1 files changed, 327 insertions, 0 deletions
diff --git a/sys/contrib/openzfs/module/zfs/refcount.c b/sys/contrib/openzfs/module/zfs/refcount.c
new file mode 100644
index 000000000000..39476261edfb
--- /dev/null
+++ b/sys/contrib/openzfs/module/zfs/refcount.c
@@ -0,0 +1,327 @@
+/*
+ * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/zfs_refcount.h>
+
+/*
+ * Reference count tracking is disabled by default.  It's memory requirements
+ * are reasonable, however as implemented it consumes a significant amount of
+ * cpu time.  Until its performance is improved it should be manually enabled.
+ */
+int reference_tracking_enable = FALSE;
+int reference_history = 3; /* tunable */
+
+#ifdef	ZFS_DEBUG
+static kmem_cache_t *reference_cache;
+static kmem_cache_t *reference_history_cache;
+
+void
+zfs_refcount_init(void)
+{
+	reference_cache = kmem_cache_create("reference_cache",
+	    sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
+
+	reference_history_cache = kmem_cache_create("reference_history_cache",
+	    sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
+}
+
+void
+zfs_refcount_fini(void)
+{
+	kmem_cache_destroy(reference_cache);
+	kmem_cache_destroy(reference_history_cache);
+}
+
+void
+zfs_refcount_create(zfs_refcount_t *rc)
+{
+	mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
+	list_create(&rc->rc_list, sizeof (reference_t),
+	    offsetof(reference_t, ref_link));
+	list_create(&rc->rc_removed, sizeof (reference_t),
+	    offsetof(reference_t, ref_link));
+	rc->rc_count = 0;
+	rc->rc_removed_count = 0;
+	rc->rc_tracked = reference_tracking_enable;
+}
+
+void
+zfs_refcount_create_tracked(zfs_refcount_t *rc)
+{
+	zfs_refcount_create(rc);
+	rc->rc_tracked = B_TRUE;
+}
+
+void
+zfs_refcount_create_untracked(zfs_refcount_t *rc)
+{
+	zfs_refcount_create(rc);
+	rc->rc_tracked = B_FALSE;
+}
+
+void
+zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number)
+{
+	reference_t *ref;
+
+	ASSERT3U(rc->rc_count, ==, number);
+	while ((ref = list_head(&rc->rc_list))) {
+		list_remove(&rc->rc_list, ref);
+		kmem_cache_free(reference_cache, ref);
+	}
+	list_destroy(&rc->rc_list);
+
+	while ((ref = list_head(&rc->rc_removed))) {
+		list_remove(&rc->rc_removed, ref);
+		kmem_cache_free(reference_history_cache, ref->ref_removed);
+		kmem_cache_free(reference_cache, ref);
+	}
+	list_destroy(&rc->rc_removed);
+	mutex_destroy(&rc->rc_mtx);
+}
+
+void
+zfs_refcount_destroy(zfs_refcount_t *rc)
+{
+	zfs_refcount_destroy_many(rc, 0);
+}
+
+int
+zfs_refcount_is_zero(zfs_refcount_t *rc)
+{
+	return (rc->rc_count == 0);
+}
+
+int64_t
+zfs_refcount_count(zfs_refcount_t *rc)
+{
+	return (rc->rc_count);
+}
+
+int64_t
+zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder)
+{
+	reference_t *ref = NULL;
+	int64_t count;
+
+	if (rc->rc_tracked) {
+		ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
+		ref->ref_holder = holder;
+		ref->ref_number = number;
+	}
+	mutex_enter(&rc->rc_mtx);
+	ASSERT3U(rc->rc_count, >=, 0);
+	if (rc->rc_tracked)
+		list_insert_head(&rc->rc_list, ref);
+	rc->rc_count += number;
+	count = rc->rc_count;
+	mutex_exit(&rc->rc_mtx);
+
+	return (count);
+}
+
+int64_t
+zfs_refcount_add(zfs_refcount_t *rc, const void *holder)
+{
+	return (zfs_refcount_add_many(rc, 1, holder));
+}
+
+int64_t
+zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number,
+    const void *holder)
+{
+	reference_t *ref;
+	int64_t count;
+
+	mutex_enter(&rc->rc_mtx);
+	ASSERT3U(rc->rc_count, >=, number);
+
+	if (!rc->rc_tracked) {
+		rc->rc_count -= number;
+		count = rc->rc_count;
+		mutex_exit(&rc->rc_mtx);
+		return (count);
+	}
+
+	for (ref = list_head(&rc->rc_list); ref;
+	    ref = list_next(&rc->rc_list, ref)) {
+		if (ref->ref_holder == holder && ref->ref_number == number) {
+			list_remove(&rc->rc_list, ref);
+			if (reference_history > 0) {
+				ref->ref_removed =
+				    kmem_cache_alloc(reference_history_cache,
+				    KM_SLEEP);
+				list_insert_head(&rc->rc_removed, ref);
+				rc->rc_removed_count++;
+				if (rc->rc_removed_count > reference_history) {
+					ref = list_tail(&rc->rc_removed);
+					list_remove(&rc->rc_removed, ref);
+					kmem_cache_free(reference_history_cache,
+					    ref->ref_removed);
+					kmem_cache_free(reference_cache, ref);
+					rc->rc_removed_count--;
+				}
+			} else {
+				kmem_cache_free(reference_cache, ref);
+			}
+			rc->rc_count -= number;
+			count = rc->rc_count;
+			mutex_exit(&rc->rc_mtx);
+			return (count);
+		}
+	}
+	panic("No such hold %p on refcount %llx", holder,
+	    (u_longlong_t)(uintptr_t)rc);
+	return (-1);
+}
+
+int64_t
+zfs_refcount_remove(zfs_refcount_t *rc, const void *holder)
+{
+	return (zfs_refcount_remove_many(rc, 1, holder));
+}
+
+void
+zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src)
+{
+	int64_t count, removed_count;
+	list_t list, removed;
+
+	list_create(&list, sizeof (reference_t),
+	    offsetof(reference_t, ref_link));
+	list_create(&removed, sizeof (reference_t),
+	    offsetof(reference_t, ref_link));
+
+	mutex_enter(&src->rc_mtx);
+	count = src->rc_count;
+	removed_count = src->rc_removed_count;
+	src->rc_count = 0;
+	src->rc_removed_count = 0;
+	list_move_tail(&list, &src->rc_list);
+	list_move_tail(&removed, &src->rc_removed);
+	mutex_exit(&src->rc_mtx);
+
+	mutex_enter(&dst->rc_mtx);
+	dst->rc_count += count;
+	dst->rc_removed_count += removed_count;
+	list_move_tail(&dst->rc_list, &list);
+	list_move_tail(&dst->rc_removed, &removed);
+	mutex_exit(&dst->rc_mtx);
+
+	list_destroy(&list);
+	list_destroy(&removed);
+}
+
+void
+zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number,
+    const void *current_holder, const void *new_holder)
+{
+	reference_t *ref;
+	boolean_t found = B_FALSE;
+
+	mutex_enter(&rc->rc_mtx);
+	if (!rc->rc_tracked) {
+		mutex_exit(&rc->rc_mtx);
+		return;
+	}
+
+	for (ref = list_head(&rc->rc_list); ref;
+	    ref = list_next(&rc->rc_list, ref)) {
+		if (ref->ref_holder == current_holder &&
+		    ref->ref_number == number) {
+			ref->ref_holder = new_holder;
+			found = B_TRUE;
+			break;
+		}
+	}
+	ASSERT(found);
+	mutex_exit(&rc->rc_mtx);
+}
+
+void
+zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder,
+    const void *new_holder)
+{
+	return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder,
+	    new_holder));
+}
+
+/*
+ * If tracking is enabled, return true if a reference exists that matches
+ * the "holder" tag. If tracking is disabled, then return true if a reference
+ * might be held.
+ */
+boolean_t
+zfs_refcount_held(zfs_refcount_t *rc, const void *holder)
+{
+	reference_t *ref;
+
+	mutex_enter(&rc->rc_mtx);
+
+	if (!rc->rc_tracked) {
+		mutex_exit(&rc->rc_mtx);
+		return (rc->rc_count > 0);
+	}
+
+	for (ref = list_head(&rc->rc_list); ref;
+	    ref = list_next(&rc->rc_list, ref)) {
+		if (ref->ref_holder == holder) {
+			mutex_exit(&rc->rc_mtx);
+			return (B_TRUE);
+		}
+	}
+	mutex_exit(&rc->rc_mtx);
+	return (B_FALSE);
+}
+
+/*
+ * If tracking is enabled, return true if a reference does not exist that
+ * matches the "holder" tag. If tracking is disabled, always return true
+ * since the reference might not be held.
+ */
+boolean_t
+zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder)
+{
+	reference_t *ref;
+
+	mutex_enter(&rc->rc_mtx);
+
+	if (!rc->rc_tracked) {
+		mutex_exit(&rc->rc_mtx);
+		return (B_TRUE);
+	}
+
+	for (ref = list_head(&rc->rc_list); ref;
+	    ref = list_next(&rc->rc_list, ref)) {
+		if (ref->ref_holder == holder) {
+			mutex_exit(&rc->rc_mtx);
+			return (B_FALSE);
+		}
+	}
+	mutex_exit(&rc->rc_mtx);
+	return (B_TRUE);
+}
+#endif	/* ZFS_DEBUG */