1/*
2 * Copyright (C) 2001 Sistina Software (UK) Limited
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm-core.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
16static LIST_HEAD(_targets);
17static DECLARE_RWSEM(_lock);
18
19static inline struct target_type *__find_target_type(const char *name)
20{
21 struct target_type *tt;
22
23 list_for_each_entry(tt, &_targets, list)
24 if (!strcmp(name, tt->name))
25 return tt;
26
27 return NULL;
28}
29
30static struct target_type *get_target_type(const char *name)
31{
32 struct target_type *tt;
33
34 down_read(&_lock);
35
36 tt = __find_target_type(name);
37 if (tt && !try_module_get(tt->module))
38 tt = NULL;
39
40 up_read(&_lock);
41 return tt;
42}
43
44static void load_module(const char *name)
45{
46 request_module("dm-%s", name);
47}
48
49struct target_type *dm_get_target_type(const char *name)
50{
51 struct target_type *tt = get_target_type(name);
52
53 if (!tt) {
54 load_module(name);
55 tt = get_target_type(name);
56 }
57
58 return tt;
59}
60
61void dm_put_target_type(struct target_type *tt)
62{
63 down_read(&_lock);
64 module_put(tt->module);
65 up_read(&_lock);
66}
67
68int dm_target_iterate(void (*iter_func)(struct target_type *tt,
69 void *param), void *param)
70{
71 struct target_type *tt;
72
73 down_read(&_lock);
74 list_for_each_entry(tt, &_targets, list)
75 iter_func(tt, param);
76 up_read(&_lock);
77
78 return 0;
79}
80
81int dm_register_target(struct target_type *tt)
82{
83 int rv = 0;
84
85 down_write(&_lock);
86 if (__find_target_type(tt->name))
87 rv = -EEXIST;
88 else
89 list_add(&tt->list, &_targets);
90
91 up_write(&_lock);
92 return rv;
93}
94
95void dm_unregister_target(struct target_type *tt)
96{
97 down_write(&_lock);
98 if (!__find_target_type(tt->name)) {
99 DMCRIT("Unregistering unrecognised target: %s", tt->name);
100 BUG();
101 }
102
103 list_del(&tt->list);
104
105 up_write(&_lock);
106}
107
108/*
109 * io-err: always fails an io, useful for bringing
110 * up LVs that have holes in them.
111 */
112static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
113{
114 /*
115 * Return error for discards instead of -EOPNOTSUPP
116 */
117 tt->num_discard_bios = 1;
118
119 return 0;
120}
121
122static void io_err_dtr(struct dm_target *tt)
123{
124 /* empty */
125}
126
127static int io_err_map(struct dm_target *tt, struct bio *bio)
128{
129 return DM_MAPIO_KILL;
130}
131
132static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
133 union map_info *map_context,
134 struct request **clone)
135{
136 return DM_MAPIO_KILL;
137}
138
139static void io_err_release_clone_rq(struct request *clone)
140{
141}
142
143static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
144 long nr_pages, void **kaddr, pfn_t *pfn)
145{
146 return -EIO;
147}
148
149static struct target_type error_target = {
150 .name = "error",
151 .version = {1, 5, 0},
152 .features = DM_TARGET_WILDCARD,
153 .ctr = io_err_ctr,
154 .dtr = io_err_dtr,
155 .map = io_err_map,
156 .clone_and_map_rq = io_err_clone_and_map_rq,
157 .release_clone_rq = io_err_release_clone_rq,
158 .direct_access = io_err_dax_direct_access,
159};
160
161int __init dm_target_init(void)
162{
163 return dm_register_target(&error_target);
164}
165
166void dm_target_exit(void)
167{
168 dm_unregister_target(&error_target);
169}
170
171EXPORT_SYMBOL(dm_register_target);
172EXPORT_SYMBOL(dm_unregister_target);
173