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