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