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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 = kvmalloc_array(size, sizeof(struct hlist_bl_head),
662 GFP_KERNEL);
663 if (!et->table)
664 return -ENOMEM;
665
666 for (i = 0; i < size; i++)
667 INIT_HLIST_BL_HEAD(et->table + i);
668
669 return 0;
670}
671
672static void dm_exception_table_exit(struct dm_exception_table *et,
673 struct kmem_cache *mem)
674{
675 struct hlist_bl_head *slot;
676 struct dm_exception *ex;
677 struct hlist_bl_node *pos, *n;
678 int i, size;
679
680 size = et->hash_mask + 1;
681 for (i = 0; i < size; i++) {
682 slot = et->table + i;
683
684 hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
685 kmem_cache_free(mem, ex);
686 }
687
688 kvfree(et->table);
689}
690
691static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
692{
693 return (chunk >> et->hash_shift) & et->hash_mask;
694}
695
696static void dm_remove_exception(struct dm_exception *e)
697{
698 hlist_bl_del(&e->hash_list);
699}
700
701/*
702 * Return the exception data for a sector, or NULL if not
703 * remapped.
704 */
705static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
706 chunk_t chunk)
707{
708 struct hlist_bl_head *slot;
709 struct hlist_bl_node *pos;
710 struct dm_exception *e;
711
712 slot = &et->table[exception_hash(et, chunk)];
713 hlist_bl_for_each_entry(e, pos, slot, hash_list)
714 if (chunk >= e->old_chunk &&
715 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
716 return e;
717
718 return NULL;
719}
720
721static struct dm_exception *alloc_completed_exception(gfp_t gfp)
722{
723 struct dm_exception *e;
724
725 e = kmem_cache_alloc(exception_cache, gfp);
726 if (!e && gfp == GFP_NOIO)
727 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
728
729 return e;
730}
731
732static void free_completed_exception(struct dm_exception *e)
733{
734 kmem_cache_free(exception_cache, e);
735}
736
737static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
738{
739 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
740 GFP_NOIO);
741
742 atomic_inc(&s->pending_exceptions_count);
743 pe->snap = s;
744
745 return pe;
746}
747
748static void free_pending_exception(struct dm_snap_pending_exception *pe)
749{
750 struct dm_snapshot *s = pe->snap;
751
752 mempool_free(pe, &s->pending_pool);
753 smp_mb__before_atomic();
754 atomic_dec(&s->pending_exceptions_count);
755}
756
757static void dm_insert_exception(struct dm_exception_table *eh,
758 struct dm_exception *new_e)
759{
760 struct hlist_bl_head *l;
761 struct hlist_bl_node *pos;
762 struct dm_exception *e = NULL;
763
764 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
765
766 /* Add immediately if this table doesn't support consecutive chunks */
767 if (!eh->hash_shift)
768 goto out;
769
770 /* List is ordered by old_chunk */
771 hlist_bl_for_each_entry(e, pos, l, hash_list) {
772 /* Insert after an existing chunk? */
773 if (new_e->old_chunk == (e->old_chunk +
774 dm_consecutive_chunk_count(e) + 1) &&
775 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
776 dm_consecutive_chunk_count(e) + 1)) {
777 dm_consecutive_chunk_count_inc(e);
778 free_completed_exception(new_e);
779 return;
780 }
781
782 /* Insert before an existing chunk? */
783 if (new_e->old_chunk == (e->old_chunk - 1) &&
784 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
785 dm_consecutive_chunk_count_inc(e);
786 e->old_chunk--;
787 e->new_chunk--;
788 free_completed_exception(new_e);
789 return;
790 }
791
792 if (new_e->old_chunk < e->old_chunk)
793 break;
794 }
795
796out:
797 if (!e) {
798 /*
799 * Either the table doesn't support consecutive chunks or slot
800 * l is empty.
801 */
802 hlist_bl_add_head(&new_e->hash_list, l);
803 } else if (new_e->old_chunk < e->old_chunk) {
804 /* Add before an existing exception */
805 hlist_bl_add_before(&new_e->hash_list, &e->hash_list);
806 } else {
807 /* Add to l's tail: e is the last exception in this slot */
808 hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);
809 }
810}
811
812/*
813 * Callback used by the exception stores to load exceptions when
814 * initialising.
815 */
816static int dm_add_exception(void *context, chunk_t old, chunk_t new)
817{
818 struct dm_exception_table_lock lock;
819 struct dm_snapshot *s = context;
820 struct dm_exception *e;
821
822 e = alloc_completed_exception(GFP_KERNEL);
823 if (!e)
824 return -ENOMEM;
825
826 e->old_chunk = old;
827
828 /* Consecutive_count is implicitly initialised to zero */
829 e->new_chunk = new;
830
831 /*
832 * Although there is no need to lock access to the exception tables
833 * here, if we don't then hlist_bl_add_head(), called by
834 * dm_insert_exception(), will complain about accessing the
835 * corresponding list without locking it first.
836 */
837 dm_exception_table_lock_init(s, old, &lock);
838
839 dm_exception_table_lock(&lock);
840 dm_insert_exception(&s->complete, e);
841 dm_exception_table_unlock(&lock);
842
843 return 0;
844}
845
846/*
847 * Return a minimum chunk size of all snapshots that have the specified origin.
848 * Return zero if the origin has no snapshots.
849 */
850static uint32_t __minimum_chunk_size(struct origin *o)
851{
852 struct dm_snapshot *snap;
853 unsigned chunk_size = rounddown_pow_of_two(UINT_MAX);
854
855 if (o)
856 list_for_each_entry(snap, &o->snapshots, list)
857 chunk_size = min_not_zero(chunk_size,
858 snap->store->chunk_size);
859
860 return (uint32_t) chunk_size;
861}
862
863/*
864 * Hard coded magic.
865 */
866static int calc_max_buckets(void)
867{
868 /* use a fixed size of 2MB */
869 unsigned long mem = 2 * 1024 * 1024;
870 mem /= sizeof(struct hlist_bl_head);
871
872 return mem;
873}
874
875/*
876 * Allocate room for a suitable hash table.
877 */
878static int init_hash_tables(struct dm_snapshot *s)
879{
880 sector_t hash_size, cow_dev_size, max_buckets;
881
882 /*
883 * Calculate based on the size of the original volume or
884 * the COW volume...
885 */
886 cow_dev_size = get_dev_size(s->cow->bdev);
887 max_buckets = calc_max_buckets();
888
889 hash_size = cow_dev_size >> s->store->chunk_shift;
890 hash_size = min(hash_size, max_buckets);
891
892 if (hash_size < 64)
893 hash_size = 64;
894 hash_size = rounddown_pow_of_two(hash_size);
895 if (dm_exception_table_init(&s->complete, hash_size,
896 DM_CHUNK_CONSECUTIVE_BITS))
897 return -ENOMEM;
898
899 /*
900 * Allocate hash table for in-flight exceptions
901 * Make this smaller than the real hash table
902 */
903 hash_size >>= 3;
904 if (hash_size < 64)
905 hash_size = 64;
906
907 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
908 dm_exception_table_exit(&s->complete, exception_cache);
909 return -ENOMEM;
910 }
911
912 return 0;
913}
914
915static void merge_shutdown(struct dm_snapshot *s)
916{
917 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
918 smp_mb__after_atomic();
919 wake_up_bit(&s->state_bits, RUNNING_MERGE);
920}
921
922static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
923{
924 s->first_merging_chunk = 0;
925 s->num_merging_chunks = 0;
926
927 return bio_list_get(&s->bios_queued_during_merge);
928}
929
930/*
931 * Remove one chunk from the index of completed exceptions.
932 */
933static int __remove_single_exception_chunk(struct dm_snapshot *s,
934 chunk_t old_chunk)
935{
936 struct dm_exception *e;
937
938 e = dm_lookup_exception(&s->complete, old_chunk);
939 if (!e) {
940 DMERR("Corruption detected: exception for block %llu is "
941 "on disk but not in memory",
942 (unsigned long long)old_chunk);
943 return -EINVAL;
944 }
945
946 /*
947 * If this is the only chunk using this exception, remove exception.
948 */
949 if (!dm_consecutive_chunk_count(e)) {
950 dm_remove_exception(e);
951 free_completed_exception(e);
952 return 0;
953 }
954
955 /*
956 * The chunk may be either at the beginning or the end of a
957 * group of consecutive chunks - never in the middle. We are
958 * removing chunks in the opposite order to that in which they
959 * were added, so this should always be true.
960 * Decrement the consecutive chunk counter and adjust the
961 * starting point if necessary.
962 */
963 if (old_chunk == e->old_chunk) {
964 e->old_chunk++;
965 e->new_chunk++;
966 } else if (old_chunk != e->old_chunk +
967 dm_consecutive_chunk_count(e)) {
968 DMERR("Attempt to merge block %llu from the "
969 "middle of a chunk range [%llu - %llu]",
970 (unsigned long long)old_chunk,
971 (unsigned long long)e->old_chunk,
972 (unsigned long long)
973 e->old_chunk + dm_consecutive_chunk_count(e));
974 return -EINVAL;
975 }
976
977 dm_consecutive_chunk_count_dec(e);
978
979 return 0;
980}
981
982static void flush_bios(struct bio *bio);
983
984static int remove_single_exception_chunk(struct dm_snapshot *s)
985{
986 struct bio *b = NULL;
987 int r;
988 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
989
990 down_write(&s->lock);
991
992 /*
993 * Process chunks (and associated exceptions) in reverse order
994 * so that dm_consecutive_chunk_count_dec() accounting works.
995 */
996 do {
997 r = __remove_single_exception_chunk(s, old_chunk);
998 if (r)
999 goto out;
1000 } while (old_chunk-- > s->first_merging_chunk);
1001
1002 b = __release_queued_bios_after_merge(s);
1003
1004out:
1005 up_write(&s->lock);
1006 if (b)
1007 flush_bios(b);
1008
1009 return r;
1010}
1011
1012static int origin_write_extent(struct dm_snapshot *merging_snap,
1013 sector_t sector, unsigned chunk_size);
1014
1015static void merge_callback(int read_err, unsigned long write_err,
1016 void *context);
1017
1018static uint64_t read_pending_exceptions_done_count(void)
1019{
1020 uint64_t pending_exceptions_done;
1021
1022 spin_lock(&_pending_exceptions_done_spinlock);
1023 pending_exceptions_done = _pending_exceptions_done_count;
1024 spin_unlock(&_pending_exceptions_done_spinlock);
1025
1026 return pending_exceptions_done;
1027}
1028
1029static void increment_pending_exceptions_done_count(void)
1030{
1031 spin_lock(&_pending_exceptions_done_spinlock);
1032 _pending_exceptions_done_count++;
1033 spin_unlock(&_pending_exceptions_done_spinlock);
1034
1035 wake_up_all(&_pending_exceptions_done);
1036}
1037
1038static void snapshot_merge_next_chunks(struct dm_snapshot *s)
1039{
1040 int i, linear_chunks;
1041 chunk_t old_chunk, new_chunk;
1042 struct dm_io_region src, dest;
1043 sector_t io_size;
1044 uint64_t previous_count;
1045
1046 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
1047 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
1048 goto shut;
1049
1050 /*
1051 * valid flag never changes during merge, so no lock required.
1052 */
1053 if (!s->valid) {
1054 DMERR("Snapshot is invalid: can't merge");
1055 goto shut;
1056 }
1057
1058 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
1059 &new_chunk);
1060 if (linear_chunks <= 0) {
1061 if (linear_chunks < 0) {
1062 DMERR("Read error in exception store: "
1063 "shutting down merge");
1064 down_write(&s->lock);
1065 s->merge_failed = true;
1066 up_write(&s->lock);
1067 }
1068 goto shut;
1069 }
1070
1071 /* Adjust old_chunk and new_chunk to reflect start of linear region */
1072 old_chunk = old_chunk + 1 - linear_chunks;
1073 new_chunk = new_chunk + 1 - linear_chunks;
1074
1075 /*
1076 * Use one (potentially large) I/O to copy all 'linear_chunks'
1077 * from the exception store to the origin
1078 */
1079 io_size = linear_chunks * s->store->chunk_size;
1080
1081 dest.bdev = s->origin->bdev;
1082 dest.sector = chunk_to_sector(s->store, old_chunk);
1083 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1084
1085 src.bdev = s->cow->bdev;
1086 src.sector = chunk_to_sector(s->store, new_chunk);
1087 src.count = dest.count;
1088
1089 /*
1090 * Reallocate any exceptions needed in other snapshots then
1091 * wait for the pending exceptions to complete.
1092 * Each time any pending exception (globally on the system)
1093 * completes we are woken and repeat the process to find out
1094 * if we can proceed. While this may not seem a particularly
1095 * efficient algorithm, it is not expected to have any
1096 * significant impact on performance.
1097 */
1098 previous_count = read_pending_exceptions_done_count();
1099 while (origin_write_extent(s, dest.sector, io_size)) {
1100 wait_event(_pending_exceptions_done,
1101 (read_pending_exceptions_done_count() !=
1102 previous_count));
1103 /* Retry after the wait, until all exceptions are done. */
1104 previous_count = read_pending_exceptions_done_count();
1105 }
1106
1107 down_write(&s->lock);
1108 s->first_merging_chunk = old_chunk;
1109 s->num_merging_chunks = linear_chunks;
1110 up_write(&s->lock);
1111
1112 /* Wait until writes to all 'linear_chunks' drain */
1113 for (i = 0; i < linear_chunks; i++)
1114 __check_for_conflicting_io(s, old_chunk + i);
1115
1116 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1117 return;
1118
1119shut:
1120 merge_shutdown(s);
1121}
1122
1123static void error_bios(struct bio *bio);
1124
1125static void merge_callback(int read_err, unsigned long write_err, void *context)
1126{
1127 struct dm_snapshot *s = context;
1128 struct bio *b = NULL;
1129
1130 if (read_err || write_err) {
1131 if (read_err)
1132 DMERR("Read error: shutting down merge.");
1133 else
1134 DMERR("Write error: shutting down merge.");
1135 goto shut;
1136 }
1137
1138 if (blkdev_issue_flush(s->origin->bdev) < 0) {
1139 DMERR("Flush after merge failed: shutting down merge");
1140 goto shut;
1141 }
1142
1143 if (s->store->type->commit_merge(s->store,
1144 s->num_merging_chunks) < 0) {
1145 DMERR("Write error in exception store: shutting down merge");
1146 goto shut;
1147 }
1148
1149 if (remove_single_exception_chunk(s) < 0)
1150 goto shut;
1151
1152 snapshot_merge_next_chunks(s);
1153
1154 return;
1155
1156shut:
1157 down_write(&s->lock);
1158 s->merge_failed = true;
1159 b = __release_queued_bios_after_merge(s);
1160 up_write(&s->lock);
1161 error_bios(b);
1162
1163 merge_shutdown(s);
1164}
1165
1166static void start_merge(struct dm_snapshot *s)
1167{
1168 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1169 snapshot_merge_next_chunks(s);
1170}
1171
1172/*
1173 * Stop the merging process and wait until it finishes.
1174 */
1175static void stop_merge(struct dm_snapshot *s)
1176{
1177 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1178 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1179 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1180}
1181
1182static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,
1183 struct dm_target *ti)
1184{
1185 int r;
1186 unsigned argc;
1187 const char *arg_name;
1188
1189 static const struct dm_arg _args[] = {
1190 {0, 2, "Invalid number of feature arguments"},
1191 };
1192
1193 /*
1194 * No feature arguments supplied.
1195 */
1196 if (!as->argc)
1197 return 0;
1198
1199 r = dm_read_arg_group(_args, as, &argc, &ti->error);
1200 if (r)
1201 return -EINVAL;
1202
1203 while (argc && !r) {
1204 arg_name = dm_shift_arg(as);
1205 argc--;
1206
1207 if (!strcasecmp(arg_name, "discard_zeroes_cow"))
1208 s->discard_zeroes_cow = true;
1209
1210 else if (!strcasecmp(arg_name, "discard_passdown_origin"))
1211 s->discard_passdown_origin = true;
1212
1213 else {
1214 ti->error = "Unrecognised feature requested";
1215 r = -EINVAL;
1216 break;
1217 }
1218 }
1219
1220 if (!s->discard_zeroes_cow && s->discard_passdown_origin) {
1221 /*
1222 * TODO: really these are disjoint.. but ti->num_discard_bios
1223 * and dm_bio_get_target_bio_nr() require rigid constraints.
1224 */
1225 ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";
1226 r = -EINVAL;
1227 }
1228
1229 return r;
1230}
1231
1232/*
1233 * Construct a snapshot mapping:
1234 * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]
1235 */
1236static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1237{
1238 struct dm_snapshot *s;
1239 struct dm_arg_set as;
1240 int i;
1241 int r = -EINVAL;
1242 char *origin_path, *cow_path;
1243 dev_t origin_dev, cow_dev;
1244 unsigned args_used, num_flush_bios = 1;
1245 fmode_t origin_mode = FMODE_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 = FMODE_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 origin_dev = s->origin->bdev->bd_dev;
1282
1283 cow_path = argv[0];
1284 argv++;
1285 argc--;
1286
1287 cow_dev = dm_get_dev_t(cow_path);
1288 if (cow_dev && cow_dev == origin_dev) {
1289 ti->error = "COW device cannot be the same as origin device";
1290 r = -EINVAL;
1291 goto bad_cow;
1292 }
1293
1294 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1295 if (r) {
1296 ti->error = "Cannot get COW device";
1297 goto bad_cow;
1298 }
1299
1300 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1301 if (r) {
1302 ti->error = "Couldn't create exception store";
1303 r = -EINVAL;
1304 goto bad_store;
1305 }
1306
1307 argv += args_used;
1308 argc -= args_used;
1309
1310 s->ti = ti;
1311 s->valid = 1;
1312 s->snapshot_overflowed = 0;
1313 s->active = 0;
1314 atomic_set(&s->pending_exceptions_count, 0);
1315 spin_lock_init(&s->pe_allocation_lock);
1316 s->exception_start_sequence = 0;
1317 s->exception_complete_sequence = 0;
1318 s->out_of_order_tree = RB_ROOT;
1319 init_rwsem(&s->lock);
1320 INIT_LIST_HEAD(&s->list);
1321 spin_lock_init(&s->pe_lock);
1322 s->state_bits = 0;
1323 s->merge_failed = false;
1324 s->first_merging_chunk = 0;
1325 s->num_merging_chunks = 0;
1326 bio_list_init(&s->bios_queued_during_merge);
1327
1328 /* Allocate hash table for COW data */
1329 if (init_hash_tables(s)) {
1330 ti->error = "Unable to allocate hash table space";
1331 r = -ENOMEM;
1332 goto bad_hash_tables;
1333 }
1334
1335 init_waitqueue_head(&s->in_progress_wait);
1336
1337 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1338 if (IS_ERR(s->kcopyd_client)) {
1339 r = PTR_ERR(s->kcopyd_client);
1340 ti->error = "Could not create kcopyd client";
1341 goto bad_kcopyd;
1342 }
1343
1344 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
1345 if (r) {
1346 ti->error = "Could not allocate mempool for pending exceptions";
1347 goto bad_pending_pool;
1348 }
1349
1350 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1351 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1352
1353 spin_lock_init(&s->tracked_chunk_lock);
1354
1355 ti->private = s;
1356 ti->num_flush_bios = num_flush_bios;
1357 if (s->discard_zeroes_cow)
1358 ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
1359 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1360
1361 /* Add snapshot to the list of snapshots for this origin */
1362 /* Exceptions aren't triggered till snapshot_resume() is called */
1363 r = register_snapshot(s);
1364 if (r == -ENOMEM) {
1365 ti->error = "Snapshot origin struct allocation failed";
1366 goto bad_load_and_register;
1367 } else if (r < 0) {
1368 /* invalid handover, register_snapshot has set ti->error */
1369 goto bad_load_and_register;
1370 }
1371
1372 /*
1373 * Metadata must only be loaded into one table at once, so skip this
1374 * if metadata will be handed over during resume.
1375 * Chunk size will be set during the handover - set it to zero to
1376 * ensure it's ignored.
1377 */
1378 if (r > 0) {
1379 s->store->chunk_size = 0;
1380 return 0;
1381 }
1382
1383 r = s->store->type->read_metadata(s->store, dm_add_exception,
1384 (void *)s);
1385 if (r < 0) {
1386 ti->error = "Failed to read snapshot metadata";
1387 goto bad_read_metadata;
1388 } else if (r > 0) {
1389 s->valid = 0;
1390 DMWARN("Snapshot is marked invalid.");
1391 }
1392
1393 if (!s->store->chunk_size) {
1394 ti->error = "Chunk size not set";
1395 r = -EINVAL;
1396 goto bad_read_metadata;
1397 }
1398
1399 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1400 if (r)
1401 goto bad_read_metadata;
1402
1403 return 0;
1404
1405bad_read_metadata:
1406 unregister_snapshot(s);
1407bad_load_and_register:
1408 mempool_exit(&s->pending_pool);
1409bad_pending_pool:
1410 dm_kcopyd_client_destroy(s->kcopyd_client);
1411bad_kcopyd:
1412 dm_exception_table_exit(&s->pending, pending_cache);
1413 dm_exception_table_exit(&s->complete, exception_cache);
1414bad_hash_tables:
1415 dm_exception_store_destroy(s->store);
1416bad_store:
1417 dm_put_device(ti, s->cow);
1418bad_cow:
1419 dm_put_device(ti, s->origin);
1420bad_origin:
1421bad_features:
1422 kfree(s);
1423bad:
1424 return r;
1425}
1426
1427static void __free_exceptions(struct dm_snapshot *s)
1428{
1429 dm_kcopyd_client_destroy(s->kcopyd_client);
1430 s->kcopyd_client = NULL;
1431
1432 dm_exception_table_exit(&s->pending, pending_cache);
1433 dm_exception_table_exit(&s->complete, exception_cache);
1434}
1435
1436static void __handover_exceptions(struct dm_snapshot *snap_src,
1437 struct dm_snapshot *snap_dest)
1438{
1439 union {
1440 struct dm_exception_table table_swap;
1441 struct dm_exception_store *store_swap;
1442 } u;
1443
1444 /*
1445 * Swap all snapshot context information between the two instances.
1446 */
1447 u.table_swap = snap_dest->complete;
1448 snap_dest->complete = snap_src->complete;
1449 snap_src->complete = u.table_swap;
1450
1451 u.store_swap = snap_dest->store;
1452 snap_dest->store = snap_src->store;
1453 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1454 snap_src->store = u.store_swap;
1455
1456 snap_dest->store->snap = snap_dest;
1457 snap_src->store->snap = snap_src;
1458
1459 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1460 snap_dest->valid = snap_src->valid;
1461 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1462
1463 /*
1464 * Set source invalid to ensure it receives no further I/O.
1465 */
1466 snap_src->valid = 0;
1467}
1468
1469static void snapshot_dtr(struct dm_target *ti)
1470{
1471#ifdef CONFIG_DM_DEBUG
1472 int i;
1473#endif
1474 struct dm_snapshot *s = ti->private;
1475 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1476
1477 down_read(&_origins_lock);
1478 /* Check whether exception handover must be cancelled */
1479 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1480 if (snap_src && snap_dest && (s == snap_src)) {
1481 down_write(&snap_dest->lock);
1482 snap_dest->valid = 0;
1483 up_write(&snap_dest->lock);
1484 DMERR("Cancelling snapshot handover.");
1485 }
1486 up_read(&_origins_lock);
1487
1488 if (dm_target_is_snapshot_merge(ti))
1489 stop_merge(s);
1490
1491 /* Prevent further origin writes from using this snapshot. */
1492 /* After this returns there can be no new kcopyd jobs. */
1493 unregister_snapshot(s);
1494
1495 while (atomic_read(&s->pending_exceptions_count))
1496 msleep(1);
1497 /*
1498 * Ensure instructions in mempool_exit aren't reordered
1499 * before atomic_read.
1500 */
1501 smp_mb();
1502
1503#ifdef CONFIG_DM_DEBUG
1504 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1505 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1506#endif
1507
1508 __free_exceptions(s);
1509
1510 mempool_exit(&s->pending_pool);
1511
1512 dm_exception_store_destroy(s->store);
1513
1514 dm_put_device(ti, s->cow);
1515
1516 dm_put_device(ti, s->origin);
1517
1518 WARN_ON(s->in_progress);
1519
1520 kfree(s);
1521}
1522
1523static void account_start_copy(struct dm_snapshot *s)
1524{
1525 spin_lock(&s->in_progress_wait.lock);
1526 s->in_progress++;
1527 spin_unlock(&s->in_progress_wait.lock);
1528}
1529
1530static void account_end_copy(struct dm_snapshot *s)
1531{
1532 spin_lock(&s->in_progress_wait.lock);
1533 BUG_ON(!s->in_progress);
1534 s->in_progress--;
1535 if (likely(s->in_progress <= cow_threshold) &&
1536 unlikely(waitqueue_active(&s->in_progress_wait)))
1537 wake_up_locked(&s->in_progress_wait);
1538 spin_unlock(&s->in_progress_wait.lock);
1539}
1540
1541static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
1542{
1543 if (unlikely(s->in_progress > cow_threshold)) {
1544 spin_lock(&s->in_progress_wait.lock);
1545 if (likely(s->in_progress > cow_threshold)) {
1546 /*
1547 * NOTE: this throttle doesn't account for whether
1548 * the caller is servicing an IO that will trigger a COW
1549 * so excess throttling may result for chunks not required
1550 * to be COW'd. But if cow_threshold was reached, extra
1551 * throttling is unlikely to negatively impact performance.
1552 */
1553 DECLARE_WAITQUEUE(wait, current);
1554 __add_wait_queue(&s->in_progress_wait, &wait);
1555 __set_current_state(TASK_UNINTERRUPTIBLE);
1556 spin_unlock(&s->in_progress_wait.lock);
1557 if (unlock_origins)
1558 up_read(&_origins_lock);
1559 io_schedule();
1560 remove_wait_queue(&s->in_progress_wait, &wait);
1561 return false;
1562 }
1563 spin_unlock(&s->in_progress_wait.lock);
1564 }
1565 return true;
1566}
1567
1568/*
1569 * Flush a list of buffers.
1570 */
1571static void flush_bios(struct bio *bio)
1572{
1573 struct bio *n;
1574
1575 while (bio) {
1576 n = bio->bi_next;
1577 bio->bi_next = NULL;
1578 submit_bio_noacct(bio);
1579 bio = n;
1580 }
1581}
1582
1583static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
1584
1585/*
1586 * Flush a list of buffers.
1587 */
1588static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1589{
1590 struct bio *n;
1591 int r;
1592
1593 while (bio) {
1594 n = bio->bi_next;
1595 bio->bi_next = NULL;
1596 r = do_origin(s->origin, bio, false);
1597 if (r == DM_MAPIO_REMAPPED)
1598 submit_bio_noacct(bio);
1599 bio = n;
1600 }
1601}
1602
1603/*
1604 * Error a list of buffers.
1605 */
1606static void error_bios(struct bio *bio)
1607{
1608 struct bio *n;
1609
1610 while (bio) {
1611 n = bio->bi_next;
1612 bio->bi_next = NULL;
1613 bio_io_error(bio);
1614 bio = n;
1615 }
1616}
1617
1618static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1619{
1620 if (!s->valid)
1621 return;
1622
1623 if (err == -EIO)
1624 DMERR("Invalidating snapshot: Error reading/writing.");
1625 else if (err == -ENOMEM)
1626 DMERR("Invalidating snapshot: Unable to allocate exception.");
1627
1628 if (s->store->type->drop_snapshot)
1629 s->store->type->drop_snapshot(s->store);
1630
1631 s->valid = 0;
1632
1633 dm_table_event(s->ti->table);
1634}
1635
1636static void invalidate_snapshot(struct dm_snapshot *s, int err)
1637{
1638 down_write(&s->lock);
1639 __invalidate_snapshot(s, err);
1640 up_write(&s->lock);
1641}
1642
1643static void pending_complete(void *context, int success)
1644{
1645 struct dm_snap_pending_exception *pe = context;
1646 struct dm_exception *e;
1647 struct dm_snapshot *s = pe->snap;
1648 struct bio *origin_bios = NULL;
1649 struct bio *snapshot_bios = NULL;
1650 struct bio *full_bio = NULL;
1651 struct dm_exception_table_lock lock;
1652 int error = 0;
1653
1654 dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);
1655
1656 if (!success) {
1657 /* Read/write error - snapshot is unusable */
1658 invalidate_snapshot(s, -EIO);
1659 error = 1;
1660
1661 dm_exception_table_lock(&lock);
1662 goto out;
1663 }
1664
1665 e = alloc_completed_exception(GFP_NOIO);
1666 if (!e) {
1667 invalidate_snapshot(s, -ENOMEM);
1668 error = 1;
1669
1670 dm_exception_table_lock(&lock);
1671 goto out;
1672 }
1673 *e = pe->e;
1674
1675 down_read(&s->lock);
1676 dm_exception_table_lock(&lock);
1677 if (!s->valid) {
1678 up_read(&s->lock);
1679 free_completed_exception(e);
1680 error = 1;
1681
1682 goto out;
1683 }
1684
1685 /*
1686 * Add a proper exception. After inserting the completed exception all
1687 * subsequent snapshot reads to this chunk will be redirected to the
1688 * COW device. This ensures that we do not starve. Moreover, as long
1689 * as the pending exception exists, neither origin writes nor snapshot
1690 * merging can overwrite the chunk in origin.
1691 */
1692 dm_insert_exception(&s->complete, e);
1693 up_read(&s->lock);
1694
1695 /* Wait for conflicting reads to drain */
1696 if (__chunk_is_tracked(s, pe->e.old_chunk)) {
1697 dm_exception_table_unlock(&lock);
1698 __check_for_conflicting_io(s, pe->e.old_chunk);
1699 dm_exception_table_lock(&lock);
1700 }
1701
1702out:
1703 /* Remove the in-flight exception from the list */
1704 dm_remove_exception(&pe->e);
1705
1706 dm_exception_table_unlock(&lock);
1707
1708 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1709 origin_bios = bio_list_get(&pe->origin_bios);
1710 full_bio = pe->full_bio;
1711 if (full_bio)
1712 full_bio->bi_end_io = pe->full_bio_end_io;
1713 increment_pending_exceptions_done_count();
1714
1715 /* Submit any pending write bios */
1716 if (error) {
1717 if (full_bio)
1718 bio_io_error(full_bio);
1719 error_bios(snapshot_bios);
1720 } else {
1721 if (full_bio)
1722 bio_endio(full_bio);
1723 flush_bios(snapshot_bios);
1724 }
1725
1726 retry_origin_bios(s, origin_bios);
1727
1728 free_pending_exception(pe);
1729}
1730
1731static void complete_exception(struct dm_snap_pending_exception *pe)
1732{
1733 struct dm_snapshot *s = pe->snap;
1734
1735 /* Update the metadata if we are persistent */
1736 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1737 pending_complete, pe);
1738}
1739
1740/*
1741 * Called when the copy I/O has finished. kcopyd actually runs
1742 * this code so don't block.
1743 */
1744static void copy_callback(int read_err, unsigned long write_err, void *context)
1745{
1746 struct dm_snap_pending_exception *pe = context;
1747 struct dm_snapshot *s = pe->snap;
1748
1749 pe->copy_error = read_err || write_err;
1750
1751 if (pe->exception_sequence == s->exception_complete_sequence) {
1752 struct rb_node *next;
1753
1754 s->exception_complete_sequence++;
1755 complete_exception(pe);
1756
1757 next = rb_first(&s->out_of_order_tree);
1758 while (next) {
1759 pe = rb_entry(next, struct dm_snap_pending_exception,
1760 out_of_order_node);
1761 if (pe->exception_sequence != s->exception_complete_sequence)
1762 break;
1763 next = rb_next(next);
1764 s->exception_complete_sequence++;
1765 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
1766 complete_exception(pe);
1767 cond_resched();
1768 }
1769 } else {
1770 struct rb_node *parent = NULL;
1771 struct rb_node **p = &s->out_of_order_tree.rb_node;
1772 struct dm_snap_pending_exception *pe2;
1773
1774 while (*p) {
1775 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
1776 parent = *p;
1777
1778 BUG_ON(pe->exception_sequence == pe2->exception_sequence);
1779 if (pe->exception_sequence < pe2->exception_sequence)
1780 p = &((*p)->rb_left);
1781 else
1782 p = &((*p)->rb_right);
1783 }
1784
1785 rb_link_node(&pe->out_of_order_node, parent, p);
1786 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
1787 }
1788 account_end_copy(s);
1789}
1790
1791/*
1792 * Dispatches the copy operation to kcopyd.
1793 */
1794static void start_copy(struct dm_snap_pending_exception *pe)
1795{
1796 struct dm_snapshot *s = pe->snap;
1797 struct dm_io_region src, dest;
1798 struct block_device *bdev = s->origin->bdev;
1799 sector_t dev_size;
1800
1801 dev_size = get_dev_size(bdev);
1802
1803 src.bdev = bdev;
1804 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1805 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1806
1807 dest.bdev = s->cow->bdev;
1808 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1809 dest.count = src.count;
1810
1811 /* Hand over to kcopyd */
1812 account_start_copy(s);
1813 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1814}
1815
1816static void full_bio_end_io(struct bio *bio)
1817{
1818 void *callback_data = bio->bi_private;
1819
1820 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
1821}
1822
1823static void start_full_bio(struct dm_snap_pending_exception *pe,
1824 struct bio *bio)
1825{
1826 struct dm_snapshot *s = pe->snap;
1827 void *callback_data;
1828
1829 pe->full_bio = bio;
1830 pe->full_bio_end_io = bio->bi_end_io;
1831
1832 account_start_copy(s);
1833 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1834 copy_callback, pe);
1835
1836 bio->bi_end_io = full_bio_end_io;
1837 bio->bi_private = callback_data;
1838
1839 submit_bio_noacct(bio);
1840}
1841
1842static struct dm_snap_pending_exception *
1843__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1844{
1845 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1846
1847 if (!e)
1848 return NULL;
1849
1850 return container_of(e, struct dm_snap_pending_exception, e);
1851}
1852
1853/*
1854 * Inserts a pending exception into the pending table.
1855 *
1856 * NOTE: a write lock must be held on the chunk's pending exception table slot
1857 * before calling this.
1858 */
1859static struct dm_snap_pending_exception *
1860__insert_pending_exception(struct dm_snapshot *s,
1861 struct dm_snap_pending_exception *pe, chunk_t chunk)
1862{
1863 pe->e.old_chunk = chunk;
1864 bio_list_init(&pe->origin_bios);
1865 bio_list_init(&pe->snapshot_bios);
1866 pe->started = 0;
1867 pe->full_bio = NULL;
1868
1869 spin_lock(&s->pe_allocation_lock);
1870 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1871 spin_unlock(&s->pe_allocation_lock);
1872 free_pending_exception(pe);
1873 return NULL;
1874 }
1875
1876 pe->exception_sequence = s->exception_start_sequence++;
1877 spin_unlock(&s->pe_allocation_lock);
1878
1879 dm_insert_exception(&s->pending, &pe->e);
1880
1881 return pe;
1882}
1883
1884/*
1885 * Looks to see if this snapshot already has a pending exception
1886 * for this chunk, otherwise it allocates a new one and inserts
1887 * it into the pending table.
1888 *
1889 * NOTE: a write lock must be held on the chunk's pending exception table slot
1890 * before calling this.
1891 */
1892static struct dm_snap_pending_exception *
1893__find_pending_exception(struct dm_snapshot *s,
1894 struct dm_snap_pending_exception *pe, chunk_t chunk)
1895{
1896 struct dm_snap_pending_exception *pe2;
1897
1898 pe2 = __lookup_pending_exception(s, chunk);
1899 if (pe2) {
1900 free_pending_exception(pe);
1901 return pe2;
1902 }
1903
1904 return __insert_pending_exception(s, pe, chunk);
1905}
1906
1907static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1908 struct bio *bio, chunk_t chunk)
1909{
1910 bio_set_dev(bio, s->cow->bdev);
1911 bio->bi_iter.bi_sector =
1912 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1913 (chunk - e->old_chunk)) +
1914 (bio->bi_iter.bi_sector & s->store->chunk_mask);
1915}
1916
1917static void zero_callback(int read_err, unsigned long write_err, void *context)
1918{
1919 struct bio *bio = context;
1920 struct dm_snapshot *s = bio->bi_private;
1921
1922 account_end_copy(s);
1923 bio->bi_status = write_err ? BLK_STS_IOERR : 0;
1924 bio_endio(bio);
1925}
1926
1927static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
1928 struct bio *bio, chunk_t chunk)
1929{
1930 struct dm_io_region dest;
1931
1932 dest.bdev = s->cow->bdev;
1933 dest.sector = bio->bi_iter.bi_sector;
1934 dest.count = s->store->chunk_size;
1935
1936 account_start_copy(s);
1937 WARN_ON_ONCE(bio->bi_private);
1938 bio->bi_private = s;
1939 dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
1940}
1941
1942static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)
1943{
1944 return bio->bi_iter.bi_size ==
1945 (s->store->chunk_size << SECTOR_SHIFT);
1946}
1947
1948static int snapshot_map(struct dm_target *ti, struct bio *bio)
1949{
1950 struct dm_exception *e;
1951 struct dm_snapshot *s = ti->private;
1952 int r = DM_MAPIO_REMAPPED;
1953 chunk_t chunk;
1954 struct dm_snap_pending_exception *pe = NULL;
1955 struct dm_exception_table_lock lock;
1956
1957 init_tracked_chunk(bio);
1958
1959 if (bio->bi_opf & REQ_PREFLUSH) {
1960 bio_set_dev(bio, s->cow->bdev);
1961 return DM_MAPIO_REMAPPED;
1962 }
1963
1964 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1965 dm_exception_table_lock_init(s, chunk, &lock);
1966
1967 /* Full snapshots are not usable */
1968 /* To get here the table must be live so s->active is always set. */
1969 if (!s->valid)
1970 return DM_MAPIO_KILL;
1971
1972 if (bio_data_dir(bio) == WRITE) {
1973 while (unlikely(!wait_for_in_progress(s, false)))
1974 ; /* wait_for_in_progress() has slept */
1975 }
1976
1977 down_read(&s->lock);
1978 dm_exception_table_lock(&lock);
1979
1980 if (!s->valid || (unlikely(s->snapshot_overflowed) &&
1981 bio_data_dir(bio) == WRITE)) {
1982 r = DM_MAPIO_KILL;
1983 goto out_unlock;
1984 }
1985
1986 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
1987 if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {
1988 /*
1989 * passdown discard to origin (without triggering
1990 * snapshot exceptions via do_origin; doing so would
1991 * defeat the goal of freeing space in origin that is
1992 * implied by the "discard_passdown_origin" feature)
1993 */
1994 bio_set_dev(bio, s->origin->bdev);
1995 track_chunk(s, bio, chunk);
1996 goto out_unlock;
1997 }
1998 /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */
1999 }
2000
2001 /* If the block is already remapped - use that, else remap it */
2002 e = dm_lookup_exception(&s->complete, chunk);
2003 if (e) {
2004 remap_exception(s, e, bio, chunk);
2005 if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
2006 io_overlaps_chunk(s, bio)) {
2007 dm_exception_table_unlock(&lock);
2008 up_read(&s->lock);
2009 zero_exception(s, e, bio, chunk);
2010 r = DM_MAPIO_SUBMITTED; /* discard is not issued */
2011 goto out;
2012 }
2013 goto out_unlock;
2014 }
2015
2016 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2017 /*
2018 * If no exception exists, complete discard immediately
2019 * otherwise it'll trigger copy-out.
2020 */
2021 bio_endio(bio);
2022 r = DM_MAPIO_SUBMITTED;
2023 goto out_unlock;
2024 }
2025
2026 /*
2027 * Write to snapshot - higher level takes care of RW/RO
2028 * flags so we should only get this if we are
2029 * writable.
2030 */
2031 if (bio_data_dir(bio) == WRITE) {
2032 pe = __lookup_pending_exception(s, chunk);
2033 if (!pe) {
2034 dm_exception_table_unlock(&lock);
2035 pe = alloc_pending_exception(s);
2036 dm_exception_table_lock(&lock);
2037
2038 e = dm_lookup_exception(&s->complete, chunk);
2039 if (e) {
2040 free_pending_exception(pe);
2041 remap_exception(s, e, bio, chunk);
2042 goto out_unlock;
2043 }
2044
2045 pe = __find_pending_exception(s, pe, chunk);
2046 if (!pe) {
2047 dm_exception_table_unlock(&lock);
2048 up_read(&s->lock);
2049
2050 down_write(&s->lock);
2051
2052 if (s->store->userspace_supports_overflow) {
2053 if (s->valid && !s->snapshot_overflowed) {
2054 s->snapshot_overflowed = 1;
2055 DMERR("Snapshot overflowed: Unable to allocate exception.");
2056 }
2057 } else
2058 __invalidate_snapshot(s, -ENOMEM);
2059 up_write(&s->lock);
2060
2061 r = DM_MAPIO_KILL;
2062 goto out;
2063 }
2064 }
2065
2066 remap_exception(s, &pe->e, bio, chunk);
2067
2068 r = DM_MAPIO_SUBMITTED;
2069
2070 if (!pe->started && io_overlaps_chunk(s, bio)) {
2071 pe->started = 1;
2072
2073 dm_exception_table_unlock(&lock);
2074 up_read(&s->lock);
2075
2076 start_full_bio(pe, bio);
2077 goto out;
2078 }
2079
2080 bio_list_add(&pe->snapshot_bios, bio);
2081
2082 if (!pe->started) {
2083 /* this is protected by the exception table lock */
2084 pe->started = 1;
2085
2086 dm_exception_table_unlock(&lock);
2087 up_read(&s->lock);
2088
2089 start_copy(pe);
2090 goto out;
2091 }
2092 } else {
2093 bio_set_dev(bio, s->origin->bdev);
2094 track_chunk(s, bio, chunk);
2095 }
2096
2097out_unlock:
2098 dm_exception_table_unlock(&lock);
2099 up_read(&s->lock);
2100out:
2101 return r;
2102}
2103
2104/*
2105 * A snapshot-merge target behaves like a combination of a snapshot
2106 * target and a snapshot-origin target. It only generates new
2107 * exceptions in other snapshots and not in the one that is being
2108 * merged.
2109 *
2110 * For each chunk, if there is an existing exception, it is used to
2111 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
2112 * which in turn might generate exceptions in other snapshots.
2113 * If merging is currently taking place on the chunk in question, the
2114 * I/O is deferred by adding it to s->bios_queued_during_merge.
2115 */
2116static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
2117{
2118 struct dm_exception *e;
2119 struct dm_snapshot *s = ti->private;
2120 int r = DM_MAPIO_REMAPPED;
2121 chunk_t chunk;
2122
2123 init_tracked_chunk(bio);
2124
2125 if (bio->bi_opf & REQ_PREFLUSH) {
2126 if (!dm_bio_get_target_bio_nr(bio))
2127 bio_set_dev(bio, s->origin->bdev);
2128 else
2129 bio_set_dev(bio, s->cow->bdev);
2130 return DM_MAPIO_REMAPPED;
2131 }
2132
2133 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2134 /* Once merging, discards no longer effect change */
2135 bio_endio(bio);
2136 return DM_MAPIO_SUBMITTED;
2137 }
2138
2139 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
2140
2141 down_write(&s->lock);
2142
2143 /* Full merging snapshots are redirected to the origin */
2144 if (!s->valid)
2145 goto redirect_to_origin;
2146
2147 /* If the block is already remapped - use that */
2148 e = dm_lookup_exception(&s->complete, chunk);
2149 if (e) {
2150 /* Queue writes overlapping with chunks being merged */
2151 if (bio_data_dir(bio) == WRITE &&
2152 chunk >= s->first_merging_chunk &&
2153 chunk < (s->first_merging_chunk +
2154 s->num_merging_chunks)) {
2155 bio_set_dev(bio, s->origin->bdev);
2156 bio_list_add(&s->bios_queued_during_merge, bio);
2157 r = DM_MAPIO_SUBMITTED;
2158 goto out_unlock;
2159 }
2160
2161 remap_exception(s, e, bio, chunk);
2162
2163 if (bio_data_dir(bio) == WRITE)
2164 track_chunk(s, bio, chunk);
2165 goto out_unlock;
2166 }
2167
2168redirect_to_origin:
2169 bio_set_dev(bio, s->origin->bdev);
2170
2171 if (bio_data_dir(bio) == WRITE) {
2172 up_write(&s->lock);
2173 return do_origin(s->origin, bio, false);
2174 }
2175
2176out_unlock:
2177 up_write(&s->lock);
2178
2179 return r;
2180}
2181
2182static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
2183 blk_status_t *error)
2184{
2185 struct dm_snapshot *s = ti->private;
2186
2187 if (is_bio_tracked(bio))
2188 stop_tracking_chunk(s, bio);
2189
2190 return DM_ENDIO_DONE;
2191}
2192
2193static void snapshot_merge_presuspend(struct dm_target *ti)
2194{
2195 struct dm_snapshot *s = ti->private;
2196
2197 stop_merge(s);
2198}
2199
2200static int snapshot_preresume(struct dm_target *ti)
2201{
2202 int r = 0;
2203 struct dm_snapshot *s = ti->private;
2204 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2205
2206 down_read(&_origins_lock);
2207 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2208 if (snap_src && snap_dest) {
2209 down_read(&snap_src->lock);
2210 if (s == snap_src) {
2211 DMERR("Unable to resume snapshot source until "
2212 "handover completes.");
2213 r = -EINVAL;
2214 } else if (!dm_suspended(snap_src->ti)) {
2215 DMERR("Unable to perform snapshot handover until "
2216 "source is suspended.");
2217 r = -EINVAL;
2218 }
2219 up_read(&snap_src->lock);
2220 }
2221 up_read(&_origins_lock);
2222
2223 return r;
2224}
2225
2226static void snapshot_resume(struct dm_target *ti)
2227{
2228 struct dm_snapshot *s = ti->private;
2229 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
2230 struct dm_origin *o;
2231 struct mapped_device *origin_md = NULL;
2232 bool must_restart_merging = false;
2233
2234 down_read(&_origins_lock);
2235
2236 o = __lookup_dm_origin(s->origin->bdev);
2237 if (o)
2238 origin_md = dm_table_get_md(o->ti->table);
2239 if (!origin_md) {
2240 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
2241 if (snap_merging)
2242 origin_md = dm_table_get_md(snap_merging->ti->table);
2243 }
2244 if (origin_md == dm_table_get_md(ti->table))
2245 origin_md = NULL;
2246 if (origin_md) {
2247 if (dm_hold(origin_md))
2248 origin_md = NULL;
2249 }
2250
2251 up_read(&_origins_lock);
2252
2253 if (origin_md) {
2254 dm_internal_suspend_fast(origin_md);
2255 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
2256 must_restart_merging = true;
2257 stop_merge(snap_merging);
2258 }
2259 }
2260
2261 down_read(&_origins_lock);
2262
2263 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2264 if (snap_src && snap_dest) {
2265 down_write(&snap_src->lock);
2266 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
2267 __handover_exceptions(snap_src, snap_dest);
2268 up_write(&snap_dest->lock);
2269 up_write(&snap_src->lock);
2270 }
2271
2272 up_read(&_origins_lock);
2273
2274 if (origin_md) {
2275 if (must_restart_merging)
2276 start_merge(snap_merging);
2277 dm_internal_resume_fast(origin_md);
2278 dm_put(origin_md);
2279 }
2280
2281 /* Now we have correct chunk size, reregister */
2282 reregister_snapshot(s);
2283
2284 down_write(&s->lock);
2285 s->active = 1;
2286 up_write(&s->lock);
2287}
2288
2289static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
2290{
2291 uint32_t min_chunksize;
2292
2293 down_read(&_origins_lock);
2294 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
2295 up_read(&_origins_lock);
2296
2297 return min_chunksize;
2298}
2299
2300static void snapshot_merge_resume(struct dm_target *ti)
2301{
2302 struct dm_snapshot *s = ti->private;
2303
2304 /*
2305 * Handover exceptions from existing snapshot.
2306 */
2307 snapshot_resume(ti);
2308
2309 /*
2310 * snapshot-merge acts as an origin, so set ti->max_io_len
2311 */
2312 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
2313
2314 start_merge(s);
2315}
2316
2317static void snapshot_status(struct dm_target *ti, status_type_t type,
2318 unsigned status_flags, char *result, unsigned maxlen)
2319{
2320 unsigned sz = 0;
2321 struct dm_snapshot *snap = ti->private;
2322 unsigned num_features;
2323
2324 switch (type) {
2325 case STATUSTYPE_INFO:
2326
2327 down_write(&snap->lock);
2328
2329 if (!snap->valid)
2330 DMEMIT("Invalid");
2331 else if (snap->merge_failed)
2332 DMEMIT("Merge failed");
2333 else if (snap->snapshot_overflowed)
2334 DMEMIT("Overflow");
2335 else {
2336 if (snap->store->type->usage) {
2337 sector_t total_sectors, sectors_allocated,
2338 metadata_sectors;
2339 snap->store->type->usage(snap->store,
2340 &total_sectors,
2341 §ors_allocated,
2342 &metadata_sectors);
2343 DMEMIT("%llu/%llu %llu",
2344 (unsigned long long)sectors_allocated,
2345 (unsigned long long)total_sectors,
2346 (unsigned long long)metadata_sectors);
2347 }
2348 else
2349 DMEMIT("Unknown");
2350 }
2351
2352 up_write(&snap->lock);
2353
2354 break;
2355
2356 case STATUSTYPE_TABLE:
2357 /*
2358 * kdevname returns a static pointer so we need
2359 * to make private copies if the output is to
2360 * make sense.
2361 */
2362 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2363 sz += snap->store->type->status(snap->store, type, result + sz,
2364 maxlen - sz);
2365 num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;
2366 if (num_features) {
2367 DMEMIT(" %u", num_features);
2368 if (snap->discard_zeroes_cow)
2369 DMEMIT(" discard_zeroes_cow");
2370 if (snap->discard_passdown_origin)
2371 DMEMIT(" discard_passdown_origin");
2372 }
2373 break;
2374
2375 case STATUSTYPE_IMA:
2376 DMEMIT_TARGET_NAME_VERSION(ti->type);
2377 DMEMIT(",snap_origin_name=%s", snap->origin->name);
2378 DMEMIT(",snap_cow_name=%s", snap->cow->name);
2379 DMEMIT(",snap_valid=%c", snap->valid ? 'y' : 'n');
2380 DMEMIT(",snap_merge_failed=%c", snap->merge_failed ? 'y' : 'n');
2381 DMEMIT(",snapshot_overflowed=%c", snap->snapshot_overflowed ? 'y' : 'n');
2382 DMEMIT(";");
2383 break;
2384 }
2385}
2386
2387static int snapshot_iterate_devices(struct dm_target *ti,
2388 iterate_devices_callout_fn fn, void *data)
2389{
2390 struct dm_snapshot *snap = ti->private;
2391 int r;
2392
2393 r = fn(ti, snap->origin, 0, ti->len, data);
2394
2395 if (!r)
2396 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2397
2398 return r;
2399}
2400
2401static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
2402{
2403 struct dm_snapshot *snap = ti->private;
2404
2405 if (snap->discard_zeroes_cow) {
2406 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2407
2408 down_read(&_origins_lock);
2409
2410 (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);
2411 if (snap_src && snap_dest)
2412 snap = snap_src;
2413
2414 /* All discards are split on chunk_size boundary */
2415 limits->discard_granularity = snap->store->chunk_size;
2416 limits->max_discard_sectors = snap->store->chunk_size;
2417
2418 up_read(&_origins_lock);
2419 }
2420}
2421
2422/*-----------------------------------------------------------------
2423 * Origin methods
2424 *---------------------------------------------------------------*/
2425
2426/*
2427 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2428 * supplied bio was ignored. The caller may submit it immediately.
2429 * (No remapping actually occurs as the origin is always a direct linear
2430 * map.)
2431 *
2432 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2433 * and any supplied bio is added to a list to be submitted once all
2434 * the necessary exceptions exist.
2435 */
2436static int __origin_write(struct list_head *snapshots, sector_t sector,
2437 struct bio *bio)
2438{
2439 int r = DM_MAPIO_REMAPPED;
2440 struct dm_snapshot *snap;
2441 struct dm_exception *e;
2442 struct dm_snap_pending_exception *pe, *pe2;
2443 struct dm_snap_pending_exception *pe_to_start_now = NULL;
2444 struct dm_snap_pending_exception *pe_to_start_last = NULL;
2445 struct dm_exception_table_lock lock;
2446 chunk_t chunk;
2447
2448 /* Do all the snapshots on this origin */
2449 list_for_each_entry (snap, snapshots, list) {
2450 /*
2451 * Don't make new exceptions in a merging snapshot
2452 * because it has effectively been deleted
2453 */
2454 if (dm_target_is_snapshot_merge(snap->ti))
2455 continue;
2456
2457 /* Nothing to do if writing beyond end of snapshot */
2458 if (sector >= dm_table_get_size(snap->ti->table))
2459 continue;
2460
2461 /*
2462 * Remember, different snapshots can have
2463 * different chunk sizes.
2464 */
2465 chunk = sector_to_chunk(snap->store, sector);
2466 dm_exception_table_lock_init(snap, chunk, &lock);
2467
2468 down_read(&snap->lock);
2469 dm_exception_table_lock(&lock);
2470
2471 /* Only deal with valid and active snapshots */
2472 if (!snap->valid || !snap->active)
2473 goto next_snapshot;
2474
2475 pe = __lookup_pending_exception(snap, chunk);
2476 if (!pe) {
2477 /*
2478 * Check exception table to see if block is already
2479 * remapped in this snapshot and trigger an exception
2480 * if not.
2481 */
2482 e = dm_lookup_exception(&snap->complete, chunk);
2483 if (e)
2484 goto next_snapshot;
2485
2486 dm_exception_table_unlock(&lock);
2487 pe = alloc_pending_exception(snap);
2488 dm_exception_table_lock(&lock);
2489
2490 pe2 = __lookup_pending_exception(snap, chunk);
2491
2492 if (!pe2) {
2493 e = dm_lookup_exception(&snap->complete, chunk);
2494 if (e) {
2495 free_pending_exception(pe);
2496 goto next_snapshot;
2497 }
2498
2499 pe = __insert_pending_exception(snap, pe, chunk);
2500 if (!pe) {
2501 dm_exception_table_unlock(&lock);
2502 up_read(&snap->lock);
2503
2504 invalidate_snapshot(snap, -ENOMEM);
2505 continue;
2506 }
2507 } else {
2508 free_pending_exception(pe);
2509 pe = pe2;
2510 }
2511 }
2512
2513 r = DM_MAPIO_SUBMITTED;
2514
2515 /*
2516 * If an origin bio was supplied, queue it to wait for the
2517 * completion of this exception, and start this one last,
2518 * at the end of the function.
2519 */
2520 if (bio) {
2521 bio_list_add(&pe->origin_bios, bio);
2522 bio = NULL;
2523
2524 if (!pe->started) {
2525 pe->started = 1;
2526 pe_to_start_last = pe;
2527 }
2528 }
2529
2530 if (!pe->started) {
2531 pe->started = 1;
2532 pe_to_start_now = pe;
2533 }
2534
2535next_snapshot:
2536 dm_exception_table_unlock(&lock);
2537 up_read(&snap->lock);
2538
2539 if (pe_to_start_now) {
2540 start_copy(pe_to_start_now);
2541 pe_to_start_now = NULL;
2542 }
2543 }
2544
2545 /*
2546 * Submit the exception against which the bio is queued last,
2547 * to give the other exceptions a head start.
2548 */
2549 if (pe_to_start_last)
2550 start_copy(pe_to_start_last);
2551
2552 return r;
2553}
2554
2555/*
2556 * Called on a write from the origin driver.
2557 */
2558static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
2559{
2560 struct origin *o;
2561 int r = DM_MAPIO_REMAPPED;
2562
2563again:
2564 down_read(&_origins_lock);
2565 o = __lookup_origin(origin->bdev);
2566 if (o) {
2567 if (limit) {
2568 struct dm_snapshot *s;
2569 list_for_each_entry(s, &o->snapshots, list)
2570 if (unlikely(!wait_for_in_progress(s, true)))
2571 goto again;
2572 }
2573
2574 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
2575 }
2576 up_read(&_origins_lock);
2577
2578 return r;
2579}
2580
2581/*
2582 * Trigger exceptions in all non-merging snapshots.
2583 *
2584 * The chunk size of the merging snapshot may be larger than the chunk
2585 * size of some other snapshot so we may need to reallocate multiple
2586 * chunks in other snapshots.
2587 *
2588 * We scan all the overlapping exceptions in the other snapshots.
2589 * Returns 1 if anything was reallocated and must be waited for,
2590 * otherwise returns 0.
2591 *
2592 * size must be a multiple of merging_snap's chunk_size.
2593 */
2594static int origin_write_extent(struct dm_snapshot *merging_snap,
2595 sector_t sector, unsigned size)
2596{
2597 int must_wait = 0;
2598 sector_t n;
2599 struct origin *o;
2600
2601 /*
2602 * The origin's __minimum_chunk_size() got stored in max_io_len
2603 * by snapshot_merge_resume().
2604 */
2605 down_read(&_origins_lock);
2606 o = __lookup_origin(merging_snap->origin->bdev);
2607 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2608 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2609 DM_MAPIO_SUBMITTED)
2610 must_wait = 1;
2611 up_read(&_origins_lock);
2612
2613 return must_wait;
2614}
2615
2616/*
2617 * Origin: maps a linear range of a device, with hooks for snapshotting.
2618 */
2619
2620/*
2621 * Construct an origin mapping: <dev_path>
2622 * The context for an origin is merely a 'struct dm_dev *'
2623 * pointing to the real device.
2624 */
2625static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2626{
2627 int r;
2628 struct dm_origin *o;
2629
2630 if (argc != 1) {
2631 ti->error = "origin: incorrect number of arguments";
2632 return -EINVAL;
2633 }
2634
2635 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2636 if (!o) {
2637 ti->error = "Cannot allocate private origin structure";
2638 r = -ENOMEM;
2639 goto bad_alloc;
2640 }
2641
2642 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2643 if (r) {
2644 ti->error = "Cannot get target device";
2645 goto bad_open;
2646 }
2647
2648 o->ti = ti;
2649 ti->private = o;
2650 ti->num_flush_bios = 1;
2651
2652 return 0;
2653
2654bad_open:
2655 kfree(o);
2656bad_alloc:
2657 return r;
2658}
2659
2660static void origin_dtr(struct dm_target *ti)
2661{
2662 struct dm_origin *o = ti->private;
2663
2664 dm_put_device(ti, o->dev);
2665 kfree(o);
2666}
2667
2668static int origin_map(struct dm_target *ti, struct bio *bio)
2669{
2670 struct dm_origin *o = ti->private;
2671 unsigned available_sectors;
2672
2673 bio_set_dev(bio, o->dev->bdev);
2674
2675 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2676 return DM_MAPIO_REMAPPED;
2677
2678 if (bio_data_dir(bio) != WRITE)
2679 return DM_MAPIO_REMAPPED;
2680
2681 available_sectors = o->split_boundary -
2682 ((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2683
2684 if (bio_sectors(bio) > available_sectors)
2685 dm_accept_partial_bio(bio, available_sectors);
2686
2687 /* Only tell snapshots if this is a write */
2688 return do_origin(o->dev, bio, true);
2689}
2690
2691/*
2692 * Set the target "max_io_len" field to the minimum of all the snapshots'
2693 * chunk sizes.
2694 */
2695static void origin_resume(struct dm_target *ti)
2696{
2697 struct dm_origin *o = ti->private;
2698
2699 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2700
2701 down_write(&_origins_lock);
2702 __insert_dm_origin(o);
2703 up_write(&_origins_lock);
2704}
2705
2706static void origin_postsuspend(struct dm_target *ti)
2707{
2708 struct dm_origin *o = ti->private;
2709
2710 down_write(&_origins_lock);
2711 __remove_dm_origin(o);
2712 up_write(&_origins_lock);
2713}
2714
2715static void origin_status(struct dm_target *ti, status_type_t type,
2716 unsigned status_flags, char *result, unsigned maxlen)
2717{
2718 struct dm_origin *o = ti->private;
2719
2720 switch (type) {
2721 case STATUSTYPE_INFO:
2722 result[0] = '\0';
2723 break;
2724
2725 case STATUSTYPE_TABLE:
2726 snprintf(result, maxlen, "%s", o->dev->name);
2727 break;
2728 case STATUSTYPE_IMA:
2729 result[0] = '\0';
2730 break;
2731 }
2732}
2733
2734static int origin_iterate_devices(struct dm_target *ti,
2735 iterate_devices_callout_fn fn, void *data)
2736{
2737 struct dm_origin *o = ti->private;
2738
2739 return fn(ti, o->dev, 0, ti->len, data);
2740}
2741
2742static struct target_type origin_target = {
2743 .name = "snapshot-origin",
2744 .version = {1, 9, 0},
2745 .module = THIS_MODULE,
2746 .ctr = origin_ctr,
2747 .dtr = origin_dtr,
2748 .map = origin_map,
2749 .resume = origin_resume,
2750 .postsuspend = origin_postsuspend,
2751 .status = origin_status,
2752 .iterate_devices = origin_iterate_devices,
2753};
2754
2755static struct target_type snapshot_target = {
2756 .name = "snapshot",
2757 .version = {1, 16, 0},
2758 .module = THIS_MODULE,
2759 .ctr = snapshot_ctr,
2760 .dtr = snapshot_dtr,
2761 .map = snapshot_map,
2762 .end_io = snapshot_end_io,
2763 .preresume = snapshot_preresume,
2764 .resume = snapshot_resume,
2765 .status = snapshot_status,
2766 .iterate_devices = snapshot_iterate_devices,
2767 .io_hints = snapshot_io_hints,
2768};
2769
2770static struct target_type merge_target = {
2771 .name = dm_snapshot_merge_target_name,
2772 .version = {1, 5, 0},
2773 .module = THIS_MODULE,
2774 .ctr = snapshot_ctr,
2775 .dtr = snapshot_dtr,
2776 .map = snapshot_merge_map,
2777 .end_io = snapshot_end_io,
2778 .presuspend = snapshot_merge_presuspend,
2779 .preresume = snapshot_preresume,
2780 .resume = snapshot_merge_resume,
2781 .status = snapshot_status,
2782 .iterate_devices = snapshot_iterate_devices,
2783 .io_hints = snapshot_io_hints,
2784};
2785
2786static int __init dm_snapshot_init(void)
2787{
2788 int r;
2789
2790 r = dm_exception_store_init();
2791 if (r) {
2792 DMERR("Failed to initialize exception stores");
2793 return r;
2794 }
2795
2796 r = init_origin_hash();
2797 if (r) {
2798 DMERR("init_origin_hash failed.");
2799 goto bad_origin_hash;
2800 }
2801
2802 exception_cache = KMEM_CACHE(dm_exception, 0);
2803 if (!exception_cache) {
2804 DMERR("Couldn't create exception cache.");
2805 r = -ENOMEM;
2806 goto bad_exception_cache;
2807 }
2808
2809 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2810 if (!pending_cache) {
2811 DMERR("Couldn't create pending cache.");
2812 r = -ENOMEM;
2813 goto bad_pending_cache;
2814 }
2815
2816 r = dm_register_target(&snapshot_target);
2817 if (r < 0) {
2818 DMERR("snapshot target register failed %d", r);
2819 goto bad_register_snapshot_target;
2820 }
2821
2822 r = dm_register_target(&origin_target);
2823 if (r < 0) {
2824 DMERR("Origin target register failed %d", r);
2825 goto bad_register_origin_target;
2826 }
2827
2828 r = dm_register_target(&merge_target);
2829 if (r < 0) {
2830 DMERR("Merge target register failed %d", r);
2831 goto bad_register_merge_target;
2832 }
2833
2834 return 0;
2835
2836bad_register_merge_target:
2837 dm_unregister_target(&origin_target);
2838bad_register_origin_target:
2839 dm_unregister_target(&snapshot_target);
2840bad_register_snapshot_target:
2841 kmem_cache_destroy(pending_cache);
2842bad_pending_cache:
2843 kmem_cache_destroy(exception_cache);
2844bad_exception_cache:
2845 exit_origin_hash();
2846bad_origin_hash:
2847 dm_exception_store_exit();
2848
2849 return r;
2850}
2851
2852static void __exit dm_snapshot_exit(void)
2853{
2854 dm_unregister_target(&snapshot_target);
2855 dm_unregister_target(&origin_target);
2856 dm_unregister_target(&merge_target);
2857
2858 exit_origin_hash();
2859 kmem_cache_destroy(pending_cache);
2860 kmem_cache_destroy(exception_cache);
2861
2862 dm_exception_store_exit();
2863}
2864
2865/* Module hooks */
2866module_init(dm_snapshot_init);
2867module_exit(dm_snapshot_exit);
2868
2869MODULE_DESCRIPTION(DM_NAME " snapshot target");
2870MODULE_AUTHOR("Joe Thornber");
2871MODULE_LICENSE("GPL");
2872MODULE_ALIAS("dm-snapshot-origin");
2873MODULE_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");