Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / md / dm-path-selector.c
blobf10a0c89b3f4e542b3901790504a212d612741ef
1 /*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
5 * Module Author: Heinz Mauelshagen
7 * This file is released under the GPL.
9 * Path selector registration.
12 #include "dm.h"
13 #include "dm-path-selector.h"
15 #include <linux/slab.h>
17 struct ps_internal {
18 struct path_selector_type pst;
20 struct list_head list;
21 long use;
24 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
26 static LIST_HEAD(_path_selectors);
27 static DECLARE_RWSEM(_ps_lock);
29 static struct ps_internal *__find_path_selector_type(const char *name)
31 struct ps_internal *psi;
33 list_for_each_entry(psi, &_path_selectors, list) {
34 if (!strcmp(name, psi->pst.name))
35 return psi;
38 return NULL;
41 static struct ps_internal *get_path_selector(const char *name)
43 struct ps_internal *psi;
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++;
53 up_read(&_ps_lock);
55 return psi;
58 struct path_selector_type *dm_get_path_selector(const char *name)
60 struct ps_internal *psi;
62 if (!name)
63 return NULL;
65 psi = get_path_selector(name);
66 if (!psi) {
67 request_module("dm-%s", name);
68 psi = get_path_selector(name);
71 return psi ? &psi->pst : NULL;
74 void dm_put_path_selector(struct path_selector_type *pst)
76 struct ps_internal *psi;
78 if (!pst)
79 return;
81 down_read(&_ps_lock);
82 psi = __find_path_selector_type(pst->name);
83 if (!psi)
84 goto out;
86 if (--psi->use == 0)
87 module_put(psi->pst.module);
89 BUG_ON(psi->use < 0);
91 out:
92 up_read(&_ps_lock);
95 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
97 struct ps_internal *psi = kmalloc(sizeof(*psi), GFP_KERNEL);
99 if (psi) {
100 memset(psi, 0, sizeof(*psi));
101 psi->pst = *pst;
104 return psi;
107 int dm_register_path_selector(struct path_selector_type *pst)
109 int r = 0;
110 struct ps_internal *psi = _alloc_path_selector(pst);
112 if (!psi)
113 return -ENOMEM;
115 down_write(&_ps_lock);
117 if (__find_path_selector_type(pst->name)) {
118 kfree(psi);
119 r = -EEXIST;
120 } else
121 list_add(&psi->list, &_path_selectors);
123 up_write(&_ps_lock);
125 return r;
128 int dm_unregister_path_selector(struct path_selector_type *pst)
130 struct ps_internal *psi;
132 down_write(&_ps_lock);
134 psi = __find_path_selector_type(pst->name);
135 if (!psi) {
136 up_write(&_ps_lock);
137 return -EINVAL;
140 if (psi->use) {
141 up_write(&_ps_lock);
142 return -ETXTBSY;
145 list_del(&psi->list);
147 up_write(&_ps_lock);
149 kfree(psi);
151 return 0;
154 EXPORT_SYMBOL_GPL(dm_register_path_selector);
155 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);