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 41 kref_init(struct kref *kref) 42 { 43 atomic_set(&kref->refcount.refs, 1); 44 } 45 46 static inline unsigned int 47 kref_read(const struct kref *kref) 48 { 49 return atomic_read(&kref->refcount.refs); 50 } 51 52 static inline void 53 kref_get(struct kref *kref) 54 { 55 refcount_inc(&kref->refcount); 56 } 57 58 static inline int 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 */ 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 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