usr/src/uts/common/fs/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 by Delphix. All rights reserved.
  24  */
  25
  26 #include <sys/zfs_context.h>
  27 #include <sys/refcount.h>
  28
  29 #ifdef  ZFS_DEBUG
  30
  31 #ifdef _KERNEL
  32 int reference_tracking_enable = FALSE; /* runs out of memory too easily */
  33 #else
  34 int reference_tracking_enable = TRUE;
  35 #endif
  36 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 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 refcount_fini(void)
  53 {
  54         kmem_cache_destroy(reference_cache);
  55         kmem_cache_destroy(reference_history_cache);
  56 }
  57
  58 void
  59 refcount_create(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 refcount_create_untracked(refcount_t *rc)
  73 {
  74         refcount_create(rc);
  75         rc->rc_tracked = B_FALSE;
  76 }
  77
  78 void
  79 refcount_destroy_many(refcount_t *rc, uint64_t number)
  80 {
  81         reference_t *ref;
  82
  83         ASSERT(rc->rc_count == number);
  84         while (ref = list_head(&rc->rc_list)) {
  85                 list_remove(&rc->rc_list, ref);
  86                 kmem_cache_free(reference_cache, ref);
  87         }
  88         list_destroy(&rc->rc_list);
  89
  90         while (ref = list_head(&rc->rc_removed)) {
  91                 list_remove(&rc->rc_removed, ref);
  92                 kmem_cache_free(reference_history_cache, ref->ref_removed);
  93                 kmem_cache_free(reference_cache, ref);
  94         }
  95         list_destroy(&rc->rc_removed);
  96         mutex_destroy(&rc->rc_mtx);
  97 }
  98
  99 void
 100 refcount_destroy(refcount_t *rc)
 101 {
 102         refcount_destroy_many(rc, 0);
 103 }
 104
 105 int
 106 refcount_is_zero(refcount_t *rc)
 107 {
 108         return (rc->rc_count == 0);
 109 }
 110
 111 int64_t
 112 refcount_count(refcount_t *rc)
 113 {
 114         return (rc->rc_count);
 115 }
 116
 117 int64_t
 118 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 119 {
 120         reference_t *ref = NULL;
 121         int64_t count;
 122
 123         if (rc->rc_tracked) {
 124                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 125                 ref->ref_holder = holder;
 126                 ref->ref_number = number;
 127         }
 128         mutex_enter(&rc->rc_mtx);
 129         ASSERT(rc->rc_count >= 0);
 130         if (rc->rc_tracked)
 131                 list_insert_head(&rc->rc_list, ref);
 132         rc->rc_count += number;
 133         count = rc->rc_count;
 134         mutex_exit(&rc->rc_mtx);
 135
 136         return (count);
 137 }
 138
 139 int64_t
 140 refcount_add(refcount_t *rc, void *holder)
 141 {
 142         return (refcount_add_many(rc, 1, holder));
 143 }
 144
 145 int64_t
 146 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 147 {
 148         reference_t *ref;
 149         int64_t count;
 150
 151         mutex_enter(&rc->rc_mtx);
 152         ASSERT(rc->rc_count >= number);
 153
 154         if (!rc->rc_tracked) {
 155                 rc->rc_count -= number;
 156                 count = rc->rc_count;
 157                 mutex_exit(&rc->rc_mtx);
 158                 return (count);
 159         }
 160
 161         for (ref = list_head(&rc->rc_list); ref;
 162             ref = list_next(&rc->rc_list, ref)) {
 163                 if (ref->ref_holder == holder && ref->ref_number == number) {
 164                         list_remove(&rc->rc_list, ref);
 165                         if (reference_history > 0) {
 166                                 ref->ref_removed =
 167                                     kmem_cache_alloc(reference_history_cache,
 168                                     KM_SLEEP);
 169                                 list_insert_head(&rc->rc_removed, ref);
 170                                 rc->rc_removed_count++;
 171                                 if (rc->rc_removed_count > reference_history) {
 172                                         ref = list_tail(&rc->rc_removed);
 173                                         list_remove(&rc->rc_removed, ref);
 174                                         kmem_cache_free(reference_history_cache,
 175                                             ref->ref_removed);
 176                                         kmem_cache_free(reference_cache, ref);
 177                                         rc->rc_removed_count--;
 178                                 }
 179                         } else {
 180                                 kmem_cache_free(reference_cache, ref);
 181                         }
 182                         rc->rc_count -= number;
 183                         count = rc->rc_count;
 184                         mutex_exit(&rc->rc_mtx);
 185                         return (count);
 186                 }
 187         }
 188         panic("No such hold %p on refcount %llx", holder,
 189             (u_longlong_t)(uintptr_t)rc);
 190         return (-1);
 191 }
 192
 193 int64_t
 194 refcount_remove(refcount_t *rc, void *holder)
 195 {
 196         return (refcount_remove_many(rc, 1, holder));
 197 }
 198
 199 void
 200 refcount_transfer(refcount_t *dst, refcount_t *src)
 201 {
 202         int64_t count, removed_count;
 203         list_t list, removed;
 204
 205         list_create(&list, sizeof (reference_t),
 206             offsetof(reference_t, ref_link));
 207         list_create(&removed, sizeof (reference_t),
 208             offsetof(reference_t, ref_link));
 209
 210         mutex_enter(&src->rc_mtx);
 211         count = src->rc_count;
 212         removed_count = src->rc_removed_count;
 213         src->rc_count = 0;
 214         src->rc_removed_count = 0;
 215         list_move_tail(&list, &src->rc_list);
 216         list_move_tail(&removed, &src->rc_removed);
 217         mutex_exit(&src->rc_mtx);
 218
 219         mutex_enter(&dst->rc_mtx);
 220         dst->rc_count += count;
 221         dst->rc_removed_count += removed_count;
 222         list_move_tail(&dst->rc_list, &list);
 223         list_move_tail(&dst->rc_removed, &removed);
 224         mutex_exit(&dst->rc_mtx);
 225
 226         list_destroy(&list);
 227         list_destroy(&removed);
 228 }
 229
 230 #endif  /* ZFS_DEBUG */