blob: ab54f99b7c3b27cfd40a023bae56f9e0ed0b0f18 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * dm-snapshot.c
3 *
4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
5 *
6 * This file is released under the GPL.
7 */
8
9#include <linux/blkdev.h>
10#include <linux/config.h>
11#include <linux/ctype.h>
12#include <linux/device-mapper.h>
13#include <linux/fs.h>
14#include <linux/init.h>
15#include <linux/kdev_t.h>
16#include <linux/list.h>
17#include <linux/mempool.h>
18#include <linux/module.h>
19#include <linux/slab.h>
20#include <linux/vmalloc.h>
21
22#include "dm-snap.h"
23#include "dm-bio-list.h"
24#include "kcopyd.h"
25
26/*
27 * The percentage increment we will wake up users at
28 */
29#define WAKE_UP_PERCENT 5
30
31/*
32 * kcopyd priority of snapshot operations
33 */
34#define SNAPSHOT_COPY_PRIORITY 2
35
36/*
37 * Each snapshot reserves this many pages for io
38 */
39#define SNAPSHOT_PAGES 256
40
41struct pending_exception {
42 struct exception e;
43
44 /*
45 * Origin buffers waiting for this to complete are held
46 * in a bio list
47 */
48 struct bio_list origin_bios;
49 struct bio_list snapshot_bios;
50
51 /*
52 * Other pending_exceptions that are processing this
53 * chunk. When this list is empty, we know we can
54 * complete the origins.
55 */
56 struct list_head siblings;
57
58 /* Pointer back to snapshot context */
59 struct dm_snapshot *snap;
60
61 /*
62 * 1 indicates the exception has already been sent to
63 * kcopyd.
64 */
65 int started;
66};
67
68/*
69 * Hash table mapping origin volumes to lists of snapshots and
70 * a lock to protect it
71 */
72static kmem_cache_t *exception_cache;
73static kmem_cache_t *pending_cache;
74static mempool_t *pending_pool;
75
76/*
77 * One of these per registered origin, held in the snapshot_origins hash
78 */
79struct origin {
80 /* The origin device */
81 struct block_device *bdev;
82
83 struct list_head hash_list;
84
85 /* List of snapshots for this origin */
86 struct list_head snapshots;
87};
88
89/*
90 * Size of the hash table for origin volumes. If we make this
91 * the size of the minors list then it should be nearly perfect
92 */
93#define ORIGIN_HASH_SIZE 256
94#define ORIGIN_MASK 0xFF
95static struct list_head *_origins;
96static struct rw_semaphore _origins_lock;
97
98static int init_origin_hash(void)
99{
100 int i;
101
102 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
103 GFP_KERNEL);
104 if (!_origins) {
105 DMERR("Device mapper: Snapshot: unable to allocate memory");
106 return -ENOMEM;
107 }
108
109 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
110 INIT_LIST_HEAD(_origins + i);
111 init_rwsem(&_origins_lock);
112
113 return 0;
114}
115
116static void exit_origin_hash(void)
117{
118 kfree(_origins);
119}
120
121static inline unsigned int origin_hash(struct block_device *bdev)
122{
123 return bdev->bd_dev & ORIGIN_MASK;
124}
125
126static struct origin *__lookup_origin(struct block_device *origin)
127{
128 struct list_head *ol;
129 struct origin *o;
130
131 ol = &_origins[origin_hash(origin)];
132 list_for_each_entry (o, ol, hash_list)
133 if (bdev_equal(o->bdev, origin))
134 return o;
135
136 return NULL;
137}
138
139static void __insert_origin(struct origin *o)
140{
141 struct list_head *sl = &_origins[origin_hash(o->bdev)];
142 list_add_tail(&o->hash_list, sl);
143}
144
145/*
146 * Make a note of the snapshot and its origin so we can look it
147 * up when the origin has a write on it.
148 */
149static int register_snapshot(struct dm_snapshot *snap)
150{
151 struct origin *o;
152 struct block_device *bdev = snap->origin->bdev;
153
154 down_write(&_origins_lock);
155 o = __lookup_origin(bdev);
156
157 if (!o) {
158 /* New origin */
159 o = kmalloc(sizeof(*o), GFP_KERNEL);
160 if (!o) {
161 up_write(&_origins_lock);
162 return -ENOMEM;
163 }
164
165 /* Initialise the struct */
166 INIT_LIST_HEAD(&o->snapshots);
167 o->bdev = bdev;
168
169 __insert_origin(o);
170 }
171
172 list_add_tail(&snap->list, &o->snapshots);
173
174 up_write(&_origins_lock);
175 return 0;
176}
177
178static void unregister_snapshot(struct dm_snapshot *s)
179{
180 struct origin *o;
181
182 down_write(&_origins_lock);
183 o = __lookup_origin(s->origin->bdev);
184
185 list_del(&s->list);
186 if (list_empty(&o->snapshots)) {
187 list_del(&o->hash_list);
188 kfree(o);
189 }
190
191 up_write(&_origins_lock);
192}
193
194/*
195 * Implementation of the exception hash tables.
196 */
197static int init_exception_table(struct exception_table *et, uint32_t size)
198{
199 unsigned int i;
200
201 et->hash_mask = size - 1;
202 et->table = dm_vcalloc(size, sizeof(struct list_head));
203 if (!et->table)
204 return -ENOMEM;
205
206 for (i = 0; i < size; i++)
207 INIT_LIST_HEAD(et->table + i);
208
209 return 0;
210}
211
212static void exit_exception_table(struct exception_table *et, kmem_cache_t *mem)
213{
214 struct list_head *slot;
215 struct exception *ex, *next;
216 int i, size;
217
218 size = et->hash_mask + 1;
219 for (i = 0; i < size; i++) {
220 slot = et->table + i;
221
222 list_for_each_entry_safe (ex, next, slot, hash_list)
223 kmem_cache_free(mem, ex);
224 }
225
226 vfree(et->table);
227}
228
229static inline uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
230{
231 return chunk & et->hash_mask;
232}
233
234static void insert_exception(struct exception_table *eh, struct exception *e)
235{
236 struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)];
237 list_add(&e->hash_list, l);
238}
239
240static inline void remove_exception(struct exception *e)
241{
242 list_del(&e->hash_list);
243}
244
245/*
246 * Return the exception data for a sector, or NULL if not
247 * remapped.
248 */
249static struct exception *lookup_exception(struct exception_table *et,
250 chunk_t chunk)
251{
252 struct list_head *slot;
253 struct exception *e;
254
255 slot = &et->table[exception_hash(et, chunk)];
256 list_for_each_entry (e, slot, hash_list)
257 if (e->old_chunk == chunk)
258 return e;
259
260 return NULL;
261}
262
263static inline struct exception *alloc_exception(void)
264{
265 struct exception *e;
266
267 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
268 if (!e)
269 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
270
271 return e;
272}
273
274static inline void free_exception(struct exception *e)
275{
276 kmem_cache_free(exception_cache, e);
277}
278
279static inline struct pending_exception *alloc_pending_exception(void)
280{
281 return mempool_alloc(pending_pool, GFP_NOIO);
282}
283
284static inline void free_pending_exception(struct pending_exception *pe)
285{
286 mempool_free(pe, pending_pool);
287}
288
289int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
290{
291 struct exception *e;
292
293 e = alloc_exception();
294 if (!e)
295 return -ENOMEM;
296
297 e->old_chunk = old;
298 e->new_chunk = new;
299 insert_exception(&s->complete, e);
300 return 0;
301}
302
303/*
304 * Hard coded magic.
305 */
306static int calc_max_buckets(void)
307{
308 /* use a fixed size of 2MB */
309 unsigned long mem = 2 * 1024 * 1024;
310 mem /= sizeof(struct list_head);
311
312 return mem;
313}
314
315/*
316 * Rounds a number down to a power of 2.
317 */
318static inline uint32_t round_down(uint32_t n)
319{
320 while (n & (n - 1))
321 n &= (n - 1);
322 return n;
323}
324
325/*
326 * Allocate room for a suitable hash table.
327 */
328static int init_hash_tables(struct dm_snapshot *s)
329{
330 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
331
332 /*
333 * Calculate based on the size of the original volume or
334 * the COW volume...
335 */
336 cow_dev_size = get_dev_size(s->cow->bdev);
337 origin_dev_size = get_dev_size(s->origin->bdev);
338 max_buckets = calc_max_buckets();
339
340 hash_size = min(origin_dev_size, cow_dev_size) >> s->chunk_shift;
341 hash_size = min(hash_size, max_buckets);
342
343 /* Round it down to a power of 2 */
344 hash_size = round_down(hash_size);
345 if (init_exception_table(&s->complete, hash_size))
346 return -ENOMEM;
347
348 /*
349 * Allocate hash table for in-flight exceptions
350 * Make this smaller than the real hash table
351 */
352 hash_size >>= 3;
353 if (hash_size < 64)
354 hash_size = 64;
355
356 if (init_exception_table(&s->pending, hash_size)) {
357 exit_exception_table(&s->complete, exception_cache);
358 return -ENOMEM;
359 }
360
361 return 0;
362}
363
364/*
365 * Round a number up to the nearest 'size' boundary. size must
366 * be a power of 2.
367 */
368static inline ulong round_up(ulong n, ulong size)
369{
370 size--;
371 return (n + size) & ~size;
372}
373
374/*
375 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
376 */
377static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
378{
379 struct dm_snapshot *s;
380 unsigned long chunk_size;
381 int r = -EINVAL;
382 char persistent;
383 char *origin_path;
384 char *cow_path;
385 char *value;
386 int blocksize;
387
388 if (argc < 4) {
389 ti->error = "dm-snapshot: requires exactly 4 arguments";
390 r = -EINVAL;
391 goto bad1;
392 }
393
394 origin_path = argv[0];
395 cow_path = argv[1];
396 persistent = toupper(*argv[2]);
397
398 if (persistent != 'P' && persistent != 'N') {
399 ti->error = "Persistent flag is not P or N";
400 r = -EINVAL;
401 goto bad1;
402 }
403
404 chunk_size = simple_strtoul(argv[3], &value, 10);
405 if (chunk_size == 0 || value == NULL) {
406 ti->error = "Invalid chunk size";
407 r = -EINVAL;
408 goto bad1;
409 }
410
411 s = kmalloc(sizeof(*s), GFP_KERNEL);
412 if (s == NULL) {
413 ti->error = "Cannot allocate snapshot context private "
414 "structure";
415 r = -ENOMEM;
416 goto bad1;
417 }
418
419 r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
420 if (r) {
421 ti->error = "Cannot get origin device";
422 goto bad2;
423 }
424
425 r = dm_get_device(ti, cow_path, 0, 0,
426 FMODE_READ | FMODE_WRITE, &s->cow);
427 if (r) {
428 dm_put_device(ti, s->origin);
429 ti->error = "Cannot get COW device";
430 goto bad2;
431 }
432
433 /*
434 * Chunk size must be multiple of page size. Silently
435 * round up if it's not.
436 */
437 chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
438
439 /* Validate the chunk size against the device block size */
440 blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
441 if (chunk_size % (blocksize >> 9)) {
442 ti->error = "Chunk size is not a multiple of device blocksize";
443 r = -EINVAL;
444 goto bad3;
445 }
446
447 /* Check chunk_size is a power of 2 */
448 if (chunk_size & (chunk_size - 1)) {
449 ti->error = "Chunk size is not a power of 2";
450 r = -EINVAL;
451 goto bad3;
452 }
453
454 s->chunk_size = chunk_size;
455 s->chunk_mask = chunk_size - 1;
456 s->type = persistent;
457 s->chunk_shift = ffs(chunk_size) - 1;
458
459 s->valid = 1;
460 s->have_metadata = 0;
461 s->last_percent = 0;
462 init_rwsem(&s->lock);
463 s->table = ti->table;
464
465 /* Allocate hash table for COW data */
466 if (init_hash_tables(s)) {
467 ti->error = "Unable to allocate hash table space";
468 r = -ENOMEM;
469 goto bad3;
470 }
471
472 /*
473 * Check the persistent flag - done here because we need the iobuf
474 * to check the LV header
475 */
476 s->store.snap = s;
477
478 if (persistent == 'P')
479 r = dm_create_persistent(&s->store, chunk_size);
480 else
481 r = dm_create_transient(&s->store, s, blocksize);
482
483 if (r) {
484 ti->error = "Couldn't create exception store";
485 r = -EINVAL;
486 goto bad4;
487 }
488
489 r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
490 if (r) {
491 ti->error = "Could not create kcopyd client";
492 goto bad5;
493 }
494
495 /* Add snapshot to the list of snapshots for this origin */
496 if (register_snapshot(s)) {
497 r = -EINVAL;
498 ti->error = "Cannot register snapshot origin";
499 goto bad6;
500 }
501
502 ti->private = s;
503 ti->split_io = chunk_size;
504
505 return 0;
506
507 bad6:
508 kcopyd_client_destroy(s->kcopyd_client);
509
510 bad5:
511 s->store.destroy(&s->store);
512
513 bad4:
514 exit_exception_table(&s->pending, pending_cache);
515 exit_exception_table(&s->complete, exception_cache);
516
517 bad3:
518 dm_put_device(ti, s->cow);
519 dm_put_device(ti, s->origin);
520
521 bad2:
522 kfree(s);
523
524 bad1:
525 return r;
526}
527
528static void snapshot_dtr(struct dm_target *ti)
529{
530 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
531
532 unregister_snapshot(s);
533
534 exit_exception_table(&s->pending, pending_cache);
535 exit_exception_table(&s->complete, exception_cache);
536
537 /* Deallocate memory used */
538 s->store.destroy(&s->store);
539
540 dm_put_device(ti, s->origin);
541 dm_put_device(ti, s->cow);
542 kcopyd_client_destroy(s->kcopyd_client);
543 kfree(s);
544}
545
546/*
547 * Flush a list of buffers.
548 */
549static void flush_bios(struct bio *bio)
550{
551 struct bio *n;
552
553 while (bio) {
554 n = bio->bi_next;
555 bio->bi_next = NULL;
556 generic_make_request(bio);
557 bio = n;
558 }
559}
560
561/*
562 * Error a list of buffers.
563 */
564static void error_bios(struct bio *bio)
565{
566 struct bio *n;
567
568 while (bio) {
569 n = bio->bi_next;
570 bio->bi_next = NULL;
571 bio_io_error(bio, bio->bi_size);
572 bio = n;
573 }
574}
575
576static struct bio *__flush_bios(struct pending_exception *pe)
577{
578 struct pending_exception *sibling;
579
580 if (list_empty(&pe->siblings))
581 return bio_list_get(&pe->origin_bios);
582
583 sibling = list_entry(pe->siblings.next,
584 struct pending_exception, siblings);
585
586 list_del(&pe->siblings);
587
588 /* This is fine as long as kcopyd is single-threaded. If kcopyd
589 * becomes multi-threaded, we'll need some locking here.
590 */
591 bio_list_merge(&sibling->origin_bios, &pe->origin_bios);
592
593 return NULL;
594}
595
596static void pending_complete(struct pending_exception *pe, int success)
597{
598 struct exception *e;
599 struct dm_snapshot *s = pe->snap;
600 struct bio *flush = NULL;
601
602 if (success) {
603 e = alloc_exception();
604 if (!e) {
605 DMWARN("Unable to allocate exception.");
606 down_write(&s->lock);
607 s->store.drop_snapshot(&s->store);
608 s->valid = 0;
609 flush = __flush_bios(pe);
610 up_write(&s->lock);
611
612 error_bios(bio_list_get(&pe->snapshot_bios));
613 goto out;
614 }
615 *e = pe->e;
616
617 /*
618 * Add a proper exception, and remove the
619 * in-flight exception from the list.
620 */
621 down_write(&s->lock);
622 insert_exception(&s->complete, e);
623 remove_exception(&pe->e);
624 flush = __flush_bios(pe);
625
626 /* Submit any pending write bios */
627 up_write(&s->lock);
628
629 flush_bios(bio_list_get(&pe->snapshot_bios));
630 } else {
631 /* Read/write error - snapshot is unusable */
632 down_write(&s->lock);
633 if (s->valid)
634 DMERR("Error reading/writing snapshot");
635 s->store.drop_snapshot(&s->store);
636 s->valid = 0;
637 remove_exception(&pe->e);
638 flush = __flush_bios(pe);
639 up_write(&s->lock);
640
641 error_bios(bio_list_get(&pe->snapshot_bios));
642
643 dm_table_event(s->table);
644 }
645
646 out:
647 free_pending_exception(pe);
648
649 if (flush)
650 flush_bios(flush);
651}
652
653static void commit_callback(void *context, int success)
654{
655 struct pending_exception *pe = (struct pending_exception *) context;
656 pending_complete(pe, success);
657}
658
659/*
660 * Called when the copy I/O has finished. kcopyd actually runs
661 * this code so don't block.
662 */
663static void copy_callback(int read_err, unsigned int write_err, void *context)
664{
665 struct pending_exception *pe = (struct pending_exception *) context;
666 struct dm_snapshot *s = pe->snap;
667
668 if (read_err || write_err)
669 pending_complete(pe, 0);
670
671 else
672 /* Update the metadata if we are persistent */
673 s->store.commit_exception(&s->store, &pe->e, commit_callback,
674 pe);
675}
676
677/*
678 * Dispatches the copy operation to kcopyd.
679 */
680static inline void start_copy(struct pending_exception *pe)
681{
682 struct dm_snapshot *s = pe->snap;
683 struct io_region src, dest;
684 struct block_device *bdev = s->origin->bdev;
685 sector_t dev_size;
686
687 dev_size = get_dev_size(bdev);
688
689 src.bdev = bdev;
690 src.sector = chunk_to_sector(s, pe->e.old_chunk);
691 src.count = min(s->chunk_size, dev_size - src.sector);
692
693 dest.bdev = s->cow->bdev;
694 dest.sector = chunk_to_sector(s, pe->e.new_chunk);
695 dest.count = src.count;
696
697 /* Hand over to kcopyd */
698 kcopyd_copy(s->kcopyd_client,
699 &src, 1, &dest, 0, copy_callback, pe);
700}
701
702/*
703 * Looks to see if this snapshot already has a pending exception
704 * for this chunk, otherwise it allocates a new one and inserts
705 * it into the pending table.
706 *
707 * NOTE: a write lock must be held on snap->lock before calling
708 * this.
709 */
710static struct pending_exception *
711__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
712{
713 struct exception *e;
714 struct pending_exception *pe;
715 chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
716
717 /*
718 * Is there a pending exception for this already ?
719 */
720 e = lookup_exception(&s->pending, chunk);
721 if (e) {
722 /* cast the exception to a pending exception */
723 pe = container_of(e, struct pending_exception, e);
724
725 } else {
726 /*
727 * Create a new pending exception, we don't want
728 * to hold the lock while we do this.
729 */
730 up_write(&s->lock);
731 pe = alloc_pending_exception();
732 down_write(&s->lock);
733
734 e = lookup_exception(&s->pending, chunk);
735 if (e) {
736 free_pending_exception(pe);
737 pe = container_of(e, struct pending_exception, e);
738 } else {
739 pe->e.old_chunk = chunk;
740 bio_list_init(&pe->origin_bios);
741 bio_list_init(&pe->snapshot_bios);
742 INIT_LIST_HEAD(&pe->siblings);
743 pe->snap = s;
744 pe->started = 0;
745
746 if (s->store.prepare_exception(&s->store, &pe->e)) {
747 free_pending_exception(pe);
748 s->valid = 0;
749 return NULL;
750 }
751
752 insert_exception(&s->pending, &pe->e);
753 }
754 }
755
756 return pe;
757}
758
759static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
760 struct bio *bio)
761{
762 bio->bi_bdev = s->cow->bdev;
763 bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
764 (bio->bi_sector & s->chunk_mask);
765}
766
767static int snapshot_map(struct dm_target *ti, struct bio *bio,
768 union map_info *map_context)
769{
770 struct exception *e;
771 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
772 int r = 1;
773 chunk_t chunk;
774 struct pending_exception *pe;
775
776 chunk = sector_to_chunk(s, bio->bi_sector);
777
778 /* Full snapshots are not usable */
779 if (!s->valid)
Alasdair G Kergonf6a80ea2005-07-12 15:53:01 -0700780 return -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781
782 /*
783 * Write to snapshot - higher level takes care of RW/RO
784 * flags so we should only get this if we are
785 * writeable.
786 */
787 if (bio_rw(bio) == WRITE) {
788
789 /* FIXME: should only take write lock if we need
790 * to copy an exception */
791 down_write(&s->lock);
792
793 /* If the block is already remapped - use that, else remap it */
794 e = lookup_exception(&s->complete, chunk);
795 if (e) {
796 remap_exception(s, e, bio);
797 up_write(&s->lock);
798
799 } else {
800 pe = __find_pending_exception(s, bio);
801
802 if (!pe) {
803 if (s->store.drop_snapshot)
804 s->store.drop_snapshot(&s->store);
805 s->valid = 0;
806 r = -EIO;
807 up_write(&s->lock);
808 } else {
809 remap_exception(s, &pe->e, bio);
810 bio_list_add(&pe->snapshot_bios, bio);
811
812 if (!pe->started) {
813 /* this is protected by snap->lock */
814 pe->started = 1;
815 up_write(&s->lock);
816 start_copy(pe);
817 } else
818 up_write(&s->lock);
819 r = 0;
820 }
821 }
822
823 } else {
824 /*
825 * FIXME: this read path scares me because we
826 * always use the origin when we have a pending
827 * exception. However I can't think of a
828 * situation where this is wrong - ejt.
829 */
830
831 /* Do reads */
832 down_read(&s->lock);
833
834 /* See if it it has been remapped */
835 e = lookup_exception(&s->complete, chunk);
836 if (e)
837 remap_exception(s, e, bio);
838 else
839 bio->bi_bdev = s->origin->bdev;
840
841 up_read(&s->lock);
842 }
843
844 return r;
845}
846
847static void snapshot_resume(struct dm_target *ti)
848{
849 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
850
851 if (s->have_metadata)
852 return;
853
854 if (s->store.read_metadata(&s->store)) {
855 down_write(&s->lock);
856 s->valid = 0;
857 up_write(&s->lock);
858 }
859
860 s->have_metadata = 1;
861}
862
863static int snapshot_status(struct dm_target *ti, status_type_t type,
864 char *result, unsigned int maxlen)
865{
866 struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
867
868 switch (type) {
869 case STATUSTYPE_INFO:
870 if (!snap->valid)
871 snprintf(result, maxlen, "Invalid");
872 else {
873 if (snap->store.fraction_full) {
874 sector_t numerator, denominator;
875 snap->store.fraction_full(&snap->store,
876 &numerator,
877 &denominator);
878 snprintf(result, maxlen,
879 SECTOR_FORMAT "/" SECTOR_FORMAT,
880 numerator, denominator);
881 }
882 else
883 snprintf(result, maxlen, "Unknown");
884 }
885 break;
886
887 case STATUSTYPE_TABLE:
888 /*
889 * kdevname returns a static pointer so we need
890 * to make private copies if the output is to
891 * make sense.
892 */
893 snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT,
894 snap->origin->name, snap->cow->name,
895 snap->type, snap->chunk_size);
896 break;
897 }
898
899 return 0;
900}
901
902/*-----------------------------------------------------------------
903 * Origin methods
904 *---------------------------------------------------------------*/
905static void list_merge(struct list_head *l1, struct list_head *l2)
906{
907 struct list_head *l1_n, *l2_p;
908
909 l1_n = l1->next;
910 l2_p = l2->prev;
911
912 l1->next = l2;
913 l2->prev = l1;
914
915 l2_p->next = l1_n;
916 l1_n->prev = l2_p;
917}
918
919static int __origin_write(struct list_head *snapshots, struct bio *bio)
920{
921 int r = 1, first = 1;
922 struct dm_snapshot *snap;
923 struct exception *e;
924 struct pending_exception *pe, *last = NULL;
925 chunk_t chunk;
926
927 /* Do all the snapshots on this origin */
928 list_for_each_entry (snap, snapshots, list) {
929
930 /* Only deal with valid snapshots */
931 if (!snap->valid)
932 continue;
933
Alasdair G Kergond5e404c2005-07-12 15:53:05 -0700934 /* Nothing to do if writing beyond end of snapshot */
935 if (bio->bi_sector >= dm_table_get_size(snap->table))
936 continue;
937
Linus Torvalds1da177e2005-04-16 15:20:36 -0700938 down_write(&snap->lock);
939
940 /*
941 * Remember, different snapshots can have
942 * different chunk sizes.
943 */
944 chunk = sector_to_chunk(snap, bio->bi_sector);
945
946 /*
947 * Check exception table to see if block
948 * is already remapped in this snapshot
949 * and trigger an exception if not.
950 */
951 e = lookup_exception(&snap->complete, chunk);
952 if (!e) {
953 pe = __find_pending_exception(snap, bio);
954 if (!pe) {
955 snap->store.drop_snapshot(&snap->store);
956 snap->valid = 0;
957
958 } else {
959 if (last)
960 list_merge(&pe->siblings,
961 &last->siblings);
962
963 last = pe;
964 r = 0;
965 }
966 }
967
968 up_write(&snap->lock);
969 }
970
971 /*
972 * Now that we have a complete pe list we can start the copying.
973 */
974 if (last) {
975 pe = last;
976 do {
977 down_write(&pe->snap->lock);
978 if (first)
979 bio_list_add(&pe->origin_bios, bio);
980 if (!pe->started) {
981 pe->started = 1;
982 up_write(&pe->snap->lock);
983 start_copy(pe);
984 } else
985 up_write(&pe->snap->lock);
986 first = 0;
987 pe = list_entry(pe->siblings.next,
988 struct pending_exception, siblings);
989
990 } while (pe != last);
991 }
992
993 return r;
994}
995
996/*
997 * Called on a write from the origin driver.
998 */
999static int do_origin(struct dm_dev *origin, struct bio *bio)
1000{
1001 struct origin *o;
1002 int r = 1;
1003
1004 down_read(&_origins_lock);
1005 o = __lookup_origin(origin->bdev);
1006 if (o)
1007 r = __origin_write(&o->snapshots, bio);
1008 up_read(&_origins_lock);
1009
1010 return r;
1011}
1012
1013/*
1014 * Origin: maps a linear range of a device, with hooks for snapshotting.
1015 */
1016
1017/*
1018 * Construct an origin mapping: <dev_path>
1019 * The context for an origin is merely a 'struct dm_dev *'
1020 * pointing to the real device.
1021 */
1022static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1023{
1024 int r;
1025 struct dm_dev *dev;
1026
1027 if (argc != 1) {
1028 ti->error = "dm-origin: incorrect number of arguments";
1029 return -EINVAL;
1030 }
1031
1032 r = dm_get_device(ti, argv[0], 0, ti->len,
1033 dm_table_get_mode(ti->table), &dev);
1034 if (r) {
1035 ti->error = "Cannot get target device";
1036 return r;
1037 }
1038
1039 ti->private = dev;
1040 return 0;
1041}
1042
1043static void origin_dtr(struct dm_target *ti)
1044{
1045 struct dm_dev *dev = (struct dm_dev *) ti->private;
1046 dm_put_device(ti, dev);
1047}
1048
1049static int origin_map(struct dm_target *ti, struct bio *bio,
1050 union map_info *map_context)
1051{
1052 struct dm_dev *dev = (struct dm_dev *) ti->private;
1053 bio->bi_bdev = dev->bdev;
1054
1055 /* Only tell snapshots if this is a write */
1056 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
1057}
1058
1059#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
1060
1061/*
1062 * Set the target "split_io" field to the minimum of all the snapshots'
1063 * chunk sizes.
1064 */
1065static void origin_resume(struct dm_target *ti)
1066{
1067 struct dm_dev *dev = (struct dm_dev *) ti->private;
1068 struct dm_snapshot *snap;
1069 struct origin *o;
1070 chunk_t chunk_size = 0;
1071
1072 down_read(&_origins_lock);
1073 o = __lookup_origin(dev->bdev);
1074 if (o)
1075 list_for_each_entry (snap, &o->snapshots, list)
1076 chunk_size = min_not_zero(chunk_size, snap->chunk_size);
1077 up_read(&_origins_lock);
1078
1079 ti->split_io = chunk_size;
1080}
1081
1082static int origin_status(struct dm_target *ti, status_type_t type, char *result,
1083 unsigned int maxlen)
1084{
1085 struct dm_dev *dev = (struct dm_dev *) ti->private;
1086
1087 switch (type) {
1088 case STATUSTYPE_INFO:
1089 result[0] = '\0';
1090 break;
1091
1092 case STATUSTYPE_TABLE:
1093 snprintf(result, maxlen, "%s", dev->name);
1094 break;
1095 }
1096
1097 return 0;
1098}
1099
1100static struct target_type origin_target = {
1101 .name = "snapshot-origin",
1102 .version = {1, 0, 1},
1103 .module = THIS_MODULE,
1104 .ctr = origin_ctr,
1105 .dtr = origin_dtr,
1106 .map = origin_map,
1107 .resume = origin_resume,
1108 .status = origin_status,
1109};
1110
1111static struct target_type snapshot_target = {
1112 .name = "snapshot",
1113 .version = {1, 0, 1},
1114 .module = THIS_MODULE,
1115 .ctr = snapshot_ctr,
1116 .dtr = snapshot_dtr,
1117 .map = snapshot_map,
1118 .resume = snapshot_resume,
1119 .status = snapshot_status,
1120};
1121
1122static int __init dm_snapshot_init(void)
1123{
1124 int r;
1125
1126 r = dm_register_target(&snapshot_target);
1127 if (r) {
1128 DMERR("snapshot target register failed %d", r);
1129 return r;
1130 }
1131
1132 r = dm_register_target(&origin_target);
1133 if (r < 0) {
1134 DMERR("Device mapper: Origin: register failed %d\n", r);
1135 goto bad1;
1136 }
1137
1138 r = init_origin_hash();
1139 if (r) {
1140 DMERR("init_origin_hash failed.");
1141 goto bad2;
1142 }
1143
1144 exception_cache = kmem_cache_create("dm-snapshot-ex",
1145 sizeof(struct exception),
1146 __alignof__(struct exception),
1147 0, NULL, NULL);
1148 if (!exception_cache) {
1149 DMERR("Couldn't create exception cache.");
1150 r = -ENOMEM;
1151 goto bad3;
1152 }
1153
1154 pending_cache =
1155 kmem_cache_create("dm-snapshot-in",
1156 sizeof(struct pending_exception),
1157 __alignof__(struct pending_exception),
1158 0, NULL, NULL);
1159 if (!pending_cache) {
1160 DMERR("Couldn't create pending cache.");
1161 r = -ENOMEM;
1162 goto bad4;
1163 }
1164
1165 pending_pool = mempool_create(128, mempool_alloc_slab,
1166 mempool_free_slab, pending_cache);
1167 if (!pending_pool) {
1168 DMERR("Couldn't create pending pool.");
1169 r = -ENOMEM;
1170 goto bad5;
1171 }
1172
1173 return 0;
1174
1175 bad5:
1176 kmem_cache_destroy(pending_cache);
1177 bad4:
1178 kmem_cache_destroy(exception_cache);
1179 bad3:
1180 exit_origin_hash();
1181 bad2:
1182 dm_unregister_target(&origin_target);
1183 bad1:
1184 dm_unregister_target(&snapshot_target);
1185 return r;
1186}
1187
1188static void __exit dm_snapshot_exit(void)
1189{
1190 int r;
1191
1192 r = dm_unregister_target(&snapshot_target);
1193 if (r)
1194 DMERR("snapshot unregister failed %d", r);
1195
1196 r = dm_unregister_target(&origin_target);
1197 if (r)
1198 DMERR("origin unregister failed %d", r);
1199
1200 exit_origin_hash();
1201 mempool_destroy(pending_pool);
1202 kmem_cache_destroy(pending_cache);
1203 kmem_cache_destroy(exception_cache);
1204}
1205
1206/* Module hooks */
1207module_init(dm_snapshot_init);
1208module_exit(dm_snapshot_exit);
1209
1210MODULE_DESCRIPTION(DM_NAME " snapshot target");
1211MODULE_AUTHOR("Joe Thornber");
1212MODULE_LICENSE("GPL");