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 32int reference_tracking_enable = FALSE; /* runs out of memory too easily */ 33SYSCTL_DECL(_vfs_zfs); 34TUNABLE_INT("vfs.zfs.reference_tracking_enable", &reference_tracking_enable); 35SYSCTL_INT(_vfs_zfs, OID_AUTO, reference_tracking_enable, CTLFLAG_RDTUN, 36 &reference_tracking_enable, 0, 37 "Track reference holders to refcount_t objects, used mostly by ZFS"); 38#else 39int reference_tracking_enable = TRUE; 40#endif 41int reference_history = 3; /* tunable */ 42 43static kmem_cache_t *reference_cache; 44static kmem_cache_t *reference_history_cache; 45 46void 47refcount_sysinit(void) 48{ 49 reference_cache = kmem_cache_create("reference_cache", 50 sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0); 51 52 reference_history_cache = kmem_cache_create("reference_history_cache", 53 sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0); 54} 55 56void 57refcount_fini(void) 58{ 59 kmem_cache_destroy(reference_cache); 60 kmem_cache_destroy(reference_history_cache); 61} 62 63void 64refcount_create(refcount_t *rc) 65{ 66 mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL); 67 list_create(&rc->rc_list, sizeof (reference_t), 68 offsetof(reference_t, ref_link)); 69 list_create(&rc->rc_removed, sizeof (reference_t), 70 offsetof(reference_t, ref_link)); 71 rc->rc_count = 0; 72 rc->rc_removed_count = 0; 73 rc->rc_tracked = reference_tracking_enable; 74} 75 76void 77refcount_create_tracked(refcount_t *rc) 78{ 79 refcount_create(rc); 80 rc->rc_tracked = B_TRUE; 81} 82 83void 84refcount_create_untracked(refcount_t *rc) 85{ 86 refcount_create(rc); 87 rc->rc_tracked = B_FALSE; 88} 89 90void 91refcount_destroy_many(refcount_t *rc, uint64_t number) 92{ 93 reference_t *ref; 94 95 ASSERT(rc->rc_count == number); 96 while (ref = list_head(&rc->rc_list)) { 97 list_remove(&rc->rc_list, ref); 98 kmem_cache_free(reference_cache, ref); 99 } 100 list_destroy(&rc->rc_list); 101 102 while (ref = list_head(&rc->rc_removed)) { 103 list_remove(&rc->rc_removed, ref); 104 kmem_cache_free(reference_history_cache, ref->ref_removed); 105 kmem_cache_free(reference_cache, ref); 106 } 107 list_destroy(&rc->rc_removed); 108 mutex_destroy(&rc->rc_mtx); 109} 110 111void 112refcount_destroy(refcount_t *rc) 113{ 114 refcount_destroy_many(rc, 0); 115} 116 117int 118refcount_is_zero(refcount_t *rc) 119{ 120 return (rc->rc_count == 0); 121} 122 123int64_t 124refcount_count(refcount_t *rc) 125{ 126 return (rc->rc_count); 127} 128 129int64_t 130refcount_add_many(refcount_t *rc, uint64_t number, void *holder) 131{ 132 reference_t *ref = NULL; 133 int64_t count; 134 135 if (rc->rc_tracked) { 136 ref = kmem_cache_alloc(reference_cache, KM_SLEEP); 137 ref->ref_holder = holder; 138 ref->ref_number = number; 139 } 140 mutex_enter(&rc->rc_mtx); 141 ASSERT(rc->rc_count >= 0); 142 if (rc->rc_tracked) 143 list_insert_head(&rc->rc_list, ref); 144 rc->rc_count += number; 145 count = rc->rc_count; 146 mutex_exit(&rc->rc_mtx); 147 148 return (count); 149} 150 151int64_t 152refcount_add(refcount_t *rc, void *holder) 153{ 154 return (refcount_add_many(rc, 1, holder)); 155} 156 157int64_t 158refcount_remove_many(refcount_t *rc, uint64_t number, void *holder) 159{ 160 reference_t *ref; 161 int64_t count; 162 163 mutex_enter(&rc->rc_mtx); 164 ASSERT(rc->rc_count >= number); 165 166 if (!rc->rc_tracked) { 167 rc->rc_count -= number; 168 count = rc->rc_count; 169 mutex_exit(&rc->rc_mtx); 170 return (count); 171 } 172 173 for (ref = list_head(&rc->rc_list); ref; 174 ref = list_next(&rc->rc_list, ref)) { 175 if (ref->ref_holder == holder && ref->ref_number == number) { 176 list_remove(&rc->rc_list, ref); 177 if (reference_history > 0) { 178 ref->ref_removed = 179 kmem_cache_alloc(reference_history_cache, 180 KM_SLEEP); 181 list_insert_head(&rc->rc_removed, ref); 182 rc->rc_removed_count++; 183 if (rc->rc_removed_count > reference_history) { 184 ref = list_tail(&rc->rc_removed); 185 list_remove(&rc->rc_removed, ref); 186 kmem_cache_free(reference_history_cache, 187 ref->ref_removed); 188 kmem_cache_free(reference_cache, ref); 189 rc->rc_removed_count--; 190 } 191 } else { 192 kmem_cache_free(reference_cache, ref); 193 } 194 rc->rc_count -= number; 195 count = rc->rc_count; 196 mutex_exit(&rc->rc_mtx); 197 return (count); 198 } 199 } 200 panic("No such hold %p on refcount %llx", holder, 201 (u_longlong_t)(uintptr_t)rc); 202 return (-1); 203} 204 205int64_t 206refcount_remove(refcount_t *rc, void *holder) 207{ 208 return (refcount_remove_many(rc, 1, holder)); 209} 210 211void 212refcount_transfer(refcount_t *dst, refcount_t *src) 213{ 214 int64_t count, removed_count; 215 list_t list, removed; 216 217 list_create(&list, sizeof (reference_t), 218 offsetof(reference_t, ref_link)); 219 list_create(&removed, sizeof (reference_t), 220 offsetof(reference_t, ref_link)); 221 222 mutex_enter(&src->rc_mtx); 223 count = src->rc_count; 224 removed_count = src->rc_removed_count; 225 src->rc_count = 0; 226 src->rc_removed_count = 0; 227 list_move_tail(&list, &src->rc_list); 228 list_move_tail(&removed, &src->rc_removed); 229 mutex_exit(&src->rc_mtx); 230 231 mutex_enter(&dst->rc_mtx); 232 dst->rc_count += count; 233 dst->rc_removed_count += removed_count; 234 list_move_tail(&dst->rc_list, &list); 235 list_move_tail(&dst->rc_removed, &removed); 236 mutex_exit(&dst->rc_mtx); 237 238 list_destroy(&list); 239 list_destroy(&removed); 240} 241 242void 243refcount_transfer_ownership(refcount_t *rc, void *current_holder, 244 void *new_holder) 245{ 246 reference_t *ref; 247 boolean_t found = B_FALSE; 248 249 mutex_enter(&rc->rc_mtx); 250 if (!rc->rc_tracked) { 251 mutex_exit(&rc->rc_mtx); 252 return; 253 } 254 255 for (ref = list_head(&rc->rc_list); ref; 256 ref = list_next(&rc->rc_list, ref)) { 257 if (ref->ref_holder == current_holder) { 258 ref->ref_holder = new_holder; 259 found = B_TRUE; 260 break; 261 } 262 } 263 ASSERT(found); 264 mutex_exit(&rc->rc_mtx); 265} 266 267/* 268 * If tracking is enabled, return true if a reference exists that matches 269 * the "holder" tag. If tracking is disabled, then return true if a reference 270 * might be held. 271 */ 272boolean_t 273refcount_held(refcount_t *rc, void *holder) 274{ 275 reference_t *ref; 276 277 mutex_enter(&rc->rc_mtx); 278 279 if (!rc->rc_tracked) { 280 mutex_exit(&rc->rc_mtx); 281 return (rc->rc_count > 0); 282 } 283 284 for (ref = list_head(&rc->rc_list); ref; 285 ref = list_next(&rc->rc_list, ref)) { 286 if (ref->ref_holder == holder) { 287 mutex_exit(&rc->rc_mtx); 288 return (B_TRUE); 289 } 290 } 291 mutex_exit(&rc->rc_mtx); 292 return (B_FALSE); 293} 294 295/* 296 * If tracking is enabled, return true if a reference does not exist that 297 * matches the "holder" tag. If tracking is disabled, always return true 298 * since the reference might not be held. 299 */ 300boolean_t 301refcount_not_held(refcount_t *rc, void *holder) 302{ 303 reference_t *ref; 304 305 mutex_enter(&rc->rc_mtx); 306 307 if (!rc->rc_tracked) { 308 mutex_exit(&rc->rc_mtx); 309 return (B_TRUE); 310 } 311 312 for (ref = list_head(&rc->rc_list); ref; 313 ref = list_next(&rc->rc_list, ref)) { 314 if (ref->ref_holder == holder) { 315 mutex_exit(&rc->rc_mtx); 316 return (B_FALSE); 317 } 318 } 319 mutex_exit(&rc->rc_mtx); 320 return (B_TRUE); 321} 322#endif /* ZFS_DEBUG */ 323