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 
19 struct 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 
26 static LIST_HEAD(_path_selectors);
27 static DECLARE_RWSEM(_ps_lock);
28 
__find_path_selector_type(const char * name)29 static 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 
get_path_selector(const char * name)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 && !try_module_get(psi->pst.module))
48 		psi = NULL;
49 	up_read(&_ps_lock);
50 
51 	return psi;
52 }
53 
dm_get_path_selector(const char * name)54 struct 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 
dm_put_path_selector(struct path_selector_type * pst)70 void 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);
83 out:
84 	up_read(&_ps_lock);
85 }
86 
_alloc_path_selector(struct path_selector_type * pst)87 static 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 
dm_register_path_selector(struct path_selector_type * pst)97 int 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 
dm_unregister_path_selector(struct path_selector_type * pst)118 int 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 
139 EXPORT_SYMBOL_GPL(dm_register_path_selector);
140 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);
141