4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
6 * This file is released under the GPL.
9 #include <linux/blkdev.h>
10 #include <linux/device-mapper.h>
11 #include <linux/delay.h>
13 #include <linux/init.h>
14 #include <linux/kdev_t.h>
15 #include <linux/list.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/log2.h>
21 #include <linux/dm-kcopyd.h>
22 #include <linux/workqueue.h>
24 #include "dm-exception-store.h"
26 #define DM_MSG_PREFIX "snapshots"
29 * The percentage increment we will wake up users at
31 #define WAKE_UP_PERCENT 5
34 * kcopyd priority of snapshot operations
36 #define SNAPSHOT_COPY_PRIORITY 2
39 * Reserve 1MB for each snapshot initially (with minimum of 1 page).
41 #define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
44 * The size of the mempool used to track chunks in use.
48 #define DM_TRACKED_CHUNK_HASH_SIZE 16
49 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
50 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
52 struct dm_exception_table
{
55 struct list_head
*table
;
59 struct rw_semaphore lock
;
61 struct dm_dev
*origin
;
66 /* List of snapshots per Origin */
67 struct list_head list
;
69 /* You can't use a snapshot if this is 0 (e.g. if full) */
72 /* Origin writes don't trigger exceptions until this is set */
75 /* Whether or not owning mapped_device is suspended */
78 mempool_t
*pending_pool
;
80 atomic_t pending_exceptions_count
;
82 struct dm_exception_table pending
;
83 struct dm_exception_table complete
;
86 * pe_lock protects all pending_exception operations and access
87 * as well as the snapshot_bios list.
91 /* The on disk metadata handler */
92 struct dm_exception_store
*store
;
94 struct dm_kcopyd_client
*kcopyd_client
;
96 /* Queue of snapshot writes for ksnapd to flush */
97 struct bio_list queued_bios
;
98 struct work_struct queued_bios_work
;
100 /* Chunks with outstanding reads */
101 mempool_t
*tracked_chunk_pool
;
102 spinlock_t tracked_chunk_lock
;
103 struct hlist_head tracked_chunk_hash
[DM_TRACKED_CHUNK_HASH_SIZE
];
106 struct dm_dev
*dm_snap_cow(struct dm_snapshot
*s
)
110 EXPORT_SYMBOL(dm_snap_cow
);
112 static struct workqueue_struct
*ksnapd
;
113 static void flush_queued_bios(struct work_struct
*work
);
115 static sector_t
chunk_to_sector(struct dm_exception_store
*store
,
118 return chunk
<< store
->chunk_shift
;
121 static int bdev_equal(struct block_device
*lhs
, struct block_device
*rhs
)
124 * There is only ever one instance of a particular block
125 * device so we can compare pointers safely.
130 struct dm_snap_pending_exception
{
131 struct dm_exception e
;
134 * Origin buffers waiting for this to complete are held
137 struct bio_list origin_bios
;
138 struct bio_list snapshot_bios
;
141 * Short-term queue of pending exceptions prior to submission.
143 struct list_head list
;
146 * The primary pending_exception is the one that holds
147 * the ref_count and the list of origin_bios for a
148 * group of pending_exceptions. It is always last to get freed.
149 * These fields get set up when writing to the origin.
151 struct dm_snap_pending_exception
*primary_pe
;
154 * Number of pending_exceptions processing this chunk.
155 * When this drops to zero we must complete the origin bios.
156 * If incrementing or decrementing this, hold pe->snap->lock for
157 * the sibling concerned and not pe->primary_pe->snap->lock unless
162 /* Pointer back to snapshot context */
163 struct dm_snapshot
*snap
;
166 * 1 indicates the exception has already been sent to
173 * Hash table mapping origin volumes to lists of snapshots and
174 * a lock to protect it
176 static struct kmem_cache
*exception_cache
;
177 static struct kmem_cache
*pending_cache
;
179 struct dm_snap_tracked_chunk
{
180 struct hlist_node node
;
184 static struct kmem_cache
*tracked_chunk_cache
;
186 static struct dm_snap_tracked_chunk
*track_chunk(struct dm_snapshot
*s
,
189 struct dm_snap_tracked_chunk
*c
= mempool_alloc(s
->tracked_chunk_pool
,
195 spin_lock_irqsave(&s
->tracked_chunk_lock
, flags
);
196 hlist_add_head(&c
->node
,
197 &s
->tracked_chunk_hash
[DM_TRACKED_CHUNK_HASH(chunk
)]);
198 spin_unlock_irqrestore(&s
->tracked_chunk_lock
, flags
);
203 static void stop_tracking_chunk(struct dm_snapshot
*s
,
204 struct dm_snap_tracked_chunk
*c
)
208 spin_lock_irqsave(&s
->tracked_chunk_lock
, flags
);
210 spin_unlock_irqrestore(&s
->tracked_chunk_lock
, flags
);
212 mempool_free(c
, s
->tracked_chunk_pool
);
215 static int __chunk_is_tracked(struct dm_snapshot
*s
, chunk_t chunk
)
217 struct dm_snap_tracked_chunk
*c
;
218 struct hlist_node
*hn
;
221 spin_lock_irq(&s
->tracked_chunk_lock
);
223 hlist_for_each_entry(c
, hn
,
224 &s
->tracked_chunk_hash
[DM_TRACKED_CHUNK_HASH(chunk
)], node
) {
225 if (c
->chunk
== chunk
) {
231 spin_unlock_irq(&s
->tracked_chunk_lock
);
237 * One of these per registered origin, held in the snapshot_origins hash
240 /* The origin device */
241 struct block_device
*bdev
;
243 struct list_head hash_list
;
245 /* List of snapshots for this origin */
246 struct list_head snapshots
;
250 * Size of the hash table for origin volumes. If we make this
251 * the size of the minors list then it should be nearly perfect
253 #define ORIGIN_HASH_SIZE 256
254 #define ORIGIN_MASK 0xFF
255 static struct list_head
*_origins
;
256 static struct rw_semaphore _origins_lock
;
258 static int init_origin_hash(void)
262 _origins
= kmalloc(ORIGIN_HASH_SIZE
* sizeof(struct list_head
),
265 DMERR("unable to allocate memory");
269 for (i
= 0; i
< ORIGIN_HASH_SIZE
; i
++)
270 INIT_LIST_HEAD(_origins
+ i
);
271 init_rwsem(&_origins_lock
);
276 static void exit_origin_hash(void)
281 static unsigned origin_hash(struct block_device
*bdev
)
283 return bdev
->bd_dev
& ORIGIN_MASK
;
286 static struct origin
*__lookup_origin(struct block_device
*origin
)
288 struct list_head
*ol
;
291 ol
= &_origins
[origin_hash(origin
)];
292 list_for_each_entry (o
, ol
, hash_list
)
293 if (bdev_equal(o
->bdev
, origin
))
299 static void __insert_origin(struct origin
*o
)
301 struct list_head
*sl
= &_origins
[origin_hash(o
->bdev
)];
302 list_add_tail(&o
->hash_list
, sl
);
306 * _origins_lock must be held when calling this function.
307 * Returns number of snapshots registered using the supplied cow device, plus:
308 * snap_src - a snapshot suitable for use as a source of exception handover
309 * snap_dest - a snapshot capable of receiving exception handover.
311 * Possible return values and states:
312 * 0: NULL, NULL - first new snapshot
313 * 1: snap_src, NULL - normal snapshot
314 * 2: snap_src, snap_dest - waiting for handover
315 * 2: snap_src, NULL - handed over, waiting for old to be deleted
316 * 1: NULL, snap_dest - source got destroyed without handover
318 static int __find_snapshots_sharing_cow(struct dm_snapshot
*snap
,
319 struct dm_snapshot
**snap_src
,
320 struct dm_snapshot
**snap_dest
)
322 struct dm_snapshot
*s
;
327 o
= __lookup_origin(snap
->origin
->bdev
);
331 list_for_each_entry(s
, &o
->snapshots
, list
) {
332 if (!bdev_equal(s
->cow
->bdev
, snap
->cow
->bdev
))
342 } else if (snap_dest
)
353 * On success, returns 1 if this snapshot is a handover destination,
354 * otherwise returns 0.
356 static int __validate_exception_handover(struct dm_snapshot
*snap
)
358 struct dm_snapshot
*snap_src
= NULL
, *snap_dest
= NULL
;
360 /* Does snapshot need exceptions handed over to it? */
361 if ((__find_snapshots_sharing_cow(snap
, &snap_src
, &snap_dest
) == 2) ||
363 snap
->ti
->error
= "Snapshot cow pairing for exception "
364 "table handover failed";
369 * If no snap_src was found, snap cannot become a handover
378 static void __insert_snapshot(struct origin
*o
, struct dm_snapshot
*s
)
380 struct dm_snapshot
*l
;
382 /* Sort the list according to chunk size, largest-first smallest-last */
383 list_for_each_entry(l
, &o
->snapshots
, list
)
384 if (l
->store
->chunk_size
< s
->store
->chunk_size
)
386 list_add_tail(&s
->list
, &l
->list
);
390 * Make a note of the snapshot and its origin so we can look it
391 * up when the origin has a write on it.
393 * Also validate snapshot exception store handovers.
394 * On success, returns 1 if this registration is a handover destination,
395 * otherwise returns 0.
397 static int register_snapshot(struct dm_snapshot
*snap
)
399 struct origin
*o
, *new_o
= NULL
;
400 struct block_device
*bdev
= snap
->origin
->bdev
;
403 new_o
= kmalloc(sizeof(*new_o
), GFP_KERNEL
);
407 down_write(&_origins_lock
);
409 r
= __validate_exception_handover(snap
);
415 o
= __lookup_origin(bdev
);
422 /* Initialise the struct */
423 INIT_LIST_HEAD(&o
->snapshots
);
429 __insert_snapshot(o
, snap
);
432 up_write(&_origins_lock
);
438 * Move snapshot to correct place in list according to chunk size.
440 static void reregister_snapshot(struct dm_snapshot
*s
)
442 struct block_device
*bdev
= s
->origin
->bdev
;
444 down_write(&_origins_lock
);
447 __insert_snapshot(__lookup_origin(bdev
), s
);
449 up_write(&_origins_lock
);
452 static void unregister_snapshot(struct dm_snapshot
*s
)
456 down_write(&_origins_lock
);
457 o
= __lookup_origin(s
->origin
->bdev
);
460 if (o
&& list_empty(&o
->snapshots
)) {
461 list_del(&o
->hash_list
);
465 up_write(&_origins_lock
);
469 * Implementation of the exception hash tables.
470 * The lowest hash_shift bits of the chunk number are ignored, allowing
471 * some consecutive chunks to be grouped together.
473 static int dm_exception_table_init(struct dm_exception_table
*et
,
474 uint32_t size
, unsigned hash_shift
)
478 et
->hash_shift
= hash_shift
;
479 et
->hash_mask
= size
- 1;
480 et
->table
= dm_vcalloc(size
, sizeof(struct list_head
));
484 for (i
= 0; i
< size
; i
++)
485 INIT_LIST_HEAD(et
->table
+ i
);
490 static void dm_exception_table_exit(struct dm_exception_table
*et
,
491 struct kmem_cache
*mem
)
493 struct list_head
*slot
;
494 struct dm_exception
*ex
, *next
;
497 size
= et
->hash_mask
+ 1;
498 for (i
= 0; i
< size
; i
++) {
499 slot
= et
->table
+ i
;
501 list_for_each_entry_safe (ex
, next
, slot
, hash_list
)
502 kmem_cache_free(mem
, ex
);
508 static uint32_t exception_hash(struct dm_exception_table
*et
, chunk_t chunk
)
510 return (chunk
>> et
->hash_shift
) & et
->hash_mask
;
513 static void dm_remove_exception(struct dm_exception
*e
)
515 list_del(&e
->hash_list
);
519 * Return the exception data for a sector, or NULL if not
522 static struct dm_exception
*dm_lookup_exception(struct dm_exception_table
*et
,
525 struct list_head
*slot
;
526 struct dm_exception
*e
;
528 slot
= &et
->table
[exception_hash(et
, chunk
)];
529 list_for_each_entry (e
, slot
, hash_list
)
530 if (chunk
>= e
->old_chunk
&&
531 chunk
<= e
->old_chunk
+ dm_consecutive_chunk_count(e
))
537 static struct dm_exception
*alloc_completed_exception(void)
539 struct dm_exception
*e
;
541 e
= kmem_cache_alloc(exception_cache
, GFP_NOIO
);
543 e
= kmem_cache_alloc(exception_cache
, GFP_ATOMIC
);
548 static void free_completed_exception(struct dm_exception
*e
)
550 kmem_cache_free(exception_cache
, e
);
553 static struct dm_snap_pending_exception
*alloc_pending_exception(struct dm_snapshot
*s
)
555 struct dm_snap_pending_exception
*pe
= mempool_alloc(s
->pending_pool
,
558 atomic_inc(&s
->pending_exceptions_count
);
564 static void free_pending_exception(struct dm_snap_pending_exception
*pe
)
566 struct dm_snapshot
*s
= pe
->snap
;
568 mempool_free(pe
, s
->pending_pool
);
569 smp_mb__before_atomic_dec();
570 atomic_dec(&s
->pending_exceptions_count
);
573 static void dm_insert_exception(struct dm_exception_table
*eh
,
574 struct dm_exception
*new_e
)
577 struct dm_exception
*e
= NULL
;
579 l
= &eh
->table
[exception_hash(eh
, new_e
->old_chunk
)];
581 /* Add immediately if this table doesn't support consecutive chunks */
585 /* List is ordered by old_chunk */
586 list_for_each_entry_reverse(e
, l
, hash_list
) {
587 /* Insert after an existing chunk? */
588 if (new_e
->old_chunk
== (e
->old_chunk
+
589 dm_consecutive_chunk_count(e
) + 1) &&
590 new_e
->new_chunk
== (dm_chunk_number(e
->new_chunk
) +
591 dm_consecutive_chunk_count(e
) + 1)) {
592 dm_consecutive_chunk_count_inc(e
);
593 free_completed_exception(new_e
);
597 /* Insert before an existing chunk? */
598 if (new_e
->old_chunk
== (e
->old_chunk
- 1) &&
599 new_e
->new_chunk
== (dm_chunk_number(e
->new_chunk
) - 1)) {
600 dm_consecutive_chunk_count_inc(e
);
603 free_completed_exception(new_e
);
607 if (new_e
->old_chunk
> e
->old_chunk
)
612 list_add(&new_e
->hash_list
, e
? &e
->hash_list
: l
);
616 * Callback used by the exception stores to load exceptions when
619 static int dm_add_exception(void *context
, chunk_t old
, chunk_t
new)
621 struct dm_snapshot
*s
= context
;
622 struct dm_exception
*e
;
624 e
= alloc_completed_exception();
630 /* Consecutive_count is implicitly initialised to zero */
633 dm_insert_exception(&s
->complete
, e
);
638 #define min_not_zero(l, r) (((l) == 0) ? (r) : (((r) == 0) ? (l) : min(l, r)))
641 * Return a minimum chunk size of all snapshots that have the specified origin.
642 * Return zero if the origin has no snapshots.
644 static sector_t
__minimum_chunk_size(struct origin
*o
)
646 struct dm_snapshot
*snap
;
647 unsigned chunk_size
= 0;
650 list_for_each_entry(snap
, &o
->snapshots
, list
)
651 chunk_size
= min_not_zero(chunk_size
,
652 snap
->store
->chunk_size
);
660 static int calc_max_buckets(void)
662 /* use a fixed size of 2MB */
663 unsigned long mem
= 2 * 1024 * 1024;
664 mem
/= sizeof(struct list_head
);
670 * Allocate room for a suitable hash table.
672 static int init_hash_tables(struct dm_snapshot
*s
)
674 sector_t hash_size
, cow_dev_size
, origin_dev_size
, max_buckets
;
677 * Calculate based on the size of the original volume or
680 cow_dev_size
= get_dev_size(s
->cow
->bdev
);
681 origin_dev_size
= get_dev_size(s
->origin
->bdev
);
682 max_buckets
= calc_max_buckets();
684 hash_size
= min(origin_dev_size
, cow_dev_size
) >> s
->store
->chunk_shift
;
685 hash_size
= min(hash_size
, max_buckets
);
689 hash_size
= rounddown_pow_of_two(hash_size
);
690 if (dm_exception_table_init(&s
->complete
, hash_size
,
691 DM_CHUNK_CONSECUTIVE_BITS
))
695 * Allocate hash table for in-flight exceptions
696 * Make this smaller than the real hash table
702 if (dm_exception_table_init(&s
->pending
, hash_size
, 0)) {
703 dm_exception_table_exit(&s
->complete
, exception_cache
);
711 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
713 static int snapshot_ctr(struct dm_target
*ti
, unsigned int argc
, char **argv
)
715 struct dm_snapshot
*s
;
718 char *origin_path
, *cow_path
;
722 ti
->error
= "requires exactly 4 arguments";
727 origin_path
= argv
[0];
731 s
= kmalloc(sizeof(*s
), GFP_KERNEL
);
733 ti
->error
= "Cannot allocate snapshot context private "
743 r
= dm_get_device(ti
, cow_path
, 0, 0,
744 FMODE_READ
| FMODE_WRITE
, &s
->cow
);
746 ti
->error
= "Cannot get COW device";
750 r
= dm_exception_store_create(ti
, argc
, argv
, s
, &args_used
, &s
->store
);
752 ti
->error
= "Couldn't create exception store";
760 r
= dm_get_device(ti
, origin_path
, 0, ti
->len
, FMODE_READ
, &s
->origin
);
762 ti
->error
= "Cannot get origin device";
770 atomic_set(&s
->pending_exceptions_count
, 0);
771 init_rwsem(&s
->lock
);
772 INIT_LIST_HEAD(&s
->list
);
773 spin_lock_init(&s
->pe_lock
);
775 /* Allocate hash table for COW data */
776 if (init_hash_tables(s
)) {
777 ti
->error
= "Unable to allocate hash table space";
779 goto bad_hash_tables
;
782 r
= dm_kcopyd_client_create(SNAPSHOT_PAGES
, &s
->kcopyd_client
);
784 ti
->error
= "Could not create kcopyd client";
788 s
->pending_pool
= mempool_create_slab_pool(MIN_IOS
, pending_cache
);
789 if (!s
->pending_pool
) {
790 ti
->error
= "Could not allocate mempool for pending exceptions";
791 goto bad_pending_pool
;
794 s
->tracked_chunk_pool
= mempool_create_slab_pool(MIN_IOS
,
795 tracked_chunk_cache
);
796 if (!s
->tracked_chunk_pool
) {
797 ti
->error
= "Could not allocate tracked_chunk mempool for "
799 goto bad_tracked_chunk_pool
;
802 for (i
= 0; i
< DM_TRACKED_CHUNK_HASH_SIZE
; i
++)
803 INIT_HLIST_HEAD(&s
->tracked_chunk_hash
[i
]);
805 spin_lock_init(&s
->tracked_chunk_lock
);
807 bio_list_init(&s
->queued_bios
);
808 INIT_WORK(&s
->queued_bios_work
, flush_queued_bios
);
811 ti
->num_flush_requests
= 1;
813 /* Add snapshot to the list of snapshots for this origin */
814 /* Exceptions aren't triggered till snapshot_resume() is called */
815 r
= register_snapshot(s
);
817 ti
->error
= "Snapshot origin struct allocation failed";
818 goto bad_load_and_register
;
820 /* invalid handover, register_snapshot has set ti->error */
821 goto bad_load_and_register
;
825 * Metadata must only be loaded into one table at once, so skip this
826 * if metadata will be handed over during resume.
827 * Chunk size will be set during the handover - set it to zero to
828 * ensure it's ignored.
831 s
->store
->chunk_size
= 0;
835 r
= s
->store
->type
->read_metadata(s
->store
, dm_add_exception
,
838 ti
->error
= "Failed to read snapshot metadata";
839 goto bad_read_metadata
;
842 DMWARN("Snapshot is marked invalid.");
845 if (!s
->store
->chunk_size
) {
846 ti
->error
= "Chunk size not set";
847 goto bad_read_metadata
;
849 ti
->split_io
= s
->store
->chunk_size
;
854 unregister_snapshot(s
);
856 bad_load_and_register
:
857 mempool_destroy(s
->tracked_chunk_pool
);
859 bad_tracked_chunk_pool
:
860 mempool_destroy(s
->pending_pool
);
863 dm_kcopyd_client_destroy(s
->kcopyd_client
);
866 dm_exception_table_exit(&s
->pending
, pending_cache
);
867 dm_exception_table_exit(&s
->complete
, exception_cache
);
870 dm_put_device(ti
, s
->origin
);
873 dm_exception_store_destroy(s
->store
);
876 dm_put_device(ti
, s
->cow
);
885 static void __free_exceptions(struct dm_snapshot
*s
)
887 dm_kcopyd_client_destroy(s
->kcopyd_client
);
888 s
->kcopyd_client
= NULL
;
890 dm_exception_table_exit(&s
->pending
, pending_cache
);
891 dm_exception_table_exit(&s
->complete
, exception_cache
);
894 static void __handover_exceptions(struct dm_snapshot
*snap_src
,
895 struct dm_snapshot
*snap_dest
)
898 struct dm_exception_table table_swap
;
899 struct dm_exception_store
*store_swap
;
903 * Swap all snapshot context information between the two instances.
905 u
.table_swap
= snap_dest
->complete
;
906 snap_dest
->complete
= snap_src
->complete
;
907 snap_src
->complete
= u
.table_swap
;
909 u
.store_swap
= snap_dest
->store
;
910 snap_dest
->store
= snap_src
->store
;
911 snap_src
->store
= u
.store_swap
;
913 snap_dest
->store
->snap
= snap_dest
;
914 snap_src
->store
->snap
= snap_src
;
916 snap_dest
->ti
->split_io
= snap_dest
->store
->chunk_size
;
917 snap_dest
->valid
= snap_src
->valid
;
920 * Set source invalid to ensure it receives no further I/O.
925 static void snapshot_dtr(struct dm_target
*ti
)
927 #ifdef CONFIG_DM_DEBUG
930 struct dm_snapshot
*s
= ti
->private;
931 struct dm_snapshot
*snap_src
= NULL
, *snap_dest
= NULL
;
933 flush_workqueue(ksnapd
);
935 down_read(&_origins_lock
);
936 /* Check whether exception handover must be cancelled */
937 (void) __find_snapshots_sharing_cow(s
, &snap_src
, &snap_dest
);
938 if (snap_src
&& snap_dest
&& (s
== snap_src
)) {
939 down_write(&snap_dest
->lock
);
940 snap_dest
->valid
= 0;
941 up_write(&snap_dest
->lock
);
942 DMERR("Cancelling snapshot handover.");
944 up_read(&_origins_lock
);
946 /* Prevent further origin writes from using this snapshot. */
947 /* After this returns there can be no new kcopyd jobs. */
948 unregister_snapshot(s
);
950 while (atomic_read(&s
->pending_exceptions_count
))
953 * Ensure instructions in mempool_destroy aren't reordered
954 * before atomic_read.
958 #ifdef CONFIG_DM_DEBUG
959 for (i
= 0; i
< DM_TRACKED_CHUNK_HASH_SIZE
; i
++)
960 BUG_ON(!hlist_empty(&s
->tracked_chunk_hash
[i
]));
963 mempool_destroy(s
->tracked_chunk_pool
);
965 __free_exceptions(s
);
967 mempool_destroy(s
->pending_pool
);
969 dm_put_device(ti
, s
->origin
);
971 dm_exception_store_destroy(s
->store
);
973 dm_put_device(ti
, s
->cow
);
979 * Flush a list of buffers.
981 static void flush_bios(struct bio
*bio
)
988 generic_make_request(bio
);
993 static void flush_queued_bios(struct work_struct
*work
)
995 struct dm_snapshot
*s
=
996 container_of(work
, struct dm_snapshot
, queued_bios_work
);
997 struct bio
*queued_bios
;
1000 spin_lock_irqsave(&s
->pe_lock
, flags
);
1001 queued_bios
= bio_list_get(&s
->queued_bios
);
1002 spin_unlock_irqrestore(&s
->pe_lock
, flags
);
1004 flush_bios(queued_bios
);
1008 * Error a list of buffers.
1010 static void error_bios(struct bio
*bio
)
1016 bio
->bi_next
= NULL
;
1022 static void __invalidate_snapshot(struct dm_snapshot
*s
, int err
)
1028 DMERR("Invalidating snapshot: Error reading/writing.");
1029 else if (err
== -ENOMEM
)
1030 DMERR("Invalidating snapshot: Unable to allocate exception.");
1032 if (s
->store
->type
->drop_snapshot
)
1033 s
->store
->type
->drop_snapshot(s
->store
);
1037 dm_table_event(s
->ti
->table
);
1040 static void get_pending_exception(struct dm_snap_pending_exception
*pe
)
1042 atomic_inc(&pe
->ref_count
);
1045 static struct bio
*put_pending_exception(struct dm_snap_pending_exception
*pe
)
1047 struct dm_snap_pending_exception
*primary_pe
;
1048 struct bio
*origin_bios
= NULL
;
1050 primary_pe
= pe
->primary_pe
;
1053 * If this pe is involved in a write to the origin and
1054 * it is the last sibling to complete then release
1055 * the bios for the original write to the origin.
1058 atomic_dec_and_test(&primary_pe
->ref_count
)) {
1059 origin_bios
= bio_list_get(&primary_pe
->origin_bios
);
1060 free_pending_exception(primary_pe
);
1064 * Free the pe if it's not linked to an origin write or if
1065 * it's not itself a primary pe.
1067 if (!primary_pe
|| primary_pe
!= pe
)
1068 free_pending_exception(pe
);
1073 static void pending_complete(struct dm_snap_pending_exception
*pe
, int success
)
1075 struct dm_exception
*e
;
1076 struct dm_snapshot
*s
= pe
->snap
;
1077 struct bio
*origin_bios
= NULL
;
1078 struct bio
*snapshot_bios
= NULL
;
1082 /* Read/write error - snapshot is unusable */
1083 down_write(&s
->lock
);
1084 __invalidate_snapshot(s
, -EIO
);
1089 e
= alloc_completed_exception();
1091 down_write(&s
->lock
);
1092 __invalidate_snapshot(s
, -ENOMEM
);
1098 down_write(&s
->lock
);
1100 free_completed_exception(e
);
1106 * Check for conflicting reads. This is extremely improbable,
1107 * so msleep(1) is sufficient and there is no need for a wait queue.
1109 while (__chunk_is_tracked(s
, pe
->e
.old_chunk
))
1113 * Add a proper exception, and remove the
1114 * in-flight exception from the list.
1116 dm_insert_exception(&s
->complete
, e
);
1119 dm_remove_exception(&pe
->e
);
1120 snapshot_bios
= bio_list_get(&pe
->snapshot_bios
);
1121 origin_bios
= put_pending_exception(pe
);
1125 /* Submit any pending write bios */
1127 error_bios(snapshot_bios
);
1129 flush_bios(snapshot_bios
);
1131 flush_bios(origin_bios
);
1134 static void commit_callback(void *context
, int success
)
1136 struct dm_snap_pending_exception
*pe
= context
;
1138 pending_complete(pe
, success
);
1142 * Called when the copy I/O has finished. kcopyd actually runs
1143 * this code so don't block.
1145 static void copy_callback(int read_err
, unsigned long write_err
, void *context
)
1147 struct dm_snap_pending_exception
*pe
= context
;
1148 struct dm_snapshot
*s
= pe
->snap
;
1150 if (read_err
|| write_err
)
1151 pending_complete(pe
, 0);
1154 /* Update the metadata if we are persistent */
1155 s
->store
->type
->commit_exception(s
->store
, &pe
->e
,
1156 commit_callback
, pe
);
1160 * Dispatches the copy operation to kcopyd.
1162 static void start_copy(struct dm_snap_pending_exception
*pe
)
1164 struct dm_snapshot
*s
= pe
->snap
;
1165 struct dm_io_region src
, dest
;
1166 struct block_device
*bdev
= s
->origin
->bdev
;
1169 dev_size
= get_dev_size(bdev
);
1172 src
.sector
= chunk_to_sector(s
->store
, pe
->e
.old_chunk
);
1173 src
.count
= min((sector_t
)s
->store
->chunk_size
, dev_size
- src
.sector
);
1175 dest
.bdev
= s
->cow
->bdev
;
1176 dest
.sector
= chunk_to_sector(s
->store
, pe
->e
.new_chunk
);
1177 dest
.count
= src
.count
;
1179 /* Hand over to kcopyd */
1180 dm_kcopyd_copy(s
->kcopyd_client
,
1181 &src
, 1, &dest
, 0, copy_callback
, pe
);
1184 static struct dm_snap_pending_exception
*
1185 __lookup_pending_exception(struct dm_snapshot
*s
, chunk_t chunk
)
1187 struct dm_exception
*e
= dm_lookup_exception(&s
->pending
, chunk
);
1192 return container_of(e
, struct dm_snap_pending_exception
, e
);
1196 * Looks to see if this snapshot already has a pending exception
1197 * for this chunk, otherwise it allocates a new one and inserts
1198 * it into the pending table.
1200 * NOTE: a write lock must be held on snap->lock before calling
1203 static struct dm_snap_pending_exception
*
1204 __find_pending_exception(struct dm_snapshot
*s
,
1205 struct dm_snap_pending_exception
*pe
, chunk_t chunk
)
1207 struct dm_snap_pending_exception
*pe2
;
1209 pe2
= __lookup_pending_exception(s
, chunk
);
1211 free_pending_exception(pe
);
1215 pe
->e
.old_chunk
= chunk
;
1216 bio_list_init(&pe
->origin_bios
);
1217 bio_list_init(&pe
->snapshot_bios
);
1218 pe
->primary_pe
= NULL
;
1219 atomic_set(&pe
->ref_count
, 0);
1222 if (s
->store
->type
->prepare_exception(s
->store
, &pe
->e
)) {
1223 free_pending_exception(pe
);
1227 get_pending_exception(pe
);
1228 dm_insert_exception(&s
->pending
, &pe
->e
);
1233 static void remap_exception(struct dm_snapshot
*s
, struct dm_exception
*e
,
1234 struct bio
*bio
, chunk_t chunk
)
1236 bio
->bi_bdev
= s
->cow
->bdev
;
1237 bio
->bi_sector
= chunk_to_sector(s
->store
,
1238 dm_chunk_number(e
->new_chunk
) +
1239 (chunk
- e
->old_chunk
)) +
1241 s
->store
->chunk_mask
);
1244 static int snapshot_map(struct dm_target
*ti
, struct bio
*bio
,
1245 union map_info
*map_context
)
1247 struct dm_exception
*e
;
1248 struct dm_snapshot
*s
= ti
->private;
1249 int r
= DM_MAPIO_REMAPPED
;
1251 struct dm_snap_pending_exception
*pe
= NULL
;
1253 if (unlikely(bio_empty_barrier(bio
))) {
1254 bio
->bi_bdev
= s
->cow
->bdev
;
1255 return DM_MAPIO_REMAPPED
;
1258 chunk
= sector_to_chunk(s
->store
, bio
->bi_sector
);
1260 /* Full snapshots are not usable */
1261 /* To get here the table must be live so s->active is always set. */
1265 /* FIXME: should only take write lock if we need
1266 * to copy an exception */
1267 down_write(&s
->lock
);
1274 /* If the block is already remapped - use that, else remap it */
1275 e
= dm_lookup_exception(&s
->complete
, chunk
);
1277 remap_exception(s
, e
, bio
, chunk
);
1282 * Write to snapshot - higher level takes care of RW/RO
1283 * flags so we should only get this if we are
1286 if (bio_rw(bio
) == WRITE
) {
1287 pe
= __lookup_pending_exception(s
, chunk
);
1290 pe
= alloc_pending_exception(s
);
1291 down_write(&s
->lock
);
1294 free_pending_exception(pe
);
1299 e
= dm_lookup_exception(&s
->complete
, chunk
);
1301 free_pending_exception(pe
);
1302 remap_exception(s
, e
, bio
, chunk
);
1306 pe
= __find_pending_exception(s
, pe
, chunk
);
1308 __invalidate_snapshot(s
, -ENOMEM
);
1314 remap_exception(s
, &pe
->e
, bio
, chunk
);
1315 bio_list_add(&pe
->snapshot_bios
, bio
);
1317 r
= DM_MAPIO_SUBMITTED
;
1320 /* this is protected by snap->lock */
1327 bio
->bi_bdev
= s
->origin
->bdev
;
1328 map_context
->ptr
= track_chunk(s
, chunk
);
1337 static int snapshot_end_io(struct dm_target
*ti
, struct bio
*bio
,
1338 int error
, union map_info
*map_context
)
1340 struct dm_snapshot
*s
= ti
->private;
1341 struct dm_snap_tracked_chunk
*c
= map_context
->ptr
;
1344 stop_tracking_chunk(s
, c
);
1349 static void snapshot_postsuspend(struct dm_target
*ti
)
1351 struct dm_snapshot
*s
= ti
->private;
1353 down_write(&s
->lock
);
1358 static int snapshot_preresume(struct dm_target
*ti
)
1361 struct dm_snapshot
*s
= ti
->private;
1362 struct dm_snapshot
*snap_src
= NULL
, *snap_dest
= NULL
;
1364 down_read(&_origins_lock
);
1365 (void) __find_snapshots_sharing_cow(s
, &snap_src
, &snap_dest
);
1366 if (snap_src
&& snap_dest
) {
1367 down_read(&snap_src
->lock
);
1368 if (s
== snap_src
) {
1369 DMERR("Unable to resume snapshot source until "
1370 "handover completes.");
1372 } else if (!snap_src
->suspended
) {
1373 DMERR("Unable to perform snapshot handover until "
1374 "source is suspended.");
1377 up_read(&snap_src
->lock
);
1379 up_read(&_origins_lock
);
1384 static void snapshot_resume(struct dm_target
*ti
)
1386 struct dm_snapshot
*s
= ti
->private;
1387 struct dm_snapshot
*snap_src
= NULL
, *snap_dest
= NULL
;
1389 down_read(&_origins_lock
);
1390 (void) __find_snapshots_sharing_cow(s
, &snap_src
, &snap_dest
);
1391 if (snap_src
&& snap_dest
) {
1392 down_write(&snap_src
->lock
);
1393 down_write_nested(&snap_dest
->lock
, SINGLE_DEPTH_NESTING
);
1394 __handover_exceptions(snap_src
, snap_dest
);
1395 up_write(&snap_dest
->lock
);
1396 up_write(&snap_src
->lock
);
1398 up_read(&_origins_lock
);
1400 /* Now we have correct chunk size, reregister */
1401 reregister_snapshot(s
);
1403 down_write(&s
->lock
);
1409 static int snapshot_status(struct dm_target
*ti
, status_type_t type
,
1410 char *result
, unsigned int maxlen
)
1413 struct dm_snapshot
*snap
= ti
->private;
1416 case STATUSTYPE_INFO
:
1418 down_write(&snap
->lock
);
1423 if (snap
->store
->type
->usage
) {
1424 sector_t total_sectors
, sectors_allocated
,
1426 snap
->store
->type
->usage(snap
->store
,
1430 DMEMIT("%llu/%llu %llu",
1431 (unsigned long long)sectors_allocated
,
1432 (unsigned long long)total_sectors
,
1433 (unsigned long long)metadata_sectors
);
1439 up_write(&snap
->lock
);
1443 case STATUSTYPE_TABLE
:
1445 * kdevname returns a static pointer so we need
1446 * to make private copies if the output is to
1449 DMEMIT("%s %s", snap
->origin
->name
, snap
->cow
->name
);
1450 snap
->store
->type
->status(snap
->store
, type
, result
+ sz
,
1458 static int snapshot_iterate_devices(struct dm_target
*ti
,
1459 iterate_devices_callout_fn fn
, void *data
)
1461 struct dm_snapshot
*snap
= ti
->private;
1463 return fn(ti
, snap
->origin
, 0, ti
->len
, data
);
1467 /*-----------------------------------------------------------------
1469 *---------------------------------------------------------------*/
1470 static int __origin_write(struct list_head
*snapshots
, struct bio
*bio
)
1472 int r
= DM_MAPIO_REMAPPED
, first
= 0;
1473 struct dm_snapshot
*snap
;
1474 struct dm_exception
*e
;
1475 struct dm_snap_pending_exception
*pe
, *next_pe
, *primary_pe
= NULL
;
1477 LIST_HEAD(pe_queue
);
1479 /* Do all the snapshots on this origin */
1480 list_for_each_entry (snap
, snapshots
, list
) {
1482 down_write(&snap
->lock
);
1484 /* Only deal with valid and active snapshots */
1485 if (!snap
->valid
|| !snap
->active
)
1488 /* Nothing to do if writing beyond end of snapshot */
1489 if (bio
->bi_sector
>= dm_table_get_size(snap
->ti
->table
))
1493 * Remember, different snapshots can have
1494 * different chunk sizes.
1496 chunk
= sector_to_chunk(snap
->store
, bio
->bi_sector
);
1499 * Check exception table to see if block
1500 * is already remapped in this snapshot
1501 * and trigger an exception if not.
1503 * ref_count is initialised to 1 so pending_complete()
1504 * won't destroy the primary_pe while we're inside this loop.
1506 e
= dm_lookup_exception(&snap
->complete
, chunk
);
1510 pe
= __lookup_pending_exception(snap
, chunk
);
1512 up_write(&snap
->lock
);
1513 pe
= alloc_pending_exception(snap
);
1514 down_write(&snap
->lock
);
1517 free_pending_exception(pe
);
1521 e
= dm_lookup_exception(&snap
->complete
, chunk
);
1523 free_pending_exception(pe
);
1527 pe
= __find_pending_exception(snap
, pe
, chunk
);
1529 __invalidate_snapshot(snap
, -ENOMEM
);
1536 * Either every pe here has same
1537 * primary_pe or none has one yet.
1540 primary_pe
= pe
->primary_pe
;
1546 bio_list_add(&primary_pe
->origin_bios
, bio
);
1548 r
= DM_MAPIO_SUBMITTED
;
1551 if (!pe
->primary_pe
) {
1552 pe
->primary_pe
= primary_pe
;
1553 get_pending_exception(primary_pe
);
1558 list_add_tail(&pe
->list
, &pe_queue
);
1562 up_write(&snap
->lock
);
1569 * If this is the first time we're processing this chunk and
1570 * ref_count is now 1 it means all the pending exceptions
1571 * got completed while we were in the loop above, so it falls to
1572 * us here to remove the primary_pe and submit any origin_bios.
1575 if (first
&& atomic_dec_and_test(&primary_pe
->ref_count
)) {
1576 flush_bios(bio_list_get(&primary_pe
->origin_bios
));
1577 free_pending_exception(primary_pe
);
1578 /* If we got here, pe_queue is necessarily empty. */
1583 * Now that we have a complete pe list we can start the copying.
1585 list_for_each_entry_safe(pe
, next_pe
, &pe_queue
, list
)
1592 * Called on a write from the origin driver.
1594 static int do_origin(struct dm_dev
*origin
, struct bio
*bio
)
1597 int r
= DM_MAPIO_REMAPPED
;
1599 down_read(&_origins_lock
);
1600 o
= __lookup_origin(origin
->bdev
);
1602 r
= __origin_write(&o
->snapshots
, bio
);
1603 up_read(&_origins_lock
);
1609 * Origin: maps a linear range of a device, with hooks for snapshotting.
1613 * Construct an origin mapping: <dev_path>
1614 * The context for an origin is merely a 'struct dm_dev *'
1615 * pointing to the real device.
1617 static int origin_ctr(struct dm_target
*ti
, unsigned int argc
, char **argv
)
1623 ti
->error
= "origin: incorrect number of arguments";
1627 r
= dm_get_device(ti
, argv
[0], 0, ti
->len
,
1628 dm_table_get_mode(ti
->table
), &dev
);
1630 ti
->error
= "Cannot get target device";
1635 ti
->num_flush_requests
= 1;
1640 static void origin_dtr(struct dm_target
*ti
)
1642 struct dm_dev
*dev
= ti
->private;
1643 dm_put_device(ti
, dev
);
1646 static int origin_map(struct dm_target
*ti
, struct bio
*bio
,
1647 union map_info
*map_context
)
1649 struct dm_dev
*dev
= ti
->private;
1650 bio
->bi_bdev
= dev
->bdev
;
1652 if (unlikely(bio_empty_barrier(bio
)))
1653 return DM_MAPIO_REMAPPED
;
1655 /* Only tell snapshots if this is a write */
1656 return (bio_rw(bio
) == WRITE
) ? do_origin(dev
, bio
) : DM_MAPIO_REMAPPED
;
1660 * Set the target "split_io" field to the minimum of all the snapshots'
1663 static void origin_resume(struct dm_target
*ti
)
1665 struct dm_dev
*dev
= ti
->private;
1667 down_read(&_origins_lock
);
1669 ti
->split_io
= __minimum_chunk_size(__lookup_origin(dev
->bdev
));
1671 up_read(&_origins_lock
);
1674 static int origin_status(struct dm_target
*ti
, status_type_t type
, char *result
,
1675 unsigned int maxlen
)
1677 struct dm_dev
*dev
= ti
->private;
1680 case STATUSTYPE_INFO
:
1684 case STATUSTYPE_TABLE
:
1685 snprintf(result
, maxlen
, "%s", dev
->name
);
1692 static int origin_iterate_devices(struct dm_target
*ti
,
1693 iterate_devices_callout_fn fn
, void *data
)
1695 struct dm_dev
*dev
= ti
->private;
1697 return fn(ti
, dev
, 0, ti
->len
, data
);
1700 static struct target_type origin_target
= {
1701 .name
= "snapshot-origin",
1702 .version
= {1, 7, 0},
1703 .module
= THIS_MODULE
,
1707 .resume
= origin_resume
,
1708 .status
= origin_status
,
1709 .iterate_devices
= origin_iterate_devices
,
1712 static struct target_type snapshot_target
= {
1714 .version
= {1, 9, 0},
1715 .module
= THIS_MODULE
,
1716 .ctr
= snapshot_ctr
,
1717 .dtr
= snapshot_dtr
,
1718 .map
= snapshot_map
,
1719 .end_io
= snapshot_end_io
,
1720 .postsuspend
= snapshot_postsuspend
,
1721 .preresume
= snapshot_preresume
,
1722 .resume
= snapshot_resume
,
1723 .status
= snapshot_status
,
1724 .iterate_devices
= snapshot_iterate_devices
,
1727 static int __init
dm_snapshot_init(void)
1731 r
= dm_exception_store_init();
1733 DMERR("Failed to initialize exception stores");
1737 r
= dm_register_target(&snapshot_target
);
1739 DMERR("snapshot target register failed %d", r
);
1740 goto bad_register_snapshot_target
;
1743 r
= dm_register_target(&origin_target
);
1745 DMERR("Origin target register failed %d", r
);
1749 r
= init_origin_hash();
1751 DMERR("init_origin_hash failed.");
1755 exception_cache
= KMEM_CACHE(dm_exception
, 0);
1756 if (!exception_cache
) {
1757 DMERR("Couldn't create exception cache.");
1762 pending_cache
= KMEM_CACHE(dm_snap_pending_exception
, 0);
1763 if (!pending_cache
) {
1764 DMERR("Couldn't create pending cache.");
1769 tracked_chunk_cache
= KMEM_CACHE(dm_snap_tracked_chunk
, 0);
1770 if (!tracked_chunk_cache
) {
1771 DMERR("Couldn't create cache to track chunks in use.");
1776 ksnapd
= create_singlethread_workqueue("ksnapd");
1778 DMERR("Failed to create ksnapd workqueue.");
1780 goto bad_pending_pool
;
1786 kmem_cache_destroy(tracked_chunk_cache
);
1788 kmem_cache_destroy(pending_cache
);
1790 kmem_cache_destroy(exception_cache
);
1794 dm_unregister_target(&origin_target
);
1796 dm_unregister_target(&snapshot_target
);
1798 bad_register_snapshot_target
:
1799 dm_exception_store_exit();
1803 static void __exit
dm_snapshot_exit(void)
1805 destroy_workqueue(ksnapd
);
1807 dm_unregister_target(&snapshot_target
);
1808 dm_unregister_target(&origin_target
);
1811 kmem_cache_destroy(pending_cache
);
1812 kmem_cache_destroy(exception_cache
);
1813 kmem_cache_destroy(tracked_chunk_cache
);
1815 dm_exception_store_exit();
1819 module_init(dm_snapshot_init
);
1820 module_exit(dm_snapshot_exit
);
1822 MODULE_DESCRIPTION(DM_NAME
" snapshot target");
1823 MODULE_AUTHOR("Joe Thornber");
1824 MODULE_LICENSE("GPL");