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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 | ||
14 | #define DM_MSG_PREFIX "target" | |
15 | ||
16 | static LIST_HEAD(_targets); | |
17 | static DECLARE_RWSEM(_lock); | |
18 | ||
19 | #define DM_MOD_NAME_SIZE 32 | |
20 | ||
21 | static inline struct target_type *__find_target_type(const char *name) | |
22 | { | |
23 | struct target_type *tt; | |
24 | ||
25 | list_for_each_entry(tt, &_targets, list) | |
26 | if (!strcmp(name, tt->name)) | |
27 | return tt; | |
28 | ||
29 | return NULL; | |
30 | } | |
31 | ||
32 | static struct target_type *get_target_type(const char *name) | |
33 | { | |
34 | struct target_type *tt; | |
35 | ||
36 | down_read(&_lock); | |
37 | ||
38 | tt = __find_target_type(name); | |
39 | if (tt && !try_module_get(tt->module)) | |
40 | tt = NULL; | |
41 | ||
42 | up_read(&_lock); | |
43 | return tt; | |
44 | } | |
45 | ||
46 | static void load_module(const char *name) | |
47 | { | |
48 | request_module("dm-%s", name); | |
49 | } | |
50 | ||
51 | struct target_type *dm_get_target_type(const char *name) | |
52 | { | |
53 | struct target_type *tt = get_target_type(name); | |
54 | ||
55 | if (!tt) { | |
56 | load_module(name); | |
57 | tt = get_target_type(name); | |
58 | } | |
59 | ||
60 | return tt; | |
61 | } | |
62 | ||
63 | void dm_put_target_type(struct target_type *tt) | |
64 | { | |
65 | down_read(&_lock); | |
66 | module_put(tt->module); | |
67 | up_read(&_lock); | |
68 | } | |
69 | ||
70 | int dm_target_iterate(void (*iter_func)(struct target_type *tt, | |
71 | void *param), void *param) | |
72 | { | |
73 | struct target_type *tt; | |
74 | ||
75 | down_read(&_lock); | |
76 | list_for_each_entry(tt, &_targets, list) | |
77 | iter_func(tt, param); | |
78 | up_read(&_lock); | |
79 | ||
80 | return 0; | |
81 | } | |
82 | ||
83 | int dm_register_target(struct target_type *tt) | |
84 | { | |
85 | int rv = 0; | |
86 | ||
87 | down_write(&_lock); | |
88 | if (__find_target_type(tt->name)) | |
89 | rv = -EEXIST; | |
90 | else | |
91 | list_add(&tt->list, &_targets); | |
92 | ||
93 | up_write(&_lock); | |
94 | return rv; | |
95 | } | |
96 | ||
97 | void dm_unregister_target(struct target_type *tt) | |
98 | { | |
99 | down_write(&_lock); | |
100 | if (!__find_target_type(tt->name)) { | |
101 | DMCRIT("Unregistering unrecognised target: %s", tt->name); | |
102 | BUG(); | |
103 | } | |
104 | ||
105 | list_del(&tt->list); | |
106 | ||
107 | up_write(&_lock); | |
108 | } | |
109 | ||
110 | /* | |
111 | * io-err: always fails an io, useful for bringing | |
112 | * up LVs that have holes in them. | |
113 | */ | |
114 | static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args) | |
115 | { | |
116 | /* | |
117 | * Return error for discards instead of -EOPNOTSUPP | |
118 | */ | |
119 | tt->num_discard_bios = 1; | |
120 | ||
121 | return 0; | |
122 | } | |
123 | ||
124 | static void io_err_dtr(struct dm_target *tt) | |
125 | { | |
126 | /* empty */ | |
127 | } | |
128 | ||
129 | static int io_err_map(struct dm_target *tt, struct bio *bio) | |
130 | { | |
131 | return -EIO; | |
132 | } | |
133 | ||
134 | static int io_err_map_rq(struct dm_target *ti, struct request *clone, | |
135 | union map_info *map_context) | |
136 | { | |
137 | return -EIO; | |
138 | } | |
139 | ||
140 | static struct target_type error_target = { | |
141 | .name = "error", | |
142 | .version = {1, 2, 0}, | |
143 | .ctr = io_err_ctr, | |
144 | .dtr = io_err_dtr, | |
145 | .map = io_err_map, | |
146 | .map_rq = io_err_map_rq, | |
147 | }; | |
148 | ||
149 | int __init dm_target_init(void) | |
150 | { | |
151 | return dm_register_target(&error_target); | |
152 | } | |
153 | ||
154 | void dm_target_exit(void) | |
155 | { | |
156 | dm_unregister_target(&error_target); | |
157 | } | |
158 | ||
159 | EXPORT_SYMBOL(dm_register_target); | |
160 | EXPORT_SYMBOL(dm_unregister_target); |