blob: f3759dd7828e585ed81b0819e9908fbf546da543 [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
Alasdair G Kergon2d38fe22006-01-06 00:20:02 -0800374static void read_snapshot_metadata(struct dm_snapshot *s)
375{
Alasdair G Kergon2d38fe22006-01-06 00:20:02 -0800376 if (s->store.read_metadata(&s->store)) {
377 down_write(&s->lock);
378 s->valid = 0;
379 up_write(&s->lock);
380 }
Alasdair G Kergon2d38fe22006-01-06 00:20:02 -0800381}
382
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383/*
384 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
385 */
386static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
387{
388 struct dm_snapshot *s;
389 unsigned long chunk_size;
390 int r = -EINVAL;
391 char persistent;
392 char *origin_path;
393 char *cow_path;
394 char *value;
395 int blocksize;
396
397 if (argc < 4) {
398 ti->error = "dm-snapshot: requires exactly 4 arguments";
399 r = -EINVAL;
400 goto bad1;
401 }
402
403 origin_path = argv[0];
404 cow_path = argv[1];
405 persistent = toupper(*argv[2]);
406
407 if (persistent != 'P' && persistent != 'N') {
408 ti->error = "Persistent flag is not P or N";
409 r = -EINVAL;
410 goto bad1;
411 }
412
413 chunk_size = simple_strtoul(argv[3], &value, 10);
414 if (chunk_size == 0 || value == NULL) {
415 ti->error = "Invalid chunk size";
416 r = -EINVAL;
417 goto bad1;
418 }
419
420 s = kmalloc(sizeof(*s), GFP_KERNEL);
421 if (s == NULL) {
422 ti->error = "Cannot allocate snapshot context private "
423 "structure";
424 r = -ENOMEM;
425 goto bad1;
426 }
427
428 r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
429 if (r) {
430 ti->error = "Cannot get origin device";
431 goto bad2;
432 }
433
434 r = dm_get_device(ti, cow_path, 0, 0,
435 FMODE_READ | FMODE_WRITE, &s->cow);
436 if (r) {
437 dm_put_device(ti, s->origin);
438 ti->error = "Cannot get COW device";
439 goto bad2;
440 }
441
442 /*
443 * Chunk size must be multiple of page size. Silently
444 * round up if it's not.
445 */
446 chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
447
448 /* Validate the chunk size against the device block size */
449 blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
450 if (chunk_size % (blocksize >> 9)) {
451 ti->error = "Chunk size is not a multiple of device blocksize";
452 r = -EINVAL;
453 goto bad3;
454 }
455
456 /* Check chunk_size is a power of 2 */
457 if (chunk_size & (chunk_size - 1)) {
458 ti->error = "Chunk size is not a power of 2";
459 r = -EINVAL;
460 goto bad3;
461 }
462
463 s->chunk_size = chunk_size;
464 s->chunk_mask = chunk_size - 1;
465 s->type = persistent;
466 s->chunk_shift = ffs(chunk_size) - 1;
467
468 s->valid = 1;
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800469 s->active = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470 s->last_percent = 0;
471 init_rwsem(&s->lock);
472 s->table = ti->table;
473
474 /* Allocate hash table for COW data */
475 if (init_hash_tables(s)) {
476 ti->error = "Unable to allocate hash table space";
477 r = -ENOMEM;
478 goto bad3;
479 }
480
481 /*
482 * Check the persistent flag - done here because we need the iobuf
483 * to check the LV header
484 */
485 s->store.snap = s;
486
487 if (persistent == 'P')
488 r = dm_create_persistent(&s->store, chunk_size);
489 else
490 r = dm_create_transient(&s->store, s, blocksize);
491
492 if (r) {
493 ti->error = "Couldn't create exception store";
494 r = -EINVAL;
495 goto bad4;
496 }
497
498 r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
499 if (r) {
500 ti->error = "Could not create kcopyd client";
501 goto bad5;
502 }
503
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800504 /* Metadata must only be loaded into one table at once */
505 read_snapshot_metadata(s);
506
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507 /* Add snapshot to the list of snapshots for this origin */
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800508 /* Exceptions aren't triggered till snapshot_resume() is called */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 if (register_snapshot(s)) {
510 r = -EINVAL;
511 ti->error = "Cannot register snapshot origin";
512 goto bad6;
513 }
514
515 ti->private = s;
516 ti->split_io = chunk_size;
517
518 return 0;
519
520 bad6:
521 kcopyd_client_destroy(s->kcopyd_client);
522
523 bad5:
524 s->store.destroy(&s->store);
525
526 bad4:
527 exit_exception_table(&s->pending, pending_cache);
528 exit_exception_table(&s->complete, exception_cache);
529
530 bad3:
531 dm_put_device(ti, s->cow);
532 dm_put_device(ti, s->origin);
533
534 bad2:
535 kfree(s);
536
537 bad1:
538 return r;
539}
540
541static void snapshot_dtr(struct dm_target *ti)
542{
543 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
544
545 unregister_snapshot(s);
546
547 exit_exception_table(&s->pending, pending_cache);
548 exit_exception_table(&s->complete, exception_cache);
549
550 /* Deallocate memory used */
551 s->store.destroy(&s->store);
552
553 dm_put_device(ti, s->origin);
554 dm_put_device(ti, s->cow);
555 kcopyd_client_destroy(s->kcopyd_client);
556 kfree(s);
557}
558
559/*
560 * Flush a list of buffers.
561 */
562static void flush_bios(struct bio *bio)
563{
564 struct bio *n;
565
566 while (bio) {
567 n = bio->bi_next;
568 bio->bi_next = NULL;
569 generic_make_request(bio);
570 bio = n;
571 }
572}
573
574/*
575 * Error a list of buffers.
576 */
577static void error_bios(struct bio *bio)
578{
579 struct bio *n;
580
581 while (bio) {
582 n = bio->bi_next;
583 bio->bi_next = NULL;
584 bio_io_error(bio, bio->bi_size);
585 bio = n;
586 }
587}
588
589static struct bio *__flush_bios(struct pending_exception *pe)
590{
591 struct pending_exception *sibling;
592
593 if (list_empty(&pe->siblings))
594 return bio_list_get(&pe->origin_bios);
595
596 sibling = list_entry(pe->siblings.next,
597 struct pending_exception, siblings);
598
599 list_del(&pe->siblings);
600
601 /* This is fine as long as kcopyd is single-threaded. If kcopyd
602 * becomes multi-threaded, we'll need some locking here.
603 */
604 bio_list_merge(&sibling->origin_bios, &pe->origin_bios);
605
606 return NULL;
607}
608
609static void pending_complete(struct pending_exception *pe, int success)
610{
611 struct exception *e;
612 struct dm_snapshot *s = pe->snap;
613 struct bio *flush = NULL;
614
615 if (success) {
616 e = alloc_exception();
617 if (!e) {
618 DMWARN("Unable to allocate exception.");
619 down_write(&s->lock);
620 s->store.drop_snapshot(&s->store);
621 s->valid = 0;
622 flush = __flush_bios(pe);
623 up_write(&s->lock);
624
625 error_bios(bio_list_get(&pe->snapshot_bios));
626 goto out;
627 }
628 *e = pe->e;
629
630 /*
631 * Add a proper exception, and remove the
632 * in-flight exception from the list.
633 */
634 down_write(&s->lock);
635 insert_exception(&s->complete, e);
636 remove_exception(&pe->e);
637 flush = __flush_bios(pe);
638
639 /* Submit any pending write bios */
640 up_write(&s->lock);
641
642 flush_bios(bio_list_get(&pe->snapshot_bios));
643 } else {
644 /* Read/write error - snapshot is unusable */
645 down_write(&s->lock);
646 if (s->valid)
647 DMERR("Error reading/writing snapshot");
648 s->store.drop_snapshot(&s->store);
649 s->valid = 0;
650 remove_exception(&pe->e);
651 flush = __flush_bios(pe);
652 up_write(&s->lock);
653
654 error_bios(bio_list_get(&pe->snapshot_bios));
655
656 dm_table_event(s->table);
657 }
658
659 out:
660 free_pending_exception(pe);
661
662 if (flush)
663 flush_bios(flush);
664}
665
666static void commit_callback(void *context, int success)
667{
668 struct pending_exception *pe = (struct pending_exception *) context;
669 pending_complete(pe, success);
670}
671
672/*
673 * Called when the copy I/O has finished. kcopyd actually runs
674 * this code so don't block.
675 */
676static void copy_callback(int read_err, unsigned int write_err, void *context)
677{
678 struct pending_exception *pe = (struct pending_exception *) context;
679 struct dm_snapshot *s = pe->snap;
680
681 if (read_err || write_err)
682 pending_complete(pe, 0);
683
684 else
685 /* Update the metadata if we are persistent */
686 s->store.commit_exception(&s->store, &pe->e, commit_callback,
687 pe);
688}
689
690/*
691 * Dispatches the copy operation to kcopyd.
692 */
Arjan van de Ven858119e2006-01-14 13:20:43 -0800693static void start_copy(struct pending_exception *pe)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694{
695 struct dm_snapshot *s = pe->snap;
696 struct io_region src, dest;
697 struct block_device *bdev = s->origin->bdev;
698 sector_t dev_size;
699
700 dev_size = get_dev_size(bdev);
701
702 src.bdev = bdev;
703 src.sector = chunk_to_sector(s, pe->e.old_chunk);
704 src.count = min(s->chunk_size, dev_size - src.sector);
705
706 dest.bdev = s->cow->bdev;
707 dest.sector = chunk_to_sector(s, pe->e.new_chunk);
708 dest.count = src.count;
709
710 /* Hand over to kcopyd */
711 kcopyd_copy(s->kcopyd_client,
712 &src, 1, &dest, 0, copy_callback, pe);
713}
714
715/*
716 * Looks to see if this snapshot already has a pending exception
717 * for this chunk, otherwise it allocates a new one and inserts
718 * it into the pending table.
719 *
720 * NOTE: a write lock must be held on snap->lock before calling
721 * this.
722 */
723static struct pending_exception *
724__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
725{
726 struct exception *e;
727 struct pending_exception *pe;
728 chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
729
730 /*
731 * Is there a pending exception for this already ?
732 */
733 e = lookup_exception(&s->pending, chunk);
734 if (e) {
735 /* cast the exception to a pending exception */
736 pe = container_of(e, struct pending_exception, e);
737
738 } else {
739 /*
740 * Create a new pending exception, we don't want
741 * to hold the lock while we do this.
742 */
743 up_write(&s->lock);
744 pe = alloc_pending_exception();
745 down_write(&s->lock);
746
747 e = lookup_exception(&s->pending, chunk);
748 if (e) {
749 free_pending_exception(pe);
750 pe = container_of(e, struct pending_exception, e);
751 } else {
752 pe->e.old_chunk = chunk;
753 bio_list_init(&pe->origin_bios);
754 bio_list_init(&pe->snapshot_bios);
755 INIT_LIST_HEAD(&pe->siblings);
756 pe->snap = s;
757 pe->started = 0;
758
759 if (s->store.prepare_exception(&s->store, &pe->e)) {
760 free_pending_exception(pe);
761 s->valid = 0;
762 return NULL;
763 }
764
765 insert_exception(&s->pending, &pe->e);
766 }
767 }
768
769 return pe;
770}
771
772static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
773 struct bio *bio)
774{
775 bio->bi_bdev = s->cow->bdev;
776 bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
777 (bio->bi_sector & s->chunk_mask);
778}
779
780static int snapshot_map(struct dm_target *ti, struct bio *bio,
781 union map_info *map_context)
782{
783 struct exception *e;
784 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
785 int r = 1;
786 chunk_t chunk;
787 struct pending_exception *pe;
788
789 chunk = sector_to_chunk(s, bio->bi_sector);
790
791 /* Full snapshots are not usable */
792 if (!s->valid)
Alasdair G Kergonf6a80ea2005-07-12 15:53:01 -0700793 return -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700794
Alasdair G Kergon4aac0a62006-02-01 03:04:55 -0800795 if (unlikely(bio_barrier(bio)))
796 return -EOPNOTSUPP;
797
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 /*
799 * Write to snapshot - higher level takes care of RW/RO
800 * flags so we should only get this if we are
801 * writeable.
802 */
803 if (bio_rw(bio) == WRITE) {
804
805 /* FIXME: should only take write lock if we need
806 * to copy an exception */
807 down_write(&s->lock);
808
809 /* If the block is already remapped - use that, else remap it */
810 e = lookup_exception(&s->complete, chunk);
811 if (e) {
812 remap_exception(s, e, bio);
813 up_write(&s->lock);
814
815 } else {
816 pe = __find_pending_exception(s, bio);
817
818 if (!pe) {
819 if (s->store.drop_snapshot)
820 s->store.drop_snapshot(&s->store);
821 s->valid = 0;
822 r = -EIO;
823 up_write(&s->lock);
824 } else {
825 remap_exception(s, &pe->e, bio);
826 bio_list_add(&pe->snapshot_bios, bio);
827
828 if (!pe->started) {
829 /* this is protected by snap->lock */
830 pe->started = 1;
831 up_write(&s->lock);
832 start_copy(pe);
833 } else
834 up_write(&s->lock);
835 r = 0;
836 }
837 }
838
839 } else {
840 /*
841 * FIXME: this read path scares me because we
842 * always use the origin when we have a pending
843 * exception. However I can't think of a
844 * situation where this is wrong - ejt.
845 */
846
847 /* Do reads */
848 down_read(&s->lock);
849
850 /* See if it it has been remapped */
851 e = lookup_exception(&s->complete, chunk);
852 if (e)
853 remap_exception(s, e, bio);
854 else
855 bio->bi_bdev = s->origin->bdev;
856
857 up_read(&s->lock);
858 }
859
860 return r;
861}
862
863static void snapshot_resume(struct dm_target *ti)
864{
865 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
866
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800867 down_write(&s->lock);
868 s->active = 1;
869 up_write(&s->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870}
871
872static int snapshot_status(struct dm_target *ti, status_type_t type,
873 char *result, unsigned int maxlen)
874{
875 struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
876
877 switch (type) {
878 case STATUSTYPE_INFO:
879 if (!snap->valid)
880 snprintf(result, maxlen, "Invalid");
881 else {
882 if (snap->store.fraction_full) {
883 sector_t numerator, denominator;
884 snap->store.fraction_full(&snap->store,
885 &numerator,
886 &denominator);
887 snprintf(result, maxlen,
888 SECTOR_FORMAT "/" SECTOR_FORMAT,
889 numerator, denominator);
890 }
891 else
892 snprintf(result, maxlen, "Unknown");
893 }
894 break;
895
896 case STATUSTYPE_TABLE:
897 /*
898 * kdevname returns a static pointer so we need
899 * to make private copies if the output is to
900 * make sense.
901 */
902 snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT,
903 snap->origin->name, snap->cow->name,
904 snap->type, snap->chunk_size);
905 break;
906 }
907
908 return 0;
909}
910
911/*-----------------------------------------------------------------
912 * Origin methods
913 *---------------------------------------------------------------*/
914static void list_merge(struct list_head *l1, struct list_head *l2)
915{
916 struct list_head *l1_n, *l2_p;
917
918 l1_n = l1->next;
919 l2_p = l2->prev;
920
921 l1->next = l2;
922 l2->prev = l1;
923
924 l2_p->next = l1_n;
925 l1_n->prev = l2_p;
926}
927
928static int __origin_write(struct list_head *snapshots, struct bio *bio)
929{
930 int r = 1, first = 1;
931 struct dm_snapshot *snap;
932 struct exception *e;
933 struct pending_exception *pe, *last = NULL;
934 chunk_t chunk;
935
936 /* Do all the snapshots on this origin */
937 list_for_each_entry (snap, snapshots, list) {
938
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800939 /* Only deal with valid and active snapshots */
940 if (!snap->valid || !snap->active)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941 continue;
942
Alasdair G Kergond5e404c2005-07-12 15:53:05 -0700943 /* Nothing to do if writing beyond end of snapshot */
944 if (bio->bi_sector >= dm_table_get_size(snap->table))
945 continue;
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 down_write(&snap->lock);
948
949 /*
950 * Remember, different snapshots can have
951 * different chunk sizes.
952 */
953 chunk = sector_to_chunk(snap, bio->bi_sector);
954
955 /*
956 * Check exception table to see if block
957 * is already remapped in this snapshot
958 * and trigger an exception if not.
959 */
960 e = lookup_exception(&snap->complete, chunk);
961 if (!e) {
962 pe = __find_pending_exception(snap, bio);
963 if (!pe) {
964 snap->store.drop_snapshot(&snap->store);
965 snap->valid = 0;
966
967 } else {
968 if (last)
969 list_merge(&pe->siblings,
970 &last->siblings);
971
972 last = pe;
973 r = 0;
974 }
975 }
976
977 up_write(&snap->lock);
978 }
979
980 /*
981 * Now that we have a complete pe list we can start the copying.
982 */
983 if (last) {
984 pe = last;
985 do {
986 down_write(&pe->snap->lock);
987 if (first)
988 bio_list_add(&pe->origin_bios, bio);
989 if (!pe->started) {
990 pe->started = 1;
991 up_write(&pe->snap->lock);
992 start_copy(pe);
993 } else
994 up_write(&pe->snap->lock);
995 first = 0;
996 pe = list_entry(pe->siblings.next,
997 struct pending_exception, siblings);
998
999 } while (pe != last);
1000 }
1001
1002 return r;
1003}
1004
1005/*
1006 * Called on a write from the origin driver.
1007 */
1008static int do_origin(struct dm_dev *origin, struct bio *bio)
1009{
1010 struct origin *o;
1011 int r = 1;
1012
1013 down_read(&_origins_lock);
1014 o = __lookup_origin(origin->bdev);
1015 if (o)
1016 r = __origin_write(&o->snapshots, bio);
1017 up_read(&_origins_lock);
1018
1019 return r;
1020}
1021
1022/*
1023 * Origin: maps a linear range of a device, with hooks for snapshotting.
1024 */
1025
1026/*
1027 * Construct an origin mapping: <dev_path>
1028 * The context for an origin is merely a 'struct dm_dev *'
1029 * pointing to the real device.
1030 */
1031static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1032{
1033 int r;
1034 struct dm_dev *dev;
1035
1036 if (argc != 1) {
1037 ti->error = "dm-origin: incorrect number of arguments";
1038 return -EINVAL;
1039 }
1040
1041 r = dm_get_device(ti, argv[0], 0, ti->len,
1042 dm_table_get_mode(ti->table), &dev);
1043 if (r) {
1044 ti->error = "Cannot get target device";
1045 return r;
1046 }
1047
1048 ti->private = dev;
1049 return 0;
1050}
1051
1052static void origin_dtr(struct dm_target *ti)
1053{
1054 struct dm_dev *dev = (struct dm_dev *) ti->private;
1055 dm_put_device(ti, dev);
1056}
1057
1058static int origin_map(struct dm_target *ti, struct bio *bio,
1059 union map_info *map_context)
1060{
1061 struct dm_dev *dev = (struct dm_dev *) ti->private;
1062 bio->bi_bdev = dev->bdev;
1063
Alasdair G Kergon4aac0a62006-02-01 03:04:55 -08001064 if (unlikely(bio_barrier(bio)))
1065 return -EOPNOTSUPP;
1066
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 /* Only tell snapshots if this is a write */
1068 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
1069}
1070
1071#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
1072
1073/*
1074 * Set the target "split_io" field to the minimum of all the snapshots'
1075 * chunk sizes.
1076 */
1077static void origin_resume(struct dm_target *ti)
1078{
1079 struct dm_dev *dev = (struct dm_dev *) ti->private;
1080 struct dm_snapshot *snap;
1081 struct origin *o;
1082 chunk_t chunk_size = 0;
1083
1084 down_read(&_origins_lock);
1085 o = __lookup_origin(dev->bdev);
1086 if (o)
1087 list_for_each_entry (snap, &o->snapshots, list)
1088 chunk_size = min_not_zero(chunk_size, snap->chunk_size);
1089 up_read(&_origins_lock);
1090
1091 ti->split_io = chunk_size;
1092}
1093
1094static int origin_status(struct dm_target *ti, status_type_t type, char *result,
1095 unsigned int maxlen)
1096{
1097 struct dm_dev *dev = (struct dm_dev *) ti->private;
1098
1099 switch (type) {
1100 case STATUSTYPE_INFO:
1101 result[0] = '\0';
1102 break;
1103
1104 case STATUSTYPE_TABLE:
1105 snprintf(result, maxlen, "%s", dev->name);
1106 break;
1107 }
1108
1109 return 0;
1110}
1111
1112static struct target_type origin_target = {
1113 .name = "snapshot-origin",
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -08001114 .version = {1, 1, 0},
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115 .module = THIS_MODULE,
1116 .ctr = origin_ctr,
1117 .dtr = origin_dtr,
1118 .map = origin_map,
1119 .resume = origin_resume,
1120 .status = origin_status,
1121};
1122
1123static struct target_type snapshot_target = {
1124 .name = "snapshot",
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -08001125 .version = {1, 1, 0},
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 .module = THIS_MODULE,
1127 .ctr = snapshot_ctr,
1128 .dtr = snapshot_dtr,
1129 .map = snapshot_map,
1130 .resume = snapshot_resume,
1131 .status = snapshot_status,
1132};
1133
1134static int __init dm_snapshot_init(void)
1135{
1136 int r;
1137
1138 r = dm_register_target(&snapshot_target);
1139 if (r) {
1140 DMERR("snapshot target register failed %d", r);
1141 return r;
1142 }
1143
1144 r = dm_register_target(&origin_target);
1145 if (r < 0) {
1146 DMERR("Device mapper: Origin: register failed %d\n", r);
1147 goto bad1;
1148 }
1149
1150 r = init_origin_hash();
1151 if (r) {
1152 DMERR("init_origin_hash failed.");
1153 goto bad2;
1154 }
1155
1156 exception_cache = kmem_cache_create("dm-snapshot-ex",
1157 sizeof(struct exception),
1158 __alignof__(struct exception),
1159 0, NULL, NULL);
1160 if (!exception_cache) {
1161 DMERR("Couldn't create exception cache.");
1162 r = -ENOMEM;
1163 goto bad3;
1164 }
1165
1166 pending_cache =
1167 kmem_cache_create("dm-snapshot-in",
1168 sizeof(struct pending_exception),
1169 __alignof__(struct pending_exception),
1170 0, NULL, NULL);
1171 if (!pending_cache) {
1172 DMERR("Couldn't create pending cache.");
1173 r = -ENOMEM;
1174 goto bad4;
1175 }
1176
1177 pending_pool = mempool_create(128, mempool_alloc_slab,
1178 mempool_free_slab, pending_cache);
1179 if (!pending_pool) {
1180 DMERR("Couldn't create pending pool.");
1181 r = -ENOMEM;
1182 goto bad5;
1183 }
1184
1185 return 0;
1186
1187 bad5:
1188 kmem_cache_destroy(pending_cache);
1189 bad4:
1190 kmem_cache_destroy(exception_cache);
1191 bad3:
1192 exit_origin_hash();
1193 bad2:
1194 dm_unregister_target(&origin_target);
1195 bad1:
1196 dm_unregister_target(&snapshot_target);
1197 return r;
1198}
1199
1200static void __exit dm_snapshot_exit(void)
1201{
1202 int r;
1203
1204 r = dm_unregister_target(&snapshot_target);
1205 if (r)
1206 DMERR("snapshot unregister failed %d", r);
1207
1208 r = dm_unregister_target(&origin_target);
1209 if (r)
1210 DMERR("origin unregister failed %d", r);
1211
1212 exit_origin_hash();
1213 mempool_destroy(pending_pool);
1214 kmem_cache_destroy(pending_cache);
1215 kmem_cache_destroy(exception_cache);
1216}
1217
1218/* Module hooks */
1219module_init(dm_snapshot_init);
1220module_exit(dm_snapshot_exit);
1221
1222MODULE_DESCRIPTION(DM_NAME " snapshot target");
1223MODULE_AUTHOR("Joe Thornber");
1224MODULE_LICENSE("GPL");