MIPS: Loongson: Remove ad-hoc cmdline default
[linux-2.6.git] / drivers / md / dm-path-selector.c
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 <linux/device-mapper.h>
13
14 #include "dm-path-selector.h"
15
16 #include <linux/slab.h>
17
18 struct ps_internal {
19         struct path_selector_type pst;
20         struct list_head list;
21 };
22
23 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
24
25 static LIST_HEAD(_path_selectors);
26 static DECLARE_RWSEM(_ps_lock);
27
28 static struct ps_internal *__find_path_selector_type(const char *name)
29 {
30         struct ps_internal *psi;
31
32         list_for_each_entry(psi, &_path_selectors, list) {
33                 if (!strcmp(name, psi->pst.name))
34                         return psi;
35         }
36
37         return NULL;
38 }
39
40 static struct ps_internal *get_path_selector(const char *name)
41 {
42         struct ps_internal *psi;
43
44         down_read(&_ps_lock);
45         psi = __find_path_selector_type(name);
46         if (psi && !try_module_get(psi->pst.module))
47                 psi = NULL;
48         up_read(&_ps_lock);
49
50         return psi;
51 }
52
53 struct path_selector_type *dm_get_path_selector(const char *name)
54 {
55         struct ps_internal *psi;
56
57         if (!name)
58                 return NULL;
59
60         psi = get_path_selector(name);
61         if (!psi) {
62                 request_module("dm-%s", name);
63                 psi = get_path_selector(name);
64         }
65
66         return psi ? &psi->pst : NULL;
67 }
68
69 void dm_put_path_selector(struct path_selector_type *pst)
70 {
71         struct ps_internal *psi;
72
73         if (!pst)
74                 return;
75
76         down_read(&_ps_lock);
77         psi = __find_path_selector_type(pst->name);
78         if (!psi)
79                 goto out;
80
81         module_put(psi->pst.module);
82 out:
83         up_read(&_ps_lock);
84 }
85
86 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
87 {
88         struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
89
90         if (psi)
91                 psi->pst = *pst;
92
93         return psi;
94 }
95
96 int dm_register_path_selector(struct path_selector_type *pst)
97 {
98         int r = 0;
99         struct ps_internal *psi = _alloc_path_selector(pst);
100
101         if (!psi)
102                 return -ENOMEM;
103
104         down_write(&_ps_lock);
105
106         if (__find_path_selector_type(pst->name)) {
107                 kfree(psi);
108                 r = -EEXIST;
109         } else
110                 list_add(&psi->list, &_path_selectors);
111
112         up_write(&_ps_lock);
113
114         return r;
115 }
116
117 int dm_unregister_path_selector(struct path_selector_type *pst)
118 {
119         struct ps_internal *psi;
120
121         down_write(&_ps_lock);
122
123         psi = __find_path_selector_type(pst->name);
124         if (!psi) {
125                 up_write(&_ps_lock);
126                 return -EINVAL;
127         }
128
129         list_del(&psi->list);
130
131         up_write(&_ps_lock);
132
133         kfree(psi);
134
135         return 0;
136 }
137
138 EXPORT_SYMBOL_GPL(dm_register_path_selector);
139 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);