module/zfs/refcount.c

   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 _KERNEL
  30 int reference_tracking_enable = FALSE; /* runs out of memory too easily */
  31 #else
  32 int reference_tracking_enable = TRUE;
  33 #endif
  34 int reference_history = 3; /* tunable */
  35
  36 #ifdef  ZFS_DEBUG
  37 static kmem_cache_t *reference_cache;
  38 static kmem_cache_t *reference_history_cache;
  39
  40 void
  41 refcount_init(void)
  42 {
  43         reference_cache = kmem_cache_create("reference_cache",
  44             sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  45
  46         reference_history_cache = kmem_cache_create("reference_history_cache",
  47             sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  48 }
  49
  50 void
  51 refcount_fini(void)
  52 {
  53         kmem_cache_destroy(reference_cache);
  54         kmem_cache_destroy(reference_history_cache);
  55 }
  56
  57 void
  58 refcount_create(refcount_t *rc)
  59 {
  60         mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
  61         list_create(&rc->rc_list, sizeof (reference_t),
  62             offsetof(reference_t, ref_link));
  63         list_create(&rc->rc_removed, sizeof (reference_t),
  64             offsetof(reference_t, ref_link));
  65         rc->rc_count = 0;
  66         rc->rc_removed_count = 0;
  67         rc->rc_tracked = reference_tracking_enable;
  68 }
  69
  70 void
  71 refcount_create_tracked(refcount_t *rc)
  72 {
  73         refcount_create(rc);
  74         rc->rc_tracked = B_TRUE;
  75 }
  76
  77 void
  78 refcount_create_untracked(refcount_t *rc)
  79 {
  80         refcount_create(rc);
  81         rc->rc_tracked = B_FALSE;
  82 }
  83
  84 void
  85 refcount_destroy_many(refcount_t *rc, uint64_t number)
  86 {
  87         reference_t *ref;
  88
  89         ASSERT(rc->rc_count == number);
  90         while ((ref = list_head(&rc->rc_list))) {
  91                 list_remove(&rc->rc_list, ref);
  92                 kmem_cache_free(reference_cache, ref);
  93         }
  94         list_destroy(&rc->rc_list);
  95
  96         while ((ref = list_head(&rc->rc_removed))) {
  97                 list_remove(&rc->rc_removed, ref);
  98                 kmem_cache_free(reference_history_cache, ref->ref_removed);
  99                 kmem_cache_free(reference_cache, ref);
 100         }
 101         list_destroy(&rc->rc_removed);
 102         mutex_destroy(&rc->rc_mtx);
 103 }
 104
 105 void
 106 refcount_destroy(refcount_t *rc)
 107 {
 108         refcount_destroy_many(rc, 0);
 109 }
 110
 111 int
 112 refcount_is_zero(refcount_t *rc)
 113 {
 114         return (rc->rc_count == 0);
 115 }
 116
 117 int64_t
 118 refcount_count(refcount_t *rc)
 119 {
 120         return (rc->rc_count);
 121 }
 122
 123 int64_t
 124 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 125 {
 126         reference_t *ref = NULL;
 127         int64_t count;
 128
 129         if (rc->rc_tracked) {
 130                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 131                 ref->ref_holder = holder;
 132                 ref->ref_number = number;
 133         }
 134         mutex_enter(&rc->rc_mtx);
 135         ASSERT(rc->rc_count >= 0);
 136         if (rc->rc_tracked)
 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(refcount_t *rc, void *holder)
 147 {
 148         return (refcount_add_many(rc, 1, holder));
 149 }
 150
 151 int64_t
 152 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 153 {
 154         reference_t *ref;
 155         int64_t count;
 156
 157         mutex_enter(&rc->rc_mtx);
 158         ASSERT(rc->rc_count >= number);
 159
 160         if (!rc->rc_tracked) {
 161                 rc->rc_count -= number;
 162                 count = rc->rc_count;
 163                 mutex_exit(&rc->rc_mtx);
 164                 return (count);
 165         }
 166
 167         for (ref = list_head(&rc->rc_list); ref;
 168             ref = list_next(&rc->rc_list, ref)) {
 169                 if (ref->ref_holder == holder && ref->ref_number == number) {
 170                         list_remove(&rc->rc_list, ref);
 171                         if (reference_history > 0) {
 172                                 ref->ref_removed =
 173                                     kmem_cache_alloc(reference_history_cache,
 174                                     KM_SLEEP);
 175                                 list_insert_head(&rc->rc_removed, ref);
 176                                 rc->rc_removed_count++;
 177                                 if (rc->rc_removed_count > reference_history) {
 178                                         ref = list_tail(&rc->rc_removed);
 179                                         list_remove(&rc->rc_removed, ref);
 180                                         kmem_cache_free(reference_history_cache,
 181                                             ref->ref_removed);
 182                                         kmem_cache_free(reference_cache, ref);
 183                                         rc->rc_removed_count--;
 184                                 }
 185                         } else {
 186                                 kmem_cache_free(reference_cache, ref);
 187                         }
 188                         rc->rc_count -= number;
 189                         count = rc->rc_count;
 190                         mutex_exit(&rc->rc_mtx);
 191                         return (count);
 192                 }
 193         }
 194         panic("No such hold %p on refcount %llx", holder,
 195             (u_longlong_t)(uintptr_t)rc);
 196         return (-1);
 197 }
 198
 199 int64_t
 200 refcount_remove(refcount_t *rc, void *holder)
 201 {
 202         return (refcount_remove_many(rc, 1, holder));
 203 }
 204
 205 void
 206 refcount_transfer(refcount_t *dst, refcount_t *src)
 207 {
 208         int64_t count, removed_count;
 209         list_t list, removed;
 210
 211         list_create(&list, sizeof (reference_t),
 212             offsetof(reference_t, ref_link));
 213         list_create(&removed, sizeof (reference_t),
 214             offsetof(reference_t, ref_link));
 215
 216         mutex_enter(&src->rc_mtx);
 217         count = src->rc_count;
 218         removed_count = src->rc_removed_count;
 219         src->rc_count = 0;
 220         src->rc_removed_count = 0;
 221         list_move_tail(&list, &src->rc_list);
 222         list_move_tail(&removed, &src->rc_removed);
 223         mutex_exit(&src->rc_mtx);
 224
 225         mutex_enter(&dst->rc_mtx);
 226         dst->rc_count += count;
 227         dst->rc_removed_count += removed_count;
 228         list_move_tail(&dst->rc_list, &list);
 229         list_move_tail(&dst->rc_removed, &removed);
 230         mutex_exit(&dst->rc_mtx);
 231
 232         list_destroy(&list);
 233         list_destroy(&removed);
 234 }
 235
 236 void
 237 refcount_transfer_ownership(refcount_t *rc, void *current_holder,
 238     void *new_holder)
 239 {
 240         reference_t *ref;
 241         boolean_t found = B_FALSE;
 242
 243         mutex_enter(&rc->rc_mtx);
 244         if (!rc->rc_tracked) {
 245                 mutex_exit(&rc->rc_mtx);
 246                 return;
 247         }
 248
 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_holder = new_holder;
 253                         found = B_TRUE;
 254                         break;
 255                 }
 256         }
 257         ASSERT(found);
 258         mutex_exit(&rc->rc_mtx);
 259 }
 260
 261 /*
 262  * If tracking is enabled, return true if a reference exists that matches
 263  * the "holder" tag. If tracking is disabled, then return true if a reference
 264  * might be held.
 265  */
 266 boolean_t
 267 refcount_held(refcount_t *rc, void *holder)
 268 {
 269         reference_t *ref;
 270
 271         mutex_enter(&rc->rc_mtx);
 272
 273         if (!rc->rc_tracked) {
 274                 mutex_exit(&rc->rc_mtx);
 275                 return (rc->rc_count > 0);
 276         }
 277
 278         for (ref = list_head(&rc->rc_list); ref;
 279             ref = list_next(&rc->rc_list, ref)) {
 280                 if (ref->ref_holder == holder) {
 281                         mutex_exit(&rc->rc_mtx);
 282                         return (B_TRUE);
 283                 }
 284         }
 285         mutex_exit(&rc->rc_mtx);
 286         return (B_FALSE);
 287 }
 288
 289 /*
 290  * If tracking is enabled, return true if a reference does not exist that
 291  * matches the "holder" tag. If tracking is disabled, always return true
 292  * since the reference might not be held.
 293  */
 294 boolean_t
 295 refcount_not_held(refcount_t *rc, void *holder)
 296 {
 297         reference_t *ref;
 298
 299         mutex_enter(&rc->rc_mtx);
 300
 301         if (!rc->rc_tracked) {
 302                 mutex_exit(&rc->rc_mtx);
 303                 return (B_TRUE);
 304         }
 305
 306         for (ref = list_head(&rc->rc_list); ref;
 307             ref = list_next(&rc->rc_list, ref)) {
 308                 if (ref->ref_holder == holder) {
 309                         mutex_exit(&rc->rc_mtx);
 310                         return (B_FALSE);
 311                 }
 312         }
 313         mutex_exit(&rc->rc_mtx);
 314         return (B_TRUE);
 315 }
 316 #endif  /* ZFS_DEBUG */