aboutsummaryrefslogtreecommitdiff
path: root/drivers/md/dm-exception-store.c
blob: fe0cfa6771396ae2d6a67388b1a34a5981d77cb9 (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
/*
 * 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/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);

int dm_exception_store_create(const char *type_name, struct dm_target *ti,
			      struct dm_exception_store **store)
{
	int r = 0;
	struct dm_exception_store_type *type;
	struct dm_exception_store *tmp_store;

	tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
	if (!tmp_store)
		return -ENOMEM;

	type = get_type(type_name);
	if (!type) {
		kfree(tmp_store);
		return -EINVAL;
	}

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

	r = type->ctr(tmp_store, 0, NULL);
	if (r) {
		put_type(type);
		kfree(tmp_store);
		return r;
	}

	*store = tmp_store;
	return 0;
}
EXPORT_SYMBOL(dm_exception_store_create);

void dm_exception_store_destroy(struct dm_exception_store *store)
{
	store->type->dtr(store);
	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();
}