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#include <linux/semaphore.h>
23
24#include "dm.h"
25
26#include "dm-exception-store.h"
27
28#define DM_MSG_PREFIX "snapshots"
29
30static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
31
32#define dm_target_is_snapshot_merge(ti) \
33 ((ti)->type->name == dm_snapshot_merge_target_name)
34
35/*
36 * The size of the mempool used to track chunks in use.
37 */
38#define MIN_IOS 256
39
40#define DM_TRACKED_CHUNK_HASH_SIZE 16
41#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
42 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
43
44struct dm_exception_table {
45 uint32_t hash_mask;
46 unsigned hash_shift;
47 struct list_head *table;
48};
49
50struct dm_snapshot {
51 struct mutex lock;
52
53 struct dm_dev *origin;
54 struct dm_dev *cow;
55
56 struct dm_target *ti;
57
58 /* List of snapshots per Origin */
59 struct list_head list;
60
61 /*
62 * You can't use a snapshot if this is 0 (e.g. if full).
63 * A snapshot-merge target never clears this.
64 */
65 int valid;
66
67 /*
68 * The snapshot overflowed because of a write to the snapshot device.
69 * We don't have to invalidate the snapshot in this case, but we need
70 * to prevent further writes.
71 */
72 int snapshot_overflowed;
73
74 /* Origin writes don't trigger exceptions until this is set */
75 int active;
76
77 atomic_t pending_exceptions_count;
78
79 /* Protected by "lock" */
80 sector_t exception_start_sequence;
81
82 /* Protected by kcopyd single-threaded callback */
83 sector_t exception_complete_sequence;
84
85 /*
86 * A list of pending exceptions that completed out of order.
87 * Protected by kcopyd single-threaded callback.
88 */
89 struct rb_root out_of_order_tree;
90
91 mempool_t pending_pool;
92
93 struct dm_exception_table pending;
94 struct dm_exception_table complete;
95
96 /*
97 * pe_lock protects all pending_exception operations and access
98 * as well as the snapshot_bios list.
99 */
100 spinlock_t pe_lock;
101
102 /* Chunks with outstanding reads */
103 spinlock_t tracked_chunk_lock;
104 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
105
106 /* The on disk metadata handler */
107 struct dm_exception_store *store;
108
109 /* Maximum number of in-flight COW jobs. */
110 struct semaphore cow_count;
111
112 struct dm_kcopyd_client *kcopyd_client;
113
114 /* Wait for events based on state_bits */
115 unsigned long state_bits;
116
117 /* Range of chunks currently being merged. */
118 chunk_t first_merging_chunk;
119 int num_merging_chunks;
120
121 /*
122 * The merge operation failed if this flag is set.
123 * Failure modes are handled as follows:
124 * - I/O error reading the header
125 * => don't load the target; abort.
126 * - Header does not have "valid" flag set
127 * => use the origin; forget about the snapshot.
128 * - I/O error when reading exceptions
129 * => don't load the target; abort.
130 * (We can't use the intermediate origin state.)
131 * - I/O error while merging
132 * => stop merging; set merge_failed; process I/O normally.
133 */
134 int merge_failed;
135
136 /*
137 * Incoming bios that overlap with chunks being merged must wait
138 * for them to be committed.
139 */
140 struct bio_list bios_queued_during_merge;
141};
142
143/*
144 * state_bits:
145 * RUNNING_MERGE - Merge operation is in progress.
146 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
147 * cleared afterwards.
148 */
149#define RUNNING_MERGE 0
150#define SHUTDOWN_MERGE 1
151
152/*
153 * Maximum number of chunks being copied on write.
154 *
155 * The value was decided experimentally as a trade-off between memory
156 * consumption, stalling the kernel's workqueues and maintaining a high enough
157 * throughput.
158 */
159#define DEFAULT_COW_THRESHOLD 2048
160
161static int cow_threshold = DEFAULT_COW_THRESHOLD;
162module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644);
163MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
164
165DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
166 "A percentage of time allocated for copy on write");
167
168struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
169{
170 return s->origin;
171}
172EXPORT_SYMBOL(dm_snap_origin);
173
174struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
175{
176 return s->cow;
177}
178EXPORT_SYMBOL(dm_snap_cow);
179
180static sector_t chunk_to_sector(struct dm_exception_store *store,
181 chunk_t chunk)
182{
183 return chunk << store->chunk_shift;
184}
185
186static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
187{
188 /*
189 * There is only ever one instance of a particular block
190 * device so we can compare pointers safely.
191 */
192 return lhs == rhs;
193}
194
195struct dm_snap_pending_exception {
196 struct dm_exception e;
197
198 /*
199 * Origin buffers waiting for this to complete are held
200 * in a bio list
201 */
202 struct bio_list origin_bios;
203 struct bio_list snapshot_bios;
204
205 /* Pointer back to snapshot context */
206 struct dm_snapshot *snap;
207
208 /*
209 * 1 indicates the exception has already been sent to
210 * kcopyd.
211 */
212 int started;
213
214 /* There was copying error. */
215 int copy_error;
216
217 /* A sequence number, it is used for in-order completion. */
218 sector_t exception_sequence;
219
220 struct rb_node out_of_order_node;
221
222 /*
223 * For writing a complete chunk, bypassing the copy.
224 */
225 struct bio *full_bio;
226 bio_end_io_t *full_bio_end_io;
227};
228
229/*
230 * Hash table mapping origin volumes to lists of snapshots and
231 * a lock to protect it
232 */
233static struct kmem_cache *exception_cache;
234static struct kmem_cache *pending_cache;
235
236struct dm_snap_tracked_chunk {
237 struct hlist_node node;
238 chunk_t chunk;
239};
240
241static void init_tracked_chunk(struct bio *bio)
242{
243 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
244 INIT_HLIST_NODE(&c->node);
245}
246
247static bool is_bio_tracked(struct bio *bio)
248{
249 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
250 return !hlist_unhashed(&c->node);
251}
252
253static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
254{
255 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
256
257 c->chunk = chunk;
258
259 spin_lock_irq(&s->tracked_chunk_lock);
260 hlist_add_head(&c->node,
261 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
262 spin_unlock_irq(&s->tracked_chunk_lock);
263}
264
265static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
266{
267 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
268 unsigned long flags;
269
270 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
271 hlist_del(&c->node);
272 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
273}
274
275static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
276{
277 struct dm_snap_tracked_chunk *c;
278 int found = 0;
279
280 spin_lock_irq(&s->tracked_chunk_lock);
281
282 hlist_for_each_entry(c,
283 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
284 if (c->chunk == chunk) {
285 found = 1;
286 break;
287 }
288 }
289
290 spin_unlock_irq(&s->tracked_chunk_lock);
291
292 return found;
293}
294
295/*
296 * This conflicting I/O is extremely improbable in the caller,
297 * so msleep(1) is sufficient and there is no need for a wait queue.
298 */
299static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
300{
301 while (__chunk_is_tracked(s, chunk))
302 msleep(1);
303}
304
305/*
306 * One of these per registered origin, held in the snapshot_origins hash
307 */
308struct origin {
309 /* The origin device */
310 struct block_device *bdev;
311
312 struct list_head hash_list;
313
314 /* List of snapshots for this origin */
315 struct list_head snapshots;
316};
317
318/*
319 * This structure is allocated for each origin target
320 */
321struct dm_origin {
322 struct dm_dev *dev;
323 struct dm_target *ti;
324 unsigned split_boundary;
325 struct list_head hash_list;
326};
327
328/*
329 * Size of the hash table for origin volumes. If we make this
330 * the size of the minors list then it should be nearly perfect
331 */
332#define ORIGIN_HASH_SIZE 256
333#define ORIGIN_MASK 0xFF
334static struct list_head *_origins;
335static struct list_head *_dm_origins;
336static struct rw_semaphore _origins_lock;
337
338static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
339static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
340static uint64_t _pending_exceptions_done_count;
341
342static int init_origin_hash(void)
343{
344 int i;
345
346 _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),
347 GFP_KERNEL);
348 if (!_origins) {
349 DMERR("unable to allocate memory for _origins");
350 return -ENOMEM;
351 }
352 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
353 INIT_LIST_HEAD(_origins + i);
354
355 _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,
356 sizeof(struct list_head),
357 GFP_KERNEL);
358 if (!_dm_origins) {
359 DMERR("unable to allocate memory for _dm_origins");
360 kfree(_origins);
361 return -ENOMEM;
362 }
363 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
364 INIT_LIST_HEAD(_dm_origins + i);
365
366 init_rwsem(&_origins_lock);
367
368 return 0;
369}
370
371static void exit_origin_hash(void)
372{
373 kfree(_origins);
374 kfree(_dm_origins);
375}
376
377static unsigned origin_hash(struct block_device *bdev)
378{
379 return bdev->bd_dev & ORIGIN_MASK;
380}
381
382static struct origin *__lookup_origin(struct block_device *origin)
383{
384 struct list_head *ol;
385 struct origin *o;
386
387 ol = &_origins[origin_hash(origin)];
388 list_for_each_entry (o, ol, hash_list)
389 if (bdev_equal(o->bdev, origin))
390 return o;
391
392 return NULL;
393}
394
395static void __insert_origin(struct origin *o)
396{
397 struct list_head *sl = &_origins[origin_hash(o->bdev)];
398 list_add_tail(&o->hash_list, sl);
399}
400
401static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
402{
403 struct list_head *ol;
404 struct dm_origin *o;
405
406 ol = &_dm_origins[origin_hash(origin)];
407 list_for_each_entry (o, ol, hash_list)
408 if (bdev_equal(o->dev->bdev, origin))
409 return o;
410
411 return NULL;
412}
413
414static void __insert_dm_origin(struct dm_origin *o)
415{
416 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
417 list_add_tail(&o->hash_list, sl);
418}
419
420static void __remove_dm_origin(struct dm_origin *o)
421{
422 list_del(&o->hash_list);
423}
424
425/*
426 * _origins_lock must be held when calling this function.
427 * Returns number of snapshots registered using the supplied cow device, plus:
428 * snap_src - a snapshot suitable for use as a source of exception handover
429 * snap_dest - a snapshot capable of receiving exception handover.
430 * snap_merge - an existing snapshot-merge target linked to the same origin.
431 * There can be at most one snapshot-merge target. The parameter is optional.
432 *
433 * Possible return values and states of snap_src and snap_dest.
434 * 0: NULL, NULL - first new snapshot
435 * 1: snap_src, NULL - normal snapshot
436 * 2: snap_src, snap_dest - waiting for handover
437 * 2: snap_src, NULL - handed over, waiting for old to be deleted
438 * 1: NULL, snap_dest - source got destroyed without handover
439 */
440static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
441 struct dm_snapshot **snap_src,
442 struct dm_snapshot **snap_dest,
443 struct dm_snapshot **snap_merge)
444{
445 struct dm_snapshot *s;
446 struct origin *o;
447 int count = 0;
448 int active;
449
450 o = __lookup_origin(snap->origin->bdev);
451 if (!o)
452 goto out;
453
454 list_for_each_entry(s, &o->snapshots, list) {
455 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
456 *snap_merge = s;
457 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
458 continue;
459
460 mutex_lock(&s->lock);
461 active = s->active;
462 mutex_unlock(&s->lock);
463
464 if (active) {
465 if (snap_src)
466 *snap_src = s;
467 } else if (snap_dest)
468 *snap_dest = s;
469
470 count++;
471 }
472
473out:
474 return count;
475}
476
477/*
478 * On success, returns 1 if this snapshot is a handover destination,
479 * otherwise returns 0.
480 */
481static int __validate_exception_handover(struct dm_snapshot *snap)
482{
483 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
484 struct dm_snapshot *snap_merge = NULL;
485
486 /* Does snapshot need exceptions handed over to it? */
487 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
488 &snap_merge) == 2) ||
489 snap_dest) {
490 snap->ti->error = "Snapshot cow pairing for exception "
491 "table handover failed";
492 return -EINVAL;
493 }
494
495 /*
496 * If no snap_src was found, snap cannot become a handover
497 * destination.
498 */
499 if (!snap_src)
500 return 0;
501
502 /*
503 * Non-snapshot-merge handover?
504 */
505 if (!dm_target_is_snapshot_merge(snap->ti))
506 return 1;
507
508 /*
509 * Do not allow more than one merging snapshot.
510 */
511 if (snap_merge) {
512 snap->ti->error = "A snapshot is already merging.";
513 return -EINVAL;
514 }
515
516 if (!snap_src->store->type->prepare_merge ||
517 !snap_src->store->type->commit_merge) {
518 snap->ti->error = "Snapshot exception store does not "
519 "support snapshot-merge.";
520 return -EINVAL;
521 }
522
523 return 1;
524}
525
526static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
527{
528 struct dm_snapshot *l;
529
530 /* Sort the list according to chunk size, largest-first smallest-last */
531 list_for_each_entry(l, &o->snapshots, list)
532 if (l->store->chunk_size < s->store->chunk_size)
533 break;
534 list_add_tail(&s->list, &l->list);
535}
536
537/*
538 * Make a note of the snapshot and its origin so we can look it
539 * up when the origin has a write on it.
540 *
541 * Also validate snapshot exception store handovers.
542 * On success, returns 1 if this registration is a handover destination,
543 * otherwise returns 0.
544 */
545static int register_snapshot(struct dm_snapshot *snap)
546{
547 struct origin *o, *new_o = NULL;
548 struct block_device *bdev = snap->origin->bdev;
549 int r = 0;
550
551 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
552 if (!new_o)
553 return -ENOMEM;
554
555 down_write(&_origins_lock);
556
557 r = __validate_exception_handover(snap);
558 if (r < 0) {
559 kfree(new_o);
560 goto out;
561 }
562
563 o = __lookup_origin(bdev);
564 if (o)
565 kfree(new_o);
566 else {
567 /* New origin */
568 o = new_o;
569
570 /* Initialise the struct */
571 INIT_LIST_HEAD(&o->snapshots);
572 o->bdev = bdev;
573
574 __insert_origin(o);
575 }
576
577 __insert_snapshot(o, snap);
578
579out:
580 up_write(&_origins_lock);
581
582 return r;
583}
584
585/*
586 * Move snapshot to correct place in list according to chunk size.
587 */
588static void reregister_snapshot(struct dm_snapshot *s)
589{
590 struct block_device *bdev = s->origin->bdev;
591
592 down_write(&_origins_lock);
593
594 list_del(&s->list);
595 __insert_snapshot(__lookup_origin(bdev), s);
596
597 up_write(&_origins_lock);
598}
599
600static void unregister_snapshot(struct dm_snapshot *s)
601{
602 struct origin *o;
603
604 down_write(&_origins_lock);
605 o = __lookup_origin(s->origin->bdev);
606
607 list_del(&s->list);
608 if (o && list_empty(&o->snapshots)) {
609 list_del(&o->hash_list);
610 kfree(o);
611 }
612
613 up_write(&_origins_lock);
614}
615
616/*
617 * Implementation of the exception hash tables.
618 * The lowest hash_shift bits of the chunk number are ignored, allowing
619 * some consecutive chunks to be grouped together.
620 */
621static int dm_exception_table_init(struct dm_exception_table *et,
622 uint32_t size, unsigned hash_shift)
623{
624 unsigned int i;
625
626 et->hash_shift = hash_shift;
627 et->hash_mask = size - 1;
628 et->table = dm_vcalloc(size, sizeof(struct list_head));
629 if (!et->table)
630 return -ENOMEM;
631
632 for (i = 0; i < size; i++)
633 INIT_LIST_HEAD(et->table + i);
634
635 return 0;
636}
637
638static void dm_exception_table_exit(struct dm_exception_table *et,
639 struct kmem_cache *mem)
640{
641 struct list_head *slot;
642 struct dm_exception *ex, *next;
643 int i, size;
644
645 size = et->hash_mask + 1;
646 for (i = 0; i < size; i++) {
647 slot = et->table + i;
648
649 list_for_each_entry_safe (ex, next, slot, hash_list)
650 kmem_cache_free(mem, ex);
651 }
652
653 vfree(et->table);
654}
655
656static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
657{
658 return (chunk >> et->hash_shift) & et->hash_mask;
659}
660
661static void dm_remove_exception(struct dm_exception *e)
662{
663 list_del(&e->hash_list);
664}
665
666/*
667 * Return the exception data for a sector, or NULL if not
668 * remapped.
669 */
670static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
671 chunk_t chunk)
672{
673 struct list_head *slot;
674 struct dm_exception *e;
675
676 slot = &et->table[exception_hash(et, chunk)];
677 list_for_each_entry (e, slot, hash_list)
678 if (chunk >= e->old_chunk &&
679 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
680 return e;
681
682 return NULL;
683}
684
685static struct dm_exception *alloc_completed_exception(gfp_t gfp)
686{
687 struct dm_exception *e;
688
689 e = kmem_cache_alloc(exception_cache, gfp);
690 if (!e && gfp == GFP_NOIO)
691 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
692
693 return e;
694}
695
696static void free_completed_exception(struct dm_exception *e)
697{
698 kmem_cache_free(exception_cache, e);
699}
700
701static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
702{
703 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
704 GFP_NOIO);
705
706 atomic_inc(&s->pending_exceptions_count);
707 pe->snap = s;
708
709 return pe;
710}
711
712static void free_pending_exception(struct dm_snap_pending_exception *pe)
713{
714 struct dm_snapshot *s = pe->snap;
715
716 mempool_free(pe, &s->pending_pool);
717 smp_mb__before_atomic();
718 atomic_dec(&s->pending_exceptions_count);
719}
720
721static void dm_insert_exception(struct dm_exception_table *eh,
722 struct dm_exception *new_e)
723{
724 struct list_head *l;
725 struct dm_exception *e = NULL;
726
727 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
728
729 /* Add immediately if this table doesn't support consecutive chunks */
730 if (!eh->hash_shift)
731 goto out;
732
733 /* List is ordered by old_chunk */
734 list_for_each_entry_reverse(e, l, hash_list) {
735 /* Insert after an existing chunk? */
736 if (new_e->old_chunk == (e->old_chunk +
737 dm_consecutive_chunk_count(e) + 1) &&
738 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
739 dm_consecutive_chunk_count(e) + 1)) {
740 dm_consecutive_chunk_count_inc(e);
741 free_completed_exception(new_e);
742 return;
743 }
744
745 /* Insert before an existing chunk? */
746 if (new_e->old_chunk == (e->old_chunk - 1) &&
747 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
748 dm_consecutive_chunk_count_inc(e);
749 e->old_chunk--;
750 e->new_chunk--;
751 free_completed_exception(new_e);
752 return;
753 }
754
755 if (new_e->old_chunk > e->old_chunk)
756 break;
757 }
758
759out:
760 list_add(&new_e->hash_list, e ? &e->hash_list : l);
761}
762
763/*
764 * Callback used by the exception stores to load exceptions when
765 * initialising.
766 */
767static int dm_add_exception(void *context, chunk_t old, chunk_t new)
768{
769 struct dm_snapshot *s = context;
770 struct dm_exception *e;
771
772 e = alloc_completed_exception(GFP_KERNEL);
773 if (!e)
774 return -ENOMEM;
775
776 e->old_chunk = old;
777
778 /* Consecutive_count is implicitly initialised to zero */
779 e->new_chunk = new;
780
781 dm_insert_exception(&s->complete, e);
782
783 return 0;
784}
785
786/*
787 * Return a minimum chunk size of all snapshots that have the specified origin.
788 * Return zero if the origin has no snapshots.
789 */
790static uint32_t __minimum_chunk_size(struct origin *o)
791{
792 struct dm_snapshot *snap;
793 unsigned chunk_size = 0;
794
795 if (o)
796 list_for_each_entry(snap, &o->snapshots, list)
797 chunk_size = min_not_zero(chunk_size,
798 snap->store->chunk_size);
799
800 return (uint32_t) chunk_size;
801}
802
803/*
804 * Hard coded magic.
805 */
806static int calc_max_buckets(void)
807{
808 /* use a fixed size of 2MB */
809 unsigned long mem = 2 * 1024 * 1024;
810 mem /= sizeof(struct list_head);
811
812 return mem;
813}
814
815/*
816 * Allocate room for a suitable hash table.
817 */
818static int init_hash_tables(struct dm_snapshot *s)
819{
820 sector_t hash_size, cow_dev_size, max_buckets;
821
822 /*
823 * Calculate based on the size of the original volume or
824 * the COW volume...
825 */
826 cow_dev_size = get_dev_size(s->cow->bdev);
827 max_buckets = calc_max_buckets();
828
829 hash_size = cow_dev_size >> s->store->chunk_shift;
830 hash_size = min(hash_size, max_buckets);
831
832 if (hash_size < 64)
833 hash_size = 64;
834 hash_size = rounddown_pow_of_two(hash_size);
835 if (dm_exception_table_init(&s->complete, hash_size,
836 DM_CHUNK_CONSECUTIVE_BITS))
837 return -ENOMEM;
838
839 /*
840 * Allocate hash table for in-flight exceptions
841 * Make this smaller than the real hash table
842 */
843 hash_size >>= 3;
844 if (hash_size < 64)
845 hash_size = 64;
846
847 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
848 dm_exception_table_exit(&s->complete, exception_cache);
849 return -ENOMEM;
850 }
851
852 return 0;
853}
854
855static void merge_shutdown(struct dm_snapshot *s)
856{
857 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
858 smp_mb__after_atomic();
859 wake_up_bit(&s->state_bits, RUNNING_MERGE);
860}
861
862static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
863{
864 s->first_merging_chunk = 0;
865 s->num_merging_chunks = 0;
866
867 return bio_list_get(&s->bios_queued_during_merge);
868}
869
870/*
871 * Remove one chunk from the index of completed exceptions.
872 */
873static int __remove_single_exception_chunk(struct dm_snapshot *s,
874 chunk_t old_chunk)
875{
876 struct dm_exception *e;
877
878 e = dm_lookup_exception(&s->complete, old_chunk);
879 if (!e) {
880 DMERR("Corruption detected: exception for block %llu is "
881 "on disk but not in memory",
882 (unsigned long long)old_chunk);
883 return -EINVAL;
884 }
885
886 /*
887 * If this is the only chunk using this exception, remove exception.
888 */
889 if (!dm_consecutive_chunk_count(e)) {
890 dm_remove_exception(e);
891 free_completed_exception(e);
892 return 0;
893 }
894
895 /*
896 * The chunk may be either at the beginning or the end of a
897 * group of consecutive chunks - never in the middle. We are
898 * removing chunks in the opposite order to that in which they
899 * were added, so this should always be true.
900 * Decrement the consecutive chunk counter and adjust the
901 * starting point if necessary.
902 */
903 if (old_chunk == e->old_chunk) {
904 e->old_chunk++;
905 e->new_chunk++;
906 } else if (old_chunk != e->old_chunk +
907 dm_consecutive_chunk_count(e)) {
908 DMERR("Attempt to merge block %llu from the "
909 "middle of a chunk range [%llu - %llu]",
910 (unsigned long long)old_chunk,
911 (unsigned long long)e->old_chunk,
912 (unsigned long long)
913 e->old_chunk + dm_consecutive_chunk_count(e));
914 return -EINVAL;
915 }
916
917 dm_consecutive_chunk_count_dec(e);
918
919 return 0;
920}
921
922static void flush_bios(struct bio *bio);
923
924static int remove_single_exception_chunk(struct dm_snapshot *s)
925{
926 struct bio *b = NULL;
927 int r;
928 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
929
930 mutex_lock(&s->lock);
931
932 /*
933 * Process chunks (and associated exceptions) in reverse order
934 * so that dm_consecutive_chunk_count_dec() accounting works.
935 */
936 do {
937 r = __remove_single_exception_chunk(s, old_chunk);
938 if (r)
939 goto out;
940 } while (old_chunk-- > s->first_merging_chunk);
941
942 b = __release_queued_bios_after_merge(s);
943
944out:
945 mutex_unlock(&s->lock);
946 if (b)
947 flush_bios(b);
948
949 return r;
950}
951
952static int origin_write_extent(struct dm_snapshot *merging_snap,
953 sector_t sector, unsigned chunk_size);
954
955static void merge_callback(int read_err, unsigned long write_err,
956 void *context);
957
958static uint64_t read_pending_exceptions_done_count(void)
959{
960 uint64_t pending_exceptions_done;
961
962 spin_lock(&_pending_exceptions_done_spinlock);
963 pending_exceptions_done = _pending_exceptions_done_count;
964 spin_unlock(&_pending_exceptions_done_spinlock);
965
966 return pending_exceptions_done;
967}
968
969static void increment_pending_exceptions_done_count(void)
970{
971 spin_lock(&_pending_exceptions_done_spinlock);
972 _pending_exceptions_done_count++;
973 spin_unlock(&_pending_exceptions_done_spinlock);
974
975 wake_up_all(&_pending_exceptions_done);
976}
977
978static void snapshot_merge_next_chunks(struct dm_snapshot *s)
979{
980 int i, linear_chunks;
981 chunk_t old_chunk, new_chunk;
982 struct dm_io_region src, dest;
983 sector_t io_size;
984 uint64_t previous_count;
985
986 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
987 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
988 goto shut;
989
990 /*
991 * valid flag never changes during merge, so no lock required.
992 */
993 if (!s->valid) {
994 DMERR("Snapshot is invalid: can't merge");
995 goto shut;
996 }
997
998 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
999 &new_chunk);
1000 if (linear_chunks <= 0) {
1001 if (linear_chunks < 0) {
1002 DMERR("Read error in exception store: "
1003 "shutting down merge");
1004 mutex_lock(&s->lock);
1005 s->merge_failed = 1;
1006 mutex_unlock(&s->lock);
1007 }
1008 goto shut;
1009 }
1010
1011 /* Adjust old_chunk and new_chunk to reflect start of linear region */
1012 old_chunk = old_chunk + 1 - linear_chunks;
1013 new_chunk = new_chunk + 1 - linear_chunks;
1014
1015 /*
1016 * Use one (potentially large) I/O to copy all 'linear_chunks'
1017 * from the exception store to the origin
1018 */
1019 io_size = linear_chunks * s->store->chunk_size;
1020
1021 dest.bdev = s->origin->bdev;
1022 dest.sector = chunk_to_sector(s->store, old_chunk);
1023 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1024
1025 src.bdev = s->cow->bdev;
1026 src.sector = chunk_to_sector(s->store, new_chunk);
1027 src.count = dest.count;
1028
1029 /*
1030 * Reallocate any exceptions needed in other snapshots then
1031 * wait for the pending exceptions to complete.
1032 * Each time any pending exception (globally on the system)
1033 * completes we are woken and repeat the process to find out
1034 * if we can proceed. While this may not seem a particularly
1035 * efficient algorithm, it is not expected to have any
1036 * significant impact on performance.
1037 */
1038 previous_count = read_pending_exceptions_done_count();
1039 while (origin_write_extent(s, dest.sector, io_size)) {
1040 wait_event(_pending_exceptions_done,
1041 (read_pending_exceptions_done_count() !=
1042 previous_count));
1043 /* Retry after the wait, until all exceptions are done. */
1044 previous_count = read_pending_exceptions_done_count();
1045 }
1046
1047 mutex_lock(&s->lock);
1048 s->first_merging_chunk = old_chunk;
1049 s->num_merging_chunks = linear_chunks;
1050 mutex_unlock(&s->lock);
1051
1052 /* Wait until writes to all 'linear_chunks' drain */
1053 for (i = 0; i < linear_chunks; i++)
1054 __check_for_conflicting_io(s, old_chunk + i);
1055
1056 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1057 return;
1058
1059shut:
1060 merge_shutdown(s);
1061}
1062
1063static void error_bios(struct bio *bio);
1064
1065static void merge_callback(int read_err, unsigned long write_err, void *context)
1066{
1067 struct dm_snapshot *s = context;
1068 struct bio *b = NULL;
1069
1070 if (read_err || write_err) {
1071 if (read_err)
1072 DMERR("Read error: shutting down merge.");
1073 else
1074 DMERR("Write error: shutting down merge.");
1075 goto shut;
1076 }
1077
1078 if (s->store->type->commit_merge(s->store,
1079 s->num_merging_chunks) < 0) {
1080 DMERR("Write error in exception store: shutting down merge");
1081 goto shut;
1082 }
1083
1084 if (remove_single_exception_chunk(s) < 0)
1085 goto shut;
1086
1087 snapshot_merge_next_chunks(s);
1088
1089 return;
1090
1091shut:
1092 mutex_lock(&s->lock);
1093 s->merge_failed = 1;
1094 b = __release_queued_bios_after_merge(s);
1095 mutex_unlock(&s->lock);
1096 error_bios(b);
1097
1098 merge_shutdown(s);
1099}
1100
1101static void start_merge(struct dm_snapshot *s)
1102{
1103 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1104 snapshot_merge_next_chunks(s);
1105}
1106
1107/*
1108 * Stop the merging process and wait until it finishes.
1109 */
1110static void stop_merge(struct dm_snapshot *s)
1111{
1112 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1113 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1114 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1115}
1116
1117/*
1118 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size>
1119 */
1120static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1121{
1122 struct dm_snapshot *s;
1123 int i;
1124 int r = -EINVAL;
1125 char *origin_path, *cow_path;
1126 dev_t origin_dev, cow_dev;
1127 unsigned args_used, num_flush_bios = 1;
1128 fmode_t origin_mode = FMODE_READ;
1129
1130 if (argc != 4) {
1131 ti->error = "requires exactly 4 arguments";
1132 r = -EINVAL;
1133 goto bad;
1134 }
1135
1136 if (dm_target_is_snapshot_merge(ti)) {
1137 num_flush_bios = 2;
1138 origin_mode = FMODE_WRITE;
1139 }
1140
1141 s = kzalloc(sizeof(*s), GFP_KERNEL);
1142 if (!s) {
1143 ti->error = "Cannot allocate private snapshot structure";
1144 r = -ENOMEM;
1145 goto bad;
1146 }
1147
1148 origin_path = argv[0];
1149 argv++;
1150 argc--;
1151
1152 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1153 if (r) {
1154 ti->error = "Cannot get origin device";
1155 goto bad_origin;
1156 }
1157 origin_dev = s->origin->bdev->bd_dev;
1158
1159 cow_path = argv[0];
1160 argv++;
1161 argc--;
1162
1163 cow_dev = dm_get_dev_t(cow_path);
1164 if (cow_dev && cow_dev == origin_dev) {
1165 ti->error = "COW device cannot be the same as origin device";
1166 r = -EINVAL;
1167 goto bad_cow;
1168 }
1169
1170 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1171 if (r) {
1172 ti->error = "Cannot get COW device";
1173 goto bad_cow;
1174 }
1175
1176 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1177 if (r) {
1178 ti->error = "Couldn't create exception store";
1179 r = -EINVAL;
1180 goto bad_store;
1181 }
1182
1183 argv += args_used;
1184 argc -= args_used;
1185
1186 s->ti = ti;
1187 s->valid = 1;
1188 s->snapshot_overflowed = 0;
1189 s->active = 0;
1190 atomic_set(&s->pending_exceptions_count, 0);
1191 s->exception_start_sequence = 0;
1192 s->exception_complete_sequence = 0;
1193 s->out_of_order_tree = RB_ROOT;
1194 mutex_init(&s->lock);
1195 INIT_LIST_HEAD(&s->list);
1196 spin_lock_init(&s->pe_lock);
1197 s->state_bits = 0;
1198 s->merge_failed = 0;
1199 s->first_merging_chunk = 0;
1200 s->num_merging_chunks = 0;
1201 bio_list_init(&s->bios_queued_during_merge);
1202
1203 /* Allocate hash table for COW data */
1204 if (init_hash_tables(s)) {
1205 ti->error = "Unable to allocate hash table space";
1206 r = -ENOMEM;
1207 goto bad_hash_tables;
1208 }
1209
1210 sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX);
1211
1212 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1213 if (IS_ERR(s->kcopyd_client)) {
1214 r = PTR_ERR(s->kcopyd_client);
1215 ti->error = "Could not create kcopyd client";
1216 goto bad_kcopyd;
1217 }
1218
1219 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
1220 if (r) {
1221 ti->error = "Could not allocate mempool for pending exceptions";
1222 goto bad_pending_pool;
1223 }
1224
1225 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1226 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1227
1228 spin_lock_init(&s->tracked_chunk_lock);
1229
1230 ti->private = s;
1231 ti->num_flush_bios = num_flush_bios;
1232 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1233
1234 /* Add snapshot to the list of snapshots for this origin */
1235 /* Exceptions aren't triggered till snapshot_resume() is called */
1236 r = register_snapshot(s);
1237 if (r == -ENOMEM) {
1238 ti->error = "Snapshot origin struct allocation failed";
1239 goto bad_load_and_register;
1240 } else if (r < 0) {
1241 /* invalid handover, register_snapshot has set ti->error */
1242 goto bad_load_and_register;
1243 }
1244
1245 /*
1246 * Metadata must only be loaded into one table at once, so skip this
1247 * if metadata will be handed over during resume.
1248 * Chunk size will be set during the handover - set it to zero to
1249 * ensure it's ignored.
1250 */
1251 if (r > 0) {
1252 s->store->chunk_size = 0;
1253 return 0;
1254 }
1255
1256 r = s->store->type->read_metadata(s->store, dm_add_exception,
1257 (void *)s);
1258 if (r < 0) {
1259 ti->error = "Failed to read snapshot metadata";
1260 goto bad_read_metadata;
1261 } else if (r > 0) {
1262 s->valid = 0;
1263 DMWARN("Snapshot is marked invalid.");
1264 }
1265
1266 if (!s->store->chunk_size) {
1267 ti->error = "Chunk size not set";
1268 goto bad_read_metadata;
1269 }
1270
1271 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1272 if (r)
1273 goto bad_read_metadata;
1274
1275 return 0;
1276
1277bad_read_metadata:
1278 unregister_snapshot(s);
1279
1280bad_load_and_register:
1281 mempool_exit(&s->pending_pool);
1282
1283bad_pending_pool:
1284 dm_kcopyd_client_destroy(s->kcopyd_client);
1285
1286bad_kcopyd:
1287 dm_exception_table_exit(&s->pending, pending_cache);
1288 dm_exception_table_exit(&s->complete, exception_cache);
1289
1290bad_hash_tables:
1291 dm_exception_store_destroy(s->store);
1292
1293bad_store:
1294 dm_put_device(ti, s->cow);
1295
1296bad_cow:
1297 dm_put_device(ti, s->origin);
1298
1299bad_origin:
1300 kfree(s);
1301
1302bad:
1303 return r;
1304}
1305
1306static void __free_exceptions(struct dm_snapshot *s)
1307{
1308 dm_kcopyd_client_destroy(s->kcopyd_client);
1309 s->kcopyd_client = NULL;
1310
1311 dm_exception_table_exit(&s->pending, pending_cache);
1312 dm_exception_table_exit(&s->complete, exception_cache);
1313}
1314
1315static void __handover_exceptions(struct dm_snapshot *snap_src,
1316 struct dm_snapshot *snap_dest)
1317{
1318 union {
1319 struct dm_exception_table table_swap;
1320 struct dm_exception_store *store_swap;
1321 } u;
1322
1323 /*
1324 * Swap all snapshot context information between the two instances.
1325 */
1326 u.table_swap = snap_dest->complete;
1327 snap_dest->complete = snap_src->complete;
1328 snap_src->complete = u.table_swap;
1329
1330 u.store_swap = snap_dest->store;
1331 snap_dest->store = snap_src->store;
1332 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1333 snap_src->store = u.store_swap;
1334
1335 snap_dest->store->snap = snap_dest;
1336 snap_src->store->snap = snap_src;
1337
1338 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1339 snap_dest->valid = snap_src->valid;
1340 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1341
1342 /*
1343 * Set source invalid to ensure it receives no further I/O.
1344 */
1345 snap_src->valid = 0;
1346}
1347
1348static void snapshot_dtr(struct dm_target *ti)
1349{
1350#ifdef CONFIG_DM_DEBUG
1351 int i;
1352#endif
1353 struct dm_snapshot *s = ti->private;
1354 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1355
1356 down_read(&_origins_lock);
1357 /* Check whether exception handover must be cancelled */
1358 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1359 if (snap_src && snap_dest && (s == snap_src)) {
1360 mutex_lock(&snap_dest->lock);
1361 snap_dest->valid = 0;
1362 mutex_unlock(&snap_dest->lock);
1363 DMERR("Cancelling snapshot handover.");
1364 }
1365 up_read(&_origins_lock);
1366
1367 if (dm_target_is_snapshot_merge(ti))
1368 stop_merge(s);
1369
1370 /* Prevent further origin writes from using this snapshot. */
1371 /* After this returns there can be no new kcopyd jobs. */
1372 unregister_snapshot(s);
1373
1374 while (atomic_read(&s->pending_exceptions_count))
1375 msleep(1);
1376 /*
1377 * Ensure instructions in mempool_exit aren't reordered
1378 * before atomic_read.
1379 */
1380 smp_mb();
1381
1382#ifdef CONFIG_DM_DEBUG
1383 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1384 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1385#endif
1386
1387 __free_exceptions(s);
1388
1389 mempool_exit(&s->pending_pool);
1390
1391 dm_exception_store_destroy(s->store);
1392
1393 mutex_destroy(&s->lock);
1394
1395 dm_put_device(ti, s->cow);
1396
1397 dm_put_device(ti, s->origin);
1398
1399 kfree(s);
1400}
1401
1402/*
1403 * Flush a list of buffers.
1404 */
1405static void flush_bios(struct bio *bio)
1406{
1407 struct bio *n;
1408
1409 while (bio) {
1410 n = bio->bi_next;
1411 bio->bi_next = NULL;
1412 generic_make_request(bio);
1413 bio = n;
1414 }
1415}
1416
1417static int do_origin(struct dm_dev *origin, struct bio *bio);
1418
1419/*
1420 * Flush a list of buffers.
1421 */
1422static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1423{
1424 struct bio *n;
1425 int r;
1426
1427 while (bio) {
1428 n = bio->bi_next;
1429 bio->bi_next = NULL;
1430 r = do_origin(s->origin, bio);
1431 if (r == DM_MAPIO_REMAPPED)
1432 generic_make_request(bio);
1433 bio = n;
1434 }
1435}
1436
1437/*
1438 * Error a list of buffers.
1439 */
1440static void error_bios(struct bio *bio)
1441{
1442 struct bio *n;
1443
1444 while (bio) {
1445 n = bio->bi_next;
1446 bio->bi_next = NULL;
1447 bio_io_error(bio);
1448 bio = n;
1449 }
1450}
1451
1452static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1453{
1454 if (!s->valid)
1455 return;
1456
1457 if (err == -EIO)
1458 DMERR("Invalidating snapshot: Error reading/writing.");
1459 else if (err == -ENOMEM)
1460 DMERR("Invalidating snapshot: Unable to allocate exception.");
1461
1462 if (s->store->type->drop_snapshot)
1463 s->store->type->drop_snapshot(s->store);
1464
1465 s->valid = 0;
1466
1467 dm_table_event(s->ti->table);
1468}
1469
1470static void pending_complete(void *context, int success)
1471{
1472 struct dm_snap_pending_exception *pe = context;
1473 struct dm_exception *e;
1474 struct dm_snapshot *s = pe->snap;
1475 struct bio *origin_bios = NULL;
1476 struct bio *snapshot_bios = NULL;
1477 struct bio *full_bio = NULL;
1478 int error = 0;
1479
1480 if (!success) {
1481 /* Read/write error - snapshot is unusable */
1482 mutex_lock(&s->lock);
1483 __invalidate_snapshot(s, -EIO);
1484 error = 1;
1485 goto out;
1486 }
1487
1488 e = alloc_completed_exception(GFP_NOIO);
1489 if (!e) {
1490 mutex_lock(&s->lock);
1491 __invalidate_snapshot(s, -ENOMEM);
1492 error = 1;
1493 goto out;
1494 }
1495 *e = pe->e;
1496
1497 mutex_lock(&s->lock);
1498 if (!s->valid) {
1499 free_completed_exception(e);
1500 error = 1;
1501 goto out;
1502 }
1503
1504 /* Check for conflicting reads */
1505 __check_for_conflicting_io(s, pe->e.old_chunk);
1506
1507 /*
1508 * Add a proper exception, and remove the
1509 * in-flight exception from the list.
1510 */
1511 dm_insert_exception(&s->complete, e);
1512
1513out:
1514 dm_remove_exception(&pe->e);
1515 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1516 origin_bios = bio_list_get(&pe->origin_bios);
1517 full_bio = pe->full_bio;
1518 if (full_bio)
1519 full_bio->bi_end_io = pe->full_bio_end_io;
1520 increment_pending_exceptions_done_count();
1521
1522 mutex_unlock(&s->lock);
1523
1524 /* Submit any pending write bios */
1525 if (error) {
1526 if (full_bio)
1527 bio_io_error(full_bio);
1528 error_bios(snapshot_bios);
1529 } else {
1530 if (full_bio)
1531 bio_endio(full_bio);
1532 flush_bios(snapshot_bios);
1533 }
1534
1535 retry_origin_bios(s, origin_bios);
1536
1537 free_pending_exception(pe);
1538}
1539
1540static void complete_exception(struct dm_snap_pending_exception *pe)
1541{
1542 struct dm_snapshot *s = pe->snap;
1543
1544 /* Update the metadata if we are persistent */
1545 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1546 pending_complete, pe);
1547}
1548
1549/*
1550 * Called when the copy I/O has finished. kcopyd actually runs
1551 * this code so don't block.
1552 */
1553static void copy_callback(int read_err, unsigned long write_err, void *context)
1554{
1555 struct dm_snap_pending_exception *pe = context;
1556 struct dm_snapshot *s = pe->snap;
1557
1558 pe->copy_error = read_err || write_err;
1559
1560 if (pe->exception_sequence == s->exception_complete_sequence) {
1561 struct rb_node *next;
1562
1563 s->exception_complete_sequence++;
1564 complete_exception(pe);
1565
1566 next = rb_first(&s->out_of_order_tree);
1567 while (next) {
1568 pe = rb_entry(next, struct dm_snap_pending_exception,
1569 out_of_order_node);
1570 if (pe->exception_sequence != s->exception_complete_sequence)
1571 break;
1572 next = rb_next(next);
1573 s->exception_complete_sequence++;
1574 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
1575 complete_exception(pe);
1576 cond_resched();
1577 }
1578 } else {
1579 struct rb_node *parent = NULL;
1580 struct rb_node **p = &s->out_of_order_tree.rb_node;
1581 struct dm_snap_pending_exception *pe2;
1582
1583 while (*p) {
1584 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
1585 parent = *p;
1586
1587 BUG_ON(pe->exception_sequence == pe2->exception_sequence);
1588 if (pe->exception_sequence < pe2->exception_sequence)
1589 p = &((*p)->rb_left);
1590 else
1591 p = &((*p)->rb_right);
1592 }
1593
1594 rb_link_node(&pe->out_of_order_node, parent, p);
1595 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
1596 }
1597 up(&s->cow_count);
1598}
1599
1600/*
1601 * Dispatches the copy operation to kcopyd.
1602 */
1603static void start_copy(struct dm_snap_pending_exception *pe)
1604{
1605 struct dm_snapshot *s = pe->snap;
1606 struct dm_io_region src, dest;
1607 struct block_device *bdev = s->origin->bdev;
1608 sector_t dev_size;
1609
1610 dev_size = get_dev_size(bdev);
1611
1612 src.bdev = bdev;
1613 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1614 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1615
1616 dest.bdev = s->cow->bdev;
1617 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1618 dest.count = src.count;
1619
1620 /* Hand over to kcopyd */
1621 down(&s->cow_count);
1622 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1623}
1624
1625static void full_bio_end_io(struct bio *bio)
1626{
1627 void *callback_data = bio->bi_private;
1628
1629 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
1630}
1631
1632static void start_full_bio(struct dm_snap_pending_exception *pe,
1633 struct bio *bio)
1634{
1635 struct dm_snapshot *s = pe->snap;
1636 void *callback_data;
1637
1638 pe->full_bio = bio;
1639 pe->full_bio_end_io = bio->bi_end_io;
1640
1641 down(&s->cow_count);
1642 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1643 copy_callback, pe);
1644
1645 bio->bi_end_io = full_bio_end_io;
1646 bio->bi_private = callback_data;
1647
1648 generic_make_request(bio);
1649}
1650
1651static struct dm_snap_pending_exception *
1652__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1653{
1654 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1655
1656 if (!e)
1657 return NULL;
1658
1659 return container_of(e, struct dm_snap_pending_exception, e);
1660}
1661
1662/*
1663 * Looks to see if this snapshot already has a pending exception
1664 * for this chunk, otherwise it allocates a new one and inserts
1665 * it into the pending table.
1666 *
1667 * NOTE: a write lock must be held on snap->lock before calling
1668 * this.
1669 */
1670static struct dm_snap_pending_exception *
1671__find_pending_exception(struct dm_snapshot *s,
1672 struct dm_snap_pending_exception *pe, chunk_t chunk)
1673{
1674 struct dm_snap_pending_exception *pe2;
1675
1676 pe2 = __lookup_pending_exception(s, chunk);
1677 if (pe2) {
1678 free_pending_exception(pe);
1679 return pe2;
1680 }
1681
1682 pe->e.old_chunk = chunk;
1683 bio_list_init(&pe->origin_bios);
1684 bio_list_init(&pe->snapshot_bios);
1685 pe->started = 0;
1686 pe->full_bio = NULL;
1687
1688 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1689 free_pending_exception(pe);
1690 return NULL;
1691 }
1692
1693 pe->exception_sequence = s->exception_start_sequence++;
1694
1695 dm_insert_exception(&s->pending, &pe->e);
1696
1697 return pe;
1698}
1699
1700static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1701 struct bio *bio, chunk_t chunk)
1702{
1703 bio_set_dev(bio, s->cow->bdev);
1704 bio->bi_iter.bi_sector =
1705 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1706 (chunk - e->old_chunk)) +
1707 (bio->bi_iter.bi_sector & s->store->chunk_mask);
1708}
1709
1710static int snapshot_map(struct dm_target *ti, struct bio *bio)
1711{
1712 struct dm_exception *e;
1713 struct dm_snapshot *s = ti->private;
1714 int r = DM_MAPIO_REMAPPED;
1715 chunk_t chunk;
1716 struct dm_snap_pending_exception *pe = NULL;
1717
1718 init_tracked_chunk(bio);
1719
1720 if (bio->bi_opf & REQ_PREFLUSH) {
1721 bio_set_dev(bio, s->cow->bdev);
1722 return DM_MAPIO_REMAPPED;
1723 }
1724
1725 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1726
1727 /* Full snapshots are not usable */
1728 /* To get here the table must be live so s->active is always set. */
1729 if (!s->valid)
1730 return DM_MAPIO_KILL;
1731
1732 mutex_lock(&s->lock);
1733
1734 if (!s->valid || (unlikely(s->snapshot_overflowed) &&
1735 bio_data_dir(bio) == WRITE)) {
1736 r = DM_MAPIO_KILL;
1737 goto out_unlock;
1738 }
1739
1740 /* If the block is already remapped - use that, else remap it */
1741 e = dm_lookup_exception(&s->complete, chunk);
1742 if (e) {
1743 remap_exception(s, e, bio, chunk);
1744 goto out_unlock;
1745 }
1746
1747 /*
1748 * Write to snapshot - higher level takes care of RW/RO
1749 * flags so we should only get this if we are
1750 * writeable.
1751 */
1752 if (bio_data_dir(bio) == WRITE) {
1753 pe = __lookup_pending_exception(s, chunk);
1754 if (!pe) {
1755 mutex_unlock(&s->lock);
1756 pe = alloc_pending_exception(s);
1757 mutex_lock(&s->lock);
1758
1759 if (!s->valid || s->snapshot_overflowed) {
1760 free_pending_exception(pe);
1761 r = DM_MAPIO_KILL;
1762 goto out_unlock;
1763 }
1764
1765 e = dm_lookup_exception(&s->complete, chunk);
1766 if (e) {
1767 free_pending_exception(pe);
1768 remap_exception(s, e, bio, chunk);
1769 goto out_unlock;
1770 }
1771
1772 pe = __find_pending_exception(s, pe, chunk);
1773 if (!pe) {
1774 if (s->store->userspace_supports_overflow) {
1775 s->snapshot_overflowed = 1;
1776 DMERR("Snapshot overflowed: Unable to allocate exception.");
1777 } else
1778 __invalidate_snapshot(s, -ENOMEM);
1779 r = DM_MAPIO_KILL;
1780 goto out_unlock;
1781 }
1782 }
1783
1784 remap_exception(s, &pe->e, bio, chunk);
1785
1786 r = DM_MAPIO_SUBMITTED;
1787
1788 if (!pe->started &&
1789 bio->bi_iter.bi_size ==
1790 (s->store->chunk_size << SECTOR_SHIFT)) {
1791 pe->started = 1;
1792 mutex_unlock(&s->lock);
1793 start_full_bio(pe, bio);
1794 goto out;
1795 }
1796
1797 bio_list_add(&pe->snapshot_bios, bio);
1798
1799 if (!pe->started) {
1800 /* this is protected by snap->lock */
1801 pe->started = 1;
1802 mutex_unlock(&s->lock);
1803 start_copy(pe);
1804 goto out;
1805 }
1806 } else {
1807 bio_set_dev(bio, s->origin->bdev);
1808 track_chunk(s, bio, chunk);
1809 }
1810
1811out_unlock:
1812 mutex_unlock(&s->lock);
1813out:
1814 return r;
1815}
1816
1817/*
1818 * A snapshot-merge target behaves like a combination of a snapshot
1819 * target and a snapshot-origin target. It only generates new
1820 * exceptions in other snapshots and not in the one that is being
1821 * merged.
1822 *
1823 * For each chunk, if there is an existing exception, it is used to
1824 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
1825 * which in turn might generate exceptions in other snapshots.
1826 * If merging is currently taking place on the chunk in question, the
1827 * I/O is deferred by adding it to s->bios_queued_during_merge.
1828 */
1829static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
1830{
1831 struct dm_exception *e;
1832 struct dm_snapshot *s = ti->private;
1833 int r = DM_MAPIO_REMAPPED;
1834 chunk_t chunk;
1835
1836 init_tracked_chunk(bio);
1837
1838 if (bio->bi_opf & REQ_PREFLUSH) {
1839 if (!dm_bio_get_target_bio_nr(bio))
1840 bio_set_dev(bio, s->origin->bdev);
1841 else
1842 bio_set_dev(bio, s->cow->bdev);
1843 return DM_MAPIO_REMAPPED;
1844 }
1845
1846 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1847
1848 mutex_lock(&s->lock);
1849
1850 /* Full merging snapshots are redirected to the origin */
1851 if (!s->valid)
1852 goto redirect_to_origin;
1853
1854 /* If the block is already remapped - use that */
1855 e = dm_lookup_exception(&s->complete, chunk);
1856 if (e) {
1857 /* Queue writes overlapping with chunks being merged */
1858 if (bio_data_dir(bio) == WRITE &&
1859 chunk >= s->first_merging_chunk &&
1860 chunk < (s->first_merging_chunk +
1861 s->num_merging_chunks)) {
1862 bio_set_dev(bio, s->origin->bdev);
1863 bio_list_add(&s->bios_queued_during_merge, bio);
1864 r = DM_MAPIO_SUBMITTED;
1865 goto out_unlock;
1866 }
1867
1868 remap_exception(s, e, bio, chunk);
1869
1870 if (bio_data_dir(bio) == WRITE)
1871 track_chunk(s, bio, chunk);
1872 goto out_unlock;
1873 }
1874
1875redirect_to_origin:
1876 bio_set_dev(bio, s->origin->bdev);
1877
1878 if (bio_data_dir(bio) == WRITE) {
1879 mutex_unlock(&s->lock);
1880 return do_origin(s->origin, bio);
1881 }
1882
1883out_unlock:
1884 mutex_unlock(&s->lock);
1885
1886 return r;
1887}
1888
1889static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
1890 blk_status_t *error)
1891{
1892 struct dm_snapshot *s = ti->private;
1893
1894 if (is_bio_tracked(bio))
1895 stop_tracking_chunk(s, bio);
1896
1897 return DM_ENDIO_DONE;
1898}
1899
1900static void snapshot_merge_presuspend(struct dm_target *ti)
1901{
1902 struct dm_snapshot *s = ti->private;
1903
1904 stop_merge(s);
1905}
1906
1907static int snapshot_preresume(struct dm_target *ti)
1908{
1909 int r = 0;
1910 struct dm_snapshot *s = ti->private;
1911 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1912
1913 down_read(&_origins_lock);
1914 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1915 if (snap_src && snap_dest) {
1916 mutex_lock(&snap_src->lock);
1917 if (s == snap_src) {
1918 DMERR("Unable to resume snapshot source until "
1919 "handover completes.");
1920 r = -EINVAL;
1921 } else if (!dm_suspended(snap_src->ti)) {
1922 DMERR("Unable to perform snapshot handover until "
1923 "source is suspended.");
1924 r = -EINVAL;
1925 }
1926 mutex_unlock(&snap_src->lock);
1927 }
1928 up_read(&_origins_lock);
1929
1930 return r;
1931}
1932
1933static void snapshot_resume(struct dm_target *ti)
1934{
1935 struct dm_snapshot *s = ti->private;
1936 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
1937 struct dm_origin *o;
1938 struct mapped_device *origin_md = NULL;
1939 bool must_restart_merging = false;
1940
1941 down_read(&_origins_lock);
1942
1943 o = __lookup_dm_origin(s->origin->bdev);
1944 if (o)
1945 origin_md = dm_table_get_md(o->ti->table);
1946 if (!origin_md) {
1947 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
1948 if (snap_merging)
1949 origin_md = dm_table_get_md(snap_merging->ti->table);
1950 }
1951 if (origin_md == dm_table_get_md(ti->table))
1952 origin_md = NULL;
1953 if (origin_md) {
1954 if (dm_hold(origin_md))
1955 origin_md = NULL;
1956 }
1957
1958 up_read(&_origins_lock);
1959
1960 if (origin_md) {
1961 dm_internal_suspend_fast(origin_md);
1962 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
1963 must_restart_merging = true;
1964 stop_merge(snap_merging);
1965 }
1966 }
1967
1968 down_read(&_origins_lock);
1969
1970 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1971 if (snap_src && snap_dest) {
1972 mutex_lock(&snap_src->lock);
1973 mutex_lock_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1974 __handover_exceptions(snap_src, snap_dest);
1975 mutex_unlock(&snap_dest->lock);
1976 mutex_unlock(&snap_src->lock);
1977 }
1978
1979 up_read(&_origins_lock);
1980
1981 if (origin_md) {
1982 if (must_restart_merging)
1983 start_merge(snap_merging);
1984 dm_internal_resume_fast(origin_md);
1985 dm_put(origin_md);
1986 }
1987
1988 /* Now we have correct chunk size, reregister */
1989 reregister_snapshot(s);
1990
1991 mutex_lock(&s->lock);
1992 s->active = 1;
1993 mutex_unlock(&s->lock);
1994}
1995
1996static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
1997{
1998 uint32_t min_chunksize;
1999
2000 down_read(&_origins_lock);
2001 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
2002 up_read(&_origins_lock);
2003
2004 return min_chunksize;
2005}
2006
2007static void snapshot_merge_resume(struct dm_target *ti)
2008{
2009 struct dm_snapshot *s = ti->private;
2010
2011 /*
2012 * Handover exceptions from existing snapshot.
2013 */
2014 snapshot_resume(ti);
2015
2016 /*
2017 * snapshot-merge acts as an origin, so set ti->max_io_len
2018 */
2019 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
2020
2021 start_merge(s);
2022}
2023
2024static void snapshot_status(struct dm_target *ti, status_type_t type,
2025 unsigned status_flags, char *result, unsigned maxlen)
2026{
2027 unsigned sz = 0;
2028 struct dm_snapshot *snap = ti->private;
2029
2030 switch (type) {
2031 case STATUSTYPE_INFO:
2032
2033 mutex_lock(&snap->lock);
2034
2035 if (!snap->valid)
2036 DMEMIT("Invalid");
2037 else if (snap->merge_failed)
2038 DMEMIT("Merge failed");
2039 else if (snap->snapshot_overflowed)
2040 DMEMIT("Overflow");
2041 else {
2042 if (snap->store->type->usage) {
2043 sector_t total_sectors, sectors_allocated,
2044 metadata_sectors;
2045 snap->store->type->usage(snap->store,
2046 &total_sectors,
2047 &sectors_allocated,
2048 &metadata_sectors);
2049 DMEMIT("%llu/%llu %llu",
2050 (unsigned long long)sectors_allocated,
2051 (unsigned long long)total_sectors,
2052 (unsigned long long)metadata_sectors);
2053 }
2054 else
2055 DMEMIT("Unknown");
2056 }
2057
2058 mutex_unlock(&snap->lock);
2059
2060 break;
2061
2062 case STATUSTYPE_TABLE:
2063 /*
2064 * kdevname returns a static pointer so we need
2065 * to make private copies if the output is to
2066 * make sense.
2067 */
2068 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2069 snap->store->type->status(snap->store, type, result + sz,
2070 maxlen - sz);
2071 break;
2072 }
2073}
2074
2075static int snapshot_iterate_devices(struct dm_target *ti,
2076 iterate_devices_callout_fn fn, void *data)
2077{
2078 struct dm_snapshot *snap = ti->private;
2079 int r;
2080
2081 r = fn(ti, snap->origin, 0, ti->len, data);
2082
2083 if (!r)
2084 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2085
2086 return r;
2087}
2088
2089
2090/*-----------------------------------------------------------------
2091 * Origin methods
2092 *---------------------------------------------------------------*/
2093
2094/*
2095 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2096 * supplied bio was ignored. The caller may submit it immediately.
2097 * (No remapping actually occurs as the origin is always a direct linear
2098 * map.)
2099 *
2100 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2101 * and any supplied bio is added to a list to be submitted once all
2102 * the necessary exceptions exist.
2103 */
2104static int __origin_write(struct list_head *snapshots, sector_t sector,
2105 struct bio *bio)
2106{
2107 int r = DM_MAPIO_REMAPPED;
2108 struct dm_snapshot *snap;
2109 struct dm_exception *e;
2110 struct dm_snap_pending_exception *pe;
2111 struct dm_snap_pending_exception *pe_to_start_now = NULL;
2112 struct dm_snap_pending_exception *pe_to_start_last = NULL;
2113 chunk_t chunk;
2114
2115 /* Do all the snapshots on this origin */
2116 list_for_each_entry (snap, snapshots, list) {
2117 /*
2118 * Don't make new exceptions in a merging snapshot
2119 * because it has effectively been deleted
2120 */
2121 if (dm_target_is_snapshot_merge(snap->ti))
2122 continue;
2123
2124 mutex_lock(&snap->lock);
2125
2126 /* Only deal with valid and active snapshots */
2127 if (!snap->valid || !snap->active)
2128 goto next_snapshot;
2129
2130 /* Nothing to do if writing beyond end of snapshot */
2131 if (sector >= dm_table_get_size(snap->ti->table))
2132 goto next_snapshot;
2133
2134 /*
2135 * Remember, different snapshots can have
2136 * different chunk sizes.
2137 */
2138 chunk = sector_to_chunk(snap->store, sector);
2139
2140 /*
2141 * Check exception table to see if block
2142 * is already remapped in this snapshot
2143 * and trigger an exception if not.
2144 */
2145 e = dm_lookup_exception(&snap->complete, chunk);
2146 if (e)
2147 goto next_snapshot;
2148
2149 pe = __lookup_pending_exception(snap, chunk);
2150 if (!pe) {
2151 mutex_unlock(&snap->lock);
2152 pe = alloc_pending_exception(snap);
2153 mutex_lock(&snap->lock);
2154
2155 if (!snap->valid) {
2156 free_pending_exception(pe);
2157 goto next_snapshot;
2158 }
2159
2160 e = dm_lookup_exception(&snap->complete, chunk);
2161 if (e) {
2162 free_pending_exception(pe);
2163 goto next_snapshot;
2164 }
2165
2166 pe = __find_pending_exception(snap, pe, chunk);
2167 if (!pe) {
2168 __invalidate_snapshot(snap, -ENOMEM);
2169 goto next_snapshot;
2170 }
2171 }
2172
2173 r = DM_MAPIO_SUBMITTED;
2174
2175 /*
2176 * If an origin bio was supplied, queue it to wait for the
2177 * completion of this exception, and start this one last,
2178 * at the end of the function.
2179 */
2180 if (bio) {
2181 bio_list_add(&pe->origin_bios, bio);
2182 bio = NULL;
2183
2184 if (!pe->started) {
2185 pe->started = 1;
2186 pe_to_start_last = pe;
2187 }
2188 }
2189
2190 if (!pe->started) {
2191 pe->started = 1;
2192 pe_to_start_now = pe;
2193 }
2194
2195next_snapshot:
2196 mutex_unlock(&snap->lock);
2197
2198 if (pe_to_start_now) {
2199 start_copy(pe_to_start_now);
2200 pe_to_start_now = NULL;
2201 }
2202 }
2203
2204 /*
2205 * Submit the exception against which the bio is queued last,
2206 * to give the other exceptions a head start.
2207 */
2208 if (pe_to_start_last)
2209 start_copy(pe_to_start_last);
2210
2211 return r;
2212}
2213
2214/*
2215 * Called on a write from the origin driver.
2216 */
2217static int do_origin(struct dm_dev *origin, struct bio *bio)
2218{
2219 struct origin *o;
2220 int r = DM_MAPIO_REMAPPED;
2221
2222 down_read(&_origins_lock);
2223 o = __lookup_origin(origin->bdev);
2224 if (o)
2225 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
2226 up_read(&_origins_lock);
2227
2228 return r;
2229}
2230
2231/*
2232 * Trigger exceptions in all non-merging snapshots.
2233 *
2234 * The chunk size of the merging snapshot may be larger than the chunk
2235 * size of some other snapshot so we may need to reallocate multiple
2236 * chunks in other snapshots.
2237 *
2238 * We scan all the overlapping exceptions in the other snapshots.
2239 * Returns 1 if anything was reallocated and must be waited for,
2240 * otherwise returns 0.
2241 *
2242 * size must be a multiple of merging_snap's chunk_size.
2243 */
2244static int origin_write_extent(struct dm_snapshot *merging_snap,
2245 sector_t sector, unsigned size)
2246{
2247 int must_wait = 0;
2248 sector_t n;
2249 struct origin *o;
2250
2251 /*
2252 * The origin's __minimum_chunk_size() got stored in max_io_len
2253 * by snapshot_merge_resume().
2254 */
2255 down_read(&_origins_lock);
2256 o = __lookup_origin(merging_snap->origin->bdev);
2257 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2258 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2259 DM_MAPIO_SUBMITTED)
2260 must_wait = 1;
2261 up_read(&_origins_lock);
2262
2263 return must_wait;
2264}
2265
2266/*
2267 * Origin: maps a linear range of a device, with hooks for snapshotting.
2268 */
2269
2270/*
2271 * Construct an origin mapping: <dev_path>
2272 * The context for an origin is merely a 'struct dm_dev *'
2273 * pointing to the real device.
2274 */
2275static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2276{
2277 int r;
2278 struct dm_origin *o;
2279
2280 if (argc != 1) {
2281 ti->error = "origin: incorrect number of arguments";
2282 return -EINVAL;
2283 }
2284
2285 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2286 if (!o) {
2287 ti->error = "Cannot allocate private origin structure";
2288 r = -ENOMEM;
2289 goto bad_alloc;
2290 }
2291
2292 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2293 if (r) {
2294 ti->error = "Cannot get target device";
2295 goto bad_open;
2296 }
2297
2298 o->ti = ti;
2299 ti->private = o;
2300 ti->num_flush_bios = 1;
2301
2302 return 0;
2303
2304bad_open:
2305 kfree(o);
2306bad_alloc:
2307 return r;
2308}
2309
2310static void origin_dtr(struct dm_target *ti)
2311{
2312 struct dm_origin *o = ti->private;
2313
2314 dm_put_device(ti, o->dev);
2315 kfree(o);
2316}
2317
2318static int origin_map(struct dm_target *ti, struct bio *bio)
2319{
2320 struct dm_origin *o = ti->private;
2321 unsigned available_sectors;
2322
2323 bio_set_dev(bio, o->dev->bdev);
2324
2325 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2326 return DM_MAPIO_REMAPPED;
2327
2328 if (bio_data_dir(bio) != WRITE)
2329 return DM_MAPIO_REMAPPED;
2330
2331 available_sectors = o->split_boundary -
2332 ((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2333
2334 if (bio_sectors(bio) > available_sectors)
2335 dm_accept_partial_bio(bio, available_sectors);
2336
2337 /* Only tell snapshots if this is a write */
2338 return do_origin(o->dev, bio);
2339}
2340
2341/*
2342 * Set the target "max_io_len" field to the minimum of all the snapshots'
2343 * chunk sizes.
2344 */
2345static void origin_resume(struct dm_target *ti)
2346{
2347 struct dm_origin *o = ti->private;
2348
2349 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2350
2351 down_write(&_origins_lock);
2352 __insert_dm_origin(o);
2353 up_write(&_origins_lock);
2354}
2355
2356static void origin_postsuspend(struct dm_target *ti)
2357{
2358 struct dm_origin *o = ti->private;
2359
2360 down_write(&_origins_lock);
2361 __remove_dm_origin(o);
2362 up_write(&_origins_lock);
2363}
2364
2365static void origin_status(struct dm_target *ti, status_type_t type,
2366 unsigned status_flags, char *result, unsigned maxlen)
2367{
2368 struct dm_origin *o = ti->private;
2369
2370 switch (type) {
2371 case STATUSTYPE_INFO:
2372 result[0] = '\0';
2373 break;
2374
2375 case STATUSTYPE_TABLE:
2376 snprintf(result, maxlen, "%s", o->dev->name);
2377 break;
2378 }
2379}
2380
2381static int origin_iterate_devices(struct dm_target *ti,
2382 iterate_devices_callout_fn fn, void *data)
2383{
2384 struct dm_origin *o = ti->private;
2385
2386 return fn(ti, o->dev, 0, ti->len, data);
2387}
2388
2389static struct target_type origin_target = {
2390 .name = "snapshot-origin",
2391 .version = {1, 9, 0},
2392 .module = THIS_MODULE,
2393 .ctr = origin_ctr,
2394 .dtr = origin_dtr,
2395 .map = origin_map,
2396 .resume = origin_resume,
2397 .postsuspend = origin_postsuspend,
2398 .status = origin_status,
2399 .iterate_devices = origin_iterate_devices,
2400};
2401
2402static struct target_type snapshot_target = {
2403 .name = "snapshot",
2404 .version = {1, 15, 0},
2405 .module = THIS_MODULE,
2406 .ctr = snapshot_ctr,
2407 .dtr = snapshot_dtr,
2408 .map = snapshot_map,
2409 .end_io = snapshot_end_io,
2410 .preresume = snapshot_preresume,
2411 .resume = snapshot_resume,
2412 .status = snapshot_status,
2413 .iterate_devices = snapshot_iterate_devices,
2414};
2415
2416static struct target_type merge_target = {
2417 .name = dm_snapshot_merge_target_name,
2418 .version = {1, 4, 0},
2419 .module = THIS_MODULE,
2420 .ctr = snapshot_ctr,
2421 .dtr = snapshot_dtr,
2422 .map = snapshot_merge_map,
2423 .end_io = snapshot_end_io,
2424 .presuspend = snapshot_merge_presuspend,
2425 .preresume = snapshot_preresume,
2426 .resume = snapshot_merge_resume,
2427 .status = snapshot_status,
2428 .iterate_devices = snapshot_iterate_devices,
2429};
2430
2431static int __init dm_snapshot_init(void)
2432{
2433 int r;
2434
2435 r = dm_exception_store_init();
2436 if (r) {
2437 DMERR("Failed to initialize exception stores");
2438 return r;
2439 }
2440
2441 r = init_origin_hash();
2442 if (r) {
2443 DMERR("init_origin_hash failed.");
2444 goto bad_origin_hash;
2445 }
2446
2447 exception_cache = KMEM_CACHE(dm_exception, 0);
2448 if (!exception_cache) {
2449 DMERR("Couldn't create exception cache.");
2450 r = -ENOMEM;
2451 goto bad_exception_cache;
2452 }
2453
2454 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2455 if (!pending_cache) {
2456 DMERR("Couldn't create pending cache.");
2457 r = -ENOMEM;
2458 goto bad_pending_cache;
2459 }
2460
2461 r = dm_register_target(&snapshot_target);
2462 if (r < 0) {
2463 DMERR("snapshot target register failed %d", r);
2464 goto bad_register_snapshot_target;
2465 }
2466
2467 r = dm_register_target(&origin_target);
2468 if (r < 0) {
2469 DMERR("Origin target register failed %d", r);
2470 goto bad_register_origin_target;
2471 }
2472
2473 r = dm_register_target(&merge_target);
2474 if (r < 0) {
2475 DMERR("Merge target register failed %d", r);
2476 goto bad_register_merge_target;
2477 }
2478
2479 return 0;
2480
2481bad_register_merge_target:
2482 dm_unregister_target(&origin_target);
2483bad_register_origin_target:
2484 dm_unregister_target(&snapshot_target);
2485bad_register_snapshot_target:
2486 kmem_cache_destroy(pending_cache);
2487bad_pending_cache:
2488 kmem_cache_destroy(exception_cache);
2489bad_exception_cache:
2490 exit_origin_hash();
2491bad_origin_hash:
2492 dm_exception_store_exit();
2493
2494 return r;
2495}
2496
2497static void __exit dm_snapshot_exit(void)
2498{
2499 dm_unregister_target(&snapshot_target);
2500 dm_unregister_target(&origin_target);
2501 dm_unregister_target(&merge_target);
2502
2503 exit_origin_hash();
2504 kmem_cache_destroy(pending_cache);
2505 kmem_cache_destroy(exception_cache);
2506
2507 dm_exception_store_exit();
2508}
2509
2510/* Module hooks */
2511module_init(dm_snapshot_init);
2512module_exit(dm_snapshot_exit);
2513
2514MODULE_DESCRIPTION(DM_NAME " snapshot target");
2515MODULE_AUTHOR("Joe Thornber");
2516MODULE_LICENSE("GPL");
2517MODULE_ALIAS("dm-snapshot-origin");
2518MODULE_ALIAS("dm-snapshot-merge");
2519