sys/vfs/hammer/hammer_reblock.c

   1 /*
   2  * Copyright (c) 2008-2012 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34 /*
  35  * HAMMER reblocker - This code frees up fragmented physical space
  36  *
  37  * HAMMER only keeps track of free space on a big-block basis.  A big-block
  38  * containing holes can only be freed by migrating the remaining data in
  39  * that big-block into a new big-block, then freeing the big-block.
  40  *
  41  * This function is called from an ioctl or via the hammer support thread.
  42  */
  43
  44 #include "hammer.h"
  45
  46 static int hammer_reblock_helper(struct hammer_ioc_reblock *reblock,
  47                                  hammer_cursor_t cursor,
  48                                  hammer_btree_elm_t elm);
  49 static int hammer_reblock_data(struct hammer_ioc_reblock *reblock,
  50                                 hammer_cursor_t cursor, hammer_btree_elm_t elm);
  51 static int hammer_reblock_leaf_node(struct hammer_ioc_reblock *reblock,
  52                                 hammer_cursor_t cursor, hammer_btree_elm_t elm);
  53 static int hammer_reblock_int_node(struct hammer_ioc_reblock *reblock,
  54                                 hammer_cursor_t cursor, hammer_btree_elm_t elm);
  55
  56 int
  57 hammer_ioc_reblock(hammer_transaction_t trans, hammer_inode_t ip,
  58                    struct hammer_ioc_reblock *reblock)
  59 {
  60         struct hammer_cursor cursor;
  61         hammer_btree_elm_t elm;
  62         int checkspace_count;
  63         int error;
  64         int seq;
  65         int slop;
  66         u_int32_t key_end_localization;
  67
  68         if ((reblock->key_beg.localization | reblock->key_end.localization) &
  69             HAMMER_LOCALIZE_PSEUDOFS_MASK) {
  70                 return(EINVAL);
  71         }
  72         if (reblock->key_beg.obj_id >= reblock->key_end.obj_id)
  73                 return(EINVAL);
  74         if (reblock->free_level < 0 ||
  75             reblock->free_level > HAMMER_BIGBLOCK_SIZE)
  76                 return(EINVAL);
  77
  78         /*
  79          * A fill_percentage <= 20% is considered an emergency.  free_level is
  80          * inverted from fill_percentage.
  81          */
  82         if (reblock->free_level >= HAMMER_BIGBLOCK_SIZE * 8 / 10)
  83                 slop = HAMMER_CHKSPC_EMERGENCY;
  84         else
  85                 slop = HAMMER_CHKSPC_REBLOCK;
  86
  87         /*
  88          * Ioctl caller has only set localization type to reblock.
  89          * Initialize cursor key localization with ip localization.
  90          */
  91         reblock->key_cur = reblock->key_beg;
  92         reblock->key_cur.localization &= HAMMER_LOCALIZE_MASK;
  93         if (reblock->allpfs == 0)
  94                 reblock->key_cur.localization += ip->obj_localization;
  95
  96         key_end_localization = reblock->key_end.localization;
  97         key_end_localization &= HAMMER_LOCALIZE_MASK;
  98         if (reblock->allpfs == 0)
  99                 key_end_localization += ip->obj_localization;
 100         else
 101                 key_end_localization += ((HAMMER_MAX_PFS - 1) << 16);
 102
 103         checkspace_count = 0;
 104         seq = trans->hmp->flusher.done;
 105 retry:
 106         error = hammer_init_cursor(trans, &cursor, NULL, NULL);
 107         if (error) {
 108                 hammer_done_cursor(&cursor);
 109                 goto failed;
 110         }
 111         cursor.key_beg.localization = reblock->key_cur.localization;
 112         cursor.key_beg.obj_id = reblock->key_cur.obj_id;
 113         cursor.key_beg.key = HAMMER_MIN_KEY;
 114         cursor.key_beg.create_tid = 1;
 115         cursor.key_beg.delete_tid = 0;
 116         cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
 117         cursor.key_beg.obj_type = 0;
 118
 119         cursor.key_end.localization = key_end_localization;
 120         cursor.key_end.obj_id = reblock->key_end.obj_id;
 121         cursor.key_end.key = HAMMER_MAX_KEY;
 122         cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
 123         cursor.key_end.delete_tid = 0;
 124         cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
 125         cursor.key_end.obj_type = 0;
 126
 127         cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
 128         cursor.flags |= HAMMER_CURSOR_BACKEND;
 129         cursor.flags |= HAMMER_CURSOR_NOSWAPCACHE;
 130
 131         /*
 132          * This flag allows the btree scan code to return internal nodes,
 133          * so we can reblock them in addition to the leafs.  Only specify it
 134          * if we intend to reblock B-Tree nodes.
 135          */
 136         if (reblock->head.flags & HAMMER_IOC_DO_BTREE)
 137                 cursor.flags |= HAMMER_CURSOR_REBLOCKING;
 138
 139         error = hammer_btree_first(&cursor);
 140         while (error == 0) {
 141                 /*
 142                  * Internal or Leaf node
 143                  */
 144                 KKASSERT(cursor.index < cursor.node->ondisk->count);
 145                 elm = &cursor.node->ondisk->elms[cursor.index];
 146                 reblock->key_cur.obj_id = elm->base.obj_id;
 147                 reblock->key_cur.localization = elm->base.localization;
 148
 149                 /*
 150                  * Yield to more important tasks
 151                  */
 152                 if ((error = hammer_signal_check(trans->hmp)) != 0)
 153                         break;
 154
 155                 /*
 156                  * If there is insufficient free space it may be due to
 157                  * reserved big-blocks, which flushing might fix.
 158                  *
 159                  * We must force a retest in case the unlocked cursor is
 160                  * moved to the end of the leaf, or moved to an internal
 161                  * node.
 162                  *
 163                  * WARNING: See warnings in hammer_unlock_cursor() function.
 164                  */
 165                 if (hammer_checkspace(trans->hmp, slop)) {
 166                         if (++checkspace_count == 10) {
 167                                 error = ENOSPC;
 168                                 break;
 169                         }
 170                         hammer_unlock_cursor(&cursor);
 171                         cursor.flags |= HAMMER_CURSOR_RETEST;
 172                         hammer_flusher_wait(trans->hmp, seq);
 173                         hammer_lock_cursor(&cursor);
 174                         seq = hammer_flusher_async(trans->hmp, NULL);
 175                         goto skip;
 176                 }
 177
 178                 /*
 179                  * Acquiring the sync_lock prevents the operation from
 180                  * crossing a synchronization boundary.
 181                  *
 182                  * NOTE: cursor.node may have changed on return.
 183                  *
 184                  * WARNING: See warnings in hammer_unlock_cursor() function.
 185                  */
 186                 hammer_sync_lock_sh(trans);
 187                 error = hammer_reblock_helper(reblock, &cursor, elm);
 188                 hammer_sync_unlock(trans);
 189
 190                 while (hammer_flusher_meta_halflimit(trans->hmp) ||
 191                        hammer_flusher_undo_exhausted(trans, 2)) {
 192                         hammer_unlock_cursor(&cursor);
 193                         hammer_flusher_wait(trans->hmp, seq);
 194                         hammer_lock_cursor(&cursor);
 195                         seq = hammer_flusher_async_one(trans->hmp);
 196                 }
 197
 198                 /*
 199                  * Setup for iteration, our cursor flags may be modified by
 200                  * other threads while we are unlocked.
 201                  */
 202                 cursor.flags |= HAMMER_CURSOR_ATEDISK;
 203
 204                 /*
 205                  * We allocate data buffers, which atm we don't track
 206                  * dirty levels for because we allow the kernel to write
 207                  * them.  But if we allocate too many we can still deadlock
 208                  * the buffer cache.
 209                  *
 210                  * WARNING: See warnings in hammer_unlock_cursor() function.
 211                  *          (The cursor's node and element may change!)
 212                  */
 213                 if (bd_heatup()) {
 214                         hammer_unlock_cursor(&cursor);
 215                         bwillwrite(HAMMER_XBUFSIZE);
 216                         hammer_lock_cursor(&cursor);
 217                 }
 218                 vm_wait_nominal();
 219 skip:
 220                 if (error == 0) {
 221                         error = hammer_btree_iterate(&cursor);
 222                 }
 223         }
 224         if (error == ENOENT)
 225                 error = 0;
 226         hammer_done_cursor(&cursor);
 227         if (error == EWOULDBLOCK) {
 228                 hammer_flusher_sync(trans->hmp);
 229                 goto retry;
 230         }
 231         if (error == EDEADLK)
 232                 goto retry;
 233         if (error == EINTR) {
 234                 reblock->head.flags |= HAMMER_IOC_HEAD_INTR;
 235                 error = 0;
 236         }
 237 failed:
 238         reblock->key_cur.localization &= HAMMER_LOCALIZE_MASK;
 239         return(error);
 240 }
 241
 242 /*
 243  * Reblock the B-Tree (leaf) node, record, and/or data if necessary.
 244  *
 245  * XXX We have no visibility into internal B-Tree nodes at the moment,
 246  * only leaf nodes.
 247  */
 248 static int
 249 hammer_reblock_helper(struct hammer_ioc_reblock *reblock,
 250                       hammer_cursor_t cursor, hammer_btree_elm_t elm)
 251 {
 252         hammer_mount_t hmp;
 253         hammer_off_t tmp_offset;
 254         hammer_node_ondisk_t ondisk;
 255         struct hammer_btree_leaf_elm leaf;
 256         int error;
 257         int bytes;
 258         int cur;
 259         int iocflags;
 260
 261         error = 0;
 262         hmp = cursor->trans->hmp;
 263
 264         /*
 265          * Reblock data.  Note that data embedded in a record is reblocked
 266          * by the record reblock code.  Data processing only occurs at leaf
 267          * nodes and for RECORD element types.
 268          */
 269         if (cursor->node->ondisk->type != HAMMER_BTREE_TYPE_LEAF)
 270                 goto skip;
 271         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 272                 return(0);
 273         tmp_offset = elm->leaf.data_offset;
 274         if (tmp_offset == 0)
 275                 goto skip;
 276         if (error)
 277                 goto skip;
 278
 279         /*
 280          * NOTE: Localization restrictions may also have been set-up, we can't
 281          *       just set the match flags willy-nilly here.
 282          */
 283         switch(elm->leaf.base.rec_type) {
 284         case HAMMER_RECTYPE_INODE:
 285         case HAMMER_RECTYPE_SNAPSHOT:
 286         case HAMMER_RECTYPE_CONFIG:
 287                 iocflags = HAMMER_IOC_DO_INODES;
 288                 break;
 289         case HAMMER_RECTYPE_EXT:
 290         case HAMMER_RECTYPE_FIX:
 291         case HAMMER_RECTYPE_PFS:
 292         case HAMMER_RECTYPE_DIRENTRY:
 293                 iocflags = HAMMER_IOC_DO_DIRS;
 294                 break;
 295         case HAMMER_RECTYPE_DATA:
 296         case HAMMER_RECTYPE_DB:
 297                 iocflags = HAMMER_IOC_DO_DATA;
 298                 break;
 299         default:
 300                 iocflags = 0;
 301                 break;
 302         }
 303         if (reblock->head.flags & iocflags) {
 304                 ++reblock->data_count;
 305                 reblock->data_byte_count += elm->leaf.data_len;
 306                 bytes = hammer_blockmap_getfree(hmp, tmp_offset, &cur, &error);
 307                 if (hammer_debug_general & 0x4000)
 308                         kprintf("D %6d/%d\n", bytes, reblock->free_level);
 309                 if (error == 0 && (cur == 0 || reblock->free_level == 0) &&
 310                     bytes >= reblock->free_level) {
 311                         /*
 312                          * This is nasty, the uncache code may have to get
 313                          * vnode locks and because of that we can't hold
 314                          * the cursor locked.
 315                          *
 316                          * WARNING: See warnings in hammer_unlock_cursor()
 317                          *          function.
 318                          */
 319                         leaf = elm->leaf;
 320                         hammer_unlock_cursor(cursor);
 321                         hammer_io_direct_uncache(hmp, &leaf);
 322                         hammer_lock_cursor(cursor);
 323
 324                         /*
 325                          * elm may have become stale or invalid, reload it.
 326                          * ondisk variable is temporary only.  Note that
 327                          * cursor->node and thus cursor->node->ondisk may
 328                          * also changed.
 329                          */
 330                         ondisk = cursor->node->ondisk;
 331                         elm = &ondisk->elms[cursor->index];
 332                         if (cursor->flags & HAMMER_CURSOR_RETEST) {
 333                                 kprintf("hammer: debug: retest on "
 334                                         "reblocker uncache\n");
 335                                 error = EDEADLK;
 336                         } else if (ondisk->type != HAMMER_BTREE_TYPE_LEAF ||
 337                                    cursor->index >= ondisk->count) {
 338                                 kprintf("hammer: debug: shifted on "
 339                                         "reblocker uncache\n");
 340                                 error = EDEADLK;
 341                         } else if (bcmp(&elm->leaf, &leaf, sizeof(leaf))) {
 342                                 kprintf("hammer: debug: changed on "
 343                                         "reblocker uncache\n");
 344                                 error = EDEADLK;
 345                         }
 346                         if (error == 0)
 347                                 error = hammer_cursor_upgrade(cursor);
 348                         if (error == 0) {
 349                                 KKASSERT(cursor->index < ondisk->count);
 350                                 error = hammer_reblock_data(reblock,
 351                                                             cursor, elm);
 352                         }
 353                         if (error == 0) {
 354                                 ++reblock->data_moves;
 355                                 reblock->data_byte_moves += elm->leaf.data_len;
 356                         }
 357                 }
 358         }
 359
 360 skip:
 361         /*
 362          * Reblock a B-Tree internal or leaf node.  A leaf node is reblocked
 363          * on initial entry only (element 0).  An internal node is reblocked
 364          * when entered upward from its first leaf node only (also element 0).
 365          * Further revisits of the internal node (index > 0) are ignored.
 366          */
 367         tmp_offset = cursor->node->node_offset;
 368         if (cursor->index == 0 &&
 369             error == 0 && (reblock->head.flags & HAMMER_IOC_DO_BTREE)) {
 370                 ++reblock->btree_count;
 371                 bytes = hammer_blockmap_getfree(hmp, tmp_offset, &cur, &error);
 372                 if (hammer_debug_general & 0x4000)
 373                         kprintf("B %6d/%d\n", bytes, reblock->free_level);
 374                 if (error == 0 && (cur == 0 || reblock->free_level == 0) &&
 375                     bytes >= reblock->free_level) {
 376                         error = hammer_cursor_upgrade(cursor);
 377                         if (error == 0) {
 378                                 if (cursor->parent) {
 379                                         KKASSERT(cursor->parent_index <
 380                                                  cursor->parent->ondisk->count);
 381                                         elm = &cursor->parent->ondisk->elms[cursor->parent_index];
 382                                 } else {
 383                                         elm = NULL;
 384                                 }
 385                                 switch(cursor->node->ondisk->type) {
 386                                 case HAMMER_BTREE_TYPE_LEAF:
 387                                         error = hammer_reblock_leaf_node(
 388                                                         reblock, cursor, elm);
 389                                         break;
 390                                 case HAMMER_BTREE_TYPE_INTERNAL:
 391                                         error = hammer_reblock_int_node(
 392                                                         reblock, cursor, elm);
 393                                         break;
 394                                 default:
 395                                         panic("Illegal B-Tree node type");
 396                                 }
 397                         }
 398                         if (error == 0) {
 399                                 ++reblock->btree_moves;
 400                         }
 401                 }
 402         }
 403
 404         hammer_cursor_downgrade(cursor);
 405         return(error);
 406 }
 407
 408 /*
 409  * Reblock a record's data.  Both the B-Tree element and record pointers
 410  * to the data must be adjusted.
 411  */
 412 static int
 413 hammer_reblock_data(struct hammer_ioc_reblock *reblock,
 414                     hammer_cursor_t cursor, hammer_btree_elm_t elm)
 415 {
 416         struct hammer_buffer *data_buffer = NULL;
 417         hammer_off_t ndata_offset;
 418         int error;
 419         void *ndata;
 420
 421         error = hammer_btree_extract(cursor, HAMMER_CURSOR_GET_DATA |
 422                                              HAMMER_CURSOR_GET_LEAF);
 423         if (error)
 424                 return (error);
 425         ndata = hammer_alloc_data(cursor->trans, elm->leaf.data_len,
 426                                   elm->leaf.base.rec_type,
 427                                   &ndata_offset, &data_buffer,
 428                                   0, &error);
 429         if (error)
 430                 goto done;
 431         hammer_io_notmeta(data_buffer);
 432
 433         /*
 434          * Move the data.  Note that we must invalidate any cached
 435          * data buffer in the cursor before calling blockmap_free.
 436          * The blockmap_free may free up the entire big-block and
 437          * will not be able to invalidate it if the cursor is holding
 438          * a data buffer cached in that big-block.
 439          */
 440         hammer_modify_buffer_noundo(cursor->trans, data_buffer);
 441         bcopy(cursor->data, ndata, elm->leaf.data_len);
 442         hammer_modify_buffer_done(data_buffer);
 443         hammer_cursor_invalidate_cache(cursor);
 444
 445         hammer_blockmap_free(cursor->trans,
 446                              elm->leaf.data_offset, elm->leaf.data_len);
 447
 448         hammer_modify_node(cursor->trans, cursor->node,
 449                            &elm->leaf.data_offset, sizeof(hammer_off_t));
 450         elm->leaf.data_offset = ndata_offset;
 451         hammer_modify_node_done(cursor->node);
 452
 453 done:
 454         if (data_buffer)
 455                 hammer_rel_buffer(data_buffer, 0);
 456         return (error);
 457 }
 458
 459 /*
 460  * Reblock a B-Tree leaf node.  The parent must be adjusted to point to
 461  * the new copy of the leaf node.
 462  *
 463  * elm is a pointer to the parent element pointing at cursor.node.
 464  */
 465 static int
 466 hammer_reblock_leaf_node(struct hammer_ioc_reblock *reblock,
 467                          hammer_cursor_t cursor, hammer_btree_elm_t elm)
 468 {
 469         hammer_node_t onode;
 470         hammer_node_t nnode;
 471         int error;
 472
 473         /*
 474          * Don't supply a hint when allocating the leaf.  Fills are done
 475          * from the leaf upwards.
 476          */
 477         onode = cursor->node;
 478         nnode = hammer_alloc_btree(cursor->trans, 0, &error);
 479
 480         if (nnode == NULL)
 481                 return (error);
 482
 483         /*
 484          * Move the node
 485          */
 486         hammer_lock_ex(&nnode->lock);
 487         hammer_modify_node_noundo(cursor->trans, nnode);
 488         bcopy(onode->ondisk, nnode->ondisk, sizeof(*nnode->ondisk));
 489
 490         if (elm) {
 491                 /*
 492                  * We are not the root of the B-Tree
 493                  */
 494                 hammer_modify_node(cursor->trans, cursor->parent,
 495                                    &elm->internal.subtree_offset,
 496                                    sizeof(elm->internal.subtree_offset));
 497                 elm->internal.subtree_offset = nnode->node_offset;
 498                 hammer_modify_node_done(cursor->parent);
 499         } else {
 500                 /*
 501                  * We are the root of the B-Tree
 502                  */
 503                 hammer_volume_t volume;
 504                 volume = hammer_get_root_volume(cursor->trans->hmp, &error);
 505                 KKASSERT(error == 0);
 506
 507                 hammer_modify_volume_field(cursor->trans, volume,
 508                                            vol0_btree_root);
 509                 volume->ondisk->vol0_btree_root = nnode->node_offset;
 510                 hammer_modify_volume_done(volume);
 511                 hammer_rel_volume(volume, 0);
 512         }
 513
 514         hammer_cursor_replaced_node(onode, nnode);
 515         hammer_delete_node(cursor->trans, onode);
 516
 517         if (hammer_debug_general & 0x4000) {
 518                 kprintf("REBLOCK LNODE %016llx -> %016llx\n",
 519                         (long long)onode->node_offset,
 520                         (long long)nnode->node_offset);
 521         }
 522         hammer_modify_node_done(nnode);
 523         cursor->node = nnode;
 524
 525         hammer_unlock(&onode->lock);
 526         hammer_rel_node(onode);
 527
 528         return (error);
 529 }
 530
 531 /*
 532  * Reblock a B-Tree internal node.  The parent must be adjusted to point to
 533  * the new copy of the internal node, and the node's children's parent
 534  * pointers must also be adjusted to point to the new copy.
 535  *
 536  * elm is a pointer to the parent element pointing at cursor.node.
 537  */
 538 static int
 539 hammer_reblock_int_node(struct hammer_ioc_reblock *reblock,
 540                          hammer_cursor_t cursor, hammer_btree_elm_t elm)
 541 {
 542         struct hammer_node_lock lockroot;
 543         hammer_node_t onode;
 544         hammer_node_t nnode;
 545         int error;
 546         int i;
 547
 548         hammer_node_lock_init(&lockroot, cursor->node);
 549         error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
 550         if (error)
 551                 goto done;
 552
 553         onode = cursor->node;
 554         nnode = hammer_alloc_btree(cursor->trans, 0, &error);
 555
 556         if (nnode == NULL)
 557                 goto done;
 558
 559         /*
 560          * Move the node.  Adjust the parent's pointer to us first.
 561          */
 562         hammer_lock_ex(&nnode->lock);
 563         hammer_modify_node_noundo(cursor->trans, nnode);
 564         bcopy(onode->ondisk, nnode->ondisk, sizeof(*nnode->ondisk));
 565
 566         if (elm) {
 567                 /*
 568                  * We are not the root of the B-Tree
 569                  */
 570                 hammer_modify_node(cursor->trans, cursor->parent,
 571                                    &elm->internal.subtree_offset,
 572                                    sizeof(elm->internal.subtree_offset));
 573                 elm->internal.subtree_offset = nnode->node_offset;
 574                 hammer_modify_node_done(cursor->parent);
 575         } else {
 576                 /*
 577                  * We are the root of the B-Tree
 578                  */
 579                 hammer_volume_t volume;
 580                 volume = hammer_get_root_volume(cursor->trans->hmp, &error);
 581                 KKASSERT(error == 0);
 582
 583                 hammer_modify_volume_field(cursor->trans, volume,
 584                                            vol0_btree_root);
 585                 volume->ondisk->vol0_btree_root = nnode->node_offset;
 586                 hammer_modify_volume_done(volume);
 587                 hammer_rel_volume(volume, 0);
 588         }
 589
 590         /*
 591          * Now adjust our children's pointers to us.
 592          */
 593         for (i = 0; i < nnode->ondisk->count; ++i) {
 594                 elm = &nnode->ondisk->elms[i];
 595                 error = btree_set_parent(cursor->trans, nnode, elm);
 596                 if (error)
 597                         panic("reblock internal node: fixup problem");
 598         }
 599
 600         /*
 601          * Clean up.
 602          *
 603          * The new node replaces the current node in the cursor.  The cursor
 604          * expects it to be locked so leave it locked.  Discard onode.
 605          */
 606         hammer_cursor_replaced_node(onode, nnode);
 607         hammer_delete_node(cursor->trans, onode);
 608
 609         if (hammer_debug_general & 0x4000) {
 610                 kprintf("REBLOCK INODE %016llx -> %016llx\n",
 611                         (long long)onode->node_offset,
 612                         (long long)nnode->node_offset);
 613         }
 614         hammer_modify_node_done(nnode);
 615         cursor->node = nnode;
 616
 617         hammer_unlock(&onode->lock);
 618         hammer_rel_node(onode);
 619
 620 done:
 621         hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
 622         return (error);
 623 }
 624