Root/drivers/md/dm-exception-store.c

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

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