summaryrefslogtreecommitdiffstats
path: root/drivers/md/dm-exception-store.c
blob: 556acff3952fe450e73e4673f46bcac84b453a47 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
/*
 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
 * Copyright (C) 2006-2008 Red Hat GmbH
 *
 * This file is released under the GPL.
 */

#include "dm-exception-store.h"

#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>

#define DM_MSG_PREFIX "snapshot exception stores"

static LIST_HEAD(_exception_store_types);
static DEFINE_SPINLOCK(_lock);

static struct dm_exception_store_type *__find_exception_store_type(const char *name)
{
	struct dm_exception_store_type *type;

	list_for_each_entry(type, &_exception_store_types, list)
		if (!strcmp(name, type->name))
			return type;

	return NULL;
}

static struct dm_exception_store_type *_get_exception_store_type(const char *name)
{
	struct dm_exception_store_type *type;

	spin_lock(&_lock);

	type = __find_exception_store_type(name);

	if (type && !try_module_get(type->module))
		type = NULL;

	spin_unlock(&_lock);

	return type;
}

/*
 * get_type
 * @type_name
 *
 * Attempt to retrieve the dm_exception_store_type by name.  If not already
 * available, attempt to load the appropriate module.
 *
 * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
 * Modules may contain multiple types.
 * This function will first try the module "dm-exstore-<type_name>",
 * then truncate 'type_name' on the last '-' and try again.
 *
 * For example, if type_name was "clustered-shared", it would search
 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
 *
 * 'dm-exception-store-<type_name>' is too long of a name in my
 * opinion, which is why I've chosen to have the files
 * containing exception store implementations be 'dm-exstore-<type_name>'.
 * If you want your module to be autoloaded, you will follow this
 * naming convention.
 *
 * Returns: dm_exception_store_type* on success, NULL on failure
 */
static struct dm_exception_store_type *get_type(const char *type_name)
{
	char *p, *type_name_dup;
	struct dm_exception_store_type *type;

	type = _get_exception_store_type(type_name);
	if (type)
		return type;

	type_name_dup = kstrdup(type_name, GFP_KERNEL);
	if (!type_name_dup) {
		DMERR("No memory left to attempt load for \"%s\"", type_name);
		return NULL;
	}

	while (request_module("dm-exstore-%s", type_name_dup) ||
	       !(type = _get_exception_store_type(type_name))) {
		p = strrchr(type_name_dup, '-');
		if (!p)
			break;
		p[0] = '\0';
	}

	if (!type)
		DMWARN("Module for exstore type \"%s\" not found.", type_name);

	kfree(type_name_dup);

	return type;
}

static void put_type(struct dm_exception_store_type *type)
{
	spin_lock(&_lock);
	module_put(type->module);
	spin_unlock(&_lock);
}

int dm_exception_store_type_register(struct dm_exception_store_type *type)
{
	int r = 0;

	spin_lock(&_lock);
	if (!__find_exception_store_type(type->name))
		list_add(&type->list, &_exception_store_types);
	else
		r = -EEXIST;
	spin_unlock(&_lock);

	return r;
}
EXPORT_SYMBOL(dm_exception_store_type_register);

int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
{
	spin_lock(&_lock);

	if (!__find_exception_store_type(type->name)) {
		spin_unlock(&_lock);
		return -EINVAL;
	}

	list_del(&type->list);

	spin_unlock(&_lock);

	return 0;
}
EXPORT_SYMBOL(dm_exception_store_type_unregister);

/*
 * Round a number up to the nearest 'size' boundary.  size must
 * be a power of 2.
 */
static ulong round_up(ulong n, ulong size)
{
	size--;
	return (n + size) & ~size;
}

static int set_chunk_size(struct dm_exception_store *store,
			  const char *chunk_size_arg, char **error)
{
	unsigned long chunk_size_ulong;
	char *value;

	chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
	if (*chunk_size_arg == '\0' || *value != '\0') {
		*error = "Invalid chunk size";
		return -EINVAL;
	}

	if (!chunk_size_ulong) {
		store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
		return 0;
	}

	/*
	 * Chunk size must be multiple of page size.  Silently
	 * round up if it's not.
	 */
	chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9);

	return dm_exception_store_set_chunk_size(store, chunk_size_ulong,
						 error);
}

int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
				      unsigned long chunk_size_ulong,
				      char **error)
{
	/* Check chunk_size is a power of 2 */
	if (!is_power_of_2(chunk_size_ulong)) {
		*error = "Chunk size is not a power of 2";
		return -EINVAL;
	}

	/* Validate the chunk size against the device block size */
	if (chunk_size_ulong % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
		*error = "Chunk size is not a multiple of device blocksize";
		return -EINVAL;
	}

	if (chunk_size_ulong > INT_MAX >> SECTOR_SHIFT) {
		*error = "Chunk size is too high";
		return -EINVAL;
	}

	store->chunk_size = chunk_size_ulong;
	store->chunk_mask = chunk_size_ulong - 1;
	store->chunk_shift = ffs(chunk_size_ulong) - 1;

	return 0;
}

int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
			      unsigned *args_used,
			      struct dm_exception_store **store)
{
	int r = 0;
	struct dm_exception_store_type *type = NULL;
	struct dm_exception_store *tmp_store;
	char persistent;

	if (argc < 3) {
		ti->error = "Insufficient exception store arguments";
		return -EINVAL;
	}

	tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
	if (!tmp_store) {
		ti->error = "Exception store allocation failed";
		return -ENOMEM;
	}

	persistent = toupper(*argv[1]);
	if (persistent == 'P')
		type = get_type("P");
	else if (persistent == 'N')
		type = get_type("N");
	else {
		ti->error = "Persistent flag is not P or N";
		return -EINVAL;
	}

	if (!type) {
		ti->error = "Exception store type not recognised";
		r = -EINVAL;
		goto bad_type;
	}

	tmp_store->type = type;
	tmp_store->ti = ti;

	r = dm_get_device(ti, argv[0], 0, 0,
			  FMODE_READ | FMODE_WRITE, &tmp_store->cow);
	if (r) {
		ti->error = "Cannot get COW device";
		goto bad_cow;
	}

	r = set_chunk_size(tmp_store, argv[2], &ti->error);
	if (r)
		goto bad_cow;

	r = type->ctr(tmp_store, 0, NULL);
	if (r) {
		ti->error = "Exception store type constructor failed";
		goto bad_ctr;
	}

	*args_used = 3;
	*store = tmp_store;
	return 0;

bad_ctr:
	dm_put_device(ti, tmp_store->cow);
bad_cow:
	put_type(type);
bad_type:
	kfree(tmp_store);
	return r;
}
EXPORT_SYMBOL(dm_exception_store_create);

void dm_exception_store_destroy(struct dm_exception_store *store)
{
	store->type->dtr(store);
	dm_put_device(store->ti, store->cow);
	put_type(store->type);
	kfree(store);
}
EXPORT_SYMBOL(dm_exception_store_destroy);

int dm_exception_store_init(void)
{
	int r;

	r = dm_transient_snapshot_init();
	if (r) {
		DMERR("Unable to register transient exception store type.");
		goto transient_fail;
	}

	r = dm_persistent_snapshot_init();
	if (r) {
		DMERR("Unable to register persistent exception store type");
		goto persistent_fail;
	}

	return 0;

persistent_fail:
	dm_persistent_snapshot_exit();
transient_fail:
	return r;
}

void dm_exception_store_exit(void)
{
	dm_persistent_snapshot_exit();
	dm_transient_snapshot_exit();
}