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1 | /* | |
2 | * Copyright (C) 2001-2002 Sistina Software (UK) Limited. | |
3 | * Copyright (C) 2006-2008 Red Hat GmbH | |
4 | * | |
5 | * This file is released under the GPL. | |
6 | */ | |
7 | ||
8 | #include "dm-exception-store.h" | |
9 | ||
10 | #include <linux/mm.h> | |
11 | #include <linux/pagemap.h> | |
12 | #include <linux/vmalloc.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/dm-io.h> | |
15 | ||
16 | #define DM_MSG_PREFIX "persistent snapshot" | |
17 | #define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */ | |
18 | ||
19 | /*----------------------------------------------------------------- | |
20 | * Persistent snapshots, by persistent we mean that the snapshot | |
21 | * will survive a reboot. | |
22 | *---------------------------------------------------------------*/ | |
23 | ||
24 | /* | |
25 | * We need to store a record of which parts of the origin have | |
26 | * been copied to the snapshot device. The snapshot code | |
27 | * requires that we copy exception chunks to chunk aligned areas | |
28 | * of the COW store. It makes sense therefore, to store the | |
29 | * metadata in chunk size blocks. | |
30 | * | |
31 | * There is no backward or forward compatibility implemented, | |
32 | * snapshots with different disk versions than the kernel will | |
33 | * not be usable. It is expected that "lvcreate" will blank out | |
34 | * the start of a fresh COW device before calling the snapshot | |
35 | * constructor. | |
36 | * | |
37 | * The first chunk of the COW device just contains the header. | |
38 | * After this there is a chunk filled with exception metadata, | |
39 | * followed by as many exception chunks as can fit in the | |
40 | * metadata areas. | |
41 | * | |
42 | * All on disk structures are in little-endian format. The end | |
43 | * of the exceptions info is indicated by an exception with a | |
44 | * new_chunk of 0, which is invalid since it would point to the | |
45 | * header chunk. | |
46 | */ | |
47 | ||
48 | /* | |
49 | * Magic for persistent snapshots: "SnAp" - Feeble isn't it. | |
50 | */ | |
51 | #define SNAP_MAGIC 0x70416e53 | |
52 | ||
53 | /* | |
54 | * The on-disk version of the metadata. | |
55 | */ | |
56 | #define SNAPSHOT_DISK_VERSION 1 | |
57 | ||
58 | #define NUM_SNAPSHOT_HDR_CHUNKS 1 | |
59 | ||
60 | struct disk_header { | |
61 | uint32_t magic; | |
62 | ||
63 | /* | |
64 | * Is this snapshot valid. There is no way of recovering | |
65 | * an invalid snapshot. | |
66 | */ | |
67 | uint32_t valid; | |
68 | ||
69 | /* | |
70 | * Simple, incrementing version. no backward | |
71 | * compatibility. | |
72 | */ | |
73 | uint32_t version; | |
74 | ||
75 | /* In sectors */ | |
76 | uint32_t chunk_size; | |
77 | }; | |
78 | ||
79 | struct disk_exception { | |
80 | uint64_t old_chunk; | |
81 | uint64_t new_chunk; | |
82 | }; | |
83 | ||
84 | struct commit_callback { | |
85 | void (*callback)(void *, int success); | |
86 | void *context; | |
87 | }; | |
88 | ||
89 | /* | |
90 | * The top level structure for a persistent exception store. | |
91 | */ | |
92 | struct pstore { | |
93 | struct dm_exception_store *store; | |
94 | int version; | |
95 | int valid; | |
96 | uint32_t exceptions_per_area; | |
97 | ||
98 | /* | |
99 | * Now that we have an asynchronous kcopyd there is no | |
100 | * need for large chunk sizes, so it wont hurt to have a | |
101 | * whole chunks worth of metadata in memory at once. | |
102 | */ | |
103 | void *area; | |
104 | ||
105 | /* | |
106 | * An area of zeros used to clear the next area. | |
107 | */ | |
108 | void *zero_area; | |
109 | ||
110 | /* | |
111 | * An area used for header. The header can be written | |
112 | * concurrently with metadata (when invalidating the snapshot), | |
113 | * so it needs a separate buffer. | |
114 | */ | |
115 | void *header_area; | |
116 | ||
117 | /* | |
118 | * Used to keep track of which metadata area the data in | |
119 | * 'chunk' refers to. | |
120 | */ | |
121 | chunk_t current_area; | |
122 | ||
123 | /* | |
124 | * The next free chunk for an exception. | |
125 | * | |
126 | * When creating exceptions, all the chunks here and above are | |
127 | * free. It holds the next chunk to be allocated. On rare | |
128 | * occasions (e.g. after a system crash) holes can be left in | |
129 | * the exception store because chunks can be committed out of | |
130 | * order. | |
131 | * | |
132 | * When merging exceptions, it does not necessarily mean all the | |
133 | * chunks here and above are free. It holds the value it would | |
134 | * have held if all chunks had been committed in order of | |
135 | * allocation. Consequently the value may occasionally be | |
136 | * slightly too low, but since it's only used for 'status' and | |
137 | * it can never reach its minimum value too early this doesn't | |
138 | * matter. | |
139 | */ | |
140 | ||
141 | chunk_t next_free; | |
142 | ||
143 | /* | |
144 | * The index of next free exception in the current | |
145 | * metadata area. | |
146 | */ | |
147 | uint32_t current_committed; | |
148 | ||
149 | atomic_t pending_count; | |
150 | uint32_t callback_count; | |
151 | struct commit_callback *callbacks; | |
152 | struct dm_io_client *io_client; | |
153 | ||
154 | struct workqueue_struct *metadata_wq; | |
155 | }; | |
156 | ||
157 | static unsigned sectors_to_pages(unsigned sectors) | |
158 | { | |
159 | return DIV_ROUND_UP(sectors, PAGE_SIZE >> 9); | |
160 | } | |
161 | ||
162 | static int alloc_area(struct pstore *ps) | |
163 | { | |
164 | int r = -ENOMEM; | |
165 | size_t len; | |
166 | ||
167 | len = ps->store->chunk_size << SECTOR_SHIFT; | |
168 | ||
169 | /* | |
170 | * Allocate the chunk_size block of memory that will hold | |
171 | * a single metadata area. | |
172 | */ | |
173 | ps->area = vmalloc(len); | |
174 | if (!ps->area) | |
175 | goto err_area; | |
176 | ||
177 | ps->zero_area = vmalloc(len); | |
178 | if (!ps->zero_area) | |
179 | goto err_zero_area; | |
180 | memset(ps->zero_area, 0, len); | |
181 | ||
182 | ps->header_area = vmalloc(len); | |
183 | if (!ps->header_area) | |
184 | goto err_header_area; | |
185 | ||
186 | return 0; | |
187 | ||
188 | err_header_area: | |
189 | vfree(ps->zero_area); | |
190 | ||
191 | err_zero_area: | |
192 | vfree(ps->area); | |
193 | ||
194 | err_area: | |
195 | return r; | |
196 | } | |
197 | ||
198 | static void free_area(struct pstore *ps) | |
199 | { | |
200 | if (ps->area) | |
201 | vfree(ps->area); | |
202 | ps->area = NULL; | |
203 | ||
204 | if (ps->zero_area) | |
205 | vfree(ps->zero_area); | |
206 | ps->zero_area = NULL; | |
207 | ||
208 | if (ps->header_area) | |
209 | vfree(ps->header_area); | |
210 | ps->header_area = NULL; | |
211 | } | |
212 | ||
213 | struct mdata_req { | |
214 | struct dm_io_region *where; | |
215 | struct dm_io_request *io_req; | |
216 | struct work_struct work; | |
217 | int result; | |
218 | }; | |
219 | ||
220 | static void do_metadata(struct work_struct *work) | |
221 | { | |
222 | struct mdata_req *req = container_of(work, struct mdata_req, work); | |
223 | ||
224 | req->result = dm_io(req->io_req, 1, req->where, NULL); | |
225 | } | |
226 | ||
227 | /* | |
228 | * Read or write a chunk aligned and sized block of data from a device. | |
229 | */ | |
230 | static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw, | |
231 | int metadata) | |
232 | { | |
233 | struct dm_io_region where = { | |
234 | .bdev = dm_snap_cow(ps->store->snap)->bdev, | |
235 | .sector = ps->store->chunk_size * chunk, | |
236 | .count = ps->store->chunk_size, | |
237 | }; | |
238 | struct dm_io_request io_req = { | |
239 | .bi_rw = rw, | |
240 | .mem.type = DM_IO_VMA, | |
241 | .mem.ptr.vma = area, | |
242 | .client = ps->io_client, | |
243 | .notify.fn = NULL, | |
244 | }; | |
245 | struct mdata_req req; | |
246 | ||
247 | if (!metadata) | |
248 | return dm_io(&io_req, 1, &where, NULL); | |
249 | ||
250 | req.where = &where; | |
251 | req.io_req = &io_req; | |
252 | ||
253 | /* | |
254 | * Issue the synchronous I/O from a different thread | |
255 | * to avoid generic_make_request recursion. | |
256 | */ | |
257 | INIT_WORK_ON_STACK(&req.work, do_metadata); | |
258 | queue_work(ps->metadata_wq, &req.work); | |
259 | flush_workqueue(ps->metadata_wq); | |
260 | ||
261 | return req.result; | |
262 | } | |
263 | ||
264 | /* | |
265 | * Convert a metadata area index to a chunk index. | |
266 | */ | |
267 | static chunk_t area_location(struct pstore *ps, chunk_t area) | |
268 | { | |
269 | return 1 + ((ps->exceptions_per_area + 1) * area); | |
270 | } | |
271 | ||
272 | /* | |
273 | * Read or write a metadata area. Remembering to skip the first | |
274 | * chunk which holds the header. | |
275 | */ | |
276 | static int area_io(struct pstore *ps, int rw) | |
277 | { | |
278 | int r; | |
279 | chunk_t chunk; | |
280 | ||
281 | chunk = area_location(ps, ps->current_area); | |
282 | ||
283 | r = chunk_io(ps, ps->area, chunk, rw, 0); | |
284 | if (r) | |
285 | return r; | |
286 | ||
287 | return 0; | |
288 | } | |
289 | ||
290 | static void zero_memory_area(struct pstore *ps) | |
291 | { | |
292 | memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT); | |
293 | } | |
294 | ||
295 | static int zero_disk_area(struct pstore *ps, chunk_t area) | |
296 | { | |
297 | return chunk_io(ps, ps->zero_area, area_location(ps, area), WRITE, 0); | |
298 | } | |
299 | ||
300 | static int read_header(struct pstore *ps, int *new_snapshot) | |
301 | { | |
302 | int r; | |
303 | struct disk_header *dh; | |
304 | unsigned chunk_size; | |
305 | int chunk_size_supplied = 1; | |
306 | char *chunk_err; | |
307 | ||
308 | /* | |
309 | * Use default chunk size (or logical_block_size, if larger) | |
310 | * if none supplied | |
311 | */ | |
312 | if (!ps->store->chunk_size) { | |
313 | ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS, | |
314 | bdev_logical_block_size(dm_snap_cow(ps->store->snap)-> | |
315 | bdev) >> 9); | |
316 | ps->store->chunk_mask = ps->store->chunk_size - 1; | |
317 | ps->store->chunk_shift = ffs(ps->store->chunk_size) - 1; | |
318 | chunk_size_supplied = 0; | |
319 | } | |
320 | ||
321 | ps->io_client = dm_io_client_create(sectors_to_pages(ps->store-> | |
322 | chunk_size)); | |
323 | if (IS_ERR(ps->io_client)) | |
324 | return PTR_ERR(ps->io_client); | |
325 | ||
326 | r = alloc_area(ps); | |
327 | if (r) | |
328 | return r; | |
329 | ||
330 | r = chunk_io(ps, ps->header_area, 0, READ, 1); | |
331 | if (r) | |
332 | goto bad; | |
333 | ||
334 | dh = ps->header_area; | |
335 | ||
336 | if (le32_to_cpu(dh->magic) == 0) { | |
337 | *new_snapshot = 1; | |
338 | return 0; | |
339 | } | |
340 | ||
341 | if (le32_to_cpu(dh->magic) != SNAP_MAGIC) { | |
342 | DMWARN("Invalid or corrupt snapshot"); | |
343 | r = -ENXIO; | |
344 | goto bad; | |
345 | } | |
346 | ||
347 | *new_snapshot = 0; | |
348 | ps->valid = le32_to_cpu(dh->valid); | |
349 | ps->version = le32_to_cpu(dh->version); | |
350 | chunk_size = le32_to_cpu(dh->chunk_size); | |
351 | ||
352 | if (ps->store->chunk_size == chunk_size) | |
353 | return 0; | |
354 | ||
355 | if (chunk_size_supplied) | |
356 | DMWARN("chunk size %u in device metadata overrides " | |
357 | "table chunk size of %u.", | |
358 | chunk_size, ps->store->chunk_size); | |
359 | ||
360 | /* We had a bogus chunk_size. Fix stuff up. */ | |
361 | free_area(ps); | |
362 | ||
363 | r = dm_exception_store_set_chunk_size(ps->store, chunk_size, | |
364 | &chunk_err); | |
365 | if (r) { | |
366 | DMERR("invalid on-disk chunk size %u: %s.", | |
367 | chunk_size, chunk_err); | |
368 | return r; | |
369 | } | |
370 | ||
371 | r = dm_io_client_resize(sectors_to_pages(ps->store->chunk_size), | |
372 | ps->io_client); | |
373 | if (r) | |
374 | return r; | |
375 | ||
376 | r = alloc_area(ps); | |
377 | return r; | |
378 | ||
379 | bad: | |
380 | free_area(ps); | |
381 | return r; | |
382 | } | |
383 | ||
384 | static int write_header(struct pstore *ps) | |
385 | { | |
386 | struct disk_header *dh; | |
387 | ||
388 | memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT); | |
389 | ||
390 | dh = ps->header_area; | |
391 | dh->magic = cpu_to_le32(SNAP_MAGIC); | |
392 | dh->valid = cpu_to_le32(ps->valid); | |
393 | dh->version = cpu_to_le32(ps->version); | |
394 | dh->chunk_size = cpu_to_le32(ps->store->chunk_size); | |
395 | ||
396 | return chunk_io(ps, ps->header_area, 0, WRITE, 1); | |
397 | } | |
398 | ||
399 | /* | |
400 | * Access functions for the disk exceptions, these do the endian conversions. | |
401 | */ | |
402 | static struct disk_exception *get_exception(struct pstore *ps, uint32_t index) | |
403 | { | |
404 | BUG_ON(index >= ps->exceptions_per_area); | |
405 | ||
406 | return ((struct disk_exception *) ps->area) + index; | |
407 | } | |
408 | ||
409 | static void read_exception(struct pstore *ps, | |
410 | uint32_t index, struct disk_exception *result) | |
411 | { | |
412 | struct disk_exception *e = get_exception(ps, index); | |
413 | ||
414 | /* copy it */ | |
415 | result->old_chunk = le64_to_cpu(e->old_chunk); | |
416 | result->new_chunk = le64_to_cpu(e->new_chunk); | |
417 | } | |
418 | ||
419 | static void write_exception(struct pstore *ps, | |
420 | uint32_t index, struct disk_exception *de) | |
421 | { | |
422 | struct disk_exception *e = get_exception(ps, index); | |
423 | ||
424 | /* copy it */ | |
425 | e->old_chunk = cpu_to_le64(de->old_chunk); | |
426 | e->new_chunk = cpu_to_le64(de->new_chunk); | |
427 | } | |
428 | ||
429 | static void clear_exception(struct pstore *ps, uint32_t index) | |
430 | { | |
431 | struct disk_exception *e = get_exception(ps, index); | |
432 | ||
433 | /* clear it */ | |
434 | e->old_chunk = 0; | |
435 | e->new_chunk = 0; | |
436 | } | |
437 | ||
438 | /* | |
439 | * Registers the exceptions that are present in the current area. | |
440 | * 'full' is filled in to indicate if the area has been | |
441 | * filled. | |
442 | */ | |
443 | static int insert_exceptions(struct pstore *ps, | |
444 | int (*callback)(void *callback_context, | |
445 | chunk_t old, chunk_t new), | |
446 | void *callback_context, | |
447 | int *full) | |
448 | { | |
449 | int r; | |
450 | unsigned int i; | |
451 | struct disk_exception de; | |
452 | ||
453 | /* presume the area is full */ | |
454 | *full = 1; | |
455 | ||
456 | for (i = 0; i < ps->exceptions_per_area; i++) { | |
457 | read_exception(ps, i, &de); | |
458 | ||
459 | /* | |
460 | * If the new_chunk is pointing at the start of | |
461 | * the COW device, where the first metadata area | |
462 | * is we know that we've hit the end of the | |
463 | * exceptions. Therefore the area is not full. | |
464 | */ | |
465 | if (de.new_chunk == 0LL) { | |
466 | ps->current_committed = i; | |
467 | *full = 0; | |
468 | break; | |
469 | } | |
470 | ||
471 | /* | |
472 | * Keep track of the start of the free chunks. | |
473 | */ | |
474 | if (ps->next_free <= de.new_chunk) | |
475 | ps->next_free = de.new_chunk + 1; | |
476 | ||
477 | /* | |
478 | * Otherwise we add the exception to the snapshot. | |
479 | */ | |
480 | r = callback(callback_context, de.old_chunk, de.new_chunk); | |
481 | if (r) | |
482 | return r; | |
483 | } | |
484 | ||
485 | return 0; | |
486 | } | |
487 | ||
488 | static int read_exceptions(struct pstore *ps, | |
489 | int (*callback)(void *callback_context, chunk_t old, | |
490 | chunk_t new), | |
491 | void *callback_context) | |
492 | { | |
493 | int r, full = 1; | |
494 | ||
495 | /* | |
496 | * Keeping reading chunks and inserting exceptions until | |
497 | * we find a partially full area. | |
498 | */ | |
499 | for (ps->current_area = 0; full; ps->current_area++) { | |
500 | r = area_io(ps, READ); | |
501 | if (r) | |
502 | return r; | |
503 | ||
504 | r = insert_exceptions(ps, callback, callback_context, &full); | |
505 | if (r) | |
506 | return r; | |
507 | } | |
508 | ||
509 | ps->current_area--; | |
510 | ||
511 | return 0; | |
512 | } | |
513 | ||
514 | static struct pstore *get_info(struct dm_exception_store *store) | |
515 | { | |
516 | return (struct pstore *) store->context; | |
517 | } | |
518 | ||
519 | static void persistent_usage(struct dm_exception_store *store, | |
520 | sector_t *total_sectors, | |
521 | sector_t *sectors_allocated, | |
522 | sector_t *metadata_sectors) | |
523 | { | |
524 | struct pstore *ps = get_info(store); | |
525 | ||
526 | *sectors_allocated = ps->next_free * store->chunk_size; | |
527 | *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev); | |
528 | ||
529 | /* | |
530 | * First chunk is the fixed header. | |
531 | * Then there are (ps->current_area + 1) metadata chunks, each one | |
532 | * separated from the next by ps->exceptions_per_area data chunks. | |
533 | */ | |
534 | *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) * | |
535 | store->chunk_size; | |
536 | } | |
537 | ||
538 | static void persistent_dtr(struct dm_exception_store *store) | |
539 | { | |
540 | struct pstore *ps = get_info(store); | |
541 | ||
542 | destroy_workqueue(ps->metadata_wq); | |
543 | ||
544 | /* Created in read_header */ | |
545 | if (ps->io_client) | |
546 | dm_io_client_destroy(ps->io_client); | |
547 | free_area(ps); | |
548 | ||
549 | /* Allocated in persistent_read_metadata */ | |
550 | if (ps->callbacks) | |
551 | vfree(ps->callbacks); | |
552 | ||
553 | kfree(ps); | |
554 | } | |
555 | ||
556 | static int persistent_read_metadata(struct dm_exception_store *store, | |
557 | int (*callback)(void *callback_context, | |
558 | chunk_t old, chunk_t new), | |
559 | void *callback_context) | |
560 | { | |
561 | int r, uninitialized_var(new_snapshot); | |
562 | struct pstore *ps = get_info(store); | |
563 | ||
564 | /* | |
565 | * Read the snapshot header. | |
566 | */ | |
567 | r = read_header(ps, &new_snapshot); | |
568 | if (r) | |
569 | return r; | |
570 | ||
571 | /* | |
572 | * Now we know correct chunk_size, complete the initialisation. | |
573 | */ | |
574 | ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) / | |
575 | sizeof(struct disk_exception); | |
576 | ps->callbacks = dm_vcalloc(ps->exceptions_per_area, | |
577 | sizeof(*ps->callbacks)); | |
578 | if (!ps->callbacks) | |
579 | return -ENOMEM; | |
580 | ||
581 | /* | |
582 | * Do we need to setup a new snapshot ? | |
583 | */ | |
584 | if (new_snapshot) { | |
585 | r = write_header(ps); | |
586 | if (r) { | |
587 | DMWARN("write_header failed"); | |
588 | return r; | |
589 | } | |
590 | ||
591 | ps->current_area = 0; | |
592 | zero_memory_area(ps); | |
593 | r = zero_disk_area(ps, 0); | |
594 | if (r) | |
595 | DMWARN("zero_disk_area(0) failed"); | |
596 | return r; | |
597 | } | |
598 | /* | |
599 | * Sanity checks. | |
600 | */ | |
601 | if (ps->version != SNAPSHOT_DISK_VERSION) { | |
602 | DMWARN("unable to handle snapshot disk version %d", | |
603 | ps->version); | |
604 | return -EINVAL; | |
605 | } | |
606 | ||
607 | /* | |
608 | * Metadata are valid, but snapshot is invalidated | |
609 | */ | |
610 | if (!ps->valid) | |
611 | return 1; | |
612 | ||
613 | /* | |
614 | * Read the metadata. | |
615 | */ | |
616 | r = read_exceptions(ps, callback, callback_context); | |
617 | ||
618 | return r; | |
619 | } | |
620 | ||
621 | static int persistent_prepare_exception(struct dm_exception_store *store, | |
622 | struct dm_exception *e) | |
623 | { | |
624 | struct pstore *ps = get_info(store); | |
625 | uint32_t stride; | |
626 | chunk_t next_free; | |
627 | sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev); | |
628 | ||
629 | /* Is there enough room ? */ | |
630 | if (size < ((ps->next_free + 1) * store->chunk_size)) | |
631 | return -ENOSPC; | |
632 | ||
633 | e->new_chunk = ps->next_free; | |
634 | ||
635 | /* | |
636 | * Move onto the next free pending, making sure to take | |
637 | * into account the location of the metadata chunks. | |
638 | */ | |
639 | stride = (ps->exceptions_per_area + 1); | |
640 | next_free = ++ps->next_free; | |
641 | if (sector_div(next_free, stride) == 1) | |
642 | ps->next_free++; | |
643 | ||
644 | atomic_inc(&ps->pending_count); | |
645 | return 0; | |
646 | } | |
647 | ||
648 | static void persistent_commit_exception(struct dm_exception_store *store, | |
649 | struct dm_exception *e, | |
650 | void (*callback) (void *, int success), | |
651 | void *callback_context) | |
652 | { | |
653 | unsigned int i; | |
654 | struct pstore *ps = get_info(store); | |
655 | struct disk_exception de; | |
656 | struct commit_callback *cb; | |
657 | ||
658 | de.old_chunk = e->old_chunk; | |
659 | de.new_chunk = e->new_chunk; | |
660 | write_exception(ps, ps->current_committed++, &de); | |
661 | ||
662 | /* | |
663 | * Add the callback to the back of the array. This code | |
664 | * is the only place where the callback array is | |
665 | * manipulated, and we know that it will never be called | |
666 | * multiple times concurrently. | |
667 | */ | |
668 | cb = ps->callbacks + ps->callback_count++; | |
669 | cb->callback = callback; | |
670 | cb->context = callback_context; | |
671 | ||
672 | /* | |
673 | * If there are exceptions in flight and we have not yet | |
674 | * filled this metadata area there's nothing more to do. | |
675 | */ | |
676 | if (!atomic_dec_and_test(&ps->pending_count) && | |
677 | (ps->current_committed != ps->exceptions_per_area)) | |
678 | return; | |
679 | ||
680 | /* | |
681 | * If we completely filled the current area, then wipe the next one. | |
682 | */ | |
683 | if ((ps->current_committed == ps->exceptions_per_area) && | |
684 | zero_disk_area(ps, ps->current_area + 1)) | |
685 | ps->valid = 0; | |
686 | ||
687 | /* | |
688 | * Commit exceptions to disk. | |
689 | */ | |
690 | if (ps->valid && area_io(ps, WRITE_BARRIER)) | |
691 | ps->valid = 0; | |
692 | ||
693 | /* | |
694 | * Advance to the next area if this one is full. | |
695 | */ | |
696 | if (ps->current_committed == ps->exceptions_per_area) { | |
697 | ps->current_committed = 0; | |
698 | ps->current_area++; | |
699 | zero_memory_area(ps); | |
700 | } | |
701 | ||
702 | for (i = 0; i < ps->callback_count; i++) { | |
703 | cb = ps->callbacks + i; | |
704 | cb->callback(cb->context, ps->valid); | |
705 | } | |
706 | ||
707 | ps->callback_count = 0; | |
708 | } | |
709 | ||
710 | static int persistent_prepare_merge(struct dm_exception_store *store, | |
711 | chunk_t *last_old_chunk, | |
712 | chunk_t *last_new_chunk) | |
713 | { | |
714 | struct pstore *ps = get_info(store); | |
715 | struct disk_exception de; | |
716 | int nr_consecutive; | |
717 | int r; | |
718 | ||
719 | /* | |
720 | * When current area is empty, move back to preceding area. | |
721 | */ | |
722 | if (!ps->current_committed) { | |
723 | /* | |
724 | * Have we finished? | |
725 | */ | |
726 | if (!ps->current_area) | |
727 | return 0; | |
728 | ||
729 | ps->current_area--; | |
730 | r = area_io(ps, READ); | |
731 | if (r < 0) | |
732 | return r; | |
733 | ps->current_committed = ps->exceptions_per_area; | |
734 | } | |
735 | ||
736 | read_exception(ps, ps->current_committed - 1, &de); | |
737 | *last_old_chunk = de.old_chunk; | |
738 | *last_new_chunk = de.new_chunk; | |
739 | ||
740 | /* | |
741 | * Find number of consecutive chunks within the current area, | |
742 | * working backwards. | |
743 | */ | |
744 | for (nr_consecutive = 1; nr_consecutive < ps->current_committed; | |
745 | nr_consecutive++) { | |
746 | read_exception(ps, ps->current_committed - 1 - nr_consecutive, | |
747 | &de); | |
748 | if (de.old_chunk != *last_old_chunk - nr_consecutive || | |
749 | de.new_chunk != *last_new_chunk - nr_consecutive) | |
750 | break; | |
751 | } | |
752 | ||
753 | return nr_consecutive; | |
754 | } | |
755 | ||
756 | static int persistent_commit_merge(struct dm_exception_store *store, | |
757 | int nr_merged) | |
758 | { | |
759 | int r, i; | |
760 | struct pstore *ps = get_info(store); | |
761 | ||
762 | BUG_ON(nr_merged > ps->current_committed); | |
763 | ||
764 | for (i = 0; i < nr_merged; i++) | |
765 | clear_exception(ps, ps->current_committed - 1 - i); | |
766 | ||
767 | r = area_io(ps, WRITE); | |
768 | if (r < 0) | |
769 | return r; | |
770 | ||
771 | ps->current_committed -= nr_merged; | |
772 | ||
773 | /* | |
774 | * At this stage, only persistent_usage() uses ps->next_free, so | |
775 | * we make no attempt to keep ps->next_free strictly accurate | |
776 | * as exceptions may have been committed out-of-order originally. | |
777 | * Once a snapshot has become merging, we set it to the value it | |
778 | * would have held had all the exceptions been committed in order. | |
779 | * | |
780 | * ps->current_area does not get reduced by prepare_merge() until | |
781 | * after commit_merge() has removed the nr_merged previous exceptions. | |
782 | */ | |
783 | ps->next_free = (area_location(ps, ps->current_area) - 1) + | |
784 | (ps->current_committed + 1) + NUM_SNAPSHOT_HDR_CHUNKS; | |
785 | ||
786 | return 0; | |
787 | } | |
788 | ||
789 | static void persistent_drop_snapshot(struct dm_exception_store *store) | |
790 | { | |
791 | struct pstore *ps = get_info(store); | |
792 | ||
793 | ps->valid = 0; | |
794 | if (write_header(ps)) | |
795 | DMWARN("write header failed"); | |
796 | } | |
797 | ||
798 | static int persistent_ctr(struct dm_exception_store *store, | |
799 | unsigned argc, char **argv) | |
800 | { | |
801 | struct pstore *ps; | |
802 | ||
803 | /* allocate the pstore */ | |
804 | ps = kzalloc(sizeof(*ps), GFP_KERNEL); | |
805 | if (!ps) | |
806 | return -ENOMEM; | |
807 | ||
808 | ps->store = store; | |
809 | ps->valid = 1; | |
810 | ps->version = SNAPSHOT_DISK_VERSION; | |
811 | ps->area = NULL; | |
812 | ps->zero_area = NULL; | |
813 | ps->header_area = NULL; | |
814 | ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */ | |
815 | ps->current_committed = 0; | |
816 | ||
817 | ps->callback_count = 0; | |
818 | atomic_set(&ps->pending_count, 0); | |
819 | ps->callbacks = NULL; | |
820 | ||
821 | ps->metadata_wq = create_singlethread_workqueue("ksnaphd"); | |
822 | if (!ps->metadata_wq) { | |
823 | kfree(ps); | |
824 | DMERR("couldn't start header metadata update thread"); | |
825 | return -ENOMEM; | |
826 | } | |
827 | ||
828 | store->context = ps; | |
829 | ||
830 | return 0; | |
831 | } | |
832 | ||
833 | static unsigned persistent_status(struct dm_exception_store *store, | |
834 | status_type_t status, char *result, | |
835 | unsigned maxlen) | |
836 | { | |
837 | unsigned sz = 0; | |
838 | ||
839 | switch (status) { | |
840 | case STATUSTYPE_INFO: | |
841 | break; | |
842 | case STATUSTYPE_TABLE: | |
843 | DMEMIT(" P %llu", (unsigned long long)store->chunk_size); | |
844 | } | |
845 | ||
846 | return sz; | |
847 | } | |
848 | ||
849 | static struct dm_exception_store_type _persistent_type = { | |
850 | .name = "persistent", | |
851 | .module = THIS_MODULE, | |
852 | .ctr = persistent_ctr, | |
853 | .dtr = persistent_dtr, | |
854 | .read_metadata = persistent_read_metadata, | |
855 | .prepare_exception = persistent_prepare_exception, | |
856 | .commit_exception = persistent_commit_exception, | |
857 | .prepare_merge = persistent_prepare_merge, | |
858 | .commit_merge = persistent_commit_merge, | |
859 | .drop_snapshot = persistent_drop_snapshot, | |
860 | .usage = persistent_usage, | |
861 | .status = persistent_status, | |
862 | }; | |
863 | ||
864 | static struct dm_exception_store_type _persistent_compat_type = { | |
865 | .name = "P", | |
866 | .module = THIS_MODULE, | |
867 | .ctr = persistent_ctr, | |
868 | .dtr = persistent_dtr, | |
869 | .read_metadata = persistent_read_metadata, | |
870 | .prepare_exception = persistent_prepare_exception, | |
871 | .commit_exception = persistent_commit_exception, | |
872 | .prepare_merge = persistent_prepare_merge, | |
873 | .commit_merge = persistent_commit_merge, | |
874 | .drop_snapshot = persistent_drop_snapshot, | |
875 | .usage = persistent_usage, | |
876 | .status = persistent_status, | |
877 | }; | |
878 | ||
879 | int dm_persistent_snapshot_init(void) | |
880 | { | |
881 | int r; | |
882 | ||
883 | r = dm_exception_store_type_register(&_persistent_type); | |
884 | if (r) { | |
885 | DMERR("Unable to register persistent exception store type"); | |
886 | return r; | |
887 | } | |
888 | ||
889 | r = dm_exception_store_type_register(&_persistent_compat_type); | |
890 | if (r) { | |
891 | DMERR("Unable to register old-style persistent exception " | |
892 | "store type"); | |
893 | dm_exception_store_type_unregister(&_persistent_type); | |
894 | return r; | |
895 | } | |
896 | ||
897 | return r; | |
898 | } | |
899 | ||
900 | void dm_persistent_snapshot_exit(void) | |
901 | { | |
902 | dm_exception_store_type_unregister(&_persistent_type); | |
903 | dm_exception_store_type_unregister(&_persistent_compat_type); | |
904 | } |