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 TUNABLE_INT("vfs.zfs.reference_tracking_enable", &reference_tracking_enable);
  35 SYSCTL_INT(_vfs_zfs, OID_AUTO, reference_tracking_enable, CTLFLAG_RDTUN,
  36     &reference_tracking_enable, 0,
  37     "Track reference holders to refcount_t objects, used mostly by ZFS");
  38 #else
  39 int reference_tracking_enable = TRUE;
  40 #endif
  41 int reference_history = 3; /* tunable */
  42
  43 static kmem_cache_t *reference_cache;
  44 static kmem_cache_t *reference_history_cache;
  45
  46 void
  47 refcount_sysinit(void)
  48 {
  49         reference_cache = kmem_cache_create("reference_cache",
  50             sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  51
  52         reference_history_cache = kmem_cache_create("reference_history_cache",
  53             sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
  54 }
  55
  56 void
  57 refcount_fini(void)
  58 {
  59         kmem_cache_destroy(reference_cache);
  60         kmem_cache_destroy(reference_history_cache);
  61 }
  62
  63 void
  64 refcount_create(refcount_t *rc)
  65 {
  66         mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
  67         list_create(&rc->rc_list, sizeof (reference_t),
  68             offsetof(reference_t, ref_link));
  69         list_create(&rc->rc_removed, sizeof (reference_t),
  70             offsetof(reference_t, ref_link));
  71         rc->rc_count = 0;
  72         rc->rc_removed_count = 0;
  73         rc->rc_tracked = reference_tracking_enable;
  74 }
  75
  76 void
  77 refcount_create_untracked(refcount_t *rc)
  78 {
  79         refcount_create(rc);
  80         rc->rc_tracked = B_FALSE;
  81 }
  82
  83 void
  84 refcount_destroy_many(refcount_t *rc, uint64_t number)
  85 {
  86         reference_t *ref;
  87
  88         ASSERT(rc->rc_count == number);
  89         while (ref = list_head(&rc->rc_list)) {
  90                 list_remove(&rc->rc_list, ref);
  91                 kmem_cache_free(reference_cache, ref);
  92         }
  93         list_destroy(&rc->rc_list);
  94
  95         while (ref = list_head(&rc->rc_removed)) {
  96                 list_remove(&rc->rc_removed, ref);
  97                 kmem_cache_free(reference_history_cache, ref->ref_removed);
  98                 kmem_cache_free(reference_cache, ref);
  99         }
 100         list_destroy(&rc->rc_removed);
 101         mutex_destroy(&rc->rc_mtx);
 102 }
 103
 104 void
 105 refcount_destroy(refcount_t *rc)
 106 {
 107         refcount_destroy_many(rc, 0);
 108 }
 109
 110 int
 111 refcount_is_zero(refcount_t *rc)
 112 {
 113         return (rc->rc_count == 0);
 114 }
 115
 116 int64_t
 117 refcount_count(refcount_t *rc)
 118 {
 119         return (rc->rc_count);
 120 }
 121
 122 int64_t
 123 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 124 {
 125         reference_t *ref = NULL;
 126         int64_t count;
 127
 128         if (rc->rc_tracked) {
 129                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 130                 ref->ref_holder = holder;
 131                 ref->ref_number = number;
 132         }
 133         mutex_enter(&rc->rc_mtx);
 134         ASSERT(rc->rc_count >= 0);
 135         if (rc->rc_tracked)
 136                 list_insert_head(&rc->rc_list, ref);
 137         rc->rc_count += number;
 138         count = rc->rc_count;
 139         mutex_exit(&rc->rc_mtx);
 140
 141         return (count);
 142 }
 143
 144 int64_t
 145 refcount_add(refcount_t *rc, void *holder)
 146 {
 147         return (refcount_add_many(rc, 1, holder));
 148 }
 149
 150 int64_t
 151 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 152 {
 153         reference_t *ref;
 154         int64_t count;
 155
 156         mutex_enter(&rc->rc_mtx);
 157         ASSERT(rc->rc_count >= number);
 158
 159         if (!rc->rc_tracked) {
 160                 rc->rc_count -= number;
 161                 count = rc->rc_count;
 162                 mutex_exit(&rc->rc_mtx);
 163                 return (count);
 164         }
 165
 166         for (ref = list_head(&rc->rc_list); ref;
 167             ref = list_next(&rc->rc_list, ref)) {
 168                 if (ref->ref_holder == holder && ref->ref_number == number) {
 169                         list_remove(&rc->rc_list, ref);
 170                         if (reference_history > 0) {
 171                                 ref->ref_removed =
 172                                     kmem_cache_alloc(reference_history_cache,
 173                                     KM_SLEEP);
 174                                 list_insert_head(&rc->rc_removed, ref);
 175                                 rc->rc_removed_count++;
 176                                 if (rc->rc_removed_count > reference_history) {
 177                                         ref = list_tail(&rc->rc_removed);
 178                                         list_remove(&rc->rc_removed, ref);
 179                                         kmem_cache_free(reference_history_cache,
 180                                             ref->ref_removed);
 181                                         kmem_cache_free(reference_cache, ref);
 182                                         rc->rc_removed_count--;
 183                                 }
 184                         } else {
 185                                 kmem_cache_free(reference_cache, ref);
 186                         }
 187                         rc->rc_count -= number;
 188                         count = rc->rc_count;
 189                         mutex_exit(&rc->rc_mtx);
 190                         return (count);
 191                 }
 192         }
 193         panic("No such hold %p on refcount %llx", holder,
 194             (u_longlong_t)(uintptr_t)rc);
 195         return (-1);
 196 }
 197
 198 int64_t
 199 refcount_remove(refcount_t *rc, void *holder)
 200 {
 201         return (refcount_remove_many(rc, 1, holder));
 202 }
 203
 204 void
 205 refcount_transfer(refcount_t *dst, refcount_t *src)
 206 {
 207         int64_t count, removed_count;
 208         list_t list, removed;
 209
 210         list_create(&list, sizeof (reference_t),
 211             offsetof(reference_t, ref_link));
 212         list_create(&removed, sizeof (reference_t),
 213             offsetof(reference_t, ref_link));
 214
 215         mutex_enter(&src->rc_mtx);
 216         count = src->rc_count;
 217         removed_count = src->rc_removed_count;
 218         src->rc_count = 0;
 219         src->rc_removed_count = 0;
 220         list_move_tail(&list, &src->rc_list);
 221         list_move_tail(&removed, &src->rc_removed);
 222         mutex_exit(&src->rc_mtx);
 223
 224         mutex_enter(&dst->rc_mtx);
 225         dst->rc_count += count;
 226         dst->rc_removed_count += removed_count;
 227         list_move_tail(&dst->rc_list, &list);
 228         list_move_tail(&dst->rc_removed, &removed);
 229         mutex_exit(&dst->rc_mtx);
 230
 231         list_destroy(&list);
 232         list_destroy(&removed);
 233 }
 234
 235 void
 236 refcount_transfer_ownership(refcount_t *rc, void *current_holder,
 237     void *new_holder)
 238 {
 239         reference_t *ref;
 240         boolean_t found = B_FALSE;
 241
 242         mutex_enter(&rc->rc_mtx);
 243         if (!rc->rc_tracked) {
 244                 mutex_exit(&rc->rc_mtx);
 245                 return;
 246         }
 247
 248         for (ref = list_head(&rc->rc_list); ref;
 249             ref = list_next(&rc->rc_list, ref)) {
 250                 if (ref->ref_holder == current_holder) {
 251                         ref->ref_holder = new_holder;
 252                         found = B_TRUE;
 253                         break;
 254                 }
 255         }
 256         ASSERT(found);
 257         mutex_exit(&rc->rc_mtx);
 258 }
 259 #endif  /* ZFS_DEBUG */