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#include <sys/zfs_context.h>
27#include <sys/avl.h>
28#include <sys/unique.h>
29
30static avl_tree_t unique_avl;
31static kmutex_t unique_mtx;
32
33typedef struct unique {
34	avl_node_t un_link;
35	uint64_t un_value;
36} unique_t;
37
38#define	UNIQUE_MASK ((1ULL << UNIQUE_BITS) - 1)
39
40static int
41unique_compare(const void *a, const void *b)
42{
43	const unique_t *una = (const unique_t *)a;
44	const unique_t *unb = (const unique_t *)b;
45
46	return (TREE_CMP(una->un_value, unb->un_value));
47}
48
49void
50unique_init(void)
51{
52	avl_create(&unique_avl, unique_compare,
53	    sizeof (unique_t), offsetof(unique_t, un_link));
54	mutex_init(&unique_mtx, NULL, MUTEX_DEFAULT, NULL);
55}
56
57void
58unique_fini(void)
59{
60	avl_destroy(&unique_avl);
61	mutex_destroy(&unique_mtx);
62}
63
64uint64_t
65unique_create(void)
66{
67	uint64_t value = unique_insert(0);
68	unique_remove(value);
69	return (value);
70}
71
72uint64_t
73unique_insert(uint64_t value)
74{
75	avl_index_t idx;
76	unique_t *un = kmem_alloc(sizeof (unique_t), KM_SLEEP);
77
78	un->un_value = value;
79
80	mutex_enter(&unique_mtx);
81	while (un->un_value == 0 || un->un_value & ~UNIQUE_MASK ||
82	    avl_find(&unique_avl, un, &idx)) {
83		mutex_exit(&unique_mtx);
84		(void) random_get_pseudo_bytes((void*)&un->un_value,
85		    sizeof (un->un_value));
86		un->un_value &= UNIQUE_MASK;
87		mutex_enter(&unique_mtx);
88	}
89
90	avl_insert(&unique_avl, un, idx);
91	mutex_exit(&unique_mtx);
92
93	return (un->un_value);
94}
95
96void
97unique_remove(uint64_t value)
98{
99	unique_t un_tofind;
100	unique_t *un;
101
102	un_tofind.un_value = value;
103	mutex_enter(&unique_mtx);
104	un = avl_find(&unique_avl, &un_tofind, NULL);
105	if (un != NULL) {
106		avl_remove(&unique_avl, un);
107		kmem_free(un, sizeof (unique_t));
108	}
109	mutex_exit(&unique_mtx);
110}
111