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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 * Flush data after merge.
147 */
148 struct bio flush_bio;
149};
150
151/*
152 * state_bits:
153 * RUNNING_MERGE - Merge operation is in progress.
154 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
155 * cleared afterwards.
156 */
157#define RUNNING_MERGE 0
158#define SHUTDOWN_MERGE 1
159
160/*
161 * Maximum number of chunks being copied on write.
162 *
163 * The value was decided experimentally as a trade-off between memory
164 * consumption, stalling the kernel's workqueues and maintaining a high enough
165 * throughput.
166 */
167#define DEFAULT_COW_THRESHOLD 2048
168
169static unsigned cow_threshold = DEFAULT_COW_THRESHOLD;
170module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);
171MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
172
173DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
174 "A percentage of time allocated for copy on write");
175
176struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
177{
178 return s->origin;
179}
180EXPORT_SYMBOL(dm_snap_origin);
181
182struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
183{
184 return s->cow;
185}
186EXPORT_SYMBOL(dm_snap_cow);
187
188static sector_t chunk_to_sector(struct dm_exception_store *store,
189 chunk_t chunk)
190{
191 return chunk << store->chunk_shift;
192}
193
194static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
195{
196 /*
197 * There is only ever one instance of a particular block
198 * device so we can compare pointers safely.
199 */
200 return lhs == rhs;
201}
202
203struct dm_snap_pending_exception {
204 struct dm_exception e;
205
206 /*
207 * Origin buffers waiting for this to complete are held
208 * in a bio list
209 */
210 struct bio_list origin_bios;
211 struct bio_list snapshot_bios;
212
213 /* Pointer back to snapshot context */
214 struct dm_snapshot *snap;
215
216 /*
217 * 1 indicates the exception has already been sent to
218 * kcopyd.
219 */
220 int started;
221
222 /* There was copying error. */
223 int copy_error;
224
225 /* A sequence number, it is used for in-order completion. */
226 sector_t exception_sequence;
227
228 struct rb_node out_of_order_node;
229
230 /*
231 * For writing a complete chunk, bypassing the copy.
232 */
233 struct bio *full_bio;
234 bio_end_io_t *full_bio_end_io;
235};
236
237/*
238 * Hash table mapping origin volumes to lists of snapshots and
239 * a lock to protect it
240 */
241static struct kmem_cache *exception_cache;
242static struct kmem_cache *pending_cache;
243
244struct dm_snap_tracked_chunk {
245 struct hlist_node node;
246 chunk_t chunk;
247};
248
249static void init_tracked_chunk(struct bio *bio)
250{
251 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
252 INIT_HLIST_NODE(&c->node);
253}
254
255static bool is_bio_tracked(struct bio *bio)
256{
257 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
258 return !hlist_unhashed(&c->node);
259}
260
261static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
262{
263 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
264
265 c->chunk = chunk;
266
267 spin_lock_irq(&s->tracked_chunk_lock);
268 hlist_add_head(&c->node,
269 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
270 spin_unlock_irq(&s->tracked_chunk_lock);
271}
272
273static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
274{
275 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
276 unsigned long flags;
277
278 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
279 hlist_del(&c->node);
280 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
281}
282
283static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
284{
285 struct dm_snap_tracked_chunk *c;
286 int found = 0;
287
288 spin_lock_irq(&s->tracked_chunk_lock);
289
290 hlist_for_each_entry(c,
291 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
292 if (c->chunk == chunk) {
293 found = 1;
294 break;
295 }
296 }
297
298 spin_unlock_irq(&s->tracked_chunk_lock);
299
300 return found;
301}
302
303/*
304 * This conflicting I/O is extremely improbable in the caller,
305 * so msleep(1) is sufficient and there is no need for a wait queue.
306 */
307static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
308{
309 while (__chunk_is_tracked(s, chunk))
310 msleep(1);
311}
312
313/*
314 * One of these per registered origin, held in the snapshot_origins hash
315 */
316struct origin {
317 /* The origin device */
318 struct block_device *bdev;
319
320 struct list_head hash_list;
321
322 /* List of snapshots for this origin */
323 struct list_head snapshots;
324};
325
326/*
327 * This structure is allocated for each origin target
328 */
329struct dm_origin {
330 struct dm_dev *dev;
331 struct dm_target *ti;
332 unsigned split_boundary;
333 struct list_head hash_list;
334};
335
336/*
337 * Size of the hash table for origin volumes. If we make this
338 * the size of the minors list then it should be nearly perfect
339 */
340#define ORIGIN_HASH_SIZE 256
341#define ORIGIN_MASK 0xFF
342static struct list_head *_origins;
343static struct list_head *_dm_origins;
344static struct rw_semaphore _origins_lock;
345
346static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
347static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
348static uint64_t _pending_exceptions_done_count;
349
350static int init_origin_hash(void)
351{
352 int i;
353
354 _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),
355 GFP_KERNEL);
356 if (!_origins) {
357 DMERR("unable to allocate memory for _origins");
358 return -ENOMEM;
359 }
360 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
361 INIT_LIST_HEAD(_origins + i);
362
363 _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,
364 sizeof(struct list_head),
365 GFP_KERNEL);
366 if (!_dm_origins) {
367 DMERR("unable to allocate memory for _dm_origins");
368 kfree(_origins);
369 return -ENOMEM;
370 }
371 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
372 INIT_LIST_HEAD(_dm_origins + i);
373
374 init_rwsem(&_origins_lock);
375
376 return 0;
377}
378
379static void exit_origin_hash(void)
380{
381 kfree(_origins);
382 kfree(_dm_origins);
383}
384
385static unsigned origin_hash(struct block_device *bdev)
386{
387 return bdev->bd_dev & ORIGIN_MASK;
388}
389
390static struct origin *__lookup_origin(struct block_device *origin)
391{
392 struct list_head *ol;
393 struct origin *o;
394
395 ol = &_origins[origin_hash(origin)];
396 list_for_each_entry (o, ol, hash_list)
397 if (bdev_equal(o->bdev, origin))
398 return o;
399
400 return NULL;
401}
402
403static void __insert_origin(struct origin *o)
404{
405 struct list_head *sl = &_origins[origin_hash(o->bdev)];
406 list_add_tail(&o->hash_list, sl);
407}
408
409static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
410{
411 struct list_head *ol;
412 struct dm_origin *o;
413
414 ol = &_dm_origins[origin_hash(origin)];
415 list_for_each_entry (o, ol, hash_list)
416 if (bdev_equal(o->dev->bdev, origin))
417 return o;
418
419 return NULL;
420}
421
422static void __insert_dm_origin(struct dm_origin *o)
423{
424 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
425 list_add_tail(&o->hash_list, sl);
426}
427
428static void __remove_dm_origin(struct dm_origin *o)
429{
430 list_del(&o->hash_list);
431}
432
433/*
434 * _origins_lock must be held when calling this function.
435 * Returns number of snapshots registered using the supplied cow device, plus:
436 * snap_src - a snapshot suitable for use as a source of exception handover
437 * snap_dest - a snapshot capable of receiving exception handover.
438 * snap_merge - an existing snapshot-merge target linked to the same origin.
439 * There can be at most one snapshot-merge target. The parameter is optional.
440 *
441 * Possible return values and states of snap_src and snap_dest.
442 * 0: NULL, NULL - first new snapshot
443 * 1: snap_src, NULL - normal snapshot
444 * 2: snap_src, snap_dest - waiting for handover
445 * 2: snap_src, NULL - handed over, waiting for old to be deleted
446 * 1: NULL, snap_dest - source got destroyed without handover
447 */
448static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
449 struct dm_snapshot **snap_src,
450 struct dm_snapshot **snap_dest,
451 struct dm_snapshot **snap_merge)
452{
453 struct dm_snapshot *s;
454 struct origin *o;
455 int count = 0;
456 int active;
457
458 o = __lookup_origin(snap->origin->bdev);
459 if (!o)
460 goto out;
461
462 list_for_each_entry(s, &o->snapshots, list) {
463 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
464 *snap_merge = s;
465 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
466 continue;
467
468 down_read(&s->lock);
469 active = s->active;
470 up_read(&s->lock);
471
472 if (active) {
473 if (snap_src)
474 *snap_src = s;
475 } else if (snap_dest)
476 *snap_dest = s;
477
478 count++;
479 }
480
481out:
482 return count;
483}
484
485/*
486 * On success, returns 1 if this snapshot is a handover destination,
487 * otherwise returns 0.
488 */
489static int __validate_exception_handover(struct dm_snapshot *snap)
490{
491 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
492 struct dm_snapshot *snap_merge = NULL;
493
494 /* Does snapshot need exceptions handed over to it? */
495 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
496 &snap_merge) == 2) ||
497 snap_dest) {
498 snap->ti->error = "Snapshot cow pairing for exception "
499 "table handover failed";
500 return -EINVAL;
501 }
502
503 /*
504 * If no snap_src was found, snap cannot become a handover
505 * destination.
506 */
507 if (!snap_src)
508 return 0;
509
510 /*
511 * Non-snapshot-merge handover?
512 */
513 if (!dm_target_is_snapshot_merge(snap->ti))
514 return 1;
515
516 /*
517 * Do not allow more than one merging snapshot.
518 */
519 if (snap_merge) {
520 snap->ti->error = "A snapshot is already merging.";
521 return -EINVAL;
522 }
523
524 if (!snap_src->store->type->prepare_merge ||
525 !snap_src->store->type->commit_merge) {
526 snap->ti->error = "Snapshot exception store does not "
527 "support snapshot-merge.";
528 return -EINVAL;
529 }
530
531 return 1;
532}
533
534static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
535{
536 struct dm_snapshot *l;
537
538 /* Sort the list according to chunk size, largest-first smallest-last */
539 list_for_each_entry(l, &o->snapshots, list)
540 if (l->store->chunk_size < s->store->chunk_size)
541 break;
542 list_add_tail(&s->list, &l->list);
543}
544
545/*
546 * Make a note of the snapshot and its origin so we can look it
547 * up when the origin has a write on it.
548 *
549 * Also validate snapshot exception store handovers.
550 * On success, returns 1 if this registration is a handover destination,
551 * otherwise returns 0.
552 */
553static int register_snapshot(struct dm_snapshot *snap)
554{
555 struct origin *o, *new_o = NULL;
556 struct block_device *bdev = snap->origin->bdev;
557 int r = 0;
558
559 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
560 if (!new_o)
561 return -ENOMEM;
562
563 down_write(&_origins_lock);
564
565 r = __validate_exception_handover(snap);
566 if (r < 0) {
567 kfree(new_o);
568 goto out;
569 }
570
571 o = __lookup_origin(bdev);
572 if (o)
573 kfree(new_o);
574 else {
575 /* New origin */
576 o = new_o;
577
578 /* Initialise the struct */
579 INIT_LIST_HEAD(&o->snapshots);
580 o->bdev = bdev;
581
582 __insert_origin(o);
583 }
584
585 __insert_snapshot(o, snap);
586
587out:
588 up_write(&_origins_lock);
589
590 return r;
591}
592
593/*
594 * Move snapshot to correct place in list according to chunk size.
595 */
596static void reregister_snapshot(struct dm_snapshot *s)
597{
598 struct block_device *bdev = s->origin->bdev;
599
600 down_write(&_origins_lock);
601
602 list_del(&s->list);
603 __insert_snapshot(__lookup_origin(bdev), s);
604
605 up_write(&_origins_lock);
606}
607
608static void unregister_snapshot(struct dm_snapshot *s)
609{
610 struct origin *o;
611
612 down_write(&_origins_lock);
613 o = __lookup_origin(s->origin->bdev);
614
615 list_del(&s->list);
616 if (o && list_empty(&o->snapshots)) {
617 list_del(&o->hash_list);
618 kfree(o);
619 }
620
621 up_write(&_origins_lock);
622}
623
624/*
625 * Implementation of the exception hash tables.
626 * The lowest hash_shift bits of the chunk number are ignored, allowing
627 * some consecutive chunks to be grouped together.
628 */
629static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk);
630
631/* Lock to protect access to the completed and pending exception hash tables. */
632struct dm_exception_table_lock {
633 struct hlist_bl_head *complete_slot;
634 struct hlist_bl_head *pending_slot;
635};
636
637static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk,
638 struct dm_exception_table_lock *lock)
639{
640 struct dm_exception_table *complete = &s->complete;
641 struct dm_exception_table *pending = &s->pending;
642
643 lock->complete_slot = &complete->table[exception_hash(complete, chunk)];
644 lock->pending_slot = &pending->table[exception_hash(pending, chunk)];
645}
646
647static void dm_exception_table_lock(struct dm_exception_table_lock *lock)
648{
649 hlist_bl_lock(lock->complete_slot);
650 hlist_bl_lock(lock->pending_slot);
651}
652
653static void dm_exception_table_unlock(struct dm_exception_table_lock *lock)
654{
655 hlist_bl_unlock(lock->pending_slot);
656 hlist_bl_unlock(lock->complete_slot);
657}
658
659static int dm_exception_table_init(struct dm_exception_table *et,
660 uint32_t size, unsigned hash_shift)
661{
662 unsigned int i;
663
664 et->hash_shift = hash_shift;
665 et->hash_mask = size - 1;
666 et->table = kvmalloc_array(size, sizeof(struct hlist_bl_head),
667 GFP_KERNEL);
668 if (!et->table)
669 return -ENOMEM;
670
671 for (i = 0; i < size; i++)
672 INIT_HLIST_BL_HEAD(et->table + i);
673
674 return 0;
675}
676
677static void dm_exception_table_exit(struct dm_exception_table *et,
678 struct kmem_cache *mem)
679{
680 struct hlist_bl_head *slot;
681 struct dm_exception *ex;
682 struct hlist_bl_node *pos, *n;
683 int i, size;
684
685 size = et->hash_mask + 1;
686 for (i = 0; i < size; i++) {
687 slot = et->table + i;
688
689 hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
690 kmem_cache_free(mem, ex);
691 }
692
693 kvfree(et->table);
694}
695
696static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
697{
698 return (chunk >> et->hash_shift) & et->hash_mask;
699}
700
701static void dm_remove_exception(struct dm_exception *e)
702{
703 hlist_bl_del(&e->hash_list);
704}
705
706/*
707 * Return the exception data for a sector, or NULL if not
708 * remapped.
709 */
710static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
711 chunk_t chunk)
712{
713 struct hlist_bl_head *slot;
714 struct hlist_bl_node *pos;
715 struct dm_exception *e;
716
717 slot = &et->table[exception_hash(et, chunk)];
718 hlist_bl_for_each_entry(e, pos, slot, hash_list)
719 if (chunk >= e->old_chunk &&
720 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
721 return e;
722
723 return NULL;
724}
725
726static struct dm_exception *alloc_completed_exception(gfp_t gfp)
727{
728 struct dm_exception *e;
729
730 e = kmem_cache_alloc(exception_cache, gfp);
731 if (!e && gfp == GFP_NOIO)
732 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
733
734 return e;
735}
736
737static void free_completed_exception(struct dm_exception *e)
738{
739 kmem_cache_free(exception_cache, e);
740}
741
742static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
743{
744 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
745 GFP_NOIO);
746
747 atomic_inc(&s->pending_exceptions_count);
748 pe->snap = s;
749
750 return pe;
751}
752
753static void free_pending_exception(struct dm_snap_pending_exception *pe)
754{
755 struct dm_snapshot *s = pe->snap;
756
757 mempool_free(pe, &s->pending_pool);
758 smp_mb__before_atomic();
759 atomic_dec(&s->pending_exceptions_count);
760}
761
762static void dm_insert_exception(struct dm_exception_table *eh,
763 struct dm_exception *new_e)
764{
765 struct hlist_bl_head *l;
766 struct hlist_bl_node *pos;
767 struct dm_exception *e = NULL;
768
769 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
770
771 /* Add immediately if this table doesn't support consecutive chunks */
772 if (!eh->hash_shift)
773 goto out;
774
775 /* List is ordered by old_chunk */
776 hlist_bl_for_each_entry(e, pos, l, hash_list) {
777 /* Insert after an existing chunk? */
778 if (new_e->old_chunk == (e->old_chunk +
779 dm_consecutive_chunk_count(e) + 1) &&
780 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
781 dm_consecutive_chunk_count(e) + 1)) {
782 dm_consecutive_chunk_count_inc(e);
783 free_completed_exception(new_e);
784 return;
785 }
786
787 /* Insert before an existing chunk? */
788 if (new_e->old_chunk == (e->old_chunk - 1) &&
789 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
790 dm_consecutive_chunk_count_inc(e);
791 e->old_chunk--;
792 e->new_chunk--;
793 free_completed_exception(new_e);
794 return;
795 }
796
797 if (new_e->old_chunk < e->old_chunk)
798 break;
799 }
800
801out:
802 if (!e) {
803 /*
804 * Either the table doesn't support consecutive chunks or slot
805 * l is empty.
806 */
807 hlist_bl_add_head(&new_e->hash_list, l);
808 } else if (new_e->old_chunk < e->old_chunk) {
809 /* Add before an existing exception */
810 hlist_bl_add_before(&new_e->hash_list, &e->hash_list);
811 } else {
812 /* Add to l's tail: e is the last exception in this slot */
813 hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);
814 }
815}
816
817/*
818 * Callback used by the exception stores to load exceptions when
819 * initialising.
820 */
821static int dm_add_exception(void *context, chunk_t old, chunk_t new)
822{
823 struct dm_exception_table_lock lock;
824 struct dm_snapshot *s = context;
825 struct dm_exception *e;
826
827 e = alloc_completed_exception(GFP_KERNEL);
828 if (!e)
829 return -ENOMEM;
830
831 e->old_chunk = old;
832
833 /* Consecutive_count is implicitly initialised to zero */
834 e->new_chunk = new;
835
836 /*
837 * Although there is no need to lock access to the exception tables
838 * here, if we don't then hlist_bl_add_head(), called by
839 * dm_insert_exception(), will complain about accessing the
840 * corresponding list without locking it first.
841 */
842 dm_exception_table_lock_init(s, old, &lock);
843
844 dm_exception_table_lock(&lock);
845 dm_insert_exception(&s->complete, e);
846 dm_exception_table_unlock(&lock);
847
848 return 0;
849}
850
851/*
852 * Return a minimum chunk size of all snapshots that have the specified origin.
853 * Return zero if the origin has no snapshots.
854 */
855static uint32_t __minimum_chunk_size(struct origin *o)
856{
857 struct dm_snapshot *snap;
858 unsigned chunk_size = rounddown_pow_of_two(UINT_MAX);
859
860 if (o)
861 list_for_each_entry(snap, &o->snapshots, list)
862 chunk_size = min_not_zero(chunk_size,
863 snap->store->chunk_size);
864
865 return (uint32_t) chunk_size;
866}
867
868/*
869 * Hard coded magic.
870 */
871static int calc_max_buckets(void)
872{
873 /* use a fixed size of 2MB */
874 unsigned long mem = 2 * 1024 * 1024;
875 mem /= sizeof(struct hlist_bl_head);
876
877 return mem;
878}
879
880/*
881 * Allocate room for a suitable hash table.
882 */
883static int init_hash_tables(struct dm_snapshot *s)
884{
885 sector_t hash_size, cow_dev_size, max_buckets;
886
887 /*
888 * Calculate based on the size of the original volume or
889 * the COW volume...
890 */
891 cow_dev_size = get_dev_size(s->cow->bdev);
892 max_buckets = calc_max_buckets();
893
894 hash_size = cow_dev_size >> s->store->chunk_shift;
895 hash_size = min(hash_size, max_buckets);
896
897 if (hash_size < 64)
898 hash_size = 64;
899 hash_size = rounddown_pow_of_two(hash_size);
900 if (dm_exception_table_init(&s->complete, hash_size,
901 DM_CHUNK_CONSECUTIVE_BITS))
902 return -ENOMEM;
903
904 /*
905 * Allocate hash table for in-flight exceptions
906 * Make this smaller than the real hash table
907 */
908 hash_size >>= 3;
909 if (hash_size < 64)
910 hash_size = 64;
911
912 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
913 dm_exception_table_exit(&s->complete, exception_cache);
914 return -ENOMEM;
915 }
916
917 return 0;
918}
919
920static void merge_shutdown(struct dm_snapshot *s)
921{
922 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
923 smp_mb__after_atomic();
924 wake_up_bit(&s->state_bits, RUNNING_MERGE);
925}
926
927static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
928{
929 s->first_merging_chunk = 0;
930 s->num_merging_chunks = 0;
931
932 return bio_list_get(&s->bios_queued_during_merge);
933}
934
935/*
936 * Remove one chunk from the index of completed exceptions.
937 */
938static int __remove_single_exception_chunk(struct dm_snapshot *s,
939 chunk_t old_chunk)
940{
941 struct dm_exception *e;
942
943 e = dm_lookup_exception(&s->complete, old_chunk);
944 if (!e) {
945 DMERR("Corruption detected: exception for block %llu is "
946 "on disk but not in memory",
947 (unsigned long long)old_chunk);
948 return -EINVAL;
949 }
950
951 /*
952 * If this is the only chunk using this exception, remove exception.
953 */
954 if (!dm_consecutive_chunk_count(e)) {
955 dm_remove_exception(e);
956 free_completed_exception(e);
957 return 0;
958 }
959
960 /*
961 * The chunk may be either at the beginning or the end of a
962 * group of consecutive chunks - never in the middle. We are
963 * removing chunks in the opposite order to that in which they
964 * were added, so this should always be true.
965 * Decrement the consecutive chunk counter and adjust the
966 * starting point if necessary.
967 */
968 if (old_chunk == e->old_chunk) {
969 e->old_chunk++;
970 e->new_chunk++;
971 } else if (old_chunk != e->old_chunk +
972 dm_consecutive_chunk_count(e)) {
973 DMERR("Attempt to merge block %llu from the "
974 "middle of a chunk range [%llu - %llu]",
975 (unsigned long long)old_chunk,
976 (unsigned long long)e->old_chunk,
977 (unsigned long long)
978 e->old_chunk + dm_consecutive_chunk_count(e));
979 return -EINVAL;
980 }
981
982 dm_consecutive_chunk_count_dec(e);
983
984 return 0;
985}
986
987static void flush_bios(struct bio *bio);
988
989static int remove_single_exception_chunk(struct dm_snapshot *s)
990{
991 struct bio *b = NULL;
992 int r;
993 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
994
995 down_write(&s->lock);
996
997 /*
998 * Process chunks (and associated exceptions) in reverse order
999 * so that dm_consecutive_chunk_count_dec() accounting works.
1000 */
1001 do {
1002 r = __remove_single_exception_chunk(s, old_chunk);
1003 if (r)
1004 goto out;
1005 } while (old_chunk-- > s->first_merging_chunk);
1006
1007 b = __release_queued_bios_after_merge(s);
1008
1009out:
1010 up_write(&s->lock);
1011 if (b)
1012 flush_bios(b);
1013
1014 return r;
1015}
1016
1017static int origin_write_extent(struct dm_snapshot *merging_snap,
1018 sector_t sector, unsigned chunk_size);
1019
1020static void merge_callback(int read_err, unsigned long write_err,
1021 void *context);
1022
1023static uint64_t read_pending_exceptions_done_count(void)
1024{
1025 uint64_t pending_exceptions_done;
1026
1027 spin_lock(&_pending_exceptions_done_spinlock);
1028 pending_exceptions_done = _pending_exceptions_done_count;
1029 spin_unlock(&_pending_exceptions_done_spinlock);
1030
1031 return pending_exceptions_done;
1032}
1033
1034static void increment_pending_exceptions_done_count(void)
1035{
1036 spin_lock(&_pending_exceptions_done_spinlock);
1037 _pending_exceptions_done_count++;
1038 spin_unlock(&_pending_exceptions_done_spinlock);
1039
1040 wake_up_all(&_pending_exceptions_done);
1041}
1042
1043static void snapshot_merge_next_chunks(struct dm_snapshot *s)
1044{
1045 int i, linear_chunks;
1046 chunk_t old_chunk, new_chunk;
1047 struct dm_io_region src, dest;
1048 sector_t io_size;
1049 uint64_t previous_count;
1050
1051 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
1052 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
1053 goto shut;
1054
1055 /*
1056 * valid flag never changes during merge, so no lock required.
1057 */
1058 if (!s->valid) {
1059 DMERR("Snapshot is invalid: can't merge");
1060 goto shut;
1061 }
1062
1063 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
1064 &new_chunk);
1065 if (linear_chunks <= 0) {
1066 if (linear_chunks < 0) {
1067 DMERR("Read error in exception store: "
1068 "shutting down merge");
1069 down_write(&s->lock);
1070 s->merge_failed = true;
1071 up_write(&s->lock);
1072 }
1073 goto shut;
1074 }
1075
1076 /* Adjust old_chunk and new_chunk to reflect start of linear region */
1077 old_chunk = old_chunk + 1 - linear_chunks;
1078 new_chunk = new_chunk + 1 - linear_chunks;
1079
1080 /*
1081 * Use one (potentially large) I/O to copy all 'linear_chunks'
1082 * from the exception store to the origin
1083 */
1084 io_size = linear_chunks * s->store->chunk_size;
1085
1086 dest.bdev = s->origin->bdev;
1087 dest.sector = chunk_to_sector(s->store, old_chunk);
1088 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1089
1090 src.bdev = s->cow->bdev;
1091 src.sector = chunk_to_sector(s->store, new_chunk);
1092 src.count = dest.count;
1093
1094 /*
1095 * Reallocate any exceptions needed in other snapshots then
1096 * wait for the pending exceptions to complete.
1097 * Each time any pending exception (globally on the system)
1098 * completes we are woken and repeat the process to find out
1099 * if we can proceed. While this may not seem a particularly
1100 * efficient algorithm, it is not expected to have any
1101 * significant impact on performance.
1102 */
1103 previous_count = read_pending_exceptions_done_count();
1104 while (origin_write_extent(s, dest.sector, io_size)) {
1105 wait_event(_pending_exceptions_done,
1106 (read_pending_exceptions_done_count() !=
1107 previous_count));
1108 /* Retry after the wait, until all exceptions are done. */
1109 previous_count = read_pending_exceptions_done_count();
1110 }
1111
1112 down_write(&s->lock);
1113 s->first_merging_chunk = old_chunk;
1114 s->num_merging_chunks = linear_chunks;
1115 up_write(&s->lock);
1116
1117 /* Wait until writes to all 'linear_chunks' drain */
1118 for (i = 0; i < linear_chunks; i++)
1119 __check_for_conflicting_io(s, old_chunk + i);
1120
1121 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1122 return;
1123
1124shut:
1125 merge_shutdown(s);
1126}
1127
1128static void error_bios(struct bio *bio);
1129
1130static int flush_data(struct dm_snapshot *s)
1131{
1132 struct bio *flush_bio = &s->flush_bio;
1133
1134 bio_reset(flush_bio);
1135 bio_set_dev(flush_bio, s->origin->bdev);
1136 flush_bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
1137
1138 return submit_bio_wait(flush_bio);
1139}
1140
1141static void merge_callback(int read_err, unsigned long write_err, void *context)
1142{
1143 struct dm_snapshot *s = context;
1144 struct bio *b = NULL;
1145
1146 if (read_err || write_err) {
1147 if (read_err)
1148 DMERR("Read error: shutting down merge.");
1149 else
1150 DMERR("Write error: shutting down merge.");
1151 goto shut;
1152 }
1153
1154 if (flush_data(s) < 0) {
1155 DMERR("Flush after merge failed: shutting down merge");
1156 goto shut;
1157 }
1158
1159 if (s->store->type->commit_merge(s->store,
1160 s->num_merging_chunks) < 0) {
1161 DMERR("Write error in exception store: shutting down merge");
1162 goto shut;
1163 }
1164
1165 if (remove_single_exception_chunk(s) < 0)
1166 goto shut;
1167
1168 snapshot_merge_next_chunks(s);
1169
1170 return;
1171
1172shut:
1173 down_write(&s->lock);
1174 s->merge_failed = true;
1175 b = __release_queued_bios_after_merge(s);
1176 up_write(&s->lock);
1177 error_bios(b);
1178
1179 merge_shutdown(s);
1180}
1181
1182static void start_merge(struct dm_snapshot *s)
1183{
1184 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1185 snapshot_merge_next_chunks(s);
1186}
1187
1188/*
1189 * Stop the merging process and wait until it finishes.
1190 */
1191static void stop_merge(struct dm_snapshot *s)
1192{
1193 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1194 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1195 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1196}
1197
1198static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,
1199 struct dm_target *ti)
1200{
1201 int r;
1202 unsigned argc;
1203 const char *arg_name;
1204
1205 static const struct dm_arg _args[] = {
1206 {0, 2, "Invalid number of feature arguments"},
1207 };
1208
1209 /*
1210 * No feature arguments supplied.
1211 */
1212 if (!as->argc)
1213 return 0;
1214
1215 r = dm_read_arg_group(_args, as, &argc, &ti->error);
1216 if (r)
1217 return -EINVAL;
1218
1219 while (argc && !r) {
1220 arg_name = dm_shift_arg(as);
1221 argc--;
1222
1223 if (!strcasecmp(arg_name, "discard_zeroes_cow"))
1224 s->discard_zeroes_cow = true;
1225
1226 else if (!strcasecmp(arg_name, "discard_passdown_origin"))
1227 s->discard_passdown_origin = true;
1228
1229 else {
1230 ti->error = "Unrecognised feature requested";
1231 r = -EINVAL;
1232 break;
1233 }
1234 }
1235
1236 if (!s->discard_zeroes_cow && s->discard_passdown_origin) {
1237 /*
1238 * TODO: really these are disjoint.. but ti->num_discard_bios
1239 * and dm_bio_get_target_bio_nr() require rigid constraints.
1240 */
1241 ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";
1242 r = -EINVAL;
1243 }
1244
1245 return r;
1246}
1247
1248/*
1249 * Construct a snapshot mapping:
1250 * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]
1251 */
1252static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1253{
1254 struct dm_snapshot *s;
1255 struct dm_arg_set as;
1256 int i;
1257 int r = -EINVAL;
1258 char *origin_path, *cow_path;
1259 dev_t origin_dev, cow_dev;
1260 unsigned args_used, num_flush_bios = 1;
1261 fmode_t origin_mode = FMODE_READ;
1262
1263 if (argc < 4) {
1264 ti->error = "requires 4 or more arguments";
1265 r = -EINVAL;
1266 goto bad;
1267 }
1268
1269 if (dm_target_is_snapshot_merge(ti)) {
1270 num_flush_bios = 2;
1271 origin_mode = FMODE_WRITE;
1272 }
1273
1274 s = kzalloc(sizeof(*s), GFP_KERNEL);
1275 if (!s) {
1276 ti->error = "Cannot allocate private snapshot structure";
1277 r = -ENOMEM;
1278 goto bad;
1279 }
1280
1281 as.argc = argc;
1282 as.argv = argv;
1283 dm_consume_args(&as, 4);
1284 r = parse_snapshot_features(&as, s, ti);
1285 if (r)
1286 goto bad_features;
1287
1288 origin_path = argv[0];
1289 argv++;
1290 argc--;
1291
1292 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1293 if (r) {
1294 ti->error = "Cannot get origin device";
1295 goto bad_origin;
1296 }
1297 origin_dev = s->origin->bdev->bd_dev;
1298
1299 cow_path = argv[0];
1300 argv++;
1301 argc--;
1302
1303 cow_dev = dm_get_dev_t(cow_path);
1304 if (cow_dev && cow_dev == origin_dev) {
1305 ti->error = "COW device cannot be the same as origin device";
1306 r = -EINVAL;
1307 goto bad_cow;
1308 }
1309
1310 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1311 if (r) {
1312 ti->error = "Cannot get COW device";
1313 goto bad_cow;
1314 }
1315
1316 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1317 if (r) {
1318 ti->error = "Couldn't create exception store";
1319 r = -EINVAL;
1320 goto bad_store;
1321 }
1322
1323 argv += args_used;
1324 argc -= args_used;
1325
1326 s->ti = ti;
1327 s->valid = 1;
1328 s->snapshot_overflowed = 0;
1329 s->active = 0;
1330 atomic_set(&s->pending_exceptions_count, 0);
1331 spin_lock_init(&s->pe_allocation_lock);
1332 s->exception_start_sequence = 0;
1333 s->exception_complete_sequence = 0;
1334 s->out_of_order_tree = RB_ROOT;
1335 init_rwsem(&s->lock);
1336 INIT_LIST_HEAD(&s->list);
1337 spin_lock_init(&s->pe_lock);
1338 s->state_bits = 0;
1339 s->merge_failed = false;
1340 s->first_merging_chunk = 0;
1341 s->num_merging_chunks = 0;
1342 bio_list_init(&s->bios_queued_during_merge);
1343 bio_init(&s->flush_bio, NULL, 0);
1344
1345 /* Allocate hash table for COW data */
1346 if (init_hash_tables(s)) {
1347 ti->error = "Unable to allocate hash table space";
1348 r = -ENOMEM;
1349 goto bad_hash_tables;
1350 }
1351
1352 init_waitqueue_head(&s->in_progress_wait);
1353
1354 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1355 if (IS_ERR(s->kcopyd_client)) {
1356 r = PTR_ERR(s->kcopyd_client);
1357 ti->error = "Could not create kcopyd client";
1358 goto bad_kcopyd;
1359 }
1360
1361 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
1362 if (r) {
1363 ti->error = "Could not allocate mempool for pending exceptions";
1364 goto bad_pending_pool;
1365 }
1366
1367 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1368 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1369
1370 spin_lock_init(&s->tracked_chunk_lock);
1371
1372 ti->private = s;
1373 ti->num_flush_bios = num_flush_bios;
1374 if (s->discard_zeroes_cow)
1375 ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
1376 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1377
1378 /* Add snapshot to the list of snapshots for this origin */
1379 /* Exceptions aren't triggered till snapshot_resume() is called */
1380 r = register_snapshot(s);
1381 if (r == -ENOMEM) {
1382 ti->error = "Snapshot origin struct allocation failed";
1383 goto bad_load_and_register;
1384 } else if (r < 0) {
1385 /* invalid handover, register_snapshot has set ti->error */
1386 goto bad_load_and_register;
1387 }
1388
1389 /*
1390 * Metadata must only be loaded into one table at once, so skip this
1391 * if metadata will be handed over during resume.
1392 * Chunk size will be set during the handover - set it to zero to
1393 * ensure it's ignored.
1394 */
1395 if (r > 0) {
1396 s->store->chunk_size = 0;
1397 return 0;
1398 }
1399
1400 r = s->store->type->read_metadata(s->store, dm_add_exception,
1401 (void *)s);
1402 if (r < 0) {
1403 ti->error = "Failed to read snapshot metadata";
1404 goto bad_read_metadata;
1405 } else if (r > 0) {
1406 s->valid = 0;
1407 DMWARN("Snapshot is marked invalid.");
1408 }
1409
1410 if (!s->store->chunk_size) {
1411 ti->error = "Chunk size not set";
1412 r = -EINVAL;
1413 goto bad_read_metadata;
1414 }
1415
1416 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1417 if (r)
1418 goto bad_read_metadata;
1419
1420 return 0;
1421
1422bad_read_metadata:
1423 unregister_snapshot(s);
1424bad_load_and_register:
1425 mempool_exit(&s->pending_pool);
1426bad_pending_pool:
1427 dm_kcopyd_client_destroy(s->kcopyd_client);
1428bad_kcopyd:
1429 dm_exception_table_exit(&s->pending, pending_cache);
1430 dm_exception_table_exit(&s->complete, exception_cache);
1431bad_hash_tables:
1432 dm_exception_store_destroy(s->store);
1433bad_store:
1434 dm_put_device(ti, s->cow);
1435bad_cow:
1436 dm_put_device(ti, s->origin);
1437bad_origin:
1438bad_features:
1439 kfree(s);
1440bad:
1441 return r;
1442}
1443
1444static void __free_exceptions(struct dm_snapshot *s)
1445{
1446 dm_kcopyd_client_destroy(s->kcopyd_client);
1447 s->kcopyd_client = NULL;
1448
1449 dm_exception_table_exit(&s->pending, pending_cache);
1450 dm_exception_table_exit(&s->complete, exception_cache);
1451}
1452
1453static void __handover_exceptions(struct dm_snapshot *snap_src,
1454 struct dm_snapshot *snap_dest)
1455{
1456 union {
1457 struct dm_exception_table table_swap;
1458 struct dm_exception_store *store_swap;
1459 } u;
1460
1461 /*
1462 * Swap all snapshot context information between the two instances.
1463 */
1464 u.table_swap = snap_dest->complete;
1465 snap_dest->complete = snap_src->complete;
1466 snap_src->complete = u.table_swap;
1467
1468 u.store_swap = snap_dest->store;
1469 snap_dest->store = snap_src->store;
1470 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1471 snap_src->store = u.store_swap;
1472
1473 snap_dest->store->snap = snap_dest;
1474 snap_src->store->snap = snap_src;
1475
1476 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1477 snap_dest->valid = snap_src->valid;
1478 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1479
1480 /*
1481 * Set source invalid to ensure it receives no further I/O.
1482 */
1483 snap_src->valid = 0;
1484}
1485
1486static void snapshot_dtr(struct dm_target *ti)
1487{
1488#ifdef CONFIG_DM_DEBUG
1489 int i;
1490#endif
1491 struct dm_snapshot *s = ti->private;
1492 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1493
1494 down_read(&_origins_lock);
1495 /* Check whether exception handover must be cancelled */
1496 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1497 if (snap_src && snap_dest && (s == snap_src)) {
1498 down_write(&snap_dest->lock);
1499 snap_dest->valid = 0;
1500 up_write(&snap_dest->lock);
1501 DMERR("Cancelling snapshot handover.");
1502 }
1503 up_read(&_origins_lock);
1504
1505 if (dm_target_is_snapshot_merge(ti))
1506 stop_merge(s);
1507
1508 /* Prevent further origin writes from using this snapshot. */
1509 /* After this returns there can be no new kcopyd jobs. */
1510 unregister_snapshot(s);
1511
1512 while (atomic_read(&s->pending_exceptions_count))
1513 msleep(1);
1514 /*
1515 * Ensure instructions in mempool_exit aren't reordered
1516 * before atomic_read.
1517 */
1518 smp_mb();
1519
1520#ifdef CONFIG_DM_DEBUG
1521 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1522 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1523#endif
1524
1525 __free_exceptions(s);
1526
1527 mempool_exit(&s->pending_pool);
1528
1529 dm_exception_store_destroy(s->store);
1530
1531 bio_uninit(&s->flush_bio);
1532
1533 dm_put_device(ti, s->cow);
1534
1535 dm_put_device(ti, s->origin);
1536
1537 WARN_ON(s->in_progress);
1538
1539 kfree(s);
1540}
1541
1542static void account_start_copy(struct dm_snapshot *s)
1543{
1544 spin_lock(&s->in_progress_wait.lock);
1545 s->in_progress++;
1546 spin_unlock(&s->in_progress_wait.lock);
1547}
1548
1549static void account_end_copy(struct dm_snapshot *s)
1550{
1551 spin_lock(&s->in_progress_wait.lock);
1552 BUG_ON(!s->in_progress);
1553 s->in_progress--;
1554 if (likely(s->in_progress <= cow_threshold) &&
1555 unlikely(waitqueue_active(&s->in_progress_wait)))
1556 wake_up_locked(&s->in_progress_wait);
1557 spin_unlock(&s->in_progress_wait.lock);
1558}
1559
1560static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
1561{
1562 if (unlikely(s->in_progress > cow_threshold)) {
1563 spin_lock(&s->in_progress_wait.lock);
1564 if (likely(s->in_progress > cow_threshold)) {
1565 /*
1566 * NOTE: this throttle doesn't account for whether
1567 * the caller is servicing an IO that will trigger a COW
1568 * so excess throttling may result for chunks not required
1569 * to be COW'd. But if cow_threshold was reached, extra
1570 * throttling is unlikely to negatively impact performance.
1571 */
1572 DECLARE_WAITQUEUE(wait, current);
1573 __add_wait_queue(&s->in_progress_wait, &wait);
1574 __set_current_state(TASK_UNINTERRUPTIBLE);
1575 spin_unlock(&s->in_progress_wait.lock);
1576 if (unlock_origins)
1577 up_read(&_origins_lock);
1578 io_schedule();
1579 remove_wait_queue(&s->in_progress_wait, &wait);
1580 return false;
1581 }
1582 spin_unlock(&s->in_progress_wait.lock);
1583 }
1584 return true;
1585}
1586
1587/*
1588 * Flush a list of buffers.
1589 */
1590static void flush_bios(struct bio *bio)
1591{
1592 struct bio *n;
1593
1594 while (bio) {
1595 n = bio->bi_next;
1596 bio->bi_next = NULL;
1597 submit_bio_noacct(bio);
1598 bio = n;
1599 }
1600}
1601
1602static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
1603
1604/*
1605 * Flush a list of buffers.
1606 */
1607static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1608{
1609 struct bio *n;
1610 int r;
1611
1612 while (bio) {
1613 n = bio->bi_next;
1614 bio->bi_next = NULL;
1615 r = do_origin(s->origin, bio, false);
1616 if (r == DM_MAPIO_REMAPPED)
1617 submit_bio_noacct(bio);
1618 bio = n;
1619 }
1620}
1621
1622/*
1623 * Error a list of buffers.
1624 */
1625static void error_bios(struct bio *bio)
1626{
1627 struct bio *n;
1628
1629 while (bio) {
1630 n = bio->bi_next;
1631 bio->bi_next = NULL;
1632 bio_io_error(bio);
1633 bio = n;
1634 }
1635}
1636
1637static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1638{
1639 if (!s->valid)
1640 return;
1641
1642 if (err == -EIO)
1643 DMERR("Invalidating snapshot: Error reading/writing.");
1644 else if (err == -ENOMEM)
1645 DMERR("Invalidating snapshot: Unable to allocate exception.");
1646
1647 if (s->store->type->drop_snapshot)
1648 s->store->type->drop_snapshot(s->store);
1649
1650 s->valid = 0;
1651
1652 dm_table_event(s->ti->table);
1653}
1654
1655static void invalidate_snapshot(struct dm_snapshot *s, int err)
1656{
1657 down_write(&s->lock);
1658 __invalidate_snapshot(s, err);
1659 up_write(&s->lock);
1660}
1661
1662static void pending_complete(void *context, int success)
1663{
1664 struct dm_snap_pending_exception *pe = context;
1665 struct dm_exception *e;
1666 struct dm_snapshot *s = pe->snap;
1667 struct bio *origin_bios = NULL;
1668 struct bio *snapshot_bios = NULL;
1669 struct bio *full_bio = NULL;
1670 struct dm_exception_table_lock lock;
1671 int error = 0;
1672
1673 dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);
1674
1675 if (!success) {
1676 /* Read/write error - snapshot is unusable */
1677 invalidate_snapshot(s, -EIO);
1678 error = 1;
1679
1680 dm_exception_table_lock(&lock);
1681 goto out;
1682 }
1683
1684 e = alloc_completed_exception(GFP_NOIO);
1685 if (!e) {
1686 invalidate_snapshot(s, -ENOMEM);
1687 error = 1;
1688
1689 dm_exception_table_lock(&lock);
1690 goto out;
1691 }
1692 *e = pe->e;
1693
1694 down_read(&s->lock);
1695 dm_exception_table_lock(&lock);
1696 if (!s->valid) {
1697 up_read(&s->lock);
1698 free_completed_exception(e);
1699 error = 1;
1700
1701 goto out;
1702 }
1703
1704 /*
1705 * Add a proper exception. After inserting the completed exception all
1706 * subsequent snapshot reads to this chunk will be redirected to the
1707 * COW device. This ensures that we do not starve. Moreover, as long
1708 * as the pending exception exists, neither origin writes nor snapshot
1709 * merging can overwrite the chunk in origin.
1710 */
1711 dm_insert_exception(&s->complete, e);
1712 up_read(&s->lock);
1713
1714 /* Wait for conflicting reads to drain */
1715 if (__chunk_is_tracked(s, pe->e.old_chunk)) {
1716 dm_exception_table_unlock(&lock);
1717 __check_for_conflicting_io(s, pe->e.old_chunk);
1718 dm_exception_table_lock(&lock);
1719 }
1720
1721out:
1722 /* Remove the in-flight exception from the list */
1723 dm_remove_exception(&pe->e);
1724
1725 dm_exception_table_unlock(&lock);
1726
1727 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1728 origin_bios = bio_list_get(&pe->origin_bios);
1729 full_bio = pe->full_bio;
1730 if (full_bio)
1731 full_bio->bi_end_io = pe->full_bio_end_io;
1732 increment_pending_exceptions_done_count();
1733
1734 /* Submit any pending write bios */
1735 if (error) {
1736 if (full_bio)
1737 bio_io_error(full_bio);
1738 error_bios(snapshot_bios);
1739 } else {
1740 if (full_bio)
1741 bio_endio(full_bio);
1742 flush_bios(snapshot_bios);
1743 }
1744
1745 retry_origin_bios(s, origin_bios);
1746
1747 free_pending_exception(pe);
1748}
1749
1750static void complete_exception(struct dm_snap_pending_exception *pe)
1751{
1752 struct dm_snapshot *s = pe->snap;
1753
1754 /* Update the metadata if we are persistent */
1755 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1756 pending_complete, pe);
1757}
1758
1759/*
1760 * Called when the copy I/O has finished. kcopyd actually runs
1761 * this code so don't block.
1762 */
1763static void copy_callback(int read_err, unsigned long write_err, void *context)
1764{
1765 struct dm_snap_pending_exception *pe = context;
1766 struct dm_snapshot *s = pe->snap;
1767
1768 pe->copy_error = read_err || write_err;
1769
1770 if (pe->exception_sequence == s->exception_complete_sequence) {
1771 struct rb_node *next;
1772
1773 s->exception_complete_sequence++;
1774 complete_exception(pe);
1775
1776 next = rb_first(&s->out_of_order_tree);
1777 while (next) {
1778 pe = rb_entry(next, struct dm_snap_pending_exception,
1779 out_of_order_node);
1780 if (pe->exception_sequence != s->exception_complete_sequence)
1781 break;
1782 next = rb_next(next);
1783 s->exception_complete_sequence++;
1784 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
1785 complete_exception(pe);
1786 cond_resched();
1787 }
1788 } else {
1789 struct rb_node *parent = NULL;
1790 struct rb_node **p = &s->out_of_order_tree.rb_node;
1791 struct dm_snap_pending_exception *pe2;
1792
1793 while (*p) {
1794 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
1795 parent = *p;
1796
1797 BUG_ON(pe->exception_sequence == pe2->exception_sequence);
1798 if (pe->exception_sequence < pe2->exception_sequence)
1799 p = &((*p)->rb_left);
1800 else
1801 p = &((*p)->rb_right);
1802 }
1803
1804 rb_link_node(&pe->out_of_order_node, parent, p);
1805 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
1806 }
1807 account_end_copy(s);
1808}
1809
1810/*
1811 * Dispatches the copy operation to kcopyd.
1812 */
1813static void start_copy(struct dm_snap_pending_exception *pe)
1814{
1815 struct dm_snapshot *s = pe->snap;
1816 struct dm_io_region src, dest;
1817 struct block_device *bdev = s->origin->bdev;
1818 sector_t dev_size;
1819
1820 dev_size = get_dev_size(bdev);
1821
1822 src.bdev = bdev;
1823 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1824 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1825
1826 dest.bdev = s->cow->bdev;
1827 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1828 dest.count = src.count;
1829
1830 /* Hand over to kcopyd */
1831 account_start_copy(s);
1832 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1833}
1834
1835static void full_bio_end_io(struct bio *bio)
1836{
1837 void *callback_data = bio->bi_private;
1838
1839 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
1840}
1841
1842static void start_full_bio(struct dm_snap_pending_exception *pe,
1843 struct bio *bio)
1844{
1845 struct dm_snapshot *s = pe->snap;
1846 void *callback_data;
1847
1848 pe->full_bio = bio;
1849 pe->full_bio_end_io = bio->bi_end_io;
1850
1851 account_start_copy(s);
1852 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1853 copy_callback, pe);
1854
1855 bio->bi_end_io = full_bio_end_io;
1856 bio->bi_private = callback_data;
1857
1858 submit_bio_noacct(bio);
1859}
1860
1861static struct dm_snap_pending_exception *
1862__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1863{
1864 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1865
1866 if (!e)
1867 return NULL;
1868
1869 return container_of(e, struct dm_snap_pending_exception, e);
1870}
1871
1872/*
1873 * Inserts a pending exception into the pending table.
1874 *
1875 * NOTE: a write lock must be held on the chunk's pending exception table slot
1876 * before calling this.
1877 */
1878static struct dm_snap_pending_exception *
1879__insert_pending_exception(struct dm_snapshot *s,
1880 struct dm_snap_pending_exception *pe, chunk_t chunk)
1881{
1882 pe->e.old_chunk = chunk;
1883 bio_list_init(&pe->origin_bios);
1884 bio_list_init(&pe->snapshot_bios);
1885 pe->started = 0;
1886 pe->full_bio = NULL;
1887
1888 spin_lock(&s->pe_allocation_lock);
1889 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1890 spin_unlock(&s->pe_allocation_lock);
1891 free_pending_exception(pe);
1892 return NULL;
1893 }
1894
1895 pe->exception_sequence = s->exception_start_sequence++;
1896 spin_unlock(&s->pe_allocation_lock);
1897
1898 dm_insert_exception(&s->pending, &pe->e);
1899
1900 return pe;
1901}
1902
1903/*
1904 * Looks to see if this snapshot already has a pending exception
1905 * for this chunk, otherwise it allocates a new one and inserts
1906 * it into the pending table.
1907 *
1908 * NOTE: a write lock must be held on the chunk's pending exception table slot
1909 * before calling this.
1910 */
1911static struct dm_snap_pending_exception *
1912__find_pending_exception(struct dm_snapshot *s,
1913 struct dm_snap_pending_exception *pe, chunk_t chunk)
1914{
1915 struct dm_snap_pending_exception *pe2;
1916
1917 pe2 = __lookup_pending_exception(s, chunk);
1918 if (pe2) {
1919 free_pending_exception(pe);
1920 return pe2;
1921 }
1922
1923 return __insert_pending_exception(s, pe, chunk);
1924}
1925
1926static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1927 struct bio *bio, chunk_t chunk)
1928{
1929 bio_set_dev(bio, s->cow->bdev);
1930 bio->bi_iter.bi_sector =
1931 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1932 (chunk - e->old_chunk)) +
1933 (bio->bi_iter.bi_sector & s->store->chunk_mask);
1934}
1935
1936static void zero_callback(int read_err, unsigned long write_err, void *context)
1937{
1938 struct bio *bio = context;
1939 struct dm_snapshot *s = bio->bi_private;
1940
1941 account_end_copy(s);
1942 bio->bi_status = write_err ? BLK_STS_IOERR : 0;
1943 bio_endio(bio);
1944}
1945
1946static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
1947 struct bio *bio, chunk_t chunk)
1948{
1949 struct dm_io_region dest;
1950
1951 dest.bdev = s->cow->bdev;
1952 dest.sector = bio->bi_iter.bi_sector;
1953 dest.count = s->store->chunk_size;
1954
1955 account_start_copy(s);
1956 WARN_ON_ONCE(bio->bi_private);
1957 bio->bi_private = s;
1958 dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
1959}
1960
1961static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)
1962{
1963 return bio->bi_iter.bi_size ==
1964 (s->store->chunk_size << SECTOR_SHIFT);
1965}
1966
1967static int snapshot_map(struct dm_target *ti, struct bio *bio)
1968{
1969 struct dm_exception *e;
1970 struct dm_snapshot *s = ti->private;
1971 int r = DM_MAPIO_REMAPPED;
1972 chunk_t chunk;
1973 struct dm_snap_pending_exception *pe = NULL;
1974 struct dm_exception_table_lock lock;
1975
1976 init_tracked_chunk(bio);
1977
1978 if (bio->bi_opf & REQ_PREFLUSH) {
1979 bio_set_dev(bio, s->cow->bdev);
1980 return DM_MAPIO_REMAPPED;
1981 }
1982
1983 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1984 dm_exception_table_lock_init(s, chunk, &lock);
1985
1986 /* Full snapshots are not usable */
1987 /* To get here the table must be live so s->active is always set. */
1988 if (!s->valid)
1989 return DM_MAPIO_KILL;
1990
1991 if (bio_data_dir(bio) == WRITE) {
1992 while (unlikely(!wait_for_in_progress(s, false)))
1993 ; /* wait_for_in_progress() has slept */
1994 }
1995
1996 down_read(&s->lock);
1997 dm_exception_table_lock(&lock);
1998
1999 if (!s->valid || (unlikely(s->snapshot_overflowed) &&
2000 bio_data_dir(bio) == WRITE)) {
2001 r = DM_MAPIO_KILL;
2002 goto out_unlock;
2003 }
2004
2005 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2006 if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {
2007 /*
2008 * passdown discard to origin (without triggering
2009 * snapshot exceptions via do_origin; doing so would
2010 * defeat the goal of freeing space in origin that is
2011 * implied by the "discard_passdown_origin" feature)
2012 */
2013 bio_set_dev(bio, s->origin->bdev);
2014 track_chunk(s, bio, chunk);
2015 goto out_unlock;
2016 }
2017 /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */
2018 }
2019
2020 /* If the block is already remapped - use that, else remap it */
2021 e = dm_lookup_exception(&s->complete, chunk);
2022 if (e) {
2023 remap_exception(s, e, bio, chunk);
2024 if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
2025 io_overlaps_chunk(s, bio)) {
2026 dm_exception_table_unlock(&lock);
2027 up_read(&s->lock);
2028 zero_exception(s, e, bio, chunk);
2029 r = DM_MAPIO_SUBMITTED; /* discard is not issued */
2030 goto out;
2031 }
2032 goto out_unlock;
2033 }
2034
2035 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2036 /*
2037 * If no exception exists, complete discard immediately
2038 * otherwise it'll trigger copy-out.
2039 */
2040 bio_endio(bio);
2041 r = DM_MAPIO_SUBMITTED;
2042 goto out_unlock;
2043 }
2044
2045 /*
2046 * Write to snapshot - higher level takes care of RW/RO
2047 * flags so we should only get this if we are
2048 * writeable.
2049 */
2050 if (bio_data_dir(bio) == WRITE) {
2051 pe = __lookup_pending_exception(s, chunk);
2052 if (!pe) {
2053 dm_exception_table_unlock(&lock);
2054 pe = alloc_pending_exception(s);
2055 dm_exception_table_lock(&lock);
2056
2057 e = dm_lookup_exception(&s->complete, chunk);
2058 if (e) {
2059 free_pending_exception(pe);
2060 remap_exception(s, e, bio, chunk);
2061 goto out_unlock;
2062 }
2063
2064 pe = __find_pending_exception(s, pe, chunk);
2065 if (!pe) {
2066 dm_exception_table_unlock(&lock);
2067 up_read(&s->lock);
2068
2069 down_write(&s->lock);
2070
2071 if (s->store->userspace_supports_overflow) {
2072 if (s->valid && !s->snapshot_overflowed) {
2073 s->snapshot_overflowed = 1;
2074 DMERR("Snapshot overflowed: Unable to allocate exception.");
2075 }
2076 } else
2077 __invalidate_snapshot(s, -ENOMEM);
2078 up_write(&s->lock);
2079
2080 r = DM_MAPIO_KILL;
2081 goto out;
2082 }
2083 }
2084
2085 remap_exception(s, &pe->e, bio, chunk);
2086
2087 r = DM_MAPIO_SUBMITTED;
2088
2089 if (!pe->started && io_overlaps_chunk(s, bio)) {
2090 pe->started = 1;
2091
2092 dm_exception_table_unlock(&lock);
2093 up_read(&s->lock);
2094
2095 start_full_bio(pe, bio);
2096 goto out;
2097 }
2098
2099 bio_list_add(&pe->snapshot_bios, bio);
2100
2101 if (!pe->started) {
2102 /* this is protected by the exception table lock */
2103 pe->started = 1;
2104
2105 dm_exception_table_unlock(&lock);
2106 up_read(&s->lock);
2107
2108 start_copy(pe);
2109 goto out;
2110 }
2111 } else {
2112 bio_set_dev(bio, s->origin->bdev);
2113 track_chunk(s, bio, chunk);
2114 }
2115
2116out_unlock:
2117 dm_exception_table_unlock(&lock);
2118 up_read(&s->lock);
2119out:
2120 return r;
2121}
2122
2123/*
2124 * A snapshot-merge target behaves like a combination of a snapshot
2125 * target and a snapshot-origin target. It only generates new
2126 * exceptions in other snapshots and not in the one that is being
2127 * merged.
2128 *
2129 * For each chunk, if there is an existing exception, it is used to
2130 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
2131 * which in turn might generate exceptions in other snapshots.
2132 * If merging is currently taking place on the chunk in question, the
2133 * I/O is deferred by adding it to s->bios_queued_during_merge.
2134 */
2135static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
2136{
2137 struct dm_exception *e;
2138 struct dm_snapshot *s = ti->private;
2139 int r = DM_MAPIO_REMAPPED;
2140 chunk_t chunk;
2141
2142 init_tracked_chunk(bio);
2143
2144 if (bio->bi_opf & REQ_PREFLUSH) {
2145 if (!dm_bio_get_target_bio_nr(bio))
2146 bio_set_dev(bio, s->origin->bdev);
2147 else
2148 bio_set_dev(bio, s->cow->bdev);
2149 return DM_MAPIO_REMAPPED;
2150 }
2151
2152 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
2153 /* Once merging, discards no longer effect change */
2154 bio_endio(bio);
2155 return DM_MAPIO_SUBMITTED;
2156 }
2157
2158 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
2159
2160 down_write(&s->lock);
2161
2162 /* Full merging snapshots are redirected to the origin */
2163 if (!s->valid)
2164 goto redirect_to_origin;
2165
2166 /* If the block is already remapped - use that */
2167 e = dm_lookup_exception(&s->complete, chunk);
2168 if (e) {
2169 /* Queue writes overlapping with chunks being merged */
2170 if (bio_data_dir(bio) == WRITE &&
2171 chunk >= s->first_merging_chunk &&
2172 chunk < (s->first_merging_chunk +
2173 s->num_merging_chunks)) {
2174 bio_set_dev(bio, s->origin->bdev);
2175 bio_list_add(&s->bios_queued_during_merge, bio);
2176 r = DM_MAPIO_SUBMITTED;
2177 goto out_unlock;
2178 }
2179
2180 remap_exception(s, e, bio, chunk);
2181
2182 if (bio_data_dir(bio) == WRITE)
2183 track_chunk(s, bio, chunk);
2184 goto out_unlock;
2185 }
2186
2187redirect_to_origin:
2188 bio_set_dev(bio, s->origin->bdev);
2189
2190 if (bio_data_dir(bio) == WRITE) {
2191 up_write(&s->lock);
2192 return do_origin(s->origin, bio, false);
2193 }
2194
2195out_unlock:
2196 up_write(&s->lock);
2197
2198 return r;
2199}
2200
2201static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
2202 blk_status_t *error)
2203{
2204 struct dm_snapshot *s = ti->private;
2205
2206 if (is_bio_tracked(bio))
2207 stop_tracking_chunk(s, bio);
2208
2209 return DM_ENDIO_DONE;
2210}
2211
2212static void snapshot_merge_presuspend(struct dm_target *ti)
2213{
2214 struct dm_snapshot *s = ti->private;
2215
2216 stop_merge(s);
2217}
2218
2219static int snapshot_preresume(struct dm_target *ti)
2220{
2221 int r = 0;
2222 struct dm_snapshot *s = ti->private;
2223 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2224
2225 down_read(&_origins_lock);
2226 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2227 if (snap_src && snap_dest) {
2228 down_read(&snap_src->lock);
2229 if (s == snap_src) {
2230 DMERR("Unable to resume snapshot source until "
2231 "handover completes.");
2232 r = -EINVAL;
2233 } else if (!dm_suspended(snap_src->ti)) {
2234 DMERR("Unable to perform snapshot handover until "
2235 "source is suspended.");
2236 r = -EINVAL;
2237 }
2238 up_read(&snap_src->lock);
2239 }
2240 up_read(&_origins_lock);
2241
2242 return r;
2243}
2244
2245static void snapshot_resume(struct dm_target *ti)
2246{
2247 struct dm_snapshot *s = ti->private;
2248 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
2249 struct dm_origin *o;
2250 struct mapped_device *origin_md = NULL;
2251 bool must_restart_merging = false;
2252
2253 down_read(&_origins_lock);
2254
2255 o = __lookup_dm_origin(s->origin->bdev);
2256 if (o)
2257 origin_md = dm_table_get_md(o->ti->table);
2258 if (!origin_md) {
2259 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
2260 if (snap_merging)
2261 origin_md = dm_table_get_md(snap_merging->ti->table);
2262 }
2263 if (origin_md == dm_table_get_md(ti->table))
2264 origin_md = NULL;
2265 if (origin_md) {
2266 if (dm_hold(origin_md))
2267 origin_md = NULL;
2268 }
2269
2270 up_read(&_origins_lock);
2271
2272 if (origin_md) {
2273 dm_internal_suspend_fast(origin_md);
2274 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
2275 must_restart_merging = true;
2276 stop_merge(snap_merging);
2277 }
2278 }
2279
2280 down_read(&_origins_lock);
2281
2282 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
2283 if (snap_src && snap_dest) {
2284 down_write(&snap_src->lock);
2285 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
2286 __handover_exceptions(snap_src, snap_dest);
2287 up_write(&snap_dest->lock);
2288 up_write(&snap_src->lock);
2289 }
2290
2291 up_read(&_origins_lock);
2292
2293 if (origin_md) {
2294 if (must_restart_merging)
2295 start_merge(snap_merging);
2296 dm_internal_resume_fast(origin_md);
2297 dm_put(origin_md);
2298 }
2299
2300 /* Now we have correct chunk size, reregister */
2301 reregister_snapshot(s);
2302
2303 down_write(&s->lock);
2304 s->active = 1;
2305 up_write(&s->lock);
2306}
2307
2308static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
2309{
2310 uint32_t min_chunksize;
2311
2312 down_read(&_origins_lock);
2313 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
2314 up_read(&_origins_lock);
2315
2316 return min_chunksize;
2317}
2318
2319static void snapshot_merge_resume(struct dm_target *ti)
2320{
2321 struct dm_snapshot *s = ti->private;
2322
2323 /*
2324 * Handover exceptions from existing snapshot.
2325 */
2326 snapshot_resume(ti);
2327
2328 /*
2329 * snapshot-merge acts as an origin, so set ti->max_io_len
2330 */
2331 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
2332
2333 start_merge(s);
2334}
2335
2336static void snapshot_status(struct dm_target *ti, status_type_t type,
2337 unsigned status_flags, char *result, unsigned maxlen)
2338{
2339 unsigned sz = 0;
2340 struct dm_snapshot *snap = ti->private;
2341 unsigned num_features;
2342
2343 switch (type) {
2344 case STATUSTYPE_INFO:
2345
2346 down_write(&snap->lock);
2347
2348 if (!snap->valid)
2349 DMEMIT("Invalid");
2350 else if (snap->merge_failed)
2351 DMEMIT("Merge failed");
2352 else if (snap->snapshot_overflowed)
2353 DMEMIT("Overflow");
2354 else {
2355 if (snap->store->type->usage) {
2356 sector_t total_sectors, sectors_allocated,
2357 metadata_sectors;
2358 snap->store->type->usage(snap->store,
2359 &total_sectors,
2360 §ors_allocated,
2361 &metadata_sectors);
2362 DMEMIT("%llu/%llu %llu",
2363 (unsigned long long)sectors_allocated,
2364 (unsigned long long)total_sectors,
2365 (unsigned long long)metadata_sectors);
2366 }
2367 else
2368 DMEMIT("Unknown");
2369 }
2370
2371 up_write(&snap->lock);
2372
2373 break;
2374
2375 case STATUSTYPE_TABLE:
2376 /*
2377 * kdevname returns a static pointer so we need
2378 * to make private copies if the output is to
2379 * make sense.
2380 */
2381 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2382 sz += snap->store->type->status(snap->store, type, result + sz,
2383 maxlen - sz);
2384 num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;
2385 if (num_features) {
2386 DMEMIT(" %u", num_features);
2387 if (snap->discard_zeroes_cow)
2388 DMEMIT(" discard_zeroes_cow");
2389 if (snap->discard_passdown_origin)
2390 DMEMIT(" discard_passdown_origin");
2391 }
2392 break;
2393 }
2394}
2395
2396static int snapshot_iterate_devices(struct dm_target *ti,
2397 iterate_devices_callout_fn fn, void *data)
2398{
2399 struct dm_snapshot *snap = ti->private;
2400 int r;
2401
2402 r = fn(ti, snap->origin, 0, ti->len, data);
2403
2404 if (!r)
2405 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2406
2407 return r;
2408}
2409
2410static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
2411{
2412 struct dm_snapshot *snap = ti->private;
2413
2414 if (snap->discard_zeroes_cow) {
2415 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
2416
2417 down_read(&_origins_lock);
2418
2419 (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);
2420 if (snap_src && snap_dest)
2421 snap = snap_src;
2422
2423 /* All discards are split on chunk_size boundary */
2424 limits->discard_granularity = snap->store->chunk_size;
2425 limits->max_discard_sectors = snap->store->chunk_size;
2426
2427 up_read(&_origins_lock);
2428 }
2429}
2430
2431/*-----------------------------------------------------------------
2432 * Origin methods
2433 *---------------------------------------------------------------*/
2434
2435/*
2436 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2437 * supplied bio was ignored. The caller may submit it immediately.
2438 * (No remapping actually occurs as the origin is always a direct linear
2439 * map.)
2440 *
2441 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2442 * and any supplied bio is added to a list to be submitted once all
2443 * the necessary exceptions exist.
2444 */
2445static int __origin_write(struct list_head *snapshots, sector_t sector,
2446 struct bio *bio)
2447{
2448 int r = DM_MAPIO_REMAPPED;
2449 struct dm_snapshot *snap;
2450 struct dm_exception *e;
2451 struct dm_snap_pending_exception *pe, *pe2;
2452 struct dm_snap_pending_exception *pe_to_start_now = NULL;
2453 struct dm_snap_pending_exception *pe_to_start_last = NULL;
2454 struct dm_exception_table_lock lock;
2455 chunk_t chunk;
2456
2457 /* Do all the snapshots on this origin */
2458 list_for_each_entry (snap, snapshots, list) {
2459 /*
2460 * Don't make new exceptions in a merging snapshot
2461 * because it has effectively been deleted
2462 */
2463 if (dm_target_is_snapshot_merge(snap->ti))
2464 continue;
2465
2466 /* Nothing to do if writing beyond end of snapshot */
2467 if (sector >= dm_table_get_size(snap->ti->table))
2468 continue;
2469
2470 /*
2471 * Remember, different snapshots can have
2472 * different chunk sizes.
2473 */
2474 chunk = sector_to_chunk(snap->store, sector);
2475 dm_exception_table_lock_init(snap, chunk, &lock);
2476
2477 down_read(&snap->lock);
2478 dm_exception_table_lock(&lock);
2479
2480 /* Only deal with valid and active snapshots */
2481 if (!snap->valid || !snap->active)
2482 goto next_snapshot;
2483
2484 pe = __lookup_pending_exception(snap, chunk);
2485 if (!pe) {
2486 /*
2487 * Check exception table to see if block is already
2488 * remapped in this snapshot and trigger an exception
2489 * if not.
2490 */
2491 e = dm_lookup_exception(&snap->complete, chunk);
2492 if (e)
2493 goto next_snapshot;
2494
2495 dm_exception_table_unlock(&lock);
2496 pe = alloc_pending_exception(snap);
2497 dm_exception_table_lock(&lock);
2498
2499 pe2 = __lookup_pending_exception(snap, chunk);
2500
2501 if (!pe2) {
2502 e = dm_lookup_exception(&snap->complete, chunk);
2503 if (e) {
2504 free_pending_exception(pe);
2505 goto next_snapshot;
2506 }
2507
2508 pe = __insert_pending_exception(snap, pe, chunk);
2509 if (!pe) {
2510 dm_exception_table_unlock(&lock);
2511 up_read(&snap->lock);
2512
2513 invalidate_snapshot(snap, -ENOMEM);
2514 continue;
2515 }
2516 } else {
2517 free_pending_exception(pe);
2518 pe = pe2;
2519 }
2520 }
2521
2522 r = DM_MAPIO_SUBMITTED;
2523
2524 /*
2525 * If an origin bio was supplied, queue it to wait for the
2526 * completion of this exception, and start this one last,
2527 * at the end of the function.
2528 */
2529 if (bio) {
2530 bio_list_add(&pe->origin_bios, bio);
2531 bio = NULL;
2532
2533 if (!pe->started) {
2534 pe->started = 1;
2535 pe_to_start_last = pe;
2536 }
2537 }
2538
2539 if (!pe->started) {
2540 pe->started = 1;
2541 pe_to_start_now = pe;
2542 }
2543
2544next_snapshot:
2545 dm_exception_table_unlock(&lock);
2546 up_read(&snap->lock);
2547
2548 if (pe_to_start_now) {
2549 start_copy(pe_to_start_now);
2550 pe_to_start_now = NULL;
2551 }
2552 }
2553
2554 /*
2555 * Submit the exception against which the bio is queued last,
2556 * to give the other exceptions a head start.
2557 */
2558 if (pe_to_start_last)
2559 start_copy(pe_to_start_last);
2560
2561 return r;
2562}
2563
2564/*
2565 * Called on a write from the origin driver.
2566 */
2567static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
2568{
2569 struct origin *o;
2570 int r = DM_MAPIO_REMAPPED;
2571
2572again:
2573 down_read(&_origins_lock);
2574 o = __lookup_origin(origin->bdev);
2575 if (o) {
2576 if (limit) {
2577 struct dm_snapshot *s;
2578 list_for_each_entry(s, &o->snapshots, list)
2579 if (unlikely(!wait_for_in_progress(s, true)))
2580 goto again;
2581 }
2582
2583 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
2584 }
2585 up_read(&_origins_lock);
2586
2587 return r;
2588}
2589
2590/*
2591 * Trigger exceptions in all non-merging snapshots.
2592 *
2593 * The chunk size of the merging snapshot may be larger than the chunk
2594 * size of some other snapshot so we may need to reallocate multiple
2595 * chunks in other snapshots.
2596 *
2597 * We scan all the overlapping exceptions in the other snapshots.
2598 * Returns 1 if anything was reallocated and must be waited for,
2599 * otherwise returns 0.
2600 *
2601 * size must be a multiple of merging_snap's chunk_size.
2602 */
2603static int origin_write_extent(struct dm_snapshot *merging_snap,
2604 sector_t sector, unsigned size)
2605{
2606 int must_wait = 0;
2607 sector_t n;
2608 struct origin *o;
2609
2610 /*
2611 * The origin's __minimum_chunk_size() got stored in max_io_len
2612 * by snapshot_merge_resume().
2613 */
2614 down_read(&_origins_lock);
2615 o = __lookup_origin(merging_snap->origin->bdev);
2616 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2617 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2618 DM_MAPIO_SUBMITTED)
2619 must_wait = 1;
2620 up_read(&_origins_lock);
2621
2622 return must_wait;
2623}
2624
2625/*
2626 * Origin: maps a linear range of a device, with hooks for snapshotting.
2627 */
2628
2629/*
2630 * Construct an origin mapping: <dev_path>
2631 * The context for an origin is merely a 'struct dm_dev *'
2632 * pointing to the real device.
2633 */
2634static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2635{
2636 int r;
2637 struct dm_origin *o;
2638
2639 if (argc != 1) {
2640 ti->error = "origin: incorrect number of arguments";
2641 return -EINVAL;
2642 }
2643
2644 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2645 if (!o) {
2646 ti->error = "Cannot allocate private origin structure";
2647 r = -ENOMEM;
2648 goto bad_alloc;
2649 }
2650
2651 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2652 if (r) {
2653 ti->error = "Cannot get target device";
2654 goto bad_open;
2655 }
2656
2657 o->ti = ti;
2658 ti->private = o;
2659 ti->num_flush_bios = 1;
2660
2661 return 0;
2662
2663bad_open:
2664 kfree(o);
2665bad_alloc:
2666 return r;
2667}
2668
2669static void origin_dtr(struct dm_target *ti)
2670{
2671 struct dm_origin *o = ti->private;
2672
2673 dm_put_device(ti, o->dev);
2674 kfree(o);
2675}
2676
2677static int origin_map(struct dm_target *ti, struct bio *bio)
2678{
2679 struct dm_origin *o = ti->private;
2680 unsigned available_sectors;
2681
2682 bio_set_dev(bio, o->dev->bdev);
2683
2684 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2685 return DM_MAPIO_REMAPPED;
2686
2687 if (bio_data_dir(bio) != WRITE)
2688 return DM_MAPIO_REMAPPED;
2689
2690 available_sectors = o->split_boundary -
2691 ((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2692
2693 if (bio_sectors(bio) > available_sectors)
2694 dm_accept_partial_bio(bio, available_sectors);
2695
2696 /* Only tell snapshots if this is a write */
2697 return do_origin(o->dev, bio, true);
2698}
2699
2700/*
2701 * Set the target "max_io_len" field to the minimum of all the snapshots'
2702 * chunk sizes.
2703 */
2704static void origin_resume(struct dm_target *ti)
2705{
2706 struct dm_origin *o = ti->private;
2707
2708 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2709
2710 down_write(&_origins_lock);
2711 __insert_dm_origin(o);
2712 up_write(&_origins_lock);
2713}
2714
2715static void origin_postsuspend(struct dm_target *ti)
2716{
2717 struct dm_origin *o = ti->private;
2718
2719 down_write(&_origins_lock);
2720 __remove_dm_origin(o);
2721 up_write(&_origins_lock);
2722}
2723
2724static void origin_status(struct dm_target *ti, status_type_t type,
2725 unsigned status_flags, char *result, unsigned maxlen)
2726{
2727 struct dm_origin *o = ti->private;
2728
2729 switch (type) {
2730 case STATUSTYPE_INFO:
2731 result[0] = '\0';
2732 break;
2733
2734 case STATUSTYPE_TABLE:
2735 snprintf(result, maxlen, "%s", o->dev->name);
2736 break;
2737 }
2738}
2739
2740static int origin_iterate_devices(struct dm_target *ti,
2741 iterate_devices_callout_fn fn, void *data)
2742{
2743 struct dm_origin *o = ti->private;
2744
2745 return fn(ti, o->dev, 0, ti->len, data);
2746}
2747
2748static struct target_type origin_target = {
2749 .name = "snapshot-origin",
2750 .version = {1, 9, 0},
2751 .module = THIS_MODULE,
2752 .ctr = origin_ctr,
2753 .dtr = origin_dtr,
2754 .map = origin_map,
2755 .resume = origin_resume,
2756 .postsuspend = origin_postsuspend,
2757 .status = origin_status,
2758 .iterate_devices = origin_iterate_devices,
2759};
2760
2761static struct target_type snapshot_target = {
2762 .name = "snapshot",
2763 .version = {1, 16, 0},
2764 .module = THIS_MODULE,
2765 .ctr = snapshot_ctr,
2766 .dtr = snapshot_dtr,
2767 .map = snapshot_map,
2768 .end_io = snapshot_end_io,
2769 .preresume = snapshot_preresume,
2770 .resume = snapshot_resume,
2771 .status = snapshot_status,
2772 .iterate_devices = snapshot_iterate_devices,
2773 .io_hints = snapshot_io_hints,
2774};
2775
2776static struct target_type merge_target = {
2777 .name = dm_snapshot_merge_target_name,
2778 .version = {1, 5, 0},
2779 .module = THIS_MODULE,
2780 .ctr = snapshot_ctr,
2781 .dtr = snapshot_dtr,
2782 .map = snapshot_merge_map,
2783 .end_io = snapshot_end_io,
2784 .presuspend = snapshot_merge_presuspend,
2785 .preresume = snapshot_preresume,
2786 .resume = snapshot_merge_resume,
2787 .status = snapshot_status,
2788 .iterate_devices = snapshot_iterate_devices,
2789 .io_hints = snapshot_io_hints,
2790};
2791
2792static int __init dm_snapshot_init(void)
2793{
2794 int r;
2795
2796 r = dm_exception_store_init();
2797 if (r) {
2798 DMERR("Failed to initialize exception stores");
2799 return r;
2800 }
2801
2802 r = init_origin_hash();
2803 if (r) {
2804 DMERR("init_origin_hash failed.");
2805 goto bad_origin_hash;
2806 }
2807
2808 exception_cache = KMEM_CACHE(dm_exception, 0);
2809 if (!exception_cache) {
2810 DMERR("Couldn't create exception cache.");
2811 r = -ENOMEM;
2812 goto bad_exception_cache;
2813 }
2814
2815 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2816 if (!pending_cache) {
2817 DMERR("Couldn't create pending cache.");
2818 r = -ENOMEM;
2819 goto bad_pending_cache;
2820 }
2821
2822 r = dm_register_target(&snapshot_target);
2823 if (r < 0) {
2824 DMERR("snapshot target register failed %d", r);
2825 goto bad_register_snapshot_target;
2826 }
2827
2828 r = dm_register_target(&origin_target);
2829 if (r < 0) {
2830 DMERR("Origin target register failed %d", r);
2831 goto bad_register_origin_target;
2832 }
2833
2834 r = dm_register_target(&merge_target);
2835 if (r < 0) {
2836 DMERR("Merge target register failed %d", r);
2837 goto bad_register_merge_target;
2838 }
2839
2840 return 0;
2841
2842bad_register_merge_target:
2843 dm_unregister_target(&origin_target);
2844bad_register_origin_target:
2845 dm_unregister_target(&snapshot_target);
2846bad_register_snapshot_target:
2847 kmem_cache_destroy(pending_cache);
2848bad_pending_cache:
2849 kmem_cache_destroy(exception_cache);
2850bad_exception_cache:
2851 exit_origin_hash();
2852bad_origin_hash:
2853 dm_exception_store_exit();
2854
2855 return r;
2856}
2857
2858static void __exit dm_snapshot_exit(void)
2859{
2860 dm_unregister_target(&snapshot_target);
2861 dm_unregister_target(&origin_target);
2862 dm_unregister_target(&merge_target);
2863
2864 exit_origin_hash();
2865 kmem_cache_destroy(pending_cache);
2866 kmem_cache_destroy(exception_cache);
2867
2868 dm_exception_store_exit();
2869}
2870
2871/* Module hooks */
2872module_init(dm_snapshot_init);
2873module_exit(dm_snapshot_exit);
2874
2875MODULE_DESCRIPTION(DM_NAME " snapshot target");
2876MODULE_AUTHOR("Joe Thornber");
2877MODULE_LICENSE("GPL");
2878MODULE_ALIAS("dm-snapshot-origin");
2879MODULE_ALIAS("dm-snapshot-merge");