 	if (is_bio_tracked(bio))
1750 		stop_tracking_chunk(s, bio);
1751 
1752 	return 0;
1753 }
1754 
1755 static void snapshot_merge_presuspend(struct dm_target *ti)
1756 {
1757 	struct dm_snapshot *s = ti->private;
1758 
1759 	stop_merge(s);
1760 }
1761 
1762 static int snapshot_preresume(struct dm_target *ti)
1763 {
1764 	int r = 0;
1765 	struct dm_snapshot *s = ti->private;
1766 	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1767 
1768 	down_read(&_origins_lock);
1769 	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1770 	if (snap_src && snap_dest) {
1771 		down_read(&snap_src->lock);
1772 		if (s == snap_src) {
1773 			DMERR("Unable to resume snapshot source until "
1774 			      "handover completes.");
1775 			r = -EINVAL;
1776 		} else if (!dm_suspended(snap_src->ti)) {
1777 			DMERR("Unable to perform snapshot handover until "
1778 			      "source is suspended.");
1779 			r = -EINVAL;
1780 		}
1781 		up_read(&snap_src->lock);
1782 	}
1783 	up_read(&_origins_lock);
1784 
1785 	return r;
1786 }
1787 
1788 static void snapshot_resume(struct dm_target *ti)
1789 {
1790 	struct dm_snapshot *s = ti->private;
1791 	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1792 
1793 	down_read(&_origins_lock);
1794 	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1795 	if (snap_src && snap_dest) {
1796 		down_write(&snap_src->lock);
1797 		down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1798 		__handover_exceptions(snap_src, snap_dest);
1799 		up_write(&snap_dest->lock);
1800 		up_write(&snap_src->lock);
1801 	}
1802 	up_read(&_origins_lock);
1803 
1804 	/* Now we have correct chunk size, reregister */
1805 	reregister_snapshot(s);
1806 
1807 	down_write(&s->lock);
1808 	s->active = 1;
1809 	up_write(&s->lock);
1810 }
1811 
1812 static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
1813 {
1814 	uint32_t min_chunksize;
1815 
1816 	down_read(&_origins_lock);
1817 	min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1818 	up_read(&_origins_lock);
1819 
1820 	return min_chunksize;
1821 }
1822 
1823 static void snapshot_merge_resume(struct dm_target *ti)
1824 {
1825 	struct dm_snapshot *s = ti->private;
1826 
1827 	/*
1828 	 * Handover exceptions from existing snapshot.
1829 	 */
1830 	snapshot_resume(ti);
1831 
1832 	/*
1833 	 * snapshot-merge acts as an origin, so set ti->max_io_len
1834 	 */
1835 	ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
1836 
1837 	start_merge(s);
1838 }
1839 
1840 static int snapshot_status(struct dm_target *ti, status_type_t type,
1841 			   unsigned status_flags, char *result, unsigned maxlen)
1842 {
1843 	unsigned sz = 0;
1844 	struct dm_snapshot *snap = ti->private;
1845 
1846 	switch (type) {
1847 	case STATUSTYPE_INFO:
1848 
1849 		down_write(&snap->lock);
1850 
1851 		if (!snap->valid)
1852 			DMEMIT("Invalid");
1853 		else if (snap->merge_failed)
1854 			DMEMIT("Merge failed");
1855 		else {
1856 			if (snap->store->type->usage) {
1857 				sector_t total_sectors, sectors_allocated,
1858 					 metadata_sectors;
1859 				snap->store->type->usage(snap->store,
1860 							 &total_sectors,
1861 							 &sectors_allocated,
1862 							 &metadata_sectors);
1863 				DMEMIT("%llu/%llu %llu",
1864 				       (unsigned long long)sectors_allocated,
1865 				       (unsigned long long)total_sectors,
1866 				       (unsigned long long)metadata_sectors);
1867 			}
1868 			else
1869 				DMEMIT("Unknown");
1870 		}
1871 
1872 		up_write(&snap->lock);
1873 
1874 		break;
1875 
1876 	case STATUSTYPE_TABLE:
1877 		/*
1878 		 * kdevname returns a static pointer so we need
1879 		 * to make private copies if the output is to
1880 		 * make sense.
1881 		 */
1882 		DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1883 		snap->store->type->status(snap->store, type, result + sz,
1884 					  maxlen - sz);
1885 		break;
1886 	}
1887 
1888 	return 0;
1889 }
1890 
1891 static int snapshot_iterate_devices(struct dm_target *ti,
1892 				    iterate_devices_callout_fn fn, void *data)
1893 {
1894 	struct dm_snapshot *snap = ti->private;
1895 	int r;
1896 
1897 	r = fn(ti, snap->origin, 0, ti->len, data);
1898 
1899 	if (!r)
1900 		r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
1901 
1902 	return r;
1903 }
1904 
1905 
1906 /*-----------------------------------------------------------------
1907  * Origin methods
1908  *---------------------------------------------------------------*/
1909 
1910 /*
1911  * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
1912  * supplied bio was ignored.  The caller may submit it immediately.
1913  * (No remapping actually occurs as the origin is always a direct linear
1914  * map.)
1915  *
1916  * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
1917  * and any supplied bio is added to a list to be submitted once all
1918  * the necessary exceptions exist.
1919  */
1920 static int __origin_write(struct list_head *snapshots, sector_t sector,
1921 			  struct bio *bio)
1922 {
1923 	int r = DM_MAPIO_REMAPPED;
1924 	struct dm_snapshot *snap;
1925 	struct dm_exception *e;
1926 	struct dm_snap_pending_exception *pe;
1927 	struct dm_snap_pending_exception *pe_to_start_now = NULL;
1928 	struct dm_snap_pending_exception *pe_to_start_last = NULL;
1929 	chunk_t chunk;
1930 
1931 	/* Do all the snapshots on this origin */
1932 	list_for_each_entry (snap, snapshots, list) {
1933 		/*
1934 		 * Don't make new exceptions in a merging snapshot
1935 		 * because it has effectively been deleted
1936 		 */
1937 		if (dm_target_is_snapshot_merge(snap->ti))
1938 			continue;
1939 
1940 		down_write(&snap->lock);
1941 
1942 		/* Only deal with valid and active snapshots */
1943 		if (!snap->valid || !snap->active)
1944 			goto next_snapshot;
1945 
1946 		/* Nothing to do if writing beyond end of snapshot */
1947 		if (sector >= dm_table_get_size(snap->ti->table))
1948 			goto next_snapshot;
1949 
1950 		/*
1951 		 * Remember, different snapshots can have
1952 		 * different chunk sizes.
1953 		 */
1954 		chunk = sector_to_chunk(snap->store, sector);
1955 
1956 		/*
1957 		 * Check exception table to see if block
1958 		 * is already remapped in this snapshot
1959 		 * and trigger an exception if not.
1960 		 */
1961 		e = dm_lookup_exception(&snap->complete, chunk);
1962 		if (e)
1963 			goto next_snapshot;
1964 
1965 		pe = __lookup_pending_exception(snap, chunk);
1966 		if (!pe) {
1967 			up_write(&snap->lock);
1968 			pe = alloc_pending_exception(snap);
1969 			down_write(&snap->lock);
1970 
1971 			if (!snap->valid) {
1972 				free_pending_exception(pe);
1973 				goto next_snapshot;
1974 			}
1975 
1976 			e = dm_lookup_exception(&snap->complete, chunk);
1977 			if (e) {
1978 				free_pending_exception(pe);
1979 				goto next_snapshot;
1980 			}
1981 
1982 			pe = __find_pending_exception(snap, pe, chunk);
1983 			if (!pe) {
1984 				__invalidate_snapshot(snap, -ENOMEM);
1985 				goto next_snapshot;
1986 			}
1987 		}
1988 
1989 		r = DM_MAPIO_SUBMITTED;
1990 
1991 		/*
1992 		 * If an origin bio was supplied, queue it to wait for the
1993 		 * completion of this exception, and start this one last,
1994 		 * at the end of the function.
1995 		 */
1996 		if (bio) {
1997 			bio_list_add(&pe->origin_bios, bio);
1998 			bio = NULL;
1999 
2000 			if (!pe->started) {
2001 				pe->started = 1;
2002 				pe_to_start_last = pe;
2003 			}
2004 		}
2005 
2006 		if (!pe->started) {
2007 			pe->started = 1;
2008 			pe_to_start_now = pe;
2009 		}
2010 
2011 next_snapshot:
2012 		up_write(&snap->lock);
2013 
2014 		if (pe_to_start_now) {
2015 			start_copy(pe_to_start_now);
2016 			pe_to_start_now = NULL;
2017 		}
2018 	}
2019 
2020 	/*
2021 	 * Submit the exception against which the bio is queued last,
2022 	 * to give the other exceptions a head start.
2023 	 */
2024 	if (pe_to_start_last)
2025 		start_copy(pe_to_start_last);
2026 
2027 	return r;
2028 }
2029 
2030 /*
2031  * Called on a write from the origin driver.
2032  */
2033 static int do_origin(struct dm_dev *origin, struct bio *bio)
2034 {
2035 	struct origin *o;
2036 	int r = DM_MAPIO_REMAPPED;
2037 
2038 	down_read(&_origins_lock);
2039 	o = __lookup_origin(origin->bdev);
2040 	if (o)
2041 		r = __origin_write(&o->snapshots, bio->bi_sector, bio);
2042 	up_read(&_origins_lock);
2043 
2044 	return r;
2045 }
2046 
2047 /*
2048  * Trigger exceptions in all non-merging snapshots.
2049  *
2050  * The chunk size of the merging snapshot may be larger than the chunk
2051  * size of some other snapshot so we may need to reallocate multiple
2052  * chunks in other snapshots.
2053  *
2054  * We scan all the overlapping exceptions in the other snapshots.
2055  * Returns 1 if anything was reallocated and must be waited for,
2056  * otherwise returns 0.
2057  *
2058  * size must be a multiple of merging_snap's chunk_size.
2059  */
2060 static int origin_write_extent(struct dm_snapshot *merging_snap,
2061 			       sector_t sector, unsigned size)
2062 {
2063 	int must_wait = 0;
2064 	sector_t n;
2065 	struct origin *o;
2066 
2067 	/*
2068 	 * The origin's __minimum_chunk_size() got stored in max_io_len
2069 	 * by snapshot_merge_resume().
2070 	 */
2071 	down_read(&_origins_lock);
2072 	o = __lookup_origin(merging_snap->origin->bdev);
2073 	for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2074 		if (__origin_write(&o->snapshots, sector + n, NULL) ==
2075 		    DM_MAPIO_SUBMITTED)
2076 			must_wait = 1;
2077 	up_read(&_origins_lock);
2078 
2079 	return must_wait;
2080 }
2081 
2082 /*
2083  * Origin: maps a linear range of a device, with hooks for snapshotting.
2084  */
2085 
2086 /*
2087  * Construct an origin mapping: <dev_path>
2088  * The context for an origin is merely a 'struct dm_dev *'
2089  * pointing to the real device.
2090  */
2091 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2092 {
2093 	int r;
2094 	struct dm_dev *dev;
2095 
2096 	if (argc != 1) {
2097 		ti->error = "origin: incorrect number of arguments";
2098 		return -EINVAL;
2099 	}
2100 
2101 	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev);
2102 	if (r) {
2103 		ti->error = "Cannot get target device";
2104 		return r;
2105 	}
2106 
2107 	ti->private = dev;
2108 	ti->num_flush_requests = 1;
2109 
2110 	return 0;
2111 }
2112 
2113 static void origin_dtr(struct dm_target *ti)
2114 {
2115 	struct dm_dev *dev = ti->private;
2116 	dm_put_device(ti, dev);
2117 }
2118 
2119 static int origin_map(struct dm_target *ti, struct bio *bio)
2120 {
2121 	struct dm_dev *dev = ti->private;
2122 	bio->bi_bdev = dev->bdev;
2123 
2124 	if (bio->bi_rw & REQ_FLUSH)
2125 		return DM_MAPIO_REMAPPED;
2126 
2127 	/* Only tell snapshots if this is a write */
2128 	return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
2129 }
2130 
2131 /*
2132  * Set the target "max_io_len" field to the minimum of all the snapshots'
2133  * chunk sizes.
2134  */
2135 static void origin_resume(struct dm_target *ti)
2136 {
2137 	struct dm_dev *dev = ti->private;
2138 
2139 	ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
2140 }
2141 
2142 static int origin_status(struct dm_target *ti, status_type_t type,
2143 			 unsigned status_flags, char *result, unsigned maxlen)
2144 {
2145 	struct dm_dev *dev = ti->private;
2146 
2147 	switch (type) {
2148 	case STATUSTYPE_INFO:
2149 		result[0] = '\0';
2150 		break;
2151 
2152 	case STATUSTYPE_TABLE:
2153 		snprintf(result, maxlen, "%s", dev->name);
2154 		break;
2155 	}
2156 
2157 	return 0;
2158 }
2159 
2160 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
2161 			struct bio_vec *biovec, int max_size)
2162 {
2163 	struct dm_dev *dev = ti->private;
2164 	struct request_queue *q = bdev_get_queue(dev->bdev);
2165 
2166 	if (!q->merge_bvec_fn)
2167 		return max_size;
2168 
2169 	bvm->bi_bdev = dev->bdev;
2170 
2171 	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2172 }
2173 
2174 static int origin_iterate_devices(struct dm_target *ti,
2175 				  iterate_devices_callout_fn fn, void *data)
2176 {
2177 	struct dm_dev *dev = ti->private;
2178 
2179 	return fn(ti, dev, 0, ti->len, data);
2180 }
2181 
2182 static struct target_type origin_target = {
2183 	.name    = "snapshot-origin",
2184 	.version = {1, 8, 0},
2185 	.module  = THIS_MODULE,
2186 	.ctr     = origin_ctr,
2187 	.dtr     = origin_dtr,
2188 	.map     = origin_map,
2189 	.resume  = origin_resume,
2190 	.status  = origin_status,
2191 	.merge	 = origin_merge,
2192 	.iterate_devices = origin_iterate_devices,
2193 };
2194 
2195 static struct target_type snapshot_target = {
2196 	.name    = "snapshot",
2197 	.version = {1, 11, 0},
2198 	.module  = THIS_MODULE,
2199 	.ctr     = snapshot_ctr,
2200 	.dtr     = snapshot_dtr,
2201 	.map     = snapshot_map,
2202 	.end_io  = snapshot_end_io,
2203 	.preresume  = snapshot_preresume,
2204 	.resume  = snapshot_resume,
2205 	.status  = snapshot_status,
2206 	.iterate_devices = snapshot_iterate_devices,
2207 };
2208 
2209 static struct target_type merge_target = {
2210 	.name    = dm_snapshot_merge_target_name,
2211 	.version = {1, 2, 0},
2212 	.module  = THIS_MODULE,
2213 	.ctr     = snapshot_ctr,
2214 	.dtr     = snapshot_dtr,
2215 	.map     = snapshot_merge_map,
2216 	.end_io  = snapshot_end_io,
2217 	.presuspend = snapshot_merge_presuspend,
2218 	.preresume  = snapshot_preresume,
2219 	.resume  = snapshot_merge_resume,
2220 	.status  = snapshot_status,
2221 	.iterate_devices = snapshot_iterate_devices,
2222 };
2223 
2224 static int __init dm_snapshot_init(void)
2225 {
2226 	int r;
2227 
2228 	r = dm_exception_store_init();
2229 	if (r) {
2230 		DMERR("Failed to initialize exception stores");
2231 		return r;
2232 	}
2233 
2234 	r = dm_register_target(&snapshot_target);
2235 	if (r < 0) {
2236 		DMERR("snapshot target register failed %d", r);
2237 		goto bad_register_snapshot_target;
2238 	}
2239 
2240 	r = dm_register_target(&origin_target);
2241 	if (r < 0) {
2242 		DMERR("Origin target register failed %d", r);
2243 		goto bad_register_origin_target;
2244 	}
2245 
2246 	r = dm_register_target(&merge_target);
2247 	if (r < 0) {
2248 		DMERR("Merge target register failed %d", r);
2249 		goto bad_register_merge_target;
2250 	}
2251 
2252 	r = init_origin_hash();
2253 	if (r) {
2254 		DMERR("init_origin_hash failed.");
2255 		goto bad_origin_hash;
2256 	}
2257 
2258 	exception_cache = KMEM_CACHE(dm_exception, 0);
2259 	if (!exception_cache) {
2260 		DMERR("Couldn't create exception cache.");
2261 		r = -ENOMEM;
2262 		goto bad_exception_cache;
2263 	}
2264 
2265 	pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2266 	if (!pending_cache) {
2267 		DMERR("Couldn't create pending cache.");
2268 		r = -ENOMEM;
2269 		goto bad_pending_cache;
2270 	}
2271 
2272 	return 0;
2273 
2274 bad_pending_cache:
2275 	kmem_cache_destroy(exception_cache);
2276 bad_exception_cache:
2277 	exit_origin_hash();
2278 bad_origin_hash:
2279 	dm_unregister_target(&merge_target);
2280 bad_register_merge_target:
2281 	dm_unregister_target(&origin_target);
2282 bad_register_origin_target:
2283 	dm_unregister_target(&snapshot_target);
2284 bad_register_snapshot_target:
2285 	dm_exception_store_exit();
2286 
2287 	return r;
2288 }
2289 
2290 static void __exit dm_snapshot_exit(void)
2291 {
2292 	dm_unregister_target(&snapshot_target);
2293 	dm_unregister_target(&origin_target);
2294 	dm_unregister_target(&merge_target);
2295 
2296 	exit_origin_hash();
2297 	kmem_cache_destroy(pending_cache);
2298 	kmem_cache_destroy(exception_cache);
2299 
2300 	dm_exception_store_exit();
2301 }
2302 
2303 /* Module hooks */
2304 module_init(dm_snapshot_init);
2305 module_exit(dm_snapshot_exit);
2306 
2307 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2308 MODULE_AUTHOR("Joe Thornber");
2309 MODULE_LICENSE("GPL");
2310