1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
4 * Copyright (C) 2006-2008 Red Hat GmbH
5 *
6 * This file is released under the GPL.
7 */
8
9 #include "dm-exception-store.h"
10
11 #include <linux/ctype.h>
12 #include <linux/mm.h>
13 #include <linux/pagemap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17
18 #define DM_MSG_PREFIX "snapshot exception stores"
19
20 static LIST_HEAD(_exception_store_types);
21 static DEFINE_SPINLOCK(_lock);
22
__find_exception_store_type(const char * name)23 static struct dm_exception_store_type *__find_exception_store_type(const char *name)
24 {
25 struct dm_exception_store_type *type;
26
27 list_for_each_entry(type, &_exception_store_types, list)
28 if (!strcmp(name, type->name))
29 return type;
30
31 return NULL;
32 }
33
_get_exception_store_type(const char * name)34 static struct dm_exception_store_type *_get_exception_store_type(const char *name)
35 {
36 struct dm_exception_store_type *type;
37
38 spin_lock(&_lock);
39
40 type = __find_exception_store_type(name);
41
42 if (type && !try_module_get(type->module))
43 type = NULL;
44
45 spin_unlock(&_lock);
46
47 return type;
48 }
49
50 /*
51 * get_type
52 * @type_name
53 *
54 * Attempt to retrieve the dm_exception_store_type by name. If not already
55 * available, attempt to load the appropriate module.
56 *
57 * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
58 * Modules may contain multiple types.
59 * This function will first try the module "dm-exstore-<type_name>",
60 * then truncate 'type_name' on the last '-' and try again.
61 *
62 * For example, if type_name was "clustered-shared", it would search
63 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
64 *
65 * 'dm-exception-store-<type_name>' is too long of a name in my
66 * opinion, which is why I've chosen to have the files
67 * containing exception store implementations be 'dm-exstore-<type_name>'.
68 * If you want your module to be autoloaded, you will follow this
69 * naming convention.
70 *
71 * Returns: dm_exception_store_type* on success, NULL on failure
72 */
get_type(const char * type_name)73 static struct dm_exception_store_type *get_type(const char *type_name)
74 {
75 char *p, *type_name_dup;
76 struct dm_exception_store_type *type;
77
78 type = _get_exception_store_type(type_name);
79 if (type)
80 return type;
81
82 type_name_dup = kstrdup(type_name, GFP_KERNEL);
83 if (!type_name_dup) {
84 DMERR("No memory left to attempt load for \"%s\"", type_name);
85 return NULL;
86 }
87
88 while (request_module("dm-exstore-%s", type_name_dup) ||
89 !(type = _get_exception_store_type(type_name))) {
90 p = strrchr(type_name_dup, '-');
91 if (!p)
92 break;
93 p[0] = '\0';
94 }
95
96 if (!type)
97 DMWARN("Module for exstore type \"%s\" not found.", type_name);
98
99 kfree(type_name_dup);
100
101 return type;
102 }
103
put_type(struct dm_exception_store_type * type)104 static void put_type(struct dm_exception_store_type *type)
105 {
106 spin_lock(&_lock);
107 module_put(type->module);
108 spin_unlock(&_lock);
109 }
110
dm_exception_store_type_register(struct dm_exception_store_type * type)111 int dm_exception_store_type_register(struct dm_exception_store_type *type)
112 {
113 int r = 0;
114
115 spin_lock(&_lock);
116 if (!__find_exception_store_type(type->name))
117 list_add(&type->list, &_exception_store_types);
118 else
119 r = -EEXIST;
120 spin_unlock(&_lock);
121
122 return r;
123 }
124 EXPORT_SYMBOL(dm_exception_store_type_register);
125
dm_exception_store_type_unregister(struct dm_exception_store_type * type)126 int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
127 {
128 spin_lock(&_lock);
129
130 if (!__find_exception_store_type(type->name)) {
131 spin_unlock(&_lock);
132 return -EINVAL;
133 }
134
135 list_del(&type->list);
136
137 spin_unlock(&_lock);
138
139 return 0;
140 }
141 EXPORT_SYMBOL(dm_exception_store_type_unregister);
142
set_chunk_size(struct dm_exception_store * store,const char * chunk_size_arg,char ** error)143 static int set_chunk_size(struct dm_exception_store *store,
144 const char *chunk_size_arg, char **error)
145 {
146 unsigned int chunk_size;
147
148 if (kstrtouint(chunk_size_arg, 10, &chunk_size)) {
149 *error = "Invalid chunk size";
150 return -EINVAL;
151 }
152
153 if (!chunk_size) {
154 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
155 return 0;
156 }
157
158 return dm_exception_store_set_chunk_size(store, chunk_size, error);
159 }
160
dm_exception_store_set_chunk_size(struct dm_exception_store * store,unsigned int chunk_size,char ** error)161 int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
162 unsigned int chunk_size,
163 char **error)
164 {
165 /* Check chunk_size is a power of 2 */
166 if (!is_power_of_2(chunk_size)) {
167 *error = "Chunk size is not a power of 2";
168 return -EINVAL;
169 }
170
171 /* Validate the chunk size against the device block size */
172 if (chunk_size %
173 (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
174 chunk_size %
175 (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
176 *error = "Chunk size is not a multiple of device blocksize";
177 return -EINVAL;
178 }
179
180 if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
181 *error = "Chunk size is too high";
182 return -EINVAL;
183 }
184
185 store->chunk_size = chunk_size;
186 store->chunk_mask = chunk_size - 1;
187 store->chunk_shift = __ffs(chunk_size);
188
189 return 0;
190 }
191
dm_exception_store_create(struct dm_target * ti,int argc,char ** argv,struct dm_snapshot * snap,unsigned int * args_used,struct dm_exception_store ** store)192 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
193 struct dm_snapshot *snap,
194 unsigned int *args_used,
195 struct dm_exception_store **store)
196 {
197 int r = 0;
198 struct dm_exception_store_type *type = NULL;
199 struct dm_exception_store *tmp_store;
200 char persistent;
201
202 if (argc < 2) {
203 ti->error = "Insufficient exception store arguments";
204 return -EINVAL;
205 }
206
207 tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL);
208 if (!tmp_store) {
209 ti->error = "Exception store allocation failed";
210 return -ENOMEM;
211 }
212
213 persistent = toupper(*argv[0]);
214 if (persistent == 'P')
215 type = get_type("P");
216 else if (persistent == 'N')
217 type = get_type("N");
218 else {
219 ti->error = "Exception store type is not P or N";
220 r = -EINVAL;
221 goto bad_type;
222 }
223
224 if (!type) {
225 ti->error = "Exception store type not recognised";
226 r = -EINVAL;
227 goto bad_type;
228 }
229
230 tmp_store->type = type;
231 tmp_store->snap = snap;
232
233 r = set_chunk_size(tmp_store, argv[1], &ti->error);
234 if (r)
235 goto bad;
236
237 r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL));
238 if (r) {
239 ti->error = "Exception store type constructor failed";
240 goto bad;
241 }
242
243 *args_used = 2;
244 *store = tmp_store;
245 return 0;
246
247 bad:
248 put_type(type);
249 bad_type:
250 kfree(tmp_store);
251 return r;
252 }
253 EXPORT_SYMBOL(dm_exception_store_create);
254
dm_exception_store_destroy(struct dm_exception_store * store)255 void dm_exception_store_destroy(struct dm_exception_store *store)
256 {
257 store->type->dtr(store);
258 put_type(store->type);
259 kfree(store);
260 }
261 EXPORT_SYMBOL(dm_exception_store_destroy);
262
dm_exception_store_init(void)263 int dm_exception_store_init(void)
264 {
265 int r;
266
267 r = dm_transient_snapshot_init();
268 if (r) {
269 DMERR("Unable to register transient exception store type.");
270 goto transient_fail;
271 }
272
273 r = dm_persistent_snapshot_init();
274 if (r) {
275 DMERR("Unable to register persistent exception store type");
276 goto persistent_fail;
277 }
278
279 return 0;
280
281 persistent_fail:
282 dm_transient_snapshot_exit();
283 transient_fail:
284 return r;
285 }
286
dm_exception_store_exit(void)287 void dm_exception_store_exit(void)
288 {
289 dm_persistent_snapshot_exit();
290 dm_transient_snapshot_exit();
291 }
292