1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
4 | * Copyright (C) 2006-2008 Red Hat GmbH |
5 | * |
6 | * This file is released under the GPL. |
7 | */ |
8 | |
9 | #include "dm-exception-store.h" |
10 | |
11 | #include <linux/ctype.h> |
12 | #include <linux/mm.h> |
13 | #include <linux/pagemap.h> |
14 | #include <linux/vmalloc.h> |
15 | #include <linux/export.h> |
16 | #include <linux/slab.h> |
17 | #include <linux/dm-io.h> |
18 | #include <linux/dm-bufio.h> |
19 | |
20 | #define DM_MSG_PREFIX "persistent snapshot" |
21 | #define DM_CHUNK_SIZE_DEFAULT_SECTORS 32U /* 16KB */ |
22 | |
23 | #define DM_PREFETCH_CHUNKS 12 |
24 | |
25 | /* |
26 | *--------------------------------------------------------------- |
27 | * Persistent snapshots, by persistent we mean that the snapshot |
28 | * will survive a reboot. |
29 | *--------------------------------------------------------------- |
30 | */ |
31 | |
32 | /* |
33 | * We need to store a record of which parts of the origin have |
34 | * been copied to the snapshot device. The snapshot code |
35 | * requires that we copy exception chunks to chunk aligned areas |
36 | * of the COW store. It makes sense therefore, to store the |
37 | * metadata in chunk size blocks. |
38 | * |
39 | * There is no backward or forward compatibility implemented, |
40 | * snapshots with different disk versions than the kernel will |
41 | * not be usable. It is expected that "lvcreate" will blank out |
42 | * the start of a fresh COW device before calling the snapshot |
43 | * constructor. |
44 | * |
45 | * The first chunk of the COW device just contains the header. |
46 | * After this there is a chunk filled with exception metadata, |
47 | * followed by as many exception chunks as can fit in the |
48 | * metadata areas. |
49 | * |
50 | * All on disk structures are in little-endian format. The end |
51 | * of the exceptions info is indicated by an exception with a |
52 | * new_chunk of 0, which is invalid since it would point to the |
53 | * header chunk. |
54 | */ |
55 | |
56 | /* |
57 | * Magic for persistent snapshots: "SnAp" - Feeble isn't it. |
58 | */ |
59 | #define SNAP_MAGIC 0x70416e53 |
60 | |
61 | /* |
62 | * The on-disk version of the metadata. |
63 | */ |
64 | #define SNAPSHOT_DISK_VERSION 1 |
65 | |
66 | #define NUM_SNAPSHOT_HDR_CHUNKS 1 |
67 | |
68 | struct { |
69 | __le32 ; |
70 | |
71 | /* |
72 | * Is this snapshot valid. There is no way of recovering |
73 | * an invalid snapshot. |
74 | */ |
75 | __le32 ; |
76 | |
77 | /* |
78 | * Simple, incrementing version. no backward |
79 | * compatibility. |
80 | */ |
81 | __le32 ; |
82 | |
83 | /* In sectors */ |
84 | __le32 ; |
85 | } __packed; |
86 | |
87 | struct disk_exception { |
88 | __le64 old_chunk; |
89 | __le64 new_chunk; |
90 | } __packed; |
91 | |
92 | struct core_exception { |
93 | uint64_t old_chunk; |
94 | uint64_t new_chunk; |
95 | }; |
96 | |
97 | struct commit_callback { |
98 | void (*callback)(void *ref, int success); |
99 | void *context; |
100 | }; |
101 | |
102 | /* |
103 | * The top level structure for a persistent exception store. |
104 | */ |
105 | struct pstore { |
106 | struct dm_exception_store *store; |
107 | int version; |
108 | int valid; |
109 | uint32_t exceptions_per_area; |
110 | |
111 | /* |
112 | * Now that we have an asynchronous kcopyd there is no |
113 | * need for large chunk sizes, so it wont hurt to have a |
114 | * whole chunks worth of metadata in memory at once. |
115 | */ |
116 | void *area; |
117 | |
118 | /* |
119 | * An area of zeros used to clear the next area. |
120 | */ |
121 | void *zero_area; |
122 | |
123 | /* |
124 | * An area used for header. The header can be written |
125 | * concurrently with metadata (when invalidating the snapshot), |
126 | * so it needs a separate buffer. |
127 | */ |
128 | void *; |
129 | |
130 | /* |
131 | * Used to keep track of which metadata area the data in |
132 | * 'chunk' refers to. |
133 | */ |
134 | chunk_t current_area; |
135 | |
136 | /* |
137 | * The next free chunk for an exception. |
138 | * |
139 | * When creating exceptions, all the chunks here and above are |
140 | * free. It holds the next chunk to be allocated. On rare |
141 | * occasions (e.g. after a system crash) holes can be left in |
142 | * the exception store because chunks can be committed out of |
143 | * order. |
144 | * |
145 | * When merging exceptions, it does not necessarily mean all the |
146 | * chunks here and above are free. It holds the value it would |
147 | * have held if all chunks had been committed in order of |
148 | * allocation. Consequently the value may occasionally be |
149 | * slightly too low, but since it's only used for 'status' and |
150 | * it can never reach its minimum value too early this doesn't |
151 | * matter. |
152 | */ |
153 | |
154 | chunk_t next_free; |
155 | |
156 | /* |
157 | * The index of next free exception in the current |
158 | * metadata area. |
159 | */ |
160 | uint32_t current_committed; |
161 | |
162 | atomic_t pending_count; |
163 | uint32_t callback_count; |
164 | struct commit_callback *callbacks; |
165 | struct dm_io_client *io_client; |
166 | |
167 | struct workqueue_struct *metadata_wq; |
168 | }; |
169 | |
170 | static int alloc_area(struct pstore *ps) |
171 | { |
172 | int r = -ENOMEM; |
173 | size_t len; |
174 | |
175 | len = ps->store->chunk_size << SECTOR_SHIFT; |
176 | |
177 | /* |
178 | * Allocate the chunk_size block of memory that will hold |
179 | * a single metadata area. |
180 | */ |
181 | ps->area = vmalloc(size: len); |
182 | if (!ps->area) |
183 | goto err_area; |
184 | |
185 | ps->zero_area = vzalloc(size: len); |
186 | if (!ps->zero_area) |
187 | goto err_zero_area; |
188 | |
189 | ps->header_area = vmalloc(size: len); |
190 | if (!ps->header_area) |
191 | goto err_header_area; |
192 | |
193 | return 0; |
194 | |
195 | : |
196 | vfree(addr: ps->zero_area); |
197 | |
198 | err_zero_area: |
199 | vfree(addr: ps->area); |
200 | |
201 | err_area: |
202 | return r; |
203 | } |
204 | |
205 | static void free_area(struct pstore *ps) |
206 | { |
207 | vfree(addr: ps->area); |
208 | ps->area = NULL; |
209 | vfree(addr: ps->zero_area); |
210 | ps->zero_area = NULL; |
211 | vfree(addr: ps->header_area); |
212 | ps->header_area = NULL; |
213 | } |
214 | |
215 | struct mdata_req { |
216 | struct dm_io_region *where; |
217 | struct dm_io_request *io_req; |
218 | struct work_struct work; |
219 | int result; |
220 | }; |
221 | |
222 | static void do_metadata(struct work_struct *work) |
223 | { |
224 | struct mdata_req *req = container_of(work, struct mdata_req, work); |
225 | |
226 | req->result = dm_io(io_req: req->io_req, num_regions: 1, region: req->where, NULL); |
227 | } |
228 | |
229 | /* |
230 | * Read or write a chunk aligned and sized block of data from a device. |
231 | */ |
232 | static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, blk_opf_t opf, |
233 | int metadata) |
234 | { |
235 | struct dm_io_region where = { |
236 | .bdev = dm_snap_cow(snap: ps->store->snap)->bdev, |
237 | .sector = ps->store->chunk_size * chunk, |
238 | .count = ps->store->chunk_size, |
239 | }; |
240 | struct dm_io_request io_req = { |
241 | .bi_opf = opf, |
242 | .mem.type = DM_IO_VMA, |
243 | .mem.ptr.vma = area, |
244 | .client = ps->io_client, |
245 | .notify.fn = NULL, |
246 | }; |
247 | struct mdata_req req; |
248 | |
249 | if (!metadata) |
250 | return dm_io(io_req: &io_req, num_regions: 1, region: &where, NULL); |
251 | |
252 | req.where = &where; |
253 | req.io_req = &io_req; |
254 | |
255 | /* |
256 | * Issue the synchronous I/O from a different thread |
257 | * to avoid submit_bio_noacct recursion. |
258 | */ |
259 | INIT_WORK_ONSTACK(&req.work, do_metadata); |
260 | queue_work(wq: ps->metadata_wq, work: &req.work); |
261 | flush_workqueue(ps->metadata_wq); |
262 | destroy_work_on_stack(work: &req.work); |
263 | |
264 | return req.result; |
265 | } |
266 | |
267 | /* |
268 | * Convert a metadata area index to a chunk index. |
269 | */ |
270 | static chunk_t area_location(struct pstore *ps, chunk_t area) |
271 | { |
272 | return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area); |
273 | } |
274 | |
275 | static void skip_metadata(struct pstore *ps) |
276 | { |
277 | uint32_t stride = ps->exceptions_per_area + 1; |
278 | chunk_t next_free = ps->next_free; |
279 | |
280 | if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS) |
281 | ps->next_free++; |
282 | } |
283 | |
284 | /* |
285 | * Read or write a metadata area. Remembering to skip the first |
286 | * chunk which holds the header. |
287 | */ |
288 | static int area_io(struct pstore *ps, blk_opf_t opf) |
289 | { |
290 | chunk_t chunk = area_location(ps, area: ps->current_area); |
291 | |
292 | return chunk_io(ps, area: ps->area, chunk, opf, metadata: 0); |
293 | } |
294 | |
295 | static void zero_memory_area(struct pstore *ps) |
296 | { |
297 | memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT); |
298 | } |
299 | |
300 | static int zero_disk_area(struct pstore *ps, chunk_t area) |
301 | { |
302 | return chunk_io(ps, area: ps->zero_area, chunk: area_location(ps, area), |
303 | opf: REQ_OP_WRITE, metadata: 0); |
304 | } |
305 | |
306 | static int (struct pstore *ps, int *new_snapshot) |
307 | { |
308 | int r; |
309 | struct disk_header *dh; |
310 | unsigned int chunk_size; |
311 | int chunk_size_supplied = 1; |
312 | char *chunk_err; |
313 | |
314 | /* |
315 | * Use default chunk size (or logical_block_size, if larger) |
316 | * if none supplied |
317 | */ |
318 | if (!ps->store->chunk_size) { |
319 | ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS, |
320 | bdev_logical_block_size(dm_snap_cow(ps->store->snap)-> |
321 | bdev) >> 9); |
322 | ps->store->chunk_mask = ps->store->chunk_size - 1; |
323 | ps->store->chunk_shift = __ffs(ps->store->chunk_size); |
324 | chunk_size_supplied = 0; |
325 | } |
326 | |
327 | ps->io_client = dm_io_client_create(); |
328 | if (IS_ERR(ptr: ps->io_client)) |
329 | return PTR_ERR(ptr: ps->io_client); |
330 | |
331 | r = alloc_area(ps); |
332 | if (r) |
333 | return r; |
334 | |
335 | r = chunk_io(ps, area: ps->header_area, chunk: 0, opf: REQ_OP_READ, metadata: 1); |
336 | if (r) |
337 | goto bad; |
338 | |
339 | dh = ps->header_area; |
340 | |
341 | if (le32_to_cpu(dh->magic) == 0) { |
342 | *new_snapshot = 1; |
343 | return 0; |
344 | } |
345 | |
346 | if (le32_to_cpu(dh->magic) != SNAP_MAGIC) { |
347 | DMWARN("Invalid or corrupt snapshot" ); |
348 | r = -ENXIO; |
349 | goto bad; |
350 | } |
351 | |
352 | *new_snapshot = 0; |
353 | ps->valid = le32_to_cpu(dh->valid); |
354 | ps->version = le32_to_cpu(dh->version); |
355 | chunk_size = le32_to_cpu(dh->chunk_size); |
356 | |
357 | if (ps->store->chunk_size == chunk_size) |
358 | return 0; |
359 | |
360 | if (chunk_size_supplied) |
361 | DMWARN("chunk size %u in device metadata overrides table chunk size of %u." , |
362 | chunk_size, ps->store->chunk_size); |
363 | |
364 | /* We had a bogus chunk_size. Fix stuff up. */ |
365 | free_area(ps); |
366 | |
367 | r = dm_exception_store_set_chunk_size(store: ps->store, chunk_size, |
368 | error: &chunk_err); |
369 | if (r) { |
370 | DMERR("invalid on-disk chunk size %u: %s." , |
371 | chunk_size, chunk_err); |
372 | return r; |
373 | } |
374 | |
375 | r = alloc_area(ps); |
376 | return r; |
377 | |
378 | bad: |
379 | free_area(ps); |
380 | return r; |
381 | } |
382 | |
383 | static int (struct pstore *ps) |
384 | { |
385 | struct disk_header *dh; |
386 | |
387 | memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT); |
388 | |
389 | dh = ps->header_area; |
390 | dh->magic = cpu_to_le32(SNAP_MAGIC); |
391 | dh->valid = cpu_to_le32(ps->valid); |
392 | dh->version = cpu_to_le32(ps->version); |
393 | dh->chunk_size = cpu_to_le32(ps->store->chunk_size); |
394 | |
395 | return chunk_io(ps, area: ps->header_area, chunk: 0, opf: REQ_OP_WRITE, metadata: 1); |
396 | } |
397 | |
398 | /* |
399 | * Access functions for the disk exceptions, these do the endian conversions. |
400 | */ |
401 | static struct disk_exception *get_exception(struct pstore *ps, void *ps_area, |
402 | 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, void *ps_area, |
410 | uint32_t index, struct core_exception *result) |
411 | { |
412 | struct disk_exception *de = get_exception(ps, ps_area, index); |
413 | |
414 | /* copy it */ |
415 | result->old_chunk = le64_to_cpu(de->old_chunk); |
416 | result->new_chunk = le64_to_cpu(de->new_chunk); |
417 | } |
418 | |
419 | static void write_exception(struct pstore *ps, |
420 | uint32_t index, struct core_exception *e) |
421 | { |
422 | struct disk_exception *de = get_exception(ps, ps_area: ps->area, index); |
423 | |
424 | /* copy it */ |
425 | de->old_chunk = cpu_to_le64(e->old_chunk); |
426 | de->new_chunk = cpu_to_le64(e->new_chunk); |
427 | } |
428 | |
429 | static void clear_exception(struct pstore *ps, uint32_t index) |
430 | { |
431 | struct disk_exception *de = get_exception(ps, ps_area: ps->area, index); |
432 | |
433 | /* clear it */ |
434 | de->old_chunk = 0; |
435 | de->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, void *ps_area, |
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 core_exception e; |
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, ps_area, index: i, result: &e); |
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 (e.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 <= e.new_chunk) |
475 | ps->next_free = e.new_chunk + 1; |
476 | |
477 | /* |
478 | * Otherwise we add the exception to the snapshot. |
479 | */ |
480 | r = callback(callback_context, e.old_chunk, e.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 | struct dm_bufio_client *client; |
495 | chunk_t prefetch_area = 0; |
496 | |
497 | client = dm_bufio_client_create(bdev: dm_snap_cow(snap: ps->store->snap)->bdev, |
498 | block_size: ps->store->chunk_size << SECTOR_SHIFT, |
499 | reserved_buffers: 1, aux_size: 0, NULL, NULL, flags: 0); |
500 | |
501 | if (IS_ERR(ptr: client)) |
502 | return PTR_ERR(ptr: client); |
503 | |
504 | /* |
505 | * Setup for one current buffer + desired readahead buffers. |
506 | */ |
507 | dm_bufio_set_minimum_buffers(c: client, n: 1 + DM_PREFETCH_CHUNKS); |
508 | |
509 | /* |
510 | * Keeping reading chunks and inserting exceptions until |
511 | * we find a partially full area. |
512 | */ |
513 | for (ps->current_area = 0; full; ps->current_area++) { |
514 | struct dm_buffer *bp; |
515 | void *area; |
516 | chunk_t chunk; |
517 | |
518 | if (unlikely(prefetch_area < ps->current_area)) |
519 | prefetch_area = ps->current_area; |
520 | |
521 | if (DM_PREFETCH_CHUNKS) { |
522 | do { |
523 | chunk_t pf_chunk = area_location(ps, area: prefetch_area); |
524 | |
525 | if (unlikely(pf_chunk >= dm_bufio_get_device_size(client))) |
526 | break; |
527 | dm_bufio_prefetch(c: client, block: pf_chunk, n_blocks: 1); |
528 | prefetch_area++; |
529 | if (unlikely(!prefetch_area)) |
530 | break; |
531 | } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS); |
532 | } |
533 | |
534 | chunk = area_location(ps, area: ps->current_area); |
535 | |
536 | area = dm_bufio_read(c: client, block: chunk, bp: &bp); |
537 | if (IS_ERR(ptr: area)) { |
538 | r = PTR_ERR(ptr: area); |
539 | goto ret_destroy_bufio; |
540 | } |
541 | |
542 | r = insert_exceptions(ps, ps_area: area, callback, callback_context, |
543 | full: &full); |
544 | |
545 | if (!full) |
546 | memcpy(ps->area, area, ps->store->chunk_size << SECTOR_SHIFT); |
547 | |
548 | dm_bufio_release(b: bp); |
549 | |
550 | dm_bufio_forget(c: client, block: chunk); |
551 | |
552 | if (unlikely(r)) |
553 | goto ret_destroy_bufio; |
554 | } |
555 | |
556 | ps->current_area--; |
557 | |
558 | skip_metadata(ps); |
559 | |
560 | r = 0; |
561 | |
562 | ret_destroy_bufio: |
563 | dm_bufio_client_destroy(c: client); |
564 | |
565 | return r; |
566 | } |
567 | |
568 | static struct pstore *get_info(struct dm_exception_store *store) |
569 | { |
570 | return store->context; |
571 | } |
572 | |
573 | static void persistent_usage(struct dm_exception_store *store, |
574 | sector_t *total_sectors, |
575 | sector_t *sectors_allocated, |
576 | sector_t *metadata_sectors) |
577 | { |
578 | struct pstore *ps = get_info(store); |
579 | |
580 | *sectors_allocated = ps->next_free * store->chunk_size; |
581 | *total_sectors = get_dev_size(bdev: dm_snap_cow(snap: store->snap)->bdev); |
582 | |
583 | /* |
584 | * First chunk is the fixed header. |
585 | * Then there are (ps->current_area + 1) metadata chunks, each one |
586 | * separated from the next by ps->exceptions_per_area data chunks. |
587 | */ |
588 | *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) * |
589 | store->chunk_size; |
590 | } |
591 | |
592 | static void persistent_dtr(struct dm_exception_store *store) |
593 | { |
594 | struct pstore *ps = get_info(store); |
595 | |
596 | destroy_workqueue(wq: ps->metadata_wq); |
597 | |
598 | /* Created in read_header */ |
599 | if (ps->io_client) |
600 | dm_io_client_destroy(client: ps->io_client); |
601 | free_area(ps); |
602 | |
603 | /* Allocated in persistent_read_metadata */ |
604 | kvfree(addr: ps->callbacks); |
605 | |
606 | kfree(objp: ps); |
607 | } |
608 | |
609 | static int persistent_read_metadata(struct dm_exception_store *store, |
610 | int (*callback)(void *callback_context, |
611 | chunk_t old, chunk_t new), |
612 | void *callback_context) |
613 | { |
614 | int r, new_snapshot; |
615 | struct pstore *ps = get_info(store); |
616 | |
617 | /* |
618 | * Read the snapshot header. |
619 | */ |
620 | r = read_header(ps, new_snapshot: &new_snapshot); |
621 | if (r) |
622 | return r; |
623 | |
624 | /* |
625 | * Now we know correct chunk_size, complete the initialisation. |
626 | */ |
627 | ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) / |
628 | sizeof(struct disk_exception); |
629 | ps->callbacks = kvcalloc(n: ps->exceptions_per_area, |
630 | size: sizeof(*ps->callbacks), GFP_KERNEL); |
631 | if (!ps->callbacks) |
632 | return -ENOMEM; |
633 | |
634 | /* |
635 | * Do we need to setup a new snapshot ? |
636 | */ |
637 | if (new_snapshot) { |
638 | r = write_header(ps); |
639 | if (r) { |
640 | DMWARN("write_header failed" ); |
641 | return r; |
642 | } |
643 | |
644 | ps->current_area = 0; |
645 | zero_memory_area(ps); |
646 | r = zero_disk_area(ps, area: 0); |
647 | if (r) |
648 | DMWARN("zero_disk_area(0) failed" ); |
649 | return r; |
650 | } |
651 | /* |
652 | * Sanity checks. |
653 | */ |
654 | if (ps->version != SNAPSHOT_DISK_VERSION) { |
655 | DMWARN("unable to handle snapshot disk version %d" , |
656 | ps->version); |
657 | return -EINVAL; |
658 | } |
659 | |
660 | /* |
661 | * Metadata are valid, but snapshot is invalidated |
662 | */ |
663 | if (!ps->valid) |
664 | return 1; |
665 | |
666 | /* |
667 | * Read the metadata. |
668 | */ |
669 | r = read_exceptions(ps, callback, callback_context); |
670 | |
671 | return r; |
672 | } |
673 | |
674 | static int persistent_prepare_exception(struct dm_exception_store *store, |
675 | struct dm_exception *e) |
676 | { |
677 | struct pstore *ps = get_info(store); |
678 | sector_t size = get_dev_size(bdev: dm_snap_cow(snap: store->snap)->bdev); |
679 | |
680 | /* Is there enough room ? */ |
681 | if (size < ((ps->next_free + 1) * store->chunk_size)) |
682 | return -ENOSPC; |
683 | |
684 | e->new_chunk = ps->next_free; |
685 | |
686 | /* |
687 | * Move onto the next free pending, making sure to take |
688 | * into account the location of the metadata chunks. |
689 | */ |
690 | ps->next_free++; |
691 | skip_metadata(ps); |
692 | |
693 | atomic_inc(v: &ps->pending_count); |
694 | return 0; |
695 | } |
696 | |
697 | static void persistent_commit_exception(struct dm_exception_store *store, |
698 | struct dm_exception *e, int valid, |
699 | void (*callback)(void *, int success), |
700 | void *callback_context) |
701 | { |
702 | unsigned int i; |
703 | struct pstore *ps = get_info(store); |
704 | struct core_exception ce; |
705 | struct commit_callback *cb; |
706 | |
707 | if (!valid) |
708 | ps->valid = 0; |
709 | |
710 | ce.old_chunk = e->old_chunk; |
711 | ce.new_chunk = e->new_chunk; |
712 | write_exception(ps, index: ps->current_committed++, e: &ce); |
713 | |
714 | /* |
715 | * Add the callback to the back of the array. This code |
716 | * is the only place where the callback array is |
717 | * manipulated, and we know that it will never be called |
718 | * multiple times concurrently. |
719 | */ |
720 | cb = ps->callbacks + ps->callback_count++; |
721 | cb->callback = callback; |
722 | cb->context = callback_context; |
723 | |
724 | /* |
725 | * If there are exceptions in flight and we have not yet |
726 | * filled this metadata area there's nothing more to do. |
727 | */ |
728 | if (!atomic_dec_and_test(v: &ps->pending_count) && |
729 | (ps->current_committed != ps->exceptions_per_area)) |
730 | return; |
731 | |
732 | /* |
733 | * If we completely filled the current area, then wipe the next one. |
734 | */ |
735 | if ((ps->current_committed == ps->exceptions_per_area) && |
736 | zero_disk_area(ps, area: ps->current_area + 1)) |
737 | ps->valid = 0; |
738 | |
739 | /* |
740 | * Commit exceptions to disk. |
741 | */ |
742 | if (ps->valid && area_io(ps, opf: REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA | |
743 | REQ_SYNC)) |
744 | ps->valid = 0; |
745 | |
746 | /* |
747 | * Advance to the next area if this one is full. |
748 | */ |
749 | if (ps->current_committed == ps->exceptions_per_area) { |
750 | ps->current_committed = 0; |
751 | ps->current_area++; |
752 | zero_memory_area(ps); |
753 | } |
754 | |
755 | for (i = 0; i < ps->callback_count; i++) { |
756 | cb = ps->callbacks + i; |
757 | cb->callback(cb->context, ps->valid); |
758 | } |
759 | |
760 | ps->callback_count = 0; |
761 | } |
762 | |
763 | static int persistent_prepare_merge(struct dm_exception_store *store, |
764 | chunk_t *last_old_chunk, |
765 | chunk_t *last_new_chunk) |
766 | { |
767 | struct pstore *ps = get_info(store); |
768 | struct core_exception ce; |
769 | int nr_consecutive; |
770 | int r; |
771 | |
772 | /* |
773 | * When current area is empty, move back to preceding area. |
774 | */ |
775 | if (!ps->current_committed) { |
776 | /* |
777 | * Have we finished? |
778 | */ |
779 | if (!ps->current_area) |
780 | return 0; |
781 | |
782 | ps->current_area--; |
783 | r = area_io(ps, opf: REQ_OP_READ); |
784 | if (r < 0) |
785 | return r; |
786 | ps->current_committed = ps->exceptions_per_area; |
787 | } |
788 | |
789 | read_exception(ps, ps_area: ps->area, index: ps->current_committed - 1, result: &ce); |
790 | *last_old_chunk = ce.old_chunk; |
791 | *last_new_chunk = ce.new_chunk; |
792 | |
793 | /* |
794 | * Find number of consecutive chunks within the current area, |
795 | * working backwards. |
796 | */ |
797 | for (nr_consecutive = 1; nr_consecutive < ps->current_committed; |
798 | nr_consecutive++) { |
799 | read_exception(ps, ps_area: ps->area, |
800 | index: ps->current_committed - 1 - nr_consecutive, result: &ce); |
801 | if (ce.old_chunk != *last_old_chunk - nr_consecutive || |
802 | ce.new_chunk != *last_new_chunk - nr_consecutive) |
803 | break; |
804 | } |
805 | |
806 | return nr_consecutive; |
807 | } |
808 | |
809 | static int persistent_commit_merge(struct dm_exception_store *store, |
810 | int nr_merged) |
811 | { |
812 | int r, i; |
813 | struct pstore *ps = get_info(store); |
814 | |
815 | BUG_ON(nr_merged > ps->current_committed); |
816 | |
817 | for (i = 0; i < nr_merged; i++) |
818 | clear_exception(ps, index: ps->current_committed - 1 - i); |
819 | |
820 | r = area_io(ps, opf: REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA); |
821 | if (r < 0) |
822 | return r; |
823 | |
824 | ps->current_committed -= nr_merged; |
825 | |
826 | /* |
827 | * At this stage, only persistent_usage() uses ps->next_free, so |
828 | * we make no attempt to keep ps->next_free strictly accurate |
829 | * as exceptions may have been committed out-of-order originally. |
830 | * Once a snapshot has become merging, we set it to the value it |
831 | * would have held had all the exceptions been committed in order. |
832 | * |
833 | * ps->current_area does not get reduced by prepare_merge() until |
834 | * after commit_merge() has removed the nr_merged previous exceptions. |
835 | */ |
836 | ps->next_free = area_location(ps, area: ps->current_area) + |
837 | ps->current_committed + 1; |
838 | |
839 | return 0; |
840 | } |
841 | |
842 | static void persistent_drop_snapshot(struct dm_exception_store *store) |
843 | { |
844 | struct pstore *ps = get_info(store); |
845 | |
846 | ps->valid = 0; |
847 | if (write_header(ps)) |
848 | DMWARN("write header failed" ); |
849 | } |
850 | |
851 | static int persistent_ctr(struct dm_exception_store *store, char *options) |
852 | { |
853 | struct pstore *ps; |
854 | int r; |
855 | |
856 | /* allocate the pstore */ |
857 | ps = kzalloc(size: sizeof(*ps), GFP_KERNEL); |
858 | if (!ps) |
859 | return -ENOMEM; |
860 | |
861 | ps->store = store; |
862 | ps->valid = 1; |
863 | ps->version = SNAPSHOT_DISK_VERSION; |
864 | ps->area = NULL; |
865 | ps->zero_area = NULL; |
866 | ps->header_area = NULL; |
867 | ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */ |
868 | ps->current_committed = 0; |
869 | |
870 | ps->callback_count = 0; |
871 | atomic_set(v: &ps->pending_count, i: 0); |
872 | ps->callbacks = NULL; |
873 | |
874 | ps->metadata_wq = alloc_workqueue(fmt: "ksnaphd" , flags: WQ_MEM_RECLAIM, max_active: 0); |
875 | if (!ps->metadata_wq) { |
876 | DMERR("couldn't start header metadata update thread" ); |
877 | r = -ENOMEM; |
878 | goto err_workqueue; |
879 | } |
880 | |
881 | if (options) { |
882 | char overflow = toupper(options[0]); |
883 | |
884 | if (overflow == 'O') |
885 | store->userspace_supports_overflow = true; |
886 | else { |
887 | DMERR("Unsupported persistent store option: %s" , options); |
888 | r = -EINVAL; |
889 | goto err_options; |
890 | } |
891 | } |
892 | |
893 | store->context = ps; |
894 | |
895 | return 0; |
896 | |
897 | err_options: |
898 | destroy_workqueue(wq: ps->metadata_wq); |
899 | err_workqueue: |
900 | kfree(objp: ps); |
901 | |
902 | return r; |
903 | } |
904 | |
905 | static unsigned int persistent_status(struct dm_exception_store *store, |
906 | status_type_t status, char *result, |
907 | unsigned int maxlen) |
908 | { |
909 | unsigned int sz = 0; |
910 | |
911 | switch (status) { |
912 | case STATUSTYPE_INFO: |
913 | break; |
914 | case STATUSTYPE_TABLE: |
915 | DMEMIT(" %s %llu" , store->userspace_supports_overflow ? "PO" : "P" , |
916 | (unsigned long long)store->chunk_size); |
917 | break; |
918 | case STATUSTYPE_IMA: |
919 | *result = '\0'; |
920 | break; |
921 | } |
922 | |
923 | return sz; |
924 | } |
925 | |
926 | static struct dm_exception_store_type _persistent_type = { |
927 | .name = "persistent" , |
928 | .module = THIS_MODULE, |
929 | .ctr = persistent_ctr, |
930 | .dtr = persistent_dtr, |
931 | .read_metadata = persistent_read_metadata, |
932 | .prepare_exception = persistent_prepare_exception, |
933 | .commit_exception = persistent_commit_exception, |
934 | .prepare_merge = persistent_prepare_merge, |
935 | .commit_merge = persistent_commit_merge, |
936 | .drop_snapshot = persistent_drop_snapshot, |
937 | .usage = persistent_usage, |
938 | .status = persistent_status, |
939 | }; |
940 | |
941 | static struct dm_exception_store_type _persistent_compat_type = { |
942 | .name = "P" , |
943 | .module = THIS_MODULE, |
944 | .ctr = persistent_ctr, |
945 | .dtr = persistent_dtr, |
946 | .read_metadata = persistent_read_metadata, |
947 | .prepare_exception = persistent_prepare_exception, |
948 | .commit_exception = persistent_commit_exception, |
949 | .prepare_merge = persistent_prepare_merge, |
950 | .commit_merge = persistent_commit_merge, |
951 | .drop_snapshot = persistent_drop_snapshot, |
952 | .usage = persistent_usage, |
953 | .status = persistent_status, |
954 | }; |
955 | |
956 | int dm_persistent_snapshot_init(void) |
957 | { |
958 | int r; |
959 | |
960 | r = dm_exception_store_type_register(type: &_persistent_type); |
961 | if (r) { |
962 | DMERR("Unable to register persistent exception store type" ); |
963 | return r; |
964 | } |
965 | |
966 | r = dm_exception_store_type_register(type: &_persistent_compat_type); |
967 | if (r) { |
968 | DMERR("Unable to register old-style persistent exception store type" ); |
969 | dm_exception_store_type_unregister(type: &_persistent_type); |
970 | return r; |
971 | } |
972 | |
973 | return r; |
974 | } |
975 | |
976 | void dm_persistent_snapshot_exit(void) |
977 | { |
978 | dm_exception_store_type_unregister(type: &_persistent_type); |
979 | dm_exception_store_type_unregister(type: &_persistent_compat_type); |
980 | } |
981 | |