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 long chunk_size_ulong;
146 	char *value;
147 
148 	chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
149 	if (*chunk_size_arg == '\0' || *value != '\0' ||
150 	    chunk_size_ulong > UINT_MAX) {
151 		*error = "Invalid chunk size";
152 		return -EINVAL;
153 	}
154 
155 	if (!chunk_size_ulong) {
156 		store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
157 		return 0;
158 	}
159 
160 	return dm_exception_store_set_chunk_size(store,
161 						 (unsigned) chunk_size_ulong,
162 						 error);
163 }
164 
165 int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
166 				      unsigned chunk_size,
167 				      char **error)
168 {
169 	/* Check chunk_size is a power of 2 */
170 	if (!is_power_of_2(chunk_size)) {
171 		*error = "Chunk size is not a power of 2";
172 		return -EINVAL;
173 	}
174 
175 	/* Validate the chunk size against the device block size */
176 	if (chunk_size %
177 	    (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
178 	    chunk_size %
179 	    (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
180 		*error = "Chunk size is not a multiple of device blocksize";
181 		return -EINVAL;
182 	}
183 
184 	if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
185 		*error = "Chunk size is too high";
186 		return -EINVAL;
187 	}
188 
189 	store->chunk_size = chunk_size;
190 	store->chunk_mask = chunk_size - 1;
191 	store->chunk_shift = ffs(chunk_size) - 1;
192 
193 	return 0;
194 }
195 
196 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
197 			      struct dm_snapshot *snap,
198 			      unsigned *args_used,
199 			      struct dm_exception_store **store)
200 {
201 	int r = 0;
202 	struct dm_exception_store_type *type = NULL;
203 	struct dm_exception_store *tmp_store;
204 	char persistent;
205 
206 	if (argc < 2) {
207 		ti->error = "Insufficient exception store arguments";
208 		return -EINVAL;
209 	}
210 
211 	tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
212 	if (!tmp_store) {
213 		ti->error = "Exception store allocation failed";
214 		return -ENOMEM;
215 	}
216 
217 	persistent = toupper(*argv[0]);
218 	if (persistent == 'P')
219 		type = get_type("P");
220 	else if (persistent == 'N')
221 		type = get_type("N");
222 	else {
223 		ti->error = "Persistent flag is not P or N";
224 		r = -EINVAL;
225 		goto bad_type;
226 	}
227 
228 	if (!type) {
229 		ti->error = "Exception store type not recognised";
230 		r = -EINVAL;
231 		goto bad_type;
232 	}
233 
234 	tmp_store->type = type;
235 	tmp_store->snap = snap;
236 
237 	r = set_chunk_size(tmp_store, argv[1], &ti->error);
238 	if (r)
239 		goto bad;
240 
241 	r = type->ctr(tmp_store, 0, NULL);
242 	if (r) {
243 		ti->error = "Exception store type constructor failed";
244 		goto bad;
245 	}
246 
247 	*args_used = 2;
248 	*store = tmp_store;
249 	return 0;
250 
251 bad:
252 	put_type(type);
253 bad_type:
254 	kfree(tmp_store);
255 	return r;
256 }
257 EXPORT_SYMBOL(dm_exception_store_create);
258 
259 void dm_exception_store_destroy(struct dm_exception_store *store)
260 {
261 	store->type->dtr(store);
262 	put_type(store->type);
263 	kfree(store);
264 }
265 EXPORT_SYMBOL(dm_exception_store_destroy);
266 
267 int dm_exception_store_init(void)
268 {
269 	int r;
270 
271 	r = dm_transient_snapshot_init();
272 	if (r) {
273 		DMERR("Unable to register transient exception store type.");
274 		goto transient_fail;
275 	}
276 
277 	r = dm_persistent_snapshot_init();
278 	if (r) {
279 		DMERR("Unable to register persistent exception store type");
280 		goto persistent_fail;
281 	}
282 
283 	return 0;
284 
285 persistent_fail:
286 	dm_transient_snapshot_exit();
287 transient_fail:
288 	return r;
289 }
290 
291 void dm_exception_store_exit(void)
292 {
293 	dm_persistent_snapshot_exit();
294 	dm_transient_snapshot_exit();
295 }
296