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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 | #define DM_MSG_PREFIX "target" |
16 | |
17 | static LIST_HEAD(_targets); |
18 | static DECLARE_RWSEM(_lock); |
19 | |
20 | #define DM_MOD_NAME_SIZE 32 |
21 | |
22 | static inline struct target_type *__find_target_type(const char *name) |
23 | { |
24 | struct target_type *tt; |
25 | |
26 | list_for_each_entry(tt, &_targets, list) |
27 | if (!strcmp(name, tt->name)) |
28 | return tt; |
29 | |
30 | return NULL; |
31 | } |
32 | |
33 | static struct target_type *get_target_type(const char *name) |
34 | { |
35 | struct target_type *tt; |
36 | |
37 | down_read(&_lock); |
38 | |
39 | tt = __find_target_type(name); |
40 | if (tt && !try_module_get(tt->module)) |
41 | tt = NULL; |
42 | |
43 | up_read(&_lock); |
44 | return tt; |
45 | } |
46 | |
47 | static void load_module(const char *name) |
48 | { |
49 | request_module("dm-%s", name); |
50 | } |
51 | |
52 | struct target_type *dm_get_target_type(const char *name) |
53 | { |
54 | struct target_type *tt = get_target_type(name); |
55 | |
56 | if (!tt) { |
57 | load_module(name); |
58 | tt = get_target_type(name); |
59 | } |
60 | |
61 | return tt; |
62 | } |
63 | |
64 | void dm_put_target_type(struct target_type *tt) |
65 | { |
66 | down_read(&_lock); |
67 | module_put(tt->module); |
68 | up_read(&_lock); |
69 | } |
70 | |
71 | int dm_target_iterate(void (*iter_func)(struct target_type *tt, |
72 | void *param), void *param) |
73 | { |
74 | struct target_type *tt; |
75 | |
76 | down_read(&_lock); |
77 | list_for_each_entry(tt, &_targets, list) |
78 | iter_func(tt, param); |
79 | up_read(&_lock); |
80 | |
81 | return 0; |
82 | } |
83 | |
84 | int dm_register_target(struct target_type *tt) |
85 | { |
86 | int rv = 0; |
87 | |
88 | down_write(&_lock); |
89 | if (__find_target_type(tt->name)) |
90 | rv = -EEXIST; |
91 | else |
92 | list_add(&tt->list, &_targets); |
93 | |
94 | up_write(&_lock); |
95 | return rv; |
96 | } |
97 | |
98 | void dm_unregister_target(struct target_type *tt) |
99 | { |
100 | down_write(&_lock); |
101 | if (!__find_target_type(tt->name)) { |
102 | DMCRIT("Unregistering unrecognised target: %s", tt->name); |
103 | BUG(); |
104 | } |
105 | |
106 | list_del(&tt->list); |
107 | |
108 | up_write(&_lock); |
109 | } |
110 | |
111 | /* |
112 | * io-err: always fails an io, useful for bringing |
113 | * up LVs that have holes in them. |
114 | */ |
115 | static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args) |
116 | { |
117 | return 0; |
118 | } |
119 | |
120 | static void io_err_dtr(struct dm_target *tt) |
121 | { |
122 | /* empty */ |
123 | } |
124 | |
125 | static int io_err_map(struct dm_target *tt, struct bio *bio, |
126 | union map_info *map_context) |
127 | { |
128 | return -EIO; |
129 | } |
130 | |
131 | static struct target_type error_target = { |
132 | .name = "error", |
133 | .version = {1, 0, 1}, |
134 | .ctr = io_err_ctr, |
135 | .dtr = io_err_dtr, |
136 | .map = io_err_map, |
137 | }; |
138 | |
139 | int __init dm_target_init(void) |
140 | { |
141 | return dm_register_target(&error_target); |
142 | } |
143 | |
144 | void dm_target_exit(void) |
145 | { |
146 | dm_unregister_target(&error_target); |
147 | } |
148 | |
149 | EXPORT_SYMBOL(dm_register_target); |
150 | EXPORT_SYMBOL(dm_unregister_target); |
151 |
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