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
16static LIST_HEAD(_targets);
17static DECLARE_RWSEM(_lock);
18
19#define DM_MOD_NAME_SIZE 32
20
21static 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
32static 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
46static void load_module(const char *name)
47{
48	request_module("dm-%s", name);
49}
50
51struct 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
63void dm_put_target_type(struct target_type *tt)
64{
65	down_read(&_lock);
66	module_put(tt->module);
67	up_read(&_lock);
68}
69
70int 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
83int 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
97void 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 */
114static 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
124static void io_err_dtr(struct dm_target *tt)
125{
126	/* empty */
127}
128
129static int io_err_map(struct dm_target *tt, struct bio *bio)
130{
131	return -EIO;
132}
133
134static int io_err_map_rq(struct dm_target *ti, struct request *clone,
135			 union map_info *map_context)
136{
137	return -EIO;
138}
139
140static 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
149int __init dm_target_init(void)
150{
151	return dm_register_target(&error_target);
152}
153
154void dm_target_exit(void)
155{
156	dm_unregister_target(&error_target);
157}
158
159EXPORT_SYMBOL(dm_register_target);
160EXPORT_SYMBOL(dm_unregister_target);
161