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  */
  24
  25 #include <sys/zfs_context.h>
  26 #include <sys/refcount.h>
  27
  28 #ifdef  ZFS_DEBUG
  29
  30 #ifdef _KERNEL
  31 int reference_tracking_enable = FALSE; /* runs out of memory too easily */
  32 #else
  33 int reference_tracking_enable = TRUE;
  34 #endif
  35 int reference_history = 4; /* tunable */
  36
  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 }
  68
  69 void
  70 refcount_destroy_many(refcount_t *rc, uint64_t number)
  71 {
  72         reference_t *ref;
  73
  74         ASSERT(rc->rc_count == number);
  75         while (ref = list_head(&rc->rc_list)) {
  76                 list_remove(&rc->rc_list, ref);
  77                 kmem_cache_free(reference_cache, ref);
  78         }
  79         list_destroy(&rc->rc_list);
  80
  81         while (ref = list_head(&rc->rc_removed)) {
  82                 list_remove(&rc->rc_removed, ref);
  83                 kmem_cache_free(reference_history_cache, ref->ref_removed);
  84                 kmem_cache_free(reference_cache, ref);
  85         }
  86         list_destroy(&rc->rc_removed);
  87         mutex_destroy(&rc->rc_mtx);
  88 }
  89
  90 void
  91 refcount_destroy(refcount_t *rc)
  92 {
  93         refcount_destroy_many(rc, 0);
  94 }
  95
  96 int
  97 refcount_is_zero(refcount_t *rc)
  98 {
  99         ASSERT(rc->rc_count >= 0);
 100         return (rc->rc_count == 0);
 101 }
 102
 103 int64_t
 104 refcount_count(refcount_t *rc)
 105 {
 106         ASSERT(rc->rc_count >= 0);
 107         return (rc->rc_count);
 108 }
 109
 110 int64_t
 111 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 112 {
 113         reference_t *ref;
 114         int64_t count;
 115
 116         if (reference_tracking_enable) {
 117                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 118                 ref->ref_holder = holder;
 119                 ref->ref_number = number;
 120         }
 121         mutex_enter(&rc->rc_mtx);
 122         ASSERT(rc->rc_count >= 0);
 123         if (reference_tracking_enable)
 124                 list_insert_head(&rc->rc_list, ref);
 125         rc->rc_count += number;
 126         count = rc->rc_count;
 127         mutex_exit(&rc->rc_mtx);
 128
 129         return (count);
 130 }
 131
 132 int64_t
 133 refcount_add(refcount_t *rc, void *holder)
 134 {
 135         return (refcount_add_many(rc, 1, holder));
 136 }
 137
 138 int64_t
 139 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 140 {
 141         reference_t *ref;
 142         int64_t count;
 143
 144         mutex_enter(&rc->rc_mtx);
 145         ASSERT(rc->rc_count >= number);
 146
 147         if (!reference_tracking_enable) {
 148                 rc->rc_count -= number;
 149                 count = rc->rc_count;
 150                 mutex_exit(&rc->rc_mtx);
 151                 return (count);
 152         }
 153
 154         for (ref = list_head(&rc->rc_list); ref;
 155             ref = list_next(&rc->rc_list, ref)) {
 156                 if (ref->ref_holder == holder && ref->ref_number == number) {
 157                         list_remove(&rc->rc_list, ref);
 158                         if (reference_history > 0) {
 159                                 ref->ref_removed =
 160                                     kmem_cache_alloc(reference_history_cache,
 161                                     KM_SLEEP);
 162                                 list_insert_head(&rc->rc_removed, ref);
 163                                 rc->rc_removed_count++;
 164                                 if (rc->rc_removed_count >= reference_history) {
 165                                         ref = list_tail(&rc->rc_removed);
 166                                         list_remove(&rc->rc_removed, ref);
 167                                         kmem_cache_free(reference_history_cache,
 168                                             ref->ref_removed);
 169                                         kmem_cache_free(reference_cache, ref);
 170                                         rc->rc_removed_count--;
 171                                 }
 172                         } else {
 173                                 kmem_cache_free(reference_cache, ref);
 174                         }
 175                         rc->rc_count -= number;
 176                         count = rc->rc_count;
 177                         mutex_exit(&rc->rc_mtx);
 178                         return (count);
 179                 }
 180         }
 181         panic("No such hold %p on refcount %llx", holder,
 182             (u_longlong_t)(uintptr_t)rc);
 183         return (-1);
 184 }
 185
 186 int64_t
 187 refcount_remove(refcount_t *rc, void *holder)
 188 {
 189         return (refcount_remove_many(rc, 1, holder));
 190 }
 191
 192 void
 193 refcount_transfer(refcount_t *dst, refcount_t *src)
 194 {
 195         int64_t count, removed_count;
 196         list_t list, removed;
 197
 198         list_create(&list, sizeof (reference_t),
 199             offsetof(reference_t, ref_link));
 200         list_create(&removed, sizeof (reference_t),
 201             offsetof(reference_t, ref_link));
 202
 203         mutex_enter(&src->rc_mtx);
 204         count = src->rc_count;
 205         removed_count = src->rc_removed_count;
 206         src->rc_count = 0;
 207         src->rc_removed_count = 0;
 208         list_move_tail(&list, &src->rc_list);
 209         list_move_tail(&removed, &src->rc_removed);
 210         mutex_exit(&src->rc_mtx);
 211
 212         mutex_enter(&dst->rc_mtx);
 213         dst->rc_count += count;
 214         dst->rc_removed_count += removed_count;
 215         list_move_tail(&dst->rc_list, &list);
 216         list_move_tail(&dst->rc_removed, &removed);
 217         mutex_exit(&dst->rc_mtx);
 218
 219         list_destroy(&list);
 220         list_destroy(&removed);
 221 }
 222
 223 #endif  /* ZFS_DEBUG */