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