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 42 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 52 refcount_fini(void) 53 { 54 kmem_cache_destroy(reference_cache); 55 kmem_cache_destroy(reference_history_cache); 56 } 57 58 void 59 refcount_create(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 72 refcount_create_tracked(refcount_t *rc) 73 { 74 refcount_create(rc); 75 rc->rc_tracked = B_TRUE; 76 } 77 78 void 79 refcount_create_untracked(refcount_t *rc) 80 { 81 refcount_create(rc); 82 rc->rc_tracked = B_FALSE; 83 } 84 85 void 86 refcount_destroy_many(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 107 refcount_destroy(refcount_t *rc) 108 { 109 refcount_destroy_many(rc, 0); 110 } 111 112 int 113 refcount_is_zero(refcount_t *rc) 114 { 115 return (rc->rc_count == 0); 116 } 117 118 int64_t 119 refcount_count(refcount_t *rc) 120 { 121 return (rc->rc_count); 122 } 123 124 int64_t 125 refcount_add_many(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 147 refcount_add(refcount_t *rc, void *holder) 148 { 149 return (refcount_add_many(rc, 1, holder)); 150 } 151 152 int64_t 153 refcount_remove_many(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 201 refcount_remove(refcount_t *rc, void *holder) 202 { 203 return (refcount_remove_many(rc, 1, holder)); 204 } 205 206 void 207 refcount_transfer(refcount_t *dst, 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 void 238 refcount_transfer_ownership(refcount_t *rc, void *current_holder, 239 void *new_holder) 240 { 241 reference_t *ref; 242 boolean_t found = B_FALSE; 243 244 mutex_enter(&rc->rc_mtx); 245 if (!rc->rc_tracked) { 246 mutex_exit(&rc->rc_mtx); 247 return; 248 } 249 250 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_holder = new_holder; 254 found = B_TRUE; 255 break; 256 } 257 } 258 ASSERT(found); 259 mutex_exit(&rc->rc_mtx); 260 } 261 262 /* 263 * If tracking is enabled, return true if a reference exists that matches 264 * the "holder" tag. If tracking is disabled, then return true if a reference 265 * might be held. 266 */ 267 boolean_t 268 refcount_held(refcount_t *rc, void *holder) 269 { 270 reference_t *ref; 271 272 mutex_enter(&rc->rc_mtx); 273 274 if (!rc->rc_tracked) { 275 mutex_exit(&rc->rc_mtx); 276 return (rc->rc_count > 0); 277 } 278 279 for (ref = list_head(&rc->rc_list); ref; 280 ref = list_next(&rc->rc_list, ref)) { 281 if (ref->ref_holder == holder) { 282 mutex_exit(&rc->rc_mtx); 283 return (B_TRUE); 284 } 285 } 286 mutex_exit(&rc->rc_mtx); 287 return (B_FALSE); 288 } 289 290 /* 291 * If tracking is enabled, return true if a reference does not exist that 292 * matches the "holder" tag. If tracking is disabled, always return true 293 * since the reference might not be held. 294 */ 295 boolean_t 296 refcount_not_held(refcount_t *rc, void *holder) 297 { 298 reference_t *ref; 299 300 mutex_enter(&rc->rc_mtx); 301 302 if (!rc->rc_tracked) { 303 mutex_exit(&rc->rc_mtx); 304 return (B_TRUE); 305 } 306 307 for (ref = list_head(&rc->rc_list); ref; 308 ref = list_next(&rc->rc_list, ref)) { 309 if (ref->ref_holder == holder) { 310 mutex_exit(&rc->rc_mtx); 311 return (B_FALSE); 312 } 313 } 314 mutex_exit(&rc->rc_mtx); 315 return (B_TRUE); 316 } 317 #endif /* ZFS_DEBUG */ 318