/*-
 * Copyright (c) 2010 Isilon Systems, Inc.
 * Copyright (c) 2010 iX Systems, Inc.
 * Copyright (c) 2010 Panasas, Inc.
 * Copyright (c) 2013-2020 François Tigeot <ftigeot@wolfpond.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _LINUX_KREF_H_
#define _LINUX_KREF_H_

#include <linux/spinlock.h>
#include <linux/refcount.h>

struct kref {
        refcount_t refcount;
};

static inline void
kref_init(struct kref *kref)
{
        atomic_set(&kref->refcount.refs, 1);
}

static inline unsigned int
kref_read(const struct kref *kref)
{
        return atomic_read(&kref->refcount.refs);
}

static inline void
kref_get(struct kref *kref)
{
        refcount_inc(&kref->refcount);
}

static inline int
kref_put(struct kref *kref, void (*release)(struct kref *kref))
{
        if (atomic_dec_and_test(&kref->refcount.refs)) {
                release(kref);
                return 1;
        }

        return 0;
}

#if 0
static inline int
kref_sub(struct kref *kref, unsigned int count,
             void (*rel)(struct kref *kref))
{
        if (refcount_release_n(&kref->refcount.counter, count)) {
                rel(kref);
                return 1;
        }
        return 0;
}
#endif

/*
 * kref_get_unless_zero: Increment refcount for object unless it is zero.
 */
static inline int __must_check kref_get_unless_zero(struct kref *kref)
{
        return atomic_add_unless(&kref->refcount.refs, 1, 0);
}

static inline int kref_put_mutex(struct kref *kref,
                                 void (*release)(struct kref *kref),
                                 struct lock *lock)
{
        if (!atomic_add_unless(&kref->refcount.refs, -1, 1)) {
                mutex_lock(lock);
                if (likely(atomic_dec_and_test(&kref->refcount.refs))) {
                        release(kref);
                        return 1;
                }
                mutex_unlock(lock);
                return 0;
        }

        return 0;
}

#endif /* _LINUX_KREF_H_ */