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Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +00001/*
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"
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +00009
Mike Snitzerb0d3cc02015-10-08 18:05:41 -040010#include <linux/ctype.h>
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000011#include <linux/mm.h>
12#include <linux/pagemap.h>
13#include <linux/vmalloc.h>
Paul Gortmakerdaaa5f72011-05-27 15:50:58 -040014#include <linux/export.h>
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000015#include <linux/slab.h>
16#include <linux/dm-io.h>
Mikulas Patockaafa53df2018-03-15 16:02:31 -040017#include <linux/dm-bufio.h>
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000018
19#define DM_MSG_PREFIX "persistent snapshot"
Mikulas Patockaad6bf882020-01-15 08:35:25 -050020#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32U /* 16KB */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000021
Mikulas Patocka55b082e2014-01-13 19:13:05 -050022#define DM_PREFETCH_CHUNKS 12
23
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000024/*-----------------------------------------------------------------
25 * Persistent snapshots, by persistent we mean that the snapshot
26 * will survive a reboot.
27 *---------------------------------------------------------------*/
28
29/*
30 * We need to store a record of which parts of the origin have
31 * been copied to the snapshot device. The snapshot code
32 * requires that we copy exception chunks to chunk aligned areas
33 * of the COW store. It makes sense therefore, to store the
34 * metadata in chunk size blocks.
35 *
36 * There is no backward or forward compatibility implemented,
37 * snapshots with different disk versions than the kernel will
38 * not be usable. It is expected that "lvcreate" will blank out
39 * the start of a fresh COW device before calling the snapshot
40 * constructor.
41 *
42 * The first chunk of the COW device just contains the header.
43 * After this there is a chunk filled with exception metadata,
44 * followed by as many exception chunks as can fit in the
45 * metadata areas.
46 *
47 * All on disk structures are in little-endian format. The end
48 * of the exceptions info is indicated by an exception with a
49 * new_chunk of 0, which is invalid since it would point to the
50 * header chunk.
51 */
52
53/*
54 * Magic for persistent snapshots: "SnAp" - Feeble isn't it.
55 */
56#define SNAP_MAGIC 0x70416e53
57
58/*
59 * The on-disk version of the metadata.
60 */
61#define SNAPSHOT_DISK_VERSION 1
62
Mikulas Patocka4454a622009-12-10 23:52:29 +000063#define NUM_SNAPSHOT_HDR_CHUNKS 1
64
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000065struct disk_header {
Alasdair G Kergon283a8322011-08-02 12:32:01 +010066 __le32 magic;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000067
68 /*
69 * Is this snapshot valid. There is no way of recovering
70 * an invalid snapshot.
71 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010072 __le32 valid;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000073
74 /*
75 * Simple, incrementing version. no backward
76 * compatibility.
77 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010078 __le32 version;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000079
80 /* In sectors */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010081 __le32 chunk_size;
82} __packed;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000083
84struct disk_exception {
Alasdair G Kergon283a8322011-08-02 12:32:01 +010085 __le64 old_chunk;
86 __le64 new_chunk;
87} __packed;
88
89struct core_exception {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000090 uint64_t old_chunk;
91 uint64_t new_chunk;
92};
93
94struct commit_callback {
95 void (*callback)(void *, int success);
96 void *context;
97};
98
99/*
100 * The top level structure for a persistent exception store.
101 */
102struct pstore {
Jonathan Brassow71fab002009-04-02 19:55:33 +0100103 struct dm_exception_store *store;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000104 int version;
105 int valid;
106 uint32_t exceptions_per_area;
107
108 /*
109 * Now that we have an asynchronous kcopyd there is no
110 * need for large chunk sizes, so it wont hurt to have a
111 * whole chunks worth of metadata in memory at once.
112 */
113 void *area;
114
115 /*
116 * An area of zeros used to clear the next area.
117 */
118 void *zero_area;
119
120 /*
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100121 * An area used for header. The header can be written
122 * concurrently with metadata (when invalidating the snapshot),
123 * so it needs a separate buffer.
124 */
125 void *header_area;
126
127 /*
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000128 * Used to keep track of which metadata area the data in
129 * 'chunk' refers to.
130 */
131 chunk_t current_area;
132
133 /*
134 * The next free chunk for an exception.
Mikulas Patocka4454a622009-12-10 23:52:29 +0000135 *
136 * When creating exceptions, all the chunks here and above are
137 * free. It holds the next chunk to be allocated. On rare
138 * occasions (e.g. after a system crash) holes can be left in
139 * the exception store because chunks can be committed out of
140 * order.
141 *
142 * When merging exceptions, it does not necessarily mean all the
143 * chunks here and above are free. It holds the value it would
144 * have held if all chunks had been committed in order of
145 * allocation. Consequently the value may occasionally be
146 * slightly too low, but since it's only used for 'status' and
147 * it can never reach its minimum value too early this doesn't
148 * matter.
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000149 */
Mikulas Patocka4454a622009-12-10 23:52:29 +0000150
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000151 chunk_t next_free;
152
153 /*
154 * The index of next free exception in the current
155 * metadata area.
156 */
157 uint32_t current_committed;
158
159 atomic_t pending_count;
160 uint32_t callback_count;
161 struct commit_callback *callbacks;
162 struct dm_io_client *io_client;
163
164 struct workqueue_struct *metadata_wq;
165};
166
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000167static int alloc_area(struct pstore *ps)
168{
169 int r = -ENOMEM;
170 size_t len;
171
Jonathan Brassow71fab002009-04-02 19:55:33 +0100172 len = ps->store->chunk_size << SECTOR_SHIFT;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000173
174 /*
175 * Allocate the chunk_size block of memory that will hold
176 * a single metadata area.
177 */
178 ps->area = vmalloc(len);
179 if (!ps->area)
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100180 goto err_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000181
Joe Perchese29e65a2011-08-02 12:32:02 +0100182 ps->zero_area = vzalloc(len);
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100183 if (!ps->zero_area)
184 goto err_zero_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000185
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100186 ps->header_area = vmalloc(len);
187 if (!ps->header_area)
188 goto err_header_area;
189
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000190 return 0;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100191
192err_header_area:
193 vfree(ps->zero_area);
194
195err_zero_area:
196 vfree(ps->area);
197
198err_area:
199 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000200}
201
202static void free_area(struct pstore *ps)
203{
Markus Elfring0c8f8632015-02-02 14:38:29 +0100204 vfree(ps->area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000205 ps->area = NULL;
Markus Elfring0c8f8632015-02-02 14:38:29 +0100206 vfree(ps->zero_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000207 ps->zero_area = NULL;
Markus Elfring0c8f8632015-02-02 14:38:29 +0100208 vfree(ps->header_area);
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100209 ps->header_area = NULL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000210}
211
212struct mdata_req {
213 struct dm_io_region *where;
214 struct dm_io_request *io_req;
215 struct work_struct work;
216 int result;
217};
218
219static void do_metadata(struct work_struct *work)
220{
221 struct mdata_req *req = container_of(work, struct mdata_req, work);
222
223 req->result = dm_io(req->io_req, 1, req->where, NULL);
224}
225
226/*
227 * Read or write a chunk aligned and sized block of data from a device.
228 */
Bart Van Assche6b990132022-07-14 11:06:54 -0700229static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, blk_opf_t opf,
230 int metadata)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000231{
232 struct dm_io_region where = {
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000233 .bdev = dm_snap_cow(ps->store->snap)->bdev,
Jonathan Brassow71fab002009-04-02 19:55:33 +0100234 .sector = ps->store->chunk_size * chunk,
235 .count = ps->store->chunk_size,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000236 };
237 struct dm_io_request io_req = {
Bart Van Assche6b990132022-07-14 11:06:54 -0700238 .bi_opf = opf,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000239 .mem.type = DM_IO_VMA,
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100240 .mem.ptr.vma = area,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000241 .client = ps->io_client,
242 .notify.fn = NULL,
243 };
244 struct mdata_req req;
245
246 if (!metadata)
247 return dm_io(&io_req, 1, &where, NULL);
248
249 req.where = &where;
250 req.io_req = &io_req;
251
252 /*
253 * Issue the synchronous I/O from a different thread
Christoph Hellwiged00aab2020-07-01 10:59:44 +0200254 * to avoid submit_bio_noacct recursion.
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000255 */
Andrew Mortonca1cab32010-10-26 14:22:34 -0700256 INIT_WORK_ONSTACK(&req.work, do_metadata);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000257 queue_work(ps->metadata_wq, &req.work);
Mikulas Patocka5ea330a2013-09-18 19:14:22 -0400258 flush_workqueue(ps->metadata_wq);
Chuansheng Liuc1a64162014-01-07 16:56:18 +0800259 destroy_work_on_stack(&req.work);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000260
261 return req.result;
262}
263
264/*
265 * Convert a metadata area index to a chunk index.
266 */
267static chunk_t area_location(struct pstore *ps, chunk_t area)
268{
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100269 return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000270}
271
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100272static void skip_metadata(struct pstore *ps)
273{
274 uint32_t stride = ps->exceptions_per_area + 1;
275 chunk_t next_free = ps->next_free;
276 if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS)
277 ps->next_free++;
278}
279
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000280/*
281 * Read or write a metadata area. Remembering to skip the first
282 * chunk which holds the header.
283 */
Bart Van Assche6b990132022-07-14 11:06:54 -0700284static int area_io(struct pstore *ps, blk_opf_t opf)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000285{
Qinglang Miao7d837c02020-09-21 21:10:10 +0800286 chunk_t chunk = area_location(ps, ps->current_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000287
Bart Van Assche6b990132022-07-14 11:06:54 -0700288 return chunk_io(ps, ps->area, chunk, opf, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000289}
290
291static void zero_memory_area(struct pstore *ps)
292{
Jonathan Brassow71fab002009-04-02 19:55:33 +0100293 memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000294}
295
296static int zero_disk_area(struct pstore *ps, chunk_t area)
297{
Mike Christiee6047142016-06-05 14:32:04 -0500298 return chunk_io(ps, ps->zero_area, area_location(ps, area),
Bart Van Assche6b990132022-07-14 11:06:54 -0700299 REQ_OP_WRITE, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000300}
301
302static int read_header(struct pstore *ps, int *new_snapshot)
303{
304 int r;
305 struct disk_header *dh;
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100306 unsigned chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000307 int chunk_size_supplied = 1;
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100308 char *chunk_err;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000309
310 /*
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100311 * Use default chunk size (or logical_block_size, if larger)
312 * if none supplied
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000313 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100314 if (!ps->store->chunk_size) {
315 ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000316 bdev_logical_block_size(dm_snap_cow(ps->store->snap)->
317 bdev) >> 9);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100318 ps->store->chunk_mask = ps->store->chunk_size - 1;
Mikulas Patockaa3d939a2015-10-02 11:21:24 -0400319 ps->store->chunk_shift = __ffs(ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000320 chunk_size_supplied = 0;
321 }
322
Mikulas Patockabda8efe2011-05-29 13:03:09 +0100323 ps->io_client = dm_io_client_create();
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000324 if (IS_ERR(ps->io_client))
325 return PTR_ERR(ps->io_client);
326
327 r = alloc_area(ps);
328 if (r)
329 return r;
330
Bart Van Assche6b990132022-07-14 11:06:54 -0700331 r = chunk_io(ps, ps->header_area, 0, REQ_OP_READ, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000332 if (r)
333 goto bad;
334
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100335 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000336
337 if (le32_to_cpu(dh->magic) == 0) {
338 *new_snapshot = 1;
339 return 0;
340 }
341
342 if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
343 DMWARN("Invalid or corrupt snapshot");
344 r = -ENXIO;
345 goto bad;
346 }
347
348 *new_snapshot = 0;
349 ps->valid = le32_to_cpu(dh->valid);
350 ps->version = le32_to_cpu(dh->version);
351 chunk_size = le32_to_cpu(dh->chunk_size);
352
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100353 if (ps->store->chunk_size == chunk_size)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000354 return 0;
355
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100356 if (chunk_size_supplied)
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100357 DMWARN("chunk size %u in device metadata overrides "
358 "table chunk size of %u.",
359 chunk_size, ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000360
361 /* We had a bogus chunk_size. Fix stuff up. */
362 free_area(ps);
363
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100364 r = dm_exception_store_set_chunk_size(ps->store, chunk_size,
365 &chunk_err);
366 if (r) {
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100367 DMERR("invalid on-disk chunk size %u: %s.",
368 chunk_size, chunk_err);
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100369 return r;
370 }
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000371
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000372 r = alloc_area(ps);
373 return r;
374
375bad:
376 free_area(ps);
377 return r;
378}
379
380static int write_header(struct pstore *ps)
381{
382 struct disk_header *dh;
383
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100384 memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000385
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100386 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000387 dh->magic = cpu_to_le32(SNAP_MAGIC);
388 dh->valid = cpu_to_le32(ps->valid);
389 dh->version = cpu_to_le32(ps->version);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100390 dh->chunk_size = cpu_to_le32(ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000391
Bart Van Assche6b990132022-07-14 11:06:54 -0700392 return chunk_io(ps, ps->header_area, 0, REQ_OP_WRITE, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000393}
394
395/*
396 * Access functions for the disk exceptions, these do the endian conversions.
397 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500398static struct disk_exception *get_exception(struct pstore *ps, void *ps_area,
399 uint32_t index)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000400{
401 BUG_ON(index >= ps->exceptions_per_area);
402
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500403 return ((struct disk_exception *) ps_area) + index;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000404}
405
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500406static void read_exception(struct pstore *ps, void *ps_area,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100407 uint32_t index, struct core_exception *result)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000408{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500409 struct disk_exception *de = get_exception(ps, ps_area, index);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000410
411 /* copy it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100412 result->old_chunk = le64_to_cpu(de->old_chunk);
413 result->new_chunk = le64_to_cpu(de->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000414}
415
416static void write_exception(struct pstore *ps,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100417 uint32_t index, struct core_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000418{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500419 struct disk_exception *de = get_exception(ps, ps->area, index);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000420
421 /* copy it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100422 de->old_chunk = cpu_to_le64(e->old_chunk);
423 de->new_chunk = cpu_to_le64(e->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000424}
425
Mikulas Patocka4454a622009-12-10 23:52:29 +0000426static void clear_exception(struct pstore *ps, uint32_t index)
427{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500428 struct disk_exception *de = get_exception(ps, ps->area, index);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000429
430 /* clear it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100431 de->old_chunk = 0;
432 de->new_chunk = 0;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000433}
434
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000435/*
436 * Registers the exceptions that are present in the current area.
437 * 'full' is filled in to indicate if the area has been
438 * filled.
439 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500440static int insert_exceptions(struct pstore *ps, void *ps_area,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000441 int (*callback)(void *callback_context,
442 chunk_t old, chunk_t new),
443 void *callback_context,
444 int *full)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000445{
446 int r;
447 unsigned int i;
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100448 struct core_exception e;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000449
450 /* presume the area is full */
451 *full = 1;
452
453 for (i = 0; i < ps->exceptions_per_area; i++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500454 read_exception(ps, ps_area, i, &e);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000455
456 /*
457 * If the new_chunk is pointing at the start of
458 * the COW device, where the first metadata area
459 * is we know that we've hit the end of the
460 * exceptions. Therefore the area is not full.
461 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100462 if (e.new_chunk == 0LL) {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000463 ps->current_committed = i;
464 *full = 0;
465 break;
466 }
467
468 /*
469 * Keep track of the start of the free chunks.
470 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100471 if (ps->next_free <= e.new_chunk)
472 ps->next_free = e.new_chunk + 1;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000473
474 /*
475 * Otherwise we add the exception to the snapshot.
476 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100477 r = callback(callback_context, e.old_chunk, e.new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000478 if (r)
479 return r;
480 }
481
482 return 0;
483}
484
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000485static int read_exceptions(struct pstore *ps,
486 int (*callback)(void *callback_context, chunk_t old,
487 chunk_t new),
488 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000489{
490 int r, full = 1;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500491 struct dm_bufio_client *client;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500492 chunk_t prefetch_area = 0;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500493
494 client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev,
495 ps->store->chunk_size << SECTOR_SHIFT,
Nathan Huckleberry0fcb1002022-07-22 09:38:21 +0000496 1, 0, NULL, NULL, 0);
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500497
498 if (IS_ERR(client))
499 return PTR_ERR(client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000500
501 /*
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500502 * Setup for one current buffer + desired readahead buffers.
503 */
504 dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS);
505
506 /*
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000507 * Keeping reading chunks and inserting exceptions until
508 * we find a partially full area.
509 */
510 for (ps->current_area = 0; full; ps->current_area++) {
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500511 struct dm_buffer *bp;
512 void *area;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500513 chunk_t chunk;
514
515 if (unlikely(prefetch_area < ps->current_area))
516 prefetch_area = ps->current_area;
517
518 if (DM_PREFETCH_CHUNKS) do {
519 chunk_t pf_chunk = area_location(ps, prefetch_area);
520 if (unlikely(pf_chunk >= dm_bufio_get_device_size(client)))
521 break;
522 dm_bufio_prefetch(client, pf_chunk, 1);
523 prefetch_area++;
524 if (unlikely(!prefetch_area))
525 break;
526 } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS);
527
528 chunk = area_location(ps, ps->current_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000529
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500530 area = dm_bufio_read(client, chunk, &bp);
viresh kumarfc0a4462015-08-10 11:42:26 +0530531 if (IS_ERR(area)) {
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500532 r = PTR_ERR(area);
533 goto ret_destroy_bufio;
534 }
535
536 r = insert_exceptions(ps, area, callback, callback_context,
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500537 &full);
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500538
Mikulas Patocka2c945822014-03-03 17:19:22 -0500539 if (!full)
540 memcpy(ps->area, area, ps->store->chunk_size << SECTOR_SHIFT);
541
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500542 dm_bufio_release(bp);
543
544 dm_bufio_forget(client, chunk);
545
546 if (unlikely(r))
547 goto ret_destroy_bufio;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000548 }
549
550 ps->current_area--;
551
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100552 skip_metadata(ps);
553
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500554 r = 0;
555
556ret_destroy_bufio:
557 dm_bufio_client_destroy(client);
558
559 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000560}
561
562static struct pstore *get_info(struct dm_exception_store *store)
563{
564 return (struct pstore *) store->context;
565}
566
Mike Snitzer985903b2009-12-10 23:52:11 +0000567static void persistent_usage(struct dm_exception_store *store,
568 sector_t *total_sectors,
569 sector_t *sectors_allocated,
570 sector_t *metadata_sectors)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000571{
Mike Snitzer985903b2009-12-10 23:52:11 +0000572 struct pstore *ps = get_info(store);
573
574 *sectors_allocated = ps->next_free * store->chunk_size;
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000575 *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
Mike Snitzer985903b2009-12-10 23:52:11 +0000576
577 /*
578 * First chunk is the fixed header.
579 * Then there are (ps->current_area + 1) metadata chunks, each one
580 * separated from the next by ps->exceptions_per_area data chunks.
581 */
Mikulas Patocka4454a622009-12-10 23:52:29 +0000582 *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) *
583 store->chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000584}
585
Jonathan Brassow493df712009-04-02 19:55:31 +0100586static void persistent_dtr(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000587{
588 struct pstore *ps = get_info(store);
589
590 destroy_workqueue(ps->metadata_wq);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100591
592 /* Created in read_header */
593 if (ps->io_client)
594 dm_io_client_destroy(ps->io_client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000595 free_area(ps);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100596
597 /* Allocated in persistent_read_metadata */
Matthew Wilcox (Oracle)7a356932021-04-07 14:25:22 +0100598 kvfree(ps->callbacks);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100599
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000600 kfree(ps);
601}
602
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000603static int persistent_read_metadata(struct dm_exception_store *store,
604 int (*callback)(void *callback_context,
605 chunk_t old, chunk_t new),
606 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000607{
Kees Cook3f649ab2020-06-03 13:09:38 -0700608 int r, new_snapshot;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000609 struct pstore *ps = get_info(store);
610
611 /*
612 * Read the snapshot header.
613 */
614 r = read_header(ps, &new_snapshot);
615 if (r)
616 return r;
617
618 /*
619 * Now we know correct chunk_size, complete the initialisation.
620 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100621 ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) /
622 sizeof(struct disk_exception);
Matthew Wilcox (Oracle)7a356932021-04-07 14:25:22 +0100623 ps->callbacks = kvcalloc(ps->exceptions_per_area,
624 sizeof(*ps->callbacks), GFP_KERNEL);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000625 if (!ps->callbacks)
626 return -ENOMEM;
627
628 /*
629 * Do we need to setup a new snapshot ?
630 */
631 if (new_snapshot) {
632 r = write_header(ps);
633 if (r) {
634 DMWARN("write_header failed");
635 return r;
636 }
637
638 ps->current_area = 0;
639 zero_memory_area(ps);
640 r = zero_disk_area(ps, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000641 if (r)
Jon Brassowf5acc832009-12-10 23:52:07 +0000642 DMWARN("zero_disk_area(0) failed");
643 return r;
644 }
645 /*
646 * Sanity checks.
647 */
648 if (ps->version != SNAPSHOT_DISK_VERSION) {
649 DMWARN("unable to handle snapshot disk version %d",
650 ps->version);
651 return -EINVAL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000652 }
653
Jon Brassowf5acc832009-12-10 23:52:07 +0000654 /*
655 * Metadata are valid, but snapshot is invalidated
656 */
657 if (!ps->valid)
658 return 1;
659
660 /*
661 * Read the metadata.
662 */
663 r = read_exceptions(ps, callback, callback_context);
664
665 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000666}
667
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000668static int persistent_prepare_exception(struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +0000669 struct dm_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000670{
671 struct pstore *ps = get_info(store);
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000672 sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000673
674 /* Is there enough room ? */
Jonathan Brassowd0216842009-04-02 19:55:32 +0100675 if (size < ((ps->next_free + 1) * store->chunk_size))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000676 return -ENOSPC;
677
678 e->new_chunk = ps->next_free;
679
680 /*
681 * Move onto the next free pending, making sure to take
682 * into account the location of the metadata chunks.
683 */
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100684 ps->next_free++;
685 skip_metadata(ps);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000686
687 atomic_inc(&ps->pending_count);
688 return 0;
689}
690
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000691static void persistent_commit_exception(struct dm_exception_store *store,
Mikulas Patocka385277b2016-01-08 19:07:55 -0500692 struct dm_exception *e, int valid,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000693 void (*callback) (void *, int success),
694 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000695{
696 unsigned int i;
697 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100698 struct core_exception ce;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000699 struct commit_callback *cb;
700
Mikulas Patocka385277b2016-01-08 19:07:55 -0500701 if (!valid)
702 ps->valid = 0;
703
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100704 ce.old_chunk = e->old_chunk;
705 ce.new_chunk = e->new_chunk;
706 write_exception(ps, ps->current_committed++, &ce);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000707
708 /*
709 * Add the callback to the back of the array. This code
710 * is the only place where the callback array is
711 * manipulated, and we know that it will never be called
712 * multiple times concurrently.
713 */
714 cb = ps->callbacks + ps->callback_count++;
715 cb->callback = callback;
716 cb->context = callback_context;
717
718 /*
719 * If there are exceptions in flight and we have not yet
720 * filled this metadata area there's nothing more to do.
721 */
722 if (!atomic_dec_and_test(&ps->pending_count) &&
723 (ps->current_committed != ps->exceptions_per_area))
724 return;
725
726 /*
727 * If we completely filled the current area, then wipe the next one.
728 */
729 if ((ps->current_committed == ps->exceptions_per_area) &&
Jonathan Brassowa2d2b032011-08-02 12:32:03 +0100730 zero_disk_area(ps, ps->current_area + 1))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000731 ps->valid = 0;
732
733 /*
734 * Commit exceptions to disk.
735 */
Bart Van Assche6b990132022-07-14 11:06:54 -0700736 if (ps->valid && area_io(ps, REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA |
737 REQ_SYNC))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000738 ps->valid = 0;
739
740 /*
741 * Advance to the next area if this one is full.
742 */
743 if (ps->current_committed == ps->exceptions_per_area) {
744 ps->current_committed = 0;
745 ps->current_area++;
746 zero_memory_area(ps);
747 }
748
749 for (i = 0; i < ps->callback_count; i++) {
750 cb = ps->callbacks + i;
751 cb->callback(cb->context, ps->valid);
752 }
753
754 ps->callback_count = 0;
755}
756
Mikulas Patocka4454a622009-12-10 23:52:29 +0000757static int persistent_prepare_merge(struct dm_exception_store *store,
758 chunk_t *last_old_chunk,
759 chunk_t *last_new_chunk)
760{
761 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100762 struct core_exception ce;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000763 int nr_consecutive;
764 int r;
765
766 /*
767 * When current area is empty, move back to preceding area.
768 */
769 if (!ps->current_committed) {
770 /*
771 * Have we finished?
772 */
773 if (!ps->current_area)
774 return 0;
775
776 ps->current_area--;
Bart Van Assche6b990132022-07-14 11:06:54 -0700777 r = area_io(ps, REQ_OP_READ);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000778 if (r < 0)
779 return r;
780 ps->current_committed = ps->exceptions_per_area;
781 }
782
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500783 read_exception(ps, ps->area, ps->current_committed - 1, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100784 *last_old_chunk = ce.old_chunk;
785 *last_new_chunk = ce.new_chunk;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000786
787 /*
788 * Find number of consecutive chunks within the current area,
789 * working backwards.
790 */
791 for (nr_consecutive = 1; nr_consecutive < ps->current_committed;
792 nr_consecutive++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500793 read_exception(ps, ps->area,
794 ps->current_committed - 1 - nr_consecutive, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100795 if (ce.old_chunk != *last_old_chunk - nr_consecutive ||
796 ce.new_chunk != *last_new_chunk - nr_consecutive)
Mikulas Patocka4454a622009-12-10 23:52:29 +0000797 break;
798 }
799
800 return nr_consecutive;
801}
802
803static int persistent_commit_merge(struct dm_exception_store *store,
804 int nr_merged)
805{
806 int r, i;
807 struct pstore *ps = get_info(store);
808
809 BUG_ON(nr_merged > ps->current_committed);
810
811 for (i = 0; i < nr_merged; i++)
812 clear_exception(ps, ps->current_committed - 1 - i);
813
Bart Van Assche6b990132022-07-14 11:06:54 -0700814 r = area_io(ps, REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000815 if (r < 0)
816 return r;
817
818 ps->current_committed -= nr_merged;
819
820 /*
821 * At this stage, only persistent_usage() uses ps->next_free, so
822 * we make no attempt to keep ps->next_free strictly accurate
823 * as exceptions may have been committed out-of-order originally.
824 * Once a snapshot has become merging, we set it to the value it
825 * would have held had all the exceptions been committed in order.
826 *
827 * ps->current_area does not get reduced by prepare_merge() until
828 * after commit_merge() has removed the nr_merged previous exceptions.
829 */
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100830 ps->next_free = area_location(ps, ps->current_area) +
831 ps->current_committed + 1;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000832
833 return 0;
834}
835
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000836static void persistent_drop_snapshot(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000837{
838 struct pstore *ps = get_info(store);
839
840 ps->valid = 0;
841 if (write_header(ps))
842 DMWARN("write header failed");
843}
844
Mike Snitzerb0d3cc02015-10-08 18:05:41 -0400845static int persistent_ctr(struct dm_exception_store *store, char *options)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000846{
847 struct pstore *ps;
Sudip Mukherjeea2a678e2015-10-13 13:33:08 +0530848 int r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000849
850 /* allocate the pstore */
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100851 ps = kzalloc(sizeof(*ps), GFP_KERNEL);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000852 if (!ps)
853 return -ENOMEM;
854
Jonathan Brassow71fab002009-04-02 19:55:33 +0100855 ps->store = store;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000856 ps->valid = 1;
857 ps->version = SNAPSHOT_DISK_VERSION;
858 ps->area = NULL;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100859 ps->zero_area = NULL;
860 ps->header_area = NULL;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000861 ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000862 ps->current_committed = 0;
863
864 ps->callback_count = 0;
865 atomic_set(&ps->pending_count, 0);
866 ps->callbacks = NULL;
867
Tejun Heo239c8dd2011-01-13 19:59:59 +0000868 ps->metadata_wq = alloc_workqueue("ksnaphd", WQ_MEM_RECLAIM, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000869 if (!ps->metadata_wq) {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000870 DMERR("couldn't start header metadata update thread");
Sudip Mukherjeea2a678e2015-10-13 13:33:08 +0530871 r = -ENOMEM;
872 goto err_workqueue;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000873 }
874
Mike Snitzerb0d3cc02015-10-08 18:05:41 -0400875 if (options) {
876 char overflow = toupper(options[0]);
877 if (overflow == 'O')
878 store->userspace_supports_overflow = true;
879 else {
880 DMERR("Unsupported persistent store option: %s", options);
Sudip Mukherjeea2a678e2015-10-13 13:33:08 +0530881 r = -EINVAL;
882 goto err_options;
Mike Snitzerb0d3cc02015-10-08 18:05:41 -0400883 }
884 }
885
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000886 store->context = ps;
887
888 return 0;
Sudip Mukherjeea2a678e2015-10-13 13:33:08 +0530889
890err_options:
891 destroy_workqueue(ps->metadata_wq);
892err_workqueue:
893 kfree(ps);
894
895 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000896}
897
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100898static unsigned persistent_status(struct dm_exception_store *store,
899 status_type_t status, char *result,
900 unsigned maxlen)
Jonathan Brassow493df712009-04-02 19:55:31 +0100901{
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100902 unsigned sz = 0;
903
904 switch (status) {
905 case STATUSTYPE_INFO:
906 break;
907 case STATUSTYPE_TABLE:
Mike Snitzerb0d3cc02015-10-08 18:05:41 -0400908 DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P",
909 (unsigned long long)store->chunk_size);
Tushar Sugandhi8ec45662021-07-12 17:49:03 -0700910 break;
911 case STATUSTYPE_IMA:
912 *result = '\0';
913 break;
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100914 }
Jonathan Brassow493df712009-04-02 19:55:31 +0100915
916 return sz;
917}
918
919static struct dm_exception_store_type _persistent_type = {
920 .name = "persistent",
921 .module = THIS_MODULE,
922 .ctr = persistent_ctr,
923 .dtr = persistent_dtr,
924 .read_metadata = persistent_read_metadata,
925 .prepare_exception = persistent_prepare_exception,
926 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000927 .prepare_merge = persistent_prepare_merge,
928 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100929 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000930 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100931 .status = persistent_status,
932};
933
934static struct dm_exception_store_type _persistent_compat_type = {
935 .name = "P",
936 .module = THIS_MODULE,
937 .ctr = persistent_ctr,
938 .dtr = persistent_dtr,
939 .read_metadata = persistent_read_metadata,
940 .prepare_exception = persistent_prepare_exception,
941 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000942 .prepare_merge = persistent_prepare_merge,
943 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100944 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000945 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100946 .status = persistent_status,
947};
948
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000949int dm_persistent_snapshot_init(void)
950{
Jonathan Brassow493df712009-04-02 19:55:31 +0100951 int r;
952
953 r = dm_exception_store_type_register(&_persistent_type);
954 if (r) {
955 DMERR("Unable to register persistent exception store type");
956 return r;
957 }
958
959 r = dm_exception_store_type_register(&_persistent_compat_type);
960 if (r) {
961 DMERR("Unable to register old-style persistent exception "
962 "store type");
963 dm_exception_store_type_unregister(&_persistent_type);
964 return r;
965 }
966
967 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000968}
969
970void dm_persistent_snapshot_exit(void)
971{
Jonathan Brassow493df712009-04-02 19:55:31 +0100972 dm_exception_store_type_unregister(&_persistent_type);
973 dm_exception_store_type_unregister(&_persistent_compat_type);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000974}