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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{
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100203 if (ps->area)
204 vfree(ps->area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000205 ps->area = NULL;
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100206
207 if (ps->zero_area)
208 vfree(ps->zero_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000209 ps->zero_area = NULL;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100210
211 if (ps->header_area)
212 vfree(ps->header_area);
213 ps->header_area = NULL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000214}
215
216struct mdata_req {
217 struct dm_io_region *where;
218 struct dm_io_request *io_req;
219 struct work_struct work;
220 int result;
221};
222
223static void do_metadata(struct work_struct *work)
224{
225 struct mdata_req *req = container_of(work, struct mdata_req, work);
226
227 req->result = dm_io(req->io_req, 1, req->where, NULL);
228}
229
230/*
231 * Read or write a chunk aligned and sized block of data from a device.
232 */
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100233static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw,
234 int metadata)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000235{
236 struct dm_io_region where = {
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000237 .bdev = dm_snap_cow(ps->store->snap)->bdev,
Jonathan Brassow71fab002009-04-02 19:55:33 +0100238 .sector = ps->store->chunk_size * chunk,
239 .count = ps->store->chunk_size,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000240 };
241 struct dm_io_request io_req = {
242 .bi_rw = rw,
243 .mem.type = DM_IO_VMA,
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100244 .mem.ptr.vma = area,
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000245 .client = ps->io_client,
246 .notify.fn = NULL,
247 };
248 struct mdata_req req;
249
250 if (!metadata)
251 return dm_io(&io_req, 1, &where, NULL);
252
253 req.where = &where;
254 req.io_req = &io_req;
255
256 /*
257 * Issue the synchronous I/O from a different thread
258 * to avoid generic_make_request recursion.
259 */
Andrew Mortonca1cab32010-10-26 14:22:34 -0700260 INIT_WORK_ONSTACK(&req.work, do_metadata);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000261 queue_work(ps->metadata_wq, &req.work);
Mikulas Patocka5ea330a2013-09-18 19:14:22 -0400262 flush_workqueue(ps->metadata_wq);
Chuansheng Liuc1a64162014-01-07 16:56:18 +0800263 destroy_work_on_stack(&req.work);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000264
265 return req.result;
266}
267
268/*
269 * Convert a metadata area index to a chunk index.
270 */
271static chunk_t area_location(struct pstore *ps, chunk_t area)
272{
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100273 return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000274}
275
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100276static void skip_metadata(struct pstore *ps)
277{
278 uint32_t stride = ps->exceptions_per_area + 1;
279 chunk_t next_free = ps->next_free;
280 if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS)
281 ps->next_free++;
282}
283
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000284/*
285 * Read or write a metadata area. Remembering to skip the first
286 * chunk which holds the header.
287 */
288static int area_io(struct pstore *ps, int rw)
289{
290 int r;
291 chunk_t chunk;
292
293 chunk = area_location(ps, ps->current_area);
294
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100295 r = chunk_io(ps, ps->area, chunk, rw, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000296 if (r)
297 return r;
298
299 return 0;
300}
301
302static void zero_memory_area(struct pstore *ps)
303{
Jonathan Brassow71fab002009-04-02 19:55:33 +0100304 memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000305}
306
307static int zero_disk_area(struct pstore *ps, chunk_t area)
308{
Mikulas Patocka02d2fd32009-09-04 20:40:37 +0100309 return chunk_io(ps, ps->zero_area, area_location(ps, area), WRITE, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000310}
311
312static int read_header(struct pstore *ps, int *new_snapshot)
313{
314 int r;
315 struct disk_header *dh;
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100316 unsigned chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000317 int chunk_size_supplied = 1;
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100318 char *chunk_err;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000319
320 /*
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100321 * Use default chunk size (or logical_block_size, if larger)
322 * if none supplied
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000323 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100324 if (!ps->store->chunk_size) {
325 ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000326 bdev_logical_block_size(dm_snap_cow(ps->store->snap)->
327 bdev) >> 9);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100328 ps->store->chunk_mask = ps->store->chunk_size - 1;
329 ps->store->chunk_shift = ffs(ps->store->chunk_size) - 1;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000330 chunk_size_supplied = 0;
331 }
332
Mikulas Patockabda8efe2011-05-29 13:03:09 +0100333 ps->io_client = dm_io_client_create();
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000334 if (IS_ERR(ps->io_client))
335 return PTR_ERR(ps->io_client);
336
337 r = alloc_area(ps);
338 if (r)
339 return r;
340
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100341 r = chunk_io(ps, ps->header_area, 0, READ, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000342 if (r)
343 goto bad;
344
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100345 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000346
347 if (le32_to_cpu(dh->magic) == 0) {
348 *new_snapshot = 1;
349 return 0;
350 }
351
352 if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
353 DMWARN("Invalid or corrupt snapshot");
354 r = -ENXIO;
355 goto bad;
356 }
357
358 *new_snapshot = 0;
359 ps->valid = le32_to_cpu(dh->valid);
360 ps->version = le32_to_cpu(dh->version);
361 chunk_size = le32_to_cpu(dh->chunk_size);
362
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100363 if (ps->store->chunk_size == chunk_size)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000364 return 0;
365
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100366 if (chunk_size_supplied)
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100367 DMWARN("chunk size %u in device metadata overrides "
368 "table chunk size of %u.",
369 chunk_size, ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000370
371 /* We had a bogus chunk_size. Fix stuff up. */
372 free_area(ps);
373
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100374 r = dm_exception_store_set_chunk_size(ps->store, chunk_size,
375 &chunk_err);
376 if (r) {
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100377 DMERR("invalid on-disk chunk size %u: %s.",
378 chunk_size, chunk_err);
Mikulas Patockaae0b7442009-09-04 20:40:43 +0100379 return r;
380 }
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000381
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000382 r = alloc_area(ps);
383 return r;
384
385bad:
386 free_area(ps);
387 return r;
388}
389
390static int write_header(struct pstore *ps)
391{
392 struct disk_header *dh;
393
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100394 memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000395
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100396 dh = ps->header_area;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000397 dh->magic = cpu_to_le32(SNAP_MAGIC);
398 dh->valid = cpu_to_le32(ps->valid);
399 dh->version = cpu_to_le32(ps->version);
Jonathan Brassow71fab002009-04-02 19:55:33 +0100400 dh->chunk_size = cpu_to_le32(ps->store->chunk_size);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000401
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100402 return chunk_io(ps, ps->header_area, 0, WRITE, 1);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000403}
404
405/*
406 * Access functions for the disk exceptions, these do the endian conversions.
407 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500408static struct disk_exception *get_exception(struct pstore *ps, void *ps_area,
409 uint32_t index)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000410{
411 BUG_ON(index >= ps->exceptions_per_area);
412
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500413 return ((struct disk_exception *) ps_area) + index;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000414}
415
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500416static void read_exception(struct pstore *ps, void *ps_area,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100417 uint32_t index, struct core_exception *result)
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 result->old_chunk = le64_to_cpu(de->old_chunk);
423 result->new_chunk = le64_to_cpu(de->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000424}
425
426static void write_exception(struct pstore *ps,
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100427 uint32_t index, struct core_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000428{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500429 struct disk_exception *de = get_exception(ps, ps->area, index);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000430
431 /* copy it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100432 de->old_chunk = cpu_to_le64(e->old_chunk);
433 de->new_chunk = cpu_to_le64(e->new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000434}
435
Mikulas Patocka4454a622009-12-10 23:52:29 +0000436static void clear_exception(struct pstore *ps, uint32_t index)
437{
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500438 struct disk_exception *de = get_exception(ps, ps->area, index);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000439
440 /* clear it */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100441 de->old_chunk = 0;
442 de->new_chunk = 0;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000443}
444
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000445/*
446 * Registers the exceptions that are present in the current area.
447 * 'full' is filled in to indicate if the area has been
448 * filled.
449 */
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500450static int insert_exceptions(struct pstore *ps, void *ps_area,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000451 int (*callback)(void *callback_context,
452 chunk_t old, chunk_t new),
453 void *callback_context,
454 int *full)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000455{
456 int r;
457 unsigned int i;
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100458 struct core_exception e;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000459
460 /* presume the area is full */
461 *full = 1;
462
463 for (i = 0; i < ps->exceptions_per_area; i++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500464 read_exception(ps, ps_area, i, &e);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000465
466 /*
467 * If the new_chunk is pointing at the start of
468 * the COW device, where the first metadata area
469 * is we know that we've hit the end of the
470 * exceptions. Therefore the area is not full.
471 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100472 if (e.new_chunk == 0LL) {
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000473 ps->current_committed = i;
474 *full = 0;
475 break;
476 }
477
478 /*
479 * Keep track of the start of the free chunks.
480 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100481 if (ps->next_free <= e.new_chunk)
482 ps->next_free = e.new_chunk + 1;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000483
484 /*
485 * Otherwise we add the exception to the snapshot.
486 */
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100487 r = callback(callback_context, e.old_chunk, e.new_chunk);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000488 if (r)
489 return r;
490 }
491
492 return 0;
493}
494
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000495static int read_exceptions(struct pstore *ps,
496 int (*callback)(void *callback_context, chunk_t old,
497 chunk_t new),
498 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000499{
500 int r, full = 1;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500501 struct dm_bufio_client *client;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500502 chunk_t prefetch_area = 0;
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500503
504 client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev,
505 ps->store->chunk_size << SECTOR_SHIFT,
506 1, 0, NULL, NULL);
507
508 if (IS_ERR(client))
509 return PTR_ERR(client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000510
511 /*
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500512 * Setup for one current buffer + desired readahead buffers.
513 */
514 dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS);
515
516 /*
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000517 * Keeping reading chunks and inserting exceptions until
518 * we find a partially full area.
519 */
520 for (ps->current_area = 0; full; ps->current_area++) {
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500521 struct dm_buffer *bp;
522 void *area;
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500523 chunk_t chunk;
524
525 if (unlikely(prefetch_area < ps->current_area))
526 prefetch_area = ps->current_area;
527
528 if (DM_PREFETCH_CHUNKS) do {
529 chunk_t pf_chunk = area_location(ps, prefetch_area);
530 if (unlikely(pf_chunk >= dm_bufio_get_device_size(client)))
531 break;
532 dm_bufio_prefetch(client, pf_chunk, 1);
533 prefetch_area++;
534 if (unlikely(!prefetch_area))
535 break;
536 } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS);
537
538 chunk = area_location(ps, ps->current_area);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000539
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500540 area = dm_bufio_read(client, chunk, &bp);
541 if (unlikely(IS_ERR(area))) {
542 r = PTR_ERR(area);
543 goto ret_destroy_bufio;
544 }
545
546 r = insert_exceptions(ps, area, callback, callback_context,
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500547 &full);
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500548
549 dm_bufio_release(bp);
550
551 dm_bufio_forget(client, chunk);
552
553 if (unlikely(r))
554 goto ret_destroy_bufio;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000555 }
556
557 ps->current_area--;
558
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100559 skip_metadata(ps);
560
Mikulas Patocka55494bf2014-01-13 19:12:36 -0500561 r = 0;
562
563ret_destroy_bufio:
564 dm_bufio_client_destroy(client);
565
566 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000567}
568
569static struct pstore *get_info(struct dm_exception_store *store)
570{
571 return (struct pstore *) store->context;
572}
573
Mike Snitzer985903b2009-12-10 23:52:11 +0000574static void persistent_usage(struct dm_exception_store *store,
575 sector_t *total_sectors,
576 sector_t *sectors_allocated,
577 sector_t *metadata_sectors)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000578{
Mike Snitzer985903b2009-12-10 23:52:11 +0000579 struct pstore *ps = get_info(store);
580
581 *sectors_allocated = ps->next_free * store->chunk_size;
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000582 *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
Mike Snitzer985903b2009-12-10 23:52:11 +0000583
584 /*
585 * First chunk is the fixed header.
586 * Then there are (ps->current_area + 1) metadata chunks, each one
587 * separated from the next by ps->exceptions_per_area data chunks.
588 */
Mikulas Patocka4454a622009-12-10 23:52:29 +0000589 *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) *
590 store->chunk_size;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000591}
592
Jonathan Brassow493df712009-04-02 19:55:31 +0100593static void persistent_dtr(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000594{
595 struct pstore *ps = get_info(store);
596
597 destroy_workqueue(ps->metadata_wq);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100598
599 /* Created in read_header */
600 if (ps->io_client)
601 dm_io_client_destroy(ps->io_client);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000602 free_area(ps);
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100603
604 /* Allocated in persistent_read_metadata */
605 if (ps->callbacks)
606 vfree(ps->callbacks);
607
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000608 kfree(ps);
609}
610
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000611static int persistent_read_metadata(struct dm_exception_store *store,
612 int (*callback)(void *callback_context,
613 chunk_t old, chunk_t new),
614 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000615{
616 int r, uninitialized_var(new_snapshot);
617 struct pstore *ps = get_info(store);
618
619 /*
620 * Read the snapshot header.
621 */
622 r = read_header(ps, &new_snapshot);
623 if (r)
624 return r;
625
626 /*
627 * Now we know correct chunk_size, complete the initialisation.
628 */
Jonathan Brassow71fab002009-04-02 19:55:33 +0100629 ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) /
630 sizeof(struct disk_exception);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000631 ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
Jonathan Brassowa2d2b032011-08-02 12:32:03 +0100632 sizeof(*ps->callbacks));
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000633 if (!ps->callbacks)
634 return -ENOMEM;
635
636 /*
637 * Do we need to setup a new snapshot ?
638 */
639 if (new_snapshot) {
640 r = write_header(ps);
641 if (r) {
642 DMWARN("write_header failed");
643 return r;
644 }
645
646 ps->current_area = 0;
647 zero_memory_area(ps);
648 r = zero_disk_area(ps, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000649 if (r)
Jon Brassowf5acc832009-12-10 23:52:07 +0000650 DMWARN("zero_disk_area(0) failed");
651 return r;
652 }
653 /*
654 * Sanity checks.
655 */
656 if (ps->version != SNAPSHOT_DISK_VERSION) {
657 DMWARN("unable to handle snapshot disk version %d",
658 ps->version);
659 return -EINVAL;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000660 }
661
Jon Brassowf5acc832009-12-10 23:52:07 +0000662 /*
663 * Metadata are valid, but snapshot is invalidated
664 */
665 if (!ps->valid)
666 return 1;
667
668 /*
669 * Read the metadata.
670 */
671 r = read_exceptions(ps, callback, callback_context);
672
673 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000674}
675
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000676static int persistent_prepare_exception(struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +0000677 struct dm_exception *e)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000678{
679 struct pstore *ps = get_info(store);
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000680 sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000681
682 /* Is there enough room ? */
Jonathan Brassowd0216842009-04-02 19:55:32 +0100683 if (size < ((ps->next_free + 1) * store->chunk_size))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000684 return -ENOSPC;
685
686 e->new_chunk = ps->next_free;
687
688 /*
689 * Move onto the next free pending, making sure to take
690 * into account the location of the metadata chunks.
691 */
Mikulas Patockae9c6a182013-10-16 03:17:47 +0100692 ps->next_free++;
693 skip_metadata(ps);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000694
695 atomic_inc(&ps->pending_count);
696 return 0;
697}
698
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000699static void persistent_commit_exception(struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +0000700 struct dm_exception *e,
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000701 void (*callback) (void *, int success),
702 void *callback_context)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000703{
704 unsigned int i;
705 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100706 struct core_exception ce;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000707 struct commit_callback *cb;
708
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100709 ce.old_chunk = e->old_chunk;
710 ce.new_chunk = e->new_chunk;
711 write_exception(ps, ps->current_committed++, &ce);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000712
713 /*
714 * Add the callback to the back of the array. This code
715 * is the only place where the callback array is
716 * manipulated, and we know that it will never be called
717 * multiple times concurrently.
718 */
719 cb = ps->callbacks + ps->callback_count++;
720 cb->callback = callback;
721 cb->context = callback_context;
722
723 /*
724 * If there are exceptions in flight and we have not yet
725 * filled this metadata area there's nothing more to do.
726 */
727 if (!atomic_dec_and_test(&ps->pending_count) &&
728 (ps->current_committed != ps->exceptions_per_area))
729 return;
730
731 /*
732 * If we completely filled the current area, then wipe the next one.
733 */
734 if ((ps->current_committed == ps->exceptions_per_area) &&
Jonathan Brassowa2d2b032011-08-02 12:32:03 +0100735 zero_disk_area(ps, ps->current_area + 1))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000736 ps->valid = 0;
737
738 /*
739 * Commit exceptions to disk.
740 */
Tejun Heod87f4c12010-09-03 11:56:19 +0200741 if (ps->valid && area_io(ps, WRITE_FLUSH_FUA))
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000742 ps->valid = 0;
743
744 /*
745 * Advance to the next area if this one is full.
746 */
747 if (ps->current_committed == ps->exceptions_per_area) {
748 ps->current_committed = 0;
749 ps->current_area++;
750 zero_memory_area(ps);
751 }
752
753 for (i = 0; i < ps->callback_count; i++) {
754 cb = ps->callbacks + i;
755 cb->callback(cb->context, ps->valid);
756 }
757
758 ps->callback_count = 0;
759}
760
Mikulas Patocka4454a622009-12-10 23:52:29 +0000761static int persistent_prepare_merge(struct dm_exception_store *store,
762 chunk_t *last_old_chunk,
763 chunk_t *last_new_chunk)
764{
765 struct pstore *ps = get_info(store);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100766 struct core_exception ce;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000767 int nr_consecutive;
768 int r;
769
770 /*
771 * When current area is empty, move back to preceding area.
772 */
773 if (!ps->current_committed) {
774 /*
775 * Have we finished?
776 */
777 if (!ps->current_area)
778 return 0;
779
780 ps->current_area--;
781 r = area_io(ps, READ);
782 if (r < 0)
783 return r;
784 ps->current_committed = ps->exceptions_per_area;
785 }
786
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500787 read_exception(ps, ps->area, ps->current_committed - 1, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100788 *last_old_chunk = ce.old_chunk;
789 *last_new_chunk = ce.new_chunk;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000790
791 /*
792 * Find number of consecutive chunks within the current area,
793 * working backwards.
794 */
795 for (nr_consecutive = 1; nr_consecutive < ps->current_committed;
796 nr_consecutive++) {
Mikulas Patocka2cadabd2014-01-13 19:14:04 -0500797 read_exception(ps, ps->area,
798 ps->current_committed - 1 - nr_consecutive, &ce);
Alasdair G Kergon283a8322011-08-02 12:32:01 +0100799 if (ce.old_chunk != *last_old_chunk - nr_consecutive ||
800 ce.new_chunk != *last_new_chunk - nr_consecutive)
Mikulas Patocka4454a622009-12-10 23:52:29 +0000801 break;
802 }
803
804 return nr_consecutive;
805}
806
807static int persistent_commit_merge(struct dm_exception_store *store,
808 int nr_merged)
809{
810 int r, i;
811 struct pstore *ps = get_info(store);
812
813 BUG_ON(nr_merged > ps->current_committed);
814
815 for (i = 0; i < nr_merged; i++)
816 clear_exception(ps, ps->current_committed - 1 - i);
817
Mikulas Patocka762a80d2011-08-02 12:32:00 +0100818 r = area_io(ps, WRITE_FLUSH_FUA);
Mikulas Patocka4454a622009-12-10 23:52:29 +0000819 if (r < 0)
820 return r;
821
822 ps->current_committed -= nr_merged;
823
824 /*
825 * At this stage, only persistent_usage() uses ps->next_free, so
826 * we make no attempt to keep ps->next_free strictly accurate
827 * as exceptions may have been committed out-of-order originally.
828 * Once a snapshot has become merging, we set it to the value it
829 * would have held had all the exceptions been committed in order.
830 *
831 * ps->current_area does not get reduced by prepare_merge() until
832 * after commit_merge() has removed the nr_merged previous exceptions.
833 */
Tomohiro Kusumi87c961c2010-08-12 04:13:59 +0100834 ps->next_free = area_location(ps, ps->current_area) +
835 ps->current_committed + 1;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000836
837 return 0;
838}
839
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000840static void persistent_drop_snapshot(struct dm_exception_store *store)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000841{
842 struct pstore *ps = get_info(store);
843
844 ps->valid = 0;
845 if (write_header(ps))
846 DMWARN("write header failed");
847}
848
Jonathan Brassow493df712009-04-02 19:55:31 +0100849static int persistent_ctr(struct dm_exception_store *store,
850 unsigned argc, char **argv)
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000851{
852 struct pstore *ps;
853
854 /* allocate the pstore */
Jonathan Brassowa32079c2009-04-02 19:55:35 +0100855 ps = kzalloc(sizeof(*ps), GFP_KERNEL);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000856 if (!ps)
857 return -ENOMEM;
858
Jonathan Brassow71fab002009-04-02 19:55:33 +0100859 ps->store = store;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000860 ps->valid = 1;
861 ps->version = SNAPSHOT_DISK_VERSION;
862 ps->area = NULL;
Mikulas Patocka61578dc2009-09-04 20:40:39 +0100863 ps->zero_area = NULL;
864 ps->header_area = NULL;
Mikulas Patocka4454a622009-12-10 23:52:29 +0000865 ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000866 ps->current_committed = 0;
867
868 ps->callback_count = 0;
869 atomic_set(&ps->pending_count, 0);
870 ps->callbacks = NULL;
871
Tejun Heo239c8dd2011-01-13 19:59:59 +0000872 ps->metadata_wq = alloc_workqueue("ksnaphd", WQ_MEM_RECLAIM, 0);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000873 if (!ps->metadata_wq) {
874 kfree(ps);
875 DMERR("couldn't start header metadata update thread");
876 return -ENOMEM;
877 }
878
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000879 store->context = ps;
880
881 return 0;
882}
883
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100884static unsigned persistent_status(struct dm_exception_store *store,
885 status_type_t status, char *result,
886 unsigned maxlen)
Jonathan Brassow493df712009-04-02 19:55:31 +0100887{
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100888 unsigned sz = 0;
889
890 switch (status) {
891 case STATUSTYPE_INFO:
892 break;
893 case STATUSTYPE_TABLE:
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000894 DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
Jonathan Brassow1e302a92009-04-02 19:55:35 +0100895 }
Jonathan Brassow493df712009-04-02 19:55:31 +0100896
897 return sz;
898}
899
900static struct dm_exception_store_type _persistent_type = {
901 .name = "persistent",
902 .module = THIS_MODULE,
903 .ctr = persistent_ctr,
904 .dtr = persistent_dtr,
905 .read_metadata = persistent_read_metadata,
906 .prepare_exception = persistent_prepare_exception,
907 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000908 .prepare_merge = persistent_prepare_merge,
909 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100910 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000911 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100912 .status = persistent_status,
913};
914
915static struct dm_exception_store_type _persistent_compat_type = {
916 .name = "P",
917 .module = THIS_MODULE,
918 .ctr = persistent_ctr,
919 .dtr = persistent_dtr,
920 .read_metadata = persistent_read_metadata,
921 .prepare_exception = persistent_prepare_exception,
922 .commit_exception = persistent_commit_exception,
Mikulas Patocka4454a622009-12-10 23:52:29 +0000923 .prepare_merge = persistent_prepare_merge,
924 .commit_merge = persistent_commit_merge,
Jonathan Brassow493df712009-04-02 19:55:31 +0100925 .drop_snapshot = persistent_drop_snapshot,
Mike Snitzer985903b2009-12-10 23:52:11 +0000926 .usage = persistent_usage,
Jonathan Brassow493df712009-04-02 19:55:31 +0100927 .status = persistent_status,
928};
929
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000930int dm_persistent_snapshot_init(void)
931{
Jonathan Brassow493df712009-04-02 19:55:31 +0100932 int r;
933
934 r = dm_exception_store_type_register(&_persistent_type);
935 if (r) {
936 DMERR("Unable to register persistent exception store type");
937 return r;
938 }
939
940 r = dm_exception_store_type_register(&_persistent_compat_type);
941 if (r) {
942 DMERR("Unable to register old-style persistent exception "
943 "store type");
944 dm_exception_store_type_unregister(&_persistent_type);
945 return r;
946 }
947
948 return r;
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000949}
950
951void dm_persistent_snapshot_exit(void)
952{
Jonathan Brassow493df712009-04-02 19:55:31 +0100953 dm_exception_store_type_unregister(&_persistent_type);
954 dm_exception_store_type_unregister(&_persistent_compat_type);
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000955}