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, 2015 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_tracked(refcount_t *rc)
  77 {
  78         refcount_create(rc);
  79         rc->rc_tracked = B_TRUE;
  80 }
  81
  82 void
  83 refcount_create_untracked(refcount_t *rc)
  84 {
  85         refcount_create(rc);
  86         rc->rc_tracked = B_FALSE;
  87 }
  88
  89 void
  90 refcount_destroy_many(refcount_t *rc, uint64_t number)
  91 {
  92         reference_t *ref;
  93
  94         ASSERT(rc->rc_count == number);
  95         while (ref = list_head(&rc->rc_list)) {
  96                 list_remove(&rc->rc_list, ref);
  97                 kmem_cache_free(reference_cache, ref);
  98         }
  99         list_destroy(&rc->rc_list);
 100
 101         while (ref = list_head(&rc->rc_removed)) {
 102                 list_remove(&rc->rc_removed, ref);
 103                 kmem_cache_free(reference_history_cache, ref->ref_removed);
 104                 kmem_cache_free(reference_cache, ref);
 105         }
 106         list_destroy(&rc->rc_removed);
 107         mutex_destroy(&rc->rc_mtx);
 108 }
 109
 110 void
 111 refcount_destroy(refcount_t *rc)
 112 {
 113         refcount_destroy_many(rc, 0);
 114 }
 115
 116 int
 117 refcount_is_zero(refcount_t *rc)
 118 {
 119         return (rc->rc_count == 0);
 120 }
 121
 122 int64_t
 123 refcount_count(refcount_t *rc)
 124 {
 125         return (rc->rc_count);
 126 }
 127
 128 int64_t
 129 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
 130 {
 131         reference_t *ref = NULL;
 132         int64_t count;
 133
 134         if (rc->rc_tracked) {
 135                 ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
 136                 ref->ref_holder = holder;
 137                 ref->ref_number = number;
 138         }
 139         mutex_enter(&rc->rc_mtx);
 140         ASSERT(rc->rc_count >= 0);
 141         if (rc->rc_tracked)
 142                 list_insert_head(&rc->rc_list, ref);
 143         rc->rc_count += number;
 144         count = rc->rc_count;
 145         mutex_exit(&rc->rc_mtx);
 146
 147         return (count);
 148 }
 149
 150 int64_t
 151 refcount_add(refcount_t *rc, void *holder)
 152 {
 153         return (refcount_add_many(rc, 1, holder));
 154 }
 155
 156 int64_t
 157 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
 158 {
 159         reference_t *ref;
 160         int64_t count;
 161
 162         mutex_enter(&rc->rc_mtx);
 163         ASSERT(rc->rc_count >= number);
 164
 165         if (!rc->rc_tracked) {
 166                 rc->rc_count -= number;
 167                 count = rc->rc_count;
 168                 mutex_exit(&rc->rc_mtx);
 169                 return (count);
 170         }
 171
 172         for (ref = list_head(&rc->rc_list); ref;
 173             ref = list_next(&rc->rc_list, ref)) {
 174                 if (ref->ref_holder == holder && ref->ref_number == number) {
 175                         list_remove(&rc->rc_list, ref);
 176                         if (reference_history > 0) {
 177                                 ref->ref_removed =
 178                                     kmem_cache_alloc(reference_history_cache,
 179                                     KM_SLEEP);
 180                                 list_insert_head(&rc->rc_removed, ref);
 181                                 rc->rc_removed_count++;
 182                                 if (rc->rc_removed_count > reference_history) {
 183                                         ref = list_tail(&rc->rc_removed);
 184                                         list_remove(&rc->rc_removed, ref);
 185                                         kmem_cache_free(reference_history_cache,
 186                                             ref->ref_removed);
 187                                         kmem_cache_free(reference_cache, ref);
 188                                         rc->rc_removed_count--;
 189                                 }
 190                         } else {
 191                                 kmem_cache_free(reference_cache, ref);
 192                         }
 193                         rc->rc_count -= number;
 194                         count = rc->rc_count;
 195                         mutex_exit(&rc->rc_mtx);
 196                         return (count);
 197                 }
 198         }
 199         panic("No such hold %p on refcount %llx", holder,
 200             (u_longlong_t)(uintptr_t)rc);
 201         return (-1);
 202 }
 203
 204 int64_t
 205 refcount_remove(refcount_t *rc, void *holder)
 206 {
 207         return (refcount_remove_many(rc, 1, holder));
 208 }
 209
 210 void
 211 refcount_transfer(refcount_t *dst, refcount_t *src)
 212 {
 213         int64_t count, removed_count;
 214         list_t list, removed;
 215
 216         list_create(&list, sizeof (reference_t),
 217             offsetof(reference_t, ref_link));
 218         list_create(&removed, sizeof (reference_t),
 219             offsetof(reference_t, ref_link));
 220
 221         mutex_enter(&src->rc_mtx);
 222         count = src->rc_count;
 223         removed_count = src->rc_removed_count;
 224         src->rc_count = 0;
 225         src->rc_removed_count = 0;
 226         list_move_tail(&list, &src->rc_list);
 227         list_move_tail(&removed, &src->rc_removed);
 228         mutex_exit(&src->rc_mtx);
 229
 230         mutex_enter(&dst->rc_mtx);
 231         dst->rc_count += count;
 232         dst->rc_removed_count += removed_count;
 233         list_move_tail(&dst->rc_list, &list);
 234         list_move_tail(&dst->rc_removed, &removed);
 235         mutex_exit(&dst->rc_mtx);
 236
 237         list_destroy(&list);
 238         list_destroy(&removed);
 239 }
 240
 241 void
 242 refcount_transfer_ownership(refcount_t *rc, void *current_holder,
 243     void *new_holder)
 244 {
 245         reference_t *ref;
 246         boolean_t found = B_FALSE;
 247
 248         mutex_enter(&rc->rc_mtx);
 249         if (!rc->rc_tracked) {
 250                 mutex_exit(&rc->rc_mtx);
 251                 return;
 252         }
 253
 254         for (ref = list_head(&rc->rc_list); ref;
 255             ref = list_next(&rc->rc_list, ref)) {
 256                 if (ref->ref_holder == current_holder) {
 257                         ref->ref_holder = new_holder;
 258                         found = B_TRUE;
 259                         break;
 260                 }
 261         }
 262         ASSERT(found);
 263         mutex_exit(&rc->rc_mtx);
 264 }
 265
 266 /*
 267  * If tracking is enabled, return true if a reference exists that matches
 268  * the "holder" tag. If tracking is disabled, then return true if a reference
 269  * might be held.
 270  */
 271 boolean_t
 272 refcount_held(refcount_t *rc, void *holder)
 273 {
 274         reference_t *ref;
 275
 276         mutex_enter(&rc->rc_mtx);
 277
 278         if (!rc->rc_tracked) {
 279                 mutex_exit(&rc->rc_mtx);
 280                 return (rc->rc_count > 0);
 281         }
 282
 283         for (ref = list_head(&rc->rc_list); ref;
 284             ref = list_next(&rc->rc_list, ref)) {
 285                 if (ref->ref_holder == holder) {
 286                         mutex_exit(&rc->rc_mtx);
 287                         return (B_TRUE);
 288                 }
 289         }
 290         mutex_exit(&rc->rc_mtx);
 291         return (B_FALSE);
 292 }
 293
 294 /*
 295  * If tracking is enabled, return true if a reference does not exist that
 296  * matches the "holder" tag. If tracking is disabled, always return true
 297  * since the reference might not be held.
 298  */
 299 boolean_t
 300 refcount_not_held(refcount_t *rc, void *holder)
 301 {
 302         reference_t *ref;
 303
 304         mutex_enter(&rc->rc_mtx);
 305
 306         if (!rc->rc_tracked) {
 307                 mutex_exit(&rc->rc_mtx);
 308                 return (B_TRUE);
 309         }
 310
 311         for (ref = list_head(&rc->rc_list); ref;
 312             ref = list_next(&rc->rc_list, ref)) {
 313                 if (ref->ref_holder == holder) {
 314                         mutex_exit(&rc->rc_mtx);
 315                         return (B_FALSE);
 316                 }
 317         }
 318         mutex_exit(&rc->rc_mtx);
 319         return (B_TRUE);
 320 }
 321 #endif  /* ZFS_DEBUG */