xref: /illumos-gate/usr/src/uts/common/fs/zfs/sys/refcount.h (revision ecd18dec)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23  * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
24  */
25 
26 #ifndef	_SYS_REFCOUNT_H
27 #define	_SYS_REFCOUNT_H
28 
29 #include <sys/inttypes.h>
30 #include <sys/list.h>
31 #include <sys/zfs_context.h>
32 
33 #ifdef	__cplusplus
34 extern "C" {
35 #endif
36 
37 /*
38  * If the reference is held only by the calling function and not any
39  * particular object, use FTAG (which is a string) for the holder_tag.
40  * Otherwise, use the object that holds the reference.
41  */
42 #define	FTAG ((char *)(uintptr_t)__func__)
43 
44 #ifdef	ZFS_DEBUG
45 typedef struct reference {
46 	list_node_t ref_link;
47 	const void *ref_holder;
48 	uint64_t ref_number;
49 	uint8_t *ref_removed;
50 } reference_t;
51 
52 typedef struct refcount {
53 	kmutex_t rc_mtx;
54 	boolean_t rc_tracked;
55 	list_t rc_list;
56 	list_t rc_removed;
57 	uint64_t rc_count;
58 	uint64_t rc_removed_count;
59 } zfs_refcount_t;
60 
61 /*
62  * Note: zfs_refcount_t must be initialized with
63  * refcount_create[_untracked]()
64  */
65 
66 void zfs_refcount_create(zfs_refcount_t *);
67 void zfs_refcount_create_untracked(zfs_refcount_t *);
68 void zfs_refcount_create_tracked(zfs_refcount_t *);
69 void zfs_refcount_destroy(zfs_refcount_t *);
70 void zfs_refcount_destroy_many(zfs_refcount_t *, uint64_t);
71 int zfs_refcount_is_zero(zfs_refcount_t *);
72 int64_t zfs_refcount_count(zfs_refcount_t *);
73 int64_t zfs_refcount_add(zfs_refcount_t *, const void *);
74 int64_t zfs_refcount_remove(zfs_refcount_t *, const void *);
75 /*
76  * Note that (add|remove)_many adds/removes one reference with "number" N,
77  * _not_ N references with "number" 1, which is what (add|remove)_few does,
78  * or what vanilla zfs_refcount_(add|remove) called N times would do.
79  *
80  * That is, add_many should be used to add N references at once when they will
81  * subsequently be removed together via a call to remove_many. And they must be
82  * -- attempting to remove a reference with number N when none exists is a
83  * panic on debug kernels with reference_tracking enabled.
84  *
85  * add_few should be used to add N references at once when they may be removed
86  * again piecemeal, via multiple calls to remove and remove_few.
87  */
88 void zfs_refcount_add_few(zfs_refcount_t *, uint64_t, const void *);
89 void zfs_refcount_remove_few(zfs_refcount_t *, uint64_t, const void *);
90 int64_t zfs_refcount_add_many(zfs_refcount_t *, uint64_t, const void *);
91 int64_t zfs_refcount_remove_many(zfs_refcount_t *, uint64_t, const void *);
92 void zfs_refcount_transfer(zfs_refcount_t *, zfs_refcount_t *);
93 void zfs_refcount_transfer_ownership(zfs_refcount_t *, void *, void *);
94 void zfs_refcount_transfer_ownership_many(zfs_refcount_t *, uint64_t,
95     void *, void *);
96 boolean_t zfs_refcount_held(zfs_refcount_t *, void *);
97 boolean_t zfs_refcount_not_held(zfs_refcount_t *, void *);
98 
99 void zfs_refcount_init(void);
100 void zfs_refcount_fini(void);
101 
102 #else	/* ZFS_DEBUG */
103 
104 typedef struct refcount {
105 	uint64_t rc_count;
106 } zfs_refcount_t;
107 
108 #define	zfs_refcount_create(rc) ((rc)->rc_count = 0)
109 #define	zfs_refcount_create_untracked(rc) ((rc)->rc_count = 0)
110 #define	zfs_refcount_create_tracked(rc) ((rc)->rc_count = 0)
111 #define	zfs_refcount_destroy(rc) ((rc)->rc_count = 0)
112 #define	zfs_refcount_destroy_many(rc, number) ((rc)->rc_count = 0)
113 #define	zfs_refcount_is_zero(rc) ((rc)->rc_count == 0)
114 #define	zfs_refcount_count(rc) ((rc)->rc_count)
115 #define	zfs_refcount_add(rc, holder) atomic_inc_64_nv(&(rc)->rc_count)
116 #define	zfs_refcount_remove(rc, holder) atomic_dec_64_nv(&(rc)->rc_count)
117 #define	zfs_refcount_add_few(rc, number, holder) \
118 	atomic_add_64(&(rc)->rc_count, number)
119 #define	zfs_refcount_remove_few(rc, number, holder) \
120 	atomic_add_64(&(rc)->rc_count, -number)
121 #define	zfs_refcount_add_many(rc, number, holder) \
122 	atomic_add_64_nv(&(rc)->rc_count, number)
123 #define	zfs_refcount_remove_many(rc, number, holder) \
124 	atomic_add_64_nv(&(rc)->rc_count, -number)
125 #define	zfs_refcount_transfer(dst, src) { \
126 	uint64_t __tmp = (src)->rc_count; \
127 	atomic_add_64(&(src)->rc_count, -__tmp); \
128 	atomic_add_64(&(dst)->rc_count, __tmp); \
129 }
130 #define	zfs_refcount_transfer_ownership(rc, current_holder, new_holder)	(void)0
131 #define	zfs_refcount_transfer_ownership_many(rc, nr, ch, nh)	((void)0)
132 #define	zfs_refcount_held(rc, holder)		((rc)->rc_count > 0)
133 #define	zfs_refcount_not_held(rc, holder)		(B_TRUE)
134 
135 #define	zfs_refcount_init()
136 #define	zfs_refcount_fini()
137 
138 #endif	/* ZFS_DEBUG */
139 
140 #ifdef	__cplusplus
141 }
142 #endif
143 
144 #endif /* _SYS_REFCOUNT_H */
145