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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
10#include <linux/mm.h>
11#include <linux/pagemap.h>
12#include <linux/vmalloc.h>
Paul Gortmakerdaaa5f72011-05-27 15:50:58 -040013#include <linux/export.h>
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000014#include <linux/slab.h>
15#include <linux/dm-io.h>
Mikulas Patocka55494bf2014-01-13 19:12:36 -050016#include "dm-bufio.h"
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000017
18#define DM_MSG_PREFIX "persistent snapshot"
19#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */
20
Mikulas Patocka55b082e2014-01-13 19:13:05 -050021#define DM_PREFETCH_CHUNKS 12
22
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000023/*-----------------------------------------------------------------
24 * Persistent snapshots, by persistent we mean that the snapshot
25 * will survive a reboot.
26 *---------------------------------------------------------------*/
27
28/*
29 * We need to store a record of which parts of the origin have
30 * been copied to the snapshot device. The snapshot code
31 * requires that we copy exception chunks to chunk aligned areas
32 * of the COW store. It makes sense therefore, to store the
33 * metadata in chunk size blocks.
34 *
35 * There is no backward or forward compatibility implemented,
36 * snapshots with different disk versions than the kernel will
37 * not be usable. It is expected that "lvcreate" will blank out
38 * the start of a fresh COW device before calling the snapshot
39 * constructor.
40 *
41 * The first chunk of the COW device just contains the header.
42 * After this there is a chunk filled with exception metadata,
43 * followed by as many exception chunks as can fit in the
44 * metadata areas.
45 *
46 * All on disk structures are in little-endian format. The end
47 * of the exceptions info is indicated by an exception with a
48 * new_chunk of 0, which is invalid since it would point to the
49 * header chunk.
50 */
51
52/*
53 * Magic for persistent snapshots: "SnAp" - Feeble isn't it.
54 */
55#define SNAP_MAGIC 0x70416e53
56
57/*
58 * The on-disk version of the metadata.
59 */
60#define SNAPSHOT_DISK_VERSION 1
61
Mikulas Patocka4454a622009-12-10 23:52:29 +000062#define NUM_SNAPSHOT_HDR_CHUNKS 1
63
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000064struct disk_header {
Alasdair G Kergon283a8322011-08-02 12:32:01 +010065 __le32 magic;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000066
67 /*
68 * Is this snapshot valid. There is no way of recovering
69 * an invalid snapshot.
70 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010071 __le32 valid;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000072
73 /*
74 * Simple, incrementing version. no backward
75 * compatibility.
76 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010077 __le32 version;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000078
79 /* In sectors */
Alasdair G Kergon283a8322011-08-02 12:32:01 +010080 __le32 chunk_size;
81} __packed;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000082
83struct disk_exception {
Alasdair G Kergon283a8322011-08-02 12:32:01 +010084 __le64 old_chunk;
85 __le64 new_chunk;
86} __packed;
87
88struct core_exception {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000089 uint64_t old_chunk;
90 uint64_t new_chunk;
91};
92
93struct commit_callback {
94 void (*callback)(void *, int success);
95 void *context;
96};
97
98/*
99 * The top level structure for a persistent exception store.
100 */
101struct pstore {
Jonathan Brassow71fab002009-04-02 19:55:33 +0100102 struct dm_exception_store *store;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000103 int version;
104 int valid;
105 uint32_t exceptions_per_area;
106
107 /*
108 * Now that we have an asynchronous kcopyd there is no
109 * need for large chunk sizes, so it wont hurt to have a
110 * whole chunks worth of metadata in memory at once.
111 */
112 void *area;
113
114 /*
115 * An area of zeros used to clear the next area.
116 */
117 void *zero_area;
118
119 /*
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100120 * An area used for header. The header can be written
121 * concurrently with metadata (when invalidating the snapshot),
122 * so it needs a separate buffer.
123 */
124 void *header_area;
125
126 /*
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000127 * Used to keep track of which metadata area the data in
128 * 'chunk' refers to.
129 */
130 chunk_t current_area;
131
132 /*
133 * The next free chunk for an exception.
Mikulas Patocka4454a622009-12-10 23:52:29 +0000134 *
135 * When creating exceptions, all the chunks here and above are
136 * free. It holds the next chunk to be allocated. On rare
137 * occasions (e.g. after a system crash) holes can be left in
138 * the exception store because chunks can be committed out of
139 * order.
140 *
141 * When merging exceptions, it does not necessarily mean all the
142 * chunks here and above are free. It holds the value it would
143 * have held if all chunks had been committed in order of
144 * allocation. Consequently the value may occasionally be
145 * slightly too low, but since it's only used for 'status' and
146 * it can never reach its minimum value too early this doesn't
147 * matter.
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000148 */
Mikulas Patocka4454a622009-12-10 23:52:29 +0000149
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000150 chunk_t next_free;
151
152 /*
153 * The index of next free exception in the current
154 * metadata area.
155 */
156 uint32_t current_committed;
157
158 atomic_t pending_count;
159 uint32_t callback_count;
160 struct commit_callback *callbacks;
161 struct dm_io_client *io_client;
162
163 struct workqueue_struct *metadata_wq;
164};
165
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000166static int alloc_area(struct pstore *ps)
167{
168 int r = -ENOMEM;
169 size_t len;
170
Jonathan Brassow71fab002009-04-02 19:55:33 +0100171 len = ps->store->chunk_size << SECTOR_SHIFT;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000172
173 /*
174 * Allocate the chunk_size block of memory that will hold
175 * a single metadata area.
176 */
177 ps->area = vmalloc(len);
178 if (!ps->area)
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100179 goto err_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000180
Joe Perchese29e65a2011-08-02 12:32:02 +0100181 ps->zero_area = vzalloc(len);
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100182 if (!ps->zero_area)
183 goto err_zero_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000184
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100185 ps->header_area = vmalloc(len);
186 if (!ps->header_area)
187 goto err_header_area;
188
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000189 return 0;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100190
191err_header_area:
192 vfree(ps->zero_area);
193
194err_zero_area:
195 vfree(ps->area);
196
197err_area:
198 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000199}
200
201static void free_area(struct pstore *ps)
202{
Markus Elfring0c8f8632015-02-02 14:38:29 +0100203 vfree(ps->area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000204 ps->area = NULL;
Markus Elfring0c8f8632015-02-02 14:38:29 +0100205 vfree(ps->zero_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000206 ps->zero_area = NULL;
Markus Elfring0c8f8632015-02-02 14:38:29 +0100207 vfree(ps->header_area);
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100208 ps->header_area = NULL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000209}
210
211struct mdata_req {
212 struct dm_io_region *where;
213 struct dm_io_request *io_req;
214 struct work_struct work;
215 int result;
216};
217
218static void do_metadata(struct work_struct *work)
219{
220 struct mdata_req *req = container_of(work, struct mdata_req, work);
221
222 req->result = dm_io(req->io_req, 1, req->where, NULL);
223}
224
225/*
226 * Read or write a chunk aligned and sized block of data from a device.
227 */
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100228static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw,
229 int metadata)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000230{
231 struct dm_io_region where = {
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000232 .bdev = dm_snap_cow(ps->store->snap)->bdev,
Jonathan Brassow71fab002009-04-02 19:55:33 +0100233 .sector = ps->store->chunk_size * chunk,
234 .count = ps->store->chunk_size,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000235 };
236 struct dm_io_request io_req = {
237 .bi_rw = rw,
238 .mem.type = DM_IO_VMA,
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100239 .mem.ptr.vma = area,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000240 .client = ps->io_client,
241 .notify.fn = NULL,
242 };
243 struct mdata_req req;
244
245 if (!metadata)
246 return dm_io(&io_req, 1, &where, NULL);
247
248 req.where = &where;
249 req.io_req = &io_req;
250
251 /*
252 * Issue the synchronous I/O from a different thread
253 * to avoid generic_make_request recursion.
254 */
Andrew Mortonca1cab32010-10-26 14:22:34 -0700255 INIT_WORK_ONSTACK(&req.work, do_metadata);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000256 queue_work(ps->metadata_wq, &req.work);
Mikulas Patocka5ea330a2013-09-18 19:14:22 -0400257 flush_workqueue(ps->metadata_wq);
Chuansheng Liuc1a64162014-01-07 16:56:18 +0800258 destroy_work_on_stack(&req.work);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000259
260 return req.result;
261}
262
263/*
264 * Convert a metadata area index to a chunk index.
265 */
266static chunk_t area_location(struct pstore *ps, chunk_t area)
267{
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100268 return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000269}
270
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100271static void skip_metadata(struct pstore *ps)
272{
273 uint32_t stride = ps->exceptions_per_area + 1;
274 chunk_t next_free = ps->next_free;
275 if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS)
276 ps->next_free++;
277}
278
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000279/*
280 * Read or write a metadata area. Remembering to skip the first
281 * chunk which holds the header.
282 */
283static int area_io(struct pstore *ps, int rw)
284{
285 int r;
286 chunk_t chunk;
287
288 chunk = area_location(ps, ps->current_area);
289
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100290 r = chunk_io(ps, ps->area, chunk, rw, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000291 if (r)
292 return r;
293
294 return 0;
295}
296
297static void zero_memory_area(struct pstore *ps)
298{
Jonathan Brassow71fab002009-04-02 19:55:33 +0100299 memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000300}
301
302static int zero_disk_area(struct pstore *ps, chunk_t area)
303{
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100304 return chunk_io(ps, ps->zero_area, area_location(ps, area), WRITE, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000305}
306
307static int read_header(struct pstore *ps, int *new_snapshot)
308{
309 int r;
310 struct disk_header *dh;
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100311 unsigned chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000312 int chunk_size_supplied = 1;
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100313 char *chunk_err;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000314
315 /*
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100316 * Use default chunk size (or logical_block_size, if larger)
317 * if none supplied
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000318 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100319 if (!ps->store->chunk_size) {
320 ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000321 bdev_logical_block_size(dm_snap_cow(ps->store->snap)->
322 bdev) >> 9);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100323 ps->store->chunk_mask = ps->store->chunk_size - 1;
324 ps->store->chunk_shift = ffs(ps->store->chunk_size) - 1;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000325 chunk_size_supplied = 0;
326 }
327
Mikulas Patockabda8efe2011-05-29 13:03:09 +0100328 ps->io_client = dm_io_client_create();
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000329 if (IS_ERR(ps->io_client))
330 return PTR_ERR(ps->io_client);
331
332 r = alloc_area(ps);
333 if (r)
334 return r;
335
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100336 r = chunk_io(ps, ps->header_area, 0, READ, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000337 if (r)
338 goto bad;
339
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100340 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000341
342 if (le32_to_cpu(dh->magic) == 0) {
343 *new_snapshot = 1;
344 return 0;
345 }
346
347 if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
348 DMWARN("Invalid or corrupt snapshot");
349 r = -ENXIO;
350 goto bad;
351 }
352
353 *new_snapshot = 0;
354 ps->valid = le32_to_cpu(dh->valid);
355 ps->version = le32_to_cpu(dh->version);
356 chunk_size = le32_to_cpu(dh->chunk_size);
357
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100358 if (ps->store->chunk_size == chunk_size)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000359 return 0;
360
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100361 if (chunk_size_supplied)
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100362 DMWARN("chunk size %u in device metadata overrides "
363 "table chunk size of %u.",
364 chunk_size, ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000365
366 /* We had a bogus chunk_size. Fix stuff up. */
367 free_area(ps);
368
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100369 r = dm_exception_store_set_chunk_size(ps->store, chunk_size,
370 &chunk_err);
371 if (r) {
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100372 DMERR("invalid on-disk chunk size %u: %s.",
373 chunk_size, chunk_err);
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100374 return r;
375 }
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000376
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000377 r = alloc_area(ps);
378 return r;
379
380bad:
381 free_area(ps);
382 return r;
383}
384
385static int write_header(struct pstore *ps)
386{
387 struct disk_header *dh;
388
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100389 memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000390
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100391 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000392 dh->magic = cpu_to_le32(SNAP_MAGIC);
393 dh->valid = cpu_to_le32(ps->valid);
394 dh->version = cpu_to_le32(ps->version);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100395 dh->chunk_size = cpu_to_le32(ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000396
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100397 return chunk_io(ps, ps->header_area, 0, WRITE, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000398}
399
400/*
401 * Access functions for the disk exceptions, these do the endian conversions.
402 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500403static struct disk_exception *get_exception(struct pstore *ps, void *ps_area,
404 uint32_t index)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000405{
406 BUG_ON(index >= ps->exceptions_per_area);
407
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500408 return ((struct disk_exception *) ps_area) + index;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000409}
410
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500411static void read_exception(struct pstore *ps, void *ps_area,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100412 uint32_t index, struct core_exception *result)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000413{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500414 struct disk_exception *de = get_exception(ps, ps_area, index);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000415
416 /* copy it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100417 result->old_chunk = le64_to_cpu(de->old_chunk);
418 result->new_chunk = le64_to_cpu(de->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000419}
420
421static void write_exception(struct pstore *ps,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100422 uint32_t index, struct core_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000423{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500424 struct disk_exception *de = get_exception(ps, ps->area, index);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000425
426 /* copy it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100427 de->old_chunk = cpu_to_le64(e->old_chunk);
428 de->new_chunk = cpu_to_le64(e->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000429}
430
Mikulas Patocka4454a622009-12-10 23:52:29 +0000431static void clear_exception(struct pstore *ps, uint32_t index)
432{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500433 struct disk_exception *de = get_exception(ps, ps->area, index);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000434
435 /* clear it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100436 de->old_chunk = 0;
437 de->new_chunk = 0;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000438}
439
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000440/*
441 * Registers the exceptions that are present in the current area.
442 * 'full' is filled in to indicate if the area has been
443 * filled.
444 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500445static int insert_exceptions(struct pstore *ps, void *ps_area,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000446 int (*callback)(void *callback_context,
447 chunk_t old, chunk_t new),
448 void *callback_context,
449 int *full)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000450{
451 int r;
452 unsigned int i;
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100453 struct core_exception e;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000454
455 /* presume the area is full */
456 *full = 1;
457
458 for (i = 0; i < ps->exceptions_per_area; i++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500459 read_exception(ps, ps_area, i, &e);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000460
461 /*
462 * If the new_chunk is pointing at the start of
463 * the COW device, where the first metadata area
464 * is we know that we've hit the end of the
465 * exceptions. Therefore the area is not full.
466 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100467 if (e.new_chunk == 0LL) {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000468 ps->current_committed = i;
469 *full = 0;
470 break;
471 }
472
473 /*
474 * Keep track of the start of the free chunks.
475 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100476 if (ps->next_free <= e.new_chunk)
477 ps->next_free = e.new_chunk + 1;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000478
479 /*
480 * Otherwise we add the exception to the snapshot.
481 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100482 r = callback(callback_context, e.old_chunk, e.new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000483 if (r)
484 return r;
485 }
486
487 return 0;
488}
489
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000490static int read_exceptions(struct pstore *ps,
491 int (*callback)(void *callback_context, chunk_t old,
492 chunk_t new),
493 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000494{
495 int r, full = 1;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500496 struct dm_bufio_client *client;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500497 chunk_t prefetch_area = 0;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500498
499 client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev,
500 ps->store->chunk_size << SECTOR_SHIFT,
501 1, 0, NULL, NULL);
502
503 if (IS_ERR(client))
504 return PTR_ERR(client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000505
506 /*
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500507 * Setup for one current buffer + desired readahead buffers.
508 */
509 dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS);
510
511 /*
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000512 * Keeping reading chunks and inserting exceptions until
513 * we find a partially full area.
514 */
515 for (ps->current_area = 0; full; ps->current_area++) {
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500516 struct dm_buffer *bp;
517 void *area;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500518 chunk_t chunk;
519
520 if (unlikely(prefetch_area < ps->current_area))
521 prefetch_area = ps->current_area;
522
523 if (DM_PREFETCH_CHUNKS) do {
524 chunk_t pf_chunk = area_location(ps, prefetch_area);
525 if (unlikely(pf_chunk >= dm_bufio_get_device_size(client)))
526 break;
527 dm_bufio_prefetch(client, pf_chunk, 1);
528 prefetch_area++;
529 if (unlikely(!prefetch_area))
530 break;
531 } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS);
532
533 chunk = area_location(ps, ps->current_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000534
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500535 area = dm_bufio_read(client, chunk, &bp);
viresh kumarfc0a4462015-08-10 11:42:26 +0530536 if (IS_ERR(area)) {
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500537 r = PTR_ERR(area);
538 goto ret_destroy_bufio;
539 }
540
541 r = insert_exceptions(ps, area, callback, callback_context,
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500542 &full);
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500543
Mikulas Patocka2c945822014-03-03 17:19:22 -0500544 if (!full)
545 memcpy(ps->area, area, ps->store->chunk_size << SECTOR_SHIFT);
546
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500547 dm_bufio_release(bp);
548
549 dm_bufio_forget(client, chunk);
550
551 if (unlikely(r))
552 goto ret_destroy_bufio;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000553 }
554
555 ps->current_area--;
556
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100557 skip_metadata(ps);
558
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500559 r = 0;
560
561ret_destroy_bufio:
562 dm_bufio_client_destroy(client);
563
564 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000565}
566
567static struct pstore *get_info(struct dm_exception_store *store)
568{
569 return (struct pstore *) store->context;
570}
571
Mike Snitzer985903b2009-12-10 23:52:11 +0000572static void persistent_usage(struct dm_exception_store *store,
573 sector_t *total_sectors,
574 sector_t *sectors_allocated,
575 sector_t *metadata_sectors)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000576{
Mike Snitzer985903b2009-12-10 23:52:11 +0000577 struct pstore *ps = get_info(store);
578
579 *sectors_allocated = ps->next_free * store->chunk_size;
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000580 *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
Mike Snitzer985903b2009-12-10 23:52:11 +0000581
582 /*
583 * First chunk is the fixed header.
584 * Then there are (ps->current_area + 1) metadata chunks, each one
585 * separated from the next by ps->exceptions_per_area data chunks.
586 */
Mikulas Patocka4454a622009-12-10 23:52:29 +0000587 *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) *
588 store->chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000589}
590
Jonathan Brassow493df712009-04-02 19:55:31 +0100591static void persistent_dtr(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000592{
593 struct pstore *ps = get_info(store);
594
595 destroy_workqueue(ps->metadata_wq);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100596
597 /* Created in read_header */
598 if (ps->io_client)
599 dm_io_client_destroy(ps->io_client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000600 free_area(ps);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100601
602 /* Allocated in persistent_read_metadata */
Markus Elfring0c8f8632015-02-02 14:38:29 +0100603 vfree(ps->callbacks);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100604
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000605 kfree(ps);
606}
607
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000608static int persistent_read_metadata(struct dm_exception_store *store,
609 int (*callback)(void *callback_context,
610 chunk_t old, chunk_t new),
611 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000612{
613 int r, uninitialized_var(new_snapshot);
614 struct pstore *ps = get_info(store);
615
616 /*
617 * Read the snapshot header.
618 */
619 r = read_header(ps, &new_snapshot);
620 if (r)
621 return r;
622
623 /*
624 * Now we know correct chunk_size, complete the initialisation.
625 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100626 ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) /
627 sizeof(struct disk_exception);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000628 ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
Jonathan Brassowa2d2b032011-08-02 12:32:03 +0100629 sizeof(*ps->callbacks));
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000630 if (!ps->callbacks)
631 return -ENOMEM;
632
633 /*
634 * Do we need to setup a new snapshot ?
635 */
636 if (new_snapshot) {
637 r = write_header(ps);
638 if (r) {
639 DMWARN("write_header failed");
640 return r;
641 }
642
643 ps->current_area = 0;
644 zero_memory_area(ps);
645 r = zero_disk_area(ps, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000646 if (r)
Jon Brassowf5acc832009-12-10 23:52:07 +0000647 DMWARN("zero_disk_area(0) failed");
648 return r;
649 }
650 /*
651 * Sanity checks.
652 */
653 if (ps->version != SNAPSHOT_DISK_VERSION) {
654 DMWARN("unable to handle snapshot disk version %d",
655 ps->version);
656 return -EINVAL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000657 }
658
Jon Brassowf5acc832009-12-10 23:52:07 +0000659 /*
660 * Metadata are valid, but snapshot is invalidated
661 */
662 if (!ps->valid)
663 return 1;
664
665 /*
666 * Read the metadata.
667 */
668 r = read_exceptions(ps, callback, callback_context);
669
670 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000671}
672
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000673static int persistent_prepare_exception(struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +0000674 struct dm_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000675{
676 struct pstore *ps = get_info(store);
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000677 sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000678
679 /* Is there enough room ? */
Jonathan Brassowd0216842009-04-02 19:55:32 +0100680 if (size < ((ps->next_free + 1) * store->chunk_size))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000681 return -ENOSPC;
682
683 e->new_chunk = ps->next_free;
684
685 /*
686 * Move onto the next free pending, making sure to take
687 * into account the location of the metadata chunks.
688 */
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100689 ps->next_free++;
690 skip_metadata(ps);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000691
692 atomic_inc(&ps->pending_count);
693 return 0;
694}
695
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000696static void persistent_commit_exception(struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +0000697 struct dm_exception *e,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000698 void (*callback) (void *, int success),
699 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000700{
701 unsigned int i;
702 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100703 struct core_exception ce;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000704 struct commit_callback *cb;
705
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100706 ce.old_chunk = e->old_chunk;
707 ce.new_chunk = e->new_chunk;
708 write_exception(ps, ps->current_committed++, &ce);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000709
710 /*
711 * Add the callback to the back of the array. This code
712 * is the only place where the callback array is
713 * manipulated, and we know that it will never be called
714 * multiple times concurrently.
715 */
716 cb = ps->callbacks + ps->callback_count++;
717 cb->callback = callback;
718 cb->context = callback_context;
719
720 /*
721 * If there are exceptions in flight and we have not yet
722 * filled this metadata area there's nothing more to do.
723 */
724 if (!atomic_dec_and_test(&ps->pending_count) &&
725 (ps->current_committed != ps->exceptions_per_area))
726 return;
727
728 /*
729 * If we completely filled the current area, then wipe the next one.
730 */
731 if ((ps->current_committed == ps->exceptions_per_area) &&
Jonathan Brassowa2d2b032011-08-02 12:32:03 +0100732 zero_disk_area(ps, ps->current_area + 1))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000733 ps->valid = 0;
734
735 /*
736 * Commit exceptions to disk.
737 */
Tejun Heod87f4c12010-09-03 11:56:19 +0200738 if (ps->valid && area_io(ps, WRITE_FLUSH_FUA))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000739 ps->valid = 0;
740
741 /*
742 * Advance to the next area if this one is full.
743 */
744 if (ps->current_committed == ps->exceptions_per_area) {
745 ps->current_committed = 0;
746 ps->current_area++;
747 zero_memory_area(ps);
748 }
749
750 for (i = 0; i < ps->callback_count; i++) {
751 cb = ps->callbacks + i;
752 cb->callback(cb->context, ps->valid);
753 }
754
755 ps->callback_count = 0;
756}
757
Mikulas Patocka4454a622009-12-10 23:52:29 +0000758static int persistent_prepare_merge(struct dm_exception_store *store,
759 chunk_t *last_old_chunk,
760 chunk_t *last_new_chunk)
761{
762 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100763 struct core_exception ce;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000764 int nr_consecutive;
765 int r;
766
767 /*
768 * When current area is empty, move back to preceding area.
769 */
770 if (!ps->current_committed) {
771 /*
772 * Have we finished?
773 */
774 if (!ps->current_area)
775 return 0;
776
777 ps->current_area--;
778 r = area_io(ps, READ);
779 if (r < 0)
780 return r;
781 ps->current_committed = ps->exceptions_per_area;
782 }
783
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500784 read_exception(ps, ps->area, ps->current_committed - 1, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100785 *last_old_chunk = ce.old_chunk;
786 *last_new_chunk = ce.new_chunk;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000787
788 /*
789 * Find number of consecutive chunks within the current area,
790 * working backwards.
791 */
792 for (nr_consecutive = 1; nr_consecutive < ps->current_committed;
793 nr_consecutive++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500794 read_exception(ps, ps->area,
795 ps->current_committed - 1 - nr_consecutive, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100796 if (ce.old_chunk != *last_old_chunk - nr_consecutive ||
797 ce.new_chunk != *last_new_chunk - nr_consecutive)
Mikulas Patocka4454a622009-12-10 23:52:29 +0000798 break;
799 }
800
801 return nr_consecutive;
802}
803
804static int persistent_commit_merge(struct dm_exception_store *store,
805 int nr_merged)
806{
807 int r, i;
808 struct pstore *ps = get_info(store);
809
810 BUG_ON(nr_merged > ps->current_committed);
811
812 for (i = 0; i < nr_merged; i++)
813 clear_exception(ps, ps->current_committed - 1 - i);
814
Mikulas Patocka762a80d2011-08-02 12:32:00 +0100815 r = area_io(ps, WRITE_FLUSH_FUA);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000816 if (r < 0)
817 return r;
818
819 ps->current_committed -= nr_merged;
820
821 /*
822 * At this stage, only persistent_usage() uses ps->next_free, so
823 * we make no attempt to keep ps->next_free strictly accurate
824 * as exceptions may have been committed out-of-order originally.
825 * Once a snapshot has become merging, we set it to the value it
826 * would have held had all the exceptions been committed in order.
827 *
828 * ps->current_area does not get reduced by prepare_merge() until
829 * after commit_merge() has removed the nr_merged previous exceptions.
830 */
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100831 ps->next_free = area_location(ps, ps->current_area) +
832 ps->current_committed + 1;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000833
834 return 0;
835}
836
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000837static void persistent_drop_snapshot(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000838{
839 struct pstore *ps = get_info(store);
840
841 ps->valid = 0;
842 if (write_header(ps))
843 DMWARN("write header failed");
844}
845
Jonathan Brassow493df712009-04-02 19:55:31 +0100846static int persistent_ctr(struct dm_exception_store *store,
847 unsigned argc, char **argv)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000848{
849 struct pstore *ps;
850
851 /* allocate the pstore */
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100852 ps = kzalloc(sizeof(*ps), GFP_KERNEL);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000853 if (!ps)
854 return -ENOMEM;
855
Jonathan Brassow71fab002009-04-02 19:55:33 +0100856 ps->store = store;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000857 ps->valid = 1;
858 ps->version = SNAPSHOT_DISK_VERSION;
859 ps->area = NULL;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100860 ps->zero_area = NULL;
861 ps->header_area = NULL;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000862 ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000863 ps->current_committed = 0;
864
865 ps->callback_count = 0;
866 atomic_set(&ps->pending_count, 0);
867 ps->callbacks = NULL;
868
Tejun Heo239c8dd2011-01-13 19:59:59 +0000869 ps->metadata_wq = alloc_workqueue("ksnaphd", WQ_MEM_RECLAIM, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000870 if (!ps->metadata_wq) {
871 kfree(ps);
872 DMERR("couldn't start header metadata update thread");
873 return -ENOMEM;
874 }
875
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000876 store->context = ps;
877
878 return 0;
879}
880
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100881static unsigned persistent_status(struct dm_exception_store *store,
882 status_type_t status, char *result,
883 unsigned maxlen)
Jonathan Brassow493df712009-04-02 19:55:31 +0100884{
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100885 unsigned sz = 0;
886
887 switch (status) {
888 case STATUSTYPE_INFO:
889 break;
890 case STATUSTYPE_TABLE:
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000891 DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100892 }
Jonathan Brassow493df712009-04-02 19:55:31 +0100893
894 return sz;
895}
896
897static struct dm_exception_store_type _persistent_type = {
898 .name = "persistent",
899 .module = THIS_MODULE,
900 .ctr = persistent_ctr,
901 .dtr = persistent_dtr,
902 .read_metadata = persistent_read_metadata,
903 .prepare_exception = persistent_prepare_exception,
904 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000905 .prepare_merge = persistent_prepare_merge,
906 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100907 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000908 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100909 .status = persistent_status,
910};
911
912static struct dm_exception_store_type _persistent_compat_type = {
913 .name = "P",
914 .module = THIS_MODULE,
915 .ctr = persistent_ctr,
916 .dtr = persistent_dtr,
917 .read_metadata = persistent_read_metadata,
918 .prepare_exception = persistent_prepare_exception,
919 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000920 .prepare_merge = persistent_prepare_merge,
921 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100922 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000923 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100924 .status = persistent_status,
925};
926
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000927int dm_persistent_snapshot_init(void)
928{
Jonathan Brassow493df712009-04-02 19:55:31 +0100929 int r;
930
931 r = dm_exception_store_type_register(&_persistent_type);
932 if (r) {
933 DMERR("Unable to register persistent exception store type");
934 return r;
935 }
936
937 r = dm_exception_store_type_register(&_persistent_compat_type);
938 if (r) {
939 DMERR("Unable to register old-style persistent exception "
940 "store type");
941 dm_exception_store_type_unregister(&_persistent_type);
942 return r;
943 }
944
945 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000946}
947
948void dm_persistent_snapshot_exit(void)
949{
Jonathan Brassow493df712009-04-02 19:55:31 +0100950 dm_exception_store_type_unregister(&_persistent_type);
951 dm_exception_store_type_unregister(&_persistent_compat_type);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000952}