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
__find_target_type(const char * name)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
get_target_type(const char * name)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
load_module(const char * name)46 static void load_module(const char *name)
47 {
48 request_module("dm-%s", name);
49 }
50
dm_get_target_type(const char * name)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
dm_put_target_type(struct target_type * tt)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
dm_target_iterate(void (* iter_func)(struct target_type * tt,void * param),void * param)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
dm_register_target(struct target_type * tt)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
dm_unregister_target(struct target_type * tt)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 */
io_err_ctr(struct dm_target * tt,unsigned int argc,char ** args)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_requests = 1;
120
121 return 0;
122 }
123
io_err_dtr(struct dm_target * tt)124 static void io_err_dtr(struct dm_target *tt)
125 {
126 /* empty */
127 }
128
io_err_map(struct dm_target * tt,struct bio * bio,union map_info * map_context)129 static int io_err_map(struct dm_target *tt, struct bio *bio,
130 union map_info *map_context)
131 {
132 return -EIO;
133 }
134
135 static struct target_type error_target = {
136 .name = "error",
137 .version = {1, 0, 1},
138 .ctr = io_err_ctr,
139 .dtr = io_err_dtr,
140 .map = io_err_map,
141 };
142
dm_target_init(void)143 int __init dm_target_init(void)
144 {
145 return dm_register_target(&error_target);
146 }
147
dm_target_exit(void)148 void dm_target_exit(void)
149 {
150 dm_unregister_target(&error_target);
151 }
152
153 EXPORT_SYMBOL(dm_register_target);
154 EXPORT_SYMBOL(dm_unregister_target);
155