1/*
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"
9
10#include <linux/ctype.h>
11#include <linux/mm.h>
12#include <linux/pagemap.h>
13#include <linux/vmalloc.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16
17#define DM_MSG_PREFIX "snapshot exception stores"
18
19static LIST_HEAD(_exception_store_types);
20static DEFINE_SPINLOCK(_lock);
21
22static struct dm_exception_store_type *__find_exception_store_type(const char *name)
23{
24 struct dm_exception_store_type *type;
25
26 list_for_each_entry(type, &_exception_store_types, list)
27 if (!strcmp(name, type->name))
28 return type;
29
30 return NULL;
31}
32
33static struct dm_exception_store_type *_get_exception_store_type(const char *name)
34{
35 struct dm_exception_store_type *type;
36
37 spin_lock(&_lock);
38
39 type = __find_exception_store_type(name);
40
41 if (type && !try_module_get(type->module))
42 type = NULL;
43
44 spin_unlock(&_lock);
45
46 return type;
47}
48
49/*
50 * get_type
51 * @type_name
52 *
53 * Attempt to retrieve the dm_exception_store_type by name. If not already
54 * available, attempt to load the appropriate module.
55 *
56 * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
57 * Modules may contain multiple types.
58 * This function will first try the module "dm-exstore-<type_name>",
59 * then truncate 'type_name' on the last '-' and try again.
60 *
61 * For example, if type_name was "clustered-shared", it would search
62 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
63 *
64 * 'dm-exception-store-<type_name>' is too long of a name in my
65 * opinion, which is why I've chosen to have the files
66 * containing exception store implementations be 'dm-exstore-<type_name>'.
67 * If you want your module to be autoloaded, you will follow this
68 * naming convention.
69 *
70 * Returns: dm_exception_store_type* on success, NULL on failure
71 */
72static struct dm_exception_store_type *get_type(const char *type_name)
73{
74 char *p, *type_name_dup;
75 struct dm_exception_store_type *type;
76
77 type = _get_exception_store_type(type_name);
78 if (type)
79 return type;
80
81 type_name_dup = kstrdup(type_name, GFP_KERNEL);
82 if (!type_name_dup) {
83 DMERR("No memory left to attempt load for \"%s\"", type_name);
84 return NULL;
85 }
86
87 while (request_module("dm-exstore-%s", type_name_dup) ||
88 !(type = _get_exception_store_type(type_name))) {
89 p = strrchr(type_name_dup, '-');
90 if (!p)
91 break;
92 p[0] = '\0';
93 }
94
95 if (!type)
96 DMWARN("Module for exstore type \"%s\" not found.", type_name);
97
98 kfree(type_name_dup);
99
100 return type;
101}
102
103static void put_type(struct dm_exception_store_type *type)
104{
105 spin_lock(&_lock);
106 module_put(type->module);
107 spin_unlock(&_lock);
108}
109
110int dm_exception_store_type_register(struct dm_exception_store_type *type)
111{
112 int r = 0;
113
114 spin_lock(&_lock);
115 if (!__find_exception_store_type(type->name))
116 list_add(&type->list, &_exception_store_types);
117 else
118 r = -EEXIST;
119 spin_unlock(&_lock);
120
121 return r;
122}
123EXPORT_SYMBOL(dm_exception_store_type_register);
124
125int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
126{
127 spin_lock(&_lock);
128
129 if (!__find_exception_store_type(type->name)) {
130 spin_unlock(&_lock);
131 return -EINVAL;
132 }
133
134 list_del(&type->list);
135
136 spin_unlock(&_lock);
137
138 return 0;
139}
140EXPORT_SYMBOL(dm_exception_store_type_unregister);
141
142static int set_chunk_size(struct dm_exception_store *store,
143 const char *chunk_size_arg, char **error)
144{
145 unsigned chunk_size;
146
147 if (kstrtouint(chunk_size_arg, 10, &chunk_size)) {
148 *error = "Invalid chunk size";
149 return -EINVAL;
150 }
151
152 if (!chunk_size) {
153 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
154 return 0;
155 }
156
157 return dm_exception_store_set_chunk_size(store, chunk_size, error);
158}
159
160int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
161 unsigned chunk_size,
162 char **error)
163{
164 /* Check chunk_size is a power of 2 */
165 if (!is_power_of_2(chunk_size)) {
166 *error = "Chunk size is not a power of 2";
167 return -EINVAL;
168 }
169
170 /* Validate the chunk size against the device block size */
171 if (chunk_size %
172 (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
173 chunk_size %
174 (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
175 *error = "Chunk size is not a multiple of device blocksize";
176 return -EINVAL;
177 }
178
179 if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
180 *error = "Chunk size is too high";
181 return -EINVAL;
182 }
183
184 store->chunk_size = chunk_size;
185 store->chunk_mask = chunk_size - 1;
186 store->chunk_shift = __ffs(chunk_size);
187
188 return 0;
189}
190
191int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
192 struct dm_snapshot *snap,
193 unsigned *args_used,
194 struct dm_exception_store **store)
195{
196 int r = 0;
197 struct dm_exception_store_type *type = NULL;
198 struct dm_exception_store *tmp_store;
199 char persistent;
200
201 if (argc < 2) {
202 ti->error = "Insufficient exception store arguments";
203 return -EINVAL;
204 }
205
206 tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL);
207 if (!tmp_store) {
208 ti->error = "Exception store allocation failed";
209 return -ENOMEM;
210 }
211
212 persistent = toupper(*argv[0]);
213 if (persistent == 'P')
214 type = get_type("P");
215 else if (persistent == 'N')
216 type = get_type("N");
217 else {
218 ti->error = "Exception store type is not P or N";
219 r = -EINVAL;
220 goto bad_type;
221 }
222
223 if (!type) {
224 ti->error = "Exception store type not recognised";
225 r = -EINVAL;
226 goto bad_type;
227 }
228
229 tmp_store->type = type;
230 tmp_store->snap = snap;
231
232 r = set_chunk_size(tmp_store, argv[1], &ti->error);
233 if (r)
234 goto bad;
235
236 r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL));
237 if (r) {
238 ti->error = "Exception store type constructor failed";
239 goto bad;
240 }
241
242 *args_used = 2;
243 *store = tmp_store;
244 return 0;
245
246bad:
247 put_type(type);
248bad_type:
249 kfree(tmp_store);
250 return r;
251}
252EXPORT_SYMBOL(dm_exception_store_create);
253
254void dm_exception_store_destroy(struct dm_exception_store *store)
255{
256 store->type->dtr(store);
257 put_type(store->type);
258 kfree(store);
259}
260EXPORT_SYMBOL(dm_exception_store_destroy);
261
262int dm_exception_store_init(void)
263{
264 int r;
265
266 r = dm_transient_snapshot_init();
267 if (r) {
268 DMERR("Unable to register transient exception store type.");
269 goto transient_fail;
270 }
271
272 r = dm_persistent_snapshot_init();
273 if (r) {
274 DMERR("Unable to register persistent exception store type");
275 goto persistent_fail;
276 }
277
278 return 0;
279
280persistent_fail:
281 dm_transient_snapshot_exit();
282transient_fail:
283 return r;
284}
285
286void dm_exception_store_exit(void)
287{
288 dm_persistent_snapshot_exit();
289 dm_transient_snapshot_exit();
290}
291