refcount.c revision 302408
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 32int reference_tracking_enable = FALSE; /* runs out of memory too easily */ 33SYSCTL_DECL(_vfs_zfs); 34SYSCTL_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 38int reference_tracking_enable = TRUE; 39#endif 40int reference_history = 3; /* tunable */ 41 42static kmem_cache_t *reference_cache; 43static kmem_cache_t *reference_history_cache; 44 45void 46refcount_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 55void 56refcount_fini(void) 57{ 58 kmem_cache_destroy(reference_cache); 59 kmem_cache_destroy(reference_history_cache); 60} 61 62void 63refcount_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 75void 76refcount_create_untracked(refcount_t *rc) 77{ 78 refcount_create(rc); 79 rc->rc_tracked = B_FALSE; 80} 81 82void 83refcount_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 103void 104refcount_destroy(refcount_t *rc) 105{ 106 refcount_destroy_many(rc, 0); 107} 108 109int 110refcount_is_zero(refcount_t *rc) 111{ 112 return (rc->rc_count == 0); 113} 114 115int64_t 116refcount_count(refcount_t *rc) 117{ 118 return (rc->rc_count); 119} 120 121int64_t 122refcount_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 143int64_t 144refcount_add(refcount_t *rc, void *holder) 145{ 146 return (refcount_add_many(rc, 1, holder)); 147} 148 149int64_t 150refcount_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 197int64_t 198refcount_remove(refcount_t *rc, void *holder) 199{ 200 return (refcount_remove_many(rc, 1, holder)); 201} 202 203void 204refcount_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