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 static void hammer_move_node(hammer_cursor_t cursor, hammer_btree_elm_t elm,
  56                                 hammer_node_t onode, hammer_node_t nnode);
  57
  58 int
  59 hammer_ioc_reblock(hammer_transaction_t trans, hammer_inode_t ip,
  60                    struct hammer_ioc_reblock *reblock)
  61 {
  62         struct hammer_cursor cursor;
  63         hammer_btree_elm_t elm;
  64         int checkspace_count;
  65         int error;
  66         int seq;
  67         int slop;
  68         uint32_t key_end_localization;
  69
  70         if ((reblock->key_beg.localization | reblock->key_end.localization) &
  71             HAMMER_LOCALIZE_PSEUDOFS_MASK) {
  72                 return(EINVAL);
  73         }
  74         if (reblock->key_beg.obj_id >= reblock->key_end.obj_id)
  75                 return(EINVAL);
  76         if (reblock->free_level < 0 ||
  77             reblock->free_level > HAMMER_BIGBLOCK_SIZE)
  78                 return(EINVAL);
  79
  80         /*
  81          * A fill_percentage <= 20% is considered an emergency.  free_level is
  82          * inverted from fill_percentage.
  83          */
  84         if (reblock->free_level >= HAMMER_BIGBLOCK_SIZE * 8 / 10)
  85                 slop = HAMMER_CHKSPC_EMERGENCY;
  86         else
  87                 slop = HAMMER_CHKSPC_REBLOCK;
  88
  89         /*
  90          * Ioctl caller has only set localization type to reblock.
  91          * Initialize cursor key localization with ip localization.
  92          */
  93         reblock->key_cur = reblock->key_beg;
  94         reblock->key_cur.localization &= HAMMER_LOCALIZE_MASK;
  95         if (reblock->allpfs == 0)
  96                 reblock->key_cur.localization |= ip->obj_localization;
  97
  98         key_end_localization = reblock->key_end.localization;
  99         key_end_localization &= HAMMER_LOCALIZE_MASK;
 100         if (reblock->allpfs == 0)
 101                 key_end_localization |= ip->obj_localization;
 102         else
 103                 key_end_localization |= pfs_to_lo(HAMMER_MAX_PFSID);
 104
 105         checkspace_count = 0;
 106         seq = trans->hmp->flusher.done;
 107 retry:
 108         error = hammer_init_cursor(trans, &cursor, NULL, NULL);
 109         if (error) {
 110                 hammer_done_cursor(&cursor);
 111                 goto failed;
 112         }
 113         cursor.key_beg.localization = reblock->key_cur.localization;
 114         cursor.key_beg.obj_id = reblock->key_cur.obj_id;
 115         cursor.key_beg.key = HAMMER_MIN_KEY;
 116         cursor.key_beg.create_tid = 1;
 117         cursor.key_beg.delete_tid = 0;
 118         cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
 119         cursor.key_beg.obj_type = 0;
 120
 121         cursor.key_end.localization = key_end_localization;
 122         cursor.key_end.obj_id = reblock->key_end.obj_id;
 123         cursor.key_end.key = HAMMER_MAX_KEY;
 124         cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
 125         cursor.key_end.delete_tid = 0;
 126         cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
 127         cursor.key_end.obj_type = 0;
 128
 129         cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
 130         cursor.flags |= HAMMER_CURSOR_BACKEND;
 131         cursor.flags |= HAMMER_CURSOR_NOSWAPCACHE;
 132
 133         /*
 134          * This flag allows the btree scan code to return internal nodes,
 135          * so we can reblock them in addition to the leafs.  Only specify it
 136          * if we intend to reblock B-Tree nodes.
 137          */
 138         if (reblock->head.flags & HAMMER_IOC_DO_BTREE)
 139                 cursor.flags |= HAMMER_CURSOR_REBLOCKING;
 140
 141         error = hammer_btree_first(&cursor);
 142         while (error == 0) {
 143                 /*
 144                  * Internal or Leaf node
 145                  */
 146                 KKASSERT(cursor.index < cursor.node->ondisk->count);
 147                 elm = &cursor.node->ondisk->elms[cursor.index];
 148                 reblock->key_cur.obj_id = elm->base.obj_id;
 149                 reblock->key_cur.localization = elm->base.localization;
 150
 151                 /*
 152                  * Filesystem went read-only during rebalancing
 153                  */
 154                 if (trans->hmp->ronly) {
 155                         error = EROFS;
 156                         break;
 157                 }
 158
 159                 /*
 160                  * Yield to more important tasks
 161                  */
 162                 if ((error = hammer_signal_check(trans->hmp)) != 0)
 163                         break;
 164
 165                 /*
 166                  * If there is insufficient free space it may be due to
 167                  * reserved big-blocks, which flushing might fix.
 168                  *
 169                  * We must force a retest in case the unlocked cursor is
 170                  * moved to the end of the leaf, or moved to an internal
 171                  * node.
 172                  *
 173                  * WARNING: See warnings in hammer_unlock_cursor() function.
 174                  */
 175                 if (hammer_checkspace(trans->hmp, slop)) {
 176                         if (++checkspace_count == 10) {
 177                                 error = ENOSPC;
 178                                 break;
 179                         }
 180                         hammer_unlock_cursor(&cursor);
 181                         cursor.flags |= HAMMER_CURSOR_RETEST;
 182                         hammer_flusher_wait(trans->hmp, seq);
 183                         hammer_lock_cursor(&cursor);
 184                         seq = hammer_flusher_async(trans->hmp, NULL);
 185                         goto skip;
 186                 }
 187
 188                 /*
 189                  * Acquiring the sync_lock prevents the operation from
 190                  * crossing a synchronization boundary.
 191                  *
 192                  * NOTE: cursor.node may have changed on return.
 193                  *
 194                  * WARNING: See warnings in hammer_unlock_cursor() function.
 195                  */
 196                 hammer_sync_lock_sh(trans);
 197                 error = hammer_reblock_helper(reblock, &cursor, elm);
 198                 hammer_sync_unlock(trans);
 199
 200                 while (hammer_flusher_meta_halflimit(trans->hmp) ||
 201                        hammer_flusher_undo_exhausted(trans, 2)) {
 202                         hammer_unlock_cursor(&cursor);
 203                         hammer_flusher_wait(trans->hmp, seq);
 204                         hammer_lock_cursor(&cursor);
 205                         seq = hammer_flusher_async_one(trans->hmp);
 206                 }
 207
 208                 /*
 209                  * Setup for iteration, our cursor flags may be modified by
 210                  * other threads while we are unlocked.
 211                  */
 212                 cursor.flags |= HAMMER_CURSOR_ATEDISK;
 213
 214                 /*
 215                  * We allocate data buffers, which atm we don't track
 216                  * dirty levels for because we allow the kernel to write
 217                  * them.  But if we allocate too many we can still deadlock
 218                  * the buffer cache.
 219                  *
 220                  * WARNING: See warnings in hammer_unlock_cursor() function.
 221                  *          (The cursor's node and element may change!)
 222                  */
 223                 if (bd_heatup()) {
 224                         hammer_unlock_cursor(&cursor);
 225                         bwillwrite(HAMMER_XBUFSIZE);
 226                         hammer_lock_cursor(&cursor);
 227                 }
 228                 vm_wait_nominal();
 229 skip:
 230                 if (error == 0) {
 231                         error = hammer_btree_iterate(&cursor);
 232                 }
 233         }
 234         if (error == ENOENT)
 235                 error = 0;
 236         hammer_done_cursor(&cursor);
 237         if (error == EWOULDBLOCK) {
 238                 hammer_flusher_sync(trans->hmp);
 239                 goto retry;
 240         }
 241         if (error == EDEADLK)
 242                 goto retry;
 243         if (error == EINTR) {
 244                 reblock->head.flags |= HAMMER_IOC_HEAD_INTR;
 245                 error = 0;
 246         }
 247 failed:
 248         reblock->key_cur.localization &= HAMMER_LOCALIZE_MASK;
 249         return(error);
 250 }
 251
 252 /*
 253  * Reblock the B-Tree (leaf) node, record, and/or data if necessary.
 254  *
 255  * XXX We have no visibility into internal B-Tree nodes at the moment,
 256  * only leaf nodes.
 257  */
 258 static int
 259 hammer_reblock_helper(struct hammer_ioc_reblock *reblock,
 260                       hammer_cursor_t cursor, hammer_btree_elm_t elm)
 261 {
 262         hammer_mount_t hmp;
 263         hammer_off_t tmp_offset;
 264         hammer_node_ondisk_t ondisk;
 265         struct hammer_btree_leaf_elm leaf;
 266         int error;
 267         int bytes;
 268         int cur;
 269         int iocflags;
 270
 271         error = 0;
 272         hmp = cursor->trans->hmp;
 273
 274         /*
 275          * Reblock data.  Note that data embedded in a record is reblocked
 276          * by the record reblock code.  Data processing only occurs at leaf
 277          * nodes and for RECORD element types.
 278          */
 279         if (cursor->node->ondisk->type != HAMMER_BTREE_TYPE_LEAF)
 280                 goto skip;
 281         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 282                 return(EINVAL);
 283         tmp_offset = elm->leaf.data_offset;
 284         if (tmp_offset == 0)
 285                 goto skip;
 286
 287         /*
 288          * If reblock->vol_no is specified we only want to reblock data
 289          * in that volume, but ignore everything else.
 290          */
 291         if (reblock->vol_no != -1 &&
 292             reblock->vol_no != HAMMER_VOL_DECODE(tmp_offset))
 293                 goto skip;
 294
 295         /*
 296          * NOTE: Localization restrictions may also have been set-up, we can't
 297          *       just set the match flags willy-nilly here.
 298          */
 299         switch(elm->leaf.base.rec_type) {
 300         case HAMMER_RECTYPE_INODE:
 301         case HAMMER_RECTYPE_SNAPSHOT:
 302         case HAMMER_RECTYPE_CONFIG:
 303                 iocflags = HAMMER_IOC_DO_INODES;
 304                 break;
 305         case HAMMER_RECTYPE_EXT:
 306         case HAMMER_RECTYPE_FIX:
 307         case HAMMER_RECTYPE_PFS:
 308         case HAMMER_RECTYPE_DIRENTRY:
 309                 iocflags = HAMMER_IOC_DO_DIRS;
 310                 break;
 311         case HAMMER_RECTYPE_DATA:
 312         case HAMMER_RECTYPE_DB:
 313                 iocflags = HAMMER_IOC_DO_DATA;
 314                 break;
 315         default:
 316                 iocflags = 0;
 317                 break;
 318         }
 319         if (reblock->head.flags & iocflags) {
 320                 ++reblock->data_count;
 321                 reblock->data_byte_count += elm->leaf.data_len;
 322                 bytes = hammer_blockmap_getfree(hmp, tmp_offset, &cur, &error);
 323                 if (hammer_debug_general & 0x4000)
 324                         hdkprintf("D %6d/%d\n", bytes, reblock->free_level);
 325                 /*
 326                  * Start data reblock if
 327                  * 1. there is no error
 328                  * 2. the data and allocator offset are not in the same
 329                  *    big-block, or free level threshold is 0
 330                  * 3. free bytes in the data's big-block is larger than
 331                  *    free level threshold (means if threshold is 0 then
 332                  *    do reblock no matter what).
 333                  */
 334                 if (error == 0 && (cur == 0 || reblock->free_level == 0) &&
 335                     bytes >= reblock->free_level) {
 336                         /*
 337                          * This is nasty, the uncache code may have to get
 338                          * vnode locks and because of that we can't hold
 339                          * the cursor locked.
 340                          *
 341                          * WARNING: See warnings in hammer_unlock_cursor()
 342                          *          function.
 343                          */
 344                         leaf = elm->leaf;
 345                         hammer_unlock_cursor(cursor);
 346                         hammer_io_direct_uncache(hmp, &leaf);
 347                         hammer_lock_cursor(cursor);
 348
 349                         /*
 350                          * elm may have become stale or invalid, reload it.
 351                          * ondisk variable is temporary only.  Note that
 352                          * cursor->node and thus cursor->node->ondisk may
 353                          * also changed.
 354                          */
 355                         ondisk = cursor->node->ondisk;
 356                         elm = &ondisk->elms[cursor->index];
 357                         if (cursor->flags & HAMMER_CURSOR_RETEST) {
 358                                 hkprintf("debug: retest on reblocker uncache\n");
 359                                 error = EDEADLK;
 360                         } else if (ondisk->type != HAMMER_BTREE_TYPE_LEAF ||
 361                                    cursor->index >= ondisk->count) {
 362                                 hkprintf("debug: shifted on reblocker uncache\n");
 363                                 error = EDEADLK;
 364                         } else if (bcmp(&elm->leaf, &leaf, sizeof(leaf))) {
 365                                 hkprintf("debug: changed on reblocker uncache\n");
 366                                 error = EDEADLK;
 367                         }
 368                         if (error == 0)
 369                                 error = hammer_cursor_upgrade(cursor);
 370                         if (error == 0) {
 371                                 KKASSERT(cursor->index < ondisk->count);
 372                                 error = hammer_reblock_data(reblock,
 373                                                             cursor, elm);
 374                         }
 375                         if (error == 0) {
 376                                 ++reblock->data_moves;
 377                                 reblock->data_byte_moves += elm->leaf.data_len;
 378                         }
 379                 }
 380         }
 381
 382 skip:
 383         /*
 384          * Reblock a B-Tree internal or leaf node.  A leaf node is reblocked
 385          * on initial entry only (element 0).  An internal node is reblocked
 386          * when entered upward from its first leaf node only (also element 0,
 387          * see hammer_btree_iterate() where cursor moves up and may return).
 388          * Further revisits of the internal node (index > 0) are ignored.
 389          */
 390         tmp_offset = cursor->node->node_offset;
 391
 392         /*
 393          * If reblock->vol_no is specified we only want to reblock data
 394          * in that volume, but ignore everything else.
 395          */
 396         if (reblock->vol_no != -1 &&
 397             reblock->vol_no != HAMMER_VOL_DECODE(tmp_offset))
 398                 goto end;
 399
 400         if (cursor->index == 0 &&
 401             error == 0 && (reblock->head.flags & HAMMER_IOC_DO_BTREE)) {
 402                 ++reblock->btree_count;
 403                 bytes = hammer_blockmap_getfree(hmp, tmp_offset, &cur, &error);
 404                 if (hammer_debug_general & 0x4000)
 405                         hdkprintf("B %6d/%d\n", bytes, reblock->free_level);
 406                 /*
 407                  * Start node reblock if
 408                  * 1. there is no error
 409                  * 2. the node and allocator offset are not in the same
 410                  *    big-block, or free level threshold is 0
 411                  * 3. free bytes in the node's big-block is larger than
 412                  *    free level threshold (means if threshold is 0 then
 413                  *    do reblock no matter what).
 414                  */
 415                 if (error == 0 && (cur == 0 || reblock->free_level == 0) &&
 416                     bytes >= reblock->free_level) {
 417                         error = hammer_cursor_upgrade(cursor);
 418                         if (error == 0) {
 419                                 if (cursor->parent) {
 420                                         KKASSERT(cursor->parent_index <
 421                                                  cursor->parent->ondisk->count);
 422                                         elm = &cursor->parent->ondisk->elms[cursor->parent_index];
 423                                 } else {
 424                                         elm = NULL;
 425                                 }
 426                                 switch(cursor->node->ondisk->type) {
 427                                 case HAMMER_BTREE_TYPE_LEAF:
 428                                         error = hammer_reblock_leaf_node(
 429                                                         reblock, cursor, elm);
 430                                         break;
 431                                 case HAMMER_BTREE_TYPE_INTERNAL:
 432                                         error = hammer_reblock_int_node(
 433                                                         reblock, cursor, elm);
 434                                         break;
 435                                 default:
 436                                         hpanic("Illegal B-Tree node type");
 437                                 }
 438                         }
 439                         if (error == 0) {
 440                                 ++reblock->btree_moves;
 441                         }
 442                 }
 443         }
 444 end:
 445         hammer_cursor_downgrade(cursor);
 446         return(error);
 447 }
 448
 449 /*
 450  * Reblock a record's data.  Both the B-Tree element and record pointers
 451  * to the data must be adjusted.
 452  */
 453 static int
 454 hammer_reblock_data(struct hammer_ioc_reblock *reblock,
 455                     hammer_cursor_t cursor, hammer_btree_elm_t elm)
 456 {
 457         hammer_buffer_t data_buffer = NULL;
 458         hammer_off_t odata_offset;
 459         hammer_off_t ndata_offset;
 460         int error;
 461         void *ndata;
 462
 463         error = hammer_btree_extract_data(cursor);
 464         if (error)
 465                 return (error);
 466         ndata = hammer_alloc_data(cursor->trans, elm->leaf.data_len,
 467                                   elm->leaf.base.rec_type,
 468                                   &ndata_offset, &data_buffer,
 469                                   0, &error);
 470         if (error)
 471                 goto done;
 472         hammer_io_notmeta(data_buffer);
 473
 474         /*
 475          * Move the data.  Note that we must invalidate any cached
 476          * data buffer in the cursor before calling blockmap_free.
 477          * The blockmap_free may free up the entire big-block and
 478          * will not be able to invalidate it if the cursor is holding
 479          * a data buffer cached in that big-block.
 480          */
 481         hammer_modify_buffer_noundo(cursor->trans, data_buffer);
 482         bcopy(cursor->data, ndata, elm->leaf.data_len);
 483         hammer_modify_buffer_done(data_buffer);
 484         hammer_cursor_invalidate_cache(cursor);
 485
 486         hammer_blockmap_free(cursor->trans,
 487                              elm->leaf.data_offset, elm->leaf.data_len);
 488
 489         hammer_modify_node(cursor->trans, cursor->node,
 490                            &elm->leaf.data_offset, sizeof(hammer_off_t));
 491         odata_offset = elm->leaf.data_offset;
 492         elm->leaf.data_offset = ndata_offset;
 493         hammer_modify_node_done(cursor->node);
 494
 495         if (hammer_debug_general & 0x4000) {
 496                 hdkprintf("%08x %016jx -> %016jx\n",
 497                         (elm ? elm->base.localization : -1),
 498                         (intmax_t)odata_offset,
 499                         (intmax_t)ndata_offset);
 500         }
 501 done:
 502         if (data_buffer)
 503                 hammer_rel_buffer(data_buffer, 0);
 504         return (error);
 505 }
 506
 507 /*
 508  * Reblock a B-Tree leaf node.  The parent must be adjusted to point to
 509  * the new copy of the leaf node.
 510  *
 511  * elm is a pointer to the parent element pointing at cursor.node.
 512  */
 513 static int
 514 hammer_reblock_leaf_node(struct hammer_ioc_reblock *reblock,
 515                          hammer_cursor_t cursor, hammer_btree_elm_t elm)
 516 {
 517         hammer_node_t onode;
 518         hammer_node_t nnode;
 519         int error;
 520
 521         /*
 522          * Don't supply a hint when allocating the leaf.  Fills are done
 523          * from the leaf upwards.
 524          */
 525         onode = cursor->node;
 526         nnode = hammer_alloc_btree(cursor->trans, 0, &error);
 527
 528         if (nnode == NULL)
 529                 return (error);
 530
 531         hammer_lock_ex(&nnode->lock);
 532         hammer_modify_node_noundo(cursor->trans, nnode);
 533
 534         hammer_move_node(cursor, elm, onode, nnode);
 535
 536         /*
 537          * Clean up.
 538          *
 539          * The new node replaces the current node in the cursor.  The cursor
 540          * expects it to be locked so leave it locked.  Discard onode.
 541          */
 542         hammer_cursor_replaced_node(onode, nnode);
 543         hammer_delete_node(cursor->trans, onode);
 544
 545         if (hammer_debug_general & 0x4000) {
 546                 hdkprintf("%08x %016jx -> %016jx\n",
 547                         (elm ? elm->base.localization : -1),
 548                         (intmax_t)onode->node_offset,
 549                         (intmax_t)nnode->node_offset);
 550         }
 551         hammer_modify_node_done(nnode);
 552         cursor->node = nnode;
 553
 554         hammer_unlock(&onode->lock);
 555         hammer_rel_node(onode);
 556
 557         return (error);
 558 }
 559
 560 /*
 561  * Reblock a B-Tree internal node.  The parent must be adjusted to point to
 562  * the new copy of the internal node, and the node's children's parent
 563  * pointers must also be adjusted to point to the new copy.
 564  *
 565  * elm is a pointer to the parent element pointing at cursor.node.
 566  */
 567 static int
 568 hammer_reblock_int_node(struct hammer_ioc_reblock *reblock,
 569                          hammer_cursor_t cursor, hammer_btree_elm_t elm)
 570 {
 571         struct hammer_node_lock lockroot;
 572         hammer_node_t onode;
 573         hammer_node_t nnode;
 574         int error;
 575
 576         hammer_node_lock_init(&lockroot, cursor->node);
 577         error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
 578         if (error)
 579                 goto done;
 580
 581         /*
 582          * Don't supply a hint when allocating the leaf.  Fills are done
 583          * from the leaf upwards.
 584          */
 585         onode = cursor->node;
 586         nnode = hammer_alloc_btree(cursor->trans, 0, &error);
 587
 588         if (nnode == NULL)
 589                 goto done;
 590
 591         hammer_lock_ex(&nnode->lock);
 592         hammer_modify_node_noundo(cursor->trans, nnode);
 593
 594         hammer_move_node(cursor, elm, onode, nnode);
 595
 596         /*
 597          * Clean up.
 598          *
 599          * The new node replaces the current node in the cursor.  The cursor
 600          * expects it to be locked so leave it locked.  Discard onode.
 601          */
 602         hammer_cursor_replaced_node(onode, nnode);
 603         hammer_delete_node(cursor->trans, onode);
 604
 605         if (hammer_debug_general & 0x4000) {
 606                 hdkprintf("%08x %016jx -> %016jx\n",
 607                         (elm ? elm->base.localization : -1),
 608                         (intmax_t)onode->node_offset,
 609                         (intmax_t)nnode->node_offset);
 610         }
 611         hammer_modify_node_done(nnode);
 612         cursor->node = nnode;
 613
 614         hammer_unlock(&onode->lock);
 615         hammer_rel_node(onode);
 616
 617 done:
 618         hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
 619         return (error);
 620 }
 621
 622 /*
 623  * nnode is a newly allocated node, and now elm becomes the node
 624  * element within nnode's parent that represents a pointer to nnode,
 625  * or nnode becomes the root node if elm does not exist.
 626  */
 627 static void
 628 hammer_move_node(hammer_cursor_t cursor, hammer_btree_elm_t elm,
 629                  hammer_node_t onode, hammer_node_t nnode)
 630 {
 631         int error, i;
 632
 633         bcopy(onode->ondisk, nnode->ondisk, sizeof(*nnode->ondisk));
 634
 635         /*
 636          * Adjust the parent's pointer to us first.
 637          */
 638         if (elm) {
 639                 /*
 640                  * We are not the root of the B-Tree
 641                  */
 642                 KKASSERT(hammer_is_internal_node_elm(elm));
 643                 hammer_modify_node(cursor->trans, cursor->parent,
 644                                    &elm->internal.subtree_offset,
 645                                    sizeof(elm->internal.subtree_offset));
 646                 elm->internal.subtree_offset = nnode->node_offset;
 647                 hammer_modify_node_done(cursor->parent);
 648         } else {
 649                 /*
 650                  * We are the root of the B-Tree
 651                  */
 652                 hammer_volume_t volume;
 653                 volume = hammer_get_root_volume(cursor->trans->hmp, &error);
 654                 KKASSERT(error == 0);
 655
 656                 hammer_modify_volume_field(cursor->trans, volume,
 657                                            vol0_btree_root);
 658                 volume->ondisk->vol0_btree_root = nnode->node_offset;
 659                 hammer_modify_volume_done(volume);
 660                 hammer_rel_volume(volume, 0);
 661         }
 662
 663         /*
 664          * Now adjust our children's pointers to us
 665          * if we are an internal node.
 666          */
 667         if (nnode->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
 668                 for (i = 0; i < nnode->ondisk->count; ++i) {
 669                         error = btree_set_parent_of_child(cursor->trans, nnode,
 670                                         &nnode->ondisk->elms[i]);
 671                         if (error)
 672                                 hpanic("reblock internal node: fixup problem");
 673                 }
 674         }
 675 }