1 /*
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
15 struct tt_internal {
16 struct target_type tt;
17
18 struct list_head list;
19 long use;
20 };
21
22 static LIST_HEAD(_targets);
23 static DECLARE_RWSEM(_lock);
24
25 #define DM_MOD_NAME_SIZE 32
26
27 static inline struct tt_internal *__find_target_type(const char *name)
28 {
29 struct tt_internal *ti;
30
31 list_for_each_entry (ti, &_targets, list)
32 if (!strcmp(name, ti->tt.name))
33 return ti;
34
35 return NULL;
36 }
37
38 static struct tt_internal *get_target_type(const char *name)
39 {
40 struct tt_internal *ti;
41
42 down_read(&_lock);
43
44 ti = __find_target_type(name);
45 if (ti) {
46 if ((ti->use == 0) && !try_module_get(ti->tt.module))
47 ti = NULL;
48 else
49 ti->use++;
50 }
51
52 up_read(&_lock);
53 return ti;
54 }
55
56 static void load_module(const char *name)
57 {
58 request_module("dm-%s", name);
59 }
60
61 struct target_type *dm_get_target_type(const char *name)
62 {
63 struct tt_internal *ti = get_target_type(name);
64
65 if (!ti) {
66 load_module(name);
67 ti = get_target_type(name);
68 }
69
70 return ti ? &ti->tt : NULL;
71 }
72
73 void dm_put_target_type(struct target_type *t)
74 {
75 struct tt_internal *ti = (struct tt_internal *) t;
76
77 down_read(&_lock);
78 if (--ti->use == 0)
79 module_put(ti->tt.module);
80
81 BUG_ON(ti->use < 0);
82 up_read(&_lock);
83
84 return;
85 }
86
87 static struct tt_internal *alloc_target(struct target_type *t)
88 {
89 struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
90
91 if (ti) {
92 memset(ti, 0, sizeof(*ti));
93 ti->tt = *t;
94 }
95
96 return ti;
97 }
98
99
100 int 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
113 int 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
133 int 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 */
159 static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
160 {
161 return 0;
162 }
163
164 static void io_err_dtr(struct dm_target *ti)
165 {
166 /* empty */
167 }
168
169 static int io_err_map(struct dm_target *ti, struct bio *bio,
170 union map_info *map_context)
171 {
172 return -EIO;
173 }
174
175 static 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
183 int __init dm_target_init(void)
184 {
185 return dm_register_target(&error_target);
186 }
187
188 void dm_target_exit(void)
189 {
190 if (dm_unregister_target(&error_target))
191 DMWARN("error target unregistration failed");
192 }
193
194 EXPORT_SYMBOL(dm_register_target);
195 EXPORT_SYMBOL(dm_unregister_target);
196
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