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