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);
  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          * The case where the data reference resolves to the same buffer
 768          * as the record reference must be handled.
 769          */
 770         node = cursor->node->ondisk;
 771         elm = &node->elms[cursor->index];
 772         cursor->data = NULL;
 773         hmp = cursor->node->hmp;
 774
 775         /*
 776          * There is nothing to extract for an internal element.
 777          */
 778         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 779                 return(EINVAL);
 780
 781         /*
 782          * Only record types have data.
 783          */
 784         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 785         cursor->leaf = &elm->leaf;
 786
 787         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 788                 return(0);
 789         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 790                 return(0);
 791         data_off = elm->leaf.data_offset;
 792         data_len = elm->leaf.data_len;
 793         if (data_off == 0)
 794                 return(0);
 795
 796         /*
 797          * Load the data
 798          */
 799         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 800         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 801                                         &error, &cursor->data_buffer);
 802
 803         /*
 804          * Mark the data buffer as not being meta-data if it isn't
 805          * meta-data (sometimes bulk data is accessed via a volume
 806          * block device).
 807          */
 808         if (error == 0) {
 809                 switch(elm->leaf.base.rec_type) {
 810                 case HAMMER_RECTYPE_DATA:
 811                 case HAMMER_RECTYPE_DB:
 812                         if ((data_off & HAMMER_ZONE_LARGE_DATA) == 0)
 813                                 break;
 814                         if (hammer_double_buffer == 0 ||
 815                             (cursor->flags & HAMMER_CURSOR_NOSWAPCACHE)) {
 816                                 hammer_io_notmeta(cursor->data_buffer);
 817                         }
 818                         break;
 819                 default:
 820                         break;
 821                 }
 822         }
 823
 824         /*
 825          * Deal with CRC errors on the extracted data.
 826          */
 827         if (error == 0 &&
 828             hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 829                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 830                         (long long)elm->leaf.data_offset, elm->leaf.data_len);
 831                 if (hammer_debug_critical)
 832                         Debugger("CRC FAILED: DATA");
 833                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 834                         error = EDOM;   /* less critical (mirroring) */
 835                 else
 836                         error = EIO;    /* critical */
 837         }
 838         return(error);
 839 }
 840
 841
 842 /*
 843  * Insert a leaf element into the B-Tree at the current cursor position.
 844  * The cursor is positioned such that the element at and beyond the cursor
 845  * are shifted to make room for the new record.
 846  *
 847  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 848  * flag set and that call must return ENOENT before this function can be
 849  * called. ENOSPC is returned if there is no room to insert a new record.
 850  *
 851  * The caller may depend on the cursor's exclusive lock after return to
 852  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 853  */
 854 int
 855 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 856                     int *doprop)
 857 {
 858         hammer_node_ondisk_t node;
 859         int i;
 860         int error;
 861
 862         *doprop = 0;
 863         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 864                 return(error);
 865         ++hammer_stats_btree_inserts;
 866
 867         /*
 868          * Insert the element at the leaf node and update the count in the
 869          * parent.  It is possible for parent to be NULL, indicating that
 870          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 871          * possible.  The root inode can never be deleted so the leaf should
 872          * never be empty.
 873          *
 874          * Remember that leaf nodes do not have boundaries.
 875          */
 876         hammer_modify_node_all(cursor->trans, cursor->node);
 877         node = cursor->node->ondisk;
 878         i = cursor->index;
 879         KKASSERT(elm->base.btype != 0);
 880         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 881         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 882         if (i != node->count) {
 883                 bcopy(&node->elms[i], &node->elms[i+1],
 884                       (node->count - i) * sizeof(*elm));
 885         }
 886         node->elms[i].leaf = *elm;
 887         ++node->count;
 888         hammer_cursor_inserted_element(cursor->node, i);
 889
 890         /*
 891          * Update the leaf node's aggregate mirror_tid for mirroring
 892          * support.
 893          */
 894         if (node->mirror_tid < elm->base.delete_tid) {
 895                 node->mirror_tid = elm->base.delete_tid;
 896                 *doprop = 1;
 897         }
 898         if (node->mirror_tid < elm->base.create_tid) {
 899                 node->mirror_tid = elm->base.create_tid;
 900                 *doprop = 1;
 901         }
 902         hammer_modify_node_done(cursor->node);
 903
 904         /*
 905          * Debugging sanity checks.
 906          */
 907         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 908         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 909         if (i) {
 910                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 911         }
 912         if (i != node->count - 1)
 913                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 914
 915         return(0);
 916 }
 917
 918 /*
 919  * Delete a record from the B-Tree at the current cursor position.
 920  * The cursor is positioned such that the current element is the one
 921  * to be deleted.
 922  *
 923  * On return the cursor will be positioned after the deleted element and
 924  * MAY point to an internal node.  It will be suitable for the continuation
 925  * of an iteration but not for an insertion or deletion.
 926  *
 927  * Deletions will attempt to partially rebalance the B-Tree in an upward
 928  * direction, but will terminate rather then deadlock.  Empty internal nodes
 929  * are never allowed by a deletion which deadlocks may end up giving us an
 930  * empty leaf.  The pruner will clean up and rebalance the tree.
 931  *
 932  * This function can return EDEADLK, requiring the caller to retry the
 933  * operation after clearing the deadlock.
 934  */
 935 int
 936 hammer_btree_delete(hammer_cursor_t cursor)
 937 {
 938         hammer_node_ondisk_t ondisk;
 939         hammer_node_t node;
 940         hammer_node_t parent __debugvar;
 941         int error;
 942         int i;
 943
 944         KKASSERT (cursor->trans->sync_lock_refs > 0);
 945         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 946                 return(error);
 947         ++hammer_stats_btree_deletes;
 948
 949         /*
 950          * Delete the element from the leaf node.
 951          *
 952          * Remember that leaf nodes do not have boundaries.
 953          */
 954         node = cursor->node;
 955         ondisk = node->ondisk;
 956         i = cursor->index;
 957
 958         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 959         KKASSERT(i >= 0 && i < ondisk->count);
 960         hammer_modify_node_all(cursor->trans, node);
 961         if (i + 1 != ondisk->count) {
 962                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 963                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 964         }
 965         --ondisk->count;
 966         hammer_modify_node_done(node);
 967         hammer_cursor_deleted_element(node, i);
 968
 969         /*
 970          * Validate local parent
 971          */
 972         if (ondisk->parent) {
 973                 parent = cursor->parent;
 974
 975                 KKASSERT(parent != NULL);
 976                 KKASSERT(parent->node_offset == ondisk->parent);
 977         }
 978
 979         /*
 980          * If the leaf becomes empty it must be detached from the parent,
 981          * potentially recursing through to the filesystem root.
 982          *
 983          * This may reposition the cursor at one of the parent's of the
 984          * current node.
 985          *
 986          * Ignore deadlock errors, that simply means that btree_remove
 987          * was unable to recurse and had to leave us with an empty leaf.
 988          */
 989         KKASSERT(cursor->index <= ondisk->count);
 990         if (ondisk->count == 0) {
 991                 error = btree_remove(cursor);
 992                 if (error == EDEADLK)
 993                         error = 0;
 994         } else {
 995                 error = 0;
 996         }
 997         KKASSERT(cursor->parent == NULL ||
 998                  cursor->parent_index < cursor->parent->ondisk->count);
 999         return(error);
1000 }
1001
1002 /*
1003  * PRIMARY B-TREE SEARCH SUPPORT PROCEDURE
1004  *
1005  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
1006  *
1007  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
1008  * iterates up the tree as necessary to properly position itself prior to
1009  * actually doing the sarch.
1010  *
1011  * INSERTIONS: The search will split full nodes and leaves on its way down
1012  * and guarentee that the leaf it ends up on is not full.  If we run out
1013  * of space the search continues to the leaf, but ENOSPC is returned.
1014  *
1015  * The search is only guarenteed to end up on a leaf if an error code of 0
1016  * is returned, or if inserting and an error code of ENOENT is returned.
1017  * Otherwise it can stop at an internal node.  On success a search returns
1018  * a leaf node.
1019  *
1020  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
1021  * filesystem, and it is not simple code.  Please note the following facts:
1022  *
1023  * - Internal node recursions have a boundary on the left AND right.  The
1024  *   right boundary is non-inclusive.  The create_tid is a generic part
1025  *   of the key for internal nodes.
1026  *
1027  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
1028  *   historical search.  ASOF and INSERT are mutually exclusive.  When
1029  *   doing an as-of lookup btree_search() checks for a right-edge boundary
1030  *   case.  If while recursing down the left-edge differs from the key
1031  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
1032  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
1033  *   The iteration backwards because as-of searches can wind up going
1034  *   down the wrong branch of the B-Tree.
1035  */
1036 static
1037 int
1038 btree_search(hammer_cursor_t cursor, int flags)
1039 {
1040         hammer_node_ondisk_t node;
1041         hammer_btree_elm_t elm;
1042         int error;
1043         int enospc = 0;
1044         int i;
1045         int r;
1046         int s;
1047
1048         flags |= cursor->flags;
1049         ++hammer_stats_btree_searches;
1050
1051         if (hammer_debug_btree) {
1052                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td=%p)\n",
1053                         (long long)cursor->node->node_offset,
1054                         cursor->index,
1055                         (long long)cursor->key_beg.obj_id,
1056                         cursor->key_beg.rec_type,
1057                         (long long)cursor->key_beg.key,
1058                         (long long)cursor->key_beg.create_tid,
1059                         cursor->key_beg.localization,
1060                         curthread
1061                 );
1062                 if (cursor->parent)
1063                     kprintf("SEARCHP  %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
1064                         (long long)cursor->parent->node_offset,
1065                         cursor->parent_index,
1066                         (long long)cursor->left_bound->obj_id,
1067                         (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
1068                         (long long)cursor->right_bound->obj_id,
1069                         (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
1070                         cursor->left_bound,
1071                         &cursor->parent->ondisk->elms[cursor->parent_index],
1072                         cursor->right_bound,
1073                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
1074                     );
1075         }
1076
1077         /*
1078          * Move our cursor up the tree until we find a node whos range covers
1079          * the key we are trying to locate.
1080          *
1081          * The left bound is inclusive, the right bound is non-inclusive.
1082          * It is ok to cursor up too far.
1083          */
1084         for (;;) {
1085                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
1086                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
1087                 if (r >= 0 && s < 0)
1088                         break;
1089                 KKASSERT(cursor->parent);
1090                 ++hammer_stats_btree_iterations;
1091                 error = hammer_cursor_up(cursor);
1092                 if (error)
1093                         goto done;
1094         }
1095
1096         /*
1097          * The delete-checks below are based on node, not parent.  Set the
1098          * initial delete-check based on the parent.
1099          */
1100         if (r == 1) {
1101                 KKASSERT(cursor->left_bound->create_tid != 1);
1102                 cursor->create_check = cursor->left_bound->create_tid - 1;
1103                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1104         }
1105
1106         /*
1107          * We better have ended up with a node somewhere.
1108          */
1109         KKASSERT(cursor->node != NULL);
1110
1111         /*
1112          * If we are inserting we can't start at a full node if the parent
1113          * is also full (because there is no way to split the node),
1114          * continue running up the tree until the requirement is satisfied
1115          * or we hit the root of the filesystem.
1116          *
1117          * (If inserting we aren't doing an as-of search so we don't have
1118          *  to worry about create_check).
1119          */
1120         while (flags & HAMMER_CURSOR_INSERT) {
1121                 if (btree_node_is_full(cursor->node->ondisk) == 0)
1122                         break;
1123                 if (cursor->node->ondisk->parent == 0 ||
1124                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1125                         break;
1126                 }
1127                 ++hammer_stats_btree_iterations;
1128                 error = hammer_cursor_up(cursor);
1129                 /* node may have become stale */
1130                 if (error)
1131                         goto done;
1132         }
1133
1134         /*
1135          * Push down through internal nodes to locate the requested key.
1136          */
1137         node = cursor->node->ondisk;
1138         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1139                 /*
1140                  * Scan the node to find the subtree index to push down into.
1141                  * We go one-past, then back-up.
1142                  *
1143                  * We must proactively remove deleted elements which may
1144                  * have been left over from a deadlocked btree_remove().
1145                  *
1146                  * The left and right boundaries are included in the loop
1147                  * in order to detect edge cases.
1148                  *
1149                  * If the separator only differs by create_tid (r == 1)
1150                  * and we are doing an as-of search, we may end up going
1151                  * down a branch to the left of the one containing the
1152                  * desired key.  This requires numerous special cases.
1153                  */
1154                 ++hammer_stats_btree_iterations;
1155                 if (hammer_debug_btree) {
1156                         kprintf("SEARCH-I %016llx count=%d\n",
1157                                 (long long)cursor->node->node_offset,
1158                                 node->count);
1159                 }
1160
1161                 /*
1162                  * Try to shortcut the search before dropping into the
1163                  * linear loop.  Locate the first node where r <= 1.
1164                  */
1165                 i = hammer_btree_search_node(&cursor->key_beg, node);
1166                 while (i <= node->count) {
1167                         ++hammer_stats_btree_elements;
1168                         elm = &node->elms[i];
1169                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1170                         if (hammer_debug_btree > 2) {
1171                                 kprintf(" IELM %p %d r=%d\n",
1172                                         &node->elms[i], i, r);
1173                         }
1174                         if (r < 0)
1175                                 break;
1176                         if (r == 1) {
1177                                 KKASSERT(elm->base.create_tid != 1);
1178                                 cursor->create_check = elm->base.create_tid - 1;
1179                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1180                         }
1181                         ++i;
1182                 }
1183                 if (hammer_debug_btree) {
1184                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1185                                 i, node->count, r);
1186                 }
1187
1188                 /*
1189                  * These cases occur when the parent's idea of the boundary
1190                  * is wider then the child's idea of the boundary, and
1191                  * require special handling.  If not inserting we can
1192                  * terminate the search early for these cases but the
1193                  * child's boundaries cannot be unconditionally modified.
1194                  */
1195                 if (i == 0) {
1196                         /*
1197                          * If i == 0 the search terminated to the LEFT of the
1198                          * left_boundary but to the RIGHT of the parent's left
1199                          * boundary.
1200                          */
1201                         u_int8_t save;
1202
1203                         elm = &node->elms[0];
1204
1205                         /*
1206                          * If we aren't inserting we can stop here.
1207                          */
1208                         if ((flags & (HAMMER_CURSOR_INSERT |
1209                                       HAMMER_CURSOR_PRUNING)) == 0) {
1210                                 cursor->index = 0;
1211                                 return(ENOENT);
1212                         }
1213
1214                         /*
1215                          * Correct a left-hand boundary mismatch.
1216                          *
1217                          * We can only do this if we can upgrade the lock,
1218                          * and synchronized as a background cursor (i.e.
1219                          * inserting or pruning).
1220                          *
1221                          * WARNING: We can only do this if inserting, i.e.
1222                          * we are running on the backend.
1223                          */
1224                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1225                                 return(error);
1226                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1227                         hammer_modify_node_field(cursor->trans, cursor->node,
1228                                                  elms[0]);
1229                         save = node->elms[0].base.btype;
1230                         node->elms[0].base = *cursor->left_bound;
1231                         node->elms[0].base.btype = save;
1232                         hammer_modify_node_done(cursor->node);
1233                 } else if (i == node->count + 1) {
1234                         /*
1235                          * If i == node->count + 1 the search terminated to
1236                          * the RIGHT of the right boundary but to the LEFT
1237                          * of the parent's right boundary.  If we aren't
1238                          * inserting we can stop here.
1239                          *
1240                          * Note that the last element in this case is
1241                          * elms[i-2] prior to adjustments to 'i'.
1242                          */
1243                         --i;
1244                         if ((flags & (HAMMER_CURSOR_INSERT |
1245                                       HAMMER_CURSOR_PRUNING)) == 0) {
1246                                 cursor->index = i;
1247                                 return (ENOENT);
1248                         }
1249
1250                         /*
1251                          * Correct a right-hand boundary mismatch.
1252                          * (actual push-down record is i-2 prior to
1253                          * adjustments to i).
1254                          *
1255                          * We can only do this if we can upgrade the lock,
1256                          * and synchronized as a background cursor (i.e.
1257                          * inserting or pruning).
1258                          *
1259                          * WARNING: We can only do this if inserting, i.e.
1260                          * we are running on the backend.
1261                          */
1262                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1263                                 return(error);
1264                         elm = &node->elms[i];
1265                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1266                         hammer_modify_node(cursor->trans, cursor->node,
1267                                            &elm->base, sizeof(elm->base));
1268                         elm->base = *cursor->right_bound;
1269                         hammer_modify_node_done(cursor->node);
1270                         --i;
1271                 } else {
1272                         /*
1273                          * The push-down index is now i - 1.  If we had
1274                          * terminated on the right boundary this will point
1275                          * us at the last element.
1276                          */
1277                         --i;
1278                 }
1279                 cursor->index = i;
1280                 elm = &node->elms[i];
1281
1282                 if (hammer_debug_btree) {
1283                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1284                                 "key=%016llx cre=%016llx lo=%02x\n",
1285                                 (long long)cursor->node->node_offset,
1286                                 i,
1287                                 (long long)elm->internal.base.obj_id,
1288                                 elm->internal.base.rec_type,
1289                                 (long long)elm->internal.base.key,
1290                                 (long long)elm->internal.base.create_tid,
1291                                 elm->internal.base.localization
1292                         );
1293                 }
1294
1295                 /*
1296                  * We better have a valid subtree offset.
1297                  */
1298                 KKASSERT(elm->internal.subtree_offset != 0);
1299
1300                 /*
1301                  * Handle insertion and deletion requirements.
1302                  *
1303                  * If inserting split full nodes.  The split code will
1304                  * adjust cursor->node and cursor->index if the current
1305                  * index winds up in the new node.
1306                  *
1307                  * If inserting and a left or right edge case was detected,
1308                  * we cannot correct the left or right boundary and must
1309                  * prepend and append an empty leaf node in order to make
1310                  * the boundary correction.
1311                  *
1312                  * If we run out of space we set enospc but continue on
1313                  * to a leaf.
1314                  */
1315                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1316                         if (btree_node_is_full(node)) {
1317                                 error = btree_split_internal(cursor);
1318                                 if (error) {
1319                                         if (error != ENOSPC)
1320                                                 goto done;
1321                                         enospc = 1;
1322                                 }
1323                                 /*
1324                                  * reload stale pointers
1325                                  */
1326                                 i = cursor->index;
1327                                 node = cursor->node->ondisk;
1328                         }
1329                 }
1330
1331                 /*
1332                  * Push down (push into new node, existing node becomes
1333                  * the parent) and continue the search.
1334                  */
1335                 error = hammer_cursor_down(cursor);
1336                 /* node may have become stale */
1337                 if (error)
1338                         goto done;
1339                 node = cursor->node->ondisk;
1340         }
1341
1342         /*
1343          * We are at a leaf, do a linear search of the key array.
1344          *
1345          * On success the index is set to the matching element and 0
1346          * is returned.
1347          *
1348          * On failure the index is set to the insertion point and ENOENT
1349          * is returned.
1350          *
1351          * Boundaries are not stored in leaf nodes, so the index can wind
1352          * up to the left of element 0 (index == 0) or past the end of
1353          * the array (index == node->count).  It is also possible that the
1354          * leaf might be empty.
1355          */
1356         ++hammer_stats_btree_iterations;
1357         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1358         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1359         if (hammer_debug_btree) {
1360                 kprintf("SEARCH-L %016llx count=%d\n",
1361                         (long long)cursor->node->node_offset,
1362                         node->count);
1363         }
1364
1365         /*
1366          * Try to shortcut the search before dropping into the
1367          * linear loop.  Locate the first node where r <= 1.
1368          */
1369         i = hammer_btree_search_node(&cursor->key_beg, node);
1370         while (i < node->count) {
1371                 ++hammer_stats_btree_elements;
1372                 elm = &node->elms[i];
1373
1374                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1375
1376                 if (hammer_debug_btree > 1)
1377                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1378
1379                 /*
1380                  * We are at a record element.  Stop if we've flipped past
1381                  * key_beg, not counting the create_tid test.  Allow the
1382                  * r == 1 case (key_beg > element but differs only by its
1383                  * create_tid) to fall through to the AS-OF check.
1384                  */
1385                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1386
1387                 if (r < 0)
1388                         goto failed;
1389                 if (r > 1) {
1390                         ++i;
1391                         continue;
1392                 }
1393
1394                 /*
1395                  * Check our as-of timestamp against the element.
1396                  */
1397                 if (flags & HAMMER_CURSOR_ASOF) {
1398                         if (hammer_btree_chkts(cursor->asof,
1399                                                &node->elms[i].base) != 0) {
1400                                 ++i;
1401                                 continue;
1402                         }
1403                         /* success */
1404                 } else {
1405                         if (r > 0) {    /* can only be +1 */
1406                                 ++i;
1407                                 continue;
1408                         }
1409                         /* success */
1410                 }
1411                 cursor->index = i;
1412                 error = 0;
1413                 if (hammer_debug_btree) {
1414                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1415                                 (long long)cursor->node->node_offset, i);
1416                 }
1417                 goto done;
1418         }
1419
1420         /*
1421          * The search of the leaf node failed.  i is the insertion point.
1422          */
1423 failed:
1424         if (hammer_debug_btree) {
1425                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1426                         (long long)cursor->node->node_offset, i);
1427         }
1428
1429         /*
1430          * No exact match was found, i is now at the insertion point.
1431          *
1432          * If inserting split a full leaf before returning.  This
1433          * may have the side effect of adjusting cursor->node and
1434          * cursor->index.
1435          */
1436         cursor->index = i;
1437         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1438              btree_node_is_full(node)) {
1439                 error = btree_split_leaf(cursor);
1440                 if (error) {
1441                         if (error != ENOSPC)
1442                                 goto done;
1443                         enospc = 1;
1444                 }
1445                 /*
1446                  * reload stale pointers
1447                  */
1448                 /* NOT USED
1449                 i = cursor->index;
1450                 node = &cursor->node->internal;
1451                 */
1452         }
1453
1454         /*
1455          * We reached a leaf but did not find the key we were looking for.
1456          * If this is an insert we will be properly positioned for an insert
1457          * (ENOENT) or unable to insert (ENOSPC).
1458          */
1459         error = enospc ? ENOSPC : ENOENT;
1460 done:
1461         return(error);
1462 }
1463
1464 /*
1465  * Heuristical search for the first element whos comparison is <= 1.  May
1466  * return an index whos compare result is > 1 but may only return an index
1467  * whos compare result is <= 1 if it is the first element with that result.
1468  */
1469 int
1470 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1471 {
1472         int b;
1473         int s;
1474         int i;
1475         int r;
1476
1477         /*
1478          * Don't bother if the node does not have very many elements
1479          */
1480         b = 0;
1481         s = node->count;
1482         while (s - b > 4) {
1483                 i = b + (s - b) / 2;
1484                 ++hammer_stats_btree_elements;
1485                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1486                 if (r <= 1) {
1487                         s = i;
1488                 } else {
1489                         b = i;
1490                 }
1491         }
1492         return(b);
1493 }
1494
1495
1496 /************************************************************************
1497  *                         SPLITTING AND MERGING                        *
1498  ************************************************************************
1499  *
1500  * These routines do all the dirty work required to split and merge nodes.
1501  */
1502
1503 /*
1504  * Split an internal node into two nodes and move the separator at the split
1505  * point to the parent.
1506  *
1507  * (cursor->node, cursor->index) indicates the element the caller intends
1508  * to push into.  We will adjust node and index if that element winds
1509  * up in the split node.
1510  *
1511  * If we are at the root of the filesystem a new root must be created with
1512  * two elements, one pointing to the original root and one pointing to the
1513  * newly allocated split node.
1514  */
1515 static
1516 int
1517 btree_split_internal(hammer_cursor_t cursor)
1518 {
1519         hammer_node_ondisk_t ondisk;
1520         hammer_node_t node;
1521         hammer_node_t parent;
1522         hammer_node_t new_node;
1523         hammer_btree_elm_t elm;
1524         hammer_btree_elm_t parent_elm;
1525         struct hammer_node_lock lockroot;
1526         hammer_mount_t hmp = cursor->trans->hmp;
1527         int parent_index;
1528         int made_root;
1529         int split;
1530         int error;
1531         int i;
1532         const int esize = sizeof(*elm);
1533
1534         hammer_node_lock_init(&lockroot, cursor->node);
1535         error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
1536         if (error)
1537                 goto done;
1538         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1539                 goto done;
1540         ++hammer_stats_btree_splits;
1541
1542         /*
1543          * Calculate the split point.  If the insertion point is at the
1544          * end of the leaf we adjust the split point significantly to the
1545          * right to try to optimize node fill and flag it.  If we hit
1546          * that same leaf again our heuristic failed and we don't try
1547          * to optimize node fill (it could lead to a degenerate case).
1548          */
1549         node = cursor->node;
1550         ondisk = node->ondisk;
1551         KKASSERT(ondisk->count > 4);
1552         if (cursor->index == ondisk->count &&
1553             (node->flags & HAMMER_NODE_NONLINEAR) == 0) {
1554                 split = (ondisk->count + 1) * 3 / 4;
1555                 node->flags |= HAMMER_NODE_NONLINEAR;
1556         } else {
1557                 /*
1558                  * We are splitting but elms[split] will be promoted to
1559                  * the parent, leaving the right hand node with one less
1560                  * element.  If the insertion point will be on the
1561                  * left-hand side adjust the split point to give the
1562                  * right hand side one additional node.
1563                  */
1564                 split = (ondisk->count + 1) / 2;
1565                 if (cursor->index <= split)
1566                         --split;
1567         }
1568
1569         /*
1570          * If we are at the root of the filesystem, create a new root node
1571          * with 1 element and split normally.  Avoid making major
1572          * modifications until we know the whole operation will work.
1573          */
1574         if (ondisk->parent == 0) {
1575                 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1576                 if (parent == NULL)
1577                         goto done;
1578                 hammer_lock_ex(&parent->lock);
1579                 hammer_modify_node_noundo(cursor->trans, parent);
1580                 ondisk = parent->ondisk;
1581                 ondisk->count = 1;
1582                 ondisk->parent = 0;
1583                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1584                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1585                 ondisk->elms[0].base = hmp->root_btree_beg;
1586                 ondisk->elms[0].base.btype = node->ondisk->type;
1587                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1588                 ondisk->elms[0].internal.mirror_tid = ondisk->mirror_tid;
1589                 ondisk->elms[1].base = hmp->root_btree_end;
1590                 hammer_modify_node_done(parent);
1591                 /* ondisk->elms[1].base.btype - not used */
1592                 made_root = 1;
1593                 parent_index = 0;       /* index of current node in parent */
1594         } else {
1595                 made_root = 0;
1596                 parent = cursor->parent;
1597                 parent_index = cursor->parent_index;
1598         }
1599
1600         /*
1601          * Split node into new_node at the split point.
1602          *
1603          *  B O O O P N N B     <-- P = node->elms[split] (index 4)
1604          *   0 1 2 3 4 5 6      <-- subtree indices
1605          *
1606          *       x x P x x
1607          *        s S S s
1608          *         /   \
1609          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1610          *   0 1 2 3      4 5 6
1611          */
1612         new_node = hammer_alloc_btree(cursor->trans, 0, &error);
1613         if (new_node == NULL) {
1614                 if (made_root) {
1615                         hammer_unlock(&parent->lock);
1616                         hammer_delete_node(cursor->trans, parent);
1617                         hammer_rel_node(parent);
1618                 }
1619                 goto done;
1620         }
1621         hammer_lock_ex(&new_node->lock);
1622
1623         /*
1624          * Create the new node.  P becomes the left-hand boundary in the
1625          * new node.  Copy the right-hand boundary as well.
1626          *
1627          * elm is the new separator.
1628          */
1629         hammer_modify_node_noundo(cursor->trans, new_node);
1630         hammer_modify_node_all(cursor->trans, node);
1631         ondisk = node->ondisk;
1632         elm = &ondisk->elms[split];
1633         bcopy(elm, &new_node->ondisk->elms[0],
1634               (ondisk->count - split + 1) * esize);
1635         new_node->ondisk->count = ondisk->count - split;
1636         new_node->ondisk->parent = parent->node_offset;
1637         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1638         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1639         KKASSERT(ondisk->type == new_node->ondisk->type);
1640         hammer_cursor_split_node(node, new_node, split);
1641
1642         /*
1643          * Cleanup the original node.  Elm (P) becomes the new boundary,
1644          * its subtree_offset was moved to the new node.  If we had created
1645          * a new root its parent pointer may have changed.
1646          */
1647         elm->internal.subtree_offset = 0;
1648         ondisk->count = split;
1649
1650         /*
1651          * Insert the separator into the parent, fixup the parent's
1652          * reference to the original node, and reference the new node.
1653          * The separator is P.
1654          *
1655          * Remember that base.count does not include the right-hand boundary.
1656          */
1657         hammer_modify_node_all(cursor->trans, parent);
1658         ondisk = parent->ondisk;
1659         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1660         parent_elm = &ondisk->elms[parent_index+1];
1661         bcopy(parent_elm, parent_elm + 1,
1662               (ondisk->count - parent_index) * esize);
1663         parent_elm->internal.base = elm->base;  /* separator P */
1664         parent_elm->internal.base.btype = new_node->ondisk->type;
1665         parent_elm->internal.subtree_offset = new_node->node_offset;
1666         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1667         ++ondisk->count;
1668         hammer_modify_node_done(parent);
1669         hammer_cursor_inserted_element(parent, parent_index + 1);
1670
1671         /*
1672          * The children of new_node need their parent pointer set to new_node.
1673          * The children have already been locked by
1674          * hammer_btree_lock_children().
1675          */
1676         for (i = 0; i < new_node->ondisk->count; ++i) {
1677                 elm = &new_node->ondisk->elms[i];
1678                 error = btree_set_parent(cursor->trans, new_node, elm);
1679                 if (error) {
1680                         panic("btree_split_internal: btree-fixup problem");
1681                 }
1682         }
1683         hammer_modify_node_done(new_node);
1684
1685         /*
1686          * The filesystem's root B-Tree pointer may have to be updated.
1687          */
1688         if (made_root) {
1689                 hammer_volume_t volume;
1690
1691                 volume = hammer_get_root_volume(hmp, &error);
1692                 KKASSERT(error == 0);
1693
1694                 hammer_modify_volume_field(cursor->trans, volume,
1695                                            vol0_btree_root);
1696                 volume->ondisk->vol0_btree_root = parent->node_offset;
1697                 hammer_modify_volume_done(volume);
1698                 node->ondisk->parent = parent->node_offset;
1699                 if (cursor->parent) {
1700                         hammer_unlock(&cursor->parent->lock);
1701                         hammer_rel_node(cursor->parent);
1702                 }
1703                 cursor->parent = parent;        /* lock'd and ref'd */
1704                 hammer_rel_volume(volume, 0);
1705         }
1706         hammer_modify_node_done(node);
1707
1708         /*
1709          * Ok, now adjust the cursor depending on which element the original
1710          * index was pointing at.  If we are >= the split point the push node
1711          * is now in the new node.
1712          *
1713          * NOTE: If we are at the split point itself we cannot stay with the
1714          * original node because the push index will point at the right-hand
1715          * boundary, which is illegal.
1716          *
1717          * NOTE: The cursor's parent or parent_index must be adjusted for
1718          * the case where a new parent (new root) was created, and the case
1719          * where the cursor is now pointing at the split node.
1720          */
1721         if (cursor->index >= split) {
1722                 cursor->parent_index = parent_index + 1;
1723                 cursor->index -= split;
1724                 hammer_unlock(&cursor->node->lock);
1725                 hammer_rel_node(cursor->node);
1726                 cursor->node = new_node;        /* locked and ref'd */
1727         } else {
1728                 cursor->parent_index = parent_index;
1729                 hammer_unlock(&new_node->lock);
1730                 hammer_rel_node(new_node);
1731         }
1732
1733         /*
1734          * Fixup left and right bounds
1735          */
1736         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1737         cursor->left_bound = &parent_elm[0].internal.base;
1738         cursor->right_bound = &parent_elm[1].internal.base;
1739         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1740                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1741         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1742                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1743
1744 done:
1745         hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
1746         hammer_cursor_downgrade(cursor);
1747         return (error);
1748 }
1749
1750 /*
1751  * Same as the above, but splits a full leaf node.
1752  */
1753 static
1754 int
1755 btree_split_leaf(hammer_cursor_t cursor)
1756 {
1757         hammer_node_ondisk_t ondisk;
1758         hammer_node_t parent;
1759         hammer_node_t leaf;
1760         hammer_mount_t hmp;
1761         hammer_node_t new_leaf;
1762         hammer_btree_elm_t elm;
1763         hammer_btree_elm_t parent_elm;
1764         hammer_base_elm_t mid_boundary;
1765         int parent_index;
1766         int made_root;
1767         int split;
1768         int error;
1769         const size_t esize = sizeof(*elm);
1770
1771         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1772                 return(error);
1773         ++hammer_stats_btree_splits;
1774
1775         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1776                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1777         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1778                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1779
1780         /*
1781          * Calculate the split point.  If the insertion point is at the
1782          * end of the leaf we adjust the split point significantly to the
1783          * right to try to optimize node fill and flag it.  If we hit
1784          * that same leaf again our heuristic failed and we don't try
1785          * to optimize node fill (it could lead to a degenerate case).
1786          */
1787         leaf = cursor->node;
1788         ondisk = leaf->ondisk;
1789         KKASSERT(ondisk->count > 4);
1790         if (cursor->index == ondisk->count &&
1791             (leaf->flags & HAMMER_NODE_NONLINEAR) == 0) {
1792                 split = (ondisk->count + 1) * 3 / 4;
1793                 leaf->flags |= HAMMER_NODE_NONLINEAR;
1794         } else {
1795                 split = (ondisk->count + 1) / 2;
1796         }
1797
1798 #if 0
1799         /*
1800          * If the insertion point is at the split point shift the
1801          * split point left so we don't have to worry about
1802          */
1803         if (cursor->index == split)
1804                 --split;
1805 #endif
1806         KKASSERT(split > 0 && split < ondisk->count);
1807
1808         error = 0;
1809         hmp = leaf->hmp;
1810
1811         elm = &ondisk->elms[split];
1812
1813         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1814         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1815         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1816         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1817
1818         /*
1819          * If we are at the root of the tree, create a new root node with
1820          * 1 element and split normally.  Avoid making major modifications
1821          * until we know the whole operation will work.
1822          */
1823         if (ondisk->parent == 0) {
1824                 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1825                 if (parent == NULL)
1826                         goto done;
1827                 hammer_lock_ex(&parent->lock);
1828                 hammer_modify_node_noundo(cursor->trans, parent);
1829                 ondisk = parent->ondisk;
1830                 ondisk->count = 1;
1831                 ondisk->parent = 0;
1832                 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1833                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1834                 ondisk->elms[0].base = hmp->root_btree_beg;
1835                 ondisk->elms[0].base.btype = leaf->ondisk->type;
1836                 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1837                 ondisk->elms[0].internal.mirror_tid = ondisk->mirror_tid;
1838                 ondisk->elms[1].base = hmp->root_btree_end;
1839                 /* ondisk->elms[1].base.btype = not used */
1840                 hammer_modify_node_done(parent);
1841                 made_root = 1;
1842                 parent_index = 0;       /* insertion point in parent */
1843         } else {
1844                 made_root = 0;
1845                 parent = cursor->parent;
1846                 parent_index = cursor->parent_index;
1847         }
1848
1849         /*
1850          * Split leaf into new_leaf at the split point.  Select a separator
1851          * value in-between the two leafs but with a bent towards the right
1852          * leaf since comparisons use an 'elm >= separator' inequality.
1853          *
1854          *  L L L L L L L L
1855          *
1856          *       x x P x x
1857          *        s S S s
1858          *         /   \
1859          *  L L L L     L L L L
1860          */
1861         new_leaf = hammer_alloc_btree(cursor->trans, 0, &error);
1862         if (new_leaf == NULL) {
1863                 if (made_root) {
1864                         hammer_unlock(&parent->lock);
1865                         hammer_delete_node(cursor->trans, parent);
1866                         hammer_rel_node(parent);
1867                 }
1868                 goto done;
1869         }
1870         hammer_lock_ex(&new_leaf->lock);
1871
1872         /*
1873          * Create the new node and copy the leaf elements from the split
1874          * point on to the new node.
1875          */
1876         hammer_modify_node_all(cursor->trans, leaf);
1877         hammer_modify_node_noundo(cursor->trans, new_leaf);
1878         ondisk = leaf->ondisk;
1879         elm = &ondisk->elms[split];
1880         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1881         new_leaf->ondisk->count = ondisk->count - split;
1882         new_leaf->ondisk->parent = parent->node_offset;
1883         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1884         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1885         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1886         hammer_modify_node_done(new_leaf);
1887         hammer_cursor_split_node(leaf, new_leaf, split);
1888
1889         /*
1890          * Cleanup the original node.  Because this is a leaf node and
1891          * leaf nodes do not have a right-hand boundary, there
1892          * aren't any special edge cases to clean up.  We just fixup the
1893          * count.
1894          */
1895         ondisk->count = split;
1896
1897         /*
1898          * Insert the separator into the parent, fixup the parent's
1899          * reference to the original node, and reference the new node.
1900          * The separator is P.
1901          *
1902          * Remember that base.count does not include the right-hand boundary.
1903          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1904          */
1905         hammer_modify_node_all(cursor->trans, parent);
1906         ondisk = parent->ondisk;
1907         KKASSERT(split != 0);
1908         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1909         parent_elm = &ondisk->elms[parent_index+1];
1910         bcopy(parent_elm, parent_elm + 1,
1911               (ondisk->count - parent_index) * esize);
1912
1913         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1914         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1915         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1916         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1917         mid_boundary = &parent_elm->base;
1918         ++ondisk->count;
1919         hammer_modify_node_done(parent);
1920         hammer_cursor_inserted_element(parent, parent_index + 1);
1921
1922         /*
1923          * The filesystem's root B-Tree pointer may have to be updated.
1924          */
1925         if (made_root) {
1926                 hammer_volume_t volume;
1927
1928                 volume = hammer_get_root_volume(hmp, &error);
1929                 KKASSERT(error == 0);
1930
1931                 hammer_modify_volume_field(cursor->trans, volume,
1932                                            vol0_btree_root);
1933                 volume->ondisk->vol0_btree_root = parent->node_offset;
1934                 hammer_modify_volume_done(volume);
1935                 leaf->ondisk->parent = parent->node_offset;
1936                 if (cursor->parent) {
1937                         hammer_unlock(&cursor->parent->lock);
1938                         hammer_rel_node(cursor->parent);
1939                 }
1940                 cursor->parent = parent;        /* lock'd and ref'd */
1941                 hammer_rel_volume(volume, 0);
1942         }
1943         hammer_modify_node_done(leaf);
1944
1945         /*
1946          * Ok, now adjust the cursor depending on which element the original
1947          * index was pointing at.  If we are >= the split point the push node
1948          * is now in the new node.
1949          *
1950          * NOTE: If we are at the split point itself we need to select the
1951          * old or new node based on where key_beg's insertion point will be.
1952          * If we pick the wrong side the inserted element will wind up in
1953          * the wrong leaf node and outside that node's bounds.
1954          */
1955         if (cursor->index > split ||
1956             (cursor->index == split &&
1957              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1958                 cursor->parent_index = parent_index + 1;
1959                 cursor->index -= split;
1960                 hammer_unlock(&cursor->node->lock);
1961                 hammer_rel_node(cursor->node);
1962                 cursor->node = new_leaf;
1963         } else {
1964                 cursor->parent_index = parent_index;
1965                 hammer_unlock(&new_leaf->lock);
1966                 hammer_rel_node(new_leaf);
1967         }
1968
1969         /*
1970          * Fixup left and right bounds
1971          */
1972         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1973         cursor->left_bound = &parent_elm[0].internal.base;
1974         cursor->right_bound = &parent_elm[1].internal.base;
1975
1976         /*
1977          * Assert that the bounds are correct.
1978          */
1979         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1980                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1981         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1982                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1983         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
1984         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
1985
1986 done:
1987         hammer_cursor_downgrade(cursor);
1988         return (error);
1989 }
1990
1991 #if 0
1992
1993 /*
1994  * Recursively correct the right-hand boundary's create_tid to (tid) as
1995  * long as the rest of the key matches.  We have to recurse upward in
1996  * the tree as well as down the left side of each parent's right node.
1997  *
1998  * Return EDEADLK if we were only partially successful, forcing the caller
1999  * to try again.  The original cursor is not modified.  This routine can
2000  * also fail with EDEADLK if it is forced to throw away a portion of its
2001  * record history.
2002  *
2003  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
2004  */
2005 struct hammer_rhb {
2006         TAILQ_ENTRY(hammer_rhb) entry;
2007         hammer_node_t   node;
2008         int             index;
2009 };
2010
2011 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
2012
2013 int
2014 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
2015 {
2016         struct hammer_mount *hmp;
2017         struct hammer_rhb_list rhb_list;
2018         hammer_base_elm_t elm;
2019         hammer_node_t orig_node;
2020         struct hammer_rhb *rhb;
2021         int orig_index;
2022         int error;
2023
2024         TAILQ_INIT(&rhb_list);
2025         hmp = cursor->trans->hmp;
2026
2027         /*
2028          * Save our position so we can restore it on return.  This also
2029          * gives us a stable 'elm'.
2030          */
2031         orig_node = cursor->node;
2032         hammer_ref_node(orig_node);
2033         hammer_lock_sh(&orig_node->lock);
2034         orig_index = cursor->index;
2035         elm = &orig_node->ondisk->elms[orig_index].base;
2036
2037         /*
2038          * Now build a list of parents going up, allocating a rhb
2039          * structure for each one.
2040          */
2041         while (cursor->parent) {
2042                 /*
2043                  * Stop if we no longer have any right-bounds to fix up
2044                  */
2045                 if (elm->obj_id != cursor->right_bound->obj_id ||
2046                     elm->rec_type != cursor->right_bound->rec_type ||
2047                     elm->key != cursor->right_bound->key) {
2048                         break;
2049                 }
2050
2051                 /*
2052                  * Stop if the right-hand bound's create_tid does not
2053                  * need to be corrected.
2054                  */
2055                 if (cursor->right_bound->create_tid >= tid)
2056                         break;
2057
2058                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2059                 rhb->node = cursor->parent;
2060                 rhb->index = cursor->parent_index;
2061                 hammer_ref_node(rhb->node);
2062                 hammer_lock_sh(&rhb->node->lock);
2063                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2064
2065                 hammer_cursor_up(cursor);
2066         }
2067
2068         /*
2069          * now safely adjust the right hand bound for each rhb.  This may
2070          * also require taking the right side of the tree and iterating down
2071          * ITS left side.
2072          */
2073         error = 0;
2074         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2075                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2076                 if (error)
2077                         break;
2078                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2079                 hammer_unlock(&rhb->node->lock);
2080                 hammer_rel_node(rhb->node);
2081                 kfree(rhb, hmp->m_misc);
2082
2083                 switch (cursor->node->ondisk->type) {
2084                 case HAMMER_BTREE_TYPE_INTERNAL:
2085                         /*
2086                          * Right-boundary for parent at internal node
2087                          * is one element to the right of the element whos
2088                          * right boundary needs adjusting.  We must then
2089                          * traverse down the left side correcting any left
2090                          * bounds (which may now be too far to the left).
2091                          */
2092                         ++cursor->index;
2093                         error = hammer_btree_correct_lhb(cursor, tid);
2094                         break;
2095                 default:
2096                         panic("hammer_btree_correct_rhb(): Bad node type");
2097                         error = EINVAL;
2098                         break;
2099                 }
2100         }
2101
2102         /*
2103          * Cleanup
2104          */
2105         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2106                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2107                 hammer_unlock(&rhb->node->lock);
2108                 hammer_rel_node(rhb->node);
2109                 kfree(rhb, hmp->m_misc);
2110         }
2111         error = hammer_cursor_seek(cursor, orig_node, orig_index);
2112         hammer_unlock(&orig_node->lock);
2113         hammer_rel_node(orig_node);
2114         return (error);
2115 }
2116
2117 /*
2118  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2119  * bound going downward starting at the current cursor position.
2120  *
2121  * This function does not restore the cursor after use.
2122  */
2123 int
2124 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2125 {
2126         struct hammer_rhb_list rhb_list;
2127         hammer_base_elm_t elm;
2128         hammer_base_elm_t cmp;
2129         struct hammer_rhb *rhb;
2130         struct hammer_mount *hmp;
2131         int error;
2132
2133         TAILQ_INIT(&rhb_list);
2134         hmp = cursor->trans->hmp;
2135
2136         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2137
2138         /*
2139          * Record the node and traverse down the left-hand side for all
2140          * matching records needing a boundary correction.
2141          */
2142         error = 0;
2143         for (;;) {
2144                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2145                 rhb->node = cursor->node;
2146                 rhb->index = cursor->index;
2147                 hammer_ref_node(rhb->node);
2148                 hammer_lock_sh(&rhb->node->lock);
2149                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2150
2151                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2152                         /*
2153                          * Nothing to traverse down if we are at the right
2154                          * boundary of an internal node.
2155                          */
2156                         if (cursor->index == cursor->node->ondisk->count)
2157                                 break;
2158                 } else {
2159                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2160                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2161                                 break;
2162                         panic("Illegal leaf record type %02x", elm->btype);
2163                 }
2164                 error = hammer_cursor_down(cursor);
2165                 if (error)
2166                         break;
2167
2168                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2169                 if (elm->obj_id != cmp->obj_id ||
2170                     elm->rec_type != cmp->rec_type ||
2171                     elm->key != cmp->key) {
2172                         break;
2173                 }
2174                 if (elm->create_tid >= tid)
2175                         break;
2176
2177         }
2178
2179         /*
2180          * Now we can safely adjust the left-hand boundary from the bottom-up.
2181          * The last element we remove from the list is the caller's right hand
2182          * boundary, which must also be adjusted.
2183          */
2184         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2185                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2186                 if (error)
2187                         break;
2188                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2189                 hammer_unlock(&rhb->node->lock);
2190                 hammer_rel_node(rhb->node);
2191                 kfree(rhb, hmp->m_misc);
2192
2193                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2194                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2195                         hammer_modify_node(cursor->trans, cursor->node,
2196                                            &elm->create_tid,
2197                                            sizeof(elm->create_tid));
2198                         elm->create_tid = tid;
2199                         hammer_modify_node_done(cursor->node);
2200                 } else {
2201                         panic("hammer_btree_correct_lhb(): Bad element type");
2202                 }
2203         }
2204
2205         /*
2206          * Cleanup
2207          */
2208         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2209                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2210                 hammer_unlock(&rhb->node->lock);
2211                 hammer_rel_node(rhb->node);
2212                 kfree(rhb, hmp->m_misc);
2213         }
2214         return (error);
2215 }
2216
2217 #endif
2218
2219 /*
2220  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2221  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2222  * the operation due to a deadlock, or some other error.
2223  *
2224  * This routine is initially called with an empty leaf and may be
2225  * recursively called with single-element internal nodes.
2226  *
2227  * It should also be noted that when removing empty leaves we must be sure
2228  * to test and update mirror_tid because another thread may have deadlocked
2229  * against us (or someone) trying to propagate it up and cannot retry once
2230  * the node has been deleted.
2231  *
2232  * On return the cursor may end up pointing to an internal node, suitable
2233  * for further iteration but not for an immediate insertion or deletion.
2234  */
2235 static int
2236 btree_remove(hammer_cursor_t cursor)
2237 {
2238         hammer_node_ondisk_t ondisk;
2239         hammer_btree_elm_t elm;
2240         hammer_node_t node;
2241         hammer_node_t parent;
2242         const int esize = sizeof(*elm);
2243         int error;
2244
2245         node = cursor->node;
2246
2247         /*
2248          * When deleting the root of the filesystem convert it to
2249          * an empty leaf node.  Internal nodes cannot be empty.
2250          */
2251         ondisk = node->ondisk;
2252         if (ondisk->parent == 0) {
2253                 KKASSERT(cursor->parent == NULL);
2254                 hammer_modify_node_all(cursor->trans, node);
2255                 KKASSERT(ondisk == node->ondisk);
2256                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2257                 ondisk->count = 0;
2258                 hammer_modify_node_done(node);
2259                 cursor->index = 0;
2260                 return(0);
2261         }
2262
2263         parent = cursor->parent;
2264
2265         /*
2266          * Attempt to remove the parent's reference to the child.  If the
2267          * parent would become empty we have to recurse.  If we fail we
2268          * leave the parent pointing to an empty leaf node.
2269          *
2270          * We have to recurse successfully before we can delete the internal
2271          * node as it is illegal to have empty internal nodes.  Even though
2272          * the operation may be aborted we must still fixup any unlocked
2273          * cursors as if we had deleted the element prior to recursing
2274          * (by calling hammer_cursor_deleted_element()) so those cursors
2275          * are properly forced up the chain by the recursion.
2276          */
2277         if (parent->ondisk->count == 1) {
2278                 /*
2279                  * This special cursor_up_locked() call leaves the original
2280                  * node exclusively locked and referenced, leaves the
2281                  * original parent locked (as the new node), and locks the
2282                  * new parent.  It can return EDEADLK.
2283                  *
2284                  * We cannot call hammer_cursor_removed_node() until we are
2285                  * actually able to remove the node.  If we did then tracked
2286                  * cursors in the middle of iterations could be repointed
2287                  * to a parent node.  If this occurs they could end up
2288                  * scanning newly inserted records into the node (that could
2289                  * not be deleted) when they push down again.
2290                  *
2291                  * Due to the way the recursion works the final parent is left
2292                  * in cursor->parent after the recursion returns.  Each
2293                  * layer on the way back up is thus able to call
2294                  * hammer_cursor_removed_node() and 'jump' the node up to
2295                  * the (same) final parent.
2296                  *
2297                  * NOTE!  The local variable 'parent' is invalid after we
2298                  *        call hammer_cursor_up_locked().
2299                  */
2300                 error = hammer_cursor_up_locked(cursor);
2301                 parent = NULL;
2302
2303                 if (error == 0) {
2304                         hammer_cursor_deleted_element(cursor->node, 0);
2305                         error = btree_remove(cursor);
2306                         if (error == 0) {
2307                                 KKASSERT(node != cursor->node);
2308                                 hammer_cursor_removed_node(
2309                                         node, cursor->node,
2310                                         cursor->index);
2311                                 hammer_modify_node_all(cursor->trans, node);
2312                                 ondisk = node->ondisk;
2313                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2314                                 ondisk->count = 0;
2315                                 hammer_modify_node_done(node);
2316                                 hammer_flush_node(node, 0);
2317                                 hammer_delete_node(cursor->trans, node);
2318                         } else {
2319                                 /*
2320                                  * Defer parent removal because we could not
2321                                  * get the lock, just let the leaf remain
2322                                  * empty.
2323                                  */
2324                                 /**/
2325                         }
2326                         hammer_unlock(&node->lock);
2327                         hammer_rel_node(node);
2328                 } else {
2329                         /*
2330                          * Defer parent removal because we could not
2331                          * get the lock, just let the leaf remain
2332                          * empty.
2333                          */
2334                         /**/
2335                 }
2336         } else {
2337                 KKASSERT(parent->ondisk->count > 1);
2338
2339                 hammer_modify_node_all(cursor->trans, parent);
2340                 ondisk = parent->ondisk;
2341                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2342
2343                 elm = &ondisk->elms[cursor->parent_index];
2344                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2345                 KKASSERT(ondisk->count > 0);
2346
2347                 /*
2348                  * We must retain the highest mirror_tid.  The deleted
2349                  * range is now encompassed by the element to the left.
2350                  * If we are already at the left edge the new left edge
2351                  * inherits mirror_tid.
2352                  *
2353                  * Note that bounds of the parent to our parent may create
2354                  * a gap to the left of our left-most node or to the right
2355                  * of our right-most node.  The gap is silently included
2356                  * in the mirror_tid's area of effect from the point of view
2357                  * of the scan.
2358                  */
2359                 if (cursor->parent_index) {
2360                         if (elm[-1].internal.mirror_tid <
2361                             elm[0].internal.mirror_tid) {
2362                                 elm[-1].internal.mirror_tid =
2363                                     elm[0].internal.mirror_tid;
2364                         }
2365                 } else {
2366                         if (elm[1].internal.mirror_tid <
2367                             elm[0].internal.mirror_tid) {
2368                                 elm[1].internal.mirror_tid =
2369                                     elm[0].internal.mirror_tid;
2370                         }
2371                 }
2372
2373                 /*
2374                  * Delete the subtree reference in the parent.  Include
2375                  * boundary element at end.
2376                  */
2377                 bcopy(&elm[1], &elm[0],
2378                       (ondisk->count - cursor->parent_index) * esize);
2379                 --ondisk->count;
2380                 hammer_modify_node_done(parent);
2381                 hammer_cursor_removed_node(node, parent, cursor->parent_index);
2382                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2383                 hammer_flush_node(node, 0);
2384                 hammer_delete_node(cursor->trans, node);
2385
2386                 /*
2387                  * cursor->node is invalid, cursor up to make the cursor
2388                  * valid again.  We have to flag the condition in case
2389                  * another thread wiggles an insertion in during an
2390                  * iteration.
2391                  */
2392                 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
2393                 error = hammer_cursor_up(cursor);
2394         }
2395         return (error);
2396 }
2397
2398 /*
2399  * Propagate cursor->trans->tid up the B-Tree starting at the current
2400  * cursor position using pseudofs info gleaned from the passed inode.
2401  *
2402  * The passed inode has no relationship to the cursor position other
2403  * then being in the same pseudofs as the insertion or deletion we
2404  * are propagating the mirror_tid for.
2405  *
2406  * WARNING!  Because we push and pop the passed cursor, it may be
2407  *           modified by other B-Tree operations while it is unlocked
2408  *           and things like the node & leaf pointers, and indexes might
2409  *           change.
2410  */
2411 void
2412 hammer_btree_do_propagation(hammer_cursor_t cursor,
2413                             hammer_pseudofs_inmem_t pfsm,
2414                             hammer_btree_leaf_elm_t leaf)
2415 {
2416         hammer_cursor_t ncursor;
2417         hammer_tid_t mirror_tid;
2418         int error __debugvar;
2419
2420         /*
2421          * We do not propagate a mirror_tid if the filesystem was mounted
2422          * in no-mirror mode.
2423          */
2424         if (cursor->trans->hmp->master_id < 0)
2425                 return;
2426
2427         /*
2428          * This is a bit of a hack because we cannot deadlock or return
2429          * EDEADLK here.  The related operation has already completed and
2430          * we must propagate the mirror_tid now regardless.
2431          *
2432          * Generate a new cursor which inherits the original's locks and
2433          * unlock the original.  Use the new cursor to propagate the
2434          * mirror_tid.  Then clean up the new cursor and reacquire locks
2435          * on the original.
2436          *
2437          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2438          * original's locks and the original is tracked and must be
2439          * re-locked.
2440          */
2441         mirror_tid = cursor->node->ondisk->mirror_tid;
2442         KKASSERT(mirror_tid != 0);
2443         ncursor = hammer_push_cursor(cursor);
2444         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2445         KKASSERT(error == 0);
2446         hammer_pop_cursor(cursor, ncursor);
2447         /* WARNING: cursor's leaf pointer may change after pop */
2448 }
2449
2450
2451 /*
2452  * Propagate a mirror TID update upwards through the B-Tree to the root.
2453  *
2454  * A locked internal node must be passed in.  The node will remain locked
2455  * on return.
2456  *
2457  * This function syncs mirror_tid at the specified internal node's element,
2458  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2459  */
2460 static int
2461 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2462 {
2463         hammer_btree_internal_elm_t elm;
2464         hammer_node_t node;
2465         int error;
2466
2467         for (;;) {
2468                 error = hammer_cursor_up(cursor);
2469                 if (error == 0)
2470                         error = hammer_cursor_upgrade(cursor);
2471
2472                 /*
2473                  * We can ignore HAMMER_CURSOR_ITERATE_CHECK, the
2474                  * cursor will still be properly positioned for
2475                  * mirror propagation, just not for iterations.
2476                  */
2477                 while (error == EDEADLK) {
2478                         hammer_recover_cursor(cursor);
2479                         error = hammer_cursor_upgrade(cursor);
2480                 }
2481                 if (error)
2482                         break;
2483
2484                 /*
2485                  * If the cursor deadlocked it could end up at a leaf
2486                  * after we lost the lock.
2487                  */
2488                 node = cursor->node;
2489                 if (node->ondisk->type != HAMMER_BTREE_TYPE_INTERNAL)
2490                         continue;
2491
2492                 /*
2493                  * Adjust the node's element
2494                  */
2495                 elm = &node->ondisk->elms[cursor->index].internal;
2496                 if (elm->mirror_tid >= mirror_tid)
2497                         break;
2498                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2499                                    sizeof(elm->mirror_tid));
2500                 elm->mirror_tid = mirror_tid;
2501                 hammer_modify_node_done(node);
2502                 if (hammer_debug_general & 0x0002) {
2503                         kprintf("mirror_propagate: propagate "
2504                                 "%016llx @%016llx:%d\n",
2505                                 (long long)mirror_tid,
2506                                 (long long)node->node_offset,
2507                                 cursor->index);
2508                 }
2509
2510
2511                 /*
2512                  * Adjust the node's mirror_tid aggregator
2513                  */
2514                 if (node->ondisk->mirror_tid >= mirror_tid)
2515                         return(0);
2516                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2517                 node->ondisk->mirror_tid = mirror_tid;
2518                 hammer_modify_node_done(node);
2519                 if (hammer_debug_general & 0x0002) {
2520                         kprintf("mirror_propagate: propagate "
2521                                 "%016llx @%016llx\n",
2522                                 (long long)mirror_tid,
2523                                 (long long)node->node_offset);
2524                 }
2525         }
2526         if (error == ENOENT)
2527                 error = 0;
2528         return(error);
2529 }
2530
2531 hammer_node_t
2532 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2533                         int *parent_indexp, int *errorp, int try_exclusive)
2534 {
2535         hammer_node_t parent;
2536         hammer_btree_elm_t elm;
2537         int i;
2538
2539         /*
2540          * Get the node
2541          */
2542         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2543         if (*errorp) {
2544                 KKASSERT(parent == NULL);
2545                 return(NULL);
2546         }
2547         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2548
2549         /*
2550          * Lock the node
2551          */
2552         if (try_exclusive) {
2553                 if (hammer_lock_ex_try(&parent->lock)) {
2554                         hammer_rel_node(parent);
2555                         *errorp = EDEADLK;
2556                         return(NULL);
2557                 }
2558         } else {
2559                 hammer_lock_sh(&parent->lock);
2560         }
2561
2562         /*
2563          * Figure out which element in the parent is pointing to the
2564          * child.
2565          */
2566         if (node->ondisk->count) {
2567                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2568                                              parent->ondisk);
2569         } else {
2570                 i = 0;
2571         }
2572         while (i < parent->ondisk->count) {
2573                 elm = &parent->ondisk->elms[i];
2574                 if (elm->internal.subtree_offset == node->node_offset)
2575                         break;
2576                 ++i;
2577         }
2578         if (i == parent->ondisk->count) {
2579                 hammer_unlock(&parent->lock);
2580                 panic("Bad B-Tree link: parent %p node %p", parent, node);
2581         }
2582         *parent_indexp = i;
2583         KKASSERT(*errorp == 0);
2584         return(parent);
2585 }
2586
2587 /*
2588  * The element (elm) has been moved to a new internal node (node).
2589  *
2590  * If the element represents a pointer to an internal node that node's
2591  * parent must be adjusted to the element's new location.
2592  *
2593  * XXX deadlock potential here with our exclusive locks
2594  */
2595 int
2596 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2597                  hammer_btree_elm_t elm)
2598 {
2599         hammer_node_t child;
2600         int error;
2601
2602         error = 0;
2603
2604         switch(elm->base.btype) {
2605         case HAMMER_BTREE_TYPE_INTERNAL:
2606         case HAMMER_BTREE_TYPE_LEAF:
2607                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2608                                         0, &error);
2609                 if (error == 0) {
2610                         hammer_modify_node_field(trans, child, parent);
2611                         child->ondisk->parent = node->node_offset;
2612                         hammer_modify_node_done(child);
2613                         hammer_rel_node(child);
2614                 }
2615                 break;
2616         default:
2617                 break;
2618         }
2619         return(error);
2620 }
2621
2622 /*
2623  * Initialize the root of a recursive B-Tree node lock list structure.
2624  */
2625 void
2626 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2627 {
2628         TAILQ_INIT(&parent->list);
2629         parent->parent = NULL;
2630         parent->node = node;
2631         parent->index = -1;
2632         parent->count = node->ondisk->count;
2633         parent->copy = NULL;
2634         parent->flags = 0;
2635 }
2636
2637 /*
2638  * Initialize a cache of hammer_node_lock's including space allocated
2639  * for node copies.
2640  *
2641  * This is used by the rebalancing code to preallocate the copy space
2642  * for ~4096 B-Tree nodes (16MB of data) prior to acquiring any HAMMER
2643  * locks, otherwise we can blow out the pageout daemon's emergency
2644  * reserve and deadlock it.
2645  *
2646  * NOTE: HAMMER_NODE_LOCK_LCACHE is not set on items cached in the lcache.
2647  *       The flag is set when the item is pulled off the cache for use.
2648  */
2649 void
2650 hammer_btree_lcache_init(hammer_mount_t hmp, hammer_node_lock_t lcache,
2651                          int depth)
2652 {
2653         hammer_node_lock_t item;
2654         int count;
2655
2656         for (count = 1; depth; --depth)
2657                 count *= HAMMER_BTREE_LEAF_ELMS;
2658         bzero(lcache, sizeof(*lcache));
2659         TAILQ_INIT(&lcache->list);
2660         while (count) {
2661                 item = kmalloc(sizeof(*item), hmp->m_misc, M_WAITOK|M_ZERO);
2662                 item->copy = kmalloc(sizeof(*item->copy),
2663                                      hmp->m_misc, M_WAITOK);
2664                 TAILQ_INIT(&item->list);
2665                 TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2666                 --count;
2667         }
2668 }
2669
2670 void
2671 hammer_btree_lcache_free(hammer_mount_t hmp, hammer_node_lock_t lcache)
2672 {
2673         hammer_node_lock_t item;
2674
2675         while ((item = TAILQ_FIRST(&lcache->list)) != NULL) {
2676                 TAILQ_REMOVE(&lcache->list, item, entry);
2677                 KKASSERT(item->copy);
2678                 KKASSERT(TAILQ_EMPTY(&item->list));
2679                 kfree(item->copy, hmp->m_misc);
2680                 kfree(item, hmp->m_misc);
2681         }
2682         KKASSERT(lcache->copy == NULL);
2683 }
2684
2685 /*
2686  * Exclusively lock all the children of node.  This is used by the split
2687  * code to prevent anyone from accessing the children of a cursor node
2688  * while we fix-up its parent offset.
2689  *
2690  * If we don't lock the children we can really mess up cursors which block
2691  * trying to cursor-up into our node.
2692  *
2693  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2694  * error is returned the cursor is adjusted to block on termination.
2695  *
2696  * The caller is responsible for managing parent->node, the root's node
2697  * is usually aliased from a cursor.
2698  */
2699 int
2700 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2701                            hammer_node_lock_t parent,
2702                            hammer_node_lock_t lcache)
2703 {
2704         hammer_node_t node;
2705         hammer_node_lock_t item;
2706         hammer_node_ondisk_t ondisk;
2707         hammer_btree_elm_t elm;
2708         hammer_node_t child;
2709         struct hammer_mount *hmp;
2710         int error;
2711         int i;
2712
2713         node = parent->node;
2714         ondisk = node->ondisk;
2715         error = 0;
2716         hmp = cursor->trans->hmp;
2717
2718         /*
2719          * We really do not want to block on I/O with exclusive locks held,
2720          * pre-get the children before trying to lock the mess.  This is
2721          * only done one-level deep for now.
2722          */
2723         for (i = 0; i < ondisk->count; ++i) {
2724                 ++hammer_stats_btree_elements;
2725                 elm = &ondisk->elms[i];
2726                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2727                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2728                         continue;
2729                 }
2730                 child = hammer_get_node(cursor->trans,
2731                                         elm->internal.subtree_offset,
2732                                         0, &error);
2733                 if (child)
2734                         hammer_rel_node(child);
2735         }
2736
2737         /*
2738          * Do it for real
2739          */
2740         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2741                 ++hammer_stats_btree_elements;
2742                 elm = &ondisk->elms[i];
2743
2744                 switch(elm->base.btype) {
2745                 case HAMMER_BTREE_TYPE_INTERNAL:
2746                 case HAMMER_BTREE_TYPE_LEAF:
2747                         KKASSERT(elm->internal.subtree_offset != 0);
2748                         child = hammer_get_node(cursor->trans,
2749                                                 elm->internal.subtree_offset,
2750                                                 0, &error);
2751                         break;
2752                 default:
2753                         child = NULL;
2754                         break;
2755                 }
2756                 if (child) {
2757                         if (hammer_lock_ex_try(&child->lock) != 0) {
2758                                 if (cursor->deadlk_node == NULL) {
2759                                         cursor->deadlk_node = child;
2760                                         hammer_ref_node(cursor->deadlk_node);
2761                                 }
2762                                 error = EDEADLK;
2763                                 hammer_rel_node(child);
2764                         } else {
2765                                 if (lcache) {
2766                                         item = TAILQ_FIRST(&lcache->list);
2767                                         KKASSERT(item != NULL);
2768                                         item->flags |= HAMMER_NODE_LOCK_LCACHE;
2769                                         TAILQ_REMOVE(&lcache->list,
2770                                                      item, entry);
2771                                 } else {
2772                                         item = kmalloc(sizeof(*item),
2773                                                        hmp->m_misc,
2774                                                        M_WAITOK|M_ZERO);
2775                                         TAILQ_INIT(&item->list);
2776                                 }
2777
2778                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2779                                 item->parent = parent;
2780                                 item->node = child;
2781                                 item->index = i;
2782                                 item->count = child->ondisk->count;
2783
2784                                 /*
2785                                  * Recurse (used by the rebalancing code)
2786                                  */
2787                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2788                                         error = hammer_btree_lock_children(
2789                                                         cursor,
2790                                                         depth - 1,
2791                                                         item,
2792                                                         lcache);
2793                                 }
2794                         }
2795                 }
2796         }
2797         if (error)
2798                 hammer_btree_unlock_children(hmp, parent, lcache);
2799         return(error);
2800 }
2801
2802 /*
2803  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2804  * including the parent.
2805  */
2806 void
2807 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2808 {
2809         hammer_mount_t hmp = cursor->trans->hmp;
2810         hammer_node_lock_t item;
2811
2812         if (parent->copy == NULL) {
2813                 KKASSERT((parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0);
2814                 parent->copy = kmalloc(sizeof(*parent->copy),
2815                                        hmp->m_misc, M_WAITOK);
2816         }
2817         KKASSERT((parent->flags & HAMMER_NODE_LOCK_UPDATED) == 0);
2818         *parent->copy = *parent->node->ondisk;
2819         TAILQ_FOREACH(item, &parent->list, entry) {
2820                 hammer_btree_lock_copy(cursor, item);
2821         }
2822 }
2823
2824 /*
2825  * Recursively sync modified copies to the media.
2826  */
2827 int
2828 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2829 {
2830         hammer_node_lock_t item;
2831         int count = 0;
2832
2833         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2834                 ++count;
2835                 hammer_modify_node_all(cursor->trans, parent->node);
2836                 *parent->node->ondisk = *parent->copy;
2837                 hammer_modify_node_done(parent->node);
2838                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2839                         hammer_flush_node(parent->node, 0);
2840                         hammer_delete_node(cursor->trans, parent->node);
2841                 }
2842         }
2843         TAILQ_FOREACH(item, &parent->list, entry) {
2844                 count += hammer_btree_sync_copy(cursor, item);
2845         }
2846         return(count);
2847 }
2848
2849 /*
2850  * Release previously obtained node locks.  The caller is responsible for
2851  * cleaning up parent->node itself (its usually just aliased from a cursor),
2852  * but this function will take care of the copies.
2853  *
2854  * NOTE: The root node is not placed in the lcache and node->copy is not
2855  *       deallocated when lcache != NULL.
2856  */
2857 void
2858 hammer_btree_unlock_children(hammer_mount_t hmp, hammer_node_lock_t parent,
2859                              hammer_node_lock_t lcache)
2860 {
2861         hammer_node_lock_t item;
2862         hammer_node_ondisk_t copy;
2863
2864         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2865                 TAILQ_REMOVE(&parent->list, item, entry);
2866                 hammer_btree_unlock_children(hmp, item, lcache);
2867                 hammer_unlock(&item->node->lock);
2868                 hammer_rel_node(item->node);
2869                 if (lcache) {
2870                         /*
2871                          * NOTE: When placing the item back in the lcache
2872                          *       the flag is cleared by the bzero().
2873                          *       Remaining fields are cleared as a safety
2874                          *       measure.
2875                          */
2876                         KKASSERT(item->flags & HAMMER_NODE_LOCK_LCACHE);
2877                         KKASSERT(TAILQ_EMPTY(&item->list));
2878                         copy = item->copy;
2879                         bzero(item, sizeof(*item));
2880                         TAILQ_INIT(&item->list);
2881                         item->copy = copy;
2882                         if (copy)
2883                                 bzero(copy, sizeof(*copy));
2884                         TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2885                 } else {
2886                         kfree(item, hmp->m_misc);
2887                 }
2888         }
2889         if (parent->copy && (parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0) {
2890                 kfree(parent->copy, hmp->m_misc);
2891                 parent->copy = NULL;    /* safety */
2892         }
2893 }
2894
2895 /************************************************************************
2896  *                         MISCELLANIOUS SUPPORT                        *
2897  ************************************************************************/
2898
2899 /*
2900  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2901  *
2902  * Note that for this particular function a return value of -1, 0, or +1
2903  * can denote a match if create_tid is otherwise discounted.  A create_tid
2904  * of zero is considered to be 'infinity' in comparisons.
2905  *
2906  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2907  */
2908 int
2909 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2910 {
2911         if (key1->localization < key2->localization)
2912                 return(-5);
2913         if (key1->localization > key2->localization)
2914                 return(5);
2915
2916         if (key1->obj_id < key2->obj_id)
2917                 return(-4);
2918         if (key1->obj_id > key2->obj_id)
2919                 return(4);
2920
2921         if (key1->rec_type < key2->rec_type)
2922                 return(-3);
2923         if (key1->rec_type > key2->rec_type)
2924                 return(3);
2925
2926         if (key1->key < key2->key)
2927                 return(-2);
2928         if (key1->key > key2->key)
2929                 return(2);
2930
2931         /*
2932          * A create_tid of zero indicates a record which is undeletable
2933          * and must be considered to have a value of positive infinity.
2934          */
2935         if (key1->create_tid == 0) {
2936                 if (key2->create_tid == 0)
2937                         return(0);
2938                 return(1);
2939         }
2940         if (key2->create_tid == 0)
2941                 return(-1);
2942         if (key1->create_tid < key2->create_tid)
2943                 return(-1);
2944         if (key1->create_tid > key2->create_tid)
2945                 return(1);
2946         return(0);
2947 }
2948
2949 /*
2950  * Test a timestamp against an element to determine whether the
2951  * element is visible.  A timestamp of 0 means 'infinity'.
2952  */
2953 int
2954 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2955 {
2956         if (asof == 0) {
2957                 if (base->delete_tid)
2958                         return(1);
2959                 return(0);
2960         }
2961         if (asof < base->create_tid)
2962                 return(-1);
2963         if (base->delete_tid && asof >= base->delete_tid)
2964                 return(1);
2965         return(0);
2966 }
2967
2968 /*
2969  * Create a separator half way inbetween key1 and key2.  For fields just
2970  * one unit apart, the separator will match key2.  key1 is on the left-hand
2971  * side and key2 is on the right-hand side.
2972  *
2973  * key2 must be >= the separator.  It is ok for the separator to match key2.
2974  *
2975  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2976  * key2.
2977  *
2978  * NOTE: It might be beneficial to just scrap this whole mess and just
2979  * set the separator to key2.
2980  */
2981 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2982         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2983
2984 static void
2985 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2986                       hammer_base_elm_t dest)
2987 {
2988         bzero(dest, sizeof(*dest));
2989
2990         dest->rec_type = key2->rec_type;
2991         dest->key = key2->key;
2992         dest->obj_id = key2->obj_id;
2993         dest->create_tid = key2->create_tid;
2994
2995         MAKE_SEPARATOR(key1, key2, dest, localization);
2996         if (key1->localization == key2->localization) {
2997                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
2998                 if (key1->obj_id == key2->obj_id) {
2999                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
3000                         if (key1->rec_type == key2->rec_type) {
3001                                 MAKE_SEPARATOR(key1, key2, dest, key);
3002                                 /*
3003                                  * Don't bother creating a separator for
3004                                  * create_tid, which also conveniently avoids
3005                                  * having to handle the create_tid == 0
3006                                  * (infinity) case.  Just leave create_tid
3007                                  * set to key2.
3008                                  *
3009                                  * Worst case, dest matches key2 exactly,
3010                                  * which is acceptable.
3011                                  */
3012                         }
3013                 }
3014         }
3015 }
3016
3017 #undef MAKE_SEPARATOR
3018
3019 /*
3020  * Return whether a generic internal or leaf node is full
3021  */
3022 static __inline
3023 int
3024 btree_node_is_full(hammer_node_ondisk_t node)
3025 {
3026         return(btree_max_elements(node->type) == node->count);
3027 }
3028
3029 static __inline
3030 int
3031 btree_max_elements(u_int8_t type)
3032 {
3033         if (type == HAMMER_BTREE_TYPE_LEAF)
3034                 return(HAMMER_BTREE_LEAF_ELMS);
3035         if (type == HAMMER_BTREE_TYPE_INTERNAL)
3036                 return(HAMMER_BTREE_INT_ELMS);
3037         panic("btree_max_elements: bad type %d", type);
3038 }
3039
3040 void
3041 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
3042 {
3043         hammer_btree_elm_t elm;
3044         int i;
3045
3046         kprintf("node %p count=%d parent=%016llx type=%c\n",
3047                 ondisk, ondisk->count,
3048                 (long long)ondisk->parent, ondisk->type);
3049
3050         /*
3051          * Dump both boundary elements if an internal node
3052          */
3053         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
3054                 for (i = 0; i <= ondisk->count; ++i) {
3055                         elm = &ondisk->elms[i];
3056                         hammer_print_btree_elm(elm, ondisk->type, i);
3057                 }
3058         } else {
3059                 for (i = 0; i < ondisk->count; ++i) {
3060                         elm = &ondisk->elms[i];
3061                         hammer_print_btree_elm(elm, ondisk->type, i);
3062                 }
3063         }
3064 }
3065
3066 void
3067 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
3068 {
3069         kprintf("  %2d", i);
3070         kprintf("\tobj_id       = %016llx\n", (long long)elm->base.obj_id);
3071         kprintf("\tkey          = %016llx\n", (long long)elm->base.key);
3072         kprintf("\tcreate_tid   = %016llx\n", (long long)elm->base.create_tid);
3073         kprintf("\tdelete_tid   = %016llx\n", (long long)elm->base.delete_tid);
3074         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
3075         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
3076         kprintf("\tbtype        = %02x (%c)\n",
3077                 elm->base.btype,
3078                 (elm->base.btype ? elm->base.btype : '?'));
3079         kprintf("\tlocalization = %02x\n", elm->base.localization);
3080
3081         switch(type) {
3082         case HAMMER_BTREE_TYPE_INTERNAL:
3083                 kprintf("\tsubtree_off  = %016llx\n",
3084                         (long long)elm->internal.subtree_offset);
3085                 break;
3086         case HAMMER_BTREE_TYPE_RECORD:
3087                 kprintf("\tdata_offset  = %016llx\n",
3088                         (long long)elm->leaf.data_offset);
3089                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
3090                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
3091                 break;
3092         }
3093 }