Commit | Line | Data |
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1da177e4 LT |
1 | /* |
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 "dm.h" | |
10 | #include "dm-snap.h" | |
11 | #include "dm-io.h" | |
12 | #include "kcopyd.h" | |
13 | ||
14 | #include <linux/mm.h> | |
15 | #include <linux/pagemap.h> | |
16 | #include <linux/vmalloc.h> | |
17 | #include <linux/slab.h> | |
18 | ||
72d94861 | 19 | #define DM_MSG_PREFIX "snapshots" |
4c7e3bf4 | 20 | #define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */ |
72d94861 | 21 | |
1da177e4 LT |
22 | /*----------------------------------------------------------------- |
23 | * Persistent snapshots, by persistent we mean that the snapshot | |
24 | * will survive a reboot. | |
25 | *---------------------------------------------------------------*/ | |
26 | ||
27 | /* | |
28 | * We need to store a record of which parts of the origin have | |
29 | * been copied to the snapshot device. The snapshot code | |
30 | * requires that we copy exception chunks to chunk aligned areas | |
31 | * of the COW store. It makes sense therefore, to store the | |
32 | * metadata in chunk size blocks. | |
33 | * | |
34 | * There is no backward or forward compatibility implemented, | |
35 | * snapshots with different disk versions than the kernel will | |
36 | * not be usable. It is expected that "lvcreate" will blank out | |
37 | * the start of a fresh COW device before calling the snapshot | |
38 | * constructor. | |
39 | * | |
40 | * The first chunk of the COW device just contains the header. | |
41 | * After this there is a chunk filled with exception metadata, | |
42 | * followed by as many exception chunks as can fit in the | |
43 | * metadata areas. | |
44 | * | |
45 | * All on disk structures are in little-endian format. The end | |
46 | * of the exceptions info is indicated by an exception with a | |
47 | * new_chunk of 0, which is invalid since it would point to the | |
48 | * header chunk. | |
49 | */ | |
50 | ||
51 | /* | |
52 | * Magic for persistent snapshots: "SnAp" - Feeble isn't it. | |
53 | */ | |
54 | #define SNAP_MAGIC 0x70416e53 | |
55 | ||
56 | /* | |
57 | * The on-disk version of the metadata. | |
58 | */ | |
59 | #define SNAPSHOT_DISK_VERSION 1 | |
60 | ||
61 | struct disk_header { | |
62 | uint32_t magic; | |
63 | ||
64 | /* | |
65 | * Is this snapshot valid. There is no way of recovering | |
66 | * an invalid snapshot. | |
67 | */ | |
68 | uint32_t valid; | |
69 | ||
70 | /* | |
71 | * Simple, incrementing version. no backward | |
72 | * compatibility. | |
73 | */ | |
74 | uint32_t version; | |
75 | ||
76 | /* In sectors */ | |
77 | uint32_t chunk_size; | |
78 | }; | |
79 | ||
80 | struct disk_exception { | |
81 | uint64_t old_chunk; | |
82 | uint64_t new_chunk; | |
83 | }; | |
84 | ||
85 | struct commit_callback { | |
86 | void (*callback)(void *, int success); | |
87 | void *context; | |
88 | }; | |
89 | ||
90 | /* | |
91 | * The top level structure for a persistent exception store. | |
92 | */ | |
93 | struct pstore { | |
94 | struct dm_snapshot *snap; /* up pointer to my snapshot */ | |
95 | int version; | |
96 | int valid; | |
1da177e4 LT |
97 | uint32_t exceptions_per_area; |
98 | ||
99 | /* | |
100 | * Now that we have an asynchronous kcopyd there is no | |
101 | * need for large chunk sizes, so it wont hurt to have a | |
102 | * whole chunks worth of metadata in memory at once. | |
103 | */ | |
104 | void *area; | |
105 | ||
106 | /* | |
107 | * Used to keep track of which metadata area the data in | |
108 | * 'chunk' refers to. | |
109 | */ | |
110 | uint32_t current_area; | |
111 | ||
112 | /* | |
113 | * The next free chunk for an exception. | |
114 | */ | |
115 | uint32_t next_free; | |
116 | ||
117 | /* | |
118 | * The index of next free exception in the current | |
119 | * metadata area. | |
120 | */ | |
121 | uint32_t current_committed; | |
122 | ||
123 | atomic_t pending_count; | |
124 | uint32_t callback_count; | |
125 | struct commit_callback *callbacks; | |
126 | }; | |
127 | ||
128 | static inline unsigned int sectors_to_pages(unsigned int sectors) | |
129 | { | |
130 | return sectors / (PAGE_SIZE >> 9); | |
131 | } | |
132 | ||
133 | static int alloc_area(struct pstore *ps) | |
134 | { | |
135 | int r = -ENOMEM; | |
136 | size_t len; | |
137 | ||
c51c2752 | 138 | len = ps->snap->chunk_size << SECTOR_SHIFT; |
1da177e4 LT |
139 | |
140 | /* | |
141 | * Allocate the chunk_size block of memory that will hold | |
142 | * a single metadata area. | |
143 | */ | |
144 | ps->area = vmalloc(len); | |
145 | if (!ps->area) | |
146 | return r; | |
147 | ||
148 | return 0; | |
149 | } | |
150 | ||
151 | static void free_area(struct pstore *ps) | |
152 | { | |
153 | vfree(ps->area); | |
4c7e3bf4 | 154 | ps->area = NULL; |
1da177e4 LT |
155 | } |
156 | ||
157 | /* | |
158 | * Read or write a chunk aligned and sized block of data from a device. | |
159 | */ | |
160 | static int chunk_io(struct pstore *ps, uint32_t chunk, int rw) | |
161 | { | |
162 | struct io_region where; | |
163 | unsigned long bits; | |
164 | ||
165 | where.bdev = ps->snap->cow->bdev; | |
c51c2752 AK |
166 | where.sector = ps->snap->chunk_size * chunk; |
167 | where.count = ps->snap->chunk_size; | |
1da177e4 LT |
168 | |
169 | return dm_io_sync_vm(1, &where, rw, ps->area, &bits); | |
170 | } | |
171 | ||
172 | /* | |
173 | * Read or write a metadata area. Remembering to skip the first | |
174 | * chunk which holds the header. | |
175 | */ | |
176 | static int area_io(struct pstore *ps, uint32_t area, int rw) | |
177 | { | |
178 | int r; | |
179 | uint32_t chunk; | |
180 | ||
181 | /* convert a metadata area index to a chunk index */ | |
182 | chunk = 1 + ((ps->exceptions_per_area + 1) * area); | |
183 | ||
184 | r = chunk_io(ps, chunk, rw); | |
185 | if (r) | |
186 | return r; | |
187 | ||
188 | ps->current_area = area; | |
189 | return 0; | |
190 | } | |
191 | ||
192 | static int zero_area(struct pstore *ps, uint32_t area) | |
193 | { | |
c51c2752 | 194 | memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT); |
1da177e4 LT |
195 | return area_io(ps, area, WRITE); |
196 | } | |
197 | ||
198 | static int read_header(struct pstore *ps, int *new_snapshot) | |
199 | { | |
200 | int r; | |
201 | struct disk_header *dh; | |
c51c2752 | 202 | chunk_t chunk_size; |
4c7e3bf4 | 203 | int chunk_size_supplied = 1; |
1da177e4 | 204 | |
4c7e3bf4 MM |
205 | /* |
206 | * Use default chunk size (or hardsect_size, if larger) if none supplied | |
207 | */ | |
208 | if (!ps->snap->chunk_size) { | |
209 | ps->snap->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS, | |
210 | bdev_hardsect_size(ps->snap->cow->bdev) >> 9); | |
211 | ps->snap->chunk_mask = ps->snap->chunk_size - 1; | |
212 | ps->snap->chunk_shift = ffs(ps->snap->chunk_size) - 1; | |
213 | chunk_size_supplied = 0; | |
214 | } | |
215 | ||
216 | r = dm_io_get(sectors_to_pages(ps->snap->chunk_size)); | |
1da177e4 LT |
217 | if (r) |
218 | return r; | |
219 | ||
4c7e3bf4 MM |
220 | r = alloc_area(ps); |
221 | if (r) | |
222 | goto bad1; | |
223 | ||
224 | r = chunk_io(ps, 0, READ); | |
225 | if (r) | |
226 | goto bad2; | |
227 | ||
1da177e4 LT |
228 | dh = (struct disk_header *) ps->area; |
229 | ||
230 | if (le32_to_cpu(dh->magic) == 0) { | |
231 | *new_snapshot = 1; | |
4c7e3bf4 MM |
232 | return 0; |
233 | } | |
1da177e4 | 234 | |
4c7e3bf4 MM |
235 | if (le32_to_cpu(dh->magic) != SNAP_MAGIC) { |
236 | DMWARN("Invalid or corrupt snapshot"); | |
1da177e4 | 237 | r = -ENXIO; |
4c7e3bf4 | 238 | goto bad2; |
1da177e4 LT |
239 | } |
240 | ||
4c7e3bf4 MM |
241 | *new_snapshot = 0; |
242 | ps->valid = le32_to_cpu(dh->valid); | |
243 | ps->version = le32_to_cpu(dh->version); | |
244 | chunk_size = le32_to_cpu(dh->chunk_size); | |
245 | ||
246 | if (!chunk_size_supplied || ps->snap->chunk_size == chunk_size) | |
247 | return 0; | |
248 | ||
249 | DMWARN("chunk size %llu in device metadata overrides " | |
250 | "table chunk size of %llu.", | |
251 | (unsigned long long)chunk_size, | |
252 | (unsigned long long)ps->snap->chunk_size); | |
253 | ||
254 | /* We had a bogus chunk_size. Fix stuff up. */ | |
255 | dm_io_put(sectors_to_pages(ps->snap->chunk_size)); | |
256 | free_area(ps); | |
257 | ||
258 | ps->snap->chunk_size = chunk_size; | |
259 | ps->snap->chunk_mask = chunk_size - 1; | |
260 | ps->snap->chunk_shift = ffs(chunk_size) - 1; | |
261 | ||
262 | r = dm_io_get(sectors_to_pages(chunk_size)); | |
263 | if (r) | |
264 | return r; | |
265 | ||
266 | r = alloc_area(ps); | |
267 | if (r) | |
268 | goto bad1; | |
269 | ||
270 | return 0; | |
271 | ||
272 | bad2: | |
273 | free_area(ps); | |
274 | bad1: | |
275 | dm_io_put(sectors_to_pages(ps->snap->chunk_size)); | |
1da177e4 LT |
276 | return r; |
277 | } | |
278 | ||
279 | static int write_header(struct pstore *ps) | |
280 | { | |
281 | struct disk_header *dh; | |
282 | ||
c51c2752 | 283 | memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT); |
1da177e4 LT |
284 | |
285 | dh = (struct disk_header *) ps->area; | |
286 | dh->magic = cpu_to_le32(SNAP_MAGIC); | |
287 | dh->valid = cpu_to_le32(ps->valid); | |
288 | dh->version = cpu_to_le32(ps->version); | |
c51c2752 | 289 | dh->chunk_size = cpu_to_le32(ps->snap->chunk_size); |
1da177e4 LT |
290 | |
291 | return chunk_io(ps, 0, WRITE); | |
292 | } | |
293 | ||
294 | /* | |
295 | * Access functions for the disk exceptions, these do the endian conversions. | |
296 | */ | |
297 | static struct disk_exception *get_exception(struct pstore *ps, uint32_t index) | |
298 | { | |
e4ff496d | 299 | BUG_ON(index >= ps->exceptions_per_area); |
1da177e4 LT |
300 | |
301 | return ((struct disk_exception *) ps->area) + index; | |
302 | } | |
303 | ||
e4ff496d MM |
304 | static void read_exception(struct pstore *ps, |
305 | uint32_t index, struct disk_exception *result) | |
1da177e4 | 306 | { |
e4ff496d | 307 | struct disk_exception *e = get_exception(ps, index); |
1da177e4 LT |
308 | |
309 | /* copy it */ | |
310 | result->old_chunk = le64_to_cpu(e->old_chunk); | |
311 | result->new_chunk = le64_to_cpu(e->new_chunk); | |
1da177e4 LT |
312 | } |
313 | ||
e4ff496d MM |
314 | static void write_exception(struct pstore *ps, |
315 | uint32_t index, struct disk_exception *de) | |
1da177e4 | 316 | { |
e4ff496d | 317 | struct disk_exception *e = get_exception(ps, index); |
1da177e4 LT |
318 | |
319 | /* copy it */ | |
320 | e->old_chunk = cpu_to_le64(de->old_chunk); | |
321 | e->new_chunk = cpu_to_le64(de->new_chunk); | |
1da177e4 LT |
322 | } |
323 | ||
324 | /* | |
325 | * Registers the exceptions that are present in the current area. | |
326 | * 'full' is filled in to indicate if the area has been | |
327 | * filled. | |
328 | */ | |
329 | static int insert_exceptions(struct pstore *ps, int *full) | |
330 | { | |
331 | int r; | |
332 | unsigned int i; | |
333 | struct disk_exception de; | |
334 | ||
335 | /* presume the area is full */ | |
336 | *full = 1; | |
337 | ||
338 | for (i = 0; i < ps->exceptions_per_area; i++) { | |
e4ff496d | 339 | read_exception(ps, i, &de); |
1da177e4 LT |
340 | |
341 | /* | |
342 | * If the new_chunk is pointing at the start of | |
343 | * the COW device, where the first metadata area | |
344 | * is we know that we've hit the end of the | |
345 | * exceptions. Therefore the area is not full. | |
346 | */ | |
347 | if (de.new_chunk == 0LL) { | |
348 | ps->current_committed = i; | |
349 | *full = 0; | |
350 | break; | |
351 | } | |
352 | ||
353 | /* | |
354 | * Keep track of the start of the free chunks. | |
355 | */ | |
356 | if (ps->next_free <= de.new_chunk) | |
357 | ps->next_free = de.new_chunk + 1; | |
358 | ||
359 | /* | |
360 | * Otherwise we add the exception to the snapshot. | |
361 | */ | |
362 | r = dm_add_exception(ps->snap, de.old_chunk, de.new_chunk); | |
363 | if (r) | |
364 | return r; | |
365 | } | |
366 | ||
367 | return 0; | |
368 | } | |
369 | ||
370 | static int read_exceptions(struct pstore *ps) | |
371 | { | |
372 | uint32_t area; | |
373 | int r, full = 1; | |
374 | ||
375 | /* | |
376 | * Keeping reading chunks and inserting exceptions until | |
377 | * we find a partially full area. | |
378 | */ | |
379 | for (area = 0; full; area++) { | |
380 | r = area_io(ps, area, READ); | |
381 | if (r) | |
382 | return r; | |
383 | ||
384 | r = insert_exceptions(ps, &full); | |
385 | if (r) | |
386 | return r; | |
387 | } | |
388 | ||
389 | return 0; | |
390 | } | |
391 | ||
392 | static inline struct pstore *get_info(struct exception_store *store) | |
393 | { | |
394 | return (struct pstore *) store->context; | |
395 | } | |
396 | ||
397 | static void persistent_fraction_full(struct exception_store *store, | |
398 | sector_t *numerator, sector_t *denominator) | |
399 | { | |
400 | *numerator = get_info(store)->next_free * store->snap->chunk_size; | |
401 | *denominator = get_dev_size(store->snap->cow->bdev); | |
402 | } | |
403 | ||
404 | static void persistent_destroy(struct exception_store *store) | |
405 | { | |
406 | struct pstore *ps = get_info(store); | |
407 | ||
c51c2752 | 408 | dm_io_put(sectors_to_pages(ps->snap->chunk_size)); |
1da177e4 LT |
409 | vfree(ps->callbacks); |
410 | free_area(ps); | |
411 | kfree(ps); | |
412 | } | |
413 | ||
414 | static int persistent_read_metadata(struct exception_store *store) | |
415 | { | |
416 | int r, new_snapshot; | |
417 | struct pstore *ps = get_info(store); | |
418 | ||
419 | /* | |
420 | * Read the snapshot header. | |
421 | */ | |
422 | r = read_header(ps, &new_snapshot); | |
423 | if (r) | |
424 | return r; | |
425 | ||
c51c2752 AK |
426 | /* |
427 | * Now we know correct chunk_size, complete the initialisation. | |
428 | */ | |
429 | ps->exceptions_per_area = (ps->snap->chunk_size << SECTOR_SHIFT) / | |
430 | sizeof(struct disk_exception); | |
431 | ps->callbacks = dm_vcalloc(ps->exceptions_per_area, | |
432 | sizeof(*ps->callbacks)); | |
433 | if (!ps->callbacks) | |
434 | return -ENOMEM; | |
435 | ||
1da177e4 LT |
436 | /* |
437 | * Do we need to setup a new snapshot ? | |
438 | */ | |
439 | if (new_snapshot) { | |
440 | r = write_header(ps); | |
441 | if (r) { | |
442 | DMWARN("write_header failed"); | |
443 | return r; | |
444 | } | |
445 | ||
446 | r = zero_area(ps, 0); | |
447 | if (r) { | |
448 | DMWARN("zero_area(0) failed"); | |
449 | return r; | |
450 | } | |
451 | ||
452 | } else { | |
453 | /* | |
454 | * Sanity checks. | |
455 | */ | |
456 | if (!ps->valid) { | |
457 | DMWARN("snapshot is marked invalid"); | |
458 | return -EINVAL; | |
459 | } | |
460 | ||
461 | if (ps->version != SNAPSHOT_DISK_VERSION) { | |
462 | DMWARN("unable to handle snapshot disk version %d", | |
463 | ps->version); | |
464 | return -EINVAL; | |
465 | } | |
466 | ||
467 | /* | |
468 | * Read the metadata. | |
469 | */ | |
470 | r = read_exceptions(ps); | |
471 | if (r) | |
472 | return r; | |
473 | } | |
474 | ||
475 | return 0; | |
476 | } | |
477 | ||
478 | static int persistent_prepare(struct exception_store *store, | |
479 | struct exception *e) | |
480 | { | |
481 | struct pstore *ps = get_info(store); | |
482 | uint32_t stride; | |
483 | sector_t size = get_dev_size(store->snap->cow->bdev); | |
484 | ||
485 | /* Is there enough room ? */ | |
486 | if (size < ((ps->next_free + 1) * store->snap->chunk_size)) | |
487 | return -ENOSPC; | |
488 | ||
489 | e->new_chunk = ps->next_free; | |
490 | ||
491 | /* | |
492 | * Move onto the next free pending, making sure to take | |
493 | * into account the location of the metadata chunks. | |
494 | */ | |
495 | stride = (ps->exceptions_per_area + 1); | |
496 | if ((++ps->next_free % stride) == 1) | |
497 | ps->next_free++; | |
498 | ||
499 | atomic_inc(&ps->pending_count); | |
500 | return 0; | |
501 | } | |
502 | ||
503 | static void persistent_commit(struct exception_store *store, | |
504 | struct exception *e, | |
505 | void (*callback) (void *, int success), | |
506 | void *callback_context) | |
507 | { | |
508 | int r; | |
509 | unsigned int i; | |
510 | struct pstore *ps = get_info(store); | |
511 | struct disk_exception de; | |
512 | struct commit_callback *cb; | |
513 | ||
514 | de.old_chunk = e->old_chunk; | |
515 | de.new_chunk = e->new_chunk; | |
516 | write_exception(ps, ps->current_committed++, &de); | |
517 | ||
518 | /* | |
519 | * Add the callback to the back of the array. This code | |
520 | * is the only place where the callback array is | |
521 | * manipulated, and we know that it will never be called | |
522 | * multiple times concurrently. | |
523 | */ | |
524 | cb = ps->callbacks + ps->callback_count++; | |
525 | cb->callback = callback; | |
526 | cb->context = callback_context; | |
527 | ||
528 | /* | |
529 | * If there are no more exceptions in flight, or we have | |
530 | * filled this metadata area we commit the exceptions to | |
531 | * disk. | |
532 | */ | |
533 | if (atomic_dec_and_test(&ps->pending_count) || | |
534 | (ps->current_committed == ps->exceptions_per_area)) { | |
535 | r = area_io(ps, ps->current_area, WRITE); | |
536 | if (r) | |
537 | ps->valid = 0; | |
538 | ||
927ffe7c MM |
539 | /* |
540 | * Have we completely filled the current area ? | |
541 | */ | |
542 | if (ps->current_committed == ps->exceptions_per_area) { | |
543 | ps->current_committed = 0; | |
544 | r = zero_area(ps, ps->current_area + 1); | |
545 | if (r) | |
546 | ps->valid = 0; | |
547 | } | |
548 | ||
1da177e4 LT |
549 | for (i = 0; i < ps->callback_count; i++) { |
550 | cb = ps->callbacks + i; | |
551 | cb->callback(cb->context, r == 0 ? 1 : 0); | |
552 | } | |
553 | ||
554 | ps->callback_count = 0; | |
555 | } | |
1da177e4 LT |
556 | } |
557 | ||
558 | static void persistent_drop(struct exception_store *store) | |
559 | { | |
560 | struct pstore *ps = get_info(store); | |
561 | ||
562 | ps->valid = 0; | |
563 | if (write_header(ps)) | |
564 | DMWARN("write header failed"); | |
565 | } | |
566 | ||
4c7e3bf4 | 567 | int dm_create_persistent(struct exception_store *store) |
1da177e4 | 568 | { |
1da177e4 LT |
569 | struct pstore *ps; |
570 | ||
1da177e4 LT |
571 | /* allocate the pstore */ |
572 | ps = kmalloc(sizeof(*ps), GFP_KERNEL); | |
4c7e3bf4 MM |
573 | if (!ps) |
574 | return -ENOMEM; | |
1da177e4 LT |
575 | |
576 | ps->snap = store->snap; | |
577 | ps->valid = 1; | |
578 | ps->version = SNAPSHOT_DISK_VERSION; | |
4c7e3bf4 | 579 | ps->area = NULL; |
1da177e4 LT |
580 | ps->next_free = 2; /* skipping the header and first area */ |
581 | ps->current_committed = 0; | |
582 | ||
1da177e4 LT |
583 | ps->callback_count = 0; |
584 | atomic_set(&ps->pending_count, 0); | |
c51c2752 | 585 | ps->callbacks = NULL; |
1da177e4 LT |
586 | |
587 | store->destroy = persistent_destroy; | |
588 | store->read_metadata = persistent_read_metadata; | |
589 | store->prepare_exception = persistent_prepare; | |
590 | store->commit_exception = persistent_commit; | |
591 | store->drop_snapshot = persistent_drop; | |
592 | store->fraction_full = persistent_fraction_full; | |
593 | store->context = ps; | |
594 | ||
595 | return 0; | |
1da177e4 LT |
596 | } |
597 | ||
598 | /*----------------------------------------------------------------- | |
599 | * Implementation of the store for non-persistent snapshots. | |
600 | *---------------------------------------------------------------*/ | |
601 | struct transient_c { | |
602 | sector_t next_free; | |
603 | }; | |
604 | ||
605 | static void transient_destroy(struct exception_store *store) | |
606 | { | |
607 | kfree(store->context); | |
608 | } | |
609 | ||
610 | static int transient_read_metadata(struct exception_store *store) | |
611 | { | |
612 | return 0; | |
613 | } | |
614 | ||
615 | static int transient_prepare(struct exception_store *store, struct exception *e) | |
616 | { | |
617 | struct transient_c *tc = (struct transient_c *) store->context; | |
618 | sector_t size = get_dev_size(store->snap->cow->bdev); | |
619 | ||
620 | if (size < (tc->next_free + store->snap->chunk_size)) | |
621 | return -1; | |
622 | ||
623 | e->new_chunk = sector_to_chunk(store->snap, tc->next_free); | |
624 | tc->next_free += store->snap->chunk_size; | |
625 | ||
626 | return 0; | |
627 | } | |
628 | ||
629 | static void transient_commit(struct exception_store *store, | |
630 | struct exception *e, | |
631 | void (*callback) (void *, int success), | |
632 | void *callback_context) | |
633 | { | |
634 | /* Just succeed */ | |
635 | callback(callback_context, 1); | |
636 | } | |
637 | ||
638 | static void transient_fraction_full(struct exception_store *store, | |
639 | sector_t *numerator, sector_t *denominator) | |
640 | { | |
641 | *numerator = ((struct transient_c *) store->context)->next_free; | |
642 | *denominator = get_dev_size(store->snap->cow->bdev); | |
643 | } | |
644 | ||
4c7e3bf4 | 645 | int dm_create_transient(struct exception_store *store) |
1da177e4 LT |
646 | { |
647 | struct transient_c *tc; | |
648 | ||
1da177e4 LT |
649 | store->destroy = transient_destroy; |
650 | store->read_metadata = transient_read_metadata; | |
651 | store->prepare_exception = transient_prepare; | |
652 | store->commit_exception = transient_commit; | |
4c7e3bf4 | 653 | store->drop_snapshot = NULL; |
1da177e4 | 654 | store->fraction_full = transient_fraction_full; |
1da177e4 LT |
655 | |
656 | tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL); | |
657 | if (!tc) | |
658 | return -ENOMEM; | |
659 | ||
660 | tc->next_free = 0; | |
661 | store->context = tc; | |
662 | ||
663 | return 0; | |
664 | } |