sys/cddl/contrib/opensolaris/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 SYSCTL_DECL(_vfs_zfs);
  34 SYSCTL_INT(_vfs_zfs, OID_AUTO, reference_tracking_enable, CTLFLAG_RDTUN,
  35     &reference_tracking_enable, 0,
  36     "Track reference holders to refcount_t objects, used mostly by ZFS");
  37 #else
  38 int reference_tracking_enable = TRUE;
  39 #endif
  40 int reference_history = 3; /* tunable */
  41
  42 static kmem_cache_t *reference_cache;
  43 static kmem_cache_t *reference_history_cache;
  44
  45 void
  46 refcount_sysinit(void)
  47 {
  48         reference_cache = kmem_cache_create("reference_cache",
  49             sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  50
  51         reference_history_cache = kmem_cache_create("reference_history_cache",
  52             sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  53 }
  54
  55 void
  56 refcount_fini(void)
  57 {
  58         kmem_cache_destroy(reference_cache);
  59         kmem_cache_destroy(reference_history_cache);
  60 }
  61
  62 void
  63 refcount_create(refcount_t *rc)
  64 {
  65         mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
  66         list_create(&rc->rc_list, sizeof (reference_t),
  67             offsetof(reference_t, ref_link));
  68         list_create(&rc->rc_removed, sizeof (reference_t),
  69             offsetof(reference_t, ref_link));
  70         rc->rc_count = 0;
  71         rc->rc_removed_count = 0;
  72         rc->rc_tracked = reference_tracking_enable;
  73 }
  74
  75 void
  76 refcount_create_untracked(refcount_t *rc)
  77 {
  78         refcount_create(rc);
  79         rc->rc_tracked = B_FALSE;
  80 }
  81
  82 void
  83 refcount_destroy_many(refcount_t *rc, uint64_t number)
  84 {
  85         reference_t *ref;
  86
  87         ASSERT(rc->rc_count == number);
  88         while (ref = list_head(&rc->rc_list)) {
  89                 list_remove(&rc->rc_list, ref);
  90                 kmem_cache_free(reference_cache, ref);
  91         }
  92         list_destroy(&rc->rc_list);
  93
  94         while (ref = list_head(&rc->rc_removed)) {
  95                 list_remove(&rc->rc_removed, ref);
  96                 kmem_cache_free(reference_history_cache, ref->ref_removed);
  97                 kmem_cache_free(reference_cache, ref);
  98         }
  99         list_destroy(&rc->rc_removed);
 100         mutex_destroy(&rc->rc_mtx);
 101 }
 102
 103 void
 104 refcount_destroy(refcount_t *rc)
 105 {
 106         refcount_destroy_many(rc, 0);
 107 }
 108
 109 int
 110 refcount_is_zero(refcount_t *rc)
 111 {
 112         return (rc->rc_count == 0);
 113 }
 114
 115 int64_t
 116 refcount_count(refcount_t *rc)
 117 {
 118         return (rc->rc_count);
 119 }
 120
 121 int64_t
 122 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 123 {
 124         reference_t *ref = NULL;
 125         int64_t count;
 126
 127         if (rc->rc_tracked) {
 128                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 129                 ref->ref_holder = holder;
 130                 ref->ref_number = number;
 131         }
 132         mutex_enter(&rc->rc_mtx);
 133         ASSERT(rc->rc_count >= 0);
 134         if (rc->rc_tracked)
 135                 list_insert_head(&rc->rc_list, ref);
 136         rc->rc_count += number;
 137         count = rc->rc_count;
 138         mutex_exit(&rc->rc_mtx);
 139
 140         return (count);
 141 }
 142
 143 int64_t
 144 refcount_add(refcount_t *rc, void *holder)
 145 {
 146         return (refcount_add_many(rc, 1, holder));
 147 }
 148
 149 int64_t
 150 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 151 {
 152         reference_t *ref;
 153         int64_t count;
 154
 155         mutex_enter(&rc->rc_mtx);
 156         ASSERT(rc->rc_count >= number);
 157
 158         if (!rc->rc_tracked) {
 159                 rc->rc_count -= number;
 160                 count = rc->rc_count;
 161                 mutex_exit(&rc->rc_mtx);
 162                 return (count);
 163         }
 164
 165         for (ref = list_head(&rc->rc_list); ref;
 166             ref = list_next(&rc->rc_list, ref)) {
 167                 if (ref->ref_holder == holder && ref->ref_number == number) {
 168                         list_remove(&rc->rc_list, ref);
 169                         if (reference_history > 0) {
 170                                 ref->ref_removed =
 171                                     kmem_cache_alloc(reference_history_cache,
 172                                     KM_SLEEP);
 173                                 list_insert_head(&rc->rc_removed, ref);
 174                                 rc->rc_removed_count++;
 175                                 if (rc->rc_removed_count > reference_history) {
 176                                         ref = list_tail(&rc->rc_removed);
 177                                         list_remove(&rc->rc_removed, ref);
 178                                         kmem_cache_free(reference_history_cache,
 179                                             ref->ref_removed);
 180                                         kmem_cache_free(reference_cache, ref);
 181                                         rc->rc_removed_count--;
 182                                 }
 183                         } else {
 184                                 kmem_cache_free(reference_cache, ref);
 185                         }
 186                         rc->rc_count -= number;
 187                         count = rc->rc_count;
 188                         mutex_exit(&rc->rc_mtx);
 189                         return (count);
 190                 }
 191         }
 192         panic("No such hold %p on refcount %llx", holder,
 193             (u_longlong_t)(uintptr_t)rc);
 194         return (-1);
 195 }
 196
 197 int64_t
 198 refcount_remove(refcount_t *rc, void *holder)
 199 {
 200         return (refcount_remove_many(rc, 1, holder));
 201 }
 202
 203 void
 204 refcount_transfer(refcount_t *dst, refcount_t *src)
 205 {
 206         int64_t count, removed_count;
 207         list_t list, removed;
 208
 209         list_create(&list, sizeof (reference_t),
 210             offsetof(reference_t, ref_link));
 211         list_create(&removed, sizeof (reference_t),
 212             offsetof(reference_t, ref_link));
 213
 214         mutex_enter(&src->rc_mtx);
 215         count = src->rc_count;
 216         removed_count = src->rc_removed_count;
 217         src->rc_count = 0;
 218         src->rc_removed_count = 0;
 219         list_move_tail(&list, &src->rc_list);
 220         list_move_tail(&removed, &src->rc_removed);
 221         mutex_exit(&src->rc_mtx);
 222
 223         mutex_enter(&dst->rc_mtx);
 224         dst->rc_count += count;
 225         dst->rc_removed_count += removed_count;
 226         list_move_tail(&dst->rc_list, &list);
 227         list_move_tail(&dst->rc_removed, &removed);
 228         mutex_exit(&dst->rc_mtx);
 229
 230         list_destroy(&list);
 231         list_destroy(&removed);
 232 }
 233
 234 #endif  /* ZFS_DEBUG */