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);