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
30 static avl_tree_t unique_avl;
31 static kmutex_t unique_mtx;
32
33 typedef 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
40 static int
unique_compare(const void * a,const void * b)41 unique_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
49 void
unique_init(void)50 unique_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
57 void
unique_fini(void)58 unique_fini(void)
59 {
60 avl_destroy(&unique_avl);
61 mutex_destroy(&unique_mtx);
62 }
63
64 uint64_t
unique_create(void)65 unique_create(void)
66 {
67 uint64_t value = unique_insert(0);
68 unique_remove(value);
69 return (value);
70 }
71
72 uint64_t
unique_insert(uint64_t value)73 unique_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
96 void
unique_remove(uint64_t value)97 unique_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