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, 2021 by Delphix. All rights reserved.
24 */
25
26 #include <sys/zfs_context.h>
27 #include <sys/zfs_refcount.h>
28
29 /*
30 * Reference count tracking is disabled by default. It's memory requirements
31 * are reasonable, however as implemented it consumes a significant amount of
32 * cpu time. Until its performance is improved it should be manually enabled.
33 */
34 int reference_tracking_enable = FALSE;
35 int reference_history = 3; /* tunable */
36
37 #ifdef ZFS_DEBUG
38 static kmem_cache_t *reference_cache;
39 static kmem_cache_t *reference_history_cache;
40
41 void
zfs_refcount_init(void)42 zfs_refcount_init(void)
43 {
44 reference_cache = kmem_cache_create("reference_cache",
45 sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
46
47 reference_history_cache = kmem_cache_create("reference_history_cache",
48 sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
49 }
50
51 void
zfs_refcount_fini(void)52 zfs_refcount_fini(void)
53 {
54 kmem_cache_destroy(reference_cache);
55 kmem_cache_destroy(reference_history_cache);
56 }
57
58 void
zfs_refcount_create(zfs_refcount_t * rc)59 zfs_refcount_create(zfs_refcount_t *rc)
60 {
61 mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
62 list_create(&rc->rc_list, sizeof (reference_t),
63 offsetof(reference_t, ref_link));
64 list_create(&rc->rc_removed, sizeof (reference_t),
65 offsetof(reference_t, ref_link));
66 rc->rc_count = 0;
67 rc->rc_removed_count = 0;
68 rc->rc_tracked = reference_tracking_enable;
69 }
70
71 void
zfs_refcount_create_tracked(zfs_refcount_t * rc)72 zfs_refcount_create_tracked(zfs_refcount_t *rc)
73 {
74 zfs_refcount_create(rc);
75 rc->rc_tracked = B_TRUE;
76 }
77
78 void
zfs_refcount_create_untracked(zfs_refcount_t * rc)79 zfs_refcount_create_untracked(zfs_refcount_t *rc)
80 {
81 zfs_refcount_create(rc);
82 rc->rc_tracked = B_FALSE;
83 }
84
85 void
zfs_refcount_destroy_many(zfs_refcount_t * rc,uint64_t number)86 zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number)
87 {
88 reference_t *ref;
89
90 ASSERT3U(rc->rc_count, ==, number);
91 while ((ref = list_head(&rc->rc_list))) {
92 list_remove(&rc->rc_list, ref);
93 kmem_cache_free(reference_cache, ref);
94 }
95 list_destroy(&rc->rc_list);
96
97 while ((ref = list_head(&rc->rc_removed))) {
98 list_remove(&rc->rc_removed, ref);
99 kmem_cache_free(reference_history_cache, ref->ref_removed);
100 kmem_cache_free(reference_cache, ref);
101 }
102 list_destroy(&rc->rc_removed);
103 mutex_destroy(&rc->rc_mtx);
104 }
105
106 void
zfs_refcount_destroy(zfs_refcount_t * rc)107 zfs_refcount_destroy(zfs_refcount_t *rc)
108 {
109 zfs_refcount_destroy_many(rc, 0);
110 }
111
112 int
zfs_refcount_is_zero(zfs_refcount_t * rc)113 zfs_refcount_is_zero(zfs_refcount_t *rc)
114 {
115 return (zfs_refcount_count(rc) == 0);
116 }
117
118 int64_t
zfs_refcount_count(zfs_refcount_t * rc)119 zfs_refcount_count(zfs_refcount_t *rc)
120 {
121 return (atomic_load_64(&rc->rc_count));
122 }
123
124 int64_t
zfs_refcount_add_many(zfs_refcount_t * rc,uint64_t number,const void * holder)125 zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder)
126 {
127 reference_t *ref = NULL;
128 int64_t count;
129
130 if (!rc->rc_tracked) {
131 count = atomic_add_64_nv(&(rc)->rc_count, number);
132 ASSERT3U(count, >=, number);
133 return (count);
134 }
135
136 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
137 ref->ref_holder = holder;
138 ref->ref_number = number;
139 mutex_enter(&rc->rc_mtx);
140 ASSERT3U(rc->rc_count, >=, 0);
141 list_insert_head(&rc->rc_list, ref);
142 rc->rc_count += number;
143 count = rc->rc_count;
144 mutex_exit(&rc->rc_mtx);
145
146 return (count);
147 }
148
149 int64_t
zfs_refcount_add(zfs_refcount_t * rc,const void * holder)150 zfs_refcount_add(zfs_refcount_t *rc, const void *holder)
151 {
152 return (zfs_refcount_add_many(rc, 1, holder));
153 }
154
155 int64_t
zfs_refcount_remove_many(zfs_refcount_t * rc,uint64_t number,const void * holder)156 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number,
157 const void *holder)
158 {
159 reference_t *ref;
160 int64_t count;
161
162 if (!rc->rc_tracked) {
163 count = atomic_add_64_nv(&(rc)->rc_count, -number);
164 ASSERT3S(count, >=, 0);
165 return (count);
166 }
167
168 mutex_enter(&rc->rc_mtx);
169 ASSERT3U(rc->rc_count, >=, number);
170 for (ref = list_head(&rc->rc_list); ref;
171 ref = list_next(&rc->rc_list, ref)) {
172 if (ref->ref_holder == holder && ref->ref_number == number) {
173 list_remove(&rc->rc_list, ref);
174 if (reference_history > 0) {
175 ref->ref_removed =
176 kmem_cache_alloc(reference_history_cache,
177 KM_SLEEP);
178 list_insert_head(&rc->rc_removed, ref);
179 rc->rc_removed_count++;
180 if (rc->rc_removed_count > reference_history) {
181 ref = list_tail(&rc->rc_removed);
182 list_remove(&rc->rc_removed, ref);
183 kmem_cache_free(reference_history_cache,
184 ref->ref_removed);
185 kmem_cache_free(reference_cache, ref);
186 rc->rc_removed_count--;
187 }
188 } else {
189 kmem_cache_free(reference_cache, ref);
190 }
191 rc->rc_count -= number;
192 count = rc->rc_count;
193 mutex_exit(&rc->rc_mtx);
194 return (count);
195 }
196 }
197 panic("No such hold %p on refcount %llx", holder,
198 (u_longlong_t)(uintptr_t)rc);
199 return (-1);
200 }
201
202 int64_t
zfs_refcount_remove(zfs_refcount_t * rc,const void * holder)203 zfs_refcount_remove(zfs_refcount_t *rc, const void *holder)
204 {
205 return (zfs_refcount_remove_many(rc, 1, holder));
206 }
207
208 void
zfs_refcount_transfer(zfs_refcount_t * dst,zfs_refcount_t * src)209 zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src)
210 {
211 int64_t count, removed_count;
212 list_t list, removed;
213
214 list_create(&list, sizeof (reference_t),
215 offsetof(reference_t, ref_link));
216 list_create(&removed, sizeof (reference_t),
217 offsetof(reference_t, ref_link));
218
219 mutex_enter(&src->rc_mtx);
220 count = src->rc_count;
221 removed_count = src->rc_removed_count;
222 src->rc_count = 0;
223 src->rc_removed_count = 0;
224 list_move_tail(&list, &src->rc_list);
225 list_move_tail(&removed, &src->rc_removed);
226 mutex_exit(&src->rc_mtx);
227
228 mutex_enter(&dst->rc_mtx);
229 dst->rc_count += count;
230 dst->rc_removed_count += removed_count;
231 list_move_tail(&dst->rc_list, &list);
232 list_move_tail(&dst->rc_removed, &removed);
233 mutex_exit(&dst->rc_mtx);
234
235 list_destroy(&list);
236 list_destroy(&removed);
237 }
238
239 void
zfs_refcount_transfer_ownership_many(zfs_refcount_t * rc,uint64_t number,const void * current_holder,const void * new_holder)240 zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number,
241 const void *current_holder, const void *new_holder)
242 {
243 reference_t *ref;
244 boolean_t found = B_FALSE;
245
246 if (!rc->rc_tracked)
247 return;
248
249 mutex_enter(&rc->rc_mtx);
250 for (ref = list_head(&rc->rc_list); ref;
251 ref = list_next(&rc->rc_list, ref)) {
252 if (ref->ref_holder == current_holder &&
253 ref->ref_number == number) {
254 ref->ref_holder = new_holder;
255 found = B_TRUE;
256 break;
257 }
258 }
259 ASSERT(found);
260 mutex_exit(&rc->rc_mtx);
261 }
262
263 void
zfs_refcount_transfer_ownership(zfs_refcount_t * rc,const void * current_holder,const void * new_holder)264 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder,
265 const void *new_holder)
266 {
267 return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder,
268 new_holder));
269 }
270
271 /*
272 * If tracking is enabled, return true if a reference exists that matches
273 * the "holder" tag. If tracking is disabled, then return true if a reference
274 * might be held.
275 */
276 boolean_t
zfs_refcount_held(zfs_refcount_t * rc,const void * holder)277 zfs_refcount_held(zfs_refcount_t *rc, const void *holder)
278 {
279 reference_t *ref;
280
281 if (!rc->rc_tracked)
282 return (zfs_refcount_count(rc) > 0);
283
284 mutex_enter(&rc->rc_mtx);
285 for (ref = list_head(&rc->rc_list); ref;
286 ref = list_next(&rc->rc_list, ref)) {
287 if (ref->ref_holder == holder) {
288 mutex_exit(&rc->rc_mtx);
289 return (B_TRUE);
290 }
291 }
292 mutex_exit(&rc->rc_mtx);
293 return (B_FALSE);
294 }
295
296 /*
297 * If tracking is enabled, return true if a reference does not exist that
298 * matches the "holder" tag. If tracking is disabled, always return true
299 * since the reference might not be held.
300 */
301 boolean_t
zfs_refcount_not_held(zfs_refcount_t * rc,const void * holder)302 zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder)
303 {
304 reference_t *ref;
305
306 if (!rc->rc_tracked)
307 return (B_TRUE);
308
309 mutex_enter(&rc->rc_mtx);
310 for (ref = list_head(&rc->rc_list); ref;
311 ref = list_next(&rc->rc_list, ref)) {
312 if (ref->ref_holder == holder) {
313 mutex_exit(&rc->rc_mtx);
314 return (B_FALSE);
315 }
316 }
317 mutex_exit(&rc->rc_mtx);
318 return (B_TRUE);
319 }
320
321 EXPORT_SYMBOL(zfs_refcount_create);
322 EXPORT_SYMBOL(zfs_refcount_destroy);
323 EXPORT_SYMBOL(zfs_refcount_is_zero);
324 EXPORT_SYMBOL(zfs_refcount_count);
325 EXPORT_SYMBOL(zfs_refcount_add);
326 EXPORT_SYMBOL(zfs_refcount_remove);
327 EXPORT_SYMBOL(zfs_refcount_held);
328
329 /* BEGIN CSTYLED */
330 ZFS_MODULE_PARAM(zfs, ,reference_tracking_enable, INT, ZMOD_RW,
331 "Track reference holders to refcount_t objects");
332
333 ZFS_MODULE_PARAM(zfs, ,reference_history, INT, ZMOD_RW,
334 "Maximum reference holders being tracked");
335 /* END CSTYLED */
336 #endif /* ZFS_DEBUG */
337