/*

 * 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 by Delphix. All rights reserved.

 */

#include <sys/zfs_context.h>

#include <sys/refcount.h>

#ifdef	ZFS_DEBUG

#ifdef _KERNEL

int reference_tracking_enable = FALSE; /* runs out of memory too easily */

#else

int reference_tracking_enable = TRUE;

#endif

int reference_history = 3; /* tunable */

static kmem_cache_t *reference_cache;

static kmem_cache_t *reference_history_cache;

void

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

refcount_fini(void)

{

	kmem_cache_destroy(reference_cache);

	kmem_cache_destroy(reference_history_cache);

}

void

refcount_create(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

refcount_create_untracked(refcount_t *rc)

{

	refcount_create(rc);

	rc->rc_tracked = B_FALSE;

}

void

refcount_destroy_many(refcount_t *rc, uint64_t number)

{

	reference_t *ref;

	ASSERT(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

refcount_destroy(refcount_t *rc)

{

	refcount_destroy_many(rc, 0);

}

int

refcount_is_zero(refcount_t *rc)

{

	return (rc->rc_count == 0);

}

int64_t

refcount_count(refcount_t *rc)

{

	return (rc->rc_count);

}

int64_t

refcount_add_many(refcount_t *rc, uint64_t number, 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);

	ASSERT(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

refcount_add(refcount_t *rc, void *holder)

{

	return (refcount_add_many(rc, 1, holder));

}

int64_t

refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)

{

	reference_t *ref;

	int64_t count;

	mutex_enter(&rc->rc_mtx);

	ASSERT(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

refcount_remove(refcount_t *rc, void *holder)

{

	return (refcount_remove_many(rc, 1, holder));

}

void

refcount_transfer(refcount_t *dst, 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);

}

#endif	/* ZFS_DEBUG */