/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 */

#define DEBUG_SUBSYSTEM S_LDLM
#include <libcfs/libcfs.h>

#include <lustre_dlm.h>
#include <lustre_lib.h>

/**
 * Lock a lock and its resource.
 *
 * LDLM locking uses resource to serialize access to locks
 * but there is a case when we change resource of lock upon
 * enqueue reply. We rely on rcu_assign_pointer(lock->l_resource, new_res)
 * being an atomic operation.
 */
struct ldlm_resource *lock_res_and_lock(struct ldlm_lock *lock)
{
	struct ldlm_resource *res;

	rcu_read_lock();
	while (1) {
		res = rcu_dereference(lock->l_resource);
		lock_res(res);
		if (res == lock->l_resource) {
			ldlm_set_res_locked(lock);
			rcu_read_unlock();
			return res;
		}
		unlock_res(res);
	}
}
EXPORT_SYMBOL(lock_res_and_lock);

/**
 * Unlock a lock and its resource previously locked with lock_res_and_lock
 */
void unlock_res_and_lock(struct ldlm_lock *lock)
{
	ldlm_clear_res_locked(lock);

	unlock_res(lock->l_resource);
}
EXPORT_SYMBOL(unlock_res_and_lock);