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
20struct 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
27static LIST_HEAD(_path_selectors);
28static DECLARE_RWSEM(_ps_lock);
29
30static 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
42static 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
55struct 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
71void 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);
84out:
85	up_read(&_ps_lock);
86}
87
88static 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
98int 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}
118EXPORT_SYMBOL_GPL(dm_register_path_selector);
119
120int 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}
140EXPORT_SYMBOL_GPL(dm_unregister_path_selector);
141