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 by Delphix. All rights reserved.
24 */
25
26 #include <sys/zfs_context.h>
27 #include <sys/refcount.h>
28
29 #ifdef ZFS_DEBUG
30
31 #ifdef _KERNEL
32 int reference_tracking_enable = FALSE; /* runs out of memory too easily */
33 SYSCTL_DECL(_vfs_zfs);
34 SYSCTL_INT(_vfs_zfs, OID_AUTO, reference_tracking_enable, CTLFLAG_RDTUN,
35 &reference_tracking_enable, 0,
36 "Track reference holders to refcount_t objects, used mostly by ZFS");
37 #else
38 int reference_tracking_enable = TRUE;
39 #endif
40 int reference_history = 3; /* tunable */
41
42 static kmem_cache_t *reference_cache;
43 static kmem_cache_t *reference_history_cache;
44
45 void
refcount_sysinit(void)46 refcount_sysinit(void)
47 {
48 reference_cache = kmem_cache_create("reference_cache",
49 sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
50
51 reference_history_cache = kmem_cache_create("reference_history_cache",
52 sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
53 }
54
55 void
refcount_fini(void)56 refcount_fini(void)
57 {
58 kmem_cache_destroy(reference_cache);
59 kmem_cache_destroy(reference_history_cache);
60 }
61
62 void
refcount_create(refcount_t * rc)63 refcount_create(refcount_t *rc)
64 {
65 mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
66 list_create(&rc->rc_list, sizeof (reference_t),
67 offsetof(reference_t, ref_link));
68 list_create(&rc->rc_removed, sizeof (reference_t),
69 offsetof(reference_t, ref_link));
70 rc->rc_count = 0;
71 rc->rc_removed_count = 0;
72 rc->rc_tracked = reference_tracking_enable;
73 }
74
75 void
refcount_create_untracked(refcount_t * rc)76 refcount_create_untracked(refcount_t *rc)
77 {
78 refcount_create(rc);
79 rc->rc_tracked = B_FALSE;
80 }
81
82 void
refcount_destroy_many(refcount_t * rc,uint64_t number)83 refcount_destroy_many(refcount_t *rc, uint64_t number)
84 {
85 reference_t *ref;
86
87 ASSERT(rc->rc_count == number);
88 while (ref = list_head(&rc->rc_list)) {
89 list_remove(&rc->rc_list, ref);
90 kmem_cache_free(reference_cache, ref);
91 }
92 list_destroy(&rc->rc_list);
93
94 while (ref = list_head(&rc->rc_removed)) {
95 list_remove(&rc->rc_removed, ref);
96 kmem_cache_free(reference_history_cache, ref->ref_removed);
97 kmem_cache_free(reference_cache, ref);
98 }
99 list_destroy(&rc->rc_removed);
100 mutex_destroy(&rc->rc_mtx);
101 }
102
103 void
refcount_destroy(refcount_t * rc)104 refcount_destroy(refcount_t *rc)
105 {
106 refcount_destroy_many(rc, 0);
107 }
108
109 int
refcount_is_zero(refcount_t * rc)110 refcount_is_zero(refcount_t *rc)
111 {
112 return (rc->rc_count == 0);
113 }
114
115 int64_t
refcount_count(refcount_t * rc)116 refcount_count(refcount_t *rc)
117 {
118 return (rc->rc_count);
119 }
120
121 int64_t
refcount_add_many(refcount_t * rc,uint64_t number,void * holder)122 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
123 {
124 reference_t *ref = NULL;
125 int64_t count;
126
127 if (rc->rc_tracked) {
128 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
129 ref->ref_holder = holder;
130 ref->ref_number = number;
131 }
132 mutex_enter(&rc->rc_mtx);
133 ASSERT(rc->rc_count >= 0);
134 if (rc->rc_tracked)
135 list_insert_head(&rc->rc_list, ref);
136 rc->rc_count += number;
137 count = rc->rc_count;
138 mutex_exit(&rc->rc_mtx);
139
140 return (count);
141 }
142
143 int64_t
refcount_add(refcount_t * rc,void * holder)144 refcount_add(refcount_t *rc, void *holder)
145 {
146 return (refcount_add_many(rc, 1, holder));
147 }
148
149 int64_t
refcount_remove_many(refcount_t * rc,uint64_t number,void * holder)150 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
151 {
152 reference_t *ref;
153 int64_t count;
154
155 mutex_enter(&rc->rc_mtx);
156 ASSERT(rc->rc_count >= number);
157
158 if (!rc->rc_tracked) {
159 rc->rc_count -= number;
160 count = rc->rc_count;
161 mutex_exit(&rc->rc_mtx);
162 return (count);
163 }
164
165 for (ref = list_head(&rc->rc_list); ref;
166 ref = list_next(&rc->rc_list, ref)) {
167 if (ref->ref_holder == holder && ref->ref_number == number) {
168 list_remove(&rc->rc_list, ref);
169 if (reference_history > 0) {
170 ref->ref_removed =
171 kmem_cache_alloc(reference_history_cache,
172 KM_SLEEP);
173 list_insert_head(&rc->rc_removed, ref);
174 rc->rc_removed_count++;
175 if (rc->rc_removed_count > reference_history) {
176 ref = list_tail(&rc->rc_removed);
177 list_remove(&rc->rc_removed, ref);
178 kmem_cache_free(reference_history_cache,
179 ref->ref_removed);
180 kmem_cache_free(reference_cache, ref);
181 rc->rc_removed_count--;
182 }
183 } else {
184 kmem_cache_free(reference_cache, ref);
185 }
186 rc->rc_count -= number;
187 count = rc->rc_count;
188 mutex_exit(&rc->rc_mtx);
189 return (count);
190 }
191 }
192 panic("No such hold %p on refcount %llx", holder,
193 (u_longlong_t)(uintptr_t)rc);
194 return (-1);
195 }
196
197 int64_t
refcount_remove(refcount_t * rc,void * holder)198 refcount_remove(refcount_t *rc, void *holder)
199 {
200 return (refcount_remove_many(rc, 1, holder));
201 }
202
203 void
refcount_transfer(refcount_t * dst,refcount_t * src)204 refcount_transfer(refcount_t *dst, refcount_t *src)
205 {
206 int64_t count, removed_count;
207 list_t list, removed;
208
209 list_create(&list, sizeof (reference_t),
210 offsetof(reference_t, ref_link));
211 list_create(&removed, sizeof (reference_t),
212 offsetof(reference_t, ref_link));
213
214 mutex_enter(&src->rc_mtx);
215 count = src->rc_count;
216 removed_count = src->rc_removed_count;
217 src->rc_count = 0;
218 src->rc_removed_count = 0;
219 list_move_tail(&list, &src->rc_list);
220 list_move_tail(&removed, &src->rc_removed);
221 mutex_exit(&src->rc_mtx);
222
223 mutex_enter(&dst->rc_mtx);
224 dst->rc_count += count;
225 dst->rc_removed_count += removed_count;
226 list_move_tail(&dst->rc_list, &list);
227 list_move_tail(&dst->rc_removed, &removed);
228 mutex_exit(&dst->rc_mtx);
229
230 list_destroy(&list);
231 list_destroy(&removed);
232 }
233
234 #endif /* ZFS_DEBUG */
235