kref.h revision 289578 
1/*-
2 * Copyright (c) 2010 Isilon Systems, Inc.
3 * Copyright (c) 2010 iX Systems, Inc.
4 * Copyright (c) 2010 Panasas, Inc.
5 * Copyright (c) 2013-2015 Mellanox Technologies, Ltd.
6 * Copyright (c) 2013 Fran��ois Tigeot
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice unmodified, this list of conditions, and the following
14 *    disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30#ifndef _LINUX_KREF_H_
31#define _LINUX_KREF_H_
32
33#include <sys/types.h>
34#include <sys/refcount.h>
35
36#include <asm/atomic.h>
37
38struct kref {
39	atomic_t refcount;
40};
41
42static inline void
43kref_init(struct kref *kref)
44{
45
46	refcount_init(&kref->refcount.counter, 1);
47}
48
49static inline void
50kref_get(struct kref *kref)
51{
52
53	refcount_acquire(&kref->refcount.counter);
54}
55
56static inline int
57kref_put(struct kref *kref, void (*rel)(struct kref *kref))
58{
59
60	if (refcount_release(&kref->refcount.counter)) {
61		rel(kref);
62		return 1;
63	}
64	return 0;
65}
66
67static inline int
68kref_sub(struct kref *kref, unsigned int count,
69    void (*rel)(struct kref *kref))
70{
71
72	while (count--) {
73		if (refcount_release(&kref->refcount.counter)) {
74			rel(kref);
75			return 1;
76		}
77	}
78	return 0;
79}
80
81static inline int __must_check
82kref_get_unless_zero(struct kref *kref)
83{
84
85	return atomic_add_unless(&kref->refcount, 1, 0);
86}
87
88#endif /* _LINUX_KREF_H_ */
89