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      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 
     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 = 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 
     55 void
     56 unique_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 
     63 void
     64 unique_fini(void)
     65 {
     66 	avl_destroy(&unique_avl);
     67 	mutex_destroy(&unique_mtx);
     68 }
     69 
     70 uint64_t
     71 unique_create(void)
     72 {
     73 	uint64_t value = unique_insert(0);
     74 	unique_remove(value);
     75 	return (value);
     76 }
     77 
     78 uint64_t
     79 unique_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 
    102 void
    103 unique_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