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/slab.h>
  21 #include <linux/sort.h>
  22 #include "ctree.h"
  23 #include "delayed-ref.h"
  24 #include "transaction.h"
  25
  26 /*
  27  * delayed back reference update tracking.  For subvolume trees
  28  * we queue up extent allocations and backref maintenance for
  29  * delayed processing.   This avoids deep call chains where we
  30  * add extents in the middle of btrfs_search_slot, and it allows
  31  * us to buffer up frequently modified backrefs in an rb tree instead
  32  * of hammering updates on the extent allocation tree.
  33  */
  34
  35 /*
  36  * compare two delayed tree backrefs with same bytenr and type
  37  */
  38 static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
  39                           struct btrfs_delayed_tree_ref *ref1)
  40 {
  41         if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
  42                 if (ref1->root < ref2->root)
  43                         return -1;
  44                 if (ref1->root > ref2->root)
  45                         return 1;
  46         } else {
  47                 if (ref1->parent < ref2->parent)
  48                         return -1;
  49                 if (ref1->parent > ref2->parent)
  50                         return 1;
  51         }
  52         return 0;
  53 }
  54
  55 /*
  56  * compare two delayed data backrefs with same bytenr and type
  57  */
  58 static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
  59                           struct btrfs_delayed_data_ref *ref1)
  60 {
  61         if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
  62                 if (ref1->root < ref2->root)
  63                         return -1;
  64                 if (ref1->root > ref2->root)
  65                         return 1;
  66                 if (ref1->objectid < ref2->objectid)
  67                         return -1;
  68                 if (ref1->objectid > ref2->objectid)
  69                         return 1;
  70                 if (ref1->offset < ref2->offset)
  71                         return -1;
  72                 if (ref1->offset > ref2->offset)
  73                         return 1;
  74         } else {
  75                 if (ref1->parent < ref2->parent)
  76                         return -1;
  77                 if (ref1->parent > ref2->parent)
  78                         return 1;
  79         }
  80         return 0;
  81 }
  82
  83 /*
  84  * entries in the rb tree are ordered by the byte number of the extent,
  85  * type of the delayed backrefs and content of delayed backrefs.
  86  */
  87 static int comp_entry(struct btrfs_delayed_ref_node *ref2,
  88                       struct btrfs_delayed_ref_node *ref1)
  89 {
  90         if (ref1->bytenr < ref2->bytenr)
  91                 return -1;
  92         if (ref1->bytenr > ref2->bytenr)
  93                 return 1;
  94         if (ref1->is_head && ref2->is_head)
  95                 return 0;
  96         if (ref2->is_head)
  97                 return -1;
  98         if (ref1->is_head)
  99                 return 1;
 100         if (ref1->type < ref2->type)
 101                 return -1;
 102         if (ref1->type > ref2->type)
 103                 return 1;
 104         if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
 105             ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
 106                 return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
 107                                       btrfs_delayed_node_to_tree_ref(ref1));
 108         } else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
 109                    ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
 110                 return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
 111                                       btrfs_delayed_node_to_data_ref(ref1));
 112         }
 113         BUG();
 114         return 0;
 115 }
 116
 117 /*
 118  * insert a new ref into the rbtree.  This returns any existing refs
 119  * for the same (bytenr,parent) tuple, or NULL if the new node was properly
 120  * inserted.
 121  */
 122 static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
 123                                                   struct rb_node *node)
 124 {
 125         struct rb_node **p = &root->rb_node;
 126         struct rb_node *parent_node = NULL;
 127         struct btrfs_delayed_ref_node *entry;
 128         struct btrfs_delayed_ref_node *ins;
 129         int cmp;
 130
 131         ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
 132         while (*p) {
 133                 parent_node = *p;
 134                 entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
 135                                  rb_node);
 136
 137                 cmp = comp_entry(entry, ins);
 138                 if (cmp < 0)
 139                         p = &(*p)->rb_left;
 140                 else if (cmp > 0)
 141                         p = &(*p)->rb_right;
 142                 else
 143                         return entry;
 144         }
 145
 146         rb_link_node(node, parent_node, p);
 147         rb_insert_color(node, root);
 148         return NULL;
 149 }
 150
 151 /*
 152  * find an head entry based on bytenr. This returns the delayed ref
 153  * head if it was able to find one, or NULL if nothing was in that spot
 154  */
 155 static struct btrfs_delayed_ref_node *find_ref_head(struct rb_root *root,
 156                                   u64 bytenr,
 157                                   struct btrfs_delayed_ref_node **last)
 158 {
 159         struct rb_node *n = root->rb_node;
 160         struct btrfs_delayed_ref_node *entry;
 161         int cmp;
 162
 163         while (n) {
 164                 entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
 165                 WARN_ON(!entry->in_tree);
 166                 if (last)
 167                         *last = entry;
 168
 169                 if (bytenr < entry->bytenr)
 170                         cmp = -1;
 171                 else if (bytenr > entry->bytenr)
 172                         cmp = 1;
 173                 else if (!btrfs_delayed_ref_is_head(entry))
 174                         cmp = 1;
 175                 else
 176                         cmp = 0;
 177
 178                 if (cmp < 0)
 179                         n = n->rb_left;
 180                 else if (cmp > 0)
 181                         n = n->rb_right;
 182                 else
 183                         return entry;
 184         }
 185         return NULL;
 186 }
 187
 188 int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
 189                            struct btrfs_delayed_ref_head *head)
 190 {
 191         struct btrfs_delayed_ref_root *delayed_refs;
 192
 193         delayed_refs = &trans->transaction->delayed_refs;
 194         assert_spin_locked(&delayed_refs->lock);
 195         if (mutex_trylock(&head->mutex))
 196                 return 0;
 197
 198         atomic_inc(&head->node.refs);
 199         spin_unlock(&delayed_refs->lock);
 200
 201         mutex_lock(&head->mutex);
 202         spin_lock(&delayed_refs->lock);
 203         if (!head->node.in_tree) {
 204                 mutex_unlock(&head->mutex);
 205                 btrfs_put_delayed_ref(&head->node);
 206                 return -EAGAIN;
 207         }
 208         btrfs_put_delayed_ref(&head->node);
 209         return 0;
 210 }
 211
 212 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
 213                            struct list_head *cluster, u64 start)
 214 {
 215         int count = 0;
 216         struct btrfs_delayed_ref_root *delayed_refs;
 217         struct rb_node *node;
 218         struct btrfs_delayed_ref_node *ref;
 219         struct btrfs_delayed_ref_head *head;
 220
 221         delayed_refs = &trans->transaction->delayed_refs;
 222         if (start == 0) {
 223                 node = rb_first(&delayed_refs->root);
 224         } else {
 225                 ref = NULL;
 226                 find_ref_head(&delayed_refs->root, start, &ref);
 227                 if (ref) {
 228                         struct btrfs_delayed_ref_node *tmp;
 229
 230                         node = rb_prev(&ref->rb_node);
 231                         while (node) {
 232                                 tmp = rb_entry(node,
 233                                                struct btrfs_delayed_ref_node,
 234                                                rb_node);
 235                                 if (tmp->bytenr < start)
 236                                         break;
 237                                 ref = tmp;
 238                                 node = rb_prev(&ref->rb_node);
 239                         }
 240                         node = &ref->rb_node;
 241                 } else
 242                         node = rb_first(&delayed_refs->root);
 243         }
 244 again:
 245         while (node && count < 32) {
 246                 ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
 247                 if (btrfs_delayed_ref_is_head(ref)) {
 248                         head = btrfs_delayed_node_to_head(ref);
 249                         if (list_empty(&head->cluster)) {
 250                                 list_add_tail(&head->cluster, cluster);
 251                                 delayed_refs->run_delayed_start =
 252                                         head->node.bytenr;
 253                                 count++;
 254
 255                                 WARN_ON(delayed_refs->num_heads_ready == 0);
 256                                 delayed_refs->num_heads_ready--;
 257                         } else if (count) {
 258                                 /* the goal of the clustering is to find extents
 259                                  * that are likely to end up in the same extent
 260                                  * leaf on disk.  So, we don't want them spread
 261                                  * all over the tree.  Stop now if we've hit
 262                                  * a head that was already in use
 263                                  */
 264                                 break;
 265                         }
 266                 }
 267                 node = rb_next(node);
 268         }
 269         if (count) {
 270                 return 0;
 271         } else if (start) {
 272                 /*
 273                  * we've gone to the end of the rbtree without finding any
 274                  * clusters.  start from the beginning and try again
 275                  */
 276                 start = 0;
 277                 node = rb_first(&delayed_refs->root);
 278                 goto again;
 279         }
 280         return 1;
 281 }
 282
 283 /*
 284  * helper function to update an extent delayed ref in the
 285  * rbtree.  existing and update must both have the same
 286  * bytenr and parent
 287  *
 288  * This may free existing if the update cancels out whatever
 289  * operation it was doing.
 290  */
 291 static noinline void
 292 update_existing_ref(struct btrfs_trans_handle *trans,
 293                     struct btrfs_delayed_ref_root *delayed_refs,
 294                     struct btrfs_delayed_ref_node *existing,
 295                     struct btrfs_delayed_ref_node *update)
 296 {
 297         if (update->action != existing->action) {
 298                 /*
 299                  * this is effectively undoing either an add or a
 300                  * drop.  We decrement the ref_mod, and if it goes
 301                  * down to zero we just delete the entry without
 302                  * every changing the extent allocation tree.
 303                  */
 304                 existing->ref_mod--;
 305                 if (existing->ref_mod == 0) {
 306                         rb_erase(&existing->rb_node,
 307                                  &delayed_refs->root);
 308                         existing->in_tree = 0;
 309                         btrfs_put_delayed_ref(existing);
 310                         delayed_refs->num_entries--;
 311                         if (trans->delayed_ref_updates)
 312                                 trans->delayed_ref_updates--;
 313                 } else {
 314                         WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
 315                                 existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
 316                 }
 317         } else {
 318                 WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
 319                         existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
 320                 /*
 321                  * the action on the existing ref matches
 322                  * the action on the ref we're trying to add.
 323                  * Bump the ref_mod by one so the backref that
 324                  * is eventually added/removed has the correct
 325                  * reference count
 326                  */
 327                 existing->ref_mod += update->ref_mod;
 328         }
 329 }
 330
 331 /*
 332  * helper function to update the accounting in the head ref
 333  * existing and update must have the same bytenr
 334  */
 335 static noinline void
 336 update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
 337                          struct btrfs_delayed_ref_node *update)
 338 {
 339         struct btrfs_delayed_ref_head *existing_ref;
 340         struct btrfs_delayed_ref_head *ref;
 341
 342         existing_ref = btrfs_delayed_node_to_head(existing);
 343         ref = btrfs_delayed_node_to_head(update);
 344         BUG_ON(existing_ref->is_data != ref->is_data);
 345
 346         if (ref->must_insert_reserved) {
 347                 /* if the extent was freed and then
 348                  * reallocated before the delayed ref
 349                  * entries were processed, we can end up
 350                  * with an existing head ref without
 351                  * the must_insert_reserved flag set.
 352                  * Set it again here
 353                  */
 354                 existing_ref->must_insert_reserved = ref->must_insert_reserved;
 355
 356                 /*
 357                  * update the num_bytes so we make sure the accounting
 358                  * is done correctly
 359                  */
 360                 existing->num_bytes = update->num_bytes;
 361
 362         }
 363
 364         if (ref->extent_op) {
 365                 if (!existing_ref->extent_op) {
 366                         existing_ref->extent_op = ref->extent_op;
 367                 } else {
 368                         if (ref->extent_op->update_key) {
 369                                 memcpy(&existing_ref->extent_op->key,
 370                                        &ref->extent_op->key,
 371                                        sizeof(ref->extent_op->key));
 372                                 existing_ref->extent_op->update_key = 1;
 373                         }
 374                         if (ref->extent_op->update_flags) {
 375                                 existing_ref->extent_op->flags_to_set |=
 376                                         ref->extent_op->flags_to_set;
 377                                 existing_ref->extent_op->update_flags = 1;
 378                         }
 379                         kfree(ref->extent_op);
 380                 }
 381         }
 382         /*
 383          * update the reference mod on the head to reflect this new operation
 384          */
 385         existing->ref_mod += update->ref_mod;
 386 }
 387
 388 /*
 389  * helper function to actually insert a head node into the rbtree.
 390  * this does all the dirty work in terms of maintaining the correct
 391  * overall modification count.
 392  */
 393 static noinline int add_delayed_ref_head(struct btrfs_fs_info *fs_info,
 394                                         struct btrfs_trans_handle *trans,
 395                                         struct btrfs_delayed_ref_node *ref,
 396                                         u64 bytenr, u64 num_bytes,
 397                                         int action, int is_data)
 398 {
 399         struct btrfs_delayed_ref_node *existing;
 400         struct btrfs_delayed_ref_head *head_ref = NULL;
 401         struct btrfs_delayed_ref_root *delayed_refs;
 402         int count_mod = 1;
 403         int must_insert_reserved = 0;
 404
 405         /*
 406          * the head node stores the sum of all the mods, so dropping a ref
 407          * should drop the sum in the head node by one.
 408          */
 409         if (action == BTRFS_UPDATE_DELAYED_HEAD)
 410                 count_mod = 0;
 411         else if (action == BTRFS_DROP_DELAYED_REF)
 412                 count_mod = -1;
 413
 414         /*
 415          * BTRFS_ADD_DELAYED_EXTENT means that we need to update
 416          * the reserved accounting when the extent is finally added, or
 417          * if a later modification deletes the delayed ref without ever
 418          * inserting the extent into the extent allocation tree.
 419          * ref->must_insert_reserved is the flag used to record
 420          * that accounting mods are required.
 421          *
 422          * Once we record must_insert_reserved, switch the action to
 423          * BTRFS_ADD_DELAYED_REF because other special casing is not required.
 424          */
 425         if (action == BTRFS_ADD_DELAYED_EXTENT)
 426                 must_insert_reserved = 1;
 427         else
 428                 must_insert_reserved = 0;
 429
 430         delayed_refs = &trans->transaction->delayed_refs;
 431
 432         /* first set the basic ref node struct up */
 433         atomic_set(&ref->refs, 1);
 434         ref->bytenr = bytenr;
 435         ref->num_bytes = num_bytes;
 436         ref->ref_mod = count_mod;
 437         ref->type  = 0;
 438         ref->action  = 0;
 439         ref->is_head = 1;
 440         ref->in_tree = 1;
 441
 442         head_ref = btrfs_delayed_node_to_head(ref);
 443         head_ref->must_insert_reserved = must_insert_reserved;
 444         head_ref->is_data = is_data;
 445
 446         INIT_LIST_HEAD(&head_ref->cluster);
 447         mutex_init(&head_ref->mutex);
 448
 449         trace_btrfs_delayed_ref_head(ref, head_ref, action);
 450
 451         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 452
 453         if (existing) {
 454                 update_existing_head_ref(existing, ref);
 455                 /*
 456                  * we've updated the existing ref, free the newly
 457                  * allocated ref
 458                  */
 459                 kfree(ref);
 460         } else {
 461                 delayed_refs->num_heads++;
 462                 delayed_refs->num_heads_ready++;
 463                 delayed_refs->num_entries++;
 464                 trans->delayed_ref_updates++;
 465         }
 466         return 0;
 467 }
 468
 469 /*
 470  * helper to insert a delayed tree ref into the rbtree.
 471  */
 472 static noinline int add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
 473                                          struct btrfs_trans_handle *trans,
 474                                          struct btrfs_delayed_ref_node *ref,
 475                                          u64 bytenr, u64 num_bytes, u64 parent,
 476                                          u64 ref_root, int level, int action,
 477                                          int for_cow)
 478 {
 479         struct btrfs_delayed_ref_node *existing;
 480         struct btrfs_delayed_tree_ref *full_ref;
 481         struct btrfs_delayed_ref_root *delayed_refs;
 482
 483         if (action == BTRFS_ADD_DELAYED_EXTENT)
 484                 action = BTRFS_ADD_DELAYED_REF;
 485
 486         delayed_refs = &trans->transaction->delayed_refs;
 487
 488         /* first set the basic ref node struct up */
 489         atomic_set(&ref->refs, 1);
 490         ref->bytenr = bytenr;
 491         ref->num_bytes = num_bytes;
 492         ref->ref_mod = 1;
 493         ref->action = action;
 494         ref->is_head = 0;
 495         ref->in_tree = 1;
 496
 497         full_ref = btrfs_delayed_node_to_tree_ref(ref);
 498         full_ref->parent = parent;
 499         full_ref->root = ref_root;
 500         if (parent)
 501                 ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
 502         else
 503                 ref->type = BTRFS_TREE_BLOCK_REF_KEY;
 504         full_ref->level = level;
 505
 506         trace_btrfs_delayed_tree_ref(ref, full_ref, action);
 507
 508         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 509
 510         if (existing) {
 511                 update_existing_ref(trans, delayed_refs, existing, ref);
 512                 /*
 513                  * we've updated the existing ref, free the newly
 514                  * allocated ref
 515                  */
 516                 kfree(ref);
 517         } else {
 518                 delayed_refs->num_entries++;
 519                 trans->delayed_ref_updates++;
 520         }
 521         return 0;
 522 }
 523
 524 /*
 525  * helper to insert a delayed data ref into the rbtree.
 526  */
 527 static noinline int add_delayed_data_ref(struct btrfs_fs_info *fs_info,
 528                                          struct btrfs_trans_handle *trans,
 529                                          struct btrfs_delayed_ref_node *ref,
 530                                          u64 bytenr, u64 num_bytes, u64 parent,
 531                                          u64 ref_root, u64 owner, u64 offset,
 532                                          int action, int for_cow)
 533 {
 534         struct btrfs_delayed_ref_node *existing;
 535         struct btrfs_delayed_data_ref *full_ref;
 536         struct btrfs_delayed_ref_root *delayed_refs;
 537
 538         if (action == BTRFS_ADD_DELAYED_EXTENT)
 539                 action = BTRFS_ADD_DELAYED_REF;
 540
 541         delayed_refs = &trans->transaction->delayed_refs;
 542
 543         /* first set the basic ref node struct up */
 544         atomic_set(&ref->refs, 1);
 545         ref->bytenr = bytenr;
 546         ref->num_bytes = num_bytes;
 547         ref->ref_mod = 1;
 548         ref->action = action;
 549         ref->is_head = 0;
 550         ref->in_tree = 1;
 551
 552         full_ref = btrfs_delayed_node_to_data_ref(ref);
 553         full_ref->parent = parent;
 554         full_ref->root = ref_root;
 555         if (parent)
 556                 ref->type = BTRFS_SHARED_DATA_REF_KEY;
 557         else
 558                 ref->type = BTRFS_EXTENT_DATA_REF_KEY;
 559
 560         full_ref->objectid = owner;
 561         full_ref->offset = offset;
 562
 563         trace_btrfs_delayed_data_ref(ref, full_ref, action);
 564
 565         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 566
 567         if (existing) {
 568                 update_existing_ref(trans, delayed_refs, existing, ref);
 569                 /*
 570                  * we've updated the existing ref, free the newly
 571                  * allocated ref
 572                  */
 573                 kfree(ref);
 574         } else {
 575                 delayed_refs->num_entries++;
 576                 trans->delayed_ref_updates++;
 577         }
 578         return 0;
 579 }
 580
 581 /*
 582  * add a delayed tree ref.  This does all of the accounting required
 583  * to make sure the delayed ref is eventually processed before this
 584  * transaction commits.
 585  */
 586 int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
 587                                struct btrfs_trans_handle *trans,
 588                                u64 bytenr, u64 num_bytes, u64 parent,
 589                                u64 ref_root,  int level, int action,
 590                                struct btrfs_delayed_extent_op *extent_op,
 591                                int for_cow)
 592 {
 593         struct btrfs_delayed_tree_ref *ref;
 594         struct btrfs_delayed_ref_head *head_ref;
 595         struct btrfs_delayed_ref_root *delayed_refs;
 596         int ret;
 597
 598         BUG_ON(extent_op && extent_op->is_data);
 599         ref = kmalloc(sizeof(*ref), GFP_NOFS);
 600         if (!ref)
 601                 return -ENOMEM;
 602
 603         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
 604         if (!head_ref) {
 605                 kfree(ref);
 606                 return -ENOMEM;
 607         }
 608
 609         head_ref->extent_op = extent_op;
 610
 611         delayed_refs = &trans->transaction->delayed_refs;
 612         spin_lock(&delayed_refs->lock);
 613
 614         /*
 615          * insert both the head node and the new ref without dropping
 616          * the spin lock
 617          */
 618         ret = add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
 619                                    num_bytes, action, 0);
 620         BUG_ON(ret);
 621
 622         ret = add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
 623                                    num_bytes, parent, ref_root, level, action,
 624                                    for_cow);
 625         BUG_ON(ret);
 626         spin_unlock(&delayed_refs->lock);
 627         return 0;
 628 }
 629
 630 /*
 631  * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
 632  */
 633 int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
 634                                struct btrfs_trans_handle *trans,
 635                                u64 bytenr, u64 num_bytes,
 636                                u64 parent, u64 ref_root,
 637                                u64 owner, u64 offset, int action,
 638                                struct btrfs_delayed_extent_op *extent_op,
 639                                int for_cow)
 640 {
 641         struct btrfs_delayed_data_ref *ref;
 642         struct btrfs_delayed_ref_head *head_ref;
 643         struct btrfs_delayed_ref_root *delayed_refs;
 644         int ret;
 645
 646         BUG_ON(extent_op && !extent_op->is_data);
 647         ref = kmalloc(sizeof(*ref), GFP_NOFS);
 648         if (!ref)
 649                 return -ENOMEM;
 650
 651         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
 652         if (!head_ref) {
 653                 kfree(ref);
 654                 return -ENOMEM;
 655         }
 656
 657         head_ref->extent_op = extent_op;
 658
 659         delayed_refs = &trans->transaction->delayed_refs;
 660         spin_lock(&delayed_refs->lock);
 661
 662         /*
 663          * insert both the head node and the new ref without dropping
 664          * the spin lock
 665          */
 666         ret = add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
 667                                    num_bytes, action, 1);
 668         BUG_ON(ret);
 669
 670         ret = add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
 671                                    num_bytes, parent, ref_root, owner, offset,
 672                                    action, for_cow);
 673         BUG_ON(ret);
 674         spin_unlock(&delayed_refs->lock);
 675         return 0;
 676 }
 677
 678 int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
 679                                 struct btrfs_trans_handle *trans,
 680                                 u64 bytenr, u64 num_bytes,
 681                                 struct btrfs_delayed_extent_op *extent_op)
 682 {
 683         struct btrfs_delayed_ref_head *head_ref;
 684         struct btrfs_delayed_ref_root *delayed_refs;
 685         int ret;
 686
 687         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
 688         if (!head_ref)
 689                 return -ENOMEM;
 690
 691         head_ref->extent_op = extent_op;
 692
 693         delayed_refs = &trans->transaction->delayed_refs;
 694         spin_lock(&delayed_refs->lock);
 695
 696         ret = add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
 697                                    num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
 698                                    extent_op->is_data);
 699         BUG_ON(ret);
 700
 701         spin_unlock(&delayed_refs->lock);
 702         return 0;
 703 }
 704
 705 /*
 706  * this does a simple search for the head node for a given extent.
 707  * It must be called with the delayed ref spinlock held, and it returns
 708  * the head node if any where found, or NULL if not.
 709  */
 710 struct btrfs_delayed_ref_head *
 711 btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
 712 {
 713         struct btrfs_delayed_ref_node *ref;
 714         struct btrfs_delayed_ref_root *delayed_refs;
 715
 716         delayed_refs = &trans->transaction->delayed_refs;
 717         ref = find_ref_head(&delayed_refs->root, bytenr, NULL);
 718         if (ref)
 719                 return btrfs_delayed_node_to_head(ref);
 720         return NULL;
 721 }