1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2001 Sistina Software (UK) Limited
4  *
5  * This file is released under the GPL.
6  */
7 
8 #include "dm-core.h"
9 
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/kmod.h>
13 #include <linux/bio.h>
14 #include <linux/dax.h>
15 
16 #define DM_MSG_PREFIX "target"
17 
18 static LIST_HEAD(_targets);
19 static DECLARE_RWSEM(_lock);
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 EXPORT_SYMBOL(dm_register_target);
97 
dm_unregister_target(struct target_type * tt)98 void dm_unregister_target(struct target_type *tt)
99 {
100 	down_write(&_lock);
101 	if (!__find_target_type(tt->name)) {
102 		DMCRIT("Unregistering unrecognised target: %s", tt->name);
103 		BUG();
104 	}
105 
106 	list_del(&tt->list);
107 
108 	up_write(&_lock);
109 }
110 EXPORT_SYMBOL(dm_unregister_target);
111 
112 /*
113  * io-err: always fails an io, useful for bringing
114  * up LVs that have holes in them.
115  */
io_err_ctr(struct dm_target * tt,unsigned int argc,char ** args)116 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
117 {
118 	/*
119 	 * Return error for discards instead of -EOPNOTSUPP
120 	 */
121 	tt->num_discard_bios = 1;
122 
123 	return 0;
124 }
125 
io_err_dtr(struct dm_target * tt)126 static void io_err_dtr(struct dm_target *tt)
127 {
128 	/* empty */
129 }
130 
io_err_map(struct dm_target * tt,struct bio * bio)131 static int io_err_map(struct dm_target *tt, struct bio *bio)
132 {
133 	return DM_MAPIO_KILL;
134 }
135 
io_err_clone_and_map_rq(struct dm_target * ti,struct request * rq,union map_info * map_context,struct request ** clone)136 static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
137 				   union map_info *map_context,
138 				   struct request **clone)
139 {
140 	return DM_MAPIO_KILL;
141 }
142 
io_err_release_clone_rq(struct request * clone,union map_info * map_context)143 static void io_err_release_clone_rq(struct request *clone,
144 				    union map_info *map_context)
145 {
146 }
147 
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)148 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
149 		long nr_pages, enum dax_access_mode mode, void **kaddr,
150 		pfn_t *pfn)
151 {
152 	return -EIO;
153 }
154 
155 static struct target_type error_target = {
156 	.name = "error",
157 	.version = {1, 5, 0},
158 	.features = DM_TARGET_WILDCARD,
159 	.ctr  = io_err_ctr,
160 	.dtr  = io_err_dtr,
161 	.map  = io_err_map,
162 	.clone_and_map_rq = io_err_clone_and_map_rq,
163 	.release_clone_rq = io_err_release_clone_rq,
164 	.direct_access = io_err_dax_direct_access,
165 };
166 
dm_target_init(void)167 int __init dm_target_init(void)
168 {
169 	return dm_register_target(&error_target);
170 }
171 
dm_target_exit(void)172 void dm_target_exit(void)
173 {
174 	dm_unregister_target(&error_target);
175 }
176