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 https://opensource.org/licenses/CDDL-1.0. 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 uint_t 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_remove_head(&rc->rc_list))) 92 kmem_cache_free(reference_cache, ref); 93 list_destroy(&rc->rc_list); 94 95 while ((ref = list_remove_head(&rc->rc_removed))) { 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 } 102 103 void 104 zfs_refcount_destroy(zfs_refcount_t *rc) 105 { 106 zfs_refcount_destroy_many(rc, 0); 107 } 108 109 int 110 zfs_refcount_is_zero(zfs_refcount_t *rc) 111 { 112 return (zfs_refcount_count(rc) == 0); 113 } 114 115 int64_t 116 zfs_refcount_count(zfs_refcount_t *rc) 117 { 118 return (atomic_load_64(&rc->rc_count)); 119 } 120 121 int64_t 122 zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder) 123 { 124 reference_t *ref = NULL; 125 int64_t count; 126 127 if (!rc->rc_tracked) { 128 count = atomic_add_64_nv(&(rc)->rc_count, number); 129 ASSERT3U(count, >=, number); 130 return (count); 131 } 132 133 ref = kmem_cache_alloc(reference_cache, KM_SLEEP); 134 ref->ref_holder = holder; 135 ref->ref_number = number; 136 mutex_enter(&rc->rc_mtx); 137 list_insert_head(&rc->rc_list, ref); 138 rc->rc_count += number; 139 count = rc->rc_count; 140 mutex_exit(&rc->rc_mtx); 141 142 return (count); 143 } 144 145 int64_t 146 zfs_refcount_add(zfs_refcount_t *rc, const void *holder) 147 { 148 return (zfs_refcount_add_many(rc, 1, holder)); 149 } 150 151 void 152 zfs_refcount_add_few(zfs_refcount_t *rc, uint64_t number, const void *holder) 153 { 154 if (!rc->rc_tracked) 155 (void) zfs_refcount_add_many(rc, number, holder); 156 else for (; number > 0; number--) 157 (void) zfs_refcount_add(rc, holder); 158 } 159 160 int64_t 161 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, 162 const void *holder) 163 { 164 reference_t *ref; 165 int64_t count; 166 167 if (!rc->rc_tracked) { 168 count = atomic_add_64_nv(&(rc)->rc_count, -number); 169 ASSERT3S(count, >=, 0); 170 return (count); 171 } 172 173 mutex_enter(&rc->rc_mtx); 174 ASSERT3U(rc->rc_count, >=, number); 175 for (ref = list_head(&rc->rc_list); ref; 176 ref = list_next(&rc->rc_list, ref)) { 177 if (ref->ref_holder == holder && ref->ref_number == number) { 178 list_remove(&rc->rc_list, ref); 179 if (reference_history > 0) { 180 ref->ref_removed = 181 kmem_cache_alloc(reference_history_cache, 182 KM_SLEEP); 183 list_insert_head(&rc->rc_removed, ref); 184 rc->rc_removed_count++; 185 if (rc->rc_removed_count > reference_history) { 186 ref = list_tail(&rc->rc_removed); 187 list_remove(&rc->rc_removed, ref); 188 kmem_cache_free(reference_history_cache, 189 ref->ref_removed); 190 kmem_cache_free(reference_cache, ref); 191 rc->rc_removed_count--; 192 } 193 } else { 194 kmem_cache_free(reference_cache, ref); 195 } 196 rc->rc_count -= number; 197 count = rc->rc_count; 198 mutex_exit(&rc->rc_mtx); 199 return (count); 200 } 201 } 202 panic("No such hold %p on refcount %llx", holder, 203 (u_longlong_t)(uintptr_t)rc); 204 return (-1); 205 } 206 207 int64_t 208 zfs_refcount_remove(zfs_refcount_t *rc, const void *holder) 209 { 210 return (zfs_refcount_remove_many(rc, 1, holder)); 211 } 212 213 void 214 zfs_refcount_remove_few(zfs_refcount_t *rc, uint64_t number, const void *holder) 215 { 216 if (!rc->rc_tracked) 217 (void) zfs_refcount_remove_many(rc, number, holder); 218 else for (; number > 0; number--) 219 (void) zfs_refcount_remove(rc, holder); 220 } 221 222 void 223 zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src) 224 { 225 int64_t count, removed_count; 226 list_t list, removed; 227 228 list_create(&list, sizeof (reference_t), 229 offsetof(reference_t, ref_link)); 230 list_create(&removed, sizeof (reference_t), 231 offsetof(reference_t, ref_link)); 232 233 mutex_enter(&src->rc_mtx); 234 count = src->rc_count; 235 removed_count = src->rc_removed_count; 236 src->rc_count = 0; 237 src->rc_removed_count = 0; 238 list_move_tail(&list, &src->rc_list); 239 list_move_tail(&removed, &src->rc_removed); 240 mutex_exit(&src->rc_mtx); 241 242 mutex_enter(&dst->rc_mtx); 243 dst->rc_count += count; 244 dst->rc_removed_count += removed_count; 245 list_move_tail(&dst->rc_list, &list); 246 list_move_tail(&dst->rc_removed, &removed); 247 mutex_exit(&dst->rc_mtx); 248 249 list_destroy(&list); 250 list_destroy(&removed); 251 } 252 253 void 254 zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number, 255 const void *current_holder, const void *new_holder) 256 { 257 reference_t *ref; 258 boolean_t found = B_FALSE; 259 260 if (!rc->rc_tracked) 261 return; 262 263 mutex_enter(&rc->rc_mtx); 264 for (ref = list_head(&rc->rc_list); ref; 265 ref = list_next(&rc->rc_list, ref)) { 266 if (ref->ref_holder == current_holder && 267 ref->ref_number == number) { 268 ref->ref_holder = new_holder; 269 found = B_TRUE; 270 break; 271 } 272 } 273 ASSERT(found); 274 mutex_exit(&rc->rc_mtx); 275 } 276 277 void 278 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder, 279 const void *new_holder) 280 { 281 return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, 282 new_holder)); 283 } 284 285 /* 286 * If tracking is enabled, return true if a reference exists that matches 287 * the "holder" tag. If tracking is disabled, then return true if a reference 288 * might be held. 289 */ 290 boolean_t 291 zfs_refcount_held(zfs_refcount_t *rc, const void *holder) 292 { 293 reference_t *ref; 294 295 if (!rc->rc_tracked) 296 return (zfs_refcount_count(rc) > 0); 297 298 mutex_enter(&rc->rc_mtx); 299 for (ref = list_head(&rc->rc_list); ref; 300 ref = list_next(&rc->rc_list, ref)) { 301 if (ref->ref_holder == holder) { 302 mutex_exit(&rc->rc_mtx); 303 return (B_TRUE); 304 } 305 } 306 mutex_exit(&rc->rc_mtx); 307 return (B_FALSE); 308 } 309 310 /* 311 * If tracking is enabled, return true if a reference does not exist that 312 * matches the "holder" tag. If tracking is disabled, always return true 313 * since the reference might not be held. 314 */ 315 boolean_t 316 zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder) 317 { 318 reference_t *ref; 319 320 if (!rc->rc_tracked) 321 return (B_TRUE); 322 323 mutex_enter(&rc->rc_mtx); 324 for (ref = list_head(&rc->rc_list); ref; 325 ref = list_next(&rc->rc_list, ref)) { 326 if (ref->ref_holder == holder) { 327 mutex_exit(&rc->rc_mtx); 328 return (B_FALSE); 329 } 330 } 331 mutex_exit(&rc->rc_mtx); 332 return (B_TRUE); 333 } 334 335 EXPORT_SYMBOL(zfs_refcount_create); 336 EXPORT_SYMBOL(zfs_refcount_destroy); 337 EXPORT_SYMBOL(zfs_refcount_is_zero); 338 EXPORT_SYMBOL(zfs_refcount_count); 339 EXPORT_SYMBOL(zfs_refcount_add); 340 EXPORT_SYMBOL(zfs_refcount_remove); 341 EXPORT_SYMBOL(zfs_refcount_held); 342 343 /* BEGIN CSTYLED */ 344 ZFS_MODULE_PARAM(zfs, , reference_tracking_enable, INT, ZMOD_RW, 345 "Track reference holders to refcount_t objects"); 346 347 ZFS_MODULE_PARAM(zfs, , reference_history, UINT, ZMOD_RW, 348 "Maximum reference holders being tracked"); 349 /* END CSTYLED */ 350 #endif /* ZFS_DEBUG */ 351