Root/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#include <linux/module.h>
14
15#include "dm-path-selector.h"
16
17#include <linux/slab.h>
18
19struct ps_internal {
20    struct path_selector_type pst;
21    struct list_head list;
22};
23
24#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
25
26static LIST_HEAD(_path_selectors);
27static DECLARE_RWSEM(_ps_lock);
28
29static 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
41static 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 && !try_module_get(psi->pst.module))
48        psi = NULL;
49    up_read(&_ps_lock);
50
51    return psi;
52}
53
54struct path_selector_type *dm_get_path_selector(const char *name)
55{
56    struct ps_internal *psi;
57
58    if (!name)
59        return NULL;
60
61    psi = get_path_selector(name);
62    if (!psi) {
63        request_module("dm-%s", name);
64        psi = get_path_selector(name);
65    }
66
67    return psi ? &psi->pst : NULL;
68}
69
70void dm_put_path_selector(struct path_selector_type *pst)
71{
72    struct ps_internal *psi;
73
74    if (!pst)
75        return;
76
77    down_read(&_ps_lock);
78    psi = __find_path_selector_type(pst->name);
79    if (!psi)
80        goto out;
81
82    module_put(psi->pst.module);
83out:
84    up_read(&_ps_lock);
85}
86
87static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
88{
89    struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
90
91    if (psi)
92        psi->pst = *pst;
93
94    return psi;
95}
96
97int dm_register_path_selector(struct path_selector_type *pst)
98{
99    int r = 0;
100    struct ps_internal *psi = _alloc_path_selector(pst);
101
102    if (!psi)
103        return -ENOMEM;
104
105    down_write(&_ps_lock);
106
107    if (__find_path_selector_type(pst->name)) {
108        kfree(psi);
109        r = -EEXIST;
110    } else
111        list_add(&psi->list, &_path_selectors);
112
113    up_write(&_ps_lock);
114
115    return r;
116}
117
118int dm_unregister_path_selector(struct path_selector_type *pst)
119{
120    struct ps_internal *psi;
121
122    down_write(&_ps_lock);
123
124    psi = __find_path_selector_type(pst->name);
125    if (!psi) {
126        up_write(&_ps_lock);
127        return -EINVAL;
128    }
129
130    list_del(&psi->list);
131
132    up_write(&_ps_lock);
133
134    kfree(psi);
135
136    return 0;
137}
138
139EXPORT_SYMBOL_GPL(dm_register_path_selector);
140EXPORT_SYMBOL_GPL(dm_unregister_path_selector);
141

Archive Download this file



interactive