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/slab.h>
15
16 #define DM_MSG_PREFIX "snapshot exception stores"
17
18 static LIST_HEAD(_exception_store_types);
19 static DEFINE_SPINLOCK(_lock);
20
21 static struct dm_exception_store_type *__find_exception_store_type(const char *name)
22 {
23 struct dm_exception_store_type *type;
24
25 list_for_each_entry(type, &_exception_store_types, list)
26 if (!strcmp(name, type->name))
27 return type;
28
29 return NULL;
30 }
31
32 static struct dm_exception_store_type *_get_exception_store_type(const char *name)
33 {
34 struct dm_exception_store_type *type;
35
36 spin_lock(&_lock);
37
38 type = __find_exception_store_type(name);
39
40 if (type && !try_module_get(type->module))
41 type = NULL;
42
43 spin_unlock(&_lock);
44
45 return type;
46 }
47
48 /*
49 * get_type
50 * @type_name
51 *
52 * Attempt to retrieve the dm_exception_store_type by name. If not already
53 * available, attempt to load the appropriate module.
54 *
55 * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
56 * Modules may contain multiple types.
57 * This function will first try the module "dm-exstore-<type_name>",
58 * then truncate 'type_name' on the last '-' and try again.
59 *
60 * For example, if type_name was "clustered-shared", it would search
61 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
62 *
63 * 'dm-exception-store-<type_name>' is too long of a name in my
64 * opinion, which is why I've chosen to have the files
65 * containing exception store implementations be 'dm-exstore-<type_name>'.
66 * If you want your module to be autoloaded, you will follow this
67 * naming convention.
68 *
69 * Returns: dm_exception_store_type* on success, NULL on failure
70 */
71 static struct dm_exception_store_type *get_type(const char *type_name)
72 {
73 char *p, *type_name_dup;
74 struct dm_exception_store_type *type;
75
76 type = _get_exception_store_type(type_name);
77 if (type)
78 return type;
79
80 type_name_dup = kstrdup(type_name, GFP_KERNEL);
81 if (!type_name_dup) {
82 DMERR("No memory left to attempt load for \"%s\"", type_name);
83 return NULL;
84 }
85
86 while (request_module("dm-exstore-%s", type_name_dup) ||
87 !(type = _get_exception_store_type(type_name))) {
88 p = strrchr(type_name_dup, '-');
89 if (!p)
90 break;
91 p[0] = '\0';
92 }
93
94 if (!type)
95 DMWARN("Module for exstore type \"%s\" not found.", type_name);
96
97 kfree(type_name_dup);
98
99 return type;
100 }
101
102 static void put_type(struct dm_exception_store_type *type)
103 {
104 spin_lock(&_lock);
105 module_put(type->module);
106 spin_unlock(&_lock);
107 }
108
109 int dm_exception_store_type_register(struct dm_exception_store_type *type)
110 {
111 int r = 0;
112
113 spin_lock(&_lock);
114 if (!__find_exception_store_type(type->name))
115 list_add(&type->list, &_exception_store_types);
116 else
117 r = -EEXIST;
118 spin_unlock(&_lock);
119
120 return r;
121 }
122 EXPORT_SYMBOL(dm_exception_store_type_register);
123
124 int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
125 {
126 spin_lock(&_lock);
127
128 if (!__find_exception_store_type(type->name)) {
129 spin_unlock(&_lock);
130 return -EINVAL;
131 }
132
133 list_del(&type->list);
134
135 spin_unlock(&_lock);
136
137 return 0;
138 }
139 EXPORT_SYMBOL(dm_exception_store_type_unregister);
140
141 /*
142 * Round a number up to the nearest 'size' boundary. size must
143 * be a power of 2.
144 */
145 static ulong round_up(ulong n, ulong size)
146 {
147 size--;
148 return (n + size) & ~size;
149 }
150
151 static int set_chunk_size(struct dm_exception_store *store,
152 const char *chunk_size_arg, char **error)
153 {
154 unsigned long chunk_size_ulong;
155 char *value;
156
157 chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
158 if (*chunk_size_arg == '\0' || *value != '\0' ||
159 chunk_size_ulong > UINT_MAX) {
160 *error = "Invalid chunk size";
161 return -EINVAL;
162 }
163
164 if (!chunk_size_ulong) {
165 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
166 return 0;
167 }
168
169 /*
170 * Chunk size must be multiple of page size. Silently
171 * round up if it's not.
172 */
173 chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9);
174
175 return dm_exception_store_set_chunk_size(store,
176 (unsigned) chunk_size_ulong,
177 error);
178 }
179
180 int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
181 unsigned chunk_size,
182 char **error)
183 {
184 /* Check chunk_size is a power of 2 */
185 if (!is_power_of_2(chunk_size)) {
186 *error = "Chunk size is not a power of 2";
187 return -EINVAL;
188 }
189
190 /* Validate the chunk size against the device block size */
191 if (chunk_size % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
192 *error = "Chunk size is not a multiple of device blocksize";
193 return -EINVAL;
194 }
195
196 if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
197 *error = "Chunk size is too high";
198 return -EINVAL;
199 }
200
201 store->chunk_size = chunk_size;
202 store->chunk_mask = chunk_size - 1;
203 store->chunk_shift = ffs(chunk_size) - 1;
204
205 return 0;
206 }
207
208 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
209 unsigned *args_used,
210 struct dm_exception_store **store)
211 {
212 int r = 0;
213 struct dm_exception_store_type *type = NULL;
214 struct dm_exception_store *tmp_store;
215 char persistent;
216
217 if (argc < 3) {
218 ti->error = "Insufficient exception store arguments";
219 return -EINVAL;
220 }
221
222 tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
223 if (!tmp_store) {
224 ti->error = "Exception store allocation failed";
225 return -ENOMEM;
226 }
227
228 persistent = toupper(*argv[1]);
229 if (persistent == 'P')
230 type = get_type("P");
231 else if (persistent == 'N')
232 type = get_type("N");
233 else {
234 ti->error = "Persistent flag is not P or N";
235 return -EINVAL;
236 }
237
238 if (!type) {
239 ti->error = "Exception store type not recognised";
240 r = -EINVAL;
241 goto bad_type;
242 }
243
244 tmp_store->type = type;
245 tmp_store->ti = ti;
246
247 r = dm_get_device(ti, argv[0], 0, 0,
248 FMODE_READ | FMODE_WRITE, &tmp_store->cow);
249 if (r) {
250 ti->error = "Cannot get COW device";
251 goto bad_cow;
252 }
253
254 r = set_chunk_size(tmp_store, argv[2], &ti->error);
255 if (r)
256 goto bad_ctr;
257
258 r = type->ctr(tmp_store, 0, NULL);
259 if (r) {
260 ti->error = "Exception store type constructor failed";
261 goto bad_ctr;
262 }
263
264 *args_used = 3;
265 *store = tmp_store;
266 return 0;
267
268 bad_ctr:
269 dm_put_device(ti, tmp_store->cow);
270 bad_cow:
271 put_type(type);
272 bad_type:
273 kfree(tmp_store);
274 return r;
275 }
276 EXPORT_SYMBOL(dm_exception_store_create);
277
278 void dm_exception_store_destroy(struct dm_exception_store *store)
279 {
280 store->type->dtr(store);
281 dm_put_device(store->ti, store->cow);
282 put_type(store->type);
283 kfree(store);
284 }
285 EXPORT_SYMBOL(dm_exception_store_destroy);
286
287 int dm_exception_store_init(void)
288 {
289 int r;
290
291 r = dm_transient_snapshot_init();
292 if (r) {
293 DMERR("Unable to register transient exception store type.");
294 goto transient_fail;
295 }
296
297 r = dm_persistent_snapshot_init();
298 if (r) {
299 DMERR("Unable to register persistent exception store type");
300 goto persistent_fail;
301 }
302
303 return 0;
304
305 persistent_fail:
306 dm_persistent_snapshot_exit();
307 transient_fail:
308 return r;
309 }
310
311 void dm_exception_store_exit(void)
312 {
313 dm_persistent_snapshot_exit();
314 dm_transient_snapshot_exit();
315 }
316
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