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 #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_tracked(refcount_t * rc)76 refcount_create_tracked(refcount_t *rc)
77 {
78 refcount_create(rc);
79 rc->rc_tracked = B_TRUE;
80 }
81
82 void
refcount_create_untracked(refcount_t * rc)83 refcount_create_untracked(refcount_t *rc)
84 {
85 refcount_create(rc);
86 rc->rc_tracked = B_FALSE;
87 }
88
89 void
refcount_destroy_many(refcount_t * rc,uint64_t number)90 refcount_destroy_many(refcount_t *rc, uint64_t number)
91 {
92 reference_t *ref;
93
94 ASSERT(rc->rc_count == number);
95 while (ref = list_head(&rc->rc_list)) {
96 list_remove(&rc->rc_list, ref);
97 kmem_cache_free(reference_cache, ref);
98 }
99 list_destroy(&rc->rc_list);
100
101 while (ref = list_head(&rc->rc_removed)) {
102 list_remove(&rc->rc_removed, ref);
103 kmem_cache_free(reference_history_cache, ref->ref_removed);
104 kmem_cache_free(reference_cache, ref);
105 }
106 list_destroy(&rc->rc_removed);
107 mutex_destroy(&rc->rc_mtx);
108 }
109
110 void
refcount_destroy(refcount_t * rc)111 refcount_destroy(refcount_t *rc)
112 {
113 refcount_destroy_many(rc, 0);
114 }
115
116 int
refcount_is_zero(refcount_t * rc)117 refcount_is_zero(refcount_t *rc)
118 {
119 return (rc->rc_count == 0);
120 }
121
122 int64_t
refcount_count(refcount_t * rc)123 refcount_count(refcount_t *rc)
124 {
125 return (rc->rc_count);
126 }
127
128 int64_t
refcount_add_many(refcount_t * rc,uint64_t number,void * holder)129 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
130 {
131 reference_t *ref = NULL;
132 int64_t count;
133
134 if (rc->rc_tracked) {
135 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
136 ref->ref_holder = holder;
137 ref->ref_number = number;
138 }
139 mutex_enter(&rc->rc_mtx);
140 ASSERT(rc->rc_count >= 0);
141 if (rc->rc_tracked)
142 list_insert_head(&rc->rc_list, ref);
143 rc->rc_count += number;
144 count = rc->rc_count;
145 mutex_exit(&rc->rc_mtx);
146
147 return (count);
148 }
149
150 int64_t
refcount_add(refcount_t * rc,void * holder)151 refcount_add(refcount_t *rc, void *holder)
152 {
153 return (refcount_add_many(rc, 1, holder));
154 }
155
156 int64_t
refcount_remove_many(refcount_t * rc,uint64_t number,void * holder)157 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
158 {
159 reference_t *ref;
160 int64_t count;
161
162 mutex_enter(&rc->rc_mtx);
163 ASSERT(rc->rc_count >= number);
164
165 if (!rc->rc_tracked) {
166 rc->rc_count -= number;
167 count = rc->rc_count;
168 mutex_exit(&rc->rc_mtx);
169 return (count);
170 }
171
172 for (ref = list_head(&rc->rc_list); ref;
173 ref = list_next(&rc->rc_list, ref)) {
174 if (ref->ref_holder == holder && ref->ref_number == number) {
175 list_remove(&rc->rc_list, ref);
176 if (reference_history > 0) {
177 ref->ref_removed =
178 kmem_cache_alloc(reference_history_cache,
179 KM_SLEEP);
180 list_insert_head(&rc->rc_removed, ref);
181 rc->rc_removed_count++;
182 if (rc->rc_removed_count > reference_history) {
183 ref = list_tail(&rc->rc_removed);
184 list_remove(&rc->rc_removed, ref);
185 kmem_cache_free(reference_history_cache,
186 ref->ref_removed);
187 kmem_cache_free(reference_cache, ref);
188 rc->rc_removed_count--;
189 }
190 } else {
191 kmem_cache_free(reference_cache, ref);
192 }
193 rc->rc_count -= number;
194 count = rc->rc_count;
195 mutex_exit(&rc->rc_mtx);
196 return (count);
197 }
198 }
199 panic("No such hold %p on refcount %llx", holder,
200 (u_longlong_t)(uintptr_t)rc);
201 return (-1);
202 }
203
204 int64_t
refcount_remove(refcount_t * rc,void * holder)205 refcount_remove(refcount_t *rc, void *holder)
206 {
207 return (refcount_remove_many(rc, 1, holder));
208 }
209
210 void
refcount_transfer(refcount_t * dst,refcount_t * src)211 refcount_transfer(refcount_t *dst, refcount_t *src)
212 {
213 int64_t count, removed_count;
214 list_t list, removed;
215
216 list_create(&list, sizeof (reference_t),
217 offsetof(reference_t, ref_link));
218 list_create(&removed, sizeof (reference_t),
219 offsetof(reference_t, ref_link));
220
221 mutex_enter(&src->rc_mtx);
222 count = src->rc_count;
223 removed_count = src->rc_removed_count;
224 src->rc_count = 0;
225 src->rc_removed_count = 0;
226 list_move_tail(&list, &src->rc_list);
227 list_move_tail(&removed, &src->rc_removed);
228 mutex_exit(&src->rc_mtx);
229
230 mutex_enter(&dst->rc_mtx);
231 dst->rc_count += count;
232 dst->rc_removed_count += removed_count;
233 list_move_tail(&dst->rc_list, &list);
234 list_move_tail(&dst->rc_removed, &removed);
235 mutex_exit(&dst->rc_mtx);
236
237 list_destroy(&list);
238 list_destroy(&removed);
239 }
240
241 void
refcount_transfer_ownership(refcount_t * rc,void * current_holder,void * new_holder)242 refcount_transfer_ownership(refcount_t *rc, void *current_holder,
243 void *new_holder)
244 {
245 reference_t *ref;
246 boolean_t found = B_FALSE;
247
248 mutex_enter(&rc->rc_mtx);
249 if (!rc->rc_tracked) {
250 mutex_exit(&rc->rc_mtx);
251 return;
252 }
253
254 for (ref = list_head(&rc->rc_list); ref;
255 ref = list_next(&rc->rc_list, ref)) {
256 if (ref->ref_holder == current_holder) {
257 ref->ref_holder = new_holder;
258 found = B_TRUE;
259 break;
260 }
261 }
262 ASSERT(found);
263 mutex_exit(&rc->rc_mtx);
264 }
265
266 /*
267 * If tracking is enabled, return true if a reference exists that matches
268 * the "holder" tag. If tracking is disabled, then return true if a reference
269 * might be held.
270 */
271 boolean_t
refcount_held(refcount_t * rc,void * holder)272 refcount_held(refcount_t *rc, void *holder)
273 {
274 reference_t *ref;
275
276 mutex_enter(&rc->rc_mtx);
277
278 if (!rc->rc_tracked) {
279 mutex_exit(&rc->rc_mtx);
280 return (rc->rc_count > 0);
281 }
282
283 for (ref = list_head(&rc->rc_list); ref;
284 ref = list_next(&rc->rc_list, ref)) {
285 if (ref->ref_holder == holder) {
286 mutex_exit(&rc->rc_mtx);
287 return (B_TRUE);
288 }
289 }
290 mutex_exit(&rc->rc_mtx);
291 return (B_FALSE);
292 }
293
294 /*
295 * If tracking is enabled, return true if a reference does not exist that
296 * matches the "holder" tag. If tracking is disabled, always return true
297 * since the reference might not be held.
298 */
299 boolean_t
refcount_not_held(refcount_t * rc,void * holder)300 refcount_not_held(refcount_t *rc, void *holder)
301 {
302 reference_t *ref;
303
304 mutex_enter(&rc->rc_mtx);
305
306 if (!rc->rc_tracked) {
307 mutex_exit(&rc->rc_mtx);
308 return (B_TRUE);
309 }
310
311 for (ref = list_head(&rc->rc_list); ref;
312 ref = list_next(&rc->rc_list, ref)) {
313 if (ref->ref_holder == holder) {
314 mutex_exit(&rc->rc_mtx);
315 return (B_FALSE);
316 }
317 }
318 mutex_exit(&rc->rc_mtx);
319 return (B_TRUE);
320 }
321 #endif /* ZFS_DEBUG */
322