sys/vfs/hammer/hammer_btree.c

   1 /*
   2  * Copyright (c) 2007-2008 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 /*
  36  * HAMMER B-Tree index
  37  *
  38  * HAMMER implements a modified B+Tree.  In documentation this will
  39  * simply be refered to as the HAMMER B-Tree.  Basically a HAMMER B-Tree
  40  * looks like a B+Tree (A B-Tree which stores its records only at the leafs
  41  * of the tree), but adds two additional boundary elements which describe
  42  * the left-most and right-most element a node is able to represent.  In
  43  * otherwords, we have boundary elements at the two ends of a B-Tree node
  44  * instead of sub-tree pointers.
  45  *
  46  * A B-Tree internal node looks like this:
  47  *
  48  *      B N N N N N N B   <-- boundary and internal elements
  49  *       S S S S S S S    <-- subtree pointers
  50  *
  51  * A B-Tree leaf node basically looks like this:
  52  *
  53  *      L L L L L L L L   <-- leaf elemenets
  54  *
  55  * The radix for an internal node is 1 less then a leaf but we get a
  56  * number of significant benefits for our troubles.
  57  *
  58  * The big benefit to using a B-Tree containing boundary information
  59  * is that it is possible to cache pointers into the middle of the tree
  60  * and not have to start searches, insertions, OR deletions at the root
  61  * node.   In particular, searches are able to progress in a definitive
  62  * direction from any point in the tree without revisting nodes.  This
  63  * greatly improves the efficiency of many operations, most especially
  64  * record appends.
  65  *
  66  * B-Trees also make the stacking of trees fairly straightforward.
  67  *
  68  * INSERTIONS:  A search performed with the intention of doing
  69  * an insert will guarantee that the terminal leaf node is not full by
  70  * splitting full nodes.  Splits occur top-down during the dive down the
  71  * B-Tree.
  72  *
  73  * DELETIONS: A deletion makes no attempt to proactively balance the
  74  * tree and will recursively remove nodes that become empty.  If a
  75  * deadlock occurs a deletion may not be able to remove an empty leaf.
  76  * Deletions never allow internal nodes to become empty (that would blow
  77  * up the boundaries).
  78  */
  79 #include "hammer.h"
  80 #include <sys/buf.h>
  81 #include <sys/buf2.h>
  82
  83 static int btree_search(hammer_cursor_t cursor, int flags);
  84 static int btree_split_internal(hammer_cursor_t cursor);
  85 static int btree_split_leaf(hammer_cursor_t cursor);
  86 static int btree_remove(hammer_cursor_t cursor);
  87 static int btree_node_is_full(hammer_node_ondisk_t node);
  88 static int hammer_btree_mirror_propagate(hammer_cursor_t cursor,
  89                         hammer_tid_t mirror_tid);
  90 static void hammer_make_separator(hammer_base_elm_t key1,
  91                         hammer_base_elm_t key2, hammer_base_elm_t dest);
  92 static void hammer_cursor_mirror_filter(hammer_cursor_t cursor);
  93
  94 /*
  95  * Iterate records after a search.  The cursor is iterated forwards past
  96  * the current record until a record matching the key-range requirements
  97  * is found.  ENOENT is returned if the iteration goes past the ending
  98  * key.
  99  *
 100  * The iteration is inclusive of key_beg and can be inclusive or exclusive
 101  * of key_end depending on whether HAMMER_CURSOR_END_INCLUSIVE is set.
 102  *
 103  * When doing an as-of search (cursor->asof != 0), key_beg.create_tid
 104  * may be modified by B-Tree functions.
 105  *
 106  * cursor->key_beg may or may not be modified by this function during
 107  * the iteration.  XXX future - in case of an inverted lock we may have
 108  * to reinitiate the lookup and set key_beg to properly pick up where we
 109  * left off.
 110  *
 111  * If HAMMER_CURSOR_ITERATE_CHECK is set it is possible that the cursor
 112  * was reverse indexed due to being moved to a parent while unlocked,
 113  * and something else might have inserted an element outside the iteration
 114  * range.  When this case occurs the iterator just keeps iterating until
 115  * it gets back into the iteration range (instead of asserting).
 116  *
 117  * NOTE!  EDEADLK *CANNOT* be returned by this procedure.
 118  */
 119 int
 120 hammer_btree_iterate(hammer_cursor_t cursor)
 121 {
 122         hammer_node_ondisk_t node;
 123         hammer_btree_elm_t elm;
 124         hammer_mount_t hmp;
 125         int error = 0;
 126         int r;
 127         int s;
 128
 129         /*
 130          * Skip past the current record
 131          */
 132         hmp = cursor->trans->hmp;
 133         node = cursor->node->ondisk;
 134         if (node == NULL)
 135                 return(ENOENT);
 136         if (cursor->index < node->count &&
 137             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 138                 ++cursor->index;
 139         }
 140
 141         /*
 142          * HAMMER can wind up being cpu-bound.
 143          */
 144         if (++hmp->check_yield > hammer_yield_check) {
 145                 hmp->check_yield = 0;
 146                 lwkt_user_yield();
 147         }
 148
 149
 150         /*
 151          * Loop until an element is found or we are done.
 152          */
 153         for (;;) {
 154                 /*
 155                  * We iterate up the tree and then index over one element
 156                  * while we are at the last element in the current node.
 157                  *
 158                  * If we are at the root of the filesystem, cursor_up
 159                  * returns ENOENT.
 160                  *
 161                  * XXX this could be optimized by storing the information in
 162                  * the parent reference.
 163                  *
 164                  * XXX we can lose the node lock temporarily, this could mess
 165                  * up our scan.
 166                  */
 167                 ++hammer_stats_btree_iterations;
 168                 hammer_flusher_clean_loose_ios(hmp);
 169
 170                 if (cursor->index == node->count) {
 171                         if (hammer_debug_btree) {
 172                                 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
 173                                         (long long)cursor->node->node_offset,
 174                                         cursor->index,
 175                                         (long long)(cursor->parent ? cursor->parent->node_offset : -1),
 176                                         cursor->parent_index,
 177                                         curthread);
 178                         }
 179                         KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
 180                         error = hammer_cursor_up(cursor);
 181                         if (error)
 182                                 break;
 183                         /* reload stale pointer */
 184                         node = cursor->node->ondisk;
 185                         KKASSERT(cursor->index != node->count);
 186
 187                         /*
 188                          * If we are reblocking we want to return internal
 189                          * nodes.  Note that the internal node will be
 190                          * returned multiple times, on each upward recursion
 191                          * from its children.  The caller selects which
 192                          * revisit it cares about (usually first or last only).
 193                          */
 194                         if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
 195                                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 196                                 return(0);
 197                         }
 198                         ++cursor->index;
 199                         continue;
 200                 }
 201
 202                 /*
 203                  * Check internal or leaf element.  Determine if the record
 204                  * at the cursor has gone beyond the end of our range.
 205                  *
 206                  * We recurse down through internal nodes.
 207                  */
 208                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 209                         elm = &node->elms[cursor->index];
 210
 211                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 212                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 213                         if (hammer_debug_btree) {
 214                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
 215                                         (long long)cursor->node->node_offset,
 216                                         cursor->index,
 217                                         (long long)elm[0].internal.base.obj_id,
 218                                         elm[0].internal.base.rec_type,
 219                                         (long long)elm[0].internal.base.key,
 220                                         elm[0].internal.base.localization,
 221                                         r,
 222                                         curthread
 223                                 );
 224                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 225                                         (long long)cursor->node->node_offset,
 226                                         cursor->index + 1,
 227                                         (long long)elm[1].internal.base.obj_id,
 228                                         elm[1].internal.base.rec_type,
 229                                         (long long)elm[1].internal.base.key,
 230                                         elm[1].internal.base.localization,
 231                                         s
 232                                 );
 233                         }
 234
 235                         if (r < 0) {
 236                                 error = ENOENT;
 237                                 break;
 238                         }
 239                         if (r == 0 && (cursor->flags &
 240                                        HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 241                                 error = ENOENT;
 242                                 break;
 243                         }
 244
 245                         /*
 246                          * Better not be zero
 247                          */
 248                         KKASSERT(elm->internal.subtree_offset != 0);
 249
 250                         if (s <= 0) {
 251                                 /*
 252                                  * If running the mirror filter see if we
 253                                  * can skip one or more entire sub-trees.
 254                                  * If we can we return the internal node
 255                                  * and the caller processes the skipped
 256                                  * range (see mirror_read).
 257                                  */
 258                                 if (cursor->flags &
 259                                     HAMMER_CURSOR_MIRROR_FILTERED) {
 260                                         if (elm->internal.mirror_tid <
 261                                             cursor->cmirror->mirror_tid) {
 262                                                 hammer_cursor_mirror_filter(cursor);
 263                                                 return(0);
 264                                         }
 265                                 }
 266                         } else {
 267                                 /*
 268                                  * Normally it would be impossible for the
 269                                  * cursor to have gotten back-indexed,
 270                                  * but it can happen if a node is deleted
 271                                  * and the cursor is moved to its parent
 272                                  * internal node.  ITERATE_CHECK will be set.
 273                                  */
 274                                 KKASSERT(cursor->flags &
 275                                          HAMMER_CURSOR_ITERATE_CHECK);
 276                                 kprintf("hammer_btree_iterate: "
 277                                         "DEBUG: Caught parent seek "
 278                                         "in internal iteration\n");
 279                         }
 280
 281                         error = hammer_cursor_down(cursor);
 282                         if (error)
 283                                 break;
 284                         KKASSERT(cursor->index == 0);
 285                         /* reload stale pointer */
 286                         node = cursor->node->ondisk;
 287                         continue;
 288                 } else {
 289                         elm = &node->elms[cursor->index];
 290                         r = hammer_btree_cmp(&cursor->key_end, &elm->base);
 291                         if (hammer_debug_btree) {
 292                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 293                                         (long long)cursor->node->node_offset,
 294                                         cursor->index,
 295                                         (elm[0].leaf.base.btype ?
 296                                          elm[0].leaf.base.btype : '?'),
 297                                         (long long)elm[0].leaf.base.obj_id,
 298                                         elm[0].leaf.base.rec_type,
 299                                         (long long)elm[0].leaf.base.key,
 300                                         elm[0].leaf.base.localization,
 301                                         r
 302                                 );
 303                         }
 304                         if (r < 0) {
 305                                 error = ENOENT;
 306                                 break;
 307                         }
 308
 309                         /*
 310                          * We support both end-inclusive and
 311                          * end-exclusive searches.
 312                          */
 313                         if (r == 0 &&
 314                            (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 315                                 error = ENOENT;
 316                                 break;
 317                         }
 318
 319                         /*
 320                          * If ITERATE_CHECK is set an unlocked cursor may
 321                          * have been moved to a parent and the iterate can
 322                          * happen upon elements that are not in the requested
 323                          * range.
 324                          */
 325                         if (cursor->flags & HAMMER_CURSOR_ITERATE_CHECK) {
 326                                 s = hammer_btree_cmp(&cursor->key_beg,
 327                                                      &elm->base);
 328                                 if (s > 0) {
 329                                         kprintf("hammer_btree_iterate: "
 330                                                 "DEBUG: Caught parent seek "
 331                                                 "in leaf iteration\n");
 332                                         ++cursor->index;
 333                                         continue;
 334                                 }
 335                         }
 336                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 337
 338                         /*
 339                          * Return the element
 340                          */
 341                         switch(elm->leaf.base.btype) {
 342                         case HAMMER_BTREE_TYPE_RECORD:
 343                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 344                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 345                                         ++cursor->index;
 346                                         continue;
 347                                 }
 348                                 error = 0;
 349                                 break;
 350                         default:
 351                                 error = EINVAL;
 352                                 break;
 353                         }
 354                         if (error)
 355                                 break;
 356                 }
 357                 /*
 358                  * node pointer invalid after loop
 359                  */
 360
 361                 /*
 362                  * Return entry
 363                  */
 364                 if (hammer_debug_btree) {
 365                         int i = cursor->index;
 366                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 367                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 368                                 cursor->node, i,
 369                                 (long long)elm->internal.base.obj_id,
 370                                 elm->internal.base.rec_type,
 371                                 (long long)elm->internal.base.key,
 372                                 elm->internal.base.localization
 373                         );
 374                 }
 375                 return(0);
 376         }
 377         return(error);
 378 }
 379
 380 /*
 381  * We hit an internal element that we could skip as part of a mirroring
 382  * scan.  Calculate the entire range being skipped.
 383  *
 384  * It is important to include any gaps between the parent's left_bound
 385  * and the node's left_bound, and same goes for the right side.
 386  */
 387 static void
 388 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
 389 {
 390         struct hammer_cmirror *cmirror;
 391         hammer_node_ondisk_t ondisk;
 392         hammer_btree_elm_t elm;
 393
 394         ondisk = cursor->node->ondisk;
 395         cmirror = cursor->cmirror;
 396
 397         /*
 398          * Calculate the skipped range
 399          */
 400         elm = &ondisk->elms[cursor->index];
 401         if (cursor->index == 0)
 402                 cmirror->skip_beg = *cursor->left_bound;
 403         else
 404                 cmirror->skip_beg = elm->internal.base;
 405         while (cursor->index < ondisk->count) {
 406                 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
 407                         break;
 408                 ++cursor->index;
 409                 ++elm;
 410         }
 411         if (cursor->index == ondisk->count)
 412                 cmirror->skip_end = *cursor->right_bound;
 413         else
 414                 cmirror->skip_end = elm->internal.base;
 415
 416         /*
 417          * clip the returned result.
 418          */
 419         if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
 420                 cmirror->skip_beg = cursor->key_beg;
 421         if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
 422                 cmirror->skip_end = cursor->key_end;
 423 }
 424
 425 /*
 426  * Iterate in the reverse direction.  This is used by the pruning code to
 427  * avoid overlapping records.
 428  */
 429 int
 430 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
 431 {
 432         hammer_node_ondisk_t node;
 433         hammer_btree_elm_t elm;
 434         hammer_mount_t hmp;
 435         int error = 0;
 436         int r;
 437         int s;
 438
 439         /* mirror filtering not supported for reverse iteration */
 440         KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
 441
 442         /*
 443          * Skip past the current record.  For various reasons the cursor
 444          * may end up set to -1 or set to point at the end of the current
 445          * node.  These cases must be addressed.
 446          */
 447         node = cursor->node->ondisk;
 448         if (node == NULL)
 449                 return(ENOENT);
 450         if (cursor->index != -1 &&
 451             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 452                 --cursor->index;
 453         }
 454         if (cursor->index == cursor->node->ondisk->count)
 455                 --cursor->index;
 456
 457         /*
 458          * HAMMER can wind up being cpu-bound.
 459          */
 460         hmp = cursor->trans->hmp;
 461         if (++hmp->check_yield > hammer_yield_check) {
 462                 hmp->check_yield = 0;
 463                 lwkt_user_yield();
 464         }
 465
 466         /*
 467          * Loop until an element is found or we are done.
 468          */
 469         for (;;) {
 470                 ++hammer_stats_btree_iterations;
 471                 hammer_flusher_clean_loose_ios(hmp);
 472
 473                 /*
 474                  * We iterate up the tree and then index over one element
 475                  * while we are at the last element in the current node.
 476                  */
 477                 if (cursor->index == -1) {
 478                         error = hammer_cursor_up(cursor);
 479                         if (error) {
 480                                 cursor->index = 0; /* sanity */
 481                                 break;
 482                         }
 483                         /* reload stale pointer */
 484                         node = cursor->node->ondisk;
 485                         KKASSERT(cursor->index != node->count);
 486                         --cursor->index;
 487                         continue;
 488                 }
 489
 490                 /*
 491                  * Check internal or leaf element.  Determine if the record
 492                  * at the cursor has gone beyond the end of our range.
 493                  *
 494                  * We recurse down through internal nodes.
 495                  */
 496                 KKASSERT(cursor->index != node->count);
 497                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 498                         elm = &node->elms[cursor->index];
 499                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 500                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 501                         if (hammer_debug_btree) {
 502                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 503                                         (long long)cursor->node->node_offset,
 504                                         cursor->index,
 505                                         (long long)elm[0].internal.base.obj_id,
 506                                         elm[0].internal.base.rec_type,
 507                                         (long long)elm[0].internal.base.key,
 508                                         elm[0].internal.base.localization,
 509                                         r
 510                                 );
 511                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 512                                         (long long)cursor->node->node_offset,
 513                                         cursor->index + 1,
 514                                         (long long)elm[1].internal.base.obj_id,
 515                                         elm[1].internal.base.rec_type,
 516                                         (long long)elm[1].internal.base.key,
 517                                         elm[1].internal.base.localization,
 518                                         s
 519                                 );
 520                         }
 521
 522                         if (s >= 0) {
 523                                 error = ENOENT;
 524                                 break;
 525                         }
 526
 527                         /*
 528                          * It shouldn't be possible to be seeked past key_end,
 529                          * even if the cursor got moved to a parent.
 530                          */
 531                         KKASSERT(r >= 0);
 532
 533                         /*
 534                          * Better not be zero
 535                          */
 536                         KKASSERT(elm->internal.subtree_offset != 0);
 537
 538                         error = hammer_cursor_down(cursor);
 539                         if (error)
 540                                 break;
 541                         KKASSERT(cursor->index == 0);
 542                         /* reload stale pointer */
 543                         node = cursor->node->ondisk;
 544
 545                         /* this can assign -1 if the leaf was empty */
 546                         cursor->index = node->count - 1;
 547                         continue;
 548                 } else {
 549                         elm = &node->elms[cursor->index];
 550                         s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
 551                         if (hammer_debug_btree) {
 552                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 553                                         (long long)cursor->node->node_offset,
 554                                         cursor->index,
 555                                         (elm[0].leaf.base.btype ?
 556                                          elm[0].leaf.base.btype : '?'),
 557                                         (long long)elm[0].leaf.base.obj_id,
 558                                         elm[0].leaf.base.rec_type,
 559                                         (long long)elm[0].leaf.base.key,
 560                                         elm[0].leaf.base.localization,
 561                                         s
 562                                 );
 563                         }
 564                         if (s > 0) {
 565                                 error = ENOENT;
 566                                 break;
 567                         }
 568
 569                         /*
 570                          * It shouldn't be possible to be seeked past key_end,
 571                          * even if the cursor got moved to a parent.
 572                          */
 573                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 574
 575                         /*
 576                          * Return the element
 577                          */
 578                         switch(elm->leaf.base.btype) {
 579                         case HAMMER_BTREE_TYPE_RECORD:
 580                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 581                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 582                                         --cursor->index;
 583                                         continue;
 584                                 }
 585                                 error = 0;
 586                                 break;
 587                         default:
 588                                 error = EINVAL;
 589                                 break;
 590                         }
 591                         if (error)
 592                                 break;
 593                 }
 594                 /*
 595                  * node pointer invalid after loop
 596                  */
 597
 598                 /*
 599                  * Return entry
 600                  */
 601                 if (hammer_debug_btree) {
 602                         int i = cursor->index;
 603                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 604                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 605                                 cursor->node, i,
 606                                 (long long)elm->internal.base.obj_id,
 607                                 elm->internal.base.rec_type,
 608                                 (long long)elm->internal.base.key,
 609                                 elm->internal.base.localization
 610                         );
 611                 }
 612                 return(0);
 613         }
 614         return(error);
 615 }
 616
 617 /*
 618  * Lookup cursor->key_beg.  0 is returned on success, ENOENT if the entry
 619  * could not be found, EDEADLK if inserting and a retry is needed, and a
 620  * fatal error otherwise.  When retrying, the caller must terminate the
 621  * cursor and reinitialize it.  EDEADLK cannot be returned if not inserting.
 622  *
 623  * The cursor is suitably positioned for a deletion on success, and suitably
 624  * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
 625  * specified.
 626  *
 627  * The cursor may begin anywhere, the search will traverse the tree in
 628  * either direction to locate the requested element.
 629  *
 630  * Most of the logic implementing historical searches is handled here.  We
 631  * do an initial lookup with create_tid set to the asof TID.  Due to the
 632  * way records are laid out, a backwards iteration may be required if
 633  * ENOENT is returned to locate the historical record.  Here's the
 634  * problem:
 635  *
 636  * create_tid:    10      15       20
 637  *                   LEAF1   LEAF2
 638  * records:         (11)        (18)
 639  *
 640  * Lets say we want to do a lookup AS-OF timestamp 17.  We will traverse
 641  * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
 642  * not visible and thus causes ENOENT to be returned.  We really need
 643  * to check record 11 in LEAF1.  If it also fails then the search fails
 644  * (e.g. it might represent the range 11-16 and thus still not match our
 645  * AS-OF timestamp of 17).  Note that LEAF1 could be empty, requiring
 646  * further iterations.
 647  *
 648  * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
 649  * and the cursor->create_check TID if an iteration might be needed.
 650  * In the above example create_check would be set to 14.
 651  */
 652 int
 653 hammer_btree_lookup(hammer_cursor_t cursor)
 654 {
 655         int error;
 656
 657         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 658         KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
 659                   cursor->trans->sync_lock_refs > 0);
 660         ++hammer_stats_btree_lookups;
 661         if (cursor->flags & HAMMER_CURSOR_ASOF) {
 662                 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
 663                 cursor->key_beg.create_tid = cursor->asof;
 664                 for (;;) {
 665                         cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
 666                         error = btree_search(cursor, 0);
 667                         if (error != ENOENT ||
 668                             (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
 669                                 /*
 670                                  * Stop if no error.
 671                                  * Stop if error other then ENOENT.
 672                                  * Stop if ENOENT and not special case.
 673                                  */
 674                                 break;
 675                         }
 676                         if (hammer_debug_btree) {
 677                                 kprintf("CREATE_CHECK %016llx\n",
 678                                         (long long)cursor->create_check);
 679                         }
 680                         cursor->key_beg.create_tid = cursor->create_check;
 681                         /* loop */
 682                 }
 683         } else {
 684                 error = btree_search(cursor, 0);
 685         }
 686         if (error == 0)
 687                 error = hammer_btree_extract(cursor, cursor->flags);
 688         return(error);
 689 }
 690
 691 /*
 692  * Execute the logic required to start an iteration.  The first record
 693  * located within the specified range is returned and iteration control
 694  * flags are adjusted for successive hammer_btree_iterate() calls.
 695  *
 696  * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
 697  * in a loop without worrying about it.  Higher-level merged searches will
 698  * adjust the flag appropriately.
 699  */
 700 int
 701 hammer_btree_first(hammer_cursor_t cursor)
 702 {
 703         int error;
 704
 705         error = hammer_btree_lookup(cursor);
 706         if (error == ENOENT) {
 707                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 708                 error = hammer_btree_iterate(cursor);
 709         }
 710         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 711         return(error);
 712 }
 713
 714 /*
 715  * Similarly but for an iteration in the reverse direction.
 716  *
 717  * Set ATEDISK when iterating backwards to skip the current entry,
 718  * which after an ENOENT lookup will be pointing beyond our end point.
 719  *
 720  * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
 721  * in a loop without worrying about it.  Higher-level merged searches will
 722  * adjust the flag appropriately.
 723  */
 724 int
 725 hammer_btree_last(hammer_cursor_t cursor)
 726 {
 727         struct hammer_base_elm save;
 728         int error;
 729
 730         save = cursor->key_beg;
 731         cursor->key_beg = cursor->key_end;
 732         error = hammer_btree_lookup(cursor);
 733         cursor->key_beg = save;
 734         if (error == ENOENT ||
 735             (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 736                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 737                 error = hammer_btree_iterate_reverse(cursor);
 738         }
 739         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 740         return(error);
 741 }
 742
 743 /*
 744  * Extract the record and/or data associated with the cursor's current
 745  * position.  Any prior record or data stored in the cursor is replaced.
 746  * The cursor must be positioned at a leaf node.
 747  *
 748  * NOTE: All extractions occur at the leaf of the B-Tree.
 749  */
 750 int
 751 hammer_btree_extract(hammer_cursor_t cursor, int flags)
 752 {
 753         hammer_node_ondisk_t node;
 754         hammer_btree_elm_t elm;
 755         hammer_off_t data_off;
 756         hammer_mount_t hmp;
 757         int32_t data_len;
 758         int error;
 759
 760         /*
 761          * The case where the data reference resolves to the same buffer
 762          * as the record reference must be handled.
 763          */
 764         node = cursor->node->ondisk;
 765         elm = &node->elms[cursor->index];
 766         cursor->data = NULL;
 767         hmp = cursor->node->hmp;
 768
 769         /*
 770          * There is nothing to extract for an internal element.
 771          */
 772         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 773                 return(EINVAL);
 774
 775         /*
 776          * Only record types have data.
 777          */
 778         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 779         cursor->leaf = &elm->leaf;
 780
 781         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 782                 return(0);
 783         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 784                 return(0);
 785         data_off = elm->leaf.data_offset;
 786         data_len = elm->leaf.data_len;
 787         if (data_off == 0)
 788                 return(0);
 789
 790         /*
 791          * Load the data
 792          */
 793         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 794         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 795                                         &error, &cursor->data_buffer);
 796
 797         /*
 798          * Mark the data buffer as not being meta-data if it isn't
 799          * meta-data (sometimes bulk data is accessed via a volume
 800          * block device).
 801          */
 802         if (error == 0) {
 803                 switch(elm->leaf.base.rec_type) {
 804                 case HAMMER_RECTYPE_DATA:
 805                 case HAMMER_RECTYPE_DB:
 806                         if ((data_off & HAMMER_ZONE_LARGE_DATA) == 0)
 807                                 break;
 808                         if (hammer_double_buffer == 0 ||
 809                             (cursor->flags & HAMMER_CURSOR_NOSWAPCACHE)) {
 810                                 hammer_io_notmeta(cursor->data_buffer);
 811                         }
 812                         break;
 813                 default:
 814                         break;
 815                 }
 816         }
 817
 818         /*
 819          * Deal with CRC errors on the extracted data.
 820          */
 821         if (error == 0 &&
 822             hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 823                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 824                         (long long)elm->leaf.data_offset, elm->leaf.data_len);
 825                 if (hammer_debug_critical)
 826                         Debugger("CRC FAILED: DATA");
 827                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 828                         error = EDOM;   /* less critical (mirroring) */
 829                 else
 830                         error = EIO;    /* critical */
 831         }
 832         return(error);
 833 }
 834
 835
 836 /*
 837  * Insert a leaf element into the B-Tree at the current cursor position.
 838  * The cursor is positioned such that the element at and beyond the cursor
 839  * are shifted to make room for the new record.
 840  *
 841  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 842  * flag set and that call must return ENOENT before this function can be
 843  * called.
 844  *
 845  * The caller may depend on the cursor's exclusive lock after return to
 846  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 847  *
 848  * ENOSPC is returned if there is no room to insert a new record.
 849  */
 850 int
 851 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 852                     int *doprop)
 853 {
 854         hammer_node_ondisk_t node;
 855         int i;
 856         int error;
 857
 858         *doprop = 0;
 859         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 860                 return(error);
 861         ++hammer_stats_btree_inserts;
 862
 863         /*
 864          * Insert the element at the leaf node and update the count in the
 865          * parent.  It is possible for parent to be NULL, indicating that
 866          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 867          * possible.  The root inode can never be deleted so the leaf should
 868          * never be empty.
 869          *
 870          * Remember that the right-hand boundary is not included in the
 871          * count.
 872          */
 873         hammer_modify_node_all(cursor->trans, cursor->node);
 874         node = cursor->node->ondisk;
 875         i = cursor->index;
 876         KKASSERT(elm->base.btype != 0);
 877         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 878         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 879         if (i != node->count) {
 880                 bcopy(&node->elms[i], &node->elms[i+1],
 881                       (node->count - i) * sizeof(*elm));
 882         }
 883         node->elms[i].leaf = *elm;
 884         ++node->count;
 885         hammer_cursor_inserted_element(cursor->node, i);
 886
 887         /*
 888          * Update the leaf node's aggregate mirror_tid for mirroring
 889          * support.
 890          */
 891         if (node->mirror_tid < elm->base.delete_tid) {
 892                 node->mirror_tid = elm->base.delete_tid;
 893                 *doprop = 1;
 894         }
 895         if (node->mirror_tid < elm->base.create_tid) {
 896                 node->mirror_tid = elm->base.create_tid;
 897                 *doprop = 1;
 898         }
 899         hammer_modify_node_done(cursor->node);
 900
 901         /*
 902          * Debugging sanity checks.
 903          */
 904         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 905         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 906         if (i) {
 907                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 908         }
 909         if (i != node->count - 1)
 910                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 911
 912         return(0);
 913 }
 914
 915 /*
 916  * Delete a record from the B-Tree at the current cursor position.
 917  * The cursor is positioned such that the current element is the one
 918  * to be deleted.
 919  *
 920  * On return the cursor will be positioned after the deleted element and
 921  * MAY point to an internal node.  It will be suitable for the continuation
 922  * of an iteration but not for an insertion or deletion.
 923  *
 924  * Deletions will attempt to partially rebalance the B-Tree in an upward
 925  * direction, but will terminate rather then deadlock.  Empty internal nodes
 926  * are never allowed by a deletion which deadlocks may end up giving us an
 927  * empty leaf.  The pruner will clean up and rebalance the tree.
 928  *
 929  * This function can return EDEADLK, requiring the caller to retry the
 930  * operation after clearing the deadlock.
 931  */
 932 int
 933 hammer_btree_delete(hammer_cursor_t cursor)
 934 {
 935         hammer_node_ondisk_t ondisk;
 936         hammer_node_t node;
 937         hammer_node_t parent __debugvar;
 938         int error;
 939         int i;
 940
 941         KKASSERT (cursor->trans->sync_lock_refs > 0);
 942         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 943                 return(error);
 944         ++hammer_stats_btree_deletes;
 945
 946         /*
 947          * Delete the element from the leaf node.
 948          *
 949          * Remember that leaf nodes do not have boundaries.
 950          */
 951         node = cursor->node;
 952         ondisk = node->ondisk;
 953         i = cursor->index;
 954
 955         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 956         KKASSERT(i >= 0 && i < ondisk->count);
 957         hammer_modify_node_all(cursor->trans, node);
 958         if (i + 1 != ondisk->count) {
 959                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 960                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 961         }
 962         --ondisk->count;
 963         hammer_modify_node_done(node);
 964         hammer_cursor_deleted_element(node, i);
 965
 966         /*
 967          * Validate local parent
 968          */
 969         if (ondisk->parent) {
 970                 parent = cursor->parent;
 971
 972                 KKASSERT(parent != NULL);
 973                 KKASSERT(parent->node_offset == ondisk->parent);
 974         }
 975
 976         /*
 977          * If the leaf becomes empty it must be detached from the parent,
 978          * potentially recursing through to the filesystem root.
 979          *
 980          * This may reposition the cursor at one of the parent's of the
 981          * current node.
 982          *
 983          * Ignore deadlock errors, that simply means that btree_remove
 984          * was unable to recurse and had to leave us with an empty leaf.
 985          */
 986         KKASSERT(cursor->index <= ondisk->count);
 987         if (ondisk->count == 0) {
 988                 error = btree_remove(cursor);
 989                 if (error == EDEADLK)
 990                         error = 0;
 991         } else {
 992                 error = 0;
 993         }
 994         KKASSERT(cursor->parent == NULL ||
 995                  cursor->parent_index < cursor->parent->ondisk->count);
 996         return(error);
 997 }
 998
 999 /*
1000  * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
1001  *
1002  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
1003  *
1004  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
1005  * iterates up the tree as necessary to properly position itself prior to
1006  * actually doing the sarch.
1007  *
1008  * INSERTIONS: The search will split full nodes and leaves on its way down
1009  * and guarentee that the leaf it ends up on is not full.  If we run out
1010  * of space the search continues to the leaf (to position the cursor for
1011  * the spike), but ENOSPC is returned.
1012  *
1013  * The search is only guarenteed to end up on a leaf if an error code of 0
1014  * is returned, or if inserting and an error code of ENOENT is returned.
1015  * Otherwise it can stop at an internal node.  On success a search returns
1016  * a leaf node.
1017  *
1018  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
1019  * filesystem, and it is not simple code.  Please note the following facts:
1020  *
1021  * - Internal node recursions have a boundary on the left AND right.  The
1022  *   right boundary is non-inclusive.  The create_tid is a generic part
1023  *   of the key for internal nodes.
1024  *
1025  * - Leaf nodes contain terminal elements only now.
1026  *
1027  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
1028  *   historical search.  ASOF and INSERT are mutually exclusive.  When
1029  *   doing an as-of lookup btree_search() checks for a right-edge boundary
1030  *   case.  If while recursing down the left-edge differs from the key
1031  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
1032  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
1033  *   The iteration backwards because as-of searches can wind up going
1034  *   down the wrong branch of the B-Tree.
1035  */
1036 static
1037 int
1038 btree_search(hammer_cursor_t cursor, int flags)
1039 {
1040         hammer_node_ondisk_t node;
1041         hammer_btree_elm_t elm;
1042         int error;
1043         int enospc = 0;
1044         int i;
1045         int r;
1046         int s;
1047
1048         flags |= cursor->flags;
1049         ++hammer_stats_btree_searches;
1050
1051         if (hammer_debug_btree) {
1052                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
1053                         (long long)cursor->node->node_offset,
1054                         cursor->index,
1055                         (long long)cursor->key_beg.obj_id,
1056                         cursor->key_beg.rec_type,
1057                         (long long)cursor->key_beg.key,
1058                         (long long)cursor->key_beg.create_tid,
1059                         cursor->key_beg.localization,
1060                         curthread
1061                 );
1062                 if (cursor->parent)
1063                     kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
1064                         (long long)cursor->parent->node_offset,
1065                         cursor->parent_index,
1066                         (long long)cursor->left_bound->obj_id,
1067                         (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
1068                         (long long)cursor->right_bound->obj_id,
1069                         (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
1070                         cursor->left_bound,
1071                         &cursor->parent->ondisk->elms[cursor->parent_index],
1072                         cursor->right_bound,
1073                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
1074                     );
1075         }
1076
1077         /*
1078          * Move our cursor up the tree until we find a node whos range covers
1079          * the key we are trying to locate.
1080          *
1081          * The left bound is inclusive, the right bound is non-inclusive.
1082          * It is ok to cursor up too far.
1083          */
1084         for (;;) {
1085                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
1086                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
1087                 if (r >= 0 && s < 0)
1088                         break;
1089                 KKASSERT(cursor->parent);
1090                 ++hammer_stats_btree_iterations;
1091                 error = hammer_cursor_up(cursor);
1092                 if (error)
1093                         goto done;
1094         }
1095
1096         /*
1097          * The delete-checks below are based on node, not parent.  Set the
1098          * initial delete-check based on the parent.
1099          */
1100         if (r == 1) {
1101                 KKASSERT(cursor->left_bound->create_tid != 1);
1102                 cursor->create_check = cursor->left_bound->create_tid - 1;
1103                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1104         }
1105
1106         /*
1107          * We better have ended up with a node somewhere.
1108          */
1109         KKASSERT(cursor->node != NULL);
1110
1111         /*
1112          * If we are inserting we can't start at a full node if the parent
1113          * is also full (because there is no way to split the node),
1114          * continue running up the tree until the requirement is satisfied
1115          * or we hit the root of the filesystem.
1116          *
1117          * (If inserting we aren't doing an as-of search so we don't have
1118          *  to worry about create_check).
1119          */
1120         while ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1121                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
1122                         if (btree_node_is_full(cursor->node->ondisk) == 0)
1123                                 break;
1124                 } else {
1125                         if (btree_node_is_full(cursor->node->ondisk) ==0)
1126                                 break;
1127                 }
1128                 if (cursor->node->ondisk->parent == 0 ||
1129                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1130                         break;
1131                 }
1132                 ++hammer_stats_btree_iterations;
1133                 error = hammer_cursor_up(cursor);
1134                 /* node may have become stale */
1135                 if (error)
1136                         goto done;
1137         }
1138
1139         /*
1140          * Push down through internal nodes to locate the requested key.
1141          */
1142         node = cursor->node->ondisk;
1143         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1144                 /*
1145                  * Scan the node to find the subtree index to push down into.
1146                  * We go one-past, then back-up.
1147                  *
1148                  * We must proactively remove deleted elements which may
1149                  * have been left over from a deadlocked btree_remove().
1150                  *
1151                  * The left and right boundaries are included in the loop
1152                  * in order to detect edge cases.
1153                  *
1154                  * If the separator only differs by create_tid (r == 1)
1155                  * and we are doing an as-of search, we may end up going
1156                  * down a branch to the left of the one containing the
1157                  * desired key.  This requires numerous special cases.
1158                  */
1159                 ++hammer_stats_btree_iterations;
1160                 if (hammer_debug_btree) {
1161                         kprintf("SEARCH-I %016llx count=%d\n",
1162                                 (long long)cursor->node->node_offset,
1163                                 node->count);
1164                 }
1165
1166                 /*
1167                  * Try to shortcut the search before dropping into the
1168                  * linear loop.  Locate the first node where r <= 1.
1169                  */
1170                 i = hammer_btree_search_node(&cursor->key_beg, node);
1171                 while (i <= node->count) {
1172                         ++hammer_stats_btree_elements;
1173                         elm = &node->elms[i];
1174                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1175                         if (hammer_debug_btree > 2) {
1176                                 kprintf(" IELM %p %d r=%d\n",
1177                                         &node->elms[i], i, r);
1178                         }
1179                         if (r < 0)
1180                                 break;
1181                         if (r == 1) {
1182                                 KKASSERT(elm->base.create_tid != 1);
1183                                 cursor->create_check = elm->base.create_tid - 1;
1184                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1185                         }
1186                         ++i;
1187                 }
1188                 if (hammer_debug_btree) {
1189                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1190                                 i, node->count, r);
1191                 }
1192
1193                 /*
1194                  * These cases occur when the parent's idea of the boundary
1195                  * is wider then the child's idea of the boundary, and
1196                  * require special handling.  If not inserting we can
1197                  * terminate the search early for these cases but the
1198                  * child's boundaries cannot be unconditionally modified.
1199                  */
1200                 if (i == 0) {
1201                         /*
1202                          * If i == 0 the search terminated to the LEFT of the
1203                          * left_boundary but to the RIGHT of the parent's left
1204                          * boundary.
1205                          */
1206                         u_int8_t save;
1207
1208                         elm = &node->elms[0];
1209
1210                         /*
1211                          * If we aren't inserting we can stop here.
1212                          */
1213                         if ((flags & (HAMMER_CURSOR_INSERT |
1214                                       HAMMER_CURSOR_PRUNING)) == 0) {
1215                                 cursor->index = 0;
1216                                 return(ENOENT);
1217                         }
1218
1219                         /*
1220                          * Correct a left-hand boundary mismatch.
1221                          *
1222                          * We can only do this if we can upgrade the lock,
1223                          * and synchronized as a background cursor (i.e.
1224                          * inserting or pruning).
1225                          *
1226                          * WARNING: We can only do this if inserting, i.e.
1227                          * we are running on the backend.
1228                          */
1229                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1230                                 return(error);
1231                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1232                         hammer_modify_node_field(cursor->trans, cursor->node,
1233                                                  elms[0]);
1234                         save = node->elms[0].base.btype;
1235                         node->elms[0].base = *cursor->left_bound;
1236                         node->elms[0].base.btype = save;
1237                         hammer_modify_node_done(cursor->node);
1238                 } else if (i == node->count + 1) {
1239                         /*
1240                          * If i == node->count + 1 the search terminated to
1241                          * the RIGHT of the right boundary but to the LEFT
1242                          * of the parent's right boundary.  If we aren't
1243                          * inserting we can stop here.
1244                          *
1245                          * Note that the last element in this case is
1246                          * elms[i-2] prior to adjustments to 'i'.
1247                          */
1248                         --i;
1249                         if ((flags & (HAMMER_CURSOR_INSERT |
1250                                       HAMMER_CURSOR_PRUNING)) == 0) {
1251                                 cursor->index = i;
1252                                 return (ENOENT);
1253                         }
1254
1255                         /*
1256                          * Correct a right-hand boundary mismatch.
1257                          * (actual push-down record is i-2 prior to
1258                          * adjustments to i).
1259                          *
1260                          * We can only do this if we can upgrade the lock,
1261                          * and synchronized as a background cursor (i.e.
1262                          * inserting or pruning).
1263                          *
1264                          * WARNING: We can only do this if inserting, i.e.
1265                          * we are running on the backend.
1266                          */
1267                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1268                                 return(error);
1269                         elm = &node->elms[i];
1270                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1271                         hammer_modify_node(cursor->trans, cursor->node,
1272                                            &elm->base, sizeof(elm->base));
1273                         elm->base = *cursor->right_bound;
1274                         hammer_modify_node_done(cursor->node);
1275                         --i;
1276                 } else {
1277                         /*
1278                          * The push-down index is now i - 1.  If we had
1279                          * terminated on the right boundary this will point
1280                          * us at the last element.
1281                          */
1282                         --i;
1283                 }
1284                 cursor->index = i;
1285                 elm = &node->elms[i];
1286
1287                 if (hammer_debug_btree) {
1288                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1289                                 "key=%016llx cre=%016llx lo=%02x\n",
1290                                 (long long)cursor->node->node_offset,
1291                                 i,
1292                                 (long long)elm->internal.base.obj_id,
1293                                 elm->internal.base.rec_type,
1294                                 (long long)elm->internal.base.key,
1295                                 (long long)elm->internal.base.create_tid,
1296                                 elm->internal.base.localization
1297                         );
1298                 }
1299
1300                 /*
1301                  * We better have a valid subtree offset.
1302                  */
1303                 KKASSERT(elm->internal.subtree_offset != 0);
1304
1305                 /*
1306                  * Handle insertion and deletion requirements.
1307                  *
1308                  * If inserting split full nodes.  The split code will
1309                  * adjust cursor->node and cursor->index if the current
1310                  * index winds up in the new node.
1311                  *
1312                  * If inserting and a left or right edge case was detected,
1313                  * we cannot correct the left or right boundary and must
1314                  * prepend and append an empty leaf node in order to make
1315                  * the boundary correction.
1316                  *
1317                  * If we run out of space we set enospc and continue on
1318                  * to a leaf to provide the spike code with a good point
1319                  * of entry.
1320                  */
1321                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1322                         if (btree_node_is_full(node)) {
1323                                 error = btree_split_internal(cursor);
1324                                 if (error) {
1325                                         if (error != ENOSPC)
1326                                                 goto done;
1327                                         enospc = 1;
1328                                 }
1329                                 /*
1330                                  * reload stale pointers
1331                                  */
1332                                 i = cursor->index;
1333                                 node = cursor->node->ondisk;
1334                         }
1335                 }
1336
1337                 /*
1338                  * Push down (push into new node, existing node becomes
1339                  * the parent) and continue the search.
1340                  */
1341                 error = hammer_cursor_down(cursor);
1342                 /* node may have become stale */
1343                 if (error)
1344                         goto done;
1345                 node = cursor->node->ondisk;
1346         }
1347
1348         /*
1349          * We are at a leaf, do a linear search of the key array.
1350          *
1351          * On success the index is set to the matching element and 0
1352          * is returned.
1353          *
1354          * On failure the index is set to the insertion point and ENOENT
1355          * is returned.
1356          *
1357          * Boundaries are not stored in leaf nodes, so the index can wind
1358          * up to the left of element 0 (index == 0) or past the end of
1359          * the array (index == node->count).  It is also possible that the
1360          * leaf might be empty.
1361          */
1362         ++hammer_stats_btree_iterations;
1363         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1364         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1365         if (hammer_debug_btree) {
1366                 kprintf("SEARCH-L %016llx count=%d\n",
1367                         (long long)cursor->node->node_offset,
1368                         node->count);
1369         }
1370
1371         /*
1372          * Try to shortcut the search before dropping into the
1373          * linear loop.  Locate the first node where r <= 1.
1374          */
1375         i = hammer_btree_search_node(&cursor->key_beg, node);
1376         while (i < node->count) {
1377                 ++hammer_stats_btree_elements;
1378                 elm = &node->elms[i];
1379
1380                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1381
1382                 if (hammer_debug_btree > 1)
1383                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1384
1385                 /*
1386                  * We are at a record element.  Stop if we've flipped past
1387                  * key_beg, not counting the create_tid test.  Allow the
1388                  * r == 1 case (key_beg > element but differs only by its
1389                  * create_tid) to fall through to the AS-OF check.
1390                  */
1391                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1392
1393                 if (r < 0)
1394                         goto failed;
1395                 if (r > 1) {
1396                         ++i;
1397                         continue;
1398                 }
1399
1400                 /*
1401                  * Check our as-of timestamp against the element.
1402                  */
1403                 if (flags & HAMMER_CURSOR_ASOF) {
1404                         if (hammer_btree_chkts(cursor->asof,
1405                                                &node->elms[i].base) != 0) {
1406                                 ++i;
1407                                 continue;
1408                         }
1409                         /* success */
1410                 } else {
1411                         if (r > 0) {    /* can only be +1 */
1412                                 ++i;
1413                                 continue;
1414                         }
1415                         /* success */
1416                 }
1417                 cursor->index = i;
1418                 error = 0;
1419                 if (hammer_debug_btree) {
1420                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1421                                 (long long)cursor->node->node_offset, i);
1422                 }
1423                 goto done;
1424         }
1425
1426         /*
1427          * The search of the leaf node failed.  i is the insertion point.
1428          */
1429 failed:
1430         if (hammer_debug_btree) {
1431                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1432                         (long long)cursor->node->node_offset, i);
1433         }
1434
1435         /*
1436          * No exact match was found, i is now at the insertion point.
1437          *
1438          * If inserting split a full leaf before returning.  This
1439          * may have the side effect of adjusting cursor->node and
1440          * cursor->index.
1441          */
1442         cursor->index = i;
1443         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1444              btree_node_is_full(node)) {
1445                 error = btree_split_leaf(cursor);
1446                 if (error) {
1447                         if (error != ENOSPC)
1448                                 goto done;
1449                         enospc = 1;
1450                 }
1451                 /*
1452                  * reload stale pointers
1453                  */
1454                 /* NOT USED
1455                 i = cursor->index;
1456                 node = &cursor->node->internal;
1457                 */
1458         }
1459
1460         /*
1461          * We reached a leaf but did not find the key we were looking for.
1462          * If this is an insert we will be properly positioned for an insert
1463          * (ENOENT) or spike (ENOSPC) operation.
1464          */
1465         error = enospc ? ENOSPC : ENOENT;
1466 done:
1467         return(error);
1468 }
1469
1470 /*
1471  * Heuristical search for the first element whos comparison is <= 1.  May
1472  * return an index whos compare result is > 1 but may only return an index
1473  * whos compare result is <= 1 if it is the first element with that result.
1474  */
1475 int
1476 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1477 {
1478         int b;
1479         int s;
1480         int i;
1481         int r;
1482
1483         /*
1484          * Don't bother if the node does not have very many elements
1485          */
1486         b = 0;
1487         s = node->count;
1488         while (s - b > 4) {
1489                 i = b + (s - b) / 2;
1490                 ++hammer_stats_btree_elements;
1491                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1492                 if (r <= 1) {
1493                         s = i;
1494                 } else {
1495                         b = i;
1496                 }
1497         }
1498         return(b);
1499 }
1500
1501
1502 /************************************************************************
1503  *                         SPLITTING AND MERGING                        *
1504  ************************************************************************
1505  *
1506  * These routines do all the dirty work required to split and merge nodes.
1507  */
1508
1509 /*
1510  * Split an internal node into two nodes and move the separator at the split
1511  * point to the parent.
1512  *
1513  * (cursor->node, cursor->index) indicates the element the caller intends
1514  * to push into.  We will adjust node and index if that element winds
1515  * up in the split node.
1516  *
1517  * If we are at the root of the filesystem a new root must be created with
1518  * two elements, one pointing to the original root and one pointing to the
1519  * newly allocated split node.
1520  */
1521 static
1522 int
1523 btree_split_internal(hammer_cursor_t cursor)
1524 {
1525         hammer_node_ondisk_t ondisk;
1526         hammer_node_t node;
1527         hammer_node_t parent;
1528         hammer_node_t new_node;
1529         hammer_btree_elm_t elm;
1530         hammer_btree_elm_t parent_elm;
1531         struct hammer_node_lock lockroot;
1532         hammer_mount_t hmp = cursor->trans->hmp;
1533         int parent_index;
1534         int made_root;
1535         int split;
1536         int error;
1537         int i;
1538         const int esize = sizeof(*elm);
1539
1540         hammer_node_lock_init(&lockroot, cursor->node);
1541         error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
1542         if (error)
1543                 goto done;
1544         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1545                 goto done;
1546         ++hammer_stats_btree_splits;
1547
1548         /*
1549          * Calculate the split point.  If the insertion point is at the
1550          * end of the leaf we adjust the split point significantly to the
1551          * right to try to optimize node fill and flag it.  If we hit
1552          * that same leaf again our heuristic failed and we don't try
1553          * to optimize node fill (it could lead to a degenerate case).
1554          */
1555         node = cursor->node;
1556         ondisk = node->ondisk;
1557         KKASSERT(ondisk->count > 4);
1558         if (cursor->index == ondisk->count &&
1559             (node->flags & HAMMER_NODE_NONLINEAR) == 0) {
1560                 split = (ondisk->count + 1) * 3 / 4;
1561                 node->flags |= HAMMER_NODE_NONLINEAR;
1562         } else {
1563                 /*
1564                  * We are splitting but elms[split] will be promoted to
1565                  * the parent, leaving the right hand node with one less
1566                  * element.  If the insertion point will be on the
1567                  * left-hand side adjust the split point to give the
1568                  * right hand side one additional node.
1569                  */
1570                 split = (ondisk->count + 1) / 2;
1571                 if (cursor->index <= split)
1572                         --split;
1573         }
1574
1575         /*
1576          * If we are at the root of the filesystem, create a new root node
1577          * with 1 element and split normally.  Avoid making major
1578          * modifications until we know the whole operation will work.
1579          */
1580         if (ondisk->parent == 0) {
1581                 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1582                 if (parent == NULL)
1583                         goto done;
1584                 hammer_lock_ex(&parent->lock);
1585                 hammer_modify_node_noundo(cursor->trans, parent);
1586                 ondisk = parent->ondisk;
1587                 ondisk->count = 1;
1588                 ondisk->parent = 0;
1589                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1590                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1591                 ondisk->elms[0].base = hmp->root_btree_beg;
1592                 ondisk->elms[0].base.btype = node->ondisk->type;
1593                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1594                 ondisk->elms[1].base = hmp->root_btree_end;
1595                 hammer_modify_node_done(parent);
1596                 /* ondisk->elms[1].base.btype - not used */
1597                 made_root = 1;
1598                 parent_index = 0;       /* index of current node in parent */
1599         } else {
1600                 made_root = 0;
1601                 parent = cursor->parent;
1602                 parent_index = cursor->parent_index;
1603         }
1604
1605         /*
1606          * Split node into new_node at the split point.
1607          *
1608          *  B O O O P N N B     <-- P = node->elms[split] (index 4)
1609          *   0 1 2 3 4 5 6      <-- subtree indices
1610          *
1611          *       x x P x x
1612          *        s S S s
1613          *         /   \
1614          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1615          *   0 1 2 3      4 5 6
1616          */
1617         new_node = hammer_alloc_btree(cursor->trans, 0, &error);
1618         if (new_node == NULL) {
1619                 if (made_root) {
1620                         hammer_unlock(&parent->lock);
1621                         hammer_delete_node(cursor->trans, parent);
1622                         hammer_rel_node(parent);
1623                 }
1624                 goto done;
1625         }
1626         hammer_lock_ex(&new_node->lock);
1627
1628         /*
1629          * Create the new node.  P becomes the left-hand boundary in the
1630          * new node.  Copy the right-hand boundary as well.
1631          *
1632          * elm is the new separator.
1633          */
1634         hammer_modify_node_noundo(cursor->trans, new_node);
1635         hammer_modify_node_all(cursor->trans, node);
1636         ondisk = node->ondisk;
1637         elm = &ondisk->elms[split];
1638         bcopy(elm, &new_node->ondisk->elms[0],
1639               (ondisk->count - split + 1) * esize);
1640         new_node->ondisk->count = ondisk->count - split;
1641         new_node->ondisk->parent = parent->node_offset;
1642         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1643         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1644         KKASSERT(ondisk->type == new_node->ondisk->type);
1645         hammer_cursor_split_node(node, new_node, split);
1646
1647         /*
1648          * Cleanup the original node.  Elm (P) becomes the new boundary,
1649          * its subtree_offset was moved to the new node.  If we had created
1650          * a new root its parent pointer may have changed.
1651          */
1652         elm->internal.subtree_offset = 0;
1653         ondisk->count = split;
1654
1655         /*
1656          * Insert the separator into the parent, fixup the parent's
1657          * reference to the original node, and reference the new node.
1658          * The separator is P.
1659          *
1660          * Remember that base.count does not include the right-hand boundary.
1661          */
1662         hammer_modify_node_all(cursor->trans, parent);
1663         ondisk = parent->ondisk;
1664         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1665         parent_elm = &ondisk->elms[parent_index+1];
1666         bcopy(parent_elm, parent_elm + 1,
1667               (ondisk->count - parent_index) * esize);
1668         parent_elm->internal.base = elm->base;  /* separator P */
1669         parent_elm->internal.base.btype = new_node->ondisk->type;
1670         parent_elm->internal.subtree_offset = new_node->node_offset;
1671         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1672         ++ondisk->count;
1673         hammer_modify_node_done(parent);
1674         hammer_cursor_inserted_element(parent, parent_index + 1);
1675
1676         /*
1677          * The children of new_node need their parent pointer set to new_node.
1678          * The children have already been locked by
1679          * hammer_btree_lock_children().
1680          */
1681         for (i = 0; i < new_node->ondisk->count; ++i) {
1682                 elm = &new_node->ondisk->elms[i];
1683                 error = btree_set_parent(cursor->trans, new_node, elm);
1684                 if (error) {
1685                         panic("btree_split_internal: btree-fixup problem");
1686                 }
1687         }
1688         hammer_modify_node_done(new_node);
1689
1690         /*
1691          * The filesystem's root B-Tree pointer may have to be updated.
1692          */
1693         if (made_root) {
1694                 hammer_volume_t volume;
1695
1696                 volume = hammer_get_root_volume(hmp, &error);
1697                 KKASSERT(error == 0);
1698
1699                 hammer_modify_volume_field(cursor->trans, volume,
1700                                            vol0_btree_root);
1701                 volume->ondisk->vol0_btree_root = parent->node_offset;
1702                 hammer_modify_volume_done(volume);
1703                 node->ondisk->parent = parent->node_offset;
1704                 if (cursor->parent) {
1705                         hammer_unlock(&cursor->parent->lock);
1706                         hammer_rel_node(cursor->parent);
1707                 }
1708                 cursor->parent = parent;        /* lock'd and ref'd */
1709                 hammer_rel_volume(volume, 0);
1710         }
1711         hammer_modify_node_done(node);
1712
1713         /*
1714          * Ok, now adjust the cursor depending on which element the original
1715          * index was pointing at.  If we are >= the split point the push node
1716          * is now in the new node.
1717          *
1718          * NOTE: If we are at the split point itself we cannot stay with the
1719          * original node because the push index will point at the right-hand
1720          * boundary, which is illegal.
1721          *
1722          * NOTE: The cursor's parent or parent_index must be adjusted for
1723          * the case where a new parent (new root) was created, and the case
1724          * where the cursor is now pointing at the split node.
1725          */
1726         if (cursor->index >= split) {
1727                 cursor->parent_index = parent_index + 1;
1728                 cursor->index -= split;
1729                 hammer_unlock(&cursor->node->lock);
1730                 hammer_rel_node(cursor->node);
1731                 cursor->node = new_node;        /* locked and ref'd */
1732         } else {
1733                 cursor->parent_index = parent_index;
1734                 hammer_unlock(&new_node->lock);
1735                 hammer_rel_node(new_node);
1736         }
1737
1738         /*
1739          * Fixup left and right bounds
1740          */
1741         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1742         cursor->left_bound = &parent_elm[0].internal.base;
1743         cursor->right_bound = &parent_elm[1].internal.base;
1744         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1745                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1746         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1747                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1748
1749 done:
1750         hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
1751         hammer_cursor_downgrade(cursor);
1752         return (error);
1753 }
1754
1755 /*
1756  * Same as the above, but splits a full leaf node.
1757  *
1758  * This function
1759  */
1760 static
1761 int
1762 btree_split_leaf(hammer_cursor_t cursor)
1763 {
1764         hammer_node_ondisk_t ondisk;
1765         hammer_node_t parent;
1766         hammer_node_t leaf;
1767         hammer_mount_t hmp;
1768         hammer_node_t new_leaf;
1769         hammer_btree_elm_t elm;
1770         hammer_btree_elm_t parent_elm;
1771         hammer_base_elm_t mid_boundary;
1772         int parent_index;
1773         int made_root;
1774         int split;
1775         int error;
1776         const size_t esize = sizeof(*elm);
1777
1778         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1779                 return(error);
1780         ++hammer_stats_btree_splits;
1781
1782         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1783                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1784         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1785                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1786
1787         /*
1788          * Calculate the split point.  If the insertion point is at the
1789          * end of the leaf we adjust the split point significantly to the
1790          * right to try to optimize node fill and flag it.  If we hit
1791          * that same leaf again our heuristic failed and we don't try
1792          * to optimize node fill (it could lead to a degenerate case).
1793          *
1794          * Spikes are made up of two leaf elements which cannot be
1795          * safely split.
1796          */
1797         leaf = cursor->node;
1798         ondisk = leaf->ondisk;
1799         KKASSERT(ondisk->count > 4);
1800         if (cursor->index == ondisk->count &&
1801             (leaf->flags & HAMMER_NODE_NONLINEAR) == 0) {
1802                 split = (ondisk->count + 1) * 3 / 4;
1803                 leaf->flags |= HAMMER_NODE_NONLINEAR;
1804         } else {
1805                 split = (ondisk->count + 1) / 2;
1806         }
1807
1808 #if 0
1809         /*
1810          * If the insertion point is at the split point shift the
1811          * split point left so we don't have to worry about
1812          */
1813         if (cursor->index == split)
1814                 --split;
1815 #endif
1816         KKASSERT(split > 0 && split < ondisk->count);
1817
1818         error = 0;
1819         hmp = leaf->hmp;
1820
1821         elm = &ondisk->elms[split];
1822
1823         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1824         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1825         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1826         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1827
1828         /*
1829          * If we are at the root of the tree, create a new root node with
1830          * 1 element and split normally.  Avoid making major modifications
1831          * until we know the whole operation will work.
1832          */
1833         if (ondisk->parent == 0) {
1834                 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1835                 if (parent == NULL)
1836                         goto done;
1837                 hammer_lock_ex(&parent->lock);
1838                 hammer_modify_node_noundo(cursor->trans, parent);
1839                 ondisk = parent->ondisk;
1840                 ondisk->count = 1;
1841                 ondisk->parent = 0;
1842                 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1843                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1844                 ondisk->elms[0].base = hmp->root_btree_beg;
1845                 ondisk->elms[0].base.btype = leaf->ondisk->type;
1846                 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1847                 ondisk->elms[1].base = hmp->root_btree_end;
1848                 /* ondisk->elms[1].base.btype = not used */
1849                 hammer_modify_node_done(parent);
1850                 made_root = 1;
1851                 parent_index = 0;       /* insertion point in parent */
1852         } else {
1853                 made_root = 0;
1854                 parent = cursor->parent;
1855                 parent_index = cursor->parent_index;
1856         }
1857
1858         /*
1859          * Split leaf into new_leaf at the split point.  Select a separator
1860          * value in-between the two leafs but with a bent towards the right
1861          * leaf since comparisons use an 'elm >= separator' inequality.
1862          *
1863          *  L L L L L L L L
1864          *
1865          *       x x P x x
1866          *        s S S s
1867          *         /   \
1868          *  L L L L     L L L L
1869          */
1870         new_leaf = hammer_alloc_btree(cursor->trans, 0, &error);
1871         if (new_leaf == NULL) {
1872                 if (made_root) {
1873                         hammer_unlock(&parent->lock);
1874                         hammer_delete_node(cursor->trans, parent);
1875                         hammer_rel_node(parent);
1876                 }
1877                 goto done;
1878         }
1879         hammer_lock_ex(&new_leaf->lock);
1880
1881         /*
1882          * Create the new node and copy the leaf elements from the split
1883          * point on to the new node.
1884          */
1885         hammer_modify_node_all(cursor->trans, leaf);
1886         hammer_modify_node_noundo(cursor->trans, new_leaf);
1887         ondisk = leaf->ondisk;
1888         elm = &ondisk->elms[split];
1889         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1890         new_leaf->ondisk->count = ondisk->count - split;
1891         new_leaf->ondisk->parent = parent->node_offset;
1892         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1893         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1894         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1895         hammer_modify_node_done(new_leaf);
1896         hammer_cursor_split_node(leaf, new_leaf, split);
1897
1898         /*
1899          * Cleanup the original node.  Because this is a leaf node and
1900          * leaf nodes do not have a right-hand boundary, there
1901          * aren't any special edge cases to clean up.  We just fixup the
1902          * count.
1903          */
1904         ondisk->count = split;
1905
1906         /*
1907          * Insert the separator into the parent, fixup the parent's
1908          * reference to the original node, and reference the new node.
1909          * The separator is P.
1910          *
1911          * Remember that base.count does not include the right-hand boundary.
1912          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1913          */
1914         hammer_modify_node_all(cursor->trans, parent);
1915         ondisk = parent->ondisk;
1916         KKASSERT(split != 0);
1917         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1918         parent_elm = &ondisk->elms[parent_index+1];
1919         bcopy(parent_elm, parent_elm + 1,
1920               (ondisk->count - parent_index) * esize);
1921
1922         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1923         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1924         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1925         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1926         mid_boundary = &parent_elm->base;
1927         ++ondisk->count;
1928         hammer_modify_node_done(parent);
1929         hammer_cursor_inserted_element(parent, parent_index + 1);
1930
1931         /*
1932          * The filesystem's root B-Tree pointer may have to be updated.
1933          */
1934         if (made_root) {
1935                 hammer_volume_t volume;
1936
1937                 volume = hammer_get_root_volume(hmp, &error);
1938                 KKASSERT(error == 0);
1939
1940                 hammer_modify_volume_field(cursor->trans, volume,
1941                                            vol0_btree_root);
1942                 volume->ondisk->vol0_btree_root = parent->node_offset;
1943                 hammer_modify_volume_done(volume);
1944                 leaf->ondisk->parent = parent->node_offset;
1945                 if (cursor->parent) {
1946                         hammer_unlock(&cursor->parent->lock);
1947                         hammer_rel_node(cursor->parent);
1948                 }
1949                 cursor->parent = parent;        /* lock'd and ref'd */
1950                 hammer_rel_volume(volume, 0);
1951         }
1952         hammer_modify_node_done(leaf);
1953
1954         /*
1955          * Ok, now adjust the cursor depending on which element the original
1956          * index was pointing at.  If we are >= the split point the push node
1957          * is now in the new node.
1958          *
1959          * NOTE: If we are at the split point itself we need to select the
1960          * old or new node based on where key_beg's insertion point will be.
1961          * If we pick the wrong side the inserted element will wind up in
1962          * the wrong leaf node and outside that node's bounds.
1963          */
1964         if (cursor->index > split ||
1965             (cursor->index == split &&
1966              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1967                 cursor->parent_index = parent_index + 1;
1968                 cursor->index -= split;
1969                 hammer_unlock(&cursor->node->lock);
1970                 hammer_rel_node(cursor->node);
1971                 cursor->node = new_leaf;
1972         } else {
1973                 cursor->parent_index = parent_index;
1974                 hammer_unlock(&new_leaf->lock);
1975                 hammer_rel_node(new_leaf);
1976         }
1977
1978         /*
1979          * Fixup left and right bounds
1980          */
1981         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1982         cursor->left_bound = &parent_elm[0].internal.base;
1983         cursor->right_bound = &parent_elm[1].internal.base;
1984
1985         /*
1986          * Assert that the bounds are correct.
1987          */
1988         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1989                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1990         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1991                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1992         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
1993         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
1994
1995 done:
1996         hammer_cursor_downgrade(cursor);
1997         return (error);
1998 }
1999
2000 #if 0
2001
2002 /*
2003  * Recursively correct the right-hand boundary's create_tid to (tid) as
2004  * long as the rest of the key matches.  We have to recurse upward in
2005  * the tree as well as down the left side of each parent's right node.
2006  *
2007  * Return EDEADLK if we were only partially successful, forcing the caller
2008  * to try again.  The original cursor is not modified.  This routine can
2009  * also fail with EDEADLK if it is forced to throw away a portion of its
2010  * record history.
2011  *
2012  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
2013  */
2014 struct hammer_rhb {
2015         TAILQ_ENTRY(hammer_rhb) entry;
2016         hammer_node_t   node;
2017         int             index;
2018 };
2019
2020 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
2021
2022 int
2023 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
2024 {
2025         struct hammer_mount *hmp;
2026         struct hammer_rhb_list rhb_list;
2027         hammer_base_elm_t elm;
2028         hammer_node_t orig_node;
2029         struct hammer_rhb *rhb;
2030         int orig_index;
2031         int error;
2032
2033         TAILQ_INIT(&rhb_list);
2034         hmp = cursor->trans->hmp;
2035
2036         /*
2037          * Save our position so we can restore it on return.  This also
2038          * gives us a stable 'elm'.
2039          */
2040         orig_node = cursor->node;
2041         hammer_ref_node(orig_node);
2042         hammer_lock_sh(&orig_node->lock);
2043         orig_index = cursor->index;
2044         elm = &orig_node->ondisk->elms[orig_index].base;
2045
2046         /*
2047          * Now build a list of parents going up, allocating a rhb
2048          * structure for each one.
2049          */
2050         while (cursor->parent) {
2051                 /*
2052                  * Stop if we no longer have any right-bounds to fix up
2053                  */
2054                 if (elm->obj_id != cursor->right_bound->obj_id ||
2055                     elm->rec_type != cursor->right_bound->rec_type ||
2056                     elm->key != cursor->right_bound->key) {
2057                         break;
2058                 }
2059
2060                 /*
2061                  * Stop if the right-hand bound's create_tid does not
2062                  * need to be corrected.
2063                  */
2064                 if (cursor->right_bound->create_tid >= tid)
2065                         break;
2066
2067                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2068                 rhb->node = cursor->parent;
2069                 rhb->index = cursor->parent_index;
2070                 hammer_ref_node(rhb->node);
2071                 hammer_lock_sh(&rhb->node->lock);
2072                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2073
2074                 hammer_cursor_up(cursor);
2075         }
2076
2077         /*
2078          * now safely adjust the right hand bound for each rhb.  This may
2079          * also require taking the right side of the tree and iterating down
2080          * ITS left side.
2081          */
2082         error = 0;
2083         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2084                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2085                 if (error)
2086                         break;
2087                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2088                 hammer_unlock(&rhb->node->lock);
2089                 hammer_rel_node(rhb->node);
2090                 kfree(rhb, hmp->m_misc);
2091
2092                 switch (cursor->node->ondisk->type) {
2093                 case HAMMER_BTREE_TYPE_INTERNAL:
2094                         /*
2095                          * Right-boundary for parent at internal node
2096                          * is one element to the right of the element whos
2097                          * right boundary needs adjusting.  We must then
2098                          * traverse down the left side correcting any left
2099                          * bounds (which may now be too far to the left).
2100                          */
2101                         ++cursor->index;
2102                         error = hammer_btree_correct_lhb(cursor, tid);
2103                         break;
2104                 default:
2105                         panic("hammer_btree_correct_rhb(): Bad node type");
2106                         error = EINVAL;
2107                         break;
2108                 }
2109         }
2110
2111         /*
2112          * Cleanup
2113          */
2114         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2115                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2116                 hammer_unlock(&rhb->node->lock);
2117                 hammer_rel_node(rhb->node);
2118                 kfree(rhb, hmp->m_misc);
2119         }
2120         error = hammer_cursor_seek(cursor, orig_node, orig_index);
2121         hammer_unlock(&orig_node->lock);
2122         hammer_rel_node(orig_node);
2123         return (error);
2124 }
2125
2126 /*
2127  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2128  * bound going downward starting at the current cursor position.
2129  *
2130  * This function does not restore the cursor after use.
2131  */
2132 int
2133 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2134 {
2135         struct hammer_rhb_list rhb_list;
2136         hammer_base_elm_t elm;
2137         hammer_base_elm_t cmp;
2138         struct hammer_rhb *rhb;
2139         struct hammer_mount *hmp;
2140         int error;
2141
2142         TAILQ_INIT(&rhb_list);
2143         hmp = cursor->trans->hmp;
2144
2145         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2146
2147         /*
2148          * Record the node and traverse down the left-hand side for all
2149          * matching records needing a boundary correction.
2150          */
2151         error = 0;
2152         for (;;) {
2153                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2154                 rhb->node = cursor->node;
2155                 rhb->index = cursor->index;
2156                 hammer_ref_node(rhb->node);
2157                 hammer_lock_sh(&rhb->node->lock);
2158                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2159
2160                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2161                         /*
2162                          * Nothing to traverse down if we are at the right
2163                          * boundary of an internal node.
2164                          */
2165                         if (cursor->index == cursor->node->ondisk->count)
2166                                 break;
2167                 } else {
2168                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2169                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2170                                 break;
2171                         panic("Illegal leaf record type %02x", elm->btype);
2172                 }
2173                 error = hammer_cursor_down(cursor);
2174                 if (error)
2175                         break;
2176
2177                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2178                 if (elm->obj_id != cmp->obj_id ||
2179                     elm->rec_type != cmp->rec_type ||
2180                     elm->key != cmp->key) {
2181                         break;
2182                 }
2183                 if (elm->create_tid >= tid)
2184                         break;
2185
2186         }
2187
2188         /*
2189          * Now we can safely adjust the left-hand boundary from the bottom-up.
2190          * The last element we remove from the list is the caller's right hand
2191          * boundary, which must also be adjusted.
2192          */
2193         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2194                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2195                 if (error)
2196                         break;
2197                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2198                 hammer_unlock(&rhb->node->lock);
2199                 hammer_rel_node(rhb->node);
2200                 kfree(rhb, hmp->m_misc);
2201
2202                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2203                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2204                         hammer_modify_node(cursor->trans, cursor->node,
2205                                            &elm->create_tid,
2206                                            sizeof(elm->create_tid));
2207                         elm->create_tid = tid;
2208                         hammer_modify_node_done(cursor->node);
2209                 } else {
2210                         panic("hammer_btree_correct_lhb(): Bad element type");
2211                 }
2212         }
2213
2214         /*
2215          * Cleanup
2216          */
2217         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2218                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2219                 hammer_unlock(&rhb->node->lock);
2220                 hammer_rel_node(rhb->node);
2221                 kfree(rhb, hmp->m_misc);
2222         }
2223         return (error);
2224 }
2225
2226 #endif
2227
2228 /*
2229  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2230  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2231  * the operation due to a deadlock, or some other error.
2232  *
2233  * This routine is initially called with an empty leaf and may be
2234  * recursively called with single-element internal nodes.
2235  *
2236  * It should also be noted that when removing empty leaves we must be sure
2237  * to test and update mirror_tid because another thread may have deadlocked
2238  * against us (or someone) trying to propagate it up and cannot retry once
2239  * the node has been deleted.
2240  *
2241  * On return the cursor may end up pointing to an internal node, suitable
2242  * for further iteration but not for an immediate insertion or deletion.
2243  */
2244 static int
2245 btree_remove(hammer_cursor_t cursor)
2246 {
2247         hammer_node_ondisk_t ondisk;
2248         hammer_btree_elm_t elm;
2249         hammer_node_t node;
2250         hammer_node_t parent;
2251         const int esize = sizeof(*elm);
2252         int error;
2253
2254         node = cursor->node;
2255
2256         /*
2257          * When deleting the root of the filesystem convert it to
2258          * an empty leaf node.  Internal nodes cannot be empty.
2259          */
2260         ondisk = node->ondisk;
2261         if (ondisk->parent == 0) {
2262                 KKASSERT(cursor->parent == NULL);
2263                 hammer_modify_node_all(cursor->trans, node);
2264                 KKASSERT(ondisk == node->ondisk);
2265                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2266                 ondisk->count = 0;
2267                 hammer_modify_node_done(node);
2268                 cursor->index = 0;
2269                 return(0);
2270         }
2271
2272         parent = cursor->parent;
2273
2274         /*
2275          * Attempt to remove the parent's reference to the child.  If the
2276          * parent would become empty we have to recurse.  If we fail we
2277          * leave the parent pointing to an empty leaf node.
2278          *
2279          * We have to recurse successfully before we can delete the internal
2280          * node as it is illegal to have empty internal nodes.  Even though
2281          * the operation may be aborted we must still fixup any unlocked
2282          * cursors as if we had deleted the element prior to recursing
2283          * (by calling hammer_cursor_deleted_element()) so those cursors
2284          * are properly forced up the chain by the recursion.
2285          */
2286         if (parent->ondisk->count == 1) {
2287                 /*
2288                  * This special cursor_up_locked() call leaves the original
2289                  * node exclusively locked and referenced, leaves the
2290                  * original parent locked (as the new node), and locks the
2291                  * new parent.  It can return EDEADLK.
2292                  *
2293                  * We cannot call hammer_cursor_removed_node() until we are
2294                  * actually able to remove the node.  If we did then tracked
2295                  * cursors in the middle of iterations could be repointed
2296                  * to a parent node.  If this occurs they could end up
2297                  * scanning newly inserted records into the node (that could
2298                  * not be deleted) when they push down again.
2299                  *
2300                  * Due to the way the recursion works the final parent is left
2301                  * in cursor->parent after the recursion returns.  Each
2302                  * layer on the way back up is thus able to call
2303                  * hammer_cursor_removed_node() and 'jump' the node up to
2304                  * the (same) final parent.
2305                  *
2306                  * NOTE!  The local variable 'parent' is invalid after we
2307                  *        call hammer_cursor_up_locked().
2308                  */
2309                 error = hammer_cursor_up_locked(cursor);
2310                 parent = NULL;
2311
2312                 if (error == 0) {
2313                         hammer_cursor_deleted_element(cursor->node, 0);
2314                         error = btree_remove(cursor);
2315                         if (error == 0) {
2316                                 KKASSERT(node != cursor->node);
2317                                 hammer_cursor_removed_node(
2318                                         node, cursor->node,
2319                                         cursor->index);
2320                                 hammer_modify_node_all(cursor->trans, node);
2321                                 ondisk = node->ondisk;
2322                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2323                                 ondisk->count = 0;
2324                                 hammer_modify_node_done(node);
2325                                 hammer_flush_node(node, 0);
2326                                 hammer_delete_node(cursor->trans, node);
2327                         } else {
2328                                 /*
2329                                  * Defer parent removal because we could not
2330                                  * get the lock, just let the leaf remain
2331                                  * empty.
2332                                  */
2333                                 /**/
2334                         }
2335                         hammer_unlock(&node->lock);
2336                         hammer_rel_node(node);
2337                 } else {
2338                         /*
2339                          * Defer parent removal because we could not
2340                          * get the lock, just let the leaf remain
2341                          * empty.
2342                          */
2343                         /**/
2344                 }
2345         } else {
2346                 KKASSERT(parent->ondisk->count > 1);
2347
2348                 hammer_modify_node_all(cursor->trans, parent);
2349                 ondisk = parent->ondisk;
2350                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2351
2352                 elm = &ondisk->elms[cursor->parent_index];
2353                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2354                 KKASSERT(ondisk->count > 0);
2355
2356                 /*
2357                  * We must retain the highest mirror_tid.  The deleted
2358                  * range is now encompassed by the element to the left.
2359                  * If we are already at the left edge the new left edge
2360                  * inherits mirror_tid.
2361                  *
2362                  * Note that bounds of the parent to our parent may create
2363                  * a gap to the left of our left-most node or to the right
2364                  * of our right-most node.  The gap is silently included
2365                  * in the mirror_tid's area of effect from the point of view
2366                  * of the scan.
2367                  */
2368                 if (cursor->parent_index) {
2369                         if (elm[-1].internal.mirror_tid <
2370                             elm[0].internal.mirror_tid) {
2371                                 elm[-1].internal.mirror_tid =
2372                                     elm[0].internal.mirror_tid;
2373                         }
2374                 } else {
2375                         if (elm[1].internal.mirror_tid <
2376                             elm[0].internal.mirror_tid) {
2377                                 elm[1].internal.mirror_tid =
2378                                     elm[0].internal.mirror_tid;
2379                         }
2380                 }
2381
2382                 /*
2383                  * Delete the subtree reference in the parent.  Include
2384                  * boundary element at end.
2385                  */
2386                 bcopy(&elm[1], &elm[0],
2387                       (ondisk->count - cursor->parent_index) * esize);
2388                 --ondisk->count;
2389                 hammer_modify_node_done(parent);
2390                 hammer_cursor_removed_node(node, parent, cursor->parent_index);
2391                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2392                 hammer_flush_node(node, 0);
2393                 hammer_delete_node(cursor->trans, node);
2394
2395                 /*
2396                  * cursor->node is invalid, cursor up to make the cursor
2397                  * valid again.  We have to flag the condition in case
2398                  * another thread wiggles an insertion in during an
2399                  * iteration.
2400                  */
2401                 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
2402                 error = hammer_cursor_up(cursor);
2403         }
2404         return (error);
2405 }
2406
2407 /*
2408  * Propagate cursor->trans->tid up the B-Tree starting at the current
2409  * cursor position using pseudofs info gleaned from the passed inode.
2410  *
2411  * The passed inode has no relationship to the cursor position other
2412  * then being in the same pseudofs as the insertion or deletion we
2413  * are propagating the mirror_tid for.
2414  *
2415  * WARNING!  Because we push and pop the passed cursor, it may be
2416  *           modified by other B-Tree operations while it is unlocked
2417  *           and things like the node & leaf pointers, and indexes might
2418  *           change.
2419  */
2420 void
2421 hammer_btree_do_propagation(hammer_cursor_t cursor,
2422                             hammer_pseudofs_inmem_t pfsm,
2423                             hammer_btree_leaf_elm_t leaf)
2424 {
2425         hammer_cursor_t ncursor;
2426         hammer_tid_t mirror_tid;
2427         int error __debugvar;
2428
2429         /*
2430          * We do not propagate a mirror_tid if the filesystem was mounted
2431          * in no-mirror mode.
2432          */
2433         if (cursor->trans->hmp->master_id < 0)
2434                 return;
2435
2436         /*
2437          * This is a bit of a hack because we cannot deadlock or return
2438          * EDEADLK here.  The related operation has already completed and
2439          * we must propagate the mirror_tid now regardless.
2440          *
2441          * Generate a new cursor which inherits the original's locks and
2442          * unlock the original.  Use the new cursor to propagate the
2443          * mirror_tid.  Then clean up the new cursor and reacquire locks
2444          * on the original.
2445          *
2446          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2447          * original's locks and the original is tracked and must be
2448          * re-locked.
2449          */
2450         mirror_tid = cursor->node->ondisk->mirror_tid;
2451         KKASSERT(mirror_tid != 0);
2452         ncursor = hammer_push_cursor(cursor);
2453         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2454         KKASSERT(error == 0);
2455         hammer_pop_cursor(cursor, ncursor);
2456         /* WARNING: cursor's leaf pointer may change after pop */
2457 }
2458
2459
2460 /*
2461  * Propagate a mirror TID update upwards through the B-Tree to the root.
2462  *
2463  * A locked internal node must be passed in.  The node will remain locked
2464  * on return.
2465  *
2466  * This function syncs mirror_tid at the specified internal node's element,
2467  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2468  */
2469 static int
2470 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2471 {
2472         hammer_btree_internal_elm_t elm;
2473         hammer_node_t node;
2474         int error;
2475
2476         for (;;) {
2477                 error = hammer_cursor_up(cursor);
2478                 if (error == 0)
2479                         error = hammer_cursor_upgrade(cursor);
2480
2481                 /*
2482                  * We can ignore HAMMER_CURSOR_ITERATE_CHECK, the
2483                  * cursor will still be properly positioned for
2484                  * mirror propagation, just not for iterations.
2485                  */
2486                 while (error == EDEADLK) {
2487                         hammer_recover_cursor(cursor);
2488                         error = hammer_cursor_upgrade(cursor);
2489                 }
2490                 if (error)
2491                         break;
2492
2493                 /*
2494                  * If the cursor deadlocked it could end up at a leaf
2495                  * after we lost the lock.
2496                  */
2497                 node = cursor->node;
2498                 if (node->ondisk->type != HAMMER_BTREE_TYPE_INTERNAL)
2499                         continue;
2500
2501                 /*
2502                  * Adjust the node's element
2503                  */
2504                 elm = &node->ondisk->elms[cursor->index].internal;
2505                 if (elm->mirror_tid >= mirror_tid)
2506                         break;
2507                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2508                                    sizeof(elm->mirror_tid));
2509                 elm->mirror_tid = mirror_tid;
2510                 hammer_modify_node_done(node);
2511                 if (hammer_debug_general & 0x0002) {
2512                         kprintf("mirror_propagate: propagate "
2513                                 "%016llx @%016llx:%d\n",
2514                                 (long long)mirror_tid,
2515                                 (long long)node->node_offset,
2516                                 cursor->index);
2517                 }
2518
2519
2520                 /*
2521                  * Adjust the node's mirror_tid aggregator
2522                  */
2523                 if (node->ondisk->mirror_tid >= mirror_tid)
2524                         return(0);
2525                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2526                 node->ondisk->mirror_tid = mirror_tid;
2527                 hammer_modify_node_done(node);
2528                 if (hammer_debug_general & 0x0002) {
2529                         kprintf("mirror_propagate: propagate "
2530                                 "%016llx @%016llx\n",
2531                                 (long long)mirror_tid,
2532                                 (long long)node->node_offset);
2533                 }
2534         }
2535         if (error == ENOENT)
2536                 error = 0;
2537         return(error);
2538 }
2539
2540 hammer_node_t
2541 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2542                         int *parent_indexp, int *errorp, int try_exclusive)
2543 {
2544         hammer_node_t parent;
2545         hammer_btree_elm_t elm;
2546         int i;
2547
2548         /*
2549          * Get the node
2550          */
2551         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2552         if (*errorp) {
2553                 KKASSERT(parent == NULL);
2554                 return(NULL);
2555         }
2556         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2557
2558         /*
2559          * Lock the node
2560          */
2561         if (try_exclusive) {
2562                 if (hammer_lock_ex_try(&parent->lock)) {
2563                         hammer_rel_node(parent);
2564                         *errorp = EDEADLK;
2565                         return(NULL);
2566                 }
2567         } else {
2568                 hammer_lock_sh(&parent->lock);
2569         }
2570
2571         /*
2572          * Figure out which element in the parent is pointing to the
2573          * child.
2574          */
2575         if (node->ondisk->count) {
2576                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2577                                              parent->ondisk);
2578         } else {
2579                 i = 0;
2580         }
2581         while (i < parent->ondisk->count) {
2582                 elm = &parent->ondisk->elms[i];
2583                 if (elm->internal.subtree_offset == node->node_offset)
2584                         break;
2585                 ++i;
2586         }
2587         if (i == parent->ondisk->count) {
2588                 hammer_unlock(&parent->lock);
2589                 panic("Bad B-Tree link: parent %p node %p", parent, node);
2590         }
2591         *parent_indexp = i;
2592         KKASSERT(*errorp == 0);
2593         return(parent);
2594 }
2595
2596 /*
2597  * The element (elm) has been moved to a new internal node (node).
2598  *
2599  * If the element represents a pointer to an internal node that node's
2600  * parent must be adjusted to the element's new location.
2601  *
2602  * XXX deadlock potential here with our exclusive locks
2603  */
2604 int
2605 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2606                  hammer_btree_elm_t elm)
2607 {
2608         hammer_node_t child;
2609         int error;
2610
2611         error = 0;
2612
2613         switch(elm->base.btype) {
2614         case HAMMER_BTREE_TYPE_INTERNAL:
2615         case HAMMER_BTREE_TYPE_LEAF:
2616                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2617                                         0, &error);
2618                 if (error == 0) {
2619                         hammer_modify_node_field(trans, child, parent);
2620                         child->ondisk->parent = node->node_offset;
2621                         hammer_modify_node_done(child);
2622                         hammer_rel_node(child);
2623                 }
2624                 break;
2625         default:
2626                 break;
2627         }
2628         return(error);
2629 }
2630
2631 /*
2632  * Initialize the root of a recursive B-Tree node lock list structure.
2633  */
2634 void
2635 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2636 {
2637         TAILQ_INIT(&parent->list);
2638         parent->parent = NULL;
2639         parent->node = node;
2640         parent->index = -1;
2641         parent->count = node->ondisk->count;
2642         parent->copy = NULL;
2643         parent->flags = 0;
2644 }
2645
2646 /*
2647  * Initialize a cache of hammer_node_lock's including space allocated
2648  * for node copies.
2649  *
2650  * This is used by the rebalancing code to preallocate the copy space
2651  * for ~4096 B-Tree nodes (16MB of data) prior to acquiring any HAMMER
2652  * locks, otherwise we can blow out the pageout daemon's emergency
2653  * reserve and deadlock it.
2654  *
2655  * NOTE: HAMMER_NODE_LOCK_LCACHE is not set on items cached in the lcache.
2656  *       The flag is set when the item is pulled off the cache for use.
2657  */
2658 void
2659 hammer_btree_lcache_init(hammer_mount_t hmp, hammer_node_lock_t lcache,
2660                          int depth)
2661 {
2662         hammer_node_lock_t item;
2663         int count;
2664
2665         for (count = 1; depth; --depth)
2666                 count *= HAMMER_BTREE_LEAF_ELMS;
2667         bzero(lcache, sizeof(*lcache));
2668         TAILQ_INIT(&lcache->list);
2669         while (count) {
2670                 item = kmalloc(sizeof(*item), hmp->m_misc, M_WAITOK|M_ZERO);
2671                 item->copy = kmalloc(sizeof(*item->copy),
2672                                      hmp->m_misc, M_WAITOK);
2673                 TAILQ_INIT(&item->list);
2674                 TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2675                 --count;
2676         }
2677 }
2678
2679 void
2680 hammer_btree_lcache_free(hammer_mount_t hmp, hammer_node_lock_t lcache)
2681 {
2682         hammer_node_lock_t item;
2683
2684         while ((item = TAILQ_FIRST(&lcache->list)) != NULL) {
2685                 TAILQ_REMOVE(&lcache->list, item, entry);
2686                 KKASSERT(item->copy);
2687                 KKASSERT(TAILQ_EMPTY(&item->list));
2688                 kfree(item->copy, hmp->m_misc);
2689                 kfree(item, hmp->m_misc);
2690         }
2691         KKASSERT(lcache->copy == NULL);
2692 }
2693
2694 /*
2695  * Exclusively lock all the children of node.  This is used by the split
2696  * code to prevent anyone from accessing the children of a cursor node
2697  * while we fix-up its parent offset.
2698  *
2699  * If we don't lock the children we can really mess up cursors which block
2700  * trying to cursor-up into our node.
2701  *
2702  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2703  * error is returned the cursor is adjusted to block on termination.
2704  *
2705  * The caller is responsible for managing parent->node, the root's node
2706  * is usually aliased from a cursor.
2707  */
2708 int
2709 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2710                            hammer_node_lock_t parent,
2711                            hammer_node_lock_t lcache)
2712 {
2713         hammer_node_t node;
2714         hammer_node_lock_t item;
2715         hammer_node_ondisk_t ondisk;
2716         hammer_btree_elm_t elm;
2717         hammer_node_t child;
2718         struct hammer_mount *hmp;
2719         int error;
2720         int i;
2721
2722         node = parent->node;
2723         ondisk = node->ondisk;
2724         error = 0;
2725         hmp = cursor->trans->hmp;
2726
2727         /*
2728          * We really do not want to block on I/O with exclusive locks held,
2729          * pre-get the children before trying to lock the mess.  This is
2730          * only done one-level deep for now.
2731          */
2732         for (i = 0; i < ondisk->count; ++i) {
2733                 ++hammer_stats_btree_elements;
2734                 elm = &ondisk->elms[i];
2735                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2736                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2737                         continue;
2738                 }
2739                 child = hammer_get_node(cursor->trans,
2740                                         elm->internal.subtree_offset,
2741                                         0, &error);
2742                 if (child)
2743                         hammer_rel_node(child);
2744         }
2745
2746         /*
2747          * Do it for real
2748          */
2749         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2750                 ++hammer_stats_btree_elements;
2751                 elm = &ondisk->elms[i];
2752
2753                 switch(elm->base.btype) {
2754                 case HAMMER_BTREE_TYPE_INTERNAL:
2755                 case HAMMER_BTREE_TYPE_LEAF:
2756                         KKASSERT(elm->internal.subtree_offset != 0);
2757                         child = hammer_get_node(cursor->trans,
2758                                                 elm->internal.subtree_offset,
2759                                                 0, &error);
2760                         break;
2761                 default:
2762                         child = NULL;
2763                         break;
2764                 }
2765                 if (child) {
2766                         if (hammer_lock_ex_try(&child->lock) != 0) {
2767                                 if (cursor->deadlk_node == NULL) {
2768                                         cursor->deadlk_node = child;
2769                                         hammer_ref_node(cursor->deadlk_node);
2770                                 }
2771                                 error = EDEADLK;
2772                                 hammer_rel_node(child);
2773                         } else {
2774                                 if (lcache) {
2775                                         item = TAILQ_FIRST(&lcache->list);
2776                                         KKASSERT(item != NULL);
2777                                         item->flags |= HAMMER_NODE_LOCK_LCACHE;
2778                                         TAILQ_REMOVE(&lcache->list,
2779                                                      item, entry);
2780                                 } else {
2781                                         item = kmalloc(sizeof(*item),
2782                                                        hmp->m_misc,
2783                                                        M_WAITOK|M_ZERO);
2784                                         TAILQ_INIT(&item->list);
2785                                 }
2786
2787                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2788                                 item->parent = parent;
2789                                 item->node = child;
2790                                 item->index = i;
2791                                 item->count = child->ondisk->count;
2792
2793                                 /*
2794                                  * Recurse (used by the rebalancing code)
2795                                  */
2796                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2797                                         error = hammer_btree_lock_children(
2798                                                         cursor,
2799                                                         depth - 1,
2800                                                         item,
2801                                                         lcache);
2802                                 }
2803                         }
2804                 }
2805         }
2806         if (error)
2807                 hammer_btree_unlock_children(hmp, parent, lcache);
2808         return(error);
2809 }
2810
2811 /*
2812  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2813  * including the parent.
2814  */
2815 void
2816 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2817 {
2818         hammer_mount_t hmp = cursor->trans->hmp;
2819         hammer_node_lock_t item;
2820
2821         if (parent->copy == NULL) {
2822                 KKASSERT((parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0);
2823                 parent->copy = kmalloc(sizeof(*parent->copy),
2824                                        hmp->m_misc, M_WAITOK);
2825         }
2826         KKASSERT((parent->flags & HAMMER_NODE_LOCK_UPDATED) == 0);
2827         *parent->copy = *parent->node->ondisk;
2828         TAILQ_FOREACH(item, &parent->list, entry) {
2829                 hammer_btree_lock_copy(cursor, item);
2830         }
2831 }
2832
2833 /*
2834  * Recursively sync modified copies to the media.
2835  */
2836 int
2837 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2838 {
2839         hammer_node_lock_t item;
2840         int count = 0;
2841
2842         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2843                 ++count;
2844                 hammer_modify_node_all(cursor->trans, parent->node);
2845                 *parent->node->ondisk = *parent->copy;
2846                 hammer_modify_node_done(parent->node);
2847                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2848                         hammer_flush_node(parent->node, 0);
2849                         hammer_delete_node(cursor->trans, parent->node);
2850                 }
2851         }
2852         TAILQ_FOREACH(item, &parent->list, entry) {
2853                 count += hammer_btree_sync_copy(cursor, item);
2854         }
2855         return(count);
2856 }
2857
2858 /*
2859  * Release previously obtained node locks.  The caller is responsible for
2860  * cleaning up parent->node itself (its usually just aliased from a cursor),
2861  * but this function will take care of the copies.
2862  *
2863  * NOTE: The root node is not placed in the lcache and node->copy is not
2864  *       deallocated when lcache != NULL.
2865  */
2866 void
2867 hammer_btree_unlock_children(hammer_mount_t hmp, hammer_node_lock_t parent,
2868                              hammer_node_lock_t lcache)
2869 {
2870         hammer_node_lock_t item;
2871         hammer_node_ondisk_t copy;
2872
2873         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2874                 TAILQ_REMOVE(&parent->list, item, entry);
2875                 hammer_btree_unlock_children(hmp, item, lcache);
2876                 hammer_unlock(&item->node->lock);
2877                 hammer_rel_node(item->node);
2878                 if (lcache) {
2879                         /*
2880                          * NOTE: When placing the item back in the lcache
2881                          *       the flag is cleared by the bzero().
2882                          *       Remaining fields are cleared as a safety
2883                          *       measure.
2884                          */
2885                         KKASSERT(item->flags & HAMMER_NODE_LOCK_LCACHE);
2886                         KKASSERT(TAILQ_EMPTY(&item->list));
2887                         copy = item->copy;
2888                         bzero(item, sizeof(*item));
2889                         TAILQ_INIT(&item->list);
2890                         item->copy = copy;
2891                         if (copy)
2892                                 bzero(copy, sizeof(*copy));
2893                         TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2894                 } else {
2895                         kfree(item, hmp->m_misc);
2896                 }
2897         }
2898         if (parent->copy && (parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0) {
2899                 kfree(parent->copy, hmp->m_misc);
2900                 parent->copy = NULL;    /* safety */
2901         }
2902 }
2903
2904 /************************************************************************
2905  *                         MISCELLANIOUS SUPPORT                        *
2906  ************************************************************************/
2907
2908 /*
2909  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2910  *
2911  * Note that for this particular function a return value of -1, 0, or +1
2912  * can denote a match if create_tid is otherwise discounted.  A create_tid
2913  * of zero is considered to be 'infinity' in comparisons.
2914  *
2915  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2916  */
2917 int
2918 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2919 {
2920         if (key1->localization < key2->localization)
2921                 return(-5);
2922         if (key1->localization > key2->localization)
2923                 return(5);
2924
2925         if (key1->obj_id < key2->obj_id)
2926                 return(-4);
2927         if (key1->obj_id > key2->obj_id)
2928                 return(4);
2929
2930         if (key1->rec_type < key2->rec_type)
2931                 return(-3);
2932         if (key1->rec_type > key2->rec_type)
2933                 return(3);
2934
2935         if (key1->key < key2->key)
2936                 return(-2);
2937         if (key1->key > key2->key)
2938                 return(2);
2939
2940         /*
2941          * A create_tid of zero indicates a record which is undeletable
2942          * and must be considered to have a value of positive infinity.
2943          */
2944         if (key1->create_tid == 0) {
2945                 if (key2->create_tid == 0)
2946                         return(0);
2947                 return(1);
2948         }
2949         if (key2->create_tid == 0)
2950                 return(-1);
2951         if (key1->create_tid < key2->create_tid)
2952                 return(-1);
2953         if (key1->create_tid > key2->create_tid)
2954                 return(1);
2955         return(0);
2956 }
2957
2958 /*
2959  * Test a timestamp against an element to determine whether the
2960  * element is visible.  A timestamp of 0 means 'infinity'.
2961  */
2962 int
2963 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2964 {
2965         if (asof == 0) {
2966                 if (base->delete_tid)
2967                         return(1);
2968                 return(0);
2969         }
2970         if (asof < base->create_tid)
2971                 return(-1);
2972         if (base->delete_tid && asof >= base->delete_tid)
2973                 return(1);
2974         return(0);
2975 }
2976
2977 /*
2978  * Create a separator half way inbetween key1 and key2.  For fields just
2979  * one unit apart, the separator will match key2.  key1 is on the left-hand
2980  * side and key2 is on the right-hand side.
2981  *
2982  * key2 must be >= the separator.  It is ok for the separator to match key2.
2983  *
2984  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2985  * key2.
2986  *
2987  * NOTE: It might be beneficial to just scrap this whole mess and just
2988  * set the separator to key2.
2989  */
2990 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2991         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2992
2993 static void
2994 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2995                       hammer_base_elm_t dest)
2996 {
2997         bzero(dest, sizeof(*dest));
2998
2999         dest->rec_type = key2->rec_type;
3000         dest->key = key2->key;
3001         dest->obj_id = key2->obj_id;
3002         dest->create_tid = key2->create_tid;
3003
3004         MAKE_SEPARATOR(key1, key2, dest, localization);
3005         if (key1->localization == key2->localization) {
3006                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
3007                 if (key1->obj_id == key2->obj_id) {
3008                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
3009                         if (key1->rec_type == key2->rec_type) {
3010                                 MAKE_SEPARATOR(key1, key2, dest, key);
3011                                 /*
3012                                  * Don't bother creating a separator for
3013                                  * create_tid, which also conveniently avoids
3014                                  * having to handle the create_tid == 0
3015                                  * (infinity) case.  Just leave create_tid
3016                                  * set to key2.
3017                                  *
3018                                  * Worst case, dest matches key2 exactly,
3019                                  * which is acceptable.
3020                                  */
3021                         }
3022                 }
3023         }
3024 }
3025
3026 #undef MAKE_SEPARATOR
3027
3028 /*
3029  * Return whether a generic internal or leaf node is full
3030  */
3031 static int
3032 btree_node_is_full(hammer_node_ondisk_t node)
3033 {
3034         switch(node->type) {
3035         case HAMMER_BTREE_TYPE_INTERNAL:
3036                 if (node->count == HAMMER_BTREE_INT_ELMS)
3037                         return(1);
3038                 break;
3039         case HAMMER_BTREE_TYPE_LEAF:
3040                 if (node->count == HAMMER_BTREE_LEAF_ELMS)
3041                         return(1);
3042                 break;
3043         default:
3044                 panic("illegal btree subtype");
3045         }
3046         return(0);
3047 }
3048
3049 #if 0
3050 static int
3051 btree_max_elements(u_int8_t type)
3052 {
3053         if (type == HAMMER_BTREE_TYPE_LEAF)
3054                 return(HAMMER_BTREE_LEAF_ELMS);
3055         if (type == HAMMER_BTREE_TYPE_INTERNAL)
3056                 return(HAMMER_BTREE_INT_ELMS);
3057         panic("btree_max_elements: bad type %d", type);
3058 }
3059 #endif
3060
3061 void
3062 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
3063 {
3064         hammer_btree_elm_t elm;
3065         int i;
3066
3067         kprintf("node %p count=%d parent=%016llx type=%c\n",
3068                 ondisk, ondisk->count,
3069                 (long long)ondisk->parent, ondisk->type);
3070
3071         /*
3072          * Dump both boundary elements if an internal node
3073          */
3074         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
3075                 for (i = 0; i <= ondisk->count; ++i) {
3076                         elm = &ondisk->elms[i];
3077                         hammer_print_btree_elm(elm, ondisk->type, i);
3078                 }
3079         } else {
3080                 for (i = 0; i < ondisk->count; ++i) {
3081                         elm = &ondisk->elms[i];
3082                         hammer_print_btree_elm(elm, ondisk->type, i);
3083                 }
3084         }
3085 }
3086
3087 void
3088 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
3089 {
3090         kprintf("  %2d", i);
3091         kprintf("\tobj_id       = %016llx\n", (long long)elm->base.obj_id);
3092         kprintf("\tkey          = %016llx\n", (long long)elm->base.key);
3093         kprintf("\tcreate_tid   = %016llx\n", (long long)elm->base.create_tid);
3094         kprintf("\tdelete_tid   = %016llx\n", (long long)elm->base.delete_tid);
3095         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
3096         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
3097         kprintf("\tbtype        = %02x (%c)\n",
3098                 elm->base.btype,
3099                 (elm->base.btype ? elm->base.btype : '?'));
3100         kprintf("\tlocalization = %02x\n", elm->base.localization);
3101
3102         switch(type) {
3103         case HAMMER_BTREE_TYPE_INTERNAL:
3104                 kprintf("\tsubtree_off  = %016llx\n",
3105                         (long long)elm->internal.subtree_offset);
3106                 break;
3107         case HAMMER_BTREE_TYPE_RECORD:
3108                 kprintf("\tdata_offset  = %016llx\n",
3109                         (long long)elm->leaf.data_offset);
3110                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
3111                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
3112                 break;
3113         }
3114 }