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-rw-r--r--uts/common/fs/zfs/unique.c116
1 files changed, 116 insertions, 0 deletions
diff --git a/uts/common/fs/zfs/unique.c b/uts/common/fs/zfs/unique.c
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+++ b/uts/common/fs/zfs/unique.c
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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma ident "%Z%%M% %I% %E% SMI"
+
+#include <sys/zfs_context.h>
+#include <sys/avl.h>
+#include <sys/unique.h>
+
+static avl_tree_t unique_avl;
+static kmutex_t unique_mtx;
+
+typedef struct unique {
+ avl_node_t un_link;
+ uint64_t un_value;
+} unique_t;
+
+#define UNIQUE_MASK ((1ULL << UNIQUE_BITS) - 1)
+
+static int
+unique_compare(const void *a, const void *b)
+{
+ const unique_t *una = a;
+ const unique_t *unb = b;
+
+ if (una->un_value < unb->un_value)
+ return (-1);
+ if (una->un_value > unb->un_value)
+ return (+1);
+ return (0);
+}
+
+void
+unique_init(void)
+{
+ avl_create(&unique_avl, unique_compare,
+ sizeof (unique_t), offsetof(unique_t, un_link));
+ mutex_init(&unique_mtx, NULL, MUTEX_DEFAULT, NULL);
+}
+
+void
+unique_fini(void)
+{
+ avl_destroy(&unique_avl);
+ mutex_destroy(&unique_mtx);
+}
+
+uint64_t
+unique_create(void)
+{
+ uint64_t value = unique_insert(0);
+ unique_remove(value);
+ return (value);
+}
+
+uint64_t
+unique_insert(uint64_t value)
+{
+ avl_index_t idx;
+ unique_t *un = kmem_alloc(sizeof (unique_t), KM_SLEEP);
+
+ un->un_value = value;
+
+ mutex_enter(&unique_mtx);
+ while (un->un_value == 0 || un->un_value & ~UNIQUE_MASK ||
+ avl_find(&unique_avl, un, &idx)) {
+ mutex_exit(&unique_mtx);
+ (void) random_get_pseudo_bytes((void*)&un->un_value,
+ sizeof (un->un_value));
+ un->un_value &= UNIQUE_MASK;
+ mutex_enter(&unique_mtx);
+ }
+
+ avl_insert(&unique_avl, un, idx);
+ mutex_exit(&unique_mtx);
+
+ return (un->un_value);
+}
+
+void
+unique_remove(uint64_t value)
+{
+ unique_t un_tofind;
+ unique_t *un;
+
+ un_tofind.un_value = value;
+ mutex_enter(&unique_mtx);
+ un = avl_find(&unique_avl, &un_tofind, NULL);
+ if (un != NULL) {
+ avl_remove(&unique_avl, un);
+ kmem_free(un, sizeof (unique_t));
+ }
+ mutex_exit(&unique_mtx);
+}