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_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 list_insert_head(&rc->rc_list, ref); 141 rc->rc_count += number; 142 count = rc->rc_count; 143 mutex_exit(&rc->rc_mtx); 144 145 return (count); 146 } 147 148 int64_t 149 zfs_refcount_add(zfs_refcount_t *rc, const void *holder) 150 { 151 return (zfs_refcount_add_many(rc, 1, holder)); 152 } 153 154 int64_t 155 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, 156 const void *holder) 157 { 158 reference_t *ref; 159 int64_t count; 160 161 if (!rc->rc_tracked) { 162 count = atomic_add_64_nv(&(rc)->rc_count, -number); 163 ASSERT3S(count, >=, 0); 164 return (count); 165 } 166 167 mutex_enter(&rc->rc_mtx); 168 ASSERT3U(rc->rc_count, >=, number); 169 for (ref = list_head(&rc->rc_list); ref; 170 ref = list_next(&rc->rc_list, ref)) { 171 if (ref->ref_holder == holder && ref->ref_number == number) { 172 list_remove(&rc->rc_list, ref); 173 if (reference_history > 0) { 174 ref->ref_removed = 175 kmem_cache_alloc(reference_history_cache, 176 KM_SLEEP); 177 list_insert_head(&rc->rc_removed, ref); 178 rc->rc_removed_count++; 179 if (rc->rc_removed_count > reference_history) { 180 ref = list_tail(&rc->rc_removed); 181 list_remove(&rc->rc_removed, ref); 182 kmem_cache_free(reference_history_cache, 183 ref->ref_removed); 184 kmem_cache_free(reference_cache, ref); 185 rc->rc_removed_count--; 186 } 187 } else { 188 kmem_cache_free(reference_cache, ref); 189 } 190 rc->rc_count -= number; 191 count = rc->rc_count; 192 mutex_exit(&rc->rc_mtx); 193 return (count); 194 } 195 } 196 panic("No such hold %p on refcount %llx", holder, 197 (u_longlong_t)(uintptr_t)rc); 198 return (-1); 199 } 200 201 int64_t 202 zfs_refcount_remove(zfs_refcount_t *rc, const void *holder) 203 { 204 return (zfs_refcount_remove_many(rc, 1, holder)); 205 } 206 207 void 208 zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src) 209 { 210 int64_t count, removed_count; 211 list_t list, removed; 212 213 list_create(&list, sizeof (reference_t), 214 offsetof(reference_t, ref_link)); 215 list_create(&removed, sizeof (reference_t), 216 offsetof(reference_t, ref_link)); 217 218 mutex_enter(&src->rc_mtx); 219 count = src->rc_count; 220 removed_count = src->rc_removed_count; 221 src->rc_count = 0; 222 src->rc_removed_count = 0; 223 list_move_tail(&list, &src->rc_list); 224 list_move_tail(&removed, &src->rc_removed); 225 mutex_exit(&src->rc_mtx); 226 227 mutex_enter(&dst->rc_mtx); 228 dst->rc_count += count; 229 dst->rc_removed_count += removed_count; 230 list_move_tail(&dst->rc_list, &list); 231 list_move_tail(&dst->rc_removed, &removed); 232 mutex_exit(&dst->rc_mtx); 233 234 list_destroy(&list); 235 list_destroy(&removed); 236 } 237 238 void 239 zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number, 240 const void *current_holder, const void *new_holder) 241 { 242 reference_t *ref; 243 boolean_t found = B_FALSE; 244 245 if (!rc->rc_tracked) 246 return; 247 248 mutex_enter(&rc->rc_mtx); 249 for (ref = list_head(&rc->rc_list); ref; 250 ref = list_next(&rc->rc_list, ref)) { 251 if (ref->ref_holder == current_holder && 252 ref->ref_number == number) { 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 void 263 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder, 264 const void *new_holder) 265 { 266 return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, 267 new_holder)); 268 } 269 270 /* 271 * If tracking is enabled, return true if a reference exists that matches 272 * the "holder" tag. If tracking is disabled, then return true if a reference 273 * might be held. 274 */ 275 boolean_t 276 zfs_refcount_held(zfs_refcount_t *rc, const void *holder) 277 { 278 reference_t *ref; 279 280 if (!rc->rc_tracked) 281 return (zfs_refcount_count(rc) > 0); 282 283 mutex_enter(&rc->rc_mtx); 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 */ 300 boolean_t 301 zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder) 302 { 303 reference_t *ref; 304 305 if (!rc->rc_tracked) 306 return (B_TRUE); 307 308 mutex_enter(&rc->rc_mtx); 309 for (ref = list_head(&rc->rc_list); ref; 310 ref = list_next(&rc->rc_list, ref)) { 311 if (ref->ref_holder == holder) { 312 mutex_exit(&rc->rc_mtx); 313 return (B_FALSE); 314 } 315 } 316 mutex_exit(&rc->rc_mtx); 317 return (B_TRUE); 318 } 319 320 EXPORT_SYMBOL(zfs_refcount_create); 321 EXPORT_SYMBOL(zfs_refcount_destroy); 322 EXPORT_SYMBOL(zfs_refcount_is_zero); 323 EXPORT_SYMBOL(zfs_refcount_count); 324 EXPORT_SYMBOL(zfs_refcount_add); 325 EXPORT_SYMBOL(zfs_refcount_remove); 326 EXPORT_SYMBOL(zfs_refcount_held); 327 328 /* BEGIN CSTYLED */ 329 ZFS_MODULE_PARAM(zfs, , reference_tracking_enable, INT, ZMOD_RW, 330 "Track reference holders to refcount_t objects"); 331 332 ZFS_MODULE_PARAM(zfs, , reference_history, UINT, ZMOD_RW, 333 "Maximum reference holders being tracked"); 334 /* END CSTYLED */ 335 #endif /* ZFS_DEBUG */ 336