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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
4 *
5 * This file is released under the GPL.
6 */
7
8#include <linux/blkdev.h>
9#include <linux/device-mapper.h>
10#include <linux/delay.h>
11#include <linux/fs.h>
12#include <linux/init.h>
13#include <linux/kdev_t.h>
14#include <linux/list.h>
15#include <linux/list_bl.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.h"
24
25#include "dm-exception-store.h"
26
27#define DM_MSG_PREFIX "snapshots"
28
29static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
30
31#define dm_target_is_snapshot_merge(ti) \
32 ((ti)->type->name == dm_snapshot_merge_target_name)
33
34/*
35 * The size of the mempool used to track chunks in use.
36 */
37#define MIN_IOS 256
38
39#define DM_TRACKED_CHUNK_HASH_SIZE 16
40#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
41 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
42
43struct dm_exception_table {
44 uint32_t hash_mask;
45 unsigned int hash_shift;
46 struct hlist_bl_head *table;
47};
48
49struct dm_snapshot {
50 struct rw_semaphore lock;
51
52 struct dm_dev *origin;
53 struct dm_dev *cow;
54
55 struct dm_target *ti;
56
57 /* List of snapshots per Origin */
58 struct list_head list;
59
60 /*
61 * You can't use a snapshot if this is 0 (e.g. if full).
62 * A snapshot-merge target never clears this.
63 */
64 int valid;
65
66 /*
67 * The snapshot overflowed because of a write to the snapshot device.
68 * We don't have to invalidate the snapshot in this case, but we need
69 * to prevent further writes.
70 */
71 int snapshot_overflowed;
72
73 /* Origin writes don't trigger exceptions until this is set */
74 int active;
75
76 atomic_t pending_exceptions_count;
77
78 spinlock_t pe_allocation_lock;
79
80 /* Protected by "pe_allocation_lock" */
81 sector_t exception_start_sequence;
82
83 /* Protected by kcopyd single-threaded callback */
84 sector_t exception_complete_sequence;
85
86 /*
87 * A list of pending exceptions that completed out of order.
88 * Protected by kcopyd single-threaded callback.
89 */
90 struct rb_root out_of_order_tree;
91
92 mempool_t pending_pool;
93
94 struct dm_exception_table pending;
95 struct dm_exception_table complete;
96
97 /*
98 * pe_lock protects all pending_exception operations and access
99 * as well as the snapshot_bios list.
100 */
101 spinlock_t pe_lock;
102
103 /* Chunks with outstanding reads */
104 spinlock_t tracked_chunk_lock;
105 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
106
107 /* The on disk metadata handler */
108 struct dm_exception_store *store;
109
110 unsigned int in_progress;
111 struct wait_queue_head in_progress_wait;
112
113 struct dm_kcopyd_client *kcopyd_client;
114
115 /* Wait for events based on state_bits */
116 unsigned long state_bits;
117
118 /* Range of chunks currently being merged. */
119 chunk_t first_merging_chunk;
120 int num_merging_chunks;
121
122 /*
123 * The merge operation failed if this flag is set.
124 * Failure modes are handled as follows:
125 * - I/O error reading the header
126 * => don't load the target; abort.
127 * - Header does not have "valid" flag set
128 * => use the origin; forget about the snapshot.
129 * - I/O error when reading exceptions
130 * => don't load the target; abort.
131 * (We can't use the intermediate origin state.)
132 * - I/O error while merging
133 * => stop merging; set merge_failed; process I/O normally.
134 */
135 bool merge_failed:1;
136
137 bool discard_zeroes_cow:1;
138 bool discard_passdown_origin:1;
139
140 /*
141 * Incoming bios that overlap with chunks being merged must wait
142 * for them to be committed.
143 */
144 struct bio_list bios_queued_during_merge;
145};
146
147/*
148 * state_bits:
149 * RUNNING_MERGE - Merge operation is in progress.
150 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
151 * cleared afterwards.
152 */
153#define RUNNING_MERGE 0
154#define SHUTDOWN_MERGE 1
155
156/*
157 * Maximum number of chunks being copied on write.
158 *
159 * The value was decided experimentally as a trade-off between memory
160 * consumption, stalling the kernel's workqueues and maintaining a high enough
161 * throughput.
162 */
163#define DEFAULT_COW_THRESHOLD 2048
164
165static unsigned int cow_threshold = DEFAULT_COW_THRESHOLD;
166module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);
167MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
168
169DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
170 "A percentage of time allocated for copy on write");
171
172struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
173{
174 return s->origin;
175}
176EXPORT_SYMBOL(dm_snap_origin);
177
178struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
179{
180 return s->cow;
181}
182EXPORT_SYMBOL(dm_snap_cow);
183
184static sector_t chunk_to_sector(struct dm_exception_store *store,
185 chunk_t chunk)
186{
187 return chunk << store->chunk_shift;
188}
189
190static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
191{
192 /*
193 * There is only ever one instance of a particular block
194 * device so we can compare pointers safely.
195 */
196 return lhs == rhs;
197}
198
199struct dm_snap_pending_exception {
200 struct dm_exception e;
201
202 /*
203 * Origin buffers waiting for this to complete are held
204 * in a bio list
205 */
206 struct bio_list origin_bios;
207 struct bio_list snapshot_bios;
208
209 /* Pointer back to snapshot context */
210 struct dm_snapshot *snap;
211
212 /*
213 * 1 indicates the exception has already been sent to
214 * kcopyd.
215 */
216 int started;
217
218 /* There was copying error. */
219 int copy_error;
220
221 /* A sequence number, it is used for in-order completion. */
222 sector_t exception_sequence;
223
224 struct rb_node out_of_order_node;
225
226 /*
227 * For writing a complete chunk, bypassing the copy.
228 */
229 struct bio *full_bio;
230 bio_end_io_t *full_bio_end_io;
231};
232
233/*
234 * Hash table mapping origin volumes to lists of snapshots and
235 * a lock to protect it
236 */
237static struct kmem_cache *exception_cache;
238static struct kmem_cache *pending_cache;
239
240struct dm_snap_tracked_chunk {
241 struct hlist_node node;
242 chunk_t chunk;
243};
244
245static void init_tracked_chunk(struct bio *bio)
246{
247 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
248
249 INIT_HLIST_NODE(&c->node);
250}
251
252static bool is_bio_tracked(struct bio *bio)
253{
254 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
255
256 return !hlist_unhashed(&c->node);
257}
258
259static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
260{
261 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
262
263 c->chunk = chunk;
264
265 spin_lock_irq(&s->tracked_chunk_lock);
266 hlist_add_head(&c->node,
267 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
268 spin_unlock_irq(&s->tracked_chunk_lock);
269}
270
271static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
272{
273 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
274 unsigned long flags;
275
276 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
277 hlist_del(&c->node);
278 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
279}
280
281static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
282{
283 struct dm_snap_tracked_chunk *c;
284 int found = 0;
285
286 spin_lock_irq(&s->tracked_chunk_lock);
287
288 hlist_for_each_entry(c,
289 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
290 if (c->chunk == chunk) {
291 found = 1;
292 break;
293 }
294 }
295
296 spin_unlock_irq(&s->tracked_chunk_lock);
297
298 return found;
299}
300
301/*
302 * This conflicting I/O is extremely improbable in the caller,
303 * so fsleep(1000) is sufficient and there is no need for a wait queue.
304 */
305static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
306{
307 while (__chunk_is_tracked(s, chunk))
308 fsleep(1000);
309}
310
311/*
312 * One of these per registered origin, held in the snapshot_origins hash
313 */
314struct origin {
315 /* The origin device */
316 struct block_device *bdev;
317
318 struct list_head hash_list;
319
320 /* List of snapshots for this origin */
321 struct list_head snapshots;
322};
323
324/*
325 * This structure is allocated for each origin target
326 */
327struct dm_origin {
328 struct dm_dev *dev;
329 struct dm_target *ti;
330 unsigned int split_boundary;
331 struct list_head hash_list;
332};
333
334/*
335 * Size of the hash table for origin volumes. If we make this
336 * the size of the minors list then it should be nearly perfect
337 */
338#define ORIGIN_HASH_SIZE 256
339#define ORIGIN_MASK 0xFF
340static struct list_head *_origins;
341static struct list_head *_dm_origins;
342static struct rw_semaphore _origins_lock;
343
344static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
345static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
346static uint64_t _pending_exceptions_done_count;
347
348static int init_origin_hash(void)
349{
350 int i;
351
352 _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),
353 GFP_KERNEL);
354 if (!_origins) {
355 DMERR("unable to allocate memory for _origins");
356 return -ENOMEM;
357 }
358 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
359 INIT_LIST_HEAD(_origins + i);
360
361 _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,
362 sizeof(struct list_head),
363 GFP_KERNEL);
364 if (!_dm_origins) {
365 DMERR("unable to allocate memory for _dm_origins");
366 kfree(_origins);
367 return -ENOMEM;
368 }
369 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
370 INIT_LIST_HEAD(_dm_origins + i);
371
372 init_rwsem(&_origins_lock);
373
374 return 0;
375}
376
377static void exit_origin_hash(void)
378{
379 kfree(_origins);
380 kfree(_dm_origins);
381}
382
383static unsigned int origin_hash(struct block_device *bdev)
384{
385 return bdev->bd_dev & ORIGIN_MASK;
386}
387
388static struct origin *__lookup_origin(struct block_device *origin)
389{
390 struct list_head *ol;
391 struct origin *o;
392
393 ol = &_origins[origin_hash(origin)];
394 list_for_each_entry(o, ol, hash_list)
395 if (bdev_equal(o->bdev, origin))
396 return o;
397
398 return NULL;
399}
400
401static void __insert_origin(struct origin *o)
402{
403 struct list_head *sl = &_origins[origin_hash(o->bdev)];
404
405 list_add_tail(&o->hash_list, sl);
406}
407
408static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
409{
410 struct list_head *ol;
411 struct dm_origin *o;
412
413 ol = &_dm_origins[origin_hash(origin)];
414 list_for_each_entry(o, ol, hash_list)
415 if (bdev_equal(o->dev->bdev, origin))
416 return o;
417
418 return NULL;
419}
420
421static void __insert_dm_origin(struct dm_origin *o)
422{
423 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
424
425 list_add_tail(&o->hash_list, sl);
426}
427
428static void __remove_dm_origin(struct dm_origin *o)
429{
430 list_del(&o->hash_list);
431}
432
433/*
434 * _origins_lock must be held when calling this function.
435 * Returns number of snapshots registered using the supplied cow device, plus:
436 * snap_src - a snapshot suitable for use as a source of exception handover
437 * snap_dest - a snapshot capable of receiving exception handover.
438 * snap_merge - an existing snapshot-merge target linked to the same origin.
439 * There can be at most one snapshot-merge target. The parameter is optional.
440 *
441 * Possible return values and states of snap_src and snap_dest.
442 * 0: NULL, NULL - first new snapshot
443 * 1: snap_src, NULL - normal snapshot
444 * 2: snap_src, snap_dest - waiting for handover
445 * 2: snap_src, NULL - handed over, waiting for old to be deleted
446 * 1: NULL, snap_dest - source got destroyed without handover
447 */
448static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
449 struct dm_snapshot **snap_src,
450 struct dm_snapshot **snap_dest,
451 struct dm_snapshot **snap_merge)
452{
453 struct dm_snapshot *s;
454 struct origin *o;
455 int count = 0;
456 int active;
457
458 o = __lookup_origin(snap->origin->bdev);
459 if (!o)
460 goto out;
461
462 list_for_each_entry(s, &o->snapshots, list) {
463 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
464 *snap_merge = s;
465 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
466 continue;
467
468 down_read(&s->lock);
469 active = s->active;
470 up_read(&s->lock);
471
472 if (active) {
473 if (snap_src)
474 *snap_src = s;
475 } else if (snap_dest)
476 *snap_dest = s;
477
478 count++;
479 }
480
481out:
482 return count;
483}
484
485/*
486 * On success, returns 1 if this snapshot is a handover destination,
487 * otherwise returns 0.
488 */
489static int __validate_exception_handover(struct dm_snapshot *snap)
490{
491 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
492 struct dm_snapshot *snap_merge = NULL;
493
494 /* Does snapshot need exceptions handed over to it? */
495 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
496 &snap_merge) == 2) ||
497 snap_dest) {
498 snap->ti->error = "Snapshot cow pairing for exception table handover failed";
499 return -EINVAL;
500 }
501
502 /*
503 * If no snap_src was found, snap cannot become a handover
504 * destination.
505 */
506 if (!snap_src)
507 return 0;
508
509 /*
510 * Non-snapshot-merge handover?
511 */
512 if (!dm_target_is_snapshot_merge(snap->ti))
513 return 1;
514
515 /*
516 * Do not allow more than one merging snapshot.
517 */
518 if (snap_merge) {
519 snap->ti->error = "A snapshot is already merging.";
520 return -EINVAL;
521 }
522
523 if (!snap_src->store->type->prepare_merge ||
524 !snap_src->store->type->commit_merge) {
525 snap->ti->error = "Snapshot exception store does not support snapshot-merge.";
526 return -EINVAL;
527 }
528
529 return 1;
530}
531
532static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
533{
534 struct dm_snapshot *l;
535
536 /* Sort the list according to chunk size, largest-first smallest-last */
537 list_for_each_entry(l, &o->snapshots, list)
538 if (l->store->chunk_size < s->store->chunk_size)
539 break;
540 list_add_tail(&s->list, &l->list);
541}
542
543/*
544 * Make a note of the snapshot and its origin so we can look it
545 * up when the origin has a write on it.
546 *
547 * Also validate snapshot exception store handovers.
548 * On success, returns 1 if this registration is a handover destination,
549 * otherwise returns 0.
550 */
551static int register_snapshot(struct dm_snapshot *snap)
552{
553 struct origin *o, *new_o = NULL;
554 struct block_device *bdev = snap->origin->bdev;
555 int r = 0;
556
557 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
558 if (!new_o)
559 return -ENOMEM;
560
561 down_write(&_origins_lock);
562
563 r = __validate_exception_handover(snap);
564 if (r < 0) {
565 kfree(new_o);
566 goto out;
567 }
568
569 o = __lookup_origin(bdev);
570 if (o)
571 kfree(new_o);
572 else {
573 /* New origin */
574 o = new_o;
575
576 /* Initialise the struct */
577 INIT_LIST_HEAD(&o->snapshots);
578 o->bdev = bdev;
579
580 __insert_origin(o);
581 }
582
583 __insert_snapshot(o, snap);
584
585out:
586 up_write(&_origins_lock);
587
588 return r;
589}
590
591/*
592 * Move snapshot to correct place in list according to chunk size.
593 */
594static void reregister_snapshot(struct dm_snapshot *s)
595{
596 struct block_device *bdev = s->origin->bdev;
597
598 down_write(&_origins_lock);
599
600 list_del(&s->list);
601 __insert_snapshot(__lookup_origin(bdev), s);
602
603 up_write(&_origins_lock);
604}
605
606static void unregister_snapshot(struct dm_snapshot *s)
607{
608 struct origin *o;
609
610 down_write(&_origins_lock);
611 o = __lookup_origin(s->origin->bdev);
612
613 list_del(&s->list);
614 if (o && list_empty(&o->snapshots)) {
615 list_del(&o->hash_list);
616 kfree(o);
617 }
618
619 up_write(&_origins_lock);
620}
621
622/*
623 * Implementation of the exception hash tables.
624 * The lowest hash_shift bits of the chunk number are ignored, allowing
625 * some consecutive chunks to be grouped together.
626 */
627static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk);
628
629/* Lock to protect access to the completed and pending exception hash tables. */
630struct dm_exception_table_lock {
631 struct hlist_bl_head *complete_slot;
632 struct hlist_bl_head *pending_slot;
633};
634
635static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk,
636 struct dm_exception_table_lock *lock)
637{
638 struct dm_exception_table *complete = &s->complete;
639 struct dm_exception_table *pending = &s->pending;
640
641 lock->complete_slot = &complete->table[exception_hash(complete, chunk)];
642 lock->pending_slot = &pending->table[exception_hash(pending, chunk)];
643}
644
645static void dm_exception_table_lock(struct dm_exception_table_lock *lock)
646{
647 hlist_bl_lock(lock->complete_slot);
648 hlist_bl_lock(lock->pending_slot);
649}
650
651static void dm_exception_table_unlock(struct dm_exception_table_lock *lock)
652{
653 hlist_bl_unlock(lock->pending_slot);
654 hlist_bl_unlock(lock->complete_slot);
655}
656
657static int dm_exception_table_init(struct dm_exception_table *et,
658 uint32_t size, unsigned int hash_shift)
659{
660 unsigned int i;
661
662 et->hash_shift = hash_shift;
663 et->hash_mask = size - 1;
664 et->table = kvmalloc_array(size, sizeof(struct hlist_bl_head),
665 GFP_KERNEL);
666 if (!et->table)
667 return -ENOMEM;
668
669 for (i = 0; i < size; i++)
670 INIT_HLIST_BL_HEAD(et->table + i);
671
672 return 0;
673}
674
675static void dm_exception_table_exit(struct dm_exception_table *et,
676 struct kmem_cache *mem)
677{
678 struct hlist_bl_head *slot;
679 struct dm_exception *ex;
680 struct hlist_bl_node *pos, *n;
681 int i, size;
682
683 size = et->hash_mask + 1;
684 for (i = 0; i < size; i++) {
685 slot = et->table + i;
686
687 hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
688 kmem_cache_free(mem, ex);
689 }
690
691 kvfree(et->table);
692}
693
694static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
695{
696 return (chunk >> et->hash_shift) & et->hash_mask;
697}
698
699static void dm_remove_exception(struct dm_exception *e)
700{
701 hlist_bl_del(&e->hash_list);
702}
703
704/*
705 * Return the exception data for a sector, or NULL if not
706 * remapped.
707 */
708static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
709 chunk_t chunk)
710{
711 struct hlist_bl_head *slot;
712 struct hlist_bl_node *pos;
713 struct dm_exception *e;
714
715 slot = &et->table[exception_hash(et, chunk)];
716 hlist_bl_for_each_entry(e, pos, slot, hash_list)
717 if (chunk >= e->old_chunk &&
718 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
719 return e;
720
721 return NULL;
722}
723
724static struct dm_exception *alloc_completed_exception(gfp_t gfp)
725{
726 struct dm_exception *e;
727
728 e = kmem_cache_alloc(exception_cache, gfp);
729 if (!e && gfp == GFP_NOIO)
730 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
731
732 return e;
733}
734
735static void free_completed_exception(struct dm_exception *e)
736{
737 kmem_cache_free(exception_cache, e);
738}
739
740static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
741{
742 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
743 GFP_NOIO);
744
745 atomic_inc(&s->pending_exceptions_count);
746 pe->snap = s;
747
748 return pe;
749}
750
751static void free_pending_exception(struct dm_snap_pending_exception *pe)
752{
753 struct dm_snapshot *s = pe->snap;
754
755 mempool_free(pe, &s->pending_pool);
756 smp_mb__before_atomic();
757 atomic_dec(&s->pending_exceptions_count);
758}
759
760static void dm_insert_exception(struct dm_exception_table *eh,
761 struct dm_exception *new_e)
762{
763 struct hlist_bl_head *l;
764 struct hlist_bl_node *pos;
765 struct dm_exception *e = NULL;
766
767 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
768
769 /* Add immediately if this table doesn't support consecutive chunks */
770 if (!eh->hash_shift)
771 goto out;
772
773 /* List is ordered by old_chunk */
774 hlist_bl_for_each_entry(e, pos, l, hash_list) {
775 /* Insert after an existing chunk? */
776 if (new_e->old_chunk == (e->old_chunk +
777 dm_consecutive_chunk_count(e) + 1) &&
778 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
779 dm_consecutive_chunk_count(e) + 1)) {
780 dm_consecutive_chunk_count_inc(e);
781 free_completed_exception(new_e);
782 return;
783 }
784
785 /* Insert before an existing chunk? */
786 if (new_e->old_chunk == (e->old_chunk - 1) &&
787 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
788 dm_consecutive_chunk_count_inc(e);
789 e->old_chunk--;
790 e->new_chunk--;
791 free_completed_exception(new_e);
792 return;
793 }
794
795 if (new_e->old_chunk < e->old_chunk)
796 break;
797 }
798
799out:
800 if (!e) {
801 /*
802 * Either the table doesn't support consecutive chunks or slot
803 * l is empty.
804 */
805 hlist_bl_add_head(&new_e->hash_list, l);
806 } else if (new_e->old_chunk < e->old_chunk) {
807 /* Add before an existing exception */
808 hlist_bl_add_before(&new_e->hash_list, &e->hash_list);
809 } else {
810 /* Add to l's tail: e is the last exception in this slot */
811 hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);
812 }
813}
814
815/*
816 * Callback used by the exception stores to load exceptions when
817 * initialising.
818 */
819static int dm_add_exception(void *context, chunk_t old, chunk_t new)
820{
821 struct dm_exception_table_lock lock;
822 struct dm_snapshot *s = context;
823 struct dm_exception *e;
824
825 e = alloc_completed_exception(GFP_KERNEL);
826 if (!e)
827 return -ENOMEM;
828
829 e->old_chunk = old;
830
831 /* Consecutive_count is implicitly initialised to zero */
832 e->new_chunk = new;
833
834 /*
835 * Although there is no need to lock access to the exception tables
836 * here, if we don't then hlist_bl_add_head(), called by
837 * dm_insert_exception(), will complain about accessing the
838 * corresponding list without locking it first.
839 */
840 dm_exception_table_lock_init(s, old, &lock);
841
842 dm_exception_table_lock(&lock);
843 dm_insert_exception(&s->complete, e);
844 dm_exception_table_unlock(&lock);
845
846 return 0;
847}
848
849/*
850 * Return a minimum chunk size of all snapshots that have the specified origin.
851 * Return zero if the origin has no snapshots.
852 */
853static uint32_t __minimum_chunk_size(struct origin *o)
854{
855 struct dm_snapshot *snap;
856 unsigned int chunk_size = rounddown_pow_of_two(UINT_MAX);
857
858 if (o)
859 list_for_each_entry(snap, &o->snapshots, list)
860 chunk_size = min_not_zero(chunk_size,
861 snap->store->chunk_size);
862
863 return (uint32_t) chunk_size;
864}
865
866/*
867 * Hard coded magic.
868 */
869static int calc_max_buckets(void)
870{
871 /* use a fixed size of 2MB */
872 unsigned long mem = 2 * 1024 * 1024;
873
874 mem /= sizeof(struct hlist_bl_head);
875
876 return mem;
877}
878
879/*
880 * Allocate room for a suitable hash table.
881 */
882static int init_hash_tables(struct dm_snapshot *s)
883{
884 sector_t hash_size, cow_dev_size, max_buckets;
885
886 /*
887 * Calculate based on the size of the original volume or
888 * the COW volume...
889 */
890 cow_dev_size = get_dev_size(s->cow->bdev);
891 max_buckets = calc_max_buckets();
892
893 hash_size = cow_dev_size >> s->store->chunk_shift;
894 hash_size = min(hash_size, max_buckets);
895
896 if (hash_size < 64)
897 hash_size = 64;
898 hash_size = rounddown_pow_of_two(hash_size);
899 if (dm_exception_table_init(&s->complete, hash_size,
900 DM_CHUNK_CONSECUTIVE_BITS))
901 return -ENOMEM;
902
903 /*
904 * Allocate hash table for in-flight exceptions
905 * Make this smaller than the real hash table
906 */
907 hash_size >>= 3;
908 if (hash_size < 64)
909 hash_size = 64;
910
911 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
912 dm_exception_table_exit(&s->complete, exception_cache);
913 return -ENOMEM;
914 }
915
916 return 0;
917}
918
919static void merge_shutdown(struct dm_snapshot *s)
920{
921 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
922 smp_mb__after_atomic();
923 wake_up_bit(&s->state_bits, RUNNING_MERGE);
924}
925
926static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
927{
928 s->first_merging_chunk = 0;
929 s->num_merging_chunks = 0;
930
931 return bio_list_get(&s->bios_queued_during_merge);
932}
933
934/*
935 * Remove one chunk from the index of completed exceptions.
936 */
937static int __remove_single_exception_chunk(struct dm_snapshot *s,
938 chunk_t old_chunk)
939{
940 struct dm_exception *e;
941
942 e = dm_lookup_exception(&s->complete, old_chunk);
943 if (!e) {
944 DMERR("Corruption detected: exception for block %llu is on disk but not in memory",
945 (unsigned long long)old_chunk);
946 return -EINVAL;
947 }
948
949 /*
950 * If this is the only chunk using this exception, remove exception.
951 */
952 if (!dm_consecutive_chunk_count(e)) {
953 dm_remove_exception(e);
954 free_completed_exception(e);
955 return 0;
956 }
957
958 /*
959 * The chunk may be either at the beginning or the end of a
960 * group of consecutive chunks - never in the middle. We are
961 * removing chunks in the opposite order to that in which they
962 * were added, so this should always be true.
963 * Decrement the consecutive chunk counter and adjust the
964 * starting point if necessary.
965 */
966 if (old_chunk == e->old_chunk) {
967 e->old_chunk++;
968 e->new_chunk++;
969 } else if (old_chunk != e->old_chunk +
970 dm_consecutive_chunk_count(e)) {
971 DMERR("Attempt to merge block %llu from the middle of a chunk range [%llu - %llu]",
972 (unsigned long long)old_chunk,
973 (unsigned long long)e->old_chunk,
974 (unsigned long long)
975 e->old_chunk + dm_consecutive_chunk_count(e));
976 return -EINVAL;
977 }
978
979 dm_consecutive_chunk_count_dec(e);
980
981 return 0;
982}
983
984static void flush_bios(struct bio *bio);
985
986static int remove_single_exception_chunk(struct dm_snapshot *s)
987{
988 struct bio *b = NULL;
989 int r;
990 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
991
992 down_write(&s->lock);
993
994 /*
995 * Process chunks (and associated exceptions) in reverse order
996 * so that dm_consecutive_chunk_count_dec() accounting works.
997 */
998 do {
999 r = __remove_single_exception_chunk(s, old_chunk);
1000 if (r)
1001 goto out;
1002 } while (old_chunk-- > s->first_merging_chunk);
1003
1004 b = __release_queued_bios_after_merge(s);
1005
1006out:
1007 up_write(&s->lock);
1008 if (b)
1009 flush_bios(b);
1010
1011 return r;
1012}
1013
1014static int origin_write_extent(struct dm_snapshot *merging_snap,
1015 sector_t sector, unsigned int chunk_size);
1016
1017static void merge_callback(int read_err, unsigned long write_err,
1018 void *context);
1019
1020static uint64_t read_pending_exceptions_done_count(void)
1021{
1022 uint64_t pending_exceptions_done;
1023
1024 spin_lock(&_pending_exceptions_done_spinlock);
1025 pending_exceptions_done = _pending_exceptions_done_count;
1026 spin_unlock(&_pending_exceptions_done_spinlock);
1027
1028 return pending_exceptions_done;
1029}
1030
1031static void increment_pending_exceptions_done_count(void)
1032{
1033 spin_lock(&_pending_exceptions_done_spinlock);
1034 _pending_exceptions_done_count++;
1035 spin_unlock(&_pending_exceptions_done_spinlock);
1036
1037 wake_up_all(&_pending_exceptions_done);
1038}
1039
1040static void snapshot_merge_next_chunks(struct dm_snapshot *s)
1041{
1042 int i, linear_chunks;
1043 chunk_t old_chunk, new_chunk;
1044 struct dm_io_region src, dest;
1045 sector_t io_size;
1046 uint64_t previous_count;
1047
1048 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
1049 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
1050 goto shut;
1051
1052 /*
1053 * valid flag never changes during merge, so no lock required.
1054 */
1055 if (!s->valid) {
1056 DMERR("Snapshot is invalid: can't merge");
1057 goto shut;
1058 }
1059
1060 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
1061 &new_chunk);
1062 if (linear_chunks <= 0) {
1063 if (linear_chunks < 0) {
1064 DMERR("Read error in exception store: shutting down merge");
1065 down_write(&s->lock);
1066 s->merge_failed = true;
1067 up_write(&s->lock);
1068 }
1069 goto shut;
1070 }
1071
1072 /* Adjust old_chunk and new_chunk to reflect start of linear region */
1073 old_chunk = old_chunk + 1 - linear_chunks;
1074 new_chunk = new_chunk + 1 - linear_chunks;
1075
1076 /*
1077 * Use one (potentially large) I/O to copy all 'linear_chunks'
1078 * from the exception store to the origin
1079 */
1080 io_size = linear_chunks * s->store->chunk_size;
1081
1082 dest.bdev = s->origin->bdev;
1083 dest.sector = chunk_to_sector(s->store, old_chunk);
1084 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1085
1086 src.bdev = s->cow->bdev;
1087 src.sector = chunk_to_sector(s->store, new_chunk);
1088 src.count = dest.count;
1089
1090 /*
1091 * Reallocate any exceptions needed in other snapshots then
1092 * wait for the pending exceptions to complete.
1093 * Each time any pending exception (globally on the system)
1094 * completes we are woken and repeat the process to find out
1095 * if we can proceed. While this may not seem a particularly
1096 * efficient algorithm, it is not expected to have any
1097 * significant impact on performance.
1098 */
1099 previous_count = read_pending_exceptions_done_count();
1100 while (origin_write_extent(s, dest.sector, io_size)) {
1101 wait_event(_pending_exceptions_done,
1102 (read_pending_exceptions_done_count() !=
1103 previous_count));
1104 /* Retry after the wait, until all exceptions are done. */
1105 previous_count = read_pending_exceptions_done_count();
1106 }
1107
1108 down_write(&s->lock);
1109 s->first_merging_chunk = old_chunk;
1110 s->num_merging_chunks = linear_chunks;
1111 up_write(&s->lock);
1112
1113 /* Wait until writes to all 'linear_chunks' drain */
1114 for (i = 0; i < linear_chunks; i++)
1115 __check_for_conflicting_io(s, old_chunk + i);
1116
1117 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1118 return;
1119
1120shut:
1121 merge_shutdown(s);
1122}
1123
1124static void error_bios(struct bio *bio);
1125
1126static void merge_callback(int read_err, unsigned long write_err, void *context)
1127{
1128 struct dm_snapshot *s = context;
1129 struct bio *b = NULL;
1130
1131 if (read_err || write_err) {
1132 if (read_err)
1133 DMERR("Read error: shutting down merge.");
1134 else
1135 DMERR("Write error: shutting down merge.");
1136 goto shut;
1137 }
1138
1139 if (blkdev_issue_flush(s->origin->bdev) < 0) {
1140 DMERR("Flush after merge failed: shutting down merge");
1141 goto shut;
1142 }
1143
1144 if (s->store->type->commit_merge(s->store,
1145 s->num_merging_chunks) < 0) {
1146 DMERR("Write error in exception store: shutting down merge");
1147 goto shut;
1148 }
1149
1150 if (remove_single_exception_chunk(s) < 0)
1151 goto shut;
1152
1153 snapshot_merge_next_chunks(s);
1154
1155 return;
1156
1157shut:
1158 down_write(&s->lock);
1159 s->merge_failed = true;
1160 b = __release_queued_bios_after_merge(s);
1161 up_write(&s->lock);
1162 error_bios(b);
1163
1164 merge_shutdown(s);
1165}
1166
1167static void start_merge(struct dm_snapshot *s)
1168{
1169 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1170 snapshot_merge_next_chunks(s);
1171}
1172
1173/*
1174 * Stop the merging process and wait until it finishes.
1175 */
1176static void stop_merge(struct dm_snapshot *s)
1177{
1178 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1179 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1180 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1181}
1182
1183static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,
1184 struct dm_target *ti)
1185{
1186 int r;
1187 unsigned int argc;
1188 const char *arg_name;
1189
1190 static const struct dm_arg _args[] = {
1191 {0, 2, "Invalid number of feature arguments"},
1192 };
1193
1194 /*
1195 * No feature arguments supplied.
1196 */
1197 if (!as->argc)
1198 return 0;
1199
1200 r = dm_read_arg_group(_args, as, &argc, &ti->error);
1201 if (r)
1202 return -EINVAL;
1203
1204 while (argc && !r) {
1205 arg_name = dm_shift_arg(as);
1206 argc--;
1207
1208 if (!strcasecmp(arg_name, "discard_zeroes_cow"))
1209 s->discard_zeroes_cow = true;
1210
1211 else if (!strcasecmp(arg_name, "discard_passdown_origin"))
1212 s->discard_passdown_origin = true;
1213
1214 else {
1215 ti->error = "Unrecognised feature requested";
1216 r = -EINVAL;
1217 break;
1218 }
1219 }
1220
1221 if (!s->discard_zeroes_cow && s->discard_passdown_origin) {
1222 /*
1223 * TODO: really these are disjoint.. but ti->num_discard_bios
1224 * and dm_bio_get_target_bio_nr() require rigid constraints.
1225 */
1226 ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";
1227 r = -EINVAL;
1228 }
1229
1230 return r;
1231}
1232
1233/*
1234 * Construct a snapshot mapping:
1235 * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]
1236 */
1237static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1238{
1239 struct dm_snapshot *s;
1240 struct dm_arg_set as;
1241 int i;
1242 int r = -EINVAL;
1243 char *origin_path, *cow_path;
1244 unsigned int args_used, num_flush_bios = 1;
1245 blk_mode_t origin_mode = BLK_OPEN_READ;
1246
1247 if (argc < 4) {
1248 ti->error = "requires 4 or more arguments";
1249 r = -EINVAL;
1250 goto bad;
1251 }
1252
1253 if (dm_target_is_snapshot_merge(ti)) {
1254 num_flush_bios = 2;
1255 origin_mode = BLK_OPEN_WRITE;
1256 }
1257
1258 s = kzalloc(sizeof(*s), GFP_KERNEL);
1259 if (!s) {
1260 ti->error = "Cannot allocate private snapshot structure";
1261 r = -ENOMEM;
1262 goto bad;
1263 }
1264
1265 as.argc = argc;
1266 as.argv = argv;
1267 dm_consume_args(&as, 4);
1268 r = parse_snapshot_features(&as, s, ti);
1269 if (r)
1270 goto bad_features;
1271
1272 origin_path = argv[0];
1273 argv++;
1274 argc--;
1275
1276 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1277 if (r) {
1278 ti->error = "Cannot get origin device";
1279 goto bad_origin;
1280 }
1281
1282 cow_path = argv[0];
1283 argv++;
1284 argc--;
1285
1286 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1287 if (r) {
1288 ti->error = "Cannot get COW device";
1289 goto bad_cow;
1290 }
1291 if (s->cow->bdev && s->cow->bdev == s->origin->bdev) {
1292 ti->error = "COW device cannot be the same as origin device";
1293 r = -EINVAL;
1294 goto bad_store;
1295 }
1296
1297 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1298 if (r) {
1299 ti->error = "Couldn't create exception store";
1300 r = -EINVAL;
1301 goto bad_store;
1302 }
1303
1304 argv += args_used;
1305 argc -= args_used;
1306
1307 s->ti = ti;
1308 s->valid = 1;
1309 s->snapshot_overflowed = 0;
1310 s->active = 0;
1311 atomic_set(&s->pending_exceptions_count, 0);
1312 spin_lock_init(&s->pe_allocation_lock);
1313 s->exception_start_sequence = 0;
1314 s->exception_complete_sequence = 0;
1315 s->out_of_order_tree = RB_ROOT;
1316 init_rwsem(&s->lock);
1317 INIT_LIST_HEAD(&s->list);
1318 spin_lock_init(&s->pe_lock);
1319 s->state_bits = 0;
1320 s->merge_failed = false;
1321 s->first_merging_chunk = 0;
1322 s->num_merging_chunks = 0;
1323 bio_list_init(&s->bios_queued_during_merge);
1324
1325 /* Allocate hash table for COW data */
1326 if (init_hash_tables(s)) {
1327 ti->error = "Unable to allocate hash table space";
1328 r = -ENOMEM;
1329 goto bad_hash_tables;
1330 }
1331
1332 init_waitqueue_head(&s->in_progress_wait);
1333
1334 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1335 if (IS_ERR(s->kcopyd_client)) {
1336 r = PTR_ERR(s->kcopyd_client);
1337 ti->error = "Could not create kcopyd client";
1338 goto bad_kcopyd;
1339 }
1340
1341 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
1342 if (r) {
1343 ti->error = "Could not allocate mempool for pending exceptions";
1344 goto bad_pending_pool;
1345 }
1346
1347 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1348 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1349
1350 spin_lock_init(&s->tracked_chunk_lock);
1351
1352 ti->private = s;
1353 ti->num_flush_bios = num_flush_bios;
1354 if (s->discard_zeroes_cow)
1355 ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
1356 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1357
1358 /* Add snapshot to the list of snapshots for this origin */
1359 /* Exceptions aren't triggered till snapshot_resume() is called */
1360 r = register_snapshot(s);
1361 if (r == -ENOMEM) {
1362 ti->error = "Snapshot origin struct allocation failed";
1363 goto bad_load_and_register;
1364 } else if (r < 0) {
1365 /* invalid handover, register_snapshot has set ti->error */
1366 goto bad_load_and_register;
1367 }
1368
1369 /*
1370 * Metadata must only be loaded into one table at once, so skip this
1371 * if metadata will be handed over during resume.
1372 * Chunk size will be set during the handover - set it to zero to
1373 * ensure it's ignored.
1374 */
1375 if (r > 0) {
1376 s->store->chunk_size = 0;
1377 return 0;
1378 }
1379
1380 r = s->store->type->read_metadata(s->store, dm_add_exception,
1381 (void *)s);
1382 if (r < 0) {
1383 ti->error = "Failed to read snapshot metadata";
1384 goto bad_read_metadata;
1385 } else if (r > 0) {
1386 s->valid = 0;
1387 DMWARN("Snapshot is marked invalid.");
1388 }
1389
1390 if (!s->store->chunk_size) {
1391 ti->error = "Chunk size not set";
1392 r = -EINVAL;
1393 goto bad_read_metadata;
1394 }
1395
1396 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1397 if (r)
1398 goto bad_read_metadata;
1399
1400 return 0;
1401
1402bad_read_metadata:
1403 unregister_snapshot(s);
1404bad_load_and_register:
1405 mempool_exit(&s->pending_pool);
1406bad_pending_pool:
1407 dm_kcopyd_client_destroy(s->kcopyd_client);
1408bad_kcopyd:
1409 dm_exception_table_exit(&s->pending, pending_cache);
1410 dm_exception_table_exit(&s->complete, exception_cache);
1411bad_hash_tables:
1412 dm_exception_store_destroy(s->store);
1413bad_store:
1414 dm_put_device(ti, s->cow);
1415bad_cow:
1416 dm_put_device(ti, s->origin);
1417bad_origin:
1418bad_features:
1419 kfree(s);
1420bad:
1421 return r;
1422}
1423
1424static void __free_exceptions(struct dm_snapshot *s)
1425{
1426 dm_kcopyd_client_destroy(s->kcopyd_client);
1427 s->kcopyd_client = NULL;
1428
1429 dm_exception_table_exit(&s->pending, pending_cache);
1430 dm_exception_table_exit(&s->complete, exception_cache);
1431}
1432
1433static void __handover_exceptions(struct dm_snapshot *snap_src,
1434 struct dm_snapshot *snap_dest)
1435{
1436 union {
1437 struct dm_exception_table table_swap;
1438 struct dm_exception_store *store_swap;
1439 } u;
1440
1441 /*
1442 * Swap all snapshot context information between the two instances.
1443 */
1444 u.table_swap = snap_dest->complete;
1445 snap_dest->complete = snap_src->complete;
1446 snap_src->complete = u.table_swap;
1447
1448 u.store_swap = snap_dest->store;
1449 snap_dest->store = snap_src->store;
1450 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1451 snap_src->store = u.store_swap;
1452
1453 snap_dest->store->snap = snap_dest;
1454 snap_src->store->snap = snap_src;
1455
1456 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1457 snap_dest->valid = snap_src->valid;
1458 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1459
1460 /*
1461 * Set source invalid to ensure it receives no further I/O.
1462 */
1463 snap_src->valid = 0;
1464}
1465
1466static void snapshot_dtr(struct dm_target *ti)
1467{
1468#ifdef CONFIG_DM_DEBUG
1469 int i;
1470#endif
1471 struct dm_snapshot *s = ti->private;
1472 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1473
1474 down_read(&_origins_lock);
1475 /* Check whether exception handover must be cancelled */
1476 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1477 if (snap_src && snap_dest && (s == snap_src)) {
1478 down_write(&snap_dest->lock);
1479 snap_dest->valid = 0;
1480 up_write(&snap_dest->lock);
1481 DMERR("Cancelling snapshot handover.");
1482 }
1483 up_read(&_origins_lock);
1484
1485 if (dm_target_is_snapshot_merge(ti))
1486 stop_merge(s);
1487
1488 /* Prevent further origin writes from using this snapshot. */
1489 /* After this returns there can be no new kcopyd jobs. */
1490 unregister_snapshot(s);
1491
1492 while (atomic_read(&s->pending_exceptions_count))
1493 fsleep(1000);
1494 /*
1495 * Ensure instructions in mempool_exit aren't reordered
1496 * before atomic_read.
1497 */
1498 smp_mb();
1499
1500#ifdef CONFIG_DM_DEBUG
1501 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1502 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1503#endif
1504
1505 __free_exceptions(s);
1506
1507 mempool_exit(&s->pending_pool);
1508
1509 dm_exception_store_destroy(s->store);
1510
1511 dm_put_device(ti, s->cow);
1512
1513 dm_put_device(ti, s->origin);
1514
1515 WARN_ON(s->in_progress);
1516
1517 kfree(s);
1518}
1519
1520static void account_start_copy(struct dm_snapshot *s)
1521{
1522 spin_lock(&s->in_progress_wait.lock);
1523 s->in_progress++;
1524 spin_unlock(&s->in_progress_wait.lock);
1525}
1526
1527static void account_end_copy(struct dm_snapshot *s)
1528{
1529 spin_lock(&s->in_progress_wait.lock);
1530 BUG_ON(!s->in_progress);
1531 s->in_progress--;
1532 if (likely(s->in_progress <= cow_threshold) &&
1533 unlikely(waitqueue_active(&s->in_progress_wait)))
1534 wake_up_locked(&s->in_progress_wait);
1535 spin_unlock(&s->in_progress_wait.lock);
1536}
1537
1538static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
1539{
1540 if (unlikely(s->in_progress > cow_threshold)) {
1541 spin_lock(&s->in_progress_wait.lock);
1542 if (likely(s->in_progress > cow_threshold)) {
1543 /*
1544 * NOTE: this throttle doesn't account for whether
1545 * the caller is servicing an IO that will trigger a COW
1546 * so excess throttling may result for chunks not required
1547 * to be COW'd. But if cow_threshold was reached, extra
1548 * throttling is unlikely to negatively impact performance.
1549 */
1550 DECLARE_WAITQUEUE(wait, current);
1551
1552 __add_wait_queue(&s->in_progress_wait, &wait);
1553 __set_current_state(TASK_UNINTERRUPTIBLE);
1554 spin_unlock(&s->in_progress_wait.lock);
1555 if (unlock_origins)
1556 up_read(&_origins_lock);
1557 io_schedule();
1558 remove_wait_queue(&s->in_progress_wait, &wait);
1559 return false;
1560 }
1561 spin_unlock(&s->in_progress_wait.lock);
1562 }
1563 return true;
1564}
1565
1566/*
1567 * Flush a list of buffers.
1568 */
1569static void flush_bios(struct bio *bio)
1570{
1571 struct bio *n;
1572
1573 while (bio) {
1574 n = bio->bi_next;
1575 bio->bi_next = NULL;
1576 submit_bio_noacct(bio);
1577 bio = n;
1578 }
1579}
1580
1581static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
1582
1583/*
1584 * Flush a list of buffers.
1585 */
1586static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1587{
1588 struct bio *n;
1589 int r;
1590
1591 while (bio) {
1592 n = bio->bi_next;
1593 bio->bi_next = NULL;
1594 r = do_origin(s->origin, bio, false);
1595 if (r == DM_MAPIO_REMAPPED)
1596 submit_bio_noacct(bio);
1597 bio = n;
1598 }
1599}
1600
1601/*
1602 * Error a list of buffers.
1603 */
1604static void error_bios(struct bio *bio)
1605{
1606 struct bio *n;
1607
1608 while (bio) {
1609 n = bio->bi_next;
1610 bio->bi_next = NULL;
1611 bio_io_error(bio);
1612 bio = n;
1613 }
1614}
1615
1616static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1617{
1618 if (!s->valid)
1619 return;
1620
1621 if (err == -EIO)
1622 DMERR("Invalidating snapshot: Error reading/writing.");
1623 else if (err == -ENOMEM)
1624 DMERR("Invalidating snapshot: Unable to allocate exception.");
1625
1626 if (s->store->type->drop_snapshot)
1627 s->store->type->drop_snapshot(s->store);
1628
1629 s->valid = 0;
1630
1631 dm_table_event(s->ti->table);
1632}
1633
1634static void invalidate_snapshot(struct dm_snapshot *s, int err)
1635{
1636 down_write(&s->lock);
1637 __invalidate_snapshot(s, err);
1638 up_write(&s->lock);
1639}
1640
1641static void pending_complete(void *context, int success)
1642{
1643 struct dm_snap_pending_exception *pe = context;
1644 struct dm_exception *e;
1645 struct dm_snapshot *s = pe->snap;
1646 struct bio *origin_bios = NULL;
1647 struct bio *snapshot_bios = NULL;
1648 struct bio *full_bio = NULL;
1649 struct dm_exception_table_lock lock;
1650 int error = 0;
1651
1652 dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);
1653
1654 if (!success) {
1655 /* Read/write error - snapshot is unusable */
1656 invalidate_snapshot(s, -EIO);
1657 error = 1;
1658
1659 dm_exception_table_lock(&lock);
1660 goto out;
1661 }
1662
1663 e = alloc_completed_exception(GFP_NOIO);
1664 if (!e) {
1665 invalidate_snapshot(s, -ENOMEM);
1666 error = 1;
1667
1668 dm_exception_table_lock(&lock);
1669 goto out;
1670 }
1671 *e = pe->e;
1672
1673 down_read(&s->lock);
1674 dm_exception_table_lock(&lock);
1675 if (!s->valid) {
1676 up_read(&s->lock);
1677 free_completed_exception(e);
1678 error = 1;
1679
1680 goto out;
1681 }
1682
1683 /*
1684 * Add a proper exception. After inserting the completed exception all
1685 * subsequent snapshot reads to this chunk will be redirected to the
1686 * COW device. This ensures that we do not starve. Moreover, as long
1687 * as the pending exception exists, neither origin writes nor snapshot
1688 * merging can overwrite the chunk in origin.
1689 */
1690 dm_insert_exception(&s->complete, e);
1691 up_read(&s->lock);
1692
1693 /* Wait for conflicting reads to drain */
1694 if (__chunk_is_tracked(s, pe->e.old_chunk)) {
1695 dm_exception_table_unlock(&lock);
1696 __check_for_conflicting_io(s, pe->e.old_chunk);
1697 dm_exception_table_lock(&lock);
1698 }
1699
1700out:
1701 /* Remove the in-flight exception from the list */
1702 dm_remove_exception(&pe->e);
1703
1704 dm_exception_table_unlock(&lock);
1705
1706 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1707 origin_bios = bio_list_get(&pe->origin_bios);
1708 full_bio = pe->full_bio;
1709 if (full_bio)
1710 full_bio->bi_end_io = pe->full_bio_end_io;
1711 increment_pending_exceptions_done_count();
1712
1713 /* Submit any pending write bios */
1714 if (error) {
1715 if (full_bio)
1716 bio_io_error(full_bio);
1717 error_bios(snapshot_bios);
1718 } else {
1719 if (full_bio)
1720 bio_endio(full_bio);
1721 flush_bios(snapshot_bios);
1722 }
1723
1724 retry_origin_bios(s, origin_bios);
1725
1726 free_pending_exception(pe);
1727}
1728
1729static void complete_exception(struct dm_snap_pending_exception *pe)
1730{
1731 struct dm_snapshot *s = pe->snap;
1732
1733 /* Update the metadata if we are persistent */
1734 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1735 pending_complete, pe);
1736}
1737
1738/*
1739 * Called when the copy I/O has finished. kcopyd actually runs
1740 * this code so don't block.
1741 */
1742static void copy_callback(int read_err, unsigned long write_err, void *context)
1743{
1744 struct dm_snap_pending_exception *pe = context;
1745 struct dm_snapshot *s = pe->snap;
1746
1747 pe->copy_error = read_err || write_err;
1748
1749 if (pe->exception_sequence == s->exception_complete_sequence) {
1750 struct rb_node *next;
1751
1752 s->exception_complete_sequence++;
1753 complete_exception(pe);
1754
1755 next = rb_first(&s->out_of_order_tree);
1756 while (next) {
1757 pe = rb_entry(next, struct dm_snap_pending_exception,
1758 out_of_order_node);
1759 if (pe->exception_sequence != s->exception_complete_sequence)
1760 break;
1761 next = rb_next(next);
1762 s->exception_complete_sequence++;
1763 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
1764 complete_exception(pe);
1765 cond_resched();
1766 }
1767 } else {
1768 struct rb_node *parent = NULL;
1769 struct rb_node **p = &s->out_of_order_tree.rb_node;
1770 struct dm_snap_pending_exception *pe2;
1771
1772 while (*p) {
1773 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
1774 parent = *p;
1775
1776 BUG_ON(pe->exception_sequence == pe2->exception_sequence);
1777 if (pe->exception_sequence < pe2->exception_sequence)
1778 p = &((*p)->rb_left);
1779 else
1780 p = &((*p)->rb_right);
1781 }
1782
1783 rb_link_node(&pe->out_of_order_node, parent, p);
1784 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
1785 }
1786 account_end_copy(s);
1787}
1788
1789/*
1790 * Dispatches the copy operation to kcopyd.
1791 */
1792static void start_copy(struct dm_snap_pending_exception *pe)
1793{
1794 struct dm_snapshot *s = pe->snap;
1795 struct dm_io_region src, dest;
1796 struct block_device *bdev = s->origin->bdev;
1797 sector_t dev_size;
1798
1799 dev_size = get_dev_size(bdev);
1800
1801 src.bdev = bdev;
1802 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1803 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1804
1805 dest.bdev = s->cow->bdev;
1806 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1807 dest.count = src.count;
1808
1809 /* Hand over to kcopyd */
1810 account_start_copy(s);
1811 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1812}
1813
1814static void full_bio_end_io(struct bio *bio)
1815{
1816 void *callback_data = bio->bi_private;
1817
1818 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
1819}
1820
1821static void start_full_bio(struct dm_snap_pending_exception *pe,
1822 struct bio *bio)
1823{
1824 struct dm_snapshot *s = pe->snap;
1825 void *callback_data;
1826
1827 pe->full_bio = bio;
1828 pe->full_bio_end_io = bio->bi_end_io;
1829
1830 account_start_copy(s);
1831 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1832 copy_callback, pe);
1833
1834 bio->bi_end_io = full_bio_end_io;
1835 bio->bi_private = callback_data;
1836
1837 submit_bio_noacct(bio);
1838}
1839
1840static struct dm_snap_pending_exception *
1841__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1842{
1843 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1844
1845 if (!e)
1846 return NULL;
1847
1848 return container_of(e, struct dm_snap_pending_exception, e);
1849}
1850
1851/*
1852 * Inserts a pending exception into the pending table.
1853 *
1854 * NOTE: a write lock must be held on the chunk's pending exception table slot
1855 * before calling this.
1856 */
1857static struct dm_snap_pending_exception *
1858__insert_pending_exception(struct dm_snapshot *s,
1859 struct dm_snap_pending_exception *pe, chunk_t chunk)
1860{
1861 pe->e.old_chunk = chunk;
1862 bio_list_init(&pe->origin_bios);
1863 bio_list_init(&pe->snapshot_bios);
1864 pe->started = 0;
1865 pe->full_bio = NULL;
1866
1867 spin_lock(&s->pe_allocation_lock);
1868 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1869 spin_unlock(&s->pe_allocation_lock);
1870 free_pending_exception(pe);
1871 return NULL;
1872 }
1873
1874 pe->exception_sequence = s->exception_start_sequence++;
1875 spin_unlock(&s->pe_allocation_lock);
1876
1877 dm_insert_exception(&s->pending, &pe->e);
1878
1879 return pe;
1880}
1881
1882/*
1883 * Looks to see if this snapshot already has a pending exception
1884 * for this chunk, otherwise it allocates a new one and inserts
1885 * it into the pending table.
1886 *
1887 * NOTE: a write lock must be held on the chunk's pending exception table slot
1888 * before calling this.
1889 */
1890static struct dm_snap_pending_exception *
1891__find_pending_exception(struct dm_snapshot *s,
1892 struct dm_snap_pending_exception *pe, chunk_t chunk)
1893{
1894 struct dm_snap_pending_exception *pe2;
1895
1896 pe2 = __lookup_pending_exception(s, chunk);
1897 if (pe2) {
1898 free_pending_exception(pe);
1899 return pe2;
1900 }
1901
1902 return __insert_pending_exception(s, pe, chunk);
1903}
1904
1905static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1906 struct bio *bio, chunk_t chunk)
1907{
1908 bio_set_dev(bio, s->cow->bdev);
1909 bio->bi_iter.bi_sector =
1910 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1911 (chunk - e->old_chunk)) +
1912 (bio->bi_iter.bi_sector & s->store->chunk_mask);
1913}
1914
1915static void zero_callback(int read_err, unsigned long write_err, void *context)
1916{
1917 struct bio *bio = context;
1918 struct dm_snapshot *s = bio->bi_private;
1919
1920 account_end_copy(s);
1921 bio->bi_status = write_err ? BLK_STS_IOERR : 0;
1922 bio_endio(bio);
1923}
1924
1925static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
1926 struct bio *bio, chunk_t chunk)
1927{
1928 struct dm_io_region dest;
1929
1930 dest.bdev = s->cow->bdev;
1931 dest.sector = bio->bi_iter.bi_sector;
1932 dest.count = s->store->chunk_size;
1933
1934 account_start_copy(s);
1935 WARN_ON_ONCE(bio->bi_private);
1936 bio->bi_private = s;
1937 dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
1938}
1939
1940static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)
1941{
1942 return bio->bi_iter.bi_size ==
1943 (s->store->chunk_size << SECTOR_SHIFT);
1944}
1945
1946static int snapshot_map(struct dm_target *ti, struct bio *bio)
1947{
1948 struct dm_exception *e;
1949 struct dm_snapshot *s = ti->private;
1950 int r = DM_MAPIO_REMAPPED;
1951 chunk_t chunk;
1952 struct dm_snap_pending_exception *pe = NULL;
1953 struct dm_exception_table_lock lock;
1954
1955 init_tracked_chunk(bio);
1956
1957 if (bio->bi_opf & REQ_PREFLUSH) {
1958 bio_set_dev(bio, s->cow->bdev);
1959 return DM_MAPIO_REMAPPED;
1960 }
1961
1962 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1963 dm_exception_table_lock_init(s, chunk, &lock);
1964
1965 /* Full snapshots are not usable */
1966 /* To get here the table must be live so s->active is always set. */
1967 if (!s->valid)
1968 return DM_MAPIO_KILL;
1969
1970 if (bio_data_dir(bio) == WRITE) {
1971 while (unlikely(!wait_for_in_progress(s, false)))
1972 ; /* wait_for_in_progress() has slept */
1973 }
1974
1975 down_read(&s->lock);
1976 dm_exception_table_lock(&lock);
1977
1978 if (!s->valid || (unlikely(s->snapshot_overflowed) &&
1979 bio_data_dir(bio) == WRITE)) {
1980 r = DM_MAPIO_KILL;
1981 goto out_unlock;
1982 }
1983
1984 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
1985 if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {
1986 /*
1987 * passdown discard to origin (without triggering
1988 * snapshot exceptions via do_origin; doing so would
1989 * defeat the goal of freeing space in origin that is
1990 * implied by the "discard_passdown_origin" feature)
1991 */
1992 bio_set_dev(bio, s->origin->bdev);
1993 track_chunk(s, bio, chunk);
1994 goto out_unlock;
1995 }
1996 /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */
1997 }
1998
1999 /* If the block is already remapped - use that, else remap it */
2000 e = dm_lookup_exception(&s->complete, chunk);
2001 if (e) {
2002 remap_exception(s, e, bio, chunk);
2003 if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
2004 io_overlaps_chunk(s, bio)) {
2005 dm_exception_table_unlock(&lock);
2006 up_read(&s->lock);
2007 zero_exception(s, e, bio, chunk);
2008 r = DM_MAPIO_SUBMITTED; /* discard is not issued */
2009 goto out;
2010 }
2011 goto out_unlock;
2012 }
2013
2014 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2015 /*
2016 * If no exception exists, complete discard immediately
2017 * otherwise it'll trigger copy-out.
2018 */
2019 bio_endio(bio);
2020 r = DM_MAPIO_SUBMITTED;
2021 goto out_unlock;
2022 }
2023
2024 /*
2025 * Write to snapshot - higher level takes care of RW/RO
2026 * flags so we should only get this if we are
2027 * writable.
2028 */
2029 if (bio_data_dir(bio) == WRITE) {
2030 pe = __lookup_pending_exception(s, chunk);
2031 if (!pe) {
2032 dm_exception_table_unlock(&lock);
2033 pe = alloc_pending_exception(s);
2034 dm_exception_table_lock(&lock);
2035
2036 e = dm_lookup_exception(&s->complete, chunk);
2037 if (e) {
2038 free_pending_exception(pe);
2039 remap_exception(s, e, bio, chunk);
2040 goto out_unlock;
2041 }
2042
2043 pe = __find_pending_exception(s, pe, chunk);
2044 if (!pe) {
2045 dm_exception_table_unlock(&lock);
2046 up_read(&s->lock);
2047
2048 down_write(&s->lock);
2049
2050 if (s->store->userspace_supports_overflow) {
2051 if (s->valid && !s->snapshot_overflowed) {
2052 s->snapshot_overflowed = 1;
2053 DMERR("Snapshot overflowed: Unable to allocate exception.");
2054 }
2055 } else
2056 __invalidate_snapshot(s, -ENOMEM);
2057 up_write(&s->lock);
2058
2059 r = DM_MAPIO_KILL;
2060 goto out;
2061 }
2062 }
2063
2064 remap_exception(s, &pe->e, bio, chunk);
2065
2066 r = DM_MAPIO_SUBMITTED;
2067
2068 if (!pe->started && io_overlaps_chunk(s, bio)) {
2069 pe->started = 1;
2070
2071 dm_exception_table_unlock(&lock);
2072 up_read(&s->lock);
2073
2074 start_full_bio(pe, bio);
2075 goto out;
2076 }
2077
2078 bio_list_add(&pe->snapshot_bios, bio);
2079
2080 if (!pe->started) {
2081 /* this is protected by the exception table lock */
2082 pe->started = 1;
2083
2084 dm_exception_table_unlock(&lock);
2085 up_read(&s->lock);
2086
2087 start_copy(pe);
2088 goto out;
2089 }
2090 } else {
2091 bio_set_dev(bio, s->origin->bdev);
2092 track_chunk(s, bio, chunk);
2093 }
2094
2095out_unlock:
2096 dm_exception_table_unlock(&lock);
2097 up_read(&s->lock);
2098out:
2099 return r;
2100}
2101
2102/*
2103 * A snapshot-merge target behaves like a combination of a snapshot
2104 * target and a snapshot-origin target. It only generates new
2105 * exceptions in other snapshots and not in the one that is being
2106 * merged.
2107 *
2108 * For each chunk, if there is an existing exception, it is used to
2109 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
2110 * which in turn might generate exceptions in other snapshots.
2111 * If merging is currently taking place on the chunk in question, the
2112 * I/O is deferred by adding it to s->bios_queued_during_merge.
2113 */
2114static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
2115{
2116 struct dm_exception *e;
2117 struct dm_snapshot *s = ti->private;
2118 int r = DM_MAPIO_REMAPPED;
2119 chunk_t chunk;
2120
2121 init_tracked_chunk(bio);
2122
2123 if (bio->bi_opf & REQ_PREFLUSH) {
2124 if (!dm_bio_get_target_bio_nr(bio))
2125 bio_set_dev(bio, s->origin->bdev);
2126 else
2127 bio_set_dev(bio, s->cow->bdev);
2128 return DM_MAPIO_REMAPPED;
2129 }
2130
2131 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2132 /* Once merging, discards no longer effect change */
2133 bio_endio(bio);
2134 return DM_MAPIO_SUBMITTED;
2135 }
2136
2137 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
2138
2139 down_write(&s->lock);
2140
2141 /* Full merging snapshots are redirected to the origin */
2142 if (!s->valid)
2143 goto redirect_to_origin;
2144
2145 /* If the block is already remapped - use that */
2146 e = dm_lookup_exception(&s->complete, chunk);
2147 if (e) {
2148 /* Queue writes overlapping with chunks being merged */
2149 if (bio_data_dir(bio) == WRITE &&
2150 chunk >= s->first_merging_chunk &&
2151 chunk < (s->first_merging_chunk +
2152 s->num_merging_chunks)) {
2153 bio_set_dev(bio, s->origin->bdev);
2154 bio_list_add(&s->bios_queued_during_merge, bio);
2155 r = DM_MAPIO_SUBMITTED;
2156 goto out_unlock;
2157 }
2158
2159 remap_exception(s, e, bio, chunk);
2160
2161 if (bio_data_dir(bio) == WRITE)
2162 track_chunk(s, bio, chunk);
2163 goto out_unlock;
2164 }
2165
2166redirect_to_origin:
2167 bio_set_dev(bio, s->origin->bdev);
2168
2169 if (bio_data_dir(bio) == WRITE) {
2170 up_write(&s->lock);
2171 return do_origin(s->origin, bio, false);
2172 }
2173
2174out_unlock:
2175 up_write(&s->lock);
2176
2177 return r;
2178}
2179
2180static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
2181 blk_status_t *error)
2182{
2183 struct dm_snapshot *s = ti->private;
2184
2185 if (is_bio_tracked(bio))
2186 stop_tracking_chunk(s, bio);
2187
2188 return DM_ENDIO_DONE;
2189}
2190
2191static void snapshot_merge_presuspend(struct dm_target *ti)
2192{
2193 struct dm_snapshot *s = ti->private;
2194
2195 stop_merge(s);
2196}
2197
2198static int snapshot_preresume(struct dm_target *ti)
2199{
2200 int r = 0;
2201 struct dm_snapshot *s = ti->private;
2202 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2203
2204 down_read(&_origins_lock);
2205 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2206 if (snap_src && snap_dest) {
2207 down_read(&snap_src->lock);
2208 if (s == snap_src) {
2209 DMERR("Unable to resume snapshot source until handover completes.");
2210 r = -EINVAL;
2211 } else if (!dm_suspended(snap_src->ti)) {
2212 DMERR("Unable to perform snapshot handover until source is suspended.");
2213 r = -EINVAL;
2214 }
2215 up_read(&snap_src->lock);
2216 }
2217 up_read(&_origins_lock);
2218
2219 return r;
2220}
2221
2222static void snapshot_resume(struct dm_target *ti)
2223{
2224 struct dm_snapshot *s = ti->private;
2225 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
2226 struct dm_origin *o;
2227 struct mapped_device *origin_md = NULL;
2228 bool must_restart_merging = false;
2229
2230 down_read(&_origins_lock);
2231
2232 o = __lookup_dm_origin(s->origin->bdev);
2233 if (o)
2234 origin_md = dm_table_get_md(o->ti->table);
2235 if (!origin_md) {
2236 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
2237 if (snap_merging)
2238 origin_md = dm_table_get_md(snap_merging->ti->table);
2239 }
2240 if (origin_md == dm_table_get_md(ti->table))
2241 origin_md = NULL;
2242 if (origin_md) {
2243 if (dm_hold(origin_md))
2244 origin_md = NULL;
2245 }
2246
2247 up_read(&_origins_lock);
2248
2249 if (origin_md) {
2250 dm_internal_suspend_fast(origin_md);
2251 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
2252 must_restart_merging = true;
2253 stop_merge(snap_merging);
2254 }
2255 }
2256
2257 down_read(&_origins_lock);
2258
2259 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2260 if (snap_src && snap_dest) {
2261 down_write(&snap_src->lock);
2262 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
2263 __handover_exceptions(snap_src, snap_dest);
2264 up_write(&snap_dest->lock);
2265 up_write(&snap_src->lock);
2266 }
2267
2268 up_read(&_origins_lock);
2269
2270 if (origin_md) {
2271 if (must_restart_merging)
2272 start_merge(snap_merging);
2273 dm_internal_resume_fast(origin_md);
2274 dm_put(origin_md);
2275 }
2276
2277 /* Now we have correct chunk size, reregister */
2278 reregister_snapshot(s);
2279
2280 down_write(&s->lock);
2281 s->active = 1;
2282 up_write(&s->lock);
2283}
2284
2285static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
2286{
2287 uint32_t min_chunksize;
2288
2289 down_read(&_origins_lock);
2290 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
2291 up_read(&_origins_lock);
2292
2293 return min_chunksize;
2294}
2295
2296static void snapshot_merge_resume(struct dm_target *ti)
2297{
2298 struct dm_snapshot *s = ti->private;
2299
2300 /*
2301 * Handover exceptions from existing snapshot.
2302 */
2303 snapshot_resume(ti);
2304
2305 /*
2306 * snapshot-merge acts as an origin, so set ti->max_io_len
2307 */
2308 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
2309
2310 start_merge(s);
2311}
2312
2313static void snapshot_status(struct dm_target *ti, status_type_t type,
2314 unsigned int status_flags, char *result, unsigned int maxlen)
2315{
2316 unsigned int sz = 0;
2317 struct dm_snapshot *snap = ti->private;
2318 unsigned int num_features;
2319
2320 switch (type) {
2321 case STATUSTYPE_INFO:
2322
2323 down_write(&snap->lock);
2324
2325 if (!snap->valid)
2326 DMEMIT("Invalid");
2327 else if (snap->merge_failed)
2328 DMEMIT("Merge failed");
2329 else if (snap->snapshot_overflowed)
2330 DMEMIT("Overflow");
2331 else {
2332 if (snap->store->type->usage) {
2333 sector_t total_sectors, sectors_allocated,
2334 metadata_sectors;
2335 snap->store->type->usage(snap->store,
2336 &total_sectors,
2337 §ors_allocated,
2338 &metadata_sectors);
2339 DMEMIT("%llu/%llu %llu",
2340 (unsigned long long)sectors_allocated,
2341 (unsigned long long)total_sectors,
2342 (unsigned long long)metadata_sectors);
2343 } else
2344 DMEMIT("Unknown");
2345 }
2346
2347 up_write(&snap->lock);
2348
2349 break;
2350
2351 case STATUSTYPE_TABLE:
2352 /*
2353 * kdevname returns a static pointer so we need
2354 * to make private copies if the output is to
2355 * make sense.
2356 */
2357 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2358 sz += snap->store->type->status(snap->store, type, result + sz,
2359 maxlen - sz);
2360 num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;
2361 if (num_features) {
2362 DMEMIT(" %u", num_features);
2363 if (snap->discard_zeroes_cow)
2364 DMEMIT(" discard_zeroes_cow");
2365 if (snap->discard_passdown_origin)
2366 DMEMIT(" discard_passdown_origin");
2367 }
2368 break;
2369
2370 case STATUSTYPE_IMA:
2371 DMEMIT_TARGET_NAME_VERSION(ti->type);
2372 DMEMIT(",snap_origin_name=%s", snap->origin->name);
2373 DMEMIT(",snap_cow_name=%s", snap->cow->name);
2374 DMEMIT(",snap_valid=%c", snap->valid ? 'y' : 'n');
2375 DMEMIT(",snap_merge_failed=%c", snap->merge_failed ? 'y' : 'n');
2376 DMEMIT(",snapshot_overflowed=%c", snap->snapshot_overflowed ? 'y' : 'n');
2377 DMEMIT(";");
2378 break;
2379 }
2380}
2381
2382static int snapshot_iterate_devices(struct dm_target *ti,
2383 iterate_devices_callout_fn fn, void *data)
2384{
2385 struct dm_snapshot *snap = ti->private;
2386 int r;
2387
2388 r = fn(ti, snap->origin, 0, ti->len, data);
2389
2390 if (!r)
2391 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2392
2393 return r;
2394}
2395
2396static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
2397{
2398 struct dm_snapshot *snap = ti->private;
2399
2400 if (snap->discard_zeroes_cow) {
2401 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2402
2403 down_read(&_origins_lock);
2404
2405 (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);
2406 if (snap_src && snap_dest)
2407 snap = snap_src;
2408
2409 /* All discards are split on chunk_size boundary */
2410 limits->discard_granularity = snap->store->chunk_size;
2411 limits->max_discard_sectors = snap->store->chunk_size;
2412
2413 up_read(&_origins_lock);
2414 }
2415}
2416
2417/*
2418 *---------------------------------------------------------------
2419 * Origin methods
2420 *---------------------------------------------------------------
2421 */
2422/*
2423 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2424 * supplied bio was ignored. The caller may submit it immediately.
2425 * (No remapping actually occurs as the origin is always a direct linear
2426 * map.)
2427 *
2428 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2429 * and any supplied bio is added to a list to be submitted once all
2430 * the necessary exceptions exist.
2431 */
2432static int __origin_write(struct list_head *snapshots, sector_t sector,
2433 struct bio *bio)
2434{
2435 int r = DM_MAPIO_REMAPPED;
2436 struct dm_snapshot *snap;
2437 struct dm_exception *e;
2438 struct dm_snap_pending_exception *pe, *pe2;
2439 struct dm_snap_pending_exception *pe_to_start_now = NULL;
2440 struct dm_snap_pending_exception *pe_to_start_last = NULL;
2441 struct dm_exception_table_lock lock;
2442 chunk_t chunk;
2443
2444 /* Do all the snapshots on this origin */
2445 list_for_each_entry(snap, snapshots, list) {
2446 /*
2447 * Don't make new exceptions in a merging snapshot
2448 * because it has effectively been deleted
2449 */
2450 if (dm_target_is_snapshot_merge(snap->ti))
2451 continue;
2452
2453 /* Nothing to do if writing beyond end of snapshot */
2454 if (sector >= dm_table_get_size(snap->ti->table))
2455 continue;
2456
2457 /*
2458 * Remember, different snapshots can have
2459 * different chunk sizes.
2460 */
2461 chunk = sector_to_chunk(snap->store, sector);
2462 dm_exception_table_lock_init(snap, chunk, &lock);
2463
2464 down_read(&snap->lock);
2465 dm_exception_table_lock(&lock);
2466
2467 /* Only deal with valid and active snapshots */
2468 if (!snap->valid || !snap->active)
2469 goto next_snapshot;
2470
2471 pe = __lookup_pending_exception(snap, chunk);
2472 if (!pe) {
2473 /*
2474 * Check exception table to see if block is already
2475 * remapped in this snapshot and trigger an exception
2476 * if not.
2477 */
2478 e = dm_lookup_exception(&snap->complete, chunk);
2479 if (e)
2480 goto next_snapshot;
2481
2482 dm_exception_table_unlock(&lock);
2483 pe = alloc_pending_exception(snap);
2484 dm_exception_table_lock(&lock);
2485
2486 pe2 = __lookup_pending_exception(snap, chunk);
2487
2488 if (!pe2) {
2489 e = dm_lookup_exception(&snap->complete, chunk);
2490 if (e) {
2491 free_pending_exception(pe);
2492 goto next_snapshot;
2493 }
2494
2495 pe = __insert_pending_exception(snap, pe, chunk);
2496 if (!pe) {
2497 dm_exception_table_unlock(&lock);
2498 up_read(&snap->lock);
2499
2500 invalidate_snapshot(snap, -ENOMEM);
2501 continue;
2502 }
2503 } else {
2504 free_pending_exception(pe);
2505 pe = pe2;
2506 }
2507 }
2508
2509 r = DM_MAPIO_SUBMITTED;
2510
2511 /*
2512 * If an origin bio was supplied, queue it to wait for the
2513 * completion of this exception, and start this one last,
2514 * at the end of the function.
2515 */
2516 if (bio) {
2517 bio_list_add(&pe->origin_bios, bio);
2518 bio = NULL;
2519
2520 if (!pe->started) {
2521 pe->started = 1;
2522 pe_to_start_last = pe;
2523 }
2524 }
2525
2526 if (!pe->started) {
2527 pe->started = 1;
2528 pe_to_start_now = pe;
2529 }
2530
2531next_snapshot:
2532 dm_exception_table_unlock(&lock);
2533 up_read(&snap->lock);
2534
2535 if (pe_to_start_now) {
2536 start_copy(pe_to_start_now);
2537 pe_to_start_now = NULL;
2538 }
2539 }
2540
2541 /*
2542 * Submit the exception against which the bio is queued last,
2543 * to give the other exceptions a head start.
2544 */
2545 if (pe_to_start_last)
2546 start_copy(pe_to_start_last);
2547
2548 return r;
2549}
2550
2551/*
2552 * Called on a write from the origin driver.
2553 */
2554static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
2555{
2556 struct origin *o;
2557 int r = DM_MAPIO_REMAPPED;
2558
2559again:
2560 down_read(&_origins_lock);
2561 o = __lookup_origin(origin->bdev);
2562 if (o) {
2563 if (limit) {
2564 struct dm_snapshot *s;
2565
2566 list_for_each_entry(s, &o->snapshots, list)
2567 if (unlikely(!wait_for_in_progress(s, true)))
2568 goto again;
2569 }
2570
2571 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
2572 }
2573 up_read(&_origins_lock);
2574
2575 return r;
2576}
2577
2578/*
2579 * Trigger exceptions in all non-merging snapshots.
2580 *
2581 * The chunk size of the merging snapshot may be larger than the chunk
2582 * size of some other snapshot so we may need to reallocate multiple
2583 * chunks in other snapshots.
2584 *
2585 * We scan all the overlapping exceptions in the other snapshots.
2586 * Returns 1 if anything was reallocated and must be waited for,
2587 * otherwise returns 0.
2588 *
2589 * size must be a multiple of merging_snap's chunk_size.
2590 */
2591static int origin_write_extent(struct dm_snapshot *merging_snap,
2592 sector_t sector, unsigned int size)
2593{
2594 int must_wait = 0;
2595 sector_t n;
2596 struct origin *o;
2597
2598 /*
2599 * The origin's __minimum_chunk_size() got stored in max_io_len
2600 * by snapshot_merge_resume().
2601 */
2602 down_read(&_origins_lock);
2603 o = __lookup_origin(merging_snap->origin->bdev);
2604 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2605 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2606 DM_MAPIO_SUBMITTED)
2607 must_wait = 1;
2608 up_read(&_origins_lock);
2609
2610 return must_wait;
2611}
2612
2613/*
2614 * Origin: maps a linear range of a device, with hooks for snapshotting.
2615 */
2616
2617/*
2618 * Construct an origin mapping: <dev_path>
2619 * The context for an origin is merely a 'struct dm_dev *'
2620 * pointing to the real device.
2621 */
2622static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2623{
2624 int r;
2625 struct dm_origin *o;
2626
2627 if (argc != 1) {
2628 ti->error = "origin: incorrect number of arguments";
2629 return -EINVAL;
2630 }
2631
2632 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2633 if (!o) {
2634 ti->error = "Cannot allocate private origin structure";
2635 r = -ENOMEM;
2636 goto bad_alloc;
2637 }
2638
2639 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2640 if (r) {
2641 ti->error = "Cannot get target device";
2642 goto bad_open;
2643 }
2644
2645 o->ti = ti;
2646 ti->private = o;
2647 ti->num_flush_bios = 1;
2648
2649 return 0;
2650
2651bad_open:
2652 kfree(o);
2653bad_alloc:
2654 return r;
2655}
2656
2657static void origin_dtr(struct dm_target *ti)
2658{
2659 struct dm_origin *o = ti->private;
2660
2661 dm_put_device(ti, o->dev);
2662 kfree(o);
2663}
2664
2665static int origin_map(struct dm_target *ti, struct bio *bio)
2666{
2667 struct dm_origin *o = ti->private;
2668 unsigned int available_sectors;
2669
2670 bio_set_dev(bio, o->dev->bdev);
2671
2672 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2673 return DM_MAPIO_REMAPPED;
2674
2675 if (bio_data_dir(bio) != WRITE)
2676 return DM_MAPIO_REMAPPED;
2677
2678 available_sectors = o->split_boundary -
2679 ((unsigned int)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2680
2681 if (bio_sectors(bio) > available_sectors)
2682 dm_accept_partial_bio(bio, available_sectors);
2683
2684 /* Only tell snapshots if this is a write */
2685 return do_origin(o->dev, bio, true);
2686}
2687
2688/*
2689 * Set the target "max_io_len" field to the minimum of all the snapshots'
2690 * chunk sizes.
2691 */
2692static void origin_resume(struct dm_target *ti)
2693{
2694 struct dm_origin *o = ti->private;
2695
2696 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2697
2698 down_write(&_origins_lock);
2699 __insert_dm_origin(o);
2700 up_write(&_origins_lock);
2701}
2702
2703static void origin_postsuspend(struct dm_target *ti)
2704{
2705 struct dm_origin *o = ti->private;
2706
2707 down_write(&_origins_lock);
2708 __remove_dm_origin(o);
2709 up_write(&_origins_lock);
2710}
2711
2712static void origin_status(struct dm_target *ti, status_type_t type,
2713 unsigned int status_flags, char *result, unsigned int maxlen)
2714{
2715 struct dm_origin *o = ti->private;
2716
2717 switch (type) {
2718 case STATUSTYPE_INFO:
2719 result[0] = '\0';
2720 break;
2721
2722 case STATUSTYPE_TABLE:
2723 snprintf(result, maxlen, "%s", o->dev->name);
2724 break;
2725 case STATUSTYPE_IMA:
2726 result[0] = '\0';
2727 break;
2728 }
2729}
2730
2731static int origin_iterate_devices(struct dm_target *ti,
2732 iterate_devices_callout_fn fn, void *data)
2733{
2734 struct dm_origin *o = ti->private;
2735
2736 return fn(ti, o->dev, 0, ti->len, data);
2737}
2738
2739static struct target_type origin_target = {
2740 .name = "snapshot-origin",
2741 .version = {1, 9, 0},
2742 .module = THIS_MODULE,
2743 .ctr = origin_ctr,
2744 .dtr = origin_dtr,
2745 .map = origin_map,
2746 .resume = origin_resume,
2747 .postsuspend = origin_postsuspend,
2748 .status = origin_status,
2749 .iterate_devices = origin_iterate_devices,
2750};
2751
2752static struct target_type snapshot_target = {
2753 .name = "snapshot",
2754 .version = {1, 16, 0},
2755 .module = THIS_MODULE,
2756 .ctr = snapshot_ctr,
2757 .dtr = snapshot_dtr,
2758 .map = snapshot_map,
2759 .end_io = snapshot_end_io,
2760 .preresume = snapshot_preresume,
2761 .resume = snapshot_resume,
2762 .status = snapshot_status,
2763 .iterate_devices = snapshot_iterate_devices,
2764 .io_hints = snapshot_io_hints,
2765};
2766
2767static struct target_type merge_target = {
2768 .name = dm_snapshot_merge_target_name,
2769 .version = {1, 5, 0},
2770 .module = THIS_MODULE,
2771 .ctr = snapshot_ctr,
2772 .dtr = snapshot_dtr,
2773 .map = snapshot_merge_map,
2774 .end_io = snapshot_end_io,
2775 .presuspend = snapshot_merge_presuspend,
2776 .preresume = snapshot_preresume,
2777 .resume = snapshot_merge_resume,
2778 .status = snapshot_status,
2779 .iterate_devices = snapshot_iterate_devices,
2780 .io_hints = snapshot_io_hints,
2781};
2782
2783static int __init dm_snapshot_init(void)
2784{
2785 int r;
2786
2787 r = dm_exception_store_init();
2788 if (r) {
2789 DMERR("Failed to initialize exception stores");
2790 return r;
2791 }
2792
2793 r = init_origin_hash();
2794 if (r) {
2795 DMERR("init_origin_hash failed.");
2796 goto bad_origin_hash;
2797 }
2798
2799 exception_cache = KMEM_CACHE(dm_exception, 0);
2800 if (!exception_cache) {
2801 DMERR("Couldn't create exception cache.");
2802 r = -ENOMEM;
2803 goto bad_exception_cache;
2804 }
2805
2806 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2807 if (!pending_cache) {
2808 DMERR("Couldn't create pending cache.");
2809 r = -ENOMEM;
2810 goto bad_pending_cache;
2811 }
2812
2813 r = dm_register_target(&snapshot_target);
2814 if (r < 0)
2815 goto bad_register_snapshot_target;
2816
2817 r = dm_register_target(&origin_target);
2818 if (r < 0)
2819 goto bad_register_origin_target;
2820
2821 r = dm_register_target(&merge_target);
2822 if (r < 0)
2823 goto bad_register_merge_target;
2824
2825 return 0;
2826
2827bad_register_merge_target:
2828 dm_unregister_target(&origin_target);
2829bad_register_origin_target:
2830 dm_unregister_target(&snapshot_target);
2831bad_register_snapshot_target:
2832 kmem_cache_destroy(pending_cache);
2833bad_pending_cache:
2834 kmem_cache_destroy(exception_cache);
2835bad_exception_cache:
2836 exit_origin_hash();
2837bad_origin_hash:
2838 dm_exception_store_exit();
2839
2840 return r;
2841}
2842
2843static void __exit dm_snapshot_exit(void)
2844{
2845 dm_unregister_target(&snapshot_target);
2846 dm_unregister_target(&origin_target);
2847 dm_unregister_target(&merge_target);
2848
2849 exit_origin_hash();
2850 kmem_cache_destroy(pending_cache);
2851 kmem_cache_destroy(exception_cache);
2852
2853 dm_exception_store_exit();
2854}
2855
2856/* Module hooks */
2857module_init(dm_snapshot_init);
2858module_exit(dm_snapshot_exit);
2859
2860MODULE_DESCRIPTION(DM_NAME " snapshot target");
2861MODULE_AUTHOR("Joe Thornber");
2862MODULE_LICENSE("GPL");
2863MODULE_ALIAS("dm-snapshot-origin");
2864MODULE_ALIAS("dm-snapshot-merge");
1/*
2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
3 *
4 * This file is released under the GPL.
5 */
6
7#include <linux/blkdev.h>
8#include <linux/device-mapper.h>
9#include <linux/delay.h>
10#include <linux/fs.h>
11#include <linux/init.h>
12#include <linux/kdev_t.h>
13#include <linux/list.h>
14#include <linux/list_bl.h>
15#include <linux/mempool.h>
16#include <linux/module.h>
17#include <linux/slab.h>
18#include <linux/vmalloc.h>
19#include <linux/log2.h>
20#include <linux/dm-kcopyd.h>
21
22#include "dm.h"
23
24#include "dm-exception-store.h"
25
26#define DM_MSG_PREFIX "snapshots"
27
28static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
29
30#define dm_target_is_snapshot_merge(ti) \
31 ((ti)->type->name == dm_snapshot_merge_target_name)
32
33/*
34 * The size of the mempool used to track chunks in use.
35 */
36#define MIN_IOS 256
37
38#define DM_TRACKED_CHUNK_HASH_SIZE 16
39#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
40 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
41
42struct dm_exception_table {
43 uint32_t hash_mask;
44 unsigned hash_shift;
45 struct hlist_bl_head *table;
46};
47
48struct dm_snapshot {
49 struct rw_semaphore lock;
50
51 struct dm_dev *origin;
52 struct dm_dev *cow;
53
54 struct dm_target *ti;
55
56 /* List of snapshots per Origin */
57 struct list_head list;
58
59 /*
60 * You can't use a snapshot if this is 0 (e.g. if full).
61 * A snapshot-merge target never clears this.
62 */
63 int valid;
64
65 /*
66 * The snapshot overflowed because of a write to the snapshot device.
67 * We don't have to invalidate the snapshot in this case, but we need
68 * to prevent further writes.
69 */
70 int snapshot_overflowed;
71
72 /* Origin writes don't trigger exceptions until this is set */
73 int active;
74
75 atomic_t pending_exceptions_count;
76
77 spinlock_t pe_allocation_lock;
78
79 /* Protected by "pe_allocation_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 unsigned in_progress;
110 struct wait_queue_head in_progress_wait;
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 bool merge_failed:1;
135
136 bool discard_zeroes_cow:1;
137 bool discard_passdown_origin:1;
138
139 /*
140 * Incoming bios that overlap with chunks being merged must wait
141 * for them to be committed.
142 */
143 struct bio_list bios_queued_during_merge;
144};
145
146/*
147 * state_bits:
148 * RUNNING_MERGE - Merge operation is in progress.
149 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
150 * cleared afterwards.
151 */
152#define RUNNING_MERGE 0
153#define SHUTDOWN_MERGE 1
154
155/*
156 * Maximum number of chunks being copied on write.
157 *
158 * The value was decided experimentally as a trade-off between memory
159 * consumption, stalling the kernel's workqueues and maintaining a high enough
160 * throughput.
161 */
162#define DEFAULT_COW_THRESHOLD 2048
163
164static unsigned cow_threshold = DEFAULT_COW_THRESHOLD;
165module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);
166MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
167
168DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
169 "A percentage of time allocated for copy on write");
170
171struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
172{
173 return s->origin;
174}
175EXPORT_SYMBOL(dm_snap_origin);
176
177struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
178{
179 return s->cow;
180}
181EXPORT_SYMBOL(dm_snap_cow);
182
183static sector_t chunk_to_sector(struct dm_exception_store *store,
184 chunk_t chunk)
185{
186 return chunk << store->chunk_shift;
187}
188
189static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
190{
191 /*
192 * There is only ever one instance of a particular block
193 * device so we can compare pointers safely.
194 */
195 return lhs == rhs;
196}
197
198struct dm_snap_pending_exception {
199 struct dm_exception e;
200
201 /*
202 * Origin buffers waiting for this to complete are held
203 * in a bio list
204 */
205 struct bio_list origin_bios;
206 struct bio_list snapshot_bios;
207
208 /* Pointer back to snapshot context */
209 struct dm_snapshot *snap;
210
211 /*
212 * 1 indicates the exception has already been sent to
213 * kcopyd.
214 */
215 int started;
216
217 /* There was copying error. */
218 int copy_error;
219
220 /* A sequence number, it is used for in-order completion. */
221 sector_t exception_sequence;
222
223 struct rb_node out_of_order_node;
224
225 /*
226 * For writing a complete chunk, bypassing the copy.
227 */
228 struct bio *full_bio;
229 bio_end_io_t *full_bio_end_io;
230};
231
232/*
233 * Hash table mapping origin volumes to lists of snapshots and
234 * a lock to protect it
235 */
236static struct kmem_cache *exception_cache;
237static struct kmem_cache *pending_cache;
238
239struct dm_snap_tracked_chunk {
240 struct hlist_node node;
241 chunk_t chunk;
242};
243
244static void init_tracked_chunk(struct bio *bio)
245{
246 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
247 INIT_HLIST_NODE(&c->node);
248}
249
250static bool is_bio_tracked(struct bio *bio)
251{
252 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
253 return !hlist_unhashed(&c->node);
254}
255
256static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
257{
258 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
259
260 c->chunk = chunk;
261
262 spin_lock_irq(&s->tracked_chunk_lock);
263 hlist_add_head(&c->node,
264 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
265 spin_unlock_irq(&s->tracked_chunk_lock);
266}
267
268static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
269{
270 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
271 unsigned long flags;
272
273 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
274 hlist_del(&c->node);
275 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
276}
277
278static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
279{
280 struct dm_snap_tracked_chunk *c;
281 int found = 0;
282
283 spin_lock_irq(&s->tracked_chunk_lock);
284
285 hlist_for_each_entry(c,
286 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
287 if (c->chunk == chunk) {
288 found = 1;
289 break;
290 }
291 }
292
293 spin_unlock_irq(&s->tracked_chunk_lock);
294
295 return found;
296}
297
298/*
299 * This conflicting I/O is extremely improbable in the caller,
300 * so msleep(1) is sufficient and there is no need for a wait queue.
301 */
302static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
303{
304 while (__chunk_is_tracked(s, chunk))
305 msleep(1);
306}
307
308/*
309 * One of these per registered origin, held in the snapshot_origins hash
310 */
311struct origin {
312 /* The origin device */
313 struct block_device *bdev;
314
315 struct list_head hash_list;
316
317 /* List of snapshots for this origin */
318 struct list_head snapshots;
319};
320
321/*
322 * This structure is allocated for each origin target
323 */
324struct dm_origin {
325 struct dm_dev *dev;
326 struct dm_target *ti;
327 unsigned split_boundary;
328 struct list_head hash_list;
329};
330
331/*
332 * Size of the hash table for origin volumes. If we make this
333 * the size of the minors list then it should be nearly perfect
334 */
335#define ORIGIN_HASH_SIZE 256
336#define ORIGIN_MASK 0xFF
337static struct list_head *_origins;
338static struct list_head *_dm_origins;
339static struct rw_semaphore _origins_lock;
340
341static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
342static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
343static uint64_t _pending_exceptions_done_count;
344
345static int init_origin_hash(void)
346{
347 int i;
348
349 _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),
350 GFP_KERNEL);
351 if (!_origins) {
352 DMERR("unable to allocate memory for _origins");
353 return -ENOMEM;
354 }
355 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
356 INIT_LIST_HEAD(_origins + i);
357
358 _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,
359 sizeof(struct list_head),
360 GFP_KERNEL);
361 if (!_dm_origins) {
362 DMERR("unable to allocate memory for _dm_origins");
363 kfree(_origins);
364 return -ENOMEM;
365 }
366 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
367 INIT_LIST_HEAD(_dm_origins + i);
368
369 init_rwsem(&_origins_lock);
370
371 return 0;
372}
373
374static void exit_origin_hash(void)
375{
376 kfree(_origins);
377 kfree(_dm_origins);
378}
379
380static unsigned origin_hash(struct block_device *bdev)
381{
382 return bdev->bd_dev & ORIGIN_MASK;
383}
384
385static struct origin *__lookup_origin(struct block_device *origin)
386{
387 struct list_head *ol;
388 struct origin *o;
389
390 ol = &_origins[origin_hash(origin)];
391 list_for_each_entry (o, ol, hash_list)
392 if (bdev_equal(o->bdev, origin))
393 return o;
394
395 return NULL;
396}
397
398static void __insert_origin(struct origin *o)
399{
400 struct list_head *sl = &_origins[origin_hash(o->bdev)];
401 list_add_tail(&o->hash_list, sl);
402}
403
404static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
405{
406 struct list_head *ol;
407 struct dm_origin *o;
408
409 ol = &_dm_origins[origin_hash(origin)];
410 list_for_each_entry (o, ol, hash_list)
411 if (bdev_equal(o->dev->bdev, origin))
412 return o;
413
414 return NULL;
415}
416
417static void __insert_dm_origin(struct dm_origin *o)
418{
419 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
420 list_add_tail(&o->hash_list, sl);
421}
422
423static void __remove_dm_origin(struct dm_origin *o)
424{
425 list_del(&o->hash_list);
426}
427
428/*
429 * _origins_lock must be held when calling this function.
430 * Returns number of snapshots registered using the supplied cow device, plus:
431 * snap_src - a snapshot suitable for use as a source of exception handover
432 * snap_dest - a snapshot capable of receiving exception handover.
433 * snap_merge - an existing snapshot-merge target linked to the same origin.
434 * There can be at most one snapshot-merge target. The parameter is optional.
435 *
436 * Possible return values and states of snap_src and snap_dest.
437 * 0: NULL, NULL - first new snapshot
438 * 1: snap_src, NULL - normal snapshot
439 * 2: snap_src, snap_dest - waiting for handover
440 * 2: snap_src, NULL - handed over, waiting for old to be deleted
441 * 1: NULL, snap_dest - source got destroyed without handover
442 */
443static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
444 struct dm_snapshot **snap_src,
445 struct dm_snapshot **snap_dest,
446 struct dm_snapshot **snap_merge)
447{
448 struct dm_snapshot *s;
449 struct origin *o;
450 int count = 0;
451 int active;
452
453 o = __lookup_origin(snap->origin->bdev);
454 if (!o)
455 goto out;
456
457 list_for_each_entry(s, &o->snapshots, list) {
458 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
459 *snap_merge = s;
460 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
461 continue;
462
463 down_read(&s->lock);
464 active = s->active;
465 up_read(&s->lock);
466
467 if (active) {
468 if (snap_src)
469 *snap_src = s;
470 } else if (snap_dest)
471 *snap_dest = s;
472
473 count++;
474 }
475
476out:
477 return count;
478}
479
480/*
481 * On success, returns 1 if this snapshot is a handover destination,
482 * otherwise returns 0.
483 */
484static int __validate_exception_handover(struct dm_snapshot *snap)
485{
486 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
487 struct dm_snapshot *snap_merge = NULL;
488
489 /* Does snapshot need exceptions handed over to it? */
490 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
491 &snap_merge) == 2) ||
492 snap_dest) {
493 snap->ti->error = "Snapshot cow pairing for exception "
494 "table handover failed";
495 return -EINVAL;
496 }
497
498 /*
499 * If no snap_src was found, snap cannot become a handover
500 * destination.
501 */
502 if (!snap_src)
503 return 0;
504
505 /*
506 * Non-snapshot-merge handover?
507 */
508 if (!dm_target_is_snapshot_merge(snap->ti))
509 return 1;
510
511 /*
512 * Do not allow more than one merging snapshot.
513 */
514 if (snap_merge) {
515 snap->ti->error = "A snapshot is already merging.";
516 return -EINVAL;
517 }
518
519 if (!snap_src->store->type->prepare_merge ||
520 !snap_src->store->type->commit_merge) {
521 snap->ti->error = "Snapshot exception store does not "
522 "support snapshot-merge.";
523 return -EINVAL;
524 }
525
526 return 1;
527}
528
529static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
530{
531 struct dm_snapshot *l;
532
533 /* Sort the list according to chunk size, largest-first smallest-last */
534 list_for_each_entry(l, &o->snapshots, list)
535 if (l->store->chunk_size < s->store->chunk_size)
536 break;
537 list_add_tail(&s->list, &l->list);
538}
539
540/*
541 * Make a note of the snapshot and its origin so we can look it
542 * up when the origin has a write on it.
543 *
544 * Also validate snapshot exception store handovers.
545 * On success, returns 1 if this registration is a handover destination,
546 * otherwise returns 0.
547 */
548static int register_snapshot(struct dm_snapshot *snap)
549{
550 struct origin *o, *new_o = NULL;
551 struct block_device *bdev = snap->origin->bdev;
552 int r = 0;
553
554 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
555 if (!new_o)
556 return -ENOMEM;
557
558 down_write(&_origins_lock);
559
560 r = __validate_exception_handover(snap);
561 if (r < 0) {
562 kfree(new_o);
563 goto out;
564 }
565
566 o = __lookup_origin(bdev);
567 if (o)
568 kfree(new_o);
569 else {
570 /* New origin */
571 o = new_o;
572
573 /* Initialise the struct */
574 INIT_LIST_HEAD(&o->snapshots);
575 o->bdev = bdev;
576
577 __insert_origin(o);
578 }
579
580 __insert_snapshot(o, snap);
581
582out:
583 up_write(&_origins_lock);
584
585 return r;
586}
587
588/*
589 * Move snapshot to correct place in list according to chunk size.
590 */
591static void reregister_snapshot(struct dm_snapshot *s)
592{
593 struct block_device *bdev = s->origin->bdev;
594
595 down_write(&_origins_lock);
596
597 list_del(&s->list);
598 __insert_snapshot(__lookup_origin(bdev), s);
599
600 up_write(&_origins_lock);
601}
602
603static void unregister_snapshot(struct dm_snapshot *s)
604{
605 struct origin *o;
606
607 down_write(&_origins_lock);
608 o = __lookup_origin(s->origin->bdev);
609
610 list_del(&s->list);
611 if (o && list_empty(&o->snapshots)) {
612 list_del(&o->hash_list);
613 kfree(o);
614 }
615
616 up_write(&_origins_lock);
617}
618
619/*
620 * Implementation of the exception hash tables.
621 * The lowest hash_shift bits of the chunk number are ignored, allowing
622 * some consecutive chunks to be grouped together.
623 */
624static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk);
625
626/* Lock to protect access to the completed and pending exception hash tables. */
627struct dm_exception_table_lock {
628 struct hlist_bl_head *complete_slot;
629 struct hlist_bl_head *pending_slot;
630};
631
632static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk,
633 struct dm_exception_table_lock *lock)
634{
635 struct dm_exception_table *complete = &s->complete;
636 struct dm_exception_table *pending = &s->pending;
637
638 lock->complete_slot = &complete->table[exception_hash(complete, chunk)];
639 lock->pending_slot = &pending->table[exception_hash(pending, chunk)];
640}
641
642static void dm_exception_table_lock(struct dm_exception_table_lock *lock)
643{
644 hlist_bl_lock(lock->complete_slot);
645 hlist_bl_lock(lock->pending_slot);
646}
647
648static void dm_exception_table_unlock(struct dm_exception_table_lock *lock)
649{
650 hlist_bl_unlock(lock->pending_slot);
651 hlist_bl_unlock(lock->complete_slot);
652}
653
654static int dm_exception_table_init(struct dm_exception_table *et,
655 uint32_t size, unsigned hash_shift)
656{
657 unsigned int i;
658
659 et->hash_shift = hash_shift;
660 et->hash_mask = size - 1;
661 et->table = dm_vcalloc(size, sizeof(struct hlist_bl_head));
662 if (!et->table)
663 return -ENOMEM;
664
665 for (i = 0; i < size; i++)
666 INIT_HLIST_BL_HEAD(et->table + i);
667
668 return 0;
669}
670
671static void dm_exception_table_exit(struct dm_exception_table *et,
672 struct kmem_cache *mem)
673{
674 struct hlist_bl_head *slot;
675 struct dm_exception *ex;
676 struct hlist_bl_node *pos, *n;
677 int i, size;
678
679 size = et->hash_mask + 1;
680 for (i = 0; i < size; i++) {
681 slot = et->table + i;
682
683 hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
684 kmem_cache_free(mem, ex);
685 }
686
687 vfree(et->table);
688}
689
690static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
691{
692 return (chunk >> et->hash_shift) & et->hash_mask;
693}
694
695static void dm_remove_exception(struct dm_exception *e)
696{
697 hlist_bl_del(&e->hash_list);
698}
699
700/*
701 * Return the exception data for a sector, or NULL if not
702 * remapped.
703 */
704static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
705 chunk_t chunk)
706{
707 struct hlist_bl_head *slot;
708 struct hlist_bl_node *pos;
709 struct dm_exception *e;
710
711 slot = &et->table[exception_hash(et, chunk)];
712 hlist_bl_for_each_entry(e, pos, slot, hash_list)
713 if (chunk >= e->old_chunk &&
714 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
715 return e;
716
717 return NULL;
718}
719
720static struct dm_exception *alloc_completed_exception(gfp_t gfp)
721{
722 struct dm_exception *e;
723
724 e = kmem_cache_alloc(exception_cache, gfp);
725 if (!e && gfp == GFP_NOIO)
726 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
727
728 return e;
729}
730
731static void free_completed_exception(struct dm_exception *e)
732{
733 kmem_cache_free(exception_cache, e);
734}
735
736static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
737{
738 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
739 GFP_NOIO);
740
741 atomic_inc(&s->pending_exceptions_count);
742 pe->snap = s;
743
744 return pe;
745}
746
747static void free_pending_exception(struct dm_snap_pending_exception *pe)
748{
749 struct dm_snapshot *s = pe->snap;
750
751 mempool_free(pe, &s->pending_pool);
752 smp_mb__before_atomic();
753 atomic_dec(&s->pending_exceptions_count);
754}
755
756static void dm_insert_exception(struct dm_exception_table *eh,
757 struct dm_exception *new_e)
758{
759 struct hlist_bl_head *l;
760 struct hlist_bl_node *pos;
761 struct dm_exception *e = NULL;
762
763 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
764
765 /* Add immediately if this table doesn't support consecutive chunks */
766 if (!eh->hash_shift)
767 goto out;
768
769 /* List is ordered by old_chunk */
770 hlist_bl_for_each_entry(e, pos, l, hash_list) {
771 /* Insert after an existing chunk? */
772 if (new_e->old_chunk == (e->old_chunk +
773 dm_consecutive_chunk_count(e) + 1) &&
774 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
775 dm_consecutive_chunk_count(e) + 1)) {
776 dm_consecutive_chunk_count_inc(e);
777 free_completed_exception(new_e);
778 return;
779 }
780
781 /* Insert before an existing chunk? */
782 if (new_e->old_chunk == (e->old_chunk - 1) &&
783 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
784 dm_consecutive_chunk_count_inc(e);
785 e->old_chunk--;
786 e->new_chunk--;
787 free_completed_exception(new_e);
788 return;
789 }
790
791 if (new_e->old_chunk < e->old_chunk)
792 break;
793 }
794
795out:
796 if (!e) {
797 /*
798 * Either the table doesn't support consecutive chunks or slot
799 * l is empty.
800 */
801 hlist_bl_add_head(&new_e->hash_list, l);
802 } else if (new_e->old_chunk < e->old_chunk) {
803 /* Add before an existing exception */
804 hlist_bl_add_before(&new_e->hash_list, &e->hash_list);
805 } else {
806 /* Add to l's tail: e is the last exception in this slot */
807 hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);
808 }
809}
810
811/*
812 * Callback used by the exception stores to load exceptions when
813 * initialising.
814 */
815static int dm_add_exception(void *context, chunk_t old, chunk_t new)
816{
817 struct dm_exception_table_lock lock;
818 struct dm_snapshot *s = context;
819 struct dm_exception *e;
820
821 e = alloc_completed_exception(GFP_KERNEL);
822 if (!e)
823 return -ENOMEM;
824
825 e->old_chunk = old;
826
827 /* Consecutive_count is implicitly initialised to zero */
828 e->new_chunk = new;
829
830 /*
831 * Although there is no need to lock access to the exception tables
832 * here, if we don't then hlist_bl_add_head(), called by
833 * dm_insert_exception(), will complain about accessing the
834 * corresponding list without locking it first.
835 */
836 dm_exception_table_lock_init(s, old, &lock);
837
838 dm_exception_table_lock(&lock);
839 dm_insert_exception(&s->complete, e);
840 dm_exception_table_unlock(&lock);
841
842 return 0;
843}
844
845/*
846 * Return a minimum chunk size of all snapshots that have the specified origin.
847 * Return zero if the origin has no snapshots.
848 */
849static uint32_t __minimum_chunk_size(struct origin *o)
850{
851 struct dm_snapshot *snap;
852 unsigned chunk_size = 0;
853
854 if (o)
855 list_for_each_entry(snap, &o->snapshots, list)
856 chunk_size = min_not_zero(chunk_size,
857 snap->store->chunk_size);
858
859 return (uint32_t) chunk_size;
860}
861
862/*
863 * Hard coded magic.
864 */
865static int calc_max_buckets(void)
866{
867 /* use a fixed size of 2MB */
868 unsigned long mem = 2 * 1024 * 1024;
869 mem /= sizeof(struct hlist_bl_head);
870
871 return mem;
872}
873
874/*
875 * Allocate room for a suitable hash table.
876 */
877static int init_hash_tables(struct dm_snapshot *s)
878{
879 sector_t hash_size, cow_dev_size, max_buckets;
880
881 /*
882 * Calculate based on the size of the original volume or
883 * the COW volume...
884 */
885 cow_dev_size = get_dev_size(s->cow->bdev);
886 max_buckets = calc_max_buckets();
887
888 hash_size = cow_dev_size >> s->store->chunk_shift;
889 hash_size = min(hash_size, max_buckets);
890
891 if (hash_size < 64)
892 hash_size = 64;
893 hash_size = rounddown_pow_of_two(hash_size);
894 if (dm_exception_table_init(&s->complete, hash_size,
895 DM_CHUNK_CONSECUTIVE_BITS))
896 return -ENOMEM;
897
898 /*
899 * Allocate hash table for in-flight exceptions
900 * Make this smaller than the real hash table
901 */
902 hash_size >>= 3;
903 if (hash_size < 64)
904 hash_size = 64;
905
906 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
907 dm_exception_table_exit(&s->complete, exception_cache);
908 return -ENOMEM;
909 }
910
911 return 0;
912}
913
914static void merge_shutdown(struct dm_snapshot *s)
915{
916 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
917 smp_mb__after_atomic();
918 wake_up_bit(&s->state_bits, RUNNING_MERGE);
919}
920
921static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
922{
923 s->first_merging_chunk = 0;
924 s->num_merging_chunks = 0;
925
926 return bio_list_get(&s->bios_queued_during_merge);
927}
928
929/*
930 * Remove one chunk from the index of completed exceptions.
931 */
932static int __remove_single_exception_chunk(struct dm_snapshot *s,
933 chunk_t old_chunk)
934{
935 struct dm_exception *e;
936
937 e = dm_lookup_exception(&s->complete, old_chunk);
938 if (!e) {
939 DMERR("Corruption detected: exception for block %llu is "
940 "on disk but not in memory",
941 (unsigned long long)old_chunk);
942 return -EINVAL;
943 }
944
945 /*
946 * If this is the only chunk using this exception, remove exception.
947 */
948 if (!dm_consecutive_chunk_count(e)) {
949 dm_remove_exception(e);
950 free_completed_exception(e);
951 return 0;
952 }
953
954 /*
955 * The chunk may be either at the beginning or the end of a
956 * group of consecutive chunks - never in the middle. We are
957 * removing chunks in the opposite order to that in which they
958 * were added, so this should always be true.
959 * Decrement the consecutive chunk counter and adjust the
960 * starting point if necessary.
961 */
962 if (old_chunk == e->old_chunk) {
963 e->old_chunk++;
964 e->new_chunk++;
965 } else if (old_chunk != e->old_chunk +
966 dm_consecutive_chunk_count(e)) {
967 DMERR("Attempt to merge block %llu from the "
968 "middle of a chunk range [%llu - %llu]",
969 (unsigned long long)old_chunk,
970 (unsigned long long)e->old_chunk,
971 (unsigned long long)
972 e->old_chunk + dm_consecutive_chunk_count(e));
973 return -EINVAL;
974 }
975
976 dm_consecutive_chunk_count_dec(e);
977
978 return 0;
979}
980
981static void flush_bios(struct bio *bio);
982
983static int remove_single_exception_chunk(struct dm_snapshot *s)
984{
985 struct bio *b = NULL;
986 int r;
987 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
988
989 down_write(&s->lock);
990
991 /*
992 * Process chunks (and associated exceptions) in reverse order
993 * so that dm_consecutive_chunk_count_dec() accounting works.
994 */
995 do {
996 r = __remove_single_exception_chunk(s, old_chunk);
997 if (r)
998 goto out;
999 } while (old_chunk-- > s->first_merging_chunk);
1000
1001 b = __release_queued_bios_after_merge(s);
1002
1003out:
1004 up_write(&s->lock);
1005 if (b)
1006 flush_bios(b);
1007
1008 return r;
1009}
1010
1011static int origin_write_extent(struct dm_snapshot *merging_snap,
1012 sector_t sector, unsigned chunk_size);
1013
1014static void merge_callback(int read_err, unsigned long write_err,
1015 void *context);
1016
1017static uint64_t read_pending_exceptions_done_count(void)
1018{
1019 uint64_t pending_exceptions_done;
1020
1021 spin_lock(&_pending_exceptions_done_spinlock);
1022 pending_exceptions_done = _pending_exceptions_done_count;
1023 spin_unlock(&_pending_exceptions_done_spinlock);
1024
1025 return pending_exceptions_done;
1026}
1027
1028static void increment_pending_exceptions_done_count(void)
1029{
1030 spin_lock(&_pending_exceptions_done_spinlock);
1031 _pending_exceptions_done_count++;
1032 spin_unlock(&_pending_exceptions_done_spinlock);
1033
1034 wake_up_all(&_pending_exceptions_done);
1035}
1036
1037static void snapshot_merge_next_chunks(struct dm_snapshot *s)
1038{
1039 int i, linear_chunks;
1040 chunk_t old_chunk, new_chunk;
1041 struct dm_io_region src, dest;
1042 sector_t io_size;
1043 uint64_t previous_count;
1044
1045 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
1046 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
1047 goto shut;
1048
1049 /*
1050 * valid flag never changes during merge, so no lock required.
1051 */
1052 if (!s->valid) {
1053 DMERR("Snapshot is invalid: can't merge");
1054 goto shut;
1055 }
1056
1057 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
1058 &new_chunk);
1059 if (linear_chunks <= 0) {
1060 if (linear_chunks < 0) {
1061 DMERR("Read error in exception store: "
1062 "shutting down merge");
1063 down_write(&s->lock);
1064 s->merge_failed = true;
1065 up_write(&s->lock);
1066 }
1067 goto shut;
1068 }
1069
1070 /* Adjust old_chunk and new_chunk to reflect start of linear region */
1071 old_chunk = old_chunk + 1 - linear_chunks;
1072 new_chunk = new_chunk + 1 - linear_chunks;
1073
1074 /*
1075 * Use one (potentially large) I/O to copy all 'linear_chunks'
1076 * from the exception store to the origin
1077 */
1078 io_size = linear_chunks * s->store->chunk_size;
1079
1080 dest.bdev = s->origin->bdev;
1081 dest.sector = chunk_to_sector(s->store, old_chunk);
1082 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1083
1084 src.bdev = s->cow->bdev;
1085 src.sector = chunk_to_sector(s->store, new_chunk);
1086 src.count = dest.count;
1087
1088 /*
1089 * Reallocate any exceptions needed in other snapshots then
1090 * wait for the pending exceptions to complete.
1091 * Each time any pending exception (globally on the system)
1092 * completes we are woken and repeat the process to find out
1093 * if we can proceed. While this may not seem a particularly
1094 * efficient algorithm, it is not expected to have any
1095 * significant impact on performance.
1096 */
1097 previous_count = read_pending_exceptions_done_count();
1098 while (origin_write_extent(s, dest.sector, io_size)) {
1099 wait_event(_pending_exceptions_done,
1100 (read_pending_exceptions_done_count() !=
1101 previous_count));
1102 /* Retry after the wait, until all exceptions are done. */
1103 previous_count = read_pending_exceptions_done_count();
1104 }
1105
1106 down_write(&s->lock);
1107 s->first_merging_chunk = old_chunk;
1108 s->num_merging_chunks = linear_chunks;
1109 up_write(&s->lock);
1110
1111 /* Wait until writes to all 'linear_chunks' drain */
1112 for (i = 0; i < linear_chunks; i++)
1113 __check_for_conflicting_io(s, old_chunk + i);
1114
1115 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1116 return;
1117
1118shut:
1119 merge_shutdown(s);
1120}
1121
1122static void error_bios(struct bio *bio);
1123
1124static void merge_callback(int read_err, unsigned long write_err, void *context)
1125{
1126 struct dm_snapshot *s = context;
1127 struct bio *b = NULL;
1128
1129 if (read_err || write_err) {
1130 if (read_err)
1131 DMERR("Read error: shutting down merge.");
1132 else
1133 DMERR("Write error: shutting down merge.");
1134 goto shut;
1135 }
1136
1137 if (s->store->type->commit_merge(s->store,
1138 s->num_merging_chunks) < 0) {
1139 DMERR("Write error in exception store: shutting down merge");
1140 goto shut;
1141 }
1142
1143 if (remove_single_exception_chunk(s) < 0)
1144 goto shut;
1145
1146 snapshot_merge_next_chunks(s);
1147
1148 return;
1149
1150shut:
1151 down_write(&s->lock);
1152 s->merge_failed = true;
1153 b = __release_queued_bios_after_merge(s);
1154 up_write(&s->lock);
1155 error_bios(b);
1156
1157 merge_shutdown(s);
1158}
1159
1160static void start_merge(struct dm_snapshot *s)
1161{
1162 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1163 snapshot_merge_next_chunks(s);
1164}
1165
1166/*
1167 * Stop the merging process and wait until it finishes.
1168 */
1169static void stop_merge(struct dm_snapshot *s)
1170{
1171 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1172 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1173 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1174}
1175
1176static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,
1177 struct dm_target *ti)
1178{
1179 int r;
1180 unsigned argc;
1181 const char *arg_name;
1182
1183 static const struct dm_arg _args[] = {
1184 {0, 2, "Invalid number of feature arguments"},
1185 };
1186
1187 /*
1188 * No feature arguments supplied.
1189 */
1190 if (!as->argc)
1191 return 0;
1192
1193 r = dm_read_arg_group(_args, as, &argc, &ti->error);
1194 if (r)
1195 return -EINVAL;
1196
1197 while (argc && !r) {
1198 arg_name = dm_shift_arg(as);
1199 argc--;
1200
1201 if (!strcasecmp(arg_name, "discard_zeroes_cow"))
1202 s->discard_zeroes_cow = true;
1203
1204 else if (!strcasecmp(arg_name, "discard_passdown_origin"))
1205 s->discard_passdown_origin = true;
1206
1207 else {
1208 ti->error = "Unrecognised feature requested";
1209 r = -EINVAL;
1210 break;
1211 }
1212 }
1213
1214 if (!s->discard_zeroes_cow && s->discard_passdown_origin) {
1215 /*
1216 * TODO: really these are disjoint.. but ti->num_discard_bios
1217 * and dm_bio_get_target_bio_nr() require rigid constraints.
1218 */
1219 ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";
1220 r = -EINVAL;
1221 }
1222
1223 return r;
1224}
1225
1226/*
1227 * Construct a snapshot mapping:
1228 * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]
1229 */
1230static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1231{
1232 struct dm_snapshot *s;
1233 struct dm_arg_set as;
1234 int i;
1235 int r = -EINVAL;
1236 char *origin_path, *cow_path;
1237 dev_t origin_dev, cow_dev;
1238 unsigned args_used, num_flush_bios = 1;
1239 fmode_t origin_mode = FMODE_READ;
1240
1241 if (argc < 4) {
1242 ti->error = "requires 4 or more arguments";
1243 r = -EINVAL;
1244 goto bad;
1245 }
1246
1247 if (dm_target_is_snapshot_merge(ti)) {
1248 num_flush_bios = 2;
1249 origin_mode = FMODE_WRITE;
1250 }
1251
1252 s = kzalloc(sizeof(*s), GFP_KERNEL);
1253 if (!s) {
1254 ti->error = "Cannot allocate private snapshot structure";
1255 r = -ENOMEM;
1256 goto bad;
1257 }
1258
1259 as.argc = argc;
1260 as.argv = argv;
1261 dm_consume_args(&as, 4);
1262 r = parse_snapshot_features(&as, s, ti);
1263 if (r)
1264 goto bad_features;
1265
1266 origin_path = argv[0];
1267 argv++;
1268 argc--;
1269
1270 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1271 if (r) {
1272 ti->error = "Cannot get origin device";
1273 goto bad_origin;
1274 }
1275 origin_dev = s->origin->bdev->bd_dev;
1276
1277 cow_path = argv[0];
1278 argv++;
1279 argc--;
1280
1281 cow_dev = dm_get_dev_t(cow_path);
1282 if (cow_dev && cow_dev == origin_dev) {
1283 ti->error = "COW device cannot be the same as origin device";
1284 r = -EINVAL;
1285 goto bad_cow;
1286 }
1287
1288 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1289 if (r) {
1290 ti->error = "Cannot get COW device";
1291 goto bad_cow;
1292 }
1293
1294 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1295 if (r) {
1296 ti->error = "Couldn't create exception store";
1297 r = -EINVAL;
1298 goto bad_store;
1299 }
1300
1301 argv += args_used;
1302 argc -= args_used;
1303
1304 s->ti = ti;
1305 s->valid = 1;
1306 s->snapshot_overflowed = 0;
1307 s->active = 0;
1308 atomic_set(&s->pending_exceptions_count, 0);
1309 spin_lock_init(&s->pe_allocation_lock);
1310 s->exception_start_sequence = 0;
1311 s->exception_complete_sequence = 0;
1312 s->out_of_order_tree = RB_ROOT;
1313 init_rwsem(&s->lock);
1314 INIT_LIST_HEAD(&s->list);
1315 spin_lock_init(&s->pe_lock);
1316 s->state_bits = 0;
1317 s->merge_failed = false;
1318 s->first_merging_chunk = 0;
1319 s->num_merging_chunks = 0;
1320 bio_list_init(&s->bios_queued_during_merge);
1321
1322 /* Allocate hash table for COW data */
1323 if (init_hash_tables(s)) {
1324 ti->error = "Unable to allocate hash table space";
1325 r = -ENOMEM;
1326 goto bad_hash_tables;
1327 }
1328
1329 init_waitqueue_head(&s->in_progress_wait);
1330
1331 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1332 if (IS_ERR(s->kcopyd_client)) {
1333 r = PTR_ERR(s->kcopyd_client);
1334 ti->error = "Could not create kcopyd client";
1335 goto bad_kcopyd;
1336 }
1337
1338 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
1339 if (r) {
1340 ti->error = "Could not allocate mempool for pending exceptions";
1341 goto bad_pending_pool;
1342 }
1343
1344 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1345 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1346
1347 spin_lock_init(&s->tracked_chunk_lock);
1348
1349 ti->private = s;
1350 ti->num_flush_bios = num_flush_bios;
1351 if (s->discard_zeroes_cow)
1352 ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
1353 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1354
1355 /* Add snapshot to the list of snapshots for this origin */
1356 /* Exceptions aren't triggered till snapshot_resume() is called */
1357 r = register_snapshot(s);
1358 if (r == -ENOMEM) {
1359 ti->error = "Snapshot origin struct allocation failed";
1360 goto bad_load_and_register;
1361 } else if (r < 0) {
1362 /* invalid handover, register_snapshot has set ti->error */
1363 goto bad_load_and_register;
1364 }
1365
1366 /*
1367 * Metadata must only be loaded into one table at once, so skip this
1368 * if metadata will be handed over during resume.
1369 * Chunk size will be set during the handover - set it to zero to
1370 * ensure it's ignored.
1371 */
1372 if (r > 0) {
1373 s->store->chunk_size = 0;
1374 return 0;
1375 }
1376
1377 r = s->store->type->read_metadata(s->store, dm_add_exception,
1378 (void *)s);
1379 if (r < 0) {
1380 ti->error = "Failed to read snapshot metadata";
1381 goto bad_read_metadata;
1382 } else if (r > 0) {
1383 s->valid = 0;
1384 DMWARN("Snapshot is marked invalid.");
1385 }
1386
1387 if (!s->store->chunk_size) {
1388 ti->error = "Chunk size not set";
1389 goto bad_read_metadata;
1390 }
1391
1392 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1393 if (r)
1394 goto bad_read_metadata;
1395
1396 return 0;
1397
1398bad_read_metadata:
1399 unregister_snapshot(s);
1400bad_load_and_register:
1401 mempool_exit(&s->pending_pool);
1402bad_pending_pool:
1403 dm_kcopyd_client_destroy(s->kcopyd_client);
1404bad_kcopyd:
1405 dm_exception_table_exit(&s->pending, pending_cache);
1406 dm_exception_table_exit(&s->complete, exception_cache);
1407bad_hash_tables:
1408 dm_exception_store_destroy(s->store);
1409bad_store:
1410 dm_put_device(ti, s->cow);
1411bad_cow:
1412 dm_put_device(ti, s->origin);
1413bad_origin:
1414bad_features:
1415 kfree(s);
1416bad:
1417 return r;
1418}
1419
1420static void __free_exceptions(struct dm_snapshot *s)
1421{
1422 dm_kcopyd_client_destroy(s->kcopyd_client);
1423 s->kcopyd_client = NULL;
1424
1425 dm_exception_table_exit(&s->pending, pending_cache);
1426 dm_exception_table_exit(&s->complete, exception_cache);
1427}
1428
1429static void __handover_exceptions(struct dm_snapshot *snap_src,
1430 struct dm_snapshot *snap_dest)
1431{
1432 union {
1433 struct dm_exception_table table_swap;
1434 struct dm_exception_store *store_swap;
1435 } u;
1436
1437 /*
1438 * Swap all snapshot context information between the two instances.
1439 */
1440 u.table_swap = snap_dest->complete;
1441 snap_dest->complete = snap_src->complete;
1442 snap_src->complete = u.table_swap;
1443
1444 u.store_swap = snap_dest->store;
1445 snap_dest->store = snap_src->store;
1446 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1447 snap_src->store = u.store_swap;
1448
1449 snap_dest->store->snap = snap_dest;
1450 snap_src->store->snap = snap_src;
1451
1452 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1453 snap_dest->valid = snap_src->valid;
1454 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1455
1456 /*
1457 * Set source invalid to ensure it receives no further I/O.
1458 */
1459 snap_src->valid = 0;
1460}
1461
1462static void snapshot_dtr(struct dm_target *ti)
1463{
1464#ifdef CONFIG_DM_DEBUG
1465 int i;
1466#endif
1467 struct dm_snapshot *s = ti->private;
1468 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1469
1470 down_read(&_origins_lock);
1471 /* Check whether exception handover must be cancelled */
1472 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1473 if (snap_src && snap_dest && (s == snap_src)) {
1474 down_write(&snap_dest->lock);
1475 snap_dest->valid = 0;
1476 up_write(&snap_dest->lock);
1477 DMERR("Cancelling snapshot handover.");
1478 }
1479 up_read(&_origins_lock);
1480
1481 if (dm_target_is_snapshot_merge(ti))
1482 stop_merge(s);
1483
1484 /* Prevent further origin writes from using this snapshot. */
1485 /* After this returns there can be no new kcopyd jobs. */
1486 unregister_snapshot(s);
1487
1488 while (atomic_read(&s->pending_exceptions_count))
1489 msleep(1);
1490 /*
1491 * Ensure instructions in mempool_exit aren't reordered
1492 * before atomic_read.
1493 */
1494 smp_mb();
1495
1496#ifdef CONFIG_DM_DEBUG
1497 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1498 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1499#endif
1500
1501 __free_exceptions(s);
1502
1503 mempool_exit(&s->pending_pool);
1504
1505 dm_exception_store_destroy(s->store);
1506
1507 dm_put_device(ti, s->cow);
1508
1509 dm_put_device(ti, s->origin);
1510
1511 WARN_ON(s->in_progress);
1512
1513 kfree(s);
1514}
1515
1516static void account_start_copy(struct dm_snapshot *s)
1517{
1518 spin_lock(&s->in_progress_wait.lock);
1519 s->in_progress++;
1520 spin_unlock(&s->in_progress_wait.lock);
1521}
1522
1523static void account_end_copy(struct dm_snapshot *s)
1524{
1525 spin_lock(&s->in_progress_wait.lock);
1526 BUG_ON(!s->in_progress);
1527 s->in_progress--;
1528 if (likely(s->in_progress <= cow_threshold) &&
1529 unlikely(waitqueue_active(&s->in_progress_wait)))
1530 wake_up_locked(&s->in_progress_wait);
1531 spin_unlock(&s->in_progress_wait.lock);
1532}
1533
1534static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
1535{
1536 if (unlikely(s->in_progress > cow_threshold)) {
1537 spin_lock(&s->in_progress_wait.lock);
1538 if (likely(s->in_progress > cow_threshold)) {
1539 /*
1540 * NOTE: this throttle doesn't account for whether
1541 * the caller is servicing an IO that will trigger a COW
1542 * so excess throttling may result for chunks not required
1543 * to be COW'd. But if cow_threshold was reached, extra
1544 * throttling is unlikely to negatively impact performance.
1545 */
1546 DECLARE_WAITQUEUE(wait, current);
1547 __add_wait_queue(&s->in_progress_wait, &wait);
1548 __set_current_state(TASK_UNINTERRUPTIBLE);
1549 spin_unlock(&s->in_progress_wait.lock);
1550 if (unlock_origins)
1551 up_read(&_origins_lock);
1552 io_schedule();
1553 remove_wait_queue(&s->in_progress_wait, &wait);
1554 return false;
1555 }
1556 spin_unlock(&s->in_progress_wait.lock);
1557 }
1558 return true;
1559}
1560
1561/*
1562 * Flush a list of buffers.
1563 */
1564static void flush_bios(struct bio *bio)
1565{
1566 struct bio *n;
1567
1568 while (bio) {
1569 n = bio->bi_next;
1570 bio->bi_next = NULL;
1571 submit_bio_noacct(bio);
1572 bio = n;
1573 }
1574}
1575
1576static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
1577
1578/*
1579 * Flush a list of buffers.
1580 */
1581static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1582{
1583 struct bio *n;
1584 int r;
1585
1586 while (bio) {
1587 n = bio->bi_next;
1588 bio->bi_next = NULL;
1589 r = do_origin(s->origin, bio, false);
1590 if (r == DM_MAPIO_REMAPPED)
1591 submit_bio_noacct(bio);
1592 bio = n;
1593 }
1594}
1595
1596/*
1597 * Error a list of buffers.
1598 */
1599static void error_bios(struct bio *bio)
1600{
1601 struct bio *n;
1602
1603 while (bio) {
1604 n = bio->bi_next;
1605 bio->bi_next = NULL;
1606 bio_io_error(bio);
1607 bio = n;
1608 }
1609}
1610
1611static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1612{
1613 if (!s->valid)
1614 return;
1615
1616 if (err == -EIO)
1617 DMERR("Invalidating snapshot: Error reading/writing.");
1618 else if (err == -ENOMEM)
1619 DMERR("Invalidating snapshot: Unable to allocate exception.");
1620
1621 if (s->store->type->drop_snapshot)
1622 s->store->type->drop_snapshot(s->store);
1623
1624 s->valid = 0;
1625
1626 dm_table_event(s->ti->table);
1627}
1628
1629static void invalidate_snapshot(struct dm_snapshot *s, int err)
1630{
1631 down_write(&s->lock);
1632 __invalidate_snapshot(s, err);
1633 up_write(&s->lock);
1634}
1635
1636static void pending_complete(void *context, int success)
1637{
1638 struct dm_snap_pending_exception *pe = context;
1639 struct dm_exception *e;
1640 struct dm_snapshot *s = pe->snap;
1641 struct bio *origin_bios = NULL;
1642 struct bio *snapshot_bios = NULL;
1643 struct bio *full_bio = NULL;
1644 struct dm_exception_table_lock lock;
1645 int error = 0;
1646
1647 dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);
1648
1649 if (!success) {
1650 /* Read/write error - snapshot is unusable */
1651 invalidate_snapshot(s, -EIO);
1652 error = 1;
1653
1654 dm_exception_table_lock(&lock);
1655 goto out;
1656 }
1657
1658 e = alloc_completed_exception(GFP_NOIO);
1659 if (!e) {
1660 invalidate_snapshot(s, -ENOMEM);
1661 error = 1;
1662
1663 dm_exception_table_lock(&lock);
1664 goto out;
1665 }
1666 *e = pe->e;
1667
1668 down_read(&s->lock);
1669 dm_exception_table_lock(&lock);
1670 if (!s->valid) {
1671 up_read(&s->lock);
1672 free_completed_exception(e);
1673 error = 1;
1674
1675 goto out;
1676 }
1677
1678 /*
1679 * Add a proper exception. After inserting the completed exception all
1680 * subsequent snapshot reads to this chunk will be redirected to the
1681 * COW device. This ensures that we do not starve. Moreover, as long
1682 * as the pending exception exists, neither origin writes nor snapshot
1683 * merging can overwrite the chunk in origin.
1684 */
1685 dm_insert_exception(&s->complete, e);
1686 up_read(&s->lock);
1687
1688 /* Wait for conflicting reads to drain */
1689 if (__chunk_is_tracked(s, pe->e.old_chunk)) {
1690 dm_exception_table_unlock(&lock);
1691 __check_for_conflicting_io(s, pe->e.old_chunk);
1692 dm_exception_table_lock(&lock);
1693 }
1694
1695out:
1696 /* Remove the in-flight exception from the list */
1697 dm_remove_exception(&pe->e);
1698
1699 dm_exception_table_unlock(&lock);
1700
1701 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1702 origin_bios = bio_list_get(&pe->origin_bios);
1703 full_bio = pe->full_bio;
1704 if (full_bio)
1705 full_bio->bi_end_io = pe->full_bio_end_io;
1706 increment_pending_exceptions_done_count();
1707
1708 /* Submit any pending write bios */
1709 if (error) {
1710 if (full_bio)
1711 bio_io_error(full_bio);
1712 error_bios(snapshot_bios);
1713 } else {
1714 if (full_bio)
1715 bio_endio(full_bio);
1716 flush_bios(snapshot_bios);
1717 }
1718
1719 retry_origin_bios(s, origin_bios);
1720
1721 free_pending_exception(pe);
1722}
1723
1724static void complete_exception(struct dm_snap_pending_exception *pe)
1725{
1726 struct dm_snapshot *s = pe->snap;
1727
1728 /* Update the metadata if we are persistent */
1729 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1730 pending_complete, pe);
1731}
1732
1733/*
1734 * Called when the copy I/O has finished. kcopyd actually runs
1735 * this code so don't block.
1736 */
1737static void copy_callback(int read_err, unsigned long write_err, void *context)
1738{
1739 struct dm_snap_pending_exception *pe = context;
1740 struct dm_snapshot *s = pe->snap;
1741
1742 pe->copy_error = read_err || write_err;
1743
1744 if (pe->exception_sequence == s->exception_complete_sequence) {
1745 struct rb_node *next;
1746
1747 s->exception_complete_sequence++;
1748 complete_exception(pe);
1749
1750 next = rb_first(&s->out_of_order_tree);
1751 while (next) {
1752 pe = rb_entry(next, struct dm_snap_pending_exception,
1753 out_of_order_node);
1754 if (pe->exception_sequence != s->exception_complete_sequence)
1755 break;
1756 next = rb_next(next);
1757 s->exception_complete_sequence++;
1758 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
1759 complete_exception(pe);
1760 cond_resched();
1761 }
1762 } else {
1763 struct rb_node *parent = NULL;
1764 struct rb_node **p = &s->out_of_order_tree.rb_node;
1765 struct dm_snap_pending_exception *pe2;
1766
1767 while (*p) {
1768 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
1769 parent = *p;
1770
1771 BUG_ON(pe->exception_sequence == pe2->exception_sequence);
1772 if (pe->exception_sequence < pe2->exception_sequence)
1773 p = &((*p)->rb_left);
1774 else
1775 p = &((*p)->rb_right);
1776 }
1777
1778 rb_link_node(&pe->out_of_order_node, parent, p);
1779 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
1780 }
1781 account_end_copy(s);
1782}
1783
1784/*
1785 * Dispatches the copy operation to kcopyd.
1786 */
1787static void start_copy(struct dm_snap_pending_exception *pe)
1788{
1789 struct dm_snapshot *s = pe->snap;
1790 struct dm_io_region src, dest;
1791 struct block_device *bdev = s->origin->bdev;
1792 sector_t dev_size;
1793
1794 dev_size = get_dev_size(bdev);
1795
1796 src.bdev = bdev;
1797 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1798 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1799
1800 dest.bdev = s->cow->bdev;
1801 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1802 dest.count = src.count;
1803
1804 /* Hand over to kcopyd */
1805 account_start_copy(s);
1806 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1807}
1808
1809static void full_bio_end_io(struct bio *bio)
1810{
1811 void *callback_data = bio->bi_private;
1812
1813 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
1814}
1815
1816static void start_full_bio(struct dm_snap_pending_exception *pe,
1817 struct bio *bio)
1818{
1819 struct dm_snapshot *s = pe->snap;
1820 void *callback_data;
1821
1822 pe->full_bio = bio;
1823 pe->full_bio_end_io = bio->bi_end_io;
1824
1825 account_start_copy(s);
1826 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1827 copy_callback, pe);
1828
1829 bio->bi_end_io = full_bio_end_io;
1830 bio->bi_private = callback_data;
1831
1832 submit_bio_noacct(bio);
1833}
1834
1835static struct dm_snap_pending_exception *
1836__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1837{
1838 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1839
1840 if (!e)
1841 return NULL;
1842
1843 return container_of(e, struct dm_snap_pending_exception, e);
1844}
1845
1846/*
1847 * Inserts a pending exception into the pending table.
1848 *
1849 * NOTE: a write lock must be held on the chunk's pending exception table slot
1850 * before calling this.
1851 */
1852static struct dm_snap_pending_exception *
1853__insert_pending_exception(struct dm_snapshot *s,
1854 struct dm_snap_pending_exception *pe, chunk_t chunk)
1855{
1856 pe->e.old_chunk = chunk;
1857 bio_list_init(&pe->origin_bios);
1858 bio_list_init(&pe->snapshot_bios);
1859 pe->started = 0;
1860 pe->full_bio = NULL;
1861
1862 spin_lock(&s->pe_allocation_lock);
1863 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1864 spin_unlock(&s->pe_allocation_lock);
1865 free_pending_exception(pe);
1866 return NULL;
1867 }
1868
1869 pe->exception_sequence = s->exception_start_sequence++;
1870 spin_unlock(&s->pe_allocation_lock);
1871
1872 dm_insert_exception(&s->pending, &pe->e);
1873
1874 return pe;
1875}
1876
1877/*
1878 * Looks to see if this snapshot already has a pending exception
1879 * for this chunk, otherwise it allocates a new one and inserts
1880 * it into the pending table.
1881 *
1882 * NOTE: a write lock must be held on the chunk's pending exception table slot
1883 * before calling this.
1884 */
1885static struct dm_snap_pending_exception *
1886__find_pending_exception(struct dm_snapshot *s,
1887 struct dm_snap_pending_exception *pe, chunk_t chunk)
1888{
1889 struct dm_snap_pending_exception *pe2;
1890
1891 pe2 = __lookup_pending_exception(s, chunk);
1892 if (pe2) {
1893 free_pending_exception(pe);
1894 return pe2;
1895 }
1896
1897 return __insert_pending_exception(s, pe, chunk);
1898}
1899
1900static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1901 struct bio *bio, chunk_t chunk)
1902{
1903 bio_set_dev(bio, s->cow->bdev);
1904 bio->bi_iter.bi_sector =
1905 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1906 (chunk - e->old_chunk)) +
1907 (bio->bi_iter.bi_sector & s->store->chunk_mask);
1908}
1909
1910static void zero_callback(int read_err, unsigned long write_err, void *context)
1911{
1912 struct bio *bio = context;
1913 struct dm_snapshot *s = bio->bi_private;
1914
1915 account_end_copy(s);
1916 bio->bi_status = write_err ? BLK_STS_IOERR : 0;
1917 bio_endio(bio);
1918}
1919
1920static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
1921 struct bio *bio, chunk_t chunk)
1922{
1923 struct dm_io_region dest;
1924
1925 dest.bdev = s->cow->bdev;
1926 dest.sector = bio->bi_iter.bi_sector;
1927 dest.count = s->store->chunk_size;
1928
1929 account_start_copy(s);
1930 WARN_ON_ONCE(bio->bi_private);
1931 bio->bi_private = s;
1932 dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
1933}
1934
1935static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)
1936{
1937 return bio->bi_iter.bi_size ==
1938 (s->store->chunk_size << SECTOR_SHIFT);
1939}
1940
1941static int snapshot_map(struct dm_target *ti, struct bio *bio)
1942{
1943 struct dm_exception *e;
1944 struct dm_snapshot *s = ti->private;
1945 int r = DM_MAPIO_REMAPPED;
1946 chunk_t chunk;
1947 struct dm_snap_pending_exception *pe = NULL;
1948 struct dm_exception_table_lock lock;
1949
1950 init_tracked_chunk(bio);
1951
1952 if (bio->bi_opf & REQ_PREFLUSH) {
1953 bio_set_dev(bio, s->cow->bdev);
1954 return DM_MAPIO_REMAPPED;
1955 }
1956
1957 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1958 dm_exception_table_lock_init(s, chunk, &lock);
1959
1960 /* Full snapshots are not usable */
1961 /* To get here the table must be live so s->active is always set. */
1962 if (!s->valid)
1963 return DM_MAPIO_KILL;
1964
1965 if (bio_data_dir(bio) == WRITE) {
1966 while (unlikely(!wait_for_in_progress(s, false)))
1967 ; /* wait_for_in_progress() has slept */
1968 }
1969
1970 down_read(&s->lock);
1971 dm_exception_table_lock(&lock);
1972
1973 if (!s->valid || (unlikely(s->snapshot_overflowed) &&
1974 bio_data_dir(bio) == WRITE)) {
1975 r = DM_MAPIO_KILL;
1976 goto out_unlock;
1977 }
1978
1979 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
1980 if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {
1981 /*
1982 * passdown discard to origin (without triggering
1983 * snapshot exceptions via do_origin; doing so would
1984 * defeat the goal of freeing space in origin that is
1985 * implied by the "discard_passdown_origin" feature)
1986 */
1987 bio_set_dev(bio, s->origin->bdev);
1988 track_chunk(s, bio, chunk);
1989 goto out_unlock;
1990 }
1991 /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */
1992 }
1993
1994 /* If the block is already remapped - use that, else remap it */
1995 e = dm_lookup_exception(&s->complete, chunk);
1996 if (e) {
1997 remap_exception(s, e, bio, chunk);
1998 if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
1999 io_overlaps_chunk(s, bio)) {
2000 dm_exception_table_unlock(&lock);
2001 up_read(&s->lock);
2002 zero_exception(s, e, bio, chunk);
2003 r = DM_MAPIO_SUBMITTED; /* discard is not issued */
2004 goto out;
2005 }
2006 goto out_unlock;
2007 }
2008
2009 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2010 /*
2011 * If no exception exists, complete discard immediately
2012 * otherwise it'll trigger copy-out.
2013 */
2014 bio_endio(bio);
2015 r = DM_MAPIO_SUBMITTED;
2016 goto out_unlock;
2017 }
2018
2019 /*
2020 * Write to snapshot - higher level takes care of RW/RO
2021 * flags so we should only get this if we are
2022 * writeable.
2023 */
2024 if (bio_data_dir(bio) == WRITE) {
2025 pe = __lookup_pending_exception(s, chunk);
2026 if (!pe) {
2027 dm_exception_table_unlock(&lock);
2028 pe = alloc_pending_exception(s);
2029 dm_exception_table_lock(&lock);
2030
2031 e = dm_lookup_exception(&s->complete, chunk);
2032 if (e) {
2033 free_pending_exception(pe);
2034 remap_exception(s, e, bio, chunk);
2035 goto out_unlock;
2036 }
2037
2038 pe = __find_pending_exception(s, pe, chunk);
2039 if (!pe) {
2040 dm_exception_table_unlock(&lock);
2041 up_read(&s->lock);
2042
2043 down_write(&s->lock);
2044
2045 if (s->store->userspace_supports_overflow) {
2046 if (s->valid && !s->snapshot_overflowed) {
2047 s->snapshot_overflowed = 1;
2048 DMERR("Snapshot overflowed: Unable to allocate exception.");
2049 }
2050 } else
2051 __invalidate_snapshot(s, -ENOMEM);
2052 up_write(&s->lock);
2053
2054 r = DM_MAPIO_KILL;
2055 goto out;
2056 }
2057 }
2058
2059 remap_exception(s, &pe->e, bio, chunk);
2060
2061 r = DM_MAPIO_SUBMITTED;
2062
2063 if (!pe->started && io_overlaps_chunk(s, bio)) {
2064 pe->started = 1;
2065
2066 dm_exception_table_unlock(&lock);
2067 up_read(&s->lock);
2068
2069 start_full_bio(pe, bio);
2070 goto out;
2071 }
2072
2073 bio_list_add(&pe->snapshot_bios, bio);
2074
2075 if (!pe->started) {
2076 /* this is protected by the exception table lock */
2077 pe->started = 1;
2078
2079 dm_exception_table_unlock(&lock);
2080 up_read(&s->lock);
2081
2082 start_copy(pe);
2083 goto out;
2084 }
2085 } else {
2086 bio_set_dev(bio, s->origin->bdev);
2087 track_chunk(s, bio, chunk);
2088 }
2089
2090out_unlock:
2091 dm_exception_table_unlock(&lock);
2092 up_read(&s->lock);
2093out:
2094 return r;
2095}
2096
2097/*
2098 * A snapshot-merge target behaves like a combination of a snapshot
2099 * target and a snapshot-origin target. It only generates new
2100 * exceptions in other snapshots and not in the one that is being
2101 * merged.
2102 *
2103 * For each chunk, if there is an existing exception, it is used to
2104 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
2105 * which in turn might generate exceptions in other snapshots.
2106 * If merging is currently taking place on the chunk in question, the
2107 * I/O is deferred by adding it to s->bios_queued_during_merge.
2108 */
2109static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
2110{
2111 struct dm_exception *e;
2112 struct dm_snapshot *s = ti->private;
2113 int r = DM_MAPIO_REMAPPED;
2114 chunk_t chunk;
2115
2116 init_tracked_chunk(bio);
2117
2118 if (bio->bi_opf & REQ_PREFLUSH) {
2119 if (!dm_bio_get_target_bio_nr(bio))
2120 bio_set_dev(bio, s->origin->bdev);
2121 else
2122 bio_set_dev(bio, s->cow->bdev);
2123 return DM_MAPIO_REMAPPED;
2124 }
2125
2126 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2127 /* Once merging, discards no longer effect change */
2128 bio_endio(bio);
2129 return DM_MAPIO_SUBMITTED;
2130 }
2131
2132 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
2133
2134 down_write(&s->lock);
2135
2136 /* Full merging snapshots are redirected to the origin */
2137 if (!s->valid)
2138 goto redirect_to_origin;
2139
2140 /* If the block is already remapped - use that */
2141 e = dm_lookup_exception(&s->complete, chunk);
2142 if (e) {
2143 /* Queue writes overlapping with chunks being merged */
2144 if (bio_data_dir(bio) == WRITE &&
2145 chunk >= s->first_merging_chunk &&
2146 chunk < (s->first_merging_chunk +
2147 s->num_merging_chunks)) {
2148 bio_set_dev(bio, s->origin->bdev);
2149 bio_list_add(&s->bios_queued_during_merge, bio);
2150 r = DM_MAPIO_SUBMITTED;
2151 goto out_unlock;
2152 }
2153
2154 remap_exception(s, e, bio, chunk);
2155
2156 if (bio_data_dir(bio) == WRITE)
2157 track_chunk(s, bio, chunk);
2158 goto out_unlock;
2159 }
2160
2161redirect_to_origin:
2162 bio_set_dev(bio, s->origin->bdev);
2163
2164 if (bio_data_dir(bio) == WRITE) {
2165 up_write(&s->lock);
2166 return do_origin(s->origin, bio, false);
2167 }
2168
2169out_unlock:
2170 up_write(&s->lock);
2171
2172 return r;
2173}
2174
2175static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
2176 blk_status_t *error)
2177{
2178 struct dm_snapshot *s = ti->private;
2179
2180 if (is_bio_tracked(bio))
2181 stop_tracking_chunk(s, bio);
2182
2183 return DM_ENDIO_DONE;
2184}
2185
2186static void snapshot_merge_presuspend(struct dm_target *ti)
2187{
2188 struct dm_snapshot *s = ti->private;
2189
2190 stop_merge(s);
2191}
2192
2193static int snapshot_preresume(struct dm_target *ti)
2194{
2195 int r = 0;
2196 struct dm_snapshot *s = ti->private;
2197 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2198
2199 down_read(&_origins_lock);
2200 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2201 if (snap_src && snap_dest) {
2202 down_read(&snap_src->lock);
2203 if (s == snap_src) {
2204 DMERR("Unable to resume snapshot source until "
2205 "handover completes.");
2206 r = -EINVAL;
2207 } else if (!dm_suspended(snap_src->ti)) {
2208 DMERR("Unable to perform snapshot handover until "
2209 "source is suspended.");
2210 r = -EINVAL;
2211 }
2212 up_read(&snap_src->lock);
2213 }
2214 up_read(&_origins_lock);
2215
2216 return r;
2217}
2218
2219static void snapshot_resume(struct dm_target *ti)
2220{
2221 struct dm_snapshot *s = ti->private;
2222 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
2223 struct dm_origin *o;
2224 struct mapped_device *origin_md = NULL;
2225 bool must_restart_merging = false;
2226
2227 down_read(&_origins_lock);
2228
2229 o = __lookup_dm_origin(s->origin->bdev);
2230 if (o)
2231 origin_md = dm_table_get_md(o->ti->table);
2232 if (!origin_md) {
2233 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
2234 if (snap_merging)
2235 origin_md = dm_table_get_md(snap_merging->ti->table);
2236 }
2237 if (origin_md == dm_table_get_md(ti->table))
2238 origin_md = NULL;
2239 if (origin_md) {
2240 if (dm_hold(origin_md))
2241 origin_md = NULL;
2242 }
2243
2244 up_read(&_origins_lock);
2245
2246 if (origin_md) {
2247 dm_internal_suspend_fast(origin_md);
2248 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
2249 must_restart_merging = true;
2250 stop_merge(snap_merging);
2251 }
2252 }
2253
2254 down_read(&_origins_lock);
2255
2256 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2257 if (snap_src && snap_dest) {
2258 down_write(&snap_src->lock);
2259 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
2260 __handover_exceptions(snap_src, snap_dest);
2261 up_write(&snap_dest->lock);
2262 up_write(&snap_src->lock);
2263 }
2264
2265 up_read(&_origins_lock);
2266
2267 if (origin_md) {
2268 if (must_restart_merging)
2269 start_merge(snap_merging);
2270 dm_internal_resume_fast(origin_md);
2271 dm_put(origin_md);
2272 }
2273
2274 /* Now we have correct chunk size, reregister */
2275 reregister_snapshot(s);
2276
2277 down_write(&s->lock);
2278 s->active = 1;
2279 up_write(&s->lock);
2280}
2281
2282static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
2283{
2284 uint32_t min_chunksize;
2285
2286 down_read(&_origins_lock);
2287 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
2288 up_read(&_origins_lock);
2289
2290 return min_chunksize;
2291}
2292
2293static void snapshot_merge_resume(struct dm_target *ti)
2294{
2295 struct dm_snapshot *s = ti->private;
2296
2297 /*
2298 * Handover exceptions from existing snapshot.
2299 */
2300 snapshot_resume(ti);
2301
2302 /*
2303 * snapshot-merge acts as an origin, so set ti->max_io_len
2304 */
2305 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
2306
2307 start_merge(s);
2308}
2309
2310static void snapshot_status(struct dm_target *ti, status_type_t type,
2311 unsigned status_flags, char *result, unsigned maxlen)
2312{
2313 unsigned sz = 0;
2314 struct dm_snapshot *snap = ti->private;
2315 unsigned num_features;
2316
2317 switch (type) {
2318 case STATUSTYPE_INFO:
2319
2320 down_write(&snap->lock);
2321
2322 if (!snap->valid)
2323 DMEMIT("Invalid");
2324 else if (snap->merge_failed)
2325 DMEMIT("Merge failed");
2326 else if (snap->snapshot_overflowed)
2327 DMEMIT("Overflow");
2328 else {
2329 if (snap->store->type->usage) {
2330 sector_t total_sectors, sectors_allocated,
2331 metadata_sectors;
2332 snap->store->type->usage(snap->store,
2333 &total_sectors,
2334 §ors_allocated,
2335 &metadata_sectors);
2336 DMEMIT("%llu/%llu %llu",
2337 (unsigned long long)sectors_allocated,
2338 (unsigned long long)total_sectors,
2339 (unsigned long long)metadata_sectors);
2340 }
2341 else
2342 DMEMIT("Unknown");
2343 }
2344
2345 up_write(&snap->lock);
2346
2347 break;
2348
2349 case STATUSTYPE_TABLE:
2350 /*
2351 * kdevname returns a static pointer so we need
2352 * to make private copies if the output is to
2353 * make sense.
2354 */
2355 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2356 sz += snap->store->type->status(snap->store, type, result + sz,
2357 maxlen - sz);
2358 num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;
2359 if (num_features) {
2360 DMEMIT(" %u", num_features);
2361 if (snap->discard_zeroes_cow)
2362 DMEMIT(" discard_zeroes_cow");
2363 if (snap->discard_passdown_origin)
2364 DMEMIT(" discard_passdown_origin");
2365 }
2366 break;
2367 }
2368}
2369
2370static int snapshot_iterate_devices(struct dm_target *ti,
2371 iterate_devices_callout_fn fn, void *data)
2372{
2373 struct dm_snapshot *snap = ti->private;
2374 int r;
2375
2376 r = fn(ti, snap->origin, 0, ti->len, data);
2377
2378 if (!r)
2379 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2380
2381 return r;
2382}
2383
2384static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
2385{
2386 struct dm_snapshot *snap = ti->private;
2387
2388 if (snap->discard_zeroes_cow) {
2389 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2390
2391 down_read(&_origins_lock);
2392
2393 (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);
2394 if (snap_src && snap_dest)
2395 snap = snap_src;
2396
2397 /* All discards are split on chunk_size boundary */
2398 limits->discard_granularity = snap->store->chunk_size;
2399 limits->max_discard_sectors = snap->store->chunk_size;
2400
2401 up_read(&_origins_lock);
2402 }
2403}
2404
2405/*-----------------------------------------------------------------
2406 * Origin methods
2407 *---------------------------------------------------------------*/
2408
2409/*
2410 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2411 * supplied bio was ignored. The caller may submit it immediately.
2412 * (No remapping actually occurs as the origin is always a direct linear
2413 * map.)
2414 *
2415 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2416 * and any supplied bio is added to a list to be submitted once all
2417 * the necessary exceptions exist.
2418 */
2419static int __origin_write(struct list_head *snapshots, sector_t sector,
2420 struct bio *bio)
2421{
2422 int r = DM_MAPIO_REMAPPED;
2423 struct dm_snapshot *snap;
2424 struct dm_exception *e;
2425 struct dm_snap_pending_exception *pe, *pe2;
2426 struct dm_snap_pending_exception *pe_to_start_now = NULL;
2427 struct dm_snap_pending_exception *pe_to_start_last = NULL;
2428 struct dm_exception_table_lock lock;
2429 chunk_t chunk;
2430
2431 /* Do all the snapshots on this origin */
2432 list_for_each_entry (snap, snapshots, list) {
2433 /*
2434 * Don't make new exceptions in a merging snapshot
2435 * because it has effectively been deleted
2436 */
2437 if (dm_target_is_snapshot_merge(snap->ti))
2438 continue;
2439
2440 /* Nothing to do if writing beyond end of snapshot */
2441 if (sector >= dm_table_get_size(snap->ti->table))
2442 continue;
2443
2444 /*
2445 * Remember, different snapshots can have
2446 * different chunk sizes.
2447 */
2448 chunk = sector_to_chunk(snap->store, sector);
2449 dm_exception_table_lock_init(snap, chunk, &lock);
2450
2451 down_read(&snap->lock);
2452 dm_exception_table_lock(&lock);
2453
2454 /* Only deal with valid and active snapshots */
2455 if (!snap->valid || !snap->active)
2456 goto next_snapshot;
2457
2458 pe = __lookup_pending_exception(snap, chunk);
2459 if (!pe) {
2460 /*
2461 * Check exception table to see if block is already
2462 * remapped in this snapshot and trigger an exception
2463 * if not.
2464 */
2465 e = dm_lookup_exception(&snap->complete, chunk);
2466 if (e)
2467 goto next_snapshot;
2468
2469 dm_exception_table_unlock(&lock);
2470 pe = alloc_pending_exception(snap);
2471 dm_exception_table_lock(&lock);
2472
2473 pe2 = __lookup_pending_exception(snap, chunk);
2474
2475 if (!pe2) {
2476 e = dm_lookup_exception(&snap->complete, chunk);
2477 if (e) {
2478 free_pending_exception(pe);
2479 goto next_snapshot;
2480 }
2481
2482 pe = __insert_pending_exception(snap, pe, chunk);
2483 if (!pe) {
2484 dm_exception_table_unlock(&lock);
2485 up_read(&snap->lock);
2486
2487 invalidate_snapshot(snap, -ENOMEM);
2488 continue;
2489 }
2490 } else {
2491 free_pending_exception(pe);
2492 pe = pe2;
2493 }
2494 }
2495
2496 r = DM_MAPIO_SUBMITTED;
2497
2498 /*
2499 * If an origin bio was supplied, queue it to wait for the
2500 * completion of this exception, and start this one last,
2501 * at the end of the function.
2502 */
2503 if (bio) {
2504 bio_list_add(&pe->origin_bios, bio);
2505 bio = NULL;
2506
2507 if (!pe->started) {
2508 pe->started = 1;
2509 pe_to_start_last = pe;
2510 }
2511 }
2512
2513 if (!pe->started) {
2514 pe->started = 1;
2515 pe_to_start_now = pe;
2516 }
2517
2518next_snapshot:
2519 dm_exception_table_unlock(&lock);
2520 up_read(&snap->lock);
2521
2522 if (pe_to_start_now) {
2523 start_copy(pe_to_start_now);
2524 pe_to_start_now = NULL;
2525 }
2526 }
2527
2528 /*
2529 * Submit the exception against which the bio is queued last,
2530 * to give the other exceptions a head start.
2531 */
2532 if (pe_to_start_last)
2533 start_copy(pe_to_start_last);
2534
2535 return r;
2536}
2537
2538/*
2539 * Called on a write from the origin driver.
2540 */
2541static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
2542{
2543 struct origin *o;
2544 int r = DM_MAPIO_REMAPPED;
2545
2546again:
2547 down_read(&_origins_lock);
2548 o = __lookup_origin(origin->bdev);
2549 if (o) {
2550 if (limit) {
2551 struct dm_snapshot *s;
2552 list_for_each_entry(s, &o->snapshots, list)
2553 if (unlikely(!wait_for_in_progress(s, true)))
2554 goto again;
2555 }
2556
2557 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
2558 }
2559 up_read(&_origins_lock);
2560
2561 return r;
2562}
2563
2564/*
2565 * Trigger exceptions in all non-merging snapshots.
2566 *
2567 * The chunk size of the merging snapshot may be larger than the chunk
2568 * size of some other snapshot so we may need to reallocate multiple
2569 * chunks in other snapshots.
2570 *
2571 * We scan all the overlapping exceptions in the other snapshots.
2572 * Returns 1 if anything was reallocated and must be waited for,
2573 * otherwise returns 0.
2574 *
2575 * size must be a multiple of merging_snap's chunk_size.
2576 */
2577static int origin_write_extent(struct dm_snapshot *merging_snap,
2578 sector_t sector, unsigned size)
2579{
2580 int must_wait = 0;
2581 sector_t n;
2582 struct origin *o;
2583
2584 /*
2585 * The origin's __minimum_chunk_size() got stored in max_io_len
2586 * by snapshot_merge_resume().
2587 */
2588 down_read(&_origins_lock);
2589 o = __lookup_origin(merging_snap->origin->bdev);
2590 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2591 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2592 DM_MAPIO_SUBMITTED)
2593 must_wait = 1;
2594 up_read(&_origins_lock);
2595
2596 return must_wait;
2597}
2598
2599/*
2600 * Origin: maps a linear range of a device, with hooks for snapshotting.
2601 */
2602
2603/*
2604 * Construct an origin mapping: <dev_path>
2605 * The context for an origin is merely a 'struct dm_dev *'
2606 * pointing to the real device.
2607 */
2608static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2609{
2610 int r;
2611 struct dm_origin *o;
2612
2613 if (argc != 1) {
2614 ti->error = "origin: incorrect number of arguments";
2615 return -EINVAL;
2616 }
2617
2618 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2619 if (!o) {
2620 ti->error = "Cannot allocate private origin structure";
2621 r = -ENOMEM;
2622 goto bad_alloc;
2623 }
2624
2625 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2626 if (r) {
2627 ti->error = "Cannot get target device";
2628 goto bad_open;
2629 }
2630
2631 o->ti = ti;
2632 ti->private = o;
2633 ti->num_flush_bios = 1;
2634
2635 return 0;
2636
2637bad_open:
2638 kfree(o);
2639bad_alloc:
2640 return r;
2641}
2642
2643static void origin_dtr(struct dm_target *ti)
2644{
2645 struct dm_origin *o = ti->private;
2646
2647 dm_put_device(ti, o->dev);
2648 kfree(o);
2649}
2650
2651static int origin_map(struct dm_target *ti, struct bio *bio)
2652{
2653 struct dm_origin *o = ti->private;
2654 unsigned available_sectors;
2655
2656 bio_set_dev(bio, o->dev->bdev);
2657
2658 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2659 return DM_MAPIO_REMAPPED;
2660
2661 if (bio_data_dir(bio) != WRITE)
2662 return DM_MAPIO_REMAPPED;
2663
2664 available_sectors = o->split_boundary -
2665 ((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2666
2667 if (bio_sectors(bio) > available_sectors)
2668 dm_accept_partial_bio(bio, available_sectors);
2669
2670 /* Only tell snapshots if this is a write */
2671 return do_origin(o->dev, bio, true);
2672}
2673
2674/*
2675 * Set the target "max_io_len" field to the minimum of all the snapshots'
2676 * chunk sizes.
2677 */
2678static void origin_resume(struct dm_target *ti)
2679{
2680 struct dm_origin *o = ti->private;
2681
2682 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2683
2684 down_write(&_origins_lock);
2685 __insert_dm_origin(o);
2686 up_write(&_origins_lock);
2687}
2688
2689static void origin_postsuspend(struct dm_target *ti)
2690{
2691 struct dm_origin *o = ti->private;
2692
2693 down_write(&_origins_lock);
2694 __remove_dm_origin(o);
2695 up_write(&_origins_lock);
2696}
2697
2698static void origin_status(struct dm_target *ti, status_type_t type,
2699 unsigned status_flags, char *result, unsigned maxlen)
2700{
2701 struct dm_origin *o = ti->private;
2702
2703 switch (type) {
2704 case STATUSTYPE_INFO:
2705 result[0] = '\0';
2706 break;
2707
2708 case STATUSTYPE_TABLE:
2709 snprintf(result, maxlen, "%s", o->dev->name);
2710 break;
2711 }
2712}
2713
2714static int origin_iterate_devices(struct dm_target *ti,
2715 iterate_devices_callout_fn fn, void *data)
2716{
2717 struct dm_origin *o = ti->private;
2718
2719 return fn(ti, o->dev, 0, ti->len, data);
2720}
2721
2722static struct target_type origin_target = {
2723 .name = "snapshot-origin",
2724 .version = {1, 9, 0},
2725 .module = THIS_MODULE,
2726 .ctr = origin_ctr,
2727 .dtr = origin_dtr,
2728 .map = origin_map,
2729 .resume = origin_resume,
2730 .postsuspend = origin_postsuspend,
2731 .status = origin_status,
2732 .iterate_devices = origin_iterate_devices,
2733};
2734
2735static struct target_type snapshot_target = {
2736 .name = "snapshot",
2737 .version = {1, 16, 0},
2738 .module = THIS_MODULE,
2739 .ctr = snapshot_ctr,
2740 .dtr = snapshot_dtr,
2741 .map = snapshot_map,
2742 .end_io = snapshot_end_io,
2743 .preresume = snapshot_preresume,
2744 .resume = snapshot_resume,
2745 .status = snapshot_status,
2746 .iterate_devices = snapshot_iterate_devices,
2747 .io_hints = snapshot_io_hints,
2748};
2749
2750static struct target_type merge_target = {
2751 .name = dm_snapshot_merge_target_name,
2752 .version = {1, 5, 0},
2753 .module = THIS_MODULE,
2754 .ctr = snapshot_ctr,
2755 .dtr = snapshot_dtr,
2756 .map = snapshot_merge_map,
2757 .end_io = snapshot_end_io,
2758 .presuspend = snapshot_merge_presuspend,
2759 .preresume = snapshot_preresume,
2760 .resume = snapshot_merge_resume,
2761 .status = snapshot_status,
2762 .iterate_devices = snapshot_iterate_devices,
2763 .io_hints = snapshot_io_hints,
2764};
2765
2766static int __init dm_snapshot_init(void)
2767{
2768 int r;
2769
2770 r = dm_exception_store_init();
2771 if (r) {
2772 DMERR("Failed to initialize exception stores");
2773 return r;
2774 }
2775
2776 r = init_origin_hash();
2777 if (r) {
2778 DMERR("init_origin_hash failed.");
2779 goto bad_origin_hash;
2780 }
2781
2782 exception_cache = KMEM_CACHE(dm_exception, 0);
2783 if (!exception_cache) {
2784 DMERR("Couldn't create exception cache.");
2785 r = -ENOMEM;
2786 goto bad_exception_cache;
2787 }
2788
2789 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2790 if (!pending_cache) {
2791 DMERR("Couldn't create pending cache.");
2792 r = -ENOMEM;
2793 goto bad_pending_cache;
2794 }
2795
2796 r = dm_register_target(&snapshot_target);
2797 if (r < 0) {
2798 DMERR("snapshot target register failed %d", r);
2799 goto bad_register_snapshot_target;
2800 }
2801
2802 r = dm_register_target(&origin_target);
2803 if (r < 0) {
2804 DMERR("Origin target register failed %d", r);
2805 goto bad_register_origin_target;
2806 }
2807
2808 r = dm_register_target(&merge_target);
2809 if (r < 0) {
2810 DMERR("Merge target register failed %d", r);
2811 goto bad_register_merge_target;
2812 }
2813
2814 return 0;
2815
2816bad_register_merge_target:
2817 dm_unregister_target(&origin_target);
2818bad_register_origin_target:
2819 dm_unregister_target(&snapshot_target);
2820bad_register_snapshot_target:
2821 kmem_cache_destroy(pending_cache);
2822bad_pending_cache:
2823 kmem_cache_destroy(exception_cache);
2824bad_exception_cache:
2825 exit_origin_hash();
2826bad_origin_hash:
2827 dm_exception_store_exit();
2828
2829 return r;
2830}
2831
2832static void __exit dm_snapshot_exit(void)
2833{
2834 dm_unregister_target(&snapshot_target);
2835 dm_unregister_target(&origin_target);
2836 dm_unregister_target(&merge_target);
2837
2838 exit_origin_hash();
2839 kmem_cache_destroy(pending_cache);
2840 kmem_cache_destroy(exception_cache);
2841
2842 dm_exception_store_exit();
2843}
2844
2845/* Module hooks */
2846module_init(dm_snapshot_init);
2847module_exit(dm_snapshot_exit);
2848
2849MODULE_DESCRIPTION(DM_NAME " snapshot target");
2850MODULE_AUTHOR("Joe Thornber");
2851MODULE_LICENSE("GPL");
2852MODULE_ALIAS("dm-snapshot-origin");
2853MODULE_ALIAS("dm-snapshot-merge");