dm-exception-store.c revision c24110450650f17f7d3ba4fbe01f01ac5a115456 
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
18static LIST_HEAD(_exception_store_types);
19static DEFINE_SPINLOCK(_lock);
20
21static 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
32static 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 */
71static 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
102static 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
109int 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}
122EXPORT_SYMBOL(dm_exception_store_type_register);
123
124int 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}
139EXPORT_SYMBOL(dm_exception_store_type_unregister);
140
141static int set_chunk_size(struct dm_exception_store *store,
142			  const char *chunk_size_arg, char **error)
143{
144	unsigned long chunk_size_ulong;
145	char *value;
146
147	chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
148	if (*chunk_size_arg == '\0' || *value != '\0' ||
149	    chunk_size_ulong > UINT_MAX) {
150		*error = "Invalid chunk size";
151		return -EINVAL;
152	}
153
154	if (!chunk_size_ulong) {
155		store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
156		return 0;
157	}
158
159	return dm_exception_store_set_chunk_size(store,
160						 (unsigned) chunk_size_ulong,
161						 error);
162}
163
164int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
165				      unsigned chunk_size,
166				      char **error)
167{
168	/* Check chunk_size is a power of 2 */
169	if (!is_power_of_2(chunk_size)) {
170		*error = "Chunk size is not a power of 2";
171		return -EINVAL;
172	}
173
174	/* Validate the chunk size against the device block size */
175	if (chunk_size %
176	    (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
177	    chunk_size %
178	    (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
179		*error = "Chunk size is not a multiple of device blocksize";
180		return -EINVAL;
181	}
182
183	if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
184		*error = "Chunk size is too high";
185		return -EINVAL;
186	}
187
188	store->chunk_size = chunk_size;
189	store->chunk_mask = chunk_size - 1;
190	store->chunk_shift = ffs(chunk_size) - 1;
191
192	return 0;
193}
194
195int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
196			      struct dm_snapshot *snap,
197			      unsigned *args_used,
198			      struct dm_exception_store **store)
199{
200	int r = 0;
201	struct dm_exception_store_type *type = NULL;
202	struct dm_exception_store *tmp_store;
203	char persistent;
204
205	if (argc < 2) {
206		ti->error = "Insufficient exception store arguments";
207		return -EINVAL;
208	}
209
210	tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
211	if (!tmp_store) {
212		ti->error = "Exception store allocation failed";
213		return -ENOMEM;
214	}
215
216	persistent = toupper(*argv[0]);
217	if (persistent == 'P')
218		type = get_type("P");
219	else if (persistent == 'N')
220		type = get_type("N");
221	else {
222		ti->error = "Persistent flag is not P or N";
223		r = -EINVAL;
224		goto bad_type;
225	}
226
227	if (!type) {
228		ti->error = "Exception store type not recognised";
229		r = -EINVAL;
230		goto bad_type;
231	}
232
233	tmp_store->type = type;
234	tmp_store->snap = snap;
235
236	r = set_chunk_size(tmp_store, argv[1], &ti->error);
237	if (r)
238		goto bad;
239
240	r = type->ctr(tmp_store, 0, NULL);
241	if (r) {
242		ti->error = "Exception store type constructor failed";
243		goto bad;
244	}
245
246	*args_used = 2;
247	*store = tmp_store;
248	return 0;
249
250bad:
251	put_type(type);
252bad_type:
253	kfree(tmp_store);
254	return r;
255}
256EXPORT_SYMBOL(dm_exception_store_create);
257
258void dm_exception_store_destroy(struct dm_exception_store *store)
259{
260	store->type->dtr(store);
261	put_type(store->type);
262	kfree(store);
263}
264EXPORT_SYMBOL(dm_exception_store_destroy);
265
266int dm_exception_store_init(void)
267{
268	int r;
269
270	r = dm_transient_snapshot_init();
271	if (r) {
272		DMERR("Unable to register transient exception store type.");
273		goto transient_fail;
274	}
275
276	r = dm_persistent_snapshot_init();
277	if (r) {
278		DMERR("Unable to register persistent exception store type");
279		goto persistent_fail;
280	}
281
282	return 0;
283
284persistent_fail:
285	dm_persistent_snapshot_exit();
286transient_fail:
287	return r;
288}
289
290void dm_exception_store_exit(void)
291{
292	dm_persistent_snapshot_exit();
293	dm_transient_snapshot_exit();
294}
295