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
16 static LIST_HEAD(_targets);
17 static DECLARE_RWSEM(_lock);
18
__find_target_type(const char * name)19 static 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
get_target_type(const char * name)30 static 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
load_module(const char * name)44 static void load_module(const char *name)
45 {
46 request_module("dm-%s", name);
47 }
48
dm_get_target_type(const char * name)49 struct 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
dm_put_target_type(struct target_type * tt)61 void dm_put_target_type(struct target_type *tt)
62 {
63 down_read(&_lock);
64 module_put(tt->module);
65 up_read(&_lock);
66 }
67
dm_target_iterate(void (* iter_func)(struct target_type * tt,void * param),void * param)68 int 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
dm_register_target(struct target_type * tt)81 int 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
dm_unregister_target(struct target_type * tt)95 void 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 */
io_err_ctr(struct dm_target * tt,unsigned int argc,char ** args)112 static 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
io_err_dtr(struct dm_target * tt)122 static void io_err_dtr(struct dm_target *tt)
123 {
124 /* empty */
125 }
126
io_err_map(struct dm_target * tt,struct bio * bio)127 static int io_err_map(struct dm_target *tt, struct bio *bio)
128 {
129 return DM_MAPIO_KILL;
130 }
131
io_err_clone_and_map_rq(struct dm_target * ti,struct request * rq,union map_info * map_context,struct request ** clone)132 static 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
io_err_release_clone_rq(struct request * clone,union map_info * map_context)139 static void io_err_release_clone_rq(struct request *clone,
140 union map_info *map_context)
141 {
142 }
143
io_err_dax_direct_access(struct dm_target * ti,pgoff_t pgoff,long nr_pages,void ** kaddr,pfn_t * pfn)144 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
145 long nr_pages, void **kaddr, pfn_t *pfn)
146 {
147 return -EIO;
148 }
149
150 static struct target_type error_target = {
151 .name = "error",
152 .version = {1, 5, 0},
153 .features = DM_TARGET_WILDCARD,
154 .ctr = io_err_ctr,
155 .dtr = io_err_dtr,
156 .map = io_err_map,
157 .clone_and_map_rq = io_err_clone_and_map_rq,
158 .release_clone_rq = io_err_release_clone_rq,
159 .direct_access = io_err_dax_direct_access,
160 };
161
dm_target_init(void)162 int __init dm_target_init(void)
163 {
164 return dm_register_target(&error_target);
165 }
166
dm_target_exit(void)167 void dm_target_exit(void)
168 {
169 dm_unregister_target(&error_target);
170 }
171
172 EXPORT_SYMBOL(dm_register_target);
173 EXPORT_SYMBOL(dm_unregister_target);
174