1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 */
25
26#pragma ident	"%Z%%M%	%I%	%E% SMI"
27
28#include <sys/zfs_context.h>
29#include <sys/avl.h>
30#include <sys/unique.h>
31
32static avl_tree_t unique_avl;
33static kmutex_t unique_mtx;
34
35typedef struct unique {
36	avl_node_t un_link;
37	uint64_t un_value;
38} unique_t;
39
40#define	UNIQUE_MASK ((1ULL << UNIQUE_BITS) - 1)
41
42static int
43unique_compare(const void *a, const void *b)
44{
45	const unique_t *una = a;
46	const unique_t *unb = b;
47
48	if (una->un_value < unb->un_value)
49		return (-1);
50	if (una->un_value > unb->un_value)
51		return (+1);
52	return (0);
53}
54
55void
56unique_init(void)
57{
58	avl_create(&unique_avl, unique_compare,
59	    sizeof (unique_t), offsetof(unique_t, un_link));
60	mutex_init(&unique_mtx, NULL, MUTEX_DEFAULT, NULL);
61}
62
63void
64unique_fini(void)
65{
66	avl_destroy(&unique_avl);
67	mutex_destroy(&unique_mtx);
68}
69
70uint64_t
71unique_create(void)
72{
73	uint64_t value = unique_insert(0);
74	unique_remove(value);
75	return (value);
76}
77
78uint64_t
79unique_insert(uint64_t value)
80{
81	avl_index_t idx;
82	unique_t *un = kmem_alloc(sizeof (unique_t), KM_SLEEP);
83
84	un->un_value = value;
85
86	mutex_enter(&unique_mtx);
87	while (un->un_value == 0 || un->un_value & ~UNIQUE_MASK ||
88	    avl_find(&unique_avl, un, &idx)) {
89		mutex_exit(&unique_mtx);
90		(void) random_get_pseudo_bytes((void*)&un->un_value,
91		    sizeof (un->un_value));
92		un->un_value &= UNIQUE_MASK;
93		mutex_enter(&unique_mtx);
94	}
95
96	avl_insert(&unique_avl, un, idx);
97	mutex_exit(&unique_mtx);
98
99	return (un->un_value);
100}
101
102void
103unique_remove(uint64_t value)
104{
105	unique_t un_tofind;
106	unique_t *un;
107
108	un_tofind.un_value = value;
109	mutex_enter(&unique_mtx);
110	un = avl_find(&unique_avl, &un_tofind, NULL);
111	if (un != NULL) {
112		avl_remove(&unique_avl, un);
113		kmem_free(un, sizeof (unique_t));
114	}
115	mutex_exit(&unique_mtx);
116}
117