1 /*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
4 *
5 * Module Author: Heinz Mauelshagen
6 *
7 * This file is released under the GPL.
8 *
9 * Path selector registration.
10 */
11
12 #include "dm.h"
13 #include "dm-path-selector.h"
14
15 #include <linux/slab.h>
16
17 struct ps_internal {
18 struct path_selector_type pst;
19
20 struct list_head list;
21 long use;
22 };
23
24 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
25
26 static LIST_HEAD(_path_selectors);
27 static DECLARE_RWSEM(_ps_lock);
28
29 static struct ps_internal *__find_path_selector_type(const char *name)
30 {
31 struct ps_internal *psi;
32
33 list_for_each_entry(psi, &_path_selectors, list) {
34 if (!strcmp(name, psi->pst.name))
35 return psi;
36 }
37
38 return NULL;
39 }
40
41 static struct ps_internal *get_path_selector(const char *name)
42 {
43 struct ps_internal *psi;
44
45 down_read(&_ps_lock);
46 psi = __find_path_selector_type(name);
47 if (psi) {
48 if ((psi->use == 0) && !try_module_get(psi->pst.module))
49 psi = NULL;
50 else
51 psi->use++;
52 }
53 up_read(&_ps_lock);
54
55 return psi;
56 }
57
58 struct path_selector_type *dm_get_path_selector(const char *name)
59 {
60 struct ps_internal *psi;
61
62 if (!name)
63 return NULL;
64
65 psi = get_path_selector(name);
66 if (!psi) {
67 request_module("dm-%s", name);
68 psi = get_path_selector(name);
69 }
70
71 return psi ? &psi->pst : NULL;
72 }
73
74 void dm_put_path_selector(struct path_selector_type *pst)
75 {
76 struct ps_internal *psi;
77
78 if (!pst)
79 return;
80
81 down_read(&_ps_lock);
82 psi = __find_path_selector_type(pst->name);
83 if (!psi)
84 goto out;
85
86 if (--psi->use == 0)
87 module_put(psi->pst.module);
88
89 BUG_ON(psi->use < 0);
90
91 out:
92 up_read(&_ps_lock);
93 }
94
95 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
96 {
97 struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
98
99 if (psi)
100 psi->pst = *pst;
101
102 return psi;
103 }
104
105 int dm_register_path_selector(struct path_selector_type *pst)
106 {
107 int r = 0;
108 struct ps_internal *psi = _alloc_path_selector(pst);
109
110 if (!psi)
111 return -ENOMEM;
112
113 down_write(&_ps_lock);
114
115 if (__find_path_selector_type(pst->name)) {
116 kfree(psi);
117 r = -EEXIST;
118 } else
119 list_add(&psi->list, &_path_selectors);
120
121 up_write(&_ps_lock);
122
123 return r;
124 }
125
126 int dm_unregister_path_selector(struct path_selector_type *pst)
127 {
128 struct ps_internal *psi;
129
130 down_write(&_ps_lock);
131
132 psi = __find_path_selector_type(pst->name);
133 if (!psi) {
134 up_write(&_ps_lock);
135 return -EINVAL;
136 }
137
138 if (psi->use) {
139 up_write(&_ps_lock);
140 return -ETXTBSY;
141 }
142
143 list_del(&psi->list);
144
145 up_write(&_ps_lock);
146
147 kfree(psi);
148
149 return 0;
150 }
151
152 EXPORT_SYMBOL_GPL(dm_register_path_selector);
153 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);
154
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