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