1 /*-
2 * Copyright (c) 2010 Isilon Systems, Inc.
3 * Copyright (c) 2010 iX Systems, Inc.
4 * Copyright (c) 2010 Panasas, Inc.
5 * Copyright (c) 2013-2020 François Tigeot <ftigeot@wolfpond.org>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice unmodified, this list of conditions, and the following
13 * disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30 #ifndef _LINUX_KREF_H_
31 #define _LINUX_KREF_H_
32
33 #include <linux/spinlock.h>
34 #include <linux/refcount.h>
35
36 struct kref {
37 refcount_t refcount;
38 };
39
40 static inline void
kref_init(struct kref * kref)41 kref_init(struct kref *kref)
42 {
43 atomic_set(&kref->refcount.refs, 1);
44 }
45
46 static inline unsigned int
kref_read(const struct kref * kref)47 kref_read(const struct kref *kref)
48 {
49 return atomic_read(&kref->refcount.refs);
50 }
51
52 static inline void
kref_get(struct kref * kref)53 kref_get(struct kref *kref)
54 {
55 refcount_inc(&kref->refcount);
56 }
57
58 static inline int
kref_put(struct kref * kref,void (* release)(struct kref * kref))59 kref_put(struct kref *kref, void (*release)(struct kref *kref))
60 {
61 if (atomic_dec_and_test(&kref->refcount.refs)) {
62 release(kref);
63 return 1;
64 }
65
66 return 0;
67 }
68
69 #if 0
70 static inline int
71 kref_sub(struct kref *kref, unsigned int count,
72 void (*rel)(struct kref *kref))
73 {
74 if (refcount_release_n(&kref->refcount.counter, count)) {
75 rel(kref);
76 return 1;
77 }
78 return 0;
79 }
80 #endif
81
82 /*
83 * kref_get_unless_zero: Increment refcount for object unless it is zero.
84 */
kref_get_unless_zero(struct kref * kref)85 static inline int __must_check kref_get_unless_zero(struct kref *kref)
86 {
87 return atomic_add_unless(&kref->refcount.refs, 1, 0);
88 }
89
kref_put_mutex(struct kref * kref,void (* release)(struct kref * kref),struct lock * lock)90 static inline int kref_put_mutex(struct kref *kref,
91 void (*release)(struct kref *kref),
92 struct lock *lock)
93 {
94 if (!atomic_add_unless(&kref->refcount.refs, -1, 1)) {
95 mutex_lock(lock);
96 if (likely(atomic_dec_and_test(&kref->refcount.refs))) {
97 release(kref);
98 return 1;
99 }
100 mutex_unlock(lock);
101 return 0;
102 }
103
104 return 0;
105 }
106
107 #endif /* _LINUX_KREF_H_ */
108