fs/btrfs/delayed-ref.c

   1 /*
   2  * Copyright (C) 2009 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/sched.h>
  20 #include <linux/sort.h>
  21 #include "ctree.h"
  22 #include "delayed-ref.h"
  23 #include "transaction.h"
  24
  25 /*
  26  * delayed back reference update tracking.  For subvolume trees
  27  * we queue up extent allocations and backref maintenance for
  28  * delayed processing.   This avoids deep call chains where we
  29  * add extents in the middle of btrfs_search_slot, and it allows
  30  * us to buffer up frequently modified backrefs in an rb tree instead
  31  * of hammering updates on the extent allocation tree.
  32  *
  33  * Right now this code is only used for reference counted trees, but
  34  * the long term goal is to get rid of the similar code for delayed
  35  * extent tree modifications.
  36  */
  37
  38 /*
  39  * entries in the rb tree are ordered by the byte number of the extent
  40  * and by the byte number of the parent block.
  41  */
  42 static int comp_entry(struct btrfs_delayed_ref_node *ref,
  43                       u64 bytenr, u64 parent)
  44 {
  45         if (bytenr < ref->bytenr)
  46                 return -1;
  47         if (bytenr > ref->bytenr)
  48                 return 1;
  49         if (parent < ref->parent)
  50                 return -1;
  51         if (parent > ref->parent)
  52                 return 1;
  53         return 0;
  54 }
  55
  56 /*
  57  * insert a new ref into the rbtree.  This returns any existing refs
  58  * for the same (bytenr,parent) tuple, or NULL if the new node was properly
  59  * inserted.
  60  */
  61 static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
  62                                                   u64 bytenr, u64 parent,
  63                                                   struct rb_node *node)
  64 {
  65         struct rb_node **p = &root->rb_node;
  66         struct rb_node *parent_node = NULL;
  67         struct btrfs_delayed_ref_node *entry;
  68         int cmp;
  69
  70         while (*p) {
  71                 parent_node = *p;
  72                 entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
  73                                  rb_node);
  74
  75                 cmp = comp_entry(entry, bytenr, parent);
  76                 if (cmp < 0)
  77                         p = &(*p)->rb_left;
  78                 else if (cmp > 0)
  79                         p = &(*p)->rb_right;
  80                 else
  81                         return entry;
  82         }
  83
  84         entry = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
  85         rb_link_node(node, parent_node, p);
  86         rb_insert_color(node, root);
  87         return NULL;
  88 }
  89
  90 /*
  91  * find an entry based on (bytenr,parent).  This returns the delayed
  92  * ref if it was able to find one, or NULL if nothing was in that spot
  93  */
  94 static struct btrfs_delayed_ref_node *tree_search(struct rb_root *root,
  95                                   u64 bytenr, u64 parent,
  96                                   struct btrfs_delayed_ref_node **last)
  97 {
  98         struct rb_node *n = root->rb_node;
  99         struct btrfs_delayed_ref_node *entry;
 100         int cmp;
 101
 102         while (n) {
 103                 entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
 104                 WARN_ON(!entry->in_tree);
 105                 if (last)
 106                         *last = entry;
 107
 108                 cmp = comp_entry(entry, bytenr, parent);
 109                 if (cmp < 0)
 110                         n = n->rb_left;
 111                 else if (cmp > 0)
 112                         n = n->rb_right;
 113                 else
 114                         return entry;
 115         }
 116         return NULL;
 117 }
 118
 119 int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
 120                            struct btrfs_delayed_ref_head *head)
 121 {
 122         struct btrfs_delayed_ref_root *delayed_refs;
 123
 124         delayed_refs = &trans->transaction->delayed_refs;
 125         assert_spin_locked(&delayed_refs->lock);
 126         if (mutex_trylock(&head->mutex))
 127                 return 0;
 128
 129         atomic_inc(&head->node.refs);
 130         spin_unlock(&delayed_refs->lock);
 131
 132         mutex_lock(&head->mutex);
 133         spin_lock(&delayed_refs->lock);
 134         if (!head->node.in_tree) {
 135                 mutex_unlock(&head->mutex);
 136                 btrfs_put_delayed_ref(&head->node);
 137                 return -EAGAIN;
 138         }
 139         btrfs_put_delayed_ref(&head->node);
 140         return 0;
 141 }
 142
 143 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
 144                            struct list_head *cluster, u64 start)
 145 {
 146         int count = 0;
 147         struct btrfs_delayed_ref_root *delayed_refs;
 148         struct rb_node *node;
 149         struct btrfs_delayed_ref_node *ref;
 150         struct btrfs_delayed_ref_head *head;
 151
 152         delayed_refs = &trans->transaction->delayed_refs;
 153         if (start == 0) {
 154                 node = rb_first(&delayed_refs->root);
 155         } else {
 156                 ref = NULL;
 157                 tree_search(&delayed_refs->root, start, (u64)-1, &ref);
 158                 if (ref) {
 159                         struct btrfs_delayed_ref_node *tmp;
 160
 161                         node = rb_prev(&ref->rb_node);
 162                         while (node) {
 163                                 tmp = rb_entry(node,
 164                                                struct btrfs_delayed_ref_node,
 165                                                rb_node);
 166                                 if (tmp->bytenr < start)
 167                                         break;
 168                                 ref = tmp;
 169                                 node = rb_prev(&ref->rb_node);
 170                         }
 171                         node = &ref->rb_node;
 172                 } else
 173                         node = rb_first(&delayed_refs->root);
 174         }
 175 again:
 176         while (node && count < 32) {
 177                 ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
 178                 if (btrfs_delayed_ref_is_head(ref)) {
 179                         head = btrfs_delayed_node_to_head(ref);
 180                         if (list_empty(&head->cluster)) {
 181                                 list_add_tail(&head->cluster, cluster);
 182                                 delayed_refs->run_delayed_start =
 183                                         head->node.bytenr;
 184                                 count++;
 185
 186                                 WARN_ON(delayed_refs->num_heads_ready == 0);
 187                                 delayed_refs->num_heads_ready--;
 188                         } else if (count) {
 189                                 /* the goal of the clustering is to find extents
 190                                  * that are likely to end up in the same extent
 191                                  * leaf on disk.  So, we don't want them spread
 192                                  * all over the tree.  Stop now if we've hit
 193                                  * a head that was already in use
 194                                  */
 195                                 break;
 196                         }
 197                 }
 198                 node = rb_next(node);
 199         }
 200         if (count) {
 201                 return 0;
 202         } else if (start) {
 203                 /*
 204                  * we've gone to the end of the rbtree without finding any
 205                  * clusters.  start from the beginning and try again
 206                  */
 207                 start = 0;
 208                 node = rb_first(&delayed_refs->root);
 209                 goto again;
 210         }
 211         return 1;
 212 }
 213
 214 /*
 215  * This checks to see if there are any delayed refs in the
 216  * btree for a given bytenr.  It returns one if it finds any
 217  * and zero otherwise.
 218  *
 219  * If it only finds a head node, it returns 0.
 220  *
 221  * The idea is to use this when deciding if you can safely delete an
 222  * extent from the extent allocation tree.  There may be a pending
 223  * ref in the rbtree that adds or removes references, so as long as this
 224  * returns one you need to leave the BTRFS_EXTENT_ITEM in the extent
 225  * allocation tree.
 226  */
 227 int btrfs_delayed_ref_pending(struct btrfs_trans_handle *trans, u64 bytenr)
 228 {
 229         struct btrfs_delayed_ref_node *ref;
 230         struct btrfs_delayed_ref_root *delayed_refs;
 231         struct rb_node *prev_node;
 232         int ret = 0;
 233
 234         delayed_refs = &trans->transaction->delayed_refs;
 235         spin_lock(&delayed_refs->lock);
 236
 237         ref = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
 238         if (ref) {
 239                 prev_node = rb_prev(&ref->rb_node);
 240                 if (!prev_node)
 241                         goto out;
 242                 ref = rb_entry(prev_node, struct btrfs_delayed_ref_node,
 243                                rb_node);
 244                 if (ref->bytenr == bytenr)
 245                         ret = 1;
 246         }
 247 out:
 248         spin_unlock(&delayed_refs->lock);
 249         return ret;
 250 }
 251
 252 /*
 253  * helper function to lookup reference count
 254  *
 255  * the head node for delayed ref is used to store the sum of all the
 256  * reference count modifications queued up in the rbtree.  This way you
 257  * can check to see what the reference count would be if all of the
 258  * delayed refs are processed.
 259  */
 260 int btrfs_lookup_extent_ref(struct btrfs_trans_handle *trans,
 261                             struct btrfs_root *root, u64 bytenr,
 262                             u64 num_bytes, u32 *refs)
 263 {
 264         struct btrfs_delayed_ref_node *ref;
 265         struct btrfs_delayed_ref_head *head;
 266         struct btrfs_delayed_ref_root *delayed_refs;
 267         struct btrfs_path *path;
 268         struct extent_buffer *leaf;
 269         struct btrfs_extent_item *ei;
 270         struct btrfs_key key;
 271         u32 num_refs;
 272         int ret;
 273
 274         path = btrfs_alloc_path();
 275         if (!path)
 276                 return -ENOMEM;
 277
 278         key.objectid = bytenr;
 279         key.type = BTRFS_EXTENT_ITEM_KEY;
 280         key.offset = num_bytes;
 281         delayed_refs = &trans->transaction->delayed_refs;
 282 again:
 283         ret = btrfs_search_slot(trans, root->fs_info->extent_root,
 284                                 &key, path, 0, 0);
 285         if (ret < 0)
 286                 goto out;
 287
 288         if (ret == 0) {
 289                 leaf = path->nodes[0];
 290                 ei = btrfs_item_ptr(leaf, path->slots[0],
 291                                     struct btrfs_extent_item);
 292                 num_refs = btrfs_extent_refs(leaf, ei);
 293         } else {
 294                 num_refs = 0;
 295                 ret = 0;
 296         }
 297
 298         spin_lock(&delayed_refs->lock);
 299         ref = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
 300         if (ref) {
 301                 head = btrfs_delayed_node_to_head(ref);
 302                 if (mutex_trylock(&head->mutex)) {
 303                         num_refs += ref->ref_mod;
 304                         mutex_unlock(&head->mutex);
 305                         *refs = num_refs;
 306                         goto out;
 307                 }
 308
 309                 atomic_inc(&ref->refs);
 310                 spin_unlock(&delayed_refs->lock);
 311
 312                 btrfs_release_path(root->fs_info->extent_root, path);
 313
 314                 mutex_lock(&head->mutex);
 315                 mutex_unlock(&head->mutex);
 316                 btrfs_put_delayed_ref(ref);
 317                 goto again;
 318         } else {
 319                 *refs = num_refs;
 320         }
 321 out:
 322         spin_unlock(&delayed_refs->lock);
 323         btrfs_free_path(path);
 324         return ret;
 325 }
 326
 327 /*
 328  * helper function to update an extent delayed ref in the
 329  * rbtree.  existing and update must both have the same
 330  * bytenr and parent
 331  *
 332  * This may free existing if the update cancels out whatever
 333  * operation it was doing.
 334  */
 335 static noinline void
 336 update_existing_ref(struct btrfs_trans_handle *trans,
 337                     struct btrfs_delayed_ref_root *delayed_refs,
 338                     struct btrfs_delayed_ref_node *existing,
 339                     struct btrfs_delayed_ref_node *update)
 340 {
 341         struct btrfs_delayed_ref *existing_ref;
 342         struct btrfs_delayed_ref *ref;
 343
 344         existing_ref = btrfs_delayed_node_to_ref(existing);
 345         ref = btrfs_delayed_node_to_ref(update);
 346
 347         if (ref->pin)
 348                 existing_ref->pin = 1;
 349
 350         if (ref->action != existing_ref->action) {
 351                 /*
 352                  * this is effectively undoing either an add or a
 353                  * drop.  We decrement the ref_mod, and if it goes
 354                  * down to zero we just delete the entry without
 355                  * every changing the extent allocation tree.
 356                  */
 357                 existing->ref_mod--;
 358                 if (existing->ref_mod == 0) {
 359                         rb_erase(&existing->rb_node,
 360                                  &delayed_refs->root);
 361                         existing->in_tree = 0;
 362                         btrfs_put_delayed_ref(existing);
 363                         delayed_refs->num_entries--;
 364                         if (trans->delayed_ref_updates)
 365                                 trans->delayed_ref_updates--;
 366                 }
 367         } else {
 368                 if (existing_ref->action == BTRFS_ADD_DELAYED_REF) {
 369                         /* if we're adding refs, make sure all the
 370                          * details match up.  The extent could
 371                          * have been totally freed and reallocated
 372                          * by a different owner before the delayed
 373                          * ref entries were removed.
 374                          */
 375                         existing_ref->owner_objectid = ref->owner_objectid;
 376                         existing_ref->generation = ref->generation;
 377                         existing_ref->root = ref->root;
 378                         existing->num_bytes = update->num_bytes;
 379                 }
 380                 /*
 381                  * the action on the existing ref matches
 382                  * the action on the ref we're trying to add.
 383                  * Bump the ref_mod by one so the backref that
 384                  * is eventually added/removed has the correct
 385                  * reference count
 386                  */
 387                 existing->ref_mod += update->ref_mod;
 388         }
 389 }
 390
 391 /*
 392  * helper function to update the accounting in the head ref
 393  * existing and update must have the same bytenr
 394  */
 395 static noinline void
 396 update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
 397                          struct btrfs_delayed_ref_node *update)
 398 {
 399         struct btrfs_delayed_ref_head *existing_ref;
 400         struct btrfs_delayed_ref_head *ref;
 401
 402         existing_ref = btrfs_delayed_node_to_head(existing);
 403         ref = btrfs_delayed_node_to_head(update);
 404
 405         if (ref->must_insert_reserved) {
 406                 /* if the extent was freed and then
 407                  * reallocated before the delayed ref
 408                  * entries were processed, we can end up
 409                  * with an existing head ref without
 410                  * the must_insert_reserved flag set.
 411                  * Set it again here
 412                  */
 413                 existing_ref->must_insert_reserved = ref->must_insert_reserved;
 414
 415                 /*
 416                  * update the num_bytes so we make sure the accounting
 417                  * is done correctly
 418                  */
 419                 existing->num_bytes = update->num_bytes;
 420
 421         }
 422
 423         /*
 424          * update the reference mod on the head to reflect this new operation
 425          */
 426         existing->ref_mod += update->ref_mod;
 427 }
 428
 429 /*
 430  * helper function to actually insert a delayed ref into the rbtree.
 431  * this does all the dirty work in terms of maintaining the correct
 432  * overall modification count in the head node and properly dealing
 433  * with updating existing nodes as new modifications are queued.
 434  */
 435 static noinline int __btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
 436                           struct btrfs_delayed_ref_node *ref,
 437                           u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
 438                           u64 ref_generation, u64 owner_objectid, int action,
 439                           int pin)
 440 {
 441         struct btrfs_delayed_ref_node *existing;
 442         struct btrfs_delayed_ref *full_ref;
 443         struct btrfs_delayed_ref_head *head_ref = NULL;
 444         struct btrfs_delayed_ref_root *delayed_refs;
 445         int count_mod = 1;
 446         int must_insert_reserved = 0;
 447
 448         /*
 449          * the head node stores the sum of all the mods, so dropping a ref
 450          * should drop the sum in the head node by one.
 451          */
 452         if (parent == (u64)-1) {
 453                 if (action == BTRFS_DROP_DELAYED_REF)
 454                         count_mod = -1;
 455                 else if (action == BTRFS_UPDATE_DELAYED_HEAD)
 456                         count_mod = 0;
 457         }
 458
 459         /*
 460          * BTRFS_ADD_DELAYED_EXTENT means that we need to update
 461          * the reserved accounting when the extent is finally added, or
 462          * if a later modification deletes the delayed ref without ever
 463          * inserting the extent into the extent allocation tree.
 464          * ref->must_insert_reserved is the flag used to record
 465          * that accounting mods are required.
 466          *
 467          * Once we record must_insert_reserved, switch the action to
 468          * BTRFS_ADD_DELAYED_REF because other special casing is not required.
 469          */
 470         if (action == BTRFS_ADD_DELAYED_EXTENT) {
 471                 must_insert_reserved = 1;
 472                 action = BTRFS_ADD_DELAYED_REF;
 473         } else {
 474                 must_insert_reserved = 0;
 475         }
 476
 477
 478         delayed_refs = &trans->transaction->delayed_refs;
 479
 480         /* first set the basic ref node struct up */
 481         atomic_set(&ref->refs, 1);
 482         ref->bytenr = bytenr;
 483         ref->parent = parent;
 484         ref->ref_mod = count_mod;
 485         ref->in_tree = 1;
 486         ref->num_bytes = num_bytes;
 487
 488         if (btrfs_delayed_ref_is_head(ref)) {
 489                 head_ref = btrfs_delayed_node_to_head(ref);
 490                 head_ref->must_insert_reserved = must_insert_reserved;
 491                 INIT_LIST_HEAD(&head_ref->cluster);
 492                 mutex_init(&head_ref->mutex);
 493         } else {
 494                 full_ref = btrfs_delayed_node_to_ref(ref);
 495                 full_ref->root = ref_root;
 496                 full_ref->generation = ref_generation;
 497                 full_ref->owner_objectid = owner_objectid;
 498                 full_ref->pin = pin;
 499                 full_ref->action = action;
 500         }
 501
 502         existing = tree_insert(&delayed_refs->root, bytenr,
 503                                parent, &ref->rb_node);
 504
 505         if (existing) {
 506                 if (btrfs_delayed_ref_is_head(ref))
 507                         update_existing_head_ref(existing, ref);
 508                 else
 509                         update_existing_ref(trans, delayed_refs, existing, ref);
 510
 511                 /*
 512                  * we've updated the existing ref, free the newly
 513                  * allocated ref
 514                  */
 515                 kfree(ref);
 516         } else {
 517                 if (btrfs_delayed_ref_is_head(ref)) {
 518                         delayed_refs->num_heads++;
 519                         delayed_refs->num_heads_ready++;
 520                 }
 521                 delayed_refs->num_entries++;
 522                 trans->delayed_ref_updates++;
 523         }
 524         return 0;
 525 }
 526
 527 /*
 528  * add a delayed ref to the tree.  This does all of the accounting required
 529  * to make sure the delayed ref is eventually processed before this
 530  * transaction commits.
 531  */
 532 int btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
 533                           u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
 534                           u64 ref_generation, u64 owner_objectid, int action,
 535                           int pin)
 536 {
 537         struct btrfs_delayed_ref *ref;
 538         struct btrfs_delayed_ref_head *head_ref;
 539         struct btrfs_delayed_ref_root *delayed_refs;
 540         int ret;
 541
 542         ref = kmalloc(sizeof(*ref), GFP_NOFS);
 543         if (!ref)
 544                 return -ENOMEM;
 545
 546         /*
 547          * the parent = 0 case comes from cases where we don't actually
 548          * know the parent yet.  It will get updated later via a add/drop
 549          * pair.
 550          */
 551         if (parent == 0)
 552                 parent = bytenr;
 553
 554         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
 555         if (!head_ref) {
 556                 kfree(ref);
 557                 return -ENOMEM;
 558         }
 559         delayed_refs = &trans->transaction->delayed_refs;
 560         spin_lock(&delayed_refs->lock);
 561
 562         /*
 563          * insert both the head node and the new ref without dropping
 564          * the spin lock
 565          */
 566         ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
 567                                       (u64)-1, 0, 0, 0, action, pin);
 568         BUG_ON(ret);
 569
 570         ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
 571                                       parent, ref_root, ref_generation,
 572                                       owner_objectid, action, pin);
 573         BUG_ON(ret);
 574         spin_unlock(&delayed_refs->lock);
 575         return 0;
 576 }
 577
 578 /*
 579  * this does a simple search for the head node for a given extent.
 580  * It must be called with the delayed ref spinlock held, and it returns
 581  * the head node if any where found, or NULL if not.
 582  */
 583 struct btrfs_delayed_ref_head *
 584 btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
 585 {
 586         struct btrfs_delayed_ref_node *ref;
 587         struct btrfs_delayed_ref_root *delayed_refs;
 588
 589         delayed_refs = &trans->transaction->delayed_refs;
 590         ref = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
 591         if (ref)
 592                 return btrfs_delayed_node_to_head(ref);
 593         return NULL;
 594 }
 595
 596 /*
 597  * add a delayed ref to the tree.  This does all of the accounting required
 598  * to make sure the delayed ref is eventually processed before this
 599  * transaction commits.
 600  *
 601  * The main point of this call is to add and remove a backreference in a single
 602  * shot, taking the lock only once, and only searching for the head node once.
 603  *
 604  * It is the same as doing a ref add and delete in two separate calls.
 605  */
 606 int btrfs_update_delayed_ref(struct btrfs_trans_handle *trans,
 607                           u64 bytenr, u64 num_bytes, u64 orig_parent,
 608                           u64 parent, u64 orig_ref_root, u64 ref_root,
 609                           u64 orig_ref_generation, u64 ref_generation,
 610                           u64 owner_objectid, int pin)
 611 {
 612         struct btrfs_delayed_ref *ref;
 613         struct btrfs_delayed_ref *old_ref;
 614         struct btrfs_delayed_ref_head *head_ref;
 615         struct btrfs_delayed_ref_root *delayed_refs;
 616         int ret;
 617
 618         ref = kmalloc(sizeof(*ref), GFP_NOFS);
 619         if (!ref)
 620                 return -ENOMEM;
 621
 622         old_ref = kmalloc(sizeof(*old_ref), GFP_NOFS);
 623         if (!old_ref) {
 624                 kfree(ref);
 625                 return -ENOMEM;
 626         }
 627
 628         /*
 629          * the parent = 0 case comes from cases where we don't actually
 630          * know the parent yet.  It will get updated later via a add/drop
 631          * pair.
 632          */
 633         if (parent == 0)
 634                 parent = bytenr;
 635         if (orig_parent == 0)
 636                 orig_parent = bytenr;
 637
 638         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
 639         if (!head_ref) {
 640                 kfree(ref);
 641                 kfree(old_ref);
 642                 return -ENOMEM;
 643         }
 644         delayed_refs = &trans->transaction->delayed_refs;
 645         spin_lock(&delayed_refs->lock);
 646
 647         /*
 648          * insert both the head node and the new ref without dropping
 649          * the spin lock
 650          */
 651         ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
 652                                       (u64)-1, 0, 0, 0,
 653                                       BTRFS_UPDATE_DELAYED_HEAD, 0);
 654         BUG_ON(ret);
 655
 656         ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
 657                                       parent, ref_root, ref_generation,
 658                                       owner_objectid, BTRFS_ADD_DELAYED_REF, 0);
 659         BUG_ON(ret);
 660
 661         ret = __btrfs_add_delayed_ref(trans, &old_ref->node, bytenr, num_bytes,
 662                                       orig_parent, orig_ref_root,
 663                                       orig_ref_generation, owner_objectid,
 664                                       BTRFS_DROP_DELAYED_REF, pin);
 665         BUG_ON(ret);
 666         spin_unlock(&delayed_refs->lock);
 667         return 0;
 668 }