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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +00003 * Copyright (C) 2006-2008 Red Hat GmbH
Linus Torvalds1da177e2005-04-16 15:20:36 -07004 *
5 * This file is released under the GPL.
6 */
7
Jonathan Brassowaea53d92009-01-06 03:05:15 +00008#include "dm-exception-store.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -07009
Jonathan Brassowfee19982009-04-02 19:55:34 +010010#include <linux/ctype.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070011#include <linux/mm.h>
12#include <linux/pagemap.h>
13#include <linux/vmalloc.h>
14#include <linux/slab.h>
15
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +000016#define DM_MSG_PREFIX "snapshot exception stores"
Alasdair G Kergon72d94862006-06-26 00:27:35 -070017
Jonathan Brassow493df712009-04-02 19:55:31 +010018static 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
Jonathan Brassowfee19982009-04-02 19:55:34 +0100141/*
142 * Round a number up to the nearest 'size' boundary. size must
143 * be a power of 2.
144 */
145static ulong round_up(ulong n, ulong size)
146{
147 size--;
148 return (n + size) & ~size;
149}
150
151static int set_chunk_size(struct dm_exception_store *store,
152 const char *chunk_size_arg, char **error)
153{
154 unsigned long chunk_size_ulong;
155 char *value;
156
157 chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
158 if (*chunk_size_arg == '\0' || *value != '\0') {
159 *error = "Invalid chunk size";
160 return -EINVAL;
161 }
162
163 if (!chunk_size_ulong) {
164 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
165 return 0;
166 }
167
168 /*
169 * Chunk size must be multiple of page size. Silently
170 * round up if it's not.
171 */
172 chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9);
173
174 /* Check chunk_size is a power of 2 */
175 if (!is_power_of_2(chunk_size_ulong)) {
176 *error = "Chunk size is not a power of 2";
177 return -EINVAL;
178 }
179
180 /* Validate the chunk size against the device block size */
Martin K. Petersene1defc42009-05-22 17:17:49 -0400181 if (chunk_size_ulong % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
Jonathan Brassowfee19982009-04-02 19:55:34 +0100182 *error = "Chunk size is not a multiple of device blocksize";
183 return -EINVAL;
184 }
185
186 store->chunk_size = chunk_size_ulong;
187 store->chunk_mask = chunk_size_ulong - 1;
188 store->chunk_shift = ffs(chunk_size_ulong) - 1;
189
190 return 0;
191}
192
193int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
194 unsigned *args_used,
Jonathan Brassow493df712009-04-02 19:55:31 +0100195 struct dm_exception_store **store)
196{
197 int r = 0;
198 struct dm_exception_store_type *type;
199 struct dm_exception_store *tmp_store;
Jonathan Brassowfee19982009-04-02 19:55:34 +0100200 char persistent;
201
202 if (argc < 3) {
203 ti->error = "Insufficient exception store arguments";
204 return -EINVAL;
205 }
Jonathan Brassow493df712009-04-02 19:55:31 +0100206
207 tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
Jonathan Brassowfee19982009-04-02 19:55:34 +0100208 if (!tmp_store) {
209 ti->error = "Exception store allocation failed";
Jonathan Brassow493df712009-04-02 19:55:31 +0100210 return -ENOMEM;
Jonathan Brassowfee19982009-04-02 19:55:34 +0100211 }
Jonathan Brassow493df712009-04-02 19:55:31 +0100212
Jonathan Brassowfee19982009-04-02 19:55:34 +0100213 persistent = toupper(*argv[1]);
214 if (persistent != 'P' && persistent != 'N') {
215 ti->error = "Persistent flag is not P or N";
Jonathan Brassow493df712009-04-02 19:55:31 +0100216 return -EINVAL;
217 }
218
Jonathan Brassowf6bd4eb2009-06-22 10:12:15 +0100219 type = get_type(&persistent);
Jonathan Brassowfee19982009-04-02 19:55:34 +0100220 if (!type) {
221 ti->error = "Exception store type not recognised";
222 r = -EINVAL;
223 goto bad_type;
224 }
225
Jonathan Brassow493df712009-04-02 19:55:31 +0100226 tmp_store->type = type;
Jonathan Brassow0cea9c72009-04-02 19:55:32 +0100227 tmp_store->ti = ti;
Jonathan Brassow493df712009-04-02 19:55:31 +0100228
Jonathan Brassowfee19982009-04-02 19:55:34 +0100229 r = dm_get_device(ti, argv[0], 0, 0,
230 FMODE_READ | FMODE_WRITE, &tmp_store->cow);
231 if (r) {
232 ti->error = "Cannot get COW device";
233 goto bad_cow;
234 }
Jonathan Brassowd0216842009-04-02 19:55:32 +0100235
Jonathan Brassowfee19982009-04-02 19:55:34 +0100236 r = set_chunk_size(tmp_store, argv[2], &ti->error);
237 if (r)
238 goto bad_cow;
Jonathan Brassow49beb2b2009-04-02 19:55:33 +0100239
Jonathan Brassow493df712009-04-02 19:55:31 +0100240 r = type->ctr(tmp_store, 0, NULL);
241 if (r) {
Jonathan Brassowfee19982009-04-02 19:55:34 +0100242 ti->error = "Exception store type constructor failed";
243 goto bad_ctr;
Jonathan Brassow493df712009-04-02 19:55:31 +0100244 }
245
Jonathan Brassowfee19982009-04-02 19:55:34 +0100246 *args_used = 3;
Jonathan Brassow493df712009-04-02 19:55:31 +0100247 *store = tmp_store;
248 return 0;
Jonathan Brassowfee19982009-04-02 19:55:34 +0100249
250bad_ctr:
251 dm_put_device(ti, tmp_store->cow);
252bad_cow:
253 put_type(type);
254bad_type:
255 kfree(tmp_store);
256 return r;
Jonathan Brassow493df712009-04-02 19:55:31 +0100257}
258EXPORT_SYMBOL(dm_exception_store_create);
259
260void dm_exception_store_destroy(struct dm_exception_store *store)
261{
262 store->type->dtr(store);
Jonathan Brassowfee19982009-04-02 19:55:34 +0100263 dm_put_device(store->ti, store->cow);
Jonathan Brassow493df712009-04-02 19:55:31 +0100264 put_type(store->type);
265 kfree(store);
266}
267EXPORT_SYMBOL(dm_exception_store_destroy);
268
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000269int dm_exception_store_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270{
271 int r;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000273 r = dm_transient_snapshot_init();
274 if (r) {
275 DMERR("Unable to register transient exception store type.");
276 goto transient_fail;
277 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700278
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000279 r = dm_persistent_snapshot_init();
280 if (r) {
281 DMERR("Unable to register persistent exception store type");
282 goto persistent_fail;
283 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000287persistent_fail:
288 dm_persistent_snapshot_exit();
289transient_fail:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 return r;
291}
292
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000293void dm_exception_store_exit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294{
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000295 dm_persistent_snapshot_exit();
296 dm_transient_snapshot_exit();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297}