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 /* 30 * Reference count tracking is disabled by default. It's memory requirements 31 * are reasonable, however as implemented it consumes a significant amount of 32 * cpu time. Until its performance is improved it should be manually enabled. 33 */ 34 int reference_tracking_enable = FALSE; 35 int reference_history = 3; /* tunable */ 36 37 #ifdef ZFS_DEBUG 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 (rc->rc_count == 0); 116 } 117 118 int64_t 119 zfs_refcount_count(zfs_refcount_t *rc) 120 { 121 return (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 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 ASSERT3U(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 zfs_refcount_add(zfs_refcount_t *rc, const void *holder) 148 { 149 return (zfs_refcount_add_many(rc, 1, holder)); 150 } 151 152 int64_t 153 zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, 154 const void *holder) 155 { 156 reference_t *ref; 157 int64_t count; 158 159 mutex_enter(&rc->rc_mtx); 160 ASSERT3U(rc->rc_count, >=, number); 161 162 if (!rc->rc_tracked) { 163 rc->rc_count -= number; 164 count = rc->rc_count; 165 mutex_exit(&rc->rc_mtx); 166 return (count); 167 } 168 169 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 mutex_enter(&rc->rc_mtx); 246 if (!rc->rc_tracked) { 247 mutex_exit(&rc->rc_mtx); 248 return; 249 } 250 251 for (ref = list_head(&rc->rc_list); ref; 252 ref = list_next(&rc->rc_list, ref)) { 253 if (ref->ref_holder == current_holder && 254 ref->ref_number == number) { 255 ref->ref_holder = new_holder; 256 found = B_TRUE; 257 break; 258 } 259 } 260 ASSERT(found); 261 mutex_exit(&rc->rc_mtx); 262 } 263 264 void 265 zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder, 266 const void *new_holder) 267 { 268 return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, 269 new_holder)); 270 } 271 272 /* 273 * If tracking is enabled, return true if a reference exists that matches 274 * the "holder" tag. If tracking is disabled, then return true if a reference 275 * might be held. 276 */ 277 boolean_t 278 zfs_refcount_held(zfs_refcount_t *rc, const void *holder) 279 { 280 reference_t *ref; 281 282 mutex_enter(&rc->rc_mtx); 283 284 if (!rc->rc_tracked) { 285 mutex_exit(&rc->rc_mtx); 286 return (rc->rc_count > 0); 287 } 288 289 for (ref = list_head(&rc->rc_list); ref; 290 ref = list_next(&rc->rc_list, ref)) { 291 if (ref->ref_holder == holder) { 292 mutex_exit(&rc->rc_mtx); 293 return (B_TRUE); 294 } 295 } 296 mutex_exit(&rc->rc_mtx); 297 return (B_FALSE); 298 } 299 300 /* 301 * If tracking is enabled, return true if a reference does not exist that 302 * matches the "holder" tag. If tracking is disabled, always return true 303 * since the reference might not be held. 304 */ 305 boolean_t 306 zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder) 307 { 308 reference_t *ref; 309 310 mutex_enter(&rc->rc_mtx); 311 312 if (!rc->rc_tracked) { 313 mutex_exit(&rc->rc_mtx); 314 return (B_TRUE); 315 } 316 317 for (ref = list_head(&rc->rc_list); ref; 318 ref = list_next(&rc->rc_list, ref)) { 319 if (ref->ref_holder == holder) { 320 mutex_exit(&rc->rc_mtx); 321 return (B_FALSE); 322 } 323 } 324 mutex_exit(&rc->rc_mtx); 325 return (B_TRUE); 326 } 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, INT, ZMOD_RW, 333 "Maximum reference holders being tracked"); 334 /* END CSTYLED */ 335 #endif /* ZFS_DEBUG */ 336