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 François 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  * $FreeBSD$
31  */
32 #ifndef _LINUX_KREF_H_
33 #define _LINUX_KREF_H_
34 
35 #include <sys/types.h>
36 #include <sys/refcount.h>
37 
38 #include <linux/compiler.h>
39 #include <linux/kernel.h>
40 #include <linux/mutex.h>
41 
42 #include <asm/atomic.h>
43 
44 struct kref {
45 	atomic_t refcount;
46 };
47 
48 static inline void
49 kref_init(struct kref *kref)
50 {
51 
52 	refcount_init(&kref->refcount.counter, 1);
53 }
54 
55 static inline unsigned int
56 kref_read(const struct kref *kref)
57 {
58 
59 	return (atomic_read(&kref->refcount));
60 }
61 
62 static inline void
63 kref_get(struct kref *kref)
64 {
65 
66 	refcount_acquire(&kref->refcount.counter);
67 }
68 
69 static inline int
70 kref_put(struct kref *kref, void (*rel)(struct kref *kref))
71 {
72 
73 	if (refcount_release(&kref->refcount.counter)) {
74 		rel(kref);
75 		return 1;
76 	}
77 	return 0;
78 }
79 
80 static inline int
81 kref_sub(struct kref *kref, unsigned int count,
82     void (*rel)(struct kref *kref))
83 {
84 
85 	while (count--) {
86 		if (refcount_release(&kref->refcount.counter)) {
87 			rel(kref);
88 			return 1;
89 		}
90 	}
91 	return 0;
92 }
93 
94 static inline int __must_check
95 kref_get_unless_zero(struct kref *kref)
96 {
97 
98 	return atomic_add_unless(&kref->refcount, 1, 0);
99 }
100 
101 static inline int kref_put_mutex(struct kref *kref,
102     void (*release)(struct kref *kref), struct mutex *lock)
103 {
104 	WARN_ON(release == NULL);
105 	if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) {
106 		mutex_lock(lock);
107 		if (unlikely(!atomic_dec_and_test(&kref->refcount))) {
108 			mutex_unlock(lock);
109 			return 0;
110 		}
111 		release(kref);
112 		return 1;
113 	}
114 	return 0;
115 }
116 
117 #endif /* _LINUX_KREF_H_ */
118