cifs: fix oops while traversing open file list (try #4)
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / md / dm-snap.c
blob9ecff5f3023a4c4f0721b958ef1541e762e910ff
1 /*
2 * dm-snapshot.c
4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
6 * This file is released under the GPL.
7 */
9 #include <linux/blkdev.h>
10 #include <linux/device-mapper.h>
11 #include <linux/delay.h>
12 #include <linux/fs.h>
13 #include <linux/init.h>
14 #include <linux/kdev_t.h>
15 #include <linux/list.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/log2.h>
21 #include <linux/dm-kcopyd.h>
23 #include "dm-exception-store.h"
25 #define DM_MSG_PREFIX "snapshots"
27 static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
29 #define dm_target_is_snapshot_merge(ti) \
30 ((ti)->type->name == dm_snapshot_merge_target_name)
33 * The percentage increment we will wake up users at
35 #define WAKE_UP_PERCENT 5
38 * kcopyd priority of snapshot operations
40 #define SNAPSHOT_COPY_PRIORITY 2
43 * The size of the mempool used to track chunks in use.
45 #define MIN_IOS 256
47 #define DM_TRACKED_CHUNK_HASH_SIZE 16
48 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
49 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
51 struct dm_exception_table {
52 uint32_t hash_mask;
53 unsigned hash_shift;
54 struct list_head *table;
57 struct dm_snapshot {
58 struct rw_semaphore lock;
60 struct dm_dev *origin;
61 struct dm_dev *cow;
63 struct dm_target *ti;
65 /* List of snapshots per Origin */
66 struct list_head list;
69 * You can't use a snapshot if this is 0 (e.g. if full).
70 * A snapshot-merge target never clears this.
72 int valid;
74 /* Origin writes don't trigger exceptions until this is set */
75 int active;
77 atomic_t pending_exceptions_count;
79 mempool_t *pending_pool;
81 struct dm_exception_table pending;
82 struct dm_exception_table complete;
85 * pe_lock protects all pending_exception operations and access
86 * as well as the snapshot_bios list.
88 spinlock_t pe_lock;
90 /* Chunks with outstanding reads */
91 spinlock_t tracked_chunk_lock;
92 mempool_t *tracked_chunk_pool;
93 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
95 /* The on disk metadata handler */
96 struct dm_exception_store *store;
98 struct dm_kcopyd_client *kcopyd_client;
100 /* Wait for events based on state_bits */
101 unsigned long state_bits;
103 /* Range of chunks currently being merged. */
104 chunk_t first_merging_chunk;
105 int num_merging_chunks;
108 * The merge operation failed if this flag is set.
109 * Failure modes are handled as follows:
110 * - I/O error reading the header
111 * => don't load the target; abort.
112 * - Header does not have "valid" flag set
113 * => use the origin; forget about the snapshot.
114 * - I/O error when reading exceptions
115 * => don't load the target; abort.
116 * (We can't use the intermediate origin state.)
117 * - I/O error while merging
118 * => stop merging; set merge_failed; process I/O normally.
120 int merge_failed;
123 * Incoming bios that overlap with chunks being merged must wait
124 * for them to be committed.
126 struct bio_list bios_queued_during_merge;
130 * state_bits:
131 * RUNNING_MERGE - Merge operation is in progress.
132 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
133 * cleared afterwards.
135 #define RUNNING_MERGE 0
136 #define SHUTDOWN_MERGE 1
138 struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
140 return s->origin;
142 EXPORT_SYMBOL(dm_snap_origin);
144 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
146 return s->cow;
148 EXPORT_SYMBOL(dm_snap_cow);
150 static sector_t chunk_to_sector(struct dm_exception_store *store,
151 chunk_t chunk)
153 return chunk << store->chunk_shift;
156 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
159 * There is only ever one instance of a particular block
160 * device so we can compare pointers safely.
162 return lhs == rhs;
165 struct dm_snap_pending_exception {
166 struct dm_exception e;
169 * Origin buffers waiting for this to complete are held
170 * in a bio list
172 struct bio_list origin_bios;
173 struct bio_list snapshot_bios;
175 /* Pointer back to snapshot context */
176 struct dm_snapshot *snap;
179 * 1 indicates the exception has already been sent to
180 * kcopyd.
182 int started;
186 * Hash table mapping origin volumes to lists of snapshots and
187 * a lock to protect it
189 static struct kmem_cache *exception_cache;
190 static struct kmem_cache *pending_cache;
192 struct dm_snap_tracked_chunk {
193 struct hlist_node node;
194 chunk_t chunk;
197 static struct kmem_cache *tracked_chunk_cache;
199 static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
200 chunk_t chunk)
202 struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
203 GFP_NOIO);
204 unsigned long flags;
206 c->chunk = chunk;
208 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
209 hlist_add_head(&c->node,
210 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
211 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
213 return c;
216 static void stop_tracking_chunk(struct dm_snapshot *s,
217 struct dm_snap_tracked_chunk *c)
219 unsigned long flags;
221 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
222 hlist_del(&c->node);
223 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
225 mempool_free(c, s->tracked_chunk_pool);
228 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
230 struct dm_snap_tracked_chunk *c;
231 struct hlist_node *hn;
232 int found = 0;
234 spin_lock_irq(&s->tracked_chunk_lock);
236 hlist_for_each_entry(c, hn,
237 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
238 if (c->chunk == chunk) {
239 found = 1;
240 break;
244 spin_unlock_irq(&s->tracked_chunk_lock);
246 return found;
250 * This conflicting I/O is extremely improbable in the caller,
251 * so msleep(1) is sufficient and there is no need for a wait queue.
253 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
255 while (__chunk_is_tracked(s, chunk))
256 msleep(1);
260 * One of these per registered origin, held in the snapshot_origins hash
262 struct origin {
263 /* The origin device */
264 struct block_device *bdev;
266 struct list_head hash_list;
268 /* List of snapshots for this origin */
269 struct list_head snapshots;
273 * Size of the hash table for origin volumes. If we make this
274 * the size of the minors list then it should be nearly perfect
276 #define ORIGIN_HASH_SIZE 256
277 #define ORIGIN_MASK 0xFF
278 static struct list_head *_origins;
279 static struct rw_semaphore _origins_lock;
281 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
282 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
283 static uint64_t _pending_exceptions_done_count;
285 static int init_origin_hash(void)
287 int i;
289 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
290 GFP_KERNEL);
291 if (!_origins) {
292 DMERR("unable to allocate memory");
293 return -ENOMEM;
296 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
297 INIT_LIST_HEAD(_origins + i);
298 init_rwsem(&_origins_lock);
300 return 0;
303 static void exit_origin_hash(void)
305 kfree(_origins);
308 static unsigned origin_hash(struct block_device *bdev)
310 return bdev->bd_dev & ORIGIN_MASK;
313 static struct origin *__lookup_origin(struct block_device *origin)
315 struct list_head *ol;
316 struct origin *o;
318 ol = &_origins[origin_hash(origin)];
319 list_for_each_entry (o, ol, hash_list)
320 if (bdev_equal(o->bdev, origin))
321 return o;
323 return NULL;
326 static void __insert_origin(struct origin *o)
328 struct list_head *sl = &_origins[origin_hash(o->bdev)];
329 list_add_tail(&o->hash_list, sl);
333 * _origins_lock must be held when calling this function.
334 * Returns number of snapshots registered using the supplied cow device, plus:
335 * snap_src - a snapshot suitable for use as a source of exception handover
336 * snap_dest - a snapshot capable of receiving exception handover.
337 * snap_merge - an existing snapshot-merge target linked to the same origin.
338 * There can be at most one snapshot-merge target. The parameter is optional.
340 * Possible return values and states of snap_src and snap_dest.
341 * 0: NULL, NULL - first new snapshot
342 * 1: snap_src, NULL - normal snapshot
343 * 2: snap_src, snap_dest - waiting for handover
344 * 2: snap_src, NULL - handed over, waiting for old to be deleted
345 * 1: NULL, snap_dest - source got destroyed without handover
347 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
348 struct dm_snapshot **snap_src,
349 struct dm_snapshot **snap_dest,
350 struct dm_snapshot **snap_merge)
352 struct dm_snapshot *s;
353 struct origin *o;
354 int count = 0;
355 int active;
357 o = __lookup_origin(snap->origin->bdev);
358 if (!o)
359 goto out;
361 list_for_each_entry(s, &o->snapshots, list) {
362 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
363 *snap_merge = s;
364 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
365 continue;
367 down_read(&s->lock);
368 active = s->active;
369 up_read(&s->lock);
371 if (active) {
372 if (snap_src)
373 *snap_src = s;
374 } else if (snap_dest)
375 *snap_dest = s;
377 count++;
380 out:
381 return count;
385 * On success, returns 1 if this snapshot is a handover destination,
386 * otherwise returns 0.
388 static int __validate_exception_handover(struct dm_snapshot *snap)
390 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
391 struct dm_snapshot *snap_merge = NULL;
393 /* Does snapshot need exceptions handed over to it? */
394 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
395 &snap_merge) == 2) ||
396 snap_dest) {
397 snap->ti->error = "Snapshot cow pairing for exception "
398 "table handover failed";
399 return -EINVAL;
403 * If no snap_src was found, snap cannot become a handover
404 * destination.
406 if (!snap_src)
407 return 0;
410 * Non-snapshot-merge handover?
412 if (!dm_target_is_snapshot_merge(snap->ti))
413 return 1;
416 * Do not allow more than one merging snapshot.
418 if (snap_merge) {
419 snap->ti->error = "A snapshot is already merging.";
420 return -EINVAL;
423 if (!snap_src->store->type->prepare_merge ||
424 !snap_src->store->type->commit_merge) {
425 snap->ti->error = "Snapshot exception store does not "
426 "support snapshot-merge.";
427 return -EINVAL;
430 return 1;
433 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
435 struct dm_snapshot *l;
437 /* Sort the list according to chunk size, largest-first smallest-last */
438 list_for_each_entry(l, &o->snapshots, list)
439 if (l->store->chunk_size < s->store->chunk_size)
440 break;
441 list_add_tail(&s->list, &l->list);
445 * Make a note of the snapshot and its origin so we can look it
446 * up when the origin has a write on it.
448 * Also validate snapshot exception store handovers.
449 * On success, returns 1 if this registration is a handover destination,
450 * otherwise returns 0.
452 static int register_snapshot(struct dm_snapshot *snap)
454 struct origin *o, *new_o = NULL;
455 struct block_device *bdev = snap->origin->bdev;
456 int r = 0;
458 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
459 if (!new_o)
460 return -ENOMEM;
462 down_write(&_origins_lock);
464 r = __validate_exception_handover(snap);
465 if (r < 0) {
466 kfree(new_o);
467 goto out;
470 o = __lookup_origin(bdev);
471 if (o)
472 kfree(new_o);
473 else {
474 /* New origin */
475 o = new_o;
477 /* Initialise the struct */
478 INIT_LIST_HEAD(&o->snapshots);
479 o->bdev = bdev;
481 __insert_origin(o);
484 __insert_snapshot(o, snap);
486 out:
487 up_write(&_origins_lock);
489 return r;
493 * Move snapshot to correct place in list according to chunk size.
495 static void reregister_snapshot(struct dm_snapshot *s)
497 struct block_device *bdev = s->origin->bdev;
499 down_write(&_origins_lock);
501 list_del(&s->list);
502 __insert_snapshot(__lookup_origin(bdev), s);
504 up_write(&_origins_lock);
507 static void unregister_snapshot(struct dm_snapshot *s)
509 struct origin *o;
511 down_write(&_origins_lock);
512 o = __lookup_origin(s->origin->bdev);
514 list_del(&s->list);
515 if (o && list_empty(&o->snapshots)) {
516 list_del(&o->hash_list);
517 kfree(o);
520 up_write(&_origins_lock);
524 * Implementation of the exception hash tables.
525 * The lowest hash_shift bits of the chunk number are ignored, allowing
526 * some consecutive chunks to be grouped together.
528 static int dm_exception_table_init(struct dm_exception_table *et,
529 uint32_t size, unsigned hash_shift)
531 unsigned int i;
533 et->hash_shift = hash_shift;
534 et->hash_mask = size - 1;
535 et->table = dm_vcalloc(size, sizeof(struct list_head));
536 if (!et->table)
537 return -ENOMEM;
539 for (i = 0; i < size; i++)
540 INIT_LIST_HEAD(et->table + i);
542 return 0;
545 static void dm_exception_table_exit(struct dm_exception_table *et,
546 struct kmem_cache *mem)
548 struct list_head *slot;
549 struct dm_exception *ex, *next;
550 int i, size;
552 size = et->hash_mask + 1;
553 for (i = 0; i < size; i++) {
554 slot = et->table + i;
556 list_for_each_entry_safe (ex, next, slot, hash_list)
557 kmem_cache_free(mem, ex);
560 vfree(et->table);
563 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
565 return (chunk >> et->hash_shift) & et->hash_mask;
568 static void dm_remove_exception(struct dm_exception *e)
570 list_del(&e->hash_list);
574 * Return the exception data for a sector, or NULL if not
575 * remapped.
577 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
578 chunk_t chunk)
580 struct list_head *slot;
581 struct dm_exception *e;
583 slot = &et->table[exception_hash(et, chunk)];
584 list_for_each_entry (e, slot, hash_list)
585 if (chunk >= e->old_chunk &&
586 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
587 return e;
589 return NULL;
592 static struct dm_exception *alloc_completed_exception(void)
594 struct dm_exception *e;
596 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
597 if (!e)
598 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
600 return e;
603 static void free_completed_exception(struct dm_exception *e)
605 kmem_cache_free(exception_cache, e);
608 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
610 struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
611 GFP_NOIO);
613 atomic_inc(&s->pending_exceptions_count);
614 pe->snap = s;
616 return pe;
619 static void free_pending_exception(struct dm_snap_pending_exception *pe)
621 struct dm_snapshot *s = pe->snap;
623 mempool_free(pe, s->pending_pool);
624 smp_mb__before_atomic_dec();
625 atomic_dec(&s->pending_exceptions_count);
628 static void dm_insert_exception(struct dm_exception_table *eh,
629 struct dm_exception *new_e)
631 struct list_head *l;
632 struct dm_exception *e = NULL;
634 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
636 /* Add immediately if this table doesn't support consecutive chunks */
637 if (!eh->hash_shift)
638 goto out;
640 /* List is ordered by old_chunk */
641 list_for_each_entry_reverse(e, l, hash_list) {
642 /* Insert after an existing chunk? */
643 if (new_e->old_chunk == (e->old_chunk +
644 dm_consecutive_chunk_count(e) + 1) &&
645 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
646 dm_consecutive_chunk_count(e) + 1)) {
647 dm_consecutive_chunk_count_inc(e);
648 free_completed_exception(new_e);
649 return;
652 /* Insert before an existing chunk? */
653 if (new_e->old_chunk == (e->old_chunk - 1) &&
654 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
655 dm_consecutive_chunk_count_inc(e);
656 e->old_chunk--;
657 e->new_chunk--;
658 free_completed_exception(new_e);
659 return;
662 if (new_e->old_chunk > e->old_chunk)
663 break;
666 out:
667 list_add(&new_e->hash_list, e ? &e->hash_list : l);
671 * Callback used by the exception stores to load exceptions when
672 * initialising.
674 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
676 struct dm_snapshot *s = context;
677 struct dm_exception *e;
679 e = alloc_completed_exception();
680 if (!e)
681 return -ENOMEM;
683 e->old_chunk = old;
685 /* Consecutive_count is implicitly initialised to zero */
686 e->new_chunk = new;
688 dm_insert_exception(&s->complete, e);
690 return 0;
694 * Return a minimum chunk size of all snapshots that have the specified origin.
695 * Return zero if the origin has no snapshots.
697 static sector_t __minimum_chunk_size(struct origin *o)
699 struct dm_snapshot *snap;
700 unsigned chunk_size = 0;
702 if (o)
703 list_for_each_entry(snap, &o->snapshots, list)
704 chunk_size = min_not_zero(chunk_size,
705 snap->store->chunk_size);
707 return chunk_size;
711 * Hard coded magic.
713 static int calc_max_buckets(void)
715 /* use a fixed size of 2MB */
716 unsigned long mem = 2 * 1024 * 1024;
717 mem /= sizeof(struct list_head);
719 return mem;
723 * Allocate room for a suitable hash table.
725 static int init_hash_tables(struct dm_snapshot *s)
727 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
730 * Calculate based on the size of the original volume or
731 * the COW volume...
733 cow_dev_size = get_dev_size(s->cow->bdev);
734 origin_dev_size = get_dev_size(s->origin->bdev);
735 max_buckets = calc_max_buckets();
737 hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
738 hash_size = min(hash_size, max_buckets);
740 if (hash_size < 64)
741 hash_size = 64;
742 hash_size = rounddown_pow_of_two(hash_size);
743 if (dm_exception_table_init(&s->complete, hash_size,
744 DM_CHUNK_CONSECUTIVE_BITS))
745 return -ENOMEM;
748 * Allocate hash table for in-flight exceptions
749 * Make this smaller than the real hash table
751 hash_size >>= 3;
752 if (hash_size < 64)
753 hash_size = 64;
755 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
756 dm_exception_table_exit(&s->complete, exception_cache);
757 return -ENOMEM;
760 return 0;
763 static void merge_shutdown(struct dm_snapshot *s)
765 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
766 smp_mb__after_clear_bit();
767 wake_up_bit(&s->state_bits, RUNNING_MERGE);
770 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
772 s->first_merging_chunk = 0;
773 s->num_merging_chunks = 0;
775 return bio_list_get(&s->bios_queued_during_merge);
779 * Remove one chunk from the index of completed exceptions.
781 static int __remove_single_exception_chunk(struct dm_snapshot *s,
782 chunk_t old_chunk)
784 struct dm_exception *e;
786 e = dm_lookup_exception(&s->complete, old_chunk);
787 if (!e) {
788 DMERR("Corruption detected: exception for block %llu is "
789 "on disk but not in memory",
790 (unsigned long long)old_chunk);
791 return -EINVAL;
795 * If this is the only chunk using this exception, remove exception.
797 if (!dm_consecutive_chunk_count(e)) {
798 dm_remove_exception(e);
799 free_completed_exception(e);
800 return 0;
804 * The chunk may be either at the beginning or the end of a
805 * group of consecutive chunks - never in the middle. We are
806 * removing chunks in the opposite order to that in which they
807 * were added, so this should always be true.
808 * Decrement the consecutive chunk counter and adjust the
809 * starting point if necessary.
811 if (old_chunk == e->old_chunk) {
812 e->old_chunk++;
813 e->new_chunk++;
814 } else if (old_chunk != e->old_chunk +
815 dm_consecutive_chunk_count(e)) {
816 DMERR("Attempt to merge block %llu from the "
817 "middle of a chunk range [%llu - %llu]",
818 (unsigned long long)old_chunk,
819 (unsigned long long)e->old_chunk,
820 (unsigned long long)
821 e->old_chunk + dm_consecutive_chunk_count(e));
822 return -EINVAL;
825 dm_consecutive_chunk_count_dec(e);
827 return 0;
830 static void flush_bios(struct bio *bio);
832 static int remove_single_exception_chunk(struct dm_snapshot *s)
834 struct bio *b = NULL;
835 int r;
836 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
838 down_write(&s->lock);
841 * Process chunks (and associated exceptions) in reverse order
842 * so that dm_consecutive_chunk_count_dec() accounting works.
844 do {
845 r = __remove_single_exception_chunk(s, old_chunk);
846 if (r)
847 goto out;
848 } while (old_chunk-- > s->first_merging_chunk);
850 b = __release_queued_bios_after_merge(s);
852 out:
853 up_write(&s->lock);
854 if (b)
855 flush_bios(b);
857 return r;
860 static int origin_write_extent(struct dm_snapshot *merging_snap,
861 sector_t sector, unsigned chunk_size);
863 static void merge_callback(int read_err, unsigned long write_err,
864 void *context);
866 static uint64_t read_pending_exceptions_done_count(void)
868 uint64_t pending_exceptions_done;
870 spin_lock(&_pending_exceptions_done_spinlock);
871 pending_exceptions_done = _pending_exceptions_done_count;
872 spin_unlock(&_pending_exceptions_done_spinlock);
874 return pending_exceptions_done;
877 static void increment_pending_exceptions_done_count(void)
879 spin_lock(&_pending_exceptions_done_spinlock);
880 _pending_exceptions_done_count++;
881 spin_unlock(&_pending_exceptions_done_spinlock);
883 wake_up_all(&_pending_exceptions_done);
886 static void snapshot_merge_next_chunks(struct dm_snapshot *s)
888 int i, linear_chunks;
889 chunk_t old_chunk, new_chunk;
890 struct dm_io_region src, dest;
891 sector_t io_size;
892 uint64_t previous_count;
894 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
895 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
896 goto shut;
899 * valid flag never changes during merge, so no lock required.
901 if (!s->valid) {
902 DMERR("Snapshot is invalid: can't merge");
903 goto shut;
906 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
907 &new_chunk);
908 if (linear_chunks <= 0) {
909 if (linear_chunks < 0) {
910 DMERR("Read error in exception store: "
911 "shutting down merge");
912 down_write(&s->lock);
913 s->merge_failed = 1;
914 up_write(&s->lock);
916 goto shut;
919 /* Adjust old_chunk and new_chunk to reflect start of linear region */
920 old_chunk = old_chunk + 1 - linear_chunks;
921 new_chunk = new_chunk + 1 - linear_chunks;
924 * Use one (potentially large) I/O to copy all 'linear_chunks'
925 * from the exception store to the origin
927 io_size = linear_chunks * s->store->chunk_size;
929 dest.bdev = s->origin->bdev;
930 dest.sector = chunk_to_sector(s->store, old_chunk);
931 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
933 src.bdev = s->cow->bdev;
934 src.sector = chunk_to_sector(s->store, new_chunk);
935 src.count = dest.count;
938 * Reallocate any exceptions needed in other snapshots then
939 * wait for the pending exceptions to complete.
940 * Each time any pending exception (globally on the system)
941 * completes we are woken and repeat the process to find out
942 * if we can proceed. While this may not seem a particularly
943 * efficient algorithm, it is not expected to have any
944 * significant impact on performance.
946 previous_count = read_pending_exceptions_done_count();
947 while (origin_write_extent(s, dest.sector, io_size)) {
948 wait_event(_pending_exceptions_done,
949 (read_pending_exceptions_done_count() !=
950 previous_count));
951 /* Retry after the wait, until all exceptions are done. */
952 previous_count = read_pending_exceptions_done_count();
955 down_write(&s->lock);
956 s->first_merging_chunk = old_chunk;
957 s->num_merging_chunks = linear_chunks;
958 up_write(&s->lock);
960 /* Wait until writes to all 'linear_chunks' drain */
961 for (i = 0; i < linear_chunks; i++)
962 __check_for_conflicting_io(s, old_chunk + i);
964 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
965 return;
967 shut:
968 merge_shutdown(s);
971 static void error_bios(struct bio *bio);
973 static void merge_callback(int read_err, unsigned long write_err, void *context)
975 struct dm_snapshot *s = context;
976 struct bio *b = NULL;
978 if (read_err || write_err) {
979 if (read_err)
980 DMERR("Read error: shutting down merge.");
981 else
982 DMERR("Write error: shutting down merge.");
983 goto shut;
986 if (s->store->type->commit_merge(s->store,
987 s->num_merging_chunks) < 0) {
988 DMERR("Write error in exception store: shutting down merge");
989 goto shut;
992 if (remove_single_exception_chunk(s) < 0)
993 goto shut;
995 snapshot_merge_next_chunks(s);
997 return;
999 shut:
1000 down_write(&s->lock);
1001 s->merge_failed = 1;
1002 b = __release_queued_bios_after_merge(s);
1003 up_write(&s->lock);
1004 error_bios(b);
1006 merge_shutdown(s);
1009 static void start_merge(struct dm_snapshot *s)
1011 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1012 snapshot_merge_next_chunks(s);
1015 static int wait_schedule(void *ptr)
1017 schedule();
1019 return 0;
1023 * Stop the merging process and wait until it finishes.
1025 static void stop_merge(struct dm_snapshot *s)
1027 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1028 wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule,
1029 TASK_UNINTERRUPTIBLE);
1030 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1034 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
1036 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1038 struct dm_snapshot *s;
1039 int i;
1040 int r = -EINVAL;
1041 char *origin_path, *cow_path;
1042 unsigned args_used, num_flush_requests = 1;
1043 fmode_t origin_mode = FMODE_READ;
1045 if (argc != 4) {
1046 ti->error = "requires exactly 4 arguments";
1047 r = -EINVAL;
1048 goto bad;
1051 if (dm_target_is_snapshot_merge(ti)) {
1052 num_flush_requests = 2;
1053 origin_mode = FMODE_WRITE;
1056 s = kmalloc(sizeof(*s), GFP_KERNEL);
1057 if (!s) {
1058 ti->error = "Cannot allocate snapshot context private "
1059 "structure";
1060 r = -ENOMEM;
1061 goto bad;
1064 origin_path = argv[0];
1065 argv++;
1066 argc--;
1068 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1069 if (r) {
1070 ti->error = "Cannot get origin device";
1071 goto bad_origin;
1074 cow_path = argv[0];
1075 argv++;
1076 argc--;
1078 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1079 if (r) {
1080 ti->error = "Cannot get COW device";
1081 goto bad_cow;
1084 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1085 if (r) {
1086 ti->error = "Couldn't create exception store";
1087 r = -EINVAL;
1088 goto bad_store;
1091 argv += args_used;
1092 argc -= args_used;
1094 s->ti = ti;
1095 s->valid = 1;
1096 s->active = 0;
1097 atomic_set(&s->pending_exceptions_count, 0);
1098 init_rwsem(&s->lock);
1099 INIT_LIST_HEAD(&s->list);
1100 spin_lock_init(&s->pe_lock);
1101 s->state_bits = 0;
1102 s->merge_failed = 0;
1103 s->first_merging_chunk = 0;
1104 s->num_merging_chunks = 0;
1105 bio_list_init(&s->bios_queued_during_merge);
1107 /* Allocate hash table for COW data */
1108 if (init_hash_tables(s)) {
1109 ti->error = "Unable to allocate hash table space";
1110 r = -ENOMEM;
1111 goto bad_hash_tables;
1114 s->kcopyd_client = dm_kcopyd_client_create();
1115 if (IS_ERR(s->kcopyd_client)) {
1116 r = PTR_ERR(s->kcopyd_client);
1117 ti->error = "Could not create kcopyd client";
1118 goto bad_kcopyd;
1121 s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1122 if (!s->pending_pool) {
1123 ti->error = "Could not allocate mempool for pending exceptions";
1124 goto bad_pending_pool;
1127 s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
1128 tracked_chunk_cache);
1129 if (!s->tracked_chunk_pool) {
1130 ti->error = "Could not allocate tracked_chunk mempool for "
1131 "tracking reads";
1132 goto bad_tracked_chunk_pool;
1135 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1136 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1138 spin_lock_init(&s->tracked_chunk_lock);
1140 ti->private = s;
1141 ti->num_flush_requests = num_flush_requests;
1143 /* Add snapshot to the list of snapshots for this origin */
1144 /* Exceptions aren't triggered till snapshot_resume() is called */
1145 r = register_snapshot(s);
1146 if (r == -ENOMEM) {
1147 ti->error = "Snapshot origin struct allocation failed";
1148 goto bad_load_and_register;
1149 } else if (r < 0) {
1150 /* invalid handover, register_snapshot has set ti->error */
1151 goto bad_load_and_register;
1155 * Metadata must only be loaded into one table at once, so skip this
1156 * if metadata will be handed over during resume.
1157 * Chunk size will be set during the handover - set it to zero to
1158 * ensure it's ignored.
1160 if (r > 0) {
1161 s->store->chunk_size = 0;
1162 return 0;
1165 r = s->store->type->read_metadata(s->store, dm_add_exception,
1166 (void *)s);
1167 if (r < 0) {
1168 ti->error = "Failed to read snapshot metadata";
1169 goto bad_read_metadata;
1170 } else if (r > 0) {
1171 s->valid = 0;
1172 DMWARN("Snapshot is marked invalid.");
1175 if (!s->store->chunk_size) {
1176 ti->error = "Chunk size not set";
1177 goto bad_read_metadata;
1179 ti->split_io = s->store->chunk_size;
1181 return 0;
1183 bad_read_metadata:
1184 unregister_snapshot(s);
1186 bad_load_and_register:
1187 mempool_destroy(s->tracked_chunk_pool);
1189 bad_tracked_chunk_pool:
1190 mempool_destroy(s->pending_pool);
1192 bad_pending_pool:
1193 dm_kcopyd_client_destroy(s->kcopyd_client);
1195 bad_kcopyd:
1196 dm_exception_table_exit(&s->pending, pending_cache);
1197 dm_exception_table_exit(&s->complete, exception_cache);
1199 bad_hash_tables:
1200 dm_exception_store_destroy(s->store);
1202 bad_store:
1203 dm_put_device(ti, s->cow);
1205 bad_cow:
1206 dm_put_device(ti, s->origin);
1208 bad_origin:
1209 kfree(s);
1211 bad:
1212 return r;
1215 static void __free_exceptions(struct dm_snapshot *s)
1217 dm_kcopyd_client_destroy(s->kcopyd_client);
1218 s->kcopyd_client = NULL;
1220 dm_exception_table_exit(&s->pending, pending_cache);
1221 dm_exception_table_exit(&s->complete, exception_cache);
1224 static void __handover_exceptions(struct dm_snapshot *snap_src,
1225 struct dm_snapshot *snap_dest)
1227 union {
1228 struct dm_exception_table table_swap;
1229 struct dm_exception_store *store_swap;
1230 } u;
1233 * Swap all snapshot context information between the two instances.
1235 u.table_swap = snap_dest->complete;
1236 snap_dest->complete = snap_src->complete;
1237 snap_src->complete = u.table_swap;
1239 u.store_swap = snap_dest->store;
1240 snap_dest->store = snap_src->store;
1241 snap_src->store = u.store_swap;
1243 snap_dest->store->snap = snap_dest;
1244 snap_src->store->snap = snap_src;
1246 snap_dest->ti->split_io = snap_dest->store->chunk_size;
1247 snap_dest->valid = snap_src->valid;
1250 * Set source invalid to ensure it receives no further I/O.
1252 snap_src->valid = 0;
1255 static void snapshot_dtr(struct dm_target *ti)
1257 #ifdef CONFIG_DM_DEBUG
1258 int i;
1259 #endif
1260 struct dm_snapshot *s = ti->private;
1261 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1263 down_read(&_origins_lock);
1264 /* Check whether exception handover must be cancelled */
1265 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1266 if (snap_src && snap_dest && (s == snap_src)) {
1267 down_write(&snap_dest->lock);
1268 snap_dest->valid = 0;
1269 up_write(&snap_dest->lock);
1270 DMERR("Cancelling snapshot handover.");
1272 up_read(&_origins_lock);
1274 if (dm_target_is_snapshot_merge(ti))
1275 stop_merge(s);
1277 /* Prevent further origin writes from using this snapshot. */
1278 /* After this returns there can be no new kcopyd jobs. */
1279 unregister_snapshot(s);
1281 while (atomic_read(&s->pending_exceptions_count))
1282 msleep(1);
1284 * Ensure instructions in mempool_destroy aren't reordered
1285 * before atomic_read.
1287 smp_mb();
1289 #ifdef CONFIG_DM_DEBUG
1290 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1291 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1292 #endif
1294 mempool_destroy(s->tracked_chunk_pool);
1296 __free_exceptions(s);
1298 mempool_destroy(s->pending_pool);
1300 dm_exception_store_destroy(s->store);
1302 dm_put_device(ti, s->cow);
1304 dm_put_device(ti, s->origin);
1306 kfree(s);
1310 * Flush a list of buffers.
1312 static void flush_bios(struct bio *bio)
1314 struct bio *n;
1316 while (bio) {
1317 n = bio->bi_next;
1318 bio->bi_next = NULL;
1319 generic_make_request(bio);
1320 bio = n;
1324 static int do_origin(struct dm_dev *origin, struct bio *bio);
1327 * Flush a list of buffers.
1329 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1331 struct bio *n;
1332 int r;
1334 while (bio) {
1335 n = bio->bi_next;
1336 bio->bi_next = NULL;
1337 r = do_origin(s->origin, bio);
1338 if (r == DM_MAPIO_REMAPPED)
1339 generic_make_request(bio);
1340 bio = n;
1345 * Error a list of buffers.
1347 static void error_bios(struct bio *bio)
1349 struct bio *n;
1351 while (bio) {
1352 n = bio->bi_next;
1353 bio->bi_next = NULL;
1354 bio_io_error(bio);
1355 bio = n;
1359 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1361 if (!s->valid)
1362 return;
1364 if (err == -EIO)
1365 DMERR("Invalidating snapshot: Error reading/writing.");
1366 else if (err == -ENOMEM)
1367 DMERR("Invalidating snapshot: Unable to allocate exception.");
1369 if (s->store->type->drop_snapshot)
1370 s->store->type->drop_snapshot(s->store);
1372 s->valid = 0;
1374 dm_table_event(s->ti->table);
1377 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
1379 struct dm_exception *e;
1380 struct dm_snapshot *s = pe->snap;
1381 struct bio *origin_bios = NULL;
1382 struct bio *snapshot_bios = NULL;
1383 int error = 0;
1385 if (!success) {
1386 /* Read/write error - snapshot is unusable */
1387 down_write(&s->lock);
1388 __invalidate_snapshot(s, -EIO);
1389 error = 1;
1390 goto out;
1393 e = alloc_completed_exception();
1394 if (!e) {
1395 down_write(&s->lock);
1396 __invalidate_snapshot(s, -ENOMEM);
1397 error = 1;
1398 goto out;
1400 *e = pe->e;
1402 down_write(&s->lock);
1403 if (!s->valid) {
1404 free_completed_exception(e);
1405 error = 1;
1406 goto out;
1409 /* Check for conflicting reads */
1410 __check_for_conflicting_io(s, pe->e.old_chunk);
1413 * Add a proper exception, and remove the
1414 * in-flight exception from the list.
1416 dm_insert_exception(&s->complete, e);
1418 out:
1419 dm_remove_exception(&pe->e);
1420 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1421 origin_bios = bio_list_get(&pe->origin_bios);
1422 free_pending_exception(pe);
1424 increment_pending_exceptions_done_count();
1426 up_write(&s->lock);
1428 /* Submit any pending write bios */
1429 if (error)
1430 error_bios(snapshot_bios);
1431 else
1432 flush_bios(snapshot_bios);
1434 retry_origin_bios(s, origin_bios);
1437 static void commit_callback(void *context, int success)
1439 struct dm_snap_pending_exception *pe = context;
1441 pending_complete(pe, success);
1445 * Called when the copy I/O has finished. kcopyd actually runs
1446 * this code so don't block.
1448 static void copy_callback(int read_err, unsigned long write_err, void *context)
1450 struct dm_snap_pending_exception *pe = context;
1451 struct dm_snapshot *s = pe->snap;
1453 if (read_err || write_err)
1454 pending_complete(pe, 0);
1456 else
1457 /* Update the metadata if we are persistent */
1458 s->store->type->commit_exception(s->store, &pe->e,
1459 commit_callback, pe);
1463 * Dispatches the copy operation to kcopyd.
1465 static void start_copy(struct dm_snap_pending_exception *pe)
1467 struct dm_snapshot *s = pe->snap;
1468 struct dm_io_region src, dest;
1469 struct block_device *bdev = s->origin->bdev;
1470 sector_t dev_size;
1472 dev_size = get_dev_size(bdev);
1474 src.bdev = bdev;
1475 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1476 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1478 dest.bdev = s->cow->bdev;
1479 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1480 dest.count = src.count;
1482 /* Hand over to kcopyd */
1483 dm_kcopyd_copy(s->kcopyd_client,
1484 &src, 1, &dest, 0, copy_callback, pe);
1487 static struct dm_snap_pending_exception *
1488 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1490 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1492 if (!e)
1493 return NULL;
1495 return container_of(e, struct dm_snap_pending_exception, e);
1499 * Looks to see if this snapshot already has a pending exception
1500 * for this chunk, otherwise it allocates a new one and inserts
1501 * it into the pending table.
1503 * NOTE: a write lock must be held on snap->lock before calling
1504 * this.
1506 static struct dm_snap_pending_exception *
1507 __find_pending_exception(struct dm_snapshot *s,
1508 struct dm_snap_pending_exception *pe, chunk_t chunk)
1510 struct dm_snap_pending_exception *pe2;
1512 pe2 = __lookup_pending_exception(s, chunk);
1513 if (pe2) {
1514 free_pending_exception(pe);
1515 return pe2;
1518 pe->e.old_chunk = chunk;
1519 bio_list_init(&pe->origin_bios);
1520 bio_list_init(&pe->snapshot_bios);
1521 pe->started = 0;
1523 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1524 free_pending_exception(pe);
1525 return NULL;
1528 dm_insert_exception(&s->pending, &pe->e);
1530 return pe;
1533 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1534 struct bio *bio, chunk_t chunk)
1536 bio->bi_bdev = s->cow->bdev;
1537 bio->bi_sector = chunk_to_sector(s->store,
1538 dm_chunk_number(e->new_chunk) +
1539 (chunk - e->old_chunk)) +
1540 (bio->bi_sector &
1541 s->store->chunk_mask);
1544 static int snapshot_map(struct dm_target *ti, struct bio *bio,
1545 union map_info *map_context)
1547 struct dm_exception *e;
1548 struct dm_snapshot *s = ti->private;
1549 int r = DM_MAPIO_REMAPPED;
1550 chunk_t chunk;
1551 struct dm_snap_pending_exception *pe = NULL;
1553 if (bio->bi_rw & REQ_FLUSH) {
1554 bio->bi_bdev = s->cow->bdev;
1555 return DM_MAPIO_REMAPPED;
1558 chunk = sector_to_chunk(s->store, bio->bi_sector);
1560 /* Full snapshots are not usable */
1561 /* To get here the table must be live so s->active is always set. */
1562 if (!s->valid)
1563 return -EIO;
1565 /* FIXME: should only take write lock if we need
1566 * to copy an exception */
1567 down_write(&s->lock);
1569 if (!s->valid) {
1570 r = -EIO;
1571 goto out_unlock;
1574 /* If the block is already remapped - use that, else remap it */
1575 e = dm_lookup_exception(&s->complete, chunk);
1576 if (e) {
1577 remap_exception(s, e, bio, chunk);
1578 goto out_unlock;
1582 * Write to snapshot - higher level takes care of RW/RO
1583 * flags so we should only get this if we are
1584 * writeable.
1586 if (bio_rw(bio) == WRITE) {
1587 pe = __lookup_pending_exception(s, chunk);
1588 if (!pe) {
1589 up_write(&s->lock);
1590 pe = alloc_pending_exception(s);
1591 down_write(&s->lock);
1593 if (!s->valid) {
1594 free_pending_exception(pe);
1595 r = -EIO;
1596 goto out_unlock;
1599 e = dm_lookup_exception(&s->complete, chunk);
1600 if (e) {
1601 free_pending_exception(pe);
1602 remap_exception(s, e, bio, chunk);
1603 goto out_unlock;
1606 pe = __find_pending_exception(s, pe, chunk);
1607 if (!pe) {
1608 __invalidate_snapshot(s, -ENOMEM);
1609 r = -EIO;
1610 goto out_unlock;
1614 remap_exception(s, &pe->e, bio, chunk);
1615 bio_list_add(&pe->snapshot_bios, bio);
1617 r = DM_MAPIO_SUBMITTED;
1619 if (!pe->started) {
1620 /* this is protected by snap->lock */
1621 pe->started = 1;
1622 up_write(&s->lock);
1623 start_copy(pe);
1624 goto out;
1626 } else {
1627 bio->bi_bdev = s->origin->bdev;
1628 map_context->ptr = track_chunk(s, chunk);
1631 out_unlock:
1632 up_write(&s->lock);
1633 out:
1634 return r;
1638 * A snapshot-merge target behaves like a combination of a snapshot
1639 * target and a snapshot-origin target. It only generates new
1640 * exceptions in other snapshots and not in the one that is being
1641 * merged.
1643 * For each chunk, if there is an existing exception, it is used to
1644 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
1645 * which in turn might generate exceptions in other snapshots.
1646 * If merging is currently taking place on the chunk in question, the
1647 * I/O is deferred by adding it to s->bios_queued_during_merge.
1649 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
1650 union map_info *map_context)
1652 struct dm_exception *e;
1653 struct dm_snapshot *s = ti->private;
1654 int r = DM_MAPIO_REMAPPED;
1655 chunk_t chunk;
1657 if (bio->bi_rw & REQ_FLUSH) {
1658 if (!map_context->target_request_nr)
1659 bio->bi_bdev = s->origin->bdev;
1660 else
1661 bio->bi_bdev = s->cow->bdev;
1662 map_context->ptr = NULL;
1663 return DM_MAPIO_REMAPPED;
1666 chunk = sector_to_chunk(s->store, bio->bi_sector);
1668 down_write(&s->lock);
1670 /* Full merging snapshots are redirected to the origin */
1671 if (!s->valid)
1672 goto redirect_to_origin;
1674 /* If the block is already remapped - use that */
1675 e = dm_lookup_exception(&s->complete, chunk);
1676 if (e) {
1677 /* Queue writes overlapping with chunks being merged */
1678 if (bio_rw(bio) == WRITE &&
1679 chunk >= s->first_merging_chunk &&
1680 chunk < (s->first_merging_chunk +
1681 s->num_merging_chunks)) {
1682 bio->bi_bdev = s->origin->bdev;
1683 bio_list_add(&s->bios_queued_during_merge, bio);
1684 r = DM_MAPIO_SUBMITTED;
1685 goto out_unlock;
1688 remap_exception(s, e, bio, chunk);
1690 if (bio_rw(bio) == WRITE)
1691 map_context->ptr = track_chunk(s, chunk);
1692 goto out_unlock;
1695 redirect_to_origin:
1696 bio->bi_bdev = s->origin->bdev;
1698 if (bio_rw(bio) == WRITE) {
1699 up_write(&s->lock);
1700 return do_origin(s->origin, bio);
1703 out_unlock:
1704 up_write(&s->lock);
1706 return r;
1709 static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
1710 int error, union map_info *map_context)
1712 struct dm_snapshot *s = ti->private;
1713 struct dm_snap_tracked_chunk *c = map_context->ptr;
1715 if (c)
1716 stop_tracking_chunk(s, c);
1718 return 0;
1721 static void snapshot_merge_presuspend(struct dm_target *ti)
1723 struct dm_snapshot *s = ti->private;
1725 stop_merge(s);
1728 static int snapshot_preresume(struct dm_target *ti)
1730 int r = 0;
1731 struct dm_snapshot *s = ti->private;
1732 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1734 down_read(&_origins_lock);
1735 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1736 if (snap_src && snap_dest) {
1737 down_read(&snap_src->lock);
1738 if (s == snap_src) {
1739 DMERR("Unable to resume snapshot source until "
1740 "handover completes.");
1741 r = -EINVAL;
1742 } else if (!dm_suspended(snap_src->ti)) {
1743 DMERR("Unable to perform snapshot handover until "
1744 "source is suspended.");
1745 r = -EINVAL;
1747 up_read(&snap_src->lock);
1749 up_read(&_origins_lock);
1751 return r;
1754 static void snapshot_resume(struct dm_target *ti)
1756 struct dm_snapshot *s = ti->private;
1757 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1759 down_read(&_origins_lock);
1760 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1761 if (snap_src && snap_dest) {
1762 down_write(&snap_src->lock);
1763 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1764 __handover_exceptions(snap_src, snap_dest);
1765 up_write(&snap_dest->lock);
1766 up_write(&snap_src->lock);
1768 up_read(&_origins_lock);
1770 /* Now we have correct chunk size, reregister */
1771 reregister_snapshot(s);
1773 down_write(&s->lock);
1774 s->active = 1;
1775 up_write(&s->lock);
1778 static sector_t get_origin_minimum_chunksize(struct block_device *bdev)
1780 sector_t min_chunksize;
1782 down_read(&_origins_lock);
1783 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1784 up_read(&_origins_lock);
1786 return min_chunksize;
1789 static void snapshot_merge_resume(struct dm_target *ti)
1791 struct dm_snapshot *s = ti->private;
1794 * Handover exceptions from existing snapshot.
1796 snapshot_resume(ti);
1799 * snapshot-merge acts as an origin, so set ti->split_io
1801 ti->split_io = get_origin_minimum_chunksize(s->origin->bdev);
1803 start_merge(s);
1806 static int snapshot_status(struct dm_target *ti, status_type_t type,
1807 char *result, unsigned int maxlen)
1809 unsigned sz = 0;
1810 struct dm_snapshot *snap = ti->private;
1812 switch (type) {
1813 case STATUSTYPE_INFO:
1815 down_write(&snap->lock);
1817 if (!snap->valid)
1818 DMEMIT("Invalid");
1819 else if (snap->merge_failed)
1820 DMEMIT("Merge failed");
1821 else {
1822 if (snap->store->type->usage) {
1823 sector_t total_sectors, sectors_allocated,
1824 metadata_sectors;
1825 snap->store->type->usage(snap->store,
1826 &total_sectors,
1827 &sectors_allocated,
1828 &metadata_sectors);
1829 DMEMIT("%llu/%llu %llu",
1830 (unsigned long long)sectors_allocated,
1831 (unsigned long long)total_sectors,
1832 (unsigned long long)metadata_sectors);
1834 else
1835 DMEMIT("Unknown");
1838 up_write(&snap->lock);
1840 break;
1842 case STATUSTYPE_TABLE:
1844 * kdevname returns a static pointer so we need
1845 * to make private copies if the output is to
1846 * make sense.
1848 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1849 snap->store->type->status(snap->store, type, result + sz,
1850 maxlen - sz);
1851 break;
1854 return 0;
1857 static int snapshot_iterate_devices(struct dm_target *ti,
1858 iterate_devices_callout_fn fn, void *data)
1860 struct dm_snapshot *snap = ti->private;
1861 int r;
1863 r = fn(ti, snap->origin, 0, ti->len, data);
1865 if (!r)
1866 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
1868 return r;
1872 /*-----------------------------------------------------------------
1873 * Origin methods
1874 *---------------------------------------------------------------*/
1877 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
1878 * supplied bio was ignored. The caller may submit it immediately.
1879 * (No remapping actually occurs as the origin is always a direct linear
1880 * map.)
1882 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
1883 * and any supplied bio is added to a list to be submitted once all
1884 * the necessary exceptions exist.
1886 static int __origin_write(struct list_head *snapshots, sector_t sector,
1887 struct bio *bio)
1889 int r = DM_MAPIO_REMAPPED;
1890 struct dm_snapshot *snap;
1891 struct dm_exception *e;
1892 struct dm_snap_pending_exception *pe;
1893 struct dm_snap_pending_exception *pe_to_start_now = NULL;
1894 struct dm_snap_pending_exception *pe_to_start_last = NULL;
1895 chunk_t chunk;
1897 /* Do all the snapshots on this origin */
1898 list_for_each_entry (snap, snapshots, list) {
1900 * Don't make new exceptions in a merging snapshot
1901 * because it has effectively been deleted
1903 if (dm_target_is_snapshot_merge(snap->ti))
1904 continue;
1906 down_write(&snap->lock);
1908 /* Only deal with valid and active snapshots */
1909 if (!snap->valid || !snap->active)
1910 goto next_snapshot;
1912 /* Nothing to do if writing beyond end of snapshot */
1913 if (sector >= dm_table_get_size(snap->ti->table))
1914 goto next_snapshot;
1917 * Remember, different snapshots can have
1918 * different chunk sizes.
1920 chunk = sector_to_chunk(snap->store, sector);
1923 * Check exception table to see if block
1924 * is already remapped in this snapshot
1925 * and trigger an exception if not.
1927 e = dm_lookup_exception(&snap->complete, chunk);
1928 if (e)
1929 goto next_snapshot;
1931 pe = __lookup_pending_exception(snap, chunk);
1932 if (!pe) {
1933 up_write(&snap->lock);
1934 pe = alloc_pending_exception(snap);
1935 down_write(&snap->lock);
1937 if (!snap->valid) {
1938 free_pending_exception(pe);
1939 goto next_snapshot;
1942 e = dm_lookup_exception(&snap->complete, chunk);
1943 if (e) {
1944 free_pending_exception(pe);
1945 goto next_snapshot;
1948 pe = __find_pending_exception(snap, pe, chunk);
1949 if (!pe) {
1950 __invalidate_snapshot(snap, -ENOMEM);
1951 goto next_snapshot;
1955 r = DM_MAPIO_SUBMITTED;
1958 * If an origin bio was supplied, queue it to wait for the
1959 * completion of this exception, and start this one last,
1960 * at the end of the function.
1962 if (bio) {
1963 bio_list_add(&pe->origin_bios, bio);
1964 bio = NULL;
1966 if (!pe->started) {
1967 pe->started = 1;
1968 pe_to_start_last = pe;
1972 if (!pe->started) {
1973 pe->started = 1;
1974 pe_to_start_now = pe;
1977 next_snapshot:
1978 up_write(&snap->lock);
1980 if (pe_to_start_now) {
1981 start_copy(pe_to_start_now);
1982 pe_to_start_now = NULL;
1987 * Submit the exception against which the bio is queued last,
1988 * to give the other exceptions a head start.
1990 if (pe_to_start_last)
1991 start_copy(pe_to_start_last);
1993 return r;
1997 * Called on a write from the origin driver.
1999 static int do_origin(struct dm_dev *origin, struct bio *bio)
2001 struct origin *o;
2002 int r = DM_MAPIO_REMAPPED;
2004 down_read(&_origins_lock);
2005 o = __lookup_origin(origin->bdev);
2006 if (o)
2007 r = __origin_write(&o->snapshots, bio->bi_sector, bio);
2008 up_read(&_origins_lock);
2010 return r;
2014 * Trigger exceptions in all non-merging snapshots.
2016 * The chunk size of the merging snapshot may be larger than the chunk
2017 * size of some other snapshot so we may need to reallocate multiple
2018 * chunks in other snapshots.
2020 * We scan all the overlapping exceptions in the other snapshots.
2021 * Returns 1 if anything was reallocated and must be waited for,
2022 * otherwise returns 0.
2024 * size must be a multiple of merging_snap's chunk_size.
2026 static int origin_write_extent(struct dm_snapshot *merging_snap,
2027 sector_t sector, unsigned size)
2029 int must_wait = 0;
2030 sector_t n;
2031 struct origin *o;
2034 * The origin's __minimum_chunk_size() got stored in split_io
2035 * by snapshot_merge_resume().
2037 down_read(&_origins_lock);
2038 o = __lookup_origin(merging_snap->origin->bdev);
2039 for (n = 0; n < size; n += merging_snap->ti->split_io)
2040 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2041 DM_MAPIO_SUBMITTED)
2042 must_wait = 1;
2043 up_read(&_origins_lock);
2045 return must_wait;
2049 * Origin: maps a linear range of a device, with hooks for snapshotting.
2053 * Construct an origin mapping: <dev_path>
2054 * The context for an origin is merely a 'struct dm_dev *'
2055 * pointing to the real device.
2057 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2059 int r;
2060 struct dm_dev *dev;
2062 if (argc != 1) {
2063 ti->error = "origin: incorrect number of arguments";
2064 return -EINVAL;
2067 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev);
2068 if (r) {
2069 ti->error = "Cannot get target device";
2070 return r;
2073 ti->private = dev;
2074 ti->num_flush_requests = 1;
2076 return 0;
2079 static void origin_dtr(struct dm_target *ti)
2081 struct dm_dev *dev = ti->private;
2082 dm_put_device(ti, dev);
2085 static int origin_map(struct dm_target *ti, struct bio *bio,
2086 union map_info *map_context)
2088 struct dm_dev *dev = ti->private;
2089 bio->bi_bdev = dev->bdev;
2091 if (bio->bi_rw & REQ_FLUSH)
2092 return DM_MAPIO_REMAPPED;
2094 /* Only tell snapshots if this is a write */
2095 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
2099 * Set the target "split_io" field to the minimum of all the snapshots'
2100 * chunk sizes.
2102 static void origin_resume(struct dm_target *ti)
2104 struct dm_dev *dev = ti->private;
2106 ti->split_io = get_origin_minimum_chunksize(dev->bdev);
2109 static int origin_status(struct dm_target *ti, status_type_t type, char *result,
2110 unsigned int maxlen)
2112 struct dm_dev *dev = ti->private;
2114 switch (type) {
2115 case STATUSTYPE_INFO:
2116 result[0] = '\0';
2117 break;
2119 case STATUSTYPE_TABLE:
2120 snprintf(result, maxlen, "%s", dev->name);
2121 break;
2124 return 0;
2127 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
2128 struct bio_vec *biovec, int max_size)
2130 struct dm_dev *dev = ti->private;
2131 struct request_queue *q = bdev_get_queue(dev->bdev);
2133 if (!q->merge_bvec_fn)
2134 return max_size;
2136 bvm->bi_bdev = dev->bdev;
2137 bvm->bi_sector = bvm->bi_sector;
2139 return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2142 static int origin_iterate_devices(struct dm_target *ti,
2143 iterate_devices_callout_fn fn, void *data)
2145 struct dm_dev *dev = ti->private;
2147 return fn(ti, dev, 0, ti->len, data);
2150 static struct target_type origin_target = {
2151 .name = "snapshot-origin",
2152 .version = {1, 7, 1},
2153 .module = THIS_MODULE,
2154 .ctr = origin_ctr,
2155 .dtr = origin_dtr,
2156 .map = origin_map,
2157 .resume = origin_resume,
2158 .status = origin_status,
2159 .merge = origin_merge,
2160 .iterate_devices = origin_iterate_devices,
2163 static struct target_type snapshot_target = {
2164 .name = "snapshot",
2165 .version = {1, 10, 0},
2166 .module = THIS_MODULE,
2167 .ctr = snapshot_ctr,
2168 .dtr = snapshot_dtr,
2169 .map = snapshot_map,
2170 .end_io = snapshot_end_io,
2171 .preresume = snapshot_preresume,
2172 .resume = snapshot_resume,
2173 .status = snapshot_status,
2174 .iterate_devices = snapshot_iterate_devices,
2177 static struct target_type merge_target = {
2178 .name = dm_snapshot_merge_target_name,
2179 .version = {1, 1, 0},
2180 .module = THIS_MODULE,
2181 .ctr = snapshot_ctr,
2182 .dtr = snapshot_dtr,
2183 .map = snapshot_merge_map,
2184 .end_io = snapshot_end_io,
2185 .presuspend = snapshot_merge_presuspend,
2186 .preresume = snapshot_preresume,
2187 .resume = snapshot_merge_resume,
2188 .status = snapshot_status,
2189 .iterate_devices = snapshot_iterate_devices,
2192 static int __init dm_snapshot_init(void)
2194 int r;
2196 r = dm_exception_store_init();
2197 if (r) {
2198 DMERR("Failed to initialize exception stores");
2199 return r;
2202 r = dm_register_target(&snapshot_target);
2203 if (r < 0) {
2204 DMERR("snapshot target register failed %d", r);
2205 goto bad_register_snapshot_target;
2208 r = dm_register_target(&origin_target);
2209 if (r < 0) {
2210 DMERR("Origin target register failed %d", r);
2211 goto bad_register_origin_target;
2214 r = dm_register_target(&merge_target);
2215 if (r < 0) {
2216 DMERR("Merge target register failed %d", r);
2217 goto bad_register_merge_target;
2220 r = init_origin_hash();
2221 if (r) {
2222 DMERR("init_origin_hash failed.");
2223 goto bad_origin_hash;
2226 exception_cache = KMEM_CACHE(dm_exception, 0);
2227 if (!exception_cache) {
2228 DMERR("Couldn't create exception cache.");
2229 r = -ENOMEM;
2230 goto bad_exception_cache;
2233 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2234 if (!pending_cache) {
2235 DMERR("Couldn't create pending cache.");
2236 r = -ENOMEM;
2237 goto bad_pending_cache;
2240 tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
2241 if (!tracked_chunk_cache) {
2242 DMERR("Couldn't create cache to track chunks in use.");
2243 r = -ENOMEM;
2244 goto bad_tracked_chunk_cache;
2247 return 0;
2249 bad_tracked_chunk_cache:
2250 kmem_cache_destroy(pending_cache);
2251 bad_pending_cache:
2252 kmem_cache_destroy(exception_cache);
2253 bad_exception_cache:
2254 exit_origin_hash();
2255 bad_origin_hash:
2256 dm_unregister_target(&merge_target);
2257 bad_register_merge_target:
2258 dm_unregister_target(&origin_target);
2259 bad_register_origin_target:
2260 dm_unregister_target(&snapshot_target);
2261 bad_register_snapshot_target:
2262 dm_exception_store_exit();
2264 return r;
2267 static void __exit dm_snapshot_exit(void)
2269 dm_unregister_target(&snapshot_target);
2270 dm_unregister_target(&origin_target);
2271 dm_unregister_target(&merge_target);
2273 exit_origin_hash();
2274 kmem_cache_destroy(pending_cache);
2275 kmem_cache_destroy(exception_cache);
2276 kmem_cache_destroy(tracked_chunk_cache);
2278 dm_exception_store_exit();
2281 /* Module hooks */
2282 module_init(dm_snapshot_init);
2283 module_exit(dm_snapshot_exit);
2285 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2286 MODULE_AUTHOR("Joe Thornber");
2287 MODULE_LICENSE("GPL");