xref: /illumos-gate/usr/src/uts/common/fs/zfs/refcount.c (revision eb633035)
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 #else
34 int reference_tracking_enable = TRUE;
35 #endif
36 int reference_history = 3; /* tunable */
37 
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 	ASSERT(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 (rc->rc_count == 0);
116 }
117 
118 int64_t
zfs_refcount_count(zfs_refcount_t * rc)119 zfs_refcount_count(zfs_refcount_t *rc)
120 {
121 	return (rc->rc_count);
122 }
123 
124 int64_t
zfs_refcount_add_many(zfs_refcount_t * rc,uint64_t number,void * holder)125 zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, void *holder)
126 {
127 	reference_t *ref = NULL;
128 	int64_t count;
129 
130 	if (rc->rc_tracked) {
131 		ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
132 		ref->ref_holder = holder;
133 		ref->ref_number = number;
134 	}
135 	mutex_enter(&rc->rc_mtx);
136 	ASSERT(rc->rc_count >= 0);
137 	if (rc->rc_tracked)
138 		list_insert_head(&rc->rc_list, ref);
139 	rc->rc_count += number;
140 	count = rc->rc_count;
141 	mutex_exit(&rc->rc_mtx);
142 
143 	return (count);
144 }
145 
146 int64_t
zfs_refcount_add(zfs_refcount_t * rc,void * holder)147 zfs_refcount_add(zfs_refcount_t *rc, void *holder)
148 {
149 	return (zfs_refcount_add_many(rc, 1, holder));
150 }
151 
152 int64_t
zfs_refcount_remove_many(zfs_refcount_t * rc,uint64_t number,void * holder)153 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, void *holder)
154 {
155 	reference_t *ref;
156 	int64_t count;
157 
158 	mutex_enter(&rc->rc_mtx);
159 	ASSERT(rc->rc_count >= number);
160 
161 	if (!rc->rc_tracked) {
162 		rc->rc_count -= number;
163 		count = rc->rc_count;
164 		mutex_exit(&rc->rc_mtx);
165 		return (count);
166 	}
167 
168 	for (ref = list_head(&rc->rc_list); ref;
169 	    ref = list_next(&rc->rc_list, ref)) {
170 		if (ref->ref_holder == holder && ref->ref_number == number) {
171 			list_remove(&rc->rc_list, ref);
172 			if (reference_history > 0) {
173 				ref->ref_removed =
174 				    kmem_cache_alloc(reference_history_cache,
175 				    KM_SLEEP);
176 				list_insert_head(&rc->rc_removed, ref);
177 				rc->rc_removed_count++;
178 				if (rc->rc_removed_count > reference_history) {
179 					ref = list_tail(&rc->rc_removed);
180 					list_remove(&rc->rc_removed, ref);
181 					kmem_cache_free(reference_history_cache,
182 					    ref->ref_removed);
183 					kmem_cache_free(reference_cache, ref);
184 					rc->rc_removed_count--;
185 				}
186 			} else {
187 				kmem_cache_free(reference_cache, ref);
188 			}
189 			rc->rc_count -= number;
190 			count = rc->rc_count;
191 			mutex_exit(&rc->rc_mtx);
192 			return (count);
193 		}
194 	}
195 	panic("No such hold %p on refcount %llx", holder,
196 	    (u_longlong_t)(uintptr_t)rc);
197 	return (-1);
198 }
199 
200 int64_t
zfs_refcount_remove(zfs_refcount_t * rc,void * holder)201 zfs_refcount_remove(zfs_refcount_t *rc, void *holder)
202 {
203 	return (zfs_refcount_remove_many(rc, 1, holder));
204 }
205 
206 void
zfs_refcount_transfer(zfs_refcount_t * dst,zfs_refcount_t * src)207 zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src)
208 {
209 	int64_t count, removed_count;
210 	list_t list, removed;
211 
212 	list_create(&list, sizeof (reference_t),
213 	    offsetof(reference_t, ref_link));
214 	list_create(&removed, sizeof (reference_t),
215 	    offsetof(reference_t, ref_link));
216 
217 	mutex_enter(&src->rc_mtx);
218 	count = src->rc_count;
219 	removed_count = src->rc_removed_count;
220 	src->rc_count = 0;
221 	src->rc_removed_count = 0;
222 	list_move_tail(&list, &src->rc_list);
223 	list_move_tail(&removed, &src->rc_removed);
224 	mutex_exit(&src->rc_mtx);
225 
226 	mutex_enter(&dst->rc_mtx);
227 	dst->rc_count += count;
228 	dst->rc_removed_count += removed_count;
229 	list_move_tail(&dst->rc_list, &list);
230 	list_move_tail(&dst->rc_removed, &removed);
231 	mutex_exit(&dst->rc_mtx);
232 
233 	list_destroy(&list);
234 	list_destroy(&removed);
235 }
236 
237 /* ARGSUSED */
238 void
zfs_refcount_transfer_ownership_many(zfs_refcount_t * rc,uint64_t number,void * current_holder,void * new_holder)239 zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number,
240     void *current_holder, void *new_holder)
241 {
242 	reference_t *ref;
243 	boolean_t found = B_FALSE;
244 
245 	mutex_enter(&rc->rc_mtx);
246 	if (!rc->rc_tracked) {
247 		mutex_exit(&rc->rc_mtx);
248 		return;
249 	}
250 
251 	for (ref = list_head(&rc->rc_list); ref;
252 	    ref = list_next(&rc->rc_list, ref)) {
253 		if (ref->ref_holder == current_holder &&
254 		    ref->ref_number == number) {
255 			ref->ref_holder = new_holder;
256 			found = B_TRUE;
257 			break;
258 		}
259 	}
260 	ASSERT(found);
261 	mutex_exit(&rc->rc_mtx);
262 }
263 
264 void
zfs_refcount_transfer_ownership(zfs_refcount_t * rc,void * current_holder,void * new_holder)265 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, void *current_holder,
266     void *new_holder)
267 {
268 	zfs_refcount_transfer_ownership_many(rc, 1, current_holder,
269 	    new_holder);
270 }
271 
272 /*
273  * If tracking is enabled, return true if a reference exists that matches
274  * the "holder" tag. If tracking is disabled, then return true if a reference
275  * might be held.
276  */
277 boolean_t
zfs_refcount_held(zfs_refcount_t * rc,void * holder)278 zfs_refcount_held(zfs_refcount_t *rc, void *holder)
279 {
280 	reference_t *ref;
281 
282 	mutex_enter(&rc->rc_mtx);
283 
284 	if (!rc->rc_tracked) {
285 		mutex_exit(&rc->rc_mtx);
286 		return (rc->rc_count > 0);
287 	}
288 
289 	for (ref = list_head(&rc->rc_list); ref;
290 	    ref = list_next(&rc->rc_list, ref)) {
291 		if (ref->ref_holder == holder) {
292 			mutex_exit(&rc->rc_mtx);
293 			return (B_TRUE);
294 		}
295 	}
296 	mutex_exit(&rc->rc_mtx);
297 	return (B_FALSE);
298 }
299 
300 /*
301  * If tracking is enabled, return true if a reference does not exist that
302  * matches the "holder" tag. If tracking is disabled, always return true
303  * since the reference might not be held.
304  */
305 boolean_t
zfs_refcount_not_held(zfs_refcount_t * rc,void * holder)306 zfs_refcount_not_held(zfs_refcount_t *rc, void *holder)
307 {
308 	reference_t *ref;
309 
310 	mutex_enter(&rc->rc_mtx);
311 
312 	if (!rc->rc_tracked) {
313 		mutex_exit(&rc->rc_mtx);
314 		return (B_TRUE);
315 	}
316 
317 	for (ref = list_head(&rc->rc_list); ref;
318 	    ref = list_next(&rc->rc_list, ref)) {
319 		if (ref->ref_holder == holder) {
320 			mutex_exit(&rc->rc_mtx);
321 			return (B_FALSE);
322 		}
323 	}
324 	mutex_exit(&rc->rc_mtx);
325 	return (B_TRUE);
326 }
327 #endif	/* ZFS_DEBUG */
328