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 
19 static LIST_HEAD(_exception_store_types);
20 static DEFINE_SPINLOCK(_lock);
21 
22 static 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 
33 static 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  */
72 static 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 
103 static 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 
110 int 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 }
123 EXPORT_SYMBOL(dm_exception_store_type_register);
124 
125 int 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 }
140 EXPORT_SYMBOL(dm_exception_store_type_unregister);
141 
142 static 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 
160 int 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) - 1;
187 
188 	return 0;
189 }
190 
191 int 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 = kmalloc(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 = "Persistent flag 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, 0, 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 
246 bad:
247 	put_type(type);
248 bad_type:
249 	kfree(tmp_store);
250 	return r;
251 }
252 EXPORT_SYMBOL(dm_exception_store_create);
253 
254 void dm_exception_store_destroy(struct dm_exception_store *store)
255 {
256 	store->type->dtr(store);
257 	put_type(store->type);
258 	kfree(store);
259 }
260 EXPORT_SYMBOL(dm_exception_store_destroy);
261 
262 int 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 
280 persistent_fail:
281 	dm_transient_snapshot_exit();
282 transient_fail:
283 	return r;
284 }
285 
286 void dm_exception_store_exit(void)
287 {
288 	dm_persistent_snapshot_exit();
289 	dm_transient_snapshot_exit();
290 }
291