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, 2021 by Delphix. All rights reserved. 24 */ 25 26 #include <sys/zfs_context.h> 27 #include <sys/zfs_refcount.h> 28 29 #ifdef ZFS_DEBUG 30 /* 31 * Reference count tracking is disabled by default. It's memory requirements 32 * are reasonable, however as implemented it consumes a significant amount of 33 * cpu time. Until its performance is improved it should be manually enabled. 34 */ 35 int reference_tracking_enable = B_FALSE; 36 static 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 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 52 zfs_refcount_fini(void) 53 { 54 kmem_cache_destroy(reference_cache); 55 kmem_cache_destroy(reference_history_cache); 56 } 57 58 void 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 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 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 86 zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number) 87 { 88 reference_t *ref; 89 90 ASSERT3U(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 zfs_refcount_destroy(zfs_refcount_t *rc) 108 { 109 zfs_refcount_destroy_many(rc, 0); 110 } 111 112 int 113 zfs_refcount_is_zero(zfs_refcount_t *rc) 114 { 115 return (zfs_refcount_count(rc) == 0); 116 } 117 118 int64_t 119 zfs_refcount_count(zfs_refcount_t *rc) 120 { 121 return (atomic_load_64(&rc->rc_count)); 122 } 123 124 int64_t 125 zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder) 126 { 127 reference_t *ref = NULL; 128 int64_t count; 129 130 if (!rc->rc_tracked) { 131 count = atomic_add_64_nv(&(rc)->rc_count, number); 132 ASSERT3U(count, >=, number); 133 return (count); 134 } 135 136 ref = kmem_cache_alloc(reference_cache, KM_SLEEP); 137 ref->ref_holder = holder; 138 ref->ref_number = number; 139 mutex_enter(&rc->rc_mtx); 140 ASSERT3U(rc->rc_count, >=, 0); 141 list_insert_head(&rc->rc_list, ref); 142 rc->rc_count += number; 143 count = rc->rc_count; 144 mutex_exit(&rc->rc_mtx); 145 146 return (count); 147 } 148 149 int64_t 150 zfs_refcount_add(zfs_refcount_t *rc, const void *holder) 151 { 152 return (zfs_refcount_add_many(rc, 1, holder)); 153 } 154 155 int64_t 156 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, 157 const void *holder) 158 { 159 reference_t *ref; 160 int64_t count; 161 162 if (!rc->rc_tracked) { 163 count = atomic_add_64_nv(&(rc)->rc_count, -number); 164 ASSERT3S(count, >=, 0); 165 return (count); 166 } 167 168 mutex_enter(&rc->rc_mtx); 169 ASSERT3U(rc->rc_count, >=, number); 170 for (ref = list_head(&rc->rc_list); ref; 171 ref = list_next(&rc->rc_list, ref)) { 172 if (ref->ref_holder == holder && ref->ref_number == number) { 173 list_remove(&rc->rc_list, ref); 174 if (reference_history > 0) { 175 ref->ref_removed = 176 kmem_cache_alloc(reference_history_cache, 177 KM_SLEEP); 178 list_insert_head(&rc->rc_removed, ref); 179 rc->rc_removed_count++; 180 if (rc->rc_removed_count > reference_history) { 181 ref = list_tail(&rc->rc_removed); 182 list_remove(&rc->rc_removed, ref); 183 kmem_cache_free(reference_history_cache, 184 ref->ref_removed); 185 kmem_cache_free(reference_cache, ref); 186 rc->rc_removed_count--; 187 } 188 } else { 189 kmem_cache_free(reference_cache, ref); 190 } 191 rc->rc_count -= number; 192 count = rc->rc_count; 193 mutex_exit(&rc->rc_mtx); 194 return (count); 195 } 196 } 197 panic("No such hold %p on refcount %llx", holder, 198 (u_longlong_t)(uintptr_t)rc); 199 return (-1); 200 } 201 202 int64_t 203 zfs_refcount_remove(zfs_refcount_t *rc, const void *holder) 204 { 205 return (zfs_refcount_remove_many(rc, 1, holder)); 206 } 207 208 void 209 zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src) 210 { 211 int64_t count, removed_count; 212 list_t list, removed; 213 214 list_create(&list, sizeof (reference_t), 215 offsetof(reference_t, ref_link)); 216 list_create(&removed, sizeof (reference_t), 217 offsetof(reference_t, ref_link)); 218 219 mutex_enter(&src->rc_mtx); 220 count = src->rc_count; 221 removed_count = src->rc_removed_count; 222 src->rc_count = 0; 223 src->rc_removed_count = 0; 224 list_move_tail(&list, &src->rc_list); 225 list_move_tail(&removed, &src->rc_removed); 226 mutex_exit(&src->rc_mtx); 227 228 mutex_enter(&dst->rc_mtx); 229 dst->rc_count += count; 230 dst->rc_removed_count += removed_count; 231 list_move_tail(&dst->rc_list, &list); 232 list_move_tail(&dst->rc_removed, &removed); 233 mutex_exit(&dst->rc_mtx); 234 235 list_destroy(&list); 236 list_destroy(&removed); 237 } 238 239 void 240 zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number, 241 const void *current_holder, const void *new_holder) 242 { 243 reference_t *ref; 244 boolean_t found = B_FALSE; 245 246 if (!rc->rc_tracked) 247 return; 248 249 mutex_enter(&rc->rc_mtx); 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_number == number) { 254 ref->ref_holder = new_holder; 255 found = B_TRUE; 256 break; 257 } 258 } 259 ASSERT(found); 260 mutex_exit(&rc->rc_mtx); 261 } 262 263 void 264 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder, 265 const void *new_holder) 266 { 267 return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, 268 new_holder)); 269 } 270 271 /* 272 * If tracking is enabled, return true if a reference exists that matches 273 * the "holder" tag. If tracking is disabled, then return true if a reference 274 * might be held. 275 */ 276 boolean_t 277 zfs_refcount_held(zfs_refcount_t *rc, const void *holder) 278 { 279 reference_t *ref; 280 281 if (!rc->rc_tracked) 282 return (zfs_refcount_count(rc) > 0); 283 284 mutex_enter(&rc->rc_mtx); 285 for (ref = list_head(&rc->rc_list); ref; 286 ref = list_next(&rc->rc_list, ref)) { 287 if (ref->ref_holder == holder) { 288 mutex_exit(&rc->rc_mtx); 289 return (B_TRUE); 290 } 291 } 292 mutex_exit(&rc->rc_mtx); 293 return (B_FALSE); 294 } 295 296 /* 297 * If tracking is enabled, return true if a reference does not exist that 298 * matches the "holder" tag. If tracking is disabled, always return true 299 * since the reference might not be held. 300 */ 301 boolean_t 302 zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder) 303 { 304 reference_t *ref; 305 306 if (!rc->rc_tracked) 307 return (B_TRUE); 308 309 mutex_enter(&rc->rc_mtx); 310 for (ref = list_head(&rc->rc_list); ref; 311 ref = list_next(&rc->rc_list, ref)) { 312 if (ref->ref_holder == holder) { 313 mutex_exit(&rc->rc_mtx); 314 return (B_FALSE); 315 } 316 } 317 mutex_exit(&rc->rc_mtx); 318 return (B_TRUE); 319 } 320 321 EXPORT_SYMBOL(zfs_refcount_create); 322 EXPORT_SYMBOL(zfs_refcount_destroy); 323 EXPORT_SYMBOL(zfs_refcount_is_zero); 324 EXPORT_SYMBOL(zfs_refcount_count); 325 EXPORT_SYMBOL(zfs_refcount_add); 326 EXPORT_SYMBOL(zfs_refcount_remove); 327 EXPORT_SYMBOL(zfs_refcount_held); 328 329 /* BEGIN CSTYLED */ 330 ZFS_MODULE_PARAM(zfs, , reference_tracking_enable, INT, ZMOD_RW, 331 "Track reference holders to refcount_t objects"); 332 333 ZFS_MODULE_PARAM(zfs, , reference_history, INT, ZMOD_RW, 334 "Maximum reference holders being tracked"); 335 /* END CSTYLED */ 336 #endif /* ZFS_DEBUG */ 337