blob: 835cf95b857fa6cbef32c0c6d0d474e03909221a [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 2001 Sistina Software (UK) Limited
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm.h"
8
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/kmod.h>
12#include <linux/bio.h>
13#include <linux/slab.h>
14
Alasdair G Kergon72d94862006-06-26 00:27:35 -070015#define DM_MSG_PREFIX "target"
16
Linus Torvalds1da177e2005-04-16 15:20:36 -070017struct tt_internal {
18 struct target_type tt;
19
20 struct list_head list;
21 long use;
22};
23
24static LIST_HEAD(_targets);
25static DECLARE_RWSEM(_lock);
26
27#define DM_MOD_NAME_SIZE 32
28
29static inline struct tt_internal *__find_target_type(const char *name)
30{
31 struct tt_internal *ti;
32
33 list_for_each_entry (ti, &_targets, list)
34 if (!strcmp(name, ti->tt.name))
35 return ti;
36
37 return NULL;
38}
39
40static struct tt_internal *get_target_type(const char *name)
41{
42 struct tt_internal *ti;
43
44 down_read(&_lock);
45
46 ti = __find_target_type(name);
47 if (ti) {
48 if ((ti->use == 0) && !try_module_get(ti->tt.module))
49 ti = NULL;
50 else
51 ti->use++;
52 }
53
54 up_read(&_lock);
55 return ti;
56}
57
58static void load_module(const char *name)
59{
60 request_module("dm-%s", name);
61}
62
63struct target_type *dm_get_target_type(const char *name)
64{
65 struct tt_internal *ti = get_target_type(name);
66
67 if (!ti) {
68 load_module(name);
69 ti = get_target_type(name);
70 }
71
72 return ti ? &ti->tt : NULL;
73}
74
75void dm_put_target_type(struct target_type *t)
76{
77 struct tt_internal *ti = (struct tt_internal *) t;
78
79 down_read(&_lock);
80 if (--ti->use == 0)
81 module_put(ti->tt.module);
82
Eric Sesterhenn543cb2a2006-04-01 01:08:12 +020083 BUG_ON(ti->use < 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 up_read(&_lock);
85
86 return;
87}
88
89static struct tt_internal *alloc_target(struct target_type *t)
90{
Dmitry Monakhov094262d2007-10-19 22:38:51 +010091 struct tt_internal *ti = kzalloc(sizeof(*ti), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -070092
Dmitry Monakhov094262d2007-10-19 22:38:51 +010093 if (ti)
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 ti->tt = *t;
Linus Torvalds1da177e2005-04-16 15:20:36 -070095
96 return ti;
97}
98
99
100int dm_target_iterate(void (*iter_func)(struct target_type *tt,
101 void *param), void *param)
102{
103 struct tt_internal *ti;
104
105 down_read(&_lock);
106 list_for_each_entry (ti, &_targets, list)
107 iter_func(&ti->tt, param);
108 up_read(&_lock);
109
110 return 0;
111}
112
113int dm_register_target(struct target_type *t)
114{
115 int rv = 0;
116 struct tt_internal *ti = alloc_target(t);
117
118 if (!ti)
119 return -ENOMEM;
120
121 down_write(&_lock);
122 if (__find_target_type(t->name))
123 rv = -EEXIST;
124 else
125 list_add(&ti->list, &_targets);
126
127 up_write(&_lock);
128 if (rv)
129 kfree(ti);
130 return rv;
131}
132
133int dm_unregister_target(struct target_type *t)
134{
135 struct tt_internal *ti;
136
137 down_write(&_lock);
138 if (!(ti = __find_target_type(t->name))) {
139 up_write(&_lock);
140 return -EINVAL;
141 }
142
143 if (ti->use) {
144 up_write(&_lock);
145 return -ETXTBSY;
146 }
147
148 list_del(&ti->list);
149 kfree(ti);
150
151 up_write(&_lock);
152 return 0;
153}
154
155/*
156 * io-err: always fails an io, useful for bringing
157 * up LVs that have holes in them.
158 */
159static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
160{
161 return 0;
162}
163
164static void io_err_dtr(struct dm_target *ti)
165{
166 /* empty */
167}
168
169static int io_err_map(struct dm_target *ti, struct bio *bio,
170 union map_info *map_context)
171{
172 return -EIO;
173}
174
175static struct target_type error_target = {
176 .name = "error",
177 .version = {1, 0, 1},
178 .ctr = io_err_ctr,
179 .dtr = io_err_dtr,
180 .map = io_err_map,
181};
182
183int __init dm_target_init(void)
184{
185 return dm_register_target(&error_target);
186}
187
188void dm_target_exit(void)
189{
190 if (dm_unregister_target(&error_target))
191 DMWARN("error target unregistration failed");
192}
193
194EXPORT_SYMBOL(dm_register_target);
195EXPORT_SYMBOL(dm_unregister_target);