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