module/zfs/unique.c

   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
  27
  28 #include <sys/zfs_context.h>
  29 #include <sys/avl.h>
  30 #include <sys/unique.h>
  31
  32 static avl_tree_t unique_avl;
  33 static kmutex_t unique_mtx;
  34
  35 typedef 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
  42 static int
  43 unique_compare(const void *a, const void *b)
  44 {
  45         const unique_t *una = (const unique_t *)a;
  46         const unique_t *unb = (const unique_t *)b;
  47
  48         return (AVL_CMP(una->un_value, unb->un_value));
  49 }
  50
  51 void
  52 unique_init(void)
  53 {
  54         avl_create(&unique_avl, unique_compare,
  55             sizeof (unique_t), offsetof(unique_t, un_link));
  56         mutex_init(&unique_mtx, NULL, MUTEX_DEFAULT, NULL);
  57 }
  58
  59 void
  60 unique_fini(void)
  61 {
  62         avl_destroy(&unique_avl);
  63         mutex_destroy(&unique_mtx);
  64 }
  65
  66 uint64_t
  67 unique_create(void)
  68 {
  69         uint64_t value = unique_insert(0);
  70         unique_remove(value);
  71         return (value);
  72 }
  73
  74 uint64_t
  75 unique_insert(uint64_t value)
  76 {
  77         avl_index_t idx;
  78         unique_t *un = kmem_alloc(sizeof (unique_t), KM_SLEEP);
  79
  80         un->un_value = value;
  81
  82         mutex_enter(&unique_mtx);
  83         while (un->un_value == 0 || un->un_value & ~UNIQUE_MASK ||
  84             avl_find(&unique_avl, un, &idx)) {
  85                 mutex_exit(&unique_mtx);
  86                 (void) random_get_pseudo_bytes((void*)&un->un_value,
  87                     sizeof (un->un_value));
  88                 un->un_value &= UNIQUE_MASK;
  89                 mutex_enter(&unique_mtx);
  90         }
  91
  92         avl_insert(&unique_avl, un, idx);
  93         mutex_exit(&unique_mtx);
  94
  95         return (un->un_value);
  96 }
  97
  98 void
  99 unique_remove(uint64_t value)
 100 {
 101         unique_t un_tofind;
 102         unique_t *un;
 103
 104         un_tofind.un_value = value;
 105         mutex_enter(&unique_mtx);
 106         un = avl_find(&unique_avl, &un_tofind, NULL);
 107         if (un != NULL) {
 108                 avl_remove(&unique_avl, un);
 109                 kmem_free(un, sizeof (unique_t));
 110         }
 111         mutex_exit(&unique_mtx);
 112 }