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 #include <linux/dax.h>
14
15 #define DM_MSG_PREFIX "target"
16
17 static LIST_HEAD(_targets);
18 static DECLARE_RWSEM(_lock);
19
__find_target_type(const char * name)20 static inline struct target_type *__find_target_type(const char *name)
21 {
22 struct target_type *tt;
23
24 list_for_each_entry(tt, &_targets, list)
25 if (!strcmp(name, tt->name))
26 return tt;
27
28 return NULL;
29 }
30
get_target_type(const char * name)31 static struct target_type *get_target_type(const char *name)
32 {
33 struct target_type *tt;
34
35 down_read(&_lock);
36
37 tt = __find_target_type(name);
38 if (tt && !try_module_get(tt->module))
39 tt = NULL;
40
41 up_read(&_lock);
42 return tt;
43 }
44
load_module(const char * name)45 static void load_module(const char *name)
46 {
47 request_module("dm-%s", name);
48 }
49
dm_get_target_type(const char * name)50 struct target_type *dm_get_target_type(const char *name)
51 {
52 struct target_type *tt = get_target_type(name);
53
54 if (!tt) {
55 load_module(name);
56 tt = get_target_type(name);
57 }
58
59 return tt;
60 }
61
dm_put_target_type(struct target_type * tt)62 void dm_put_target_type(struct target_type *tt)
63 {
64 down_read(&_lock);
65 module_put(tt->module);
66 up_read(&_lock);
67 }
68
dm_target_iterate(void (* iter_func)(struct target_type * tt,void * param),void * param)69 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
70 void *param), void *param)
71 {
72 struct target_type *tt;
73
74 down_read(&_lock);
75 list_for_each_entry(tt, &_targets, list)
76 iter_func(tt, param);
77 up_read(&_lock);
78
79 return 0;
80 }
81
dm_register_target(struct target_type * tt)82 int dm_register_target(struct target_type *tt)
83 {
84 int rv = 0;
85
86 down_write(&_lock);
87 if (__find_target_type(tt->name))
88 rv = -EEXIST;
89 else
90 list_add(&tt->list, &_targets);
91
92 up_write(&_lock);
93 return rv;
94 }
95
dm_unregister_target(struct target_type * tt)96 void dm_unregister_target(struct target_type *tt)
97 {
98 down_write(&_lock);
99 if (!__find_target_type(tt->name)) {
100 DMCRIT("Unregistering unrecognised target: %s", tt->name);
101 BUG();
102 }
103
104 list_del(&tt->list);
105
106 up_write(&_lock);
107 }
108
109 /*
110 * io-err: always fails an io, useful for bringing
111 * up LVs that have holes in them.
112 */
io_err_ctr(struct dm_target * tt,unsigned int argc,char ** args)113 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
114 {
115 /*
116 * Return error for discards instead of -EOPNOTSUPP
117 */
118 tt->num_discard_bios = 1;
119
120 return 0;
121 }
122
io_err_dtr(struct dm_target * tt)123 static void io_err_dtr(struct dm_target *tt)
124 {
125 /* empty */
126 }
127
io_err_map(struct dm_target * tt,struct bio * bio)128 static int io_err_map(struct dm_target *tt, struct bio *bio)
129 {
130 return DM_MAPIO_KILL;
131 }
132
io_err_clone_and_map_rq(struct dm_target * ti,struct request * rq,union map_info * map_context,struct request ** clone)133 static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
134 union map_info *map_context,
135 struct request **clone)
136 {
137 return DM_MAPIO_KILL;
138 }
139
io_err_release_clone_rq(struct request * clone,union map_info * map_context)140 static void io_err_release_clone_rq(struct request *clone,
141 union map_info *map_context)
142 {
143 }
144
io_err_dax_direct_access(struct dm_target * ti,pgoff_t pgoff,long nr_pages,enum dax_access_mode mode,void ** kaddr,pfn_t * pfn)145 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
146 long nr_pages, enum dax_access_mode mode, void **kaddr,
147 pfn_t *pfn)
148 {
149 return -EIO;
150 }
151
152 static struct target_type error_target = {
153 .name = "error",
154 .version = {1, 5, 0},
155 .features = DM_TARGET_WILDCARD,
156 .ctr = io_err_ctr,
157 .dtr = io_err_dtr,
158 .map = io_err_map,
159 .clone_and_map_rq = io_err_clone_and_map_rq,
160 .release_clone_rq = io_err_release_clone_rq,
161 .direct_access = io_err_dax_direct_access,
162 };
163
dm_target_init(void)164 int __init dm_target_init(void)
165 {
166 return dm_register_target(&error_target);
167 }
168
dm_target_exit(void)169 void dm_target_exit(void)
170 {
171 dm_unregister_target(&error_target);
172 }
173
174 EXPORT_SYMBOL(dm_register_target);
175 EXPORT_SYMBOL(dm_unregister_target);
176