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1da177e4 LT |
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 | ||
5e198d94 | 29 | static struct ps_internal *__find_path_selector_type(const char *name) |
1da177e4 LT |
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 | if (psi->use < 0) | |
90 | BUG(); | |
91 | ||
92 | out: | |
93 | up_read(&_ps_lock); | |
94 | } | |
95 | ||
96 | static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst) | |
97 | { | |
98 | struct ps_internal *psi = kmalloc(sizeof(*psi), GFP_KERNEL); | |
99 | ||
100 | if (psi) { | |
101 | memset(psi, 0, sizeof(*psi)); | |
102 | psi->pst = *pst; | |
103 | } | |
104 | ||
105 | return psi; | |
106 | } | |
107 | ||
108 | int dm_register_path_selector(struct path_selector_type *pst) | |
109 | { | |
110 | int r = 0; | |
111 | struct ps_internal *psi = _alloc_path_selector(pst); | |
112 | ||
113 | if (!psi) | |
114 | return -ENOMEM; | |
115 | ||
116 | down_write(&_ps_lock); | |
117 | ||
118 | if (__find_path_selector_type(pst->name)) { | |
119 | kfree(psi); | |
120 | r = -EEXIST; | |
121 | } else | |
122 | list_add(&psi->list, &_path_selectors); | |
123 | ||
124 | up_write(&_ps_lock); | |
125 | ||
126 | return r; | |
127 | } | |
128 | ||
129 | int dm_unregister_path_selector(struct path_selector_type *pst) | |
130 | { | |
131 | struct ps_internal *psi; | |
132 | ||
133 | down_write(&_ps_lock); | |
134 | ||
135 | psi = __find_path_selector_type(pst->name); | |
136 | if (!psi) { | |
137 | up_write(&_ps_lock); | |
138 | return -EINVAL; | |
139 | } | |
140 | ||
141 | if (psi->use) { | |
142 | up_write(&_ps_lock); | |
143 | return -ETXTBSY; | |
144 | } | |
145 | ||
146 | list_del(&psi->list); | |
147 | ||
148 | up_write(&_ps_lock); | |
149 | ||
150 | kfree(psi); | |
151 | ||
152 | return 0; | |
153 | } | |
154 | ||
155 | EXPORT_SYMBOL_GPL(dm_register_path_selector); | |
156 | EXPORT_SYMBOL_GPL(dm_unregister_path_selector); |