xref: /openbmc/linux/drivers/md/dm-path-selector.c (revision aa07f9d8)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2003 Sistina Software.
4  * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
5  *
6  * Module Author: Heinz Mauelshagen
7  *
8  * This file is released under the GPL.
9  *
10  * Path selector registration.
11  */
12 
13 #include <linux/device-mapper.h>
14 #include <linux/module.h>
15 
16 #include "dm-path-selector.h"
17 
18 #include <linux/slab.h>
19 
20 struct ps_internal {
21 	struct path_selector_type pst;
22 	struct list_head list;
23 };
24 
25 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
26 
27 static LIST_HEAD(_path_selectors);
28 static DECLARE_RWSEM(_ps_lock);
29 
__find_path_selector_type(const char * name)30 static struct ps_internal *__find_path_selector_type(const char *name)
31 {
32 	struct ps_internal *psi;
33 
34 	list_for_each_entry(psi, &_path_selectors, list) {
35 		if (!strcmp(name, psi->pst.name))
36 			return psi;
37 	}
38 
39 	return NULL;
40 }
41 
get_path_selector(const char * name)42 static struct ps_internal *get_path_selector(const char *name)
43 {
44 	struct ps_internal *psi;
45 
46 	down_read(&_ps_lock);
47 	psi = __find_path_selector_type(name);
48 	if (psi && !try_module_get(psi->pst.module))
49 		psi = NULL;
50 	up_read(&_ps_lock);
51 
52 	return psi;
53 }
54 
dm_get_path_selector(const char * name)55 struct path_selector_type *dm_get_path_selector(const char *name)
56 {
57 	struct ps_internal *psi;
58 
59 	if (!name)
60 		return NULL;
61 
62 	psi = get_path_selector(name);
63 	if (!psi) {
64 		request_module("dm-%s", name);
65 		psi = get_path_selector(name);
66 	}
67 
68 	return psi ? &psi->pst : NULL;
69 }
70 
dm_put_path_selector(struct path_selector_type * pst)71 void dm_put_path_selector(struct path_selector_type *pst)
72 {
73 	struct ps_internal *psi;
74 
75 	if (!pst)
76 		return;
77 
78 	down_read(&_ps_lock);
79 	psi = __find_path_selector_type(pst->name);
80 	if (!psi)
81 		goto out;
82 
83 	module_put(psi->pst.module);
84 out:
85 	up_read(&_ps_lock);
86 }
87 
_alloc_path_selector(struct path_selector_type * pst)88 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
89 {
90 	struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
91 
92 	if (psi)
93 		psi->pst = *pst;
94 
95 	return psi;
96 }
97 
dm_register_path_selector(struct path_selector_type * pst)98 int dm_register_path_selector(struct path_selector_type *pst)
99 {
100 	int r = 0;
101 	struct ps_internal *psi = _alloc_path_selector(pst);
102 
103 	if (!psi)
104 		return -ENOMEM;
105 
106 	down_write(&_ps_lock);
107 
108 	if (__find_path_selector_type(pst->name)) {
109 		kfree(psi);
110 		r = -EEXIST;
111 	} else
112 		list_add(&psi->list, &_path_selectors);
113 
114 	up_write(&_ps_lock);
115 
116 	return r;
117 }
118 EXPORT_SYMBOL_GPL(dm_register_path_selector);
119 
dm_unregister_path_selector(struct path_selector_type * pst)120 int dm_unregister_path_selector(struct path_selector_type *pst)
121 {
122 	struct ps_internal *psi;
123 
124 	down_write(&_ps_lock);
125 
126 	psi = __find_path_selector_type(pst->name);
127 	if (!psi) {
128 		up_write(&_ps_lock);
129 		return -EINVAL;
130 	}
131 
132 	list_del(&psi->list);
133 
134 	up_write(&_ps_lock);
135 
136 	kfree(psi);
137 
138 	return 0;
139 }
140 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);
141