sys/vfs/hammer/hammer_btree.c

   1 /*
   2  * Copyright (c) 2007-2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 /*
  36  * HAMMER B-Tree index
  37  *
  38  * HAMMER implements a modified B+Tree.  In documentation this will
  39  * simply be refered to as the HAMMER B-Tree.  Basically a HAMMER B-Tree
  40  * looks like a B+Tree (A B-Tree which stores its records only at the leafs
  41  * of the tree), but adds two additional boundary elements which describe
  42  * the left-most and right-most element a node is able to represent.  In
  43  * otherwords, we have boundary elements at the two ends of a B-Tree node
  44  * instead of sub-tree pointers.
  45  *
  46  * A B-Tree internal node looks like this:
  47  *
  48  *      B N N N N N N B   <-- boundary and internal elements
  49  *       S S S S S S S    <-- subtree pointers
  50  *
  51  * A B-Tree leaf node basically looks like this:
  52  *
  53  *      L L L L L L L L   <-- leaf elemenets
  54  *
  55  * The radix for an internal node is 1 less then a leaf but we get a
  56  * number of significant benefits for our troubles.
  57  *
  58  * The big benefit to using a B-Tree containing boundary information
  59  * is that it is possible to cache pointers into the middle of the tree
  60  * and not have to start searches, insertions, OR deletions at the root
  61  * node.   In particular, searches are able to progress in a definitive
  62  * direction from any point in the tree without revisting nodes.  This
  63  * greatly improves the efficiency of many operations, most especially
  64  * record appends.
  65  *
  66  * B-Trees also make the stacking of trees fairly straightforward.
  67  *
  68  * INSERTIONS:  A search performed with the intention of doing
  69  * an insert will guarantee that the terminal leaf node is not full by
  70  * splitting full nodes.  Splits occur top-down during the dive down the
  71  * B-Tree.
  72  *
  73  * DELETIONS: A deletion makes no attempt to proactively balance the
  74  * tree and will recursively remove nodes that become empty.  If a
  75  * deadlock occurs a deletion may not be able to remove an empty leaf.
  76  * Deletions never allow internal nodes to become empty (that would blow
  77  * up the boundaries).
  78  */
  79 #include "hammer.h"
  80 #include <sys/buf.h>
  81 #include <sys/buf2.h>
  82
  83 static int btree_search(hammer_cursor_t cursor, int flags);
  84 static int btree_split_internal(hammer_cursor_t cursor);
  85 static int btree_split_leaf(hammer_cursor_t cursor);
  86 static int btree_remove(hammer_cursor_t cursor);
  87 static int btree_node_is_full(hammer_node_ondisk_t node);
  88 static int hammer_btree_mirror_propagate(hammer_cursor_t cursor,
  89                         hammer_tid_t mirror_tid);
  90 static void hammer_make_separator(hammer_base_elm_t key1,
  91                         hammer_base_elm_t key2, hammer_base_elm_t dest);
  92 static void hammer_cursor_mirror_filter(hammer_cursor_t cursor);
  93
  94 /*
  95  * Iterate records after a search.  The cursor is iterated forwards past
  96  * the current record until a record matching the key-range requirements
  97  * is found.  ENOENT is returned if the iteration goes past the ending
  98  * key.
  99  *
 100  * The iteration is inclusive of key_beg and can be inclusive or exclusive
 101  * of key_end depending on whether HAMMER_CURSOR_END_INCLUSIVE is set.
 102  *
 103  * When doing an as-of search (cursor->asof != 0), key_beg.create_tid
 104  * may be modified by B-Tree functions.
 105  *
 106  * cursor->key_beg may or may not be modified by this function during
 107  * the iteration.  XXX future - in case of an inverted lock we may have
 108  * to reinitiate the lookup and set key_beg to properly pick up where we
 109  * left off.
 110  *
 111  * If HAMMER_CURSOR_ITERATE_CHECK is set it is possible that the cursor
 112  * was reverse indexed due to being moved to a parent while unlocked,
 113  * and something else might have inserted an element outside the iteration
 114  * range.  When this case occurs the iterator just keeps iterating until
 115  * it gets back into the iteration range (instead of asserting).
 116  *
 117  * NOTE!  EDEADLK *CANNOT* be returned by this procedure.
 118  */
 119 int
 120 hammer_btree_iterate(hammer_cursor_t cursor)
 121 {
 122         hammer_node_ondisk_t node;
 123         hammer_btree_elm_t elm;
 124         hammer_mount_t hmp;
 125         int error = 0;
 126         int r;
 127         int s;
 128
 129         /*
 130          * Skip past the current record
 131          */
 132         hmp = cursor->trans->hmp;
 133         node = cursor->node->ondisk;
 134         if (node == NULL)
 135                 return(ENOENT);
 136         if (cursor->index < node->count &&
 137             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 138                 ++cursor->index;
 139         }
 140
 141         /*
 142          * HAMMER can wind up being cpu-bound.
 143          */
 144         if (++hmp->check_yield > hammer_yield_check) {
 145                 hmp->check_yield = 0;
 146                 lwkt_user_yield();
 147         }
 148
 149
 150         /*
 151          * Loop until an element is found or we are done.
 152          */
 153         for (;;) {
 154                 /*
 155                  * We iterate up the tree and then index over one element
 156                  * while we are at the last element in the current node.
 157                  *
 158                  * If we are at the root of the filesystem, cursor_up
 159                  * returns ENOENT.
 160                  *
 161                  * XXX this could be optimized by storing the information in
 162                  * the parent reference.
 163                  *
 164                  * XXX we can lose the node lock temporarily, this could mess
 165                  * up our scan.
 166                  */
 167                 ++hammer_stats_btree_iterations;
 168                 hammer_flusher_clean_loose_ios(hmp);
 169
 170                 if (cursor->index == node->count) {
 171                         if (hammer_debug_btree) {
 172                                 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
 173                                         (long long)cursor->node->node_offset,
 174                                         cursor->index,
 175                                         (long long)(cursor->parent ? cursor->parent->node_offset : -1),
 176                                         cursor->parent_index,
 177                                         curthread);
 178                         }
 179                         KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
 180                         error = hammer_cursor_up(cursor);
 181                         if (error)
 182                                 break;
 183                         /* reload stale pointer */
 184                         node = cursor->node->ondisk;
 185                         KKASSERT(cursor->index != node->count);
 186
 187                         /*
 188                          * If we are reblocking we want to return internal
 189                          * nodes.  Note that the internal node will be
 190                          * returned multiple times, on each upward recursion
 191                          * from its children.  The caller selects which
 192                          * revisit it cares about (usually first or last only).
 193                          */
 194                         if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
 195                                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 196                                 return(0);
 197                         }
 198                         ++cursor->index;
 199                         continue;
 200                 }
 201
 202                 /*
 203                  * Check internal or leaf element.  Determine if the record
 204                  * at the cursor has gone beyond the end of our range.
 205                  *
 206                  * We recurse down through internal nodes.
 207                  */
 208                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 209                         elm = &node->elms[cursor->index];
 210
 211                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 212                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 213                         if (hammer_debug_btree) {
 214                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
 215                                         (long long)cursor->node->node_offset,
 216                                         cursor->index,
 217                                         (long long)elm[0].internal.base.obj_id,
 218                                         elm[0].internal.base.rec_type,
 219                                         (long long)elm[0].internal.base.key,
 220                                         elm[0].internal.base.localization,
 221                                         r,
 222                                         curthread
 223                                 );
 224                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 225                                         (long long)cursor->node->node_offset,
 226                                         cursor->index + 1,
 227                                         (long long)elm[1].internal.base.obj_id,
 228                                         elm[1].internal.base.rec_type,
 229                                         (long long)elm[1].internal.base.key,
 230                                         elm[1].internal.base.localization,
 231                                         s
 232                                 );
 233                         }
 234
 235                         if (r < 0) {
 236                                 error = ENOENT;
 237                                 break;
 238                         }
 239                         if (r == 0 && (cursor->flags &
 240                                        HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 241                                 error = ENOENT;
 242                                 break;
 243                         }
 244
 245                         /*
 246                          * Better not be zero
 247                          */
 248                         KKASSERT(elm->internal.subtree_offset != 0);
 249
 250                         if (s <= 0) {
 251                                 /*
 252                                  * If running the mirror filter see if we
 253                                  * can skip one or more entire sub-trees.
 254                                  * If we can we return the internal node
 255                                  * and the caller processes the skipped
 256                                  * range (see mirror_read).
 257                                  */
 258                                 if (cursor->flags &
 259                                     HAMMER_CURSOR_MIRROR_FILTERED) {
 260                                         if (elm->internal.mirror_tid <
 261                                             cursor->cmirror->mirror_tid) {
 262                                                 hammer_cursor_mirror_filter(cursor);
 263                                                 return(0);
 264                                         }
 265                                 }
 266                         } else {
 267                                 /*
 268                                  * Normally it would be impossible for the
 269                                  * cursor to have gotten back-indexed,
 270                                  * but it can happen if a node is deleted
 271                                  * and the cursor is moved to its parent
 272                                  * internal node.  ITERATE_CHECK will be set.
 273                                  */
 274                                 KKASSERT(cursor->flags &
 275                                          HAMMER_CURSOR_ITERATE_CHECK);
 276                                 kprintf("hammer_btree_iterate: "
 277                                         "DEBUG: Caught parent seek "
 278                                         "in internal iteration\n");
 279                         }
 280
 281                         error = hammer_cursor_down(cursor);
 282                         if (error)
 283                                 break;
 284                         KKASSERT(cursor->index == 0);
 285                         /* reload stale pointer */
 286                         node = cursor->node->ondisk;
 287                         continue;
 288                 } else {
 289                         elm = &node->elms[cursor->index];
 290                         r = hammer_btree_cmp(&cursor->key_end, &elm->base);
 291                         if (hammer_debug_btree) {
 292                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 293                                         (long long)cursor->node->node_offset,
 294                                         cursor->index,
 295                                         (elm[0].leaf.base.btype ?
 296                                          elm[0].leaf.base.btype : '?'),
 297                                         (long long)elm[0].leaf.base.obj_id,
 298                                         elm[0].leaf.base.rec_type,
 299                                         (long long)elm[0].leaf.base.key,
 300                                         elm[0].leaf.base.localization,
 301                                         r
 302                                 );
 303                         }
 304                         if (r < 0) {
 305                                 error = ENOENT;
 306                                 break;
 307                         }
 308
 309                         /*
 310                          * We support both end-inclusive and
 311                          * end-exclusive searches.
 312                          */
 313                         if (r == 0 &&
 314                            (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 315                                 error = ENOENT;
 316                                 break;
 317                         }
 318
 319                         /*
 320                          * If ITERATE_CHECK is set an unlocked cursor may
 321                          * have been moved to a parent and the iterate can
 322                          * happen upon elements that are not in the requested
 323                          * range.
 324                          */
 325                         if (cursor->flags & HAMMER_CURSOR_ITERATE_CHECK) {
 326                                 s = hammer_btree_cmp(&cursor->key_beg,
 327                                                      &elm->base);
 328                                 if (s > 0) {
 329                                         kprintf("hammer_btree_iterate: "
 330                                                 "DEBUG: Caught parent seek "
 331                                                 "in leaf iteration\n");
 332                                         ++cursor->index;
 333                                         continue;
 334                                 }
 335                         }
 336                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 337
 338                         /*
 339                          * Return the element
 340                          */
 341                         switch(elm->leaf.base.btype) {
 342                         case HAMMER_BTREE_TYPE_RECORD:
 343                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 344                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 345                                         ++cursor->index;
 346                                         continue;
 347                                 }
 348                                 error = 0;
 349                                 break;
 350                         default:
 351                                 error = EINVAL;
 352                                 break;
 353                         }
 354                         if (error)
 355                                 break;
 356                 }
 357                 /*
 358                  * node pointer invalid after loop
 359                  */
 360
 361                 /*
 362                  * Return entry
 363                  */
 364                 if (hammer_debug_btree) {
 365                         int i = cursor->index;
 366                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 367                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 368                                 cursor->node, i,
 369                                 (long long)elm->internal.base.obj_id,
 370                                 elm->internal.base.rec_type,
 371                                 (long long)elm->internal.base.key,
 372                                 elm->internal.base.localization
 373                         );
 374                 }
 375                 return(0);
 376         }
 377         return(error);
 378 }
 379
 380 /*
 381  * We hit an internal element that we could skip as part of a mirroring
 382  * scan.  Calculate the entire range being skipped.
 383  *
 384  * It is important to include any gaps between the parent's left_bound
 385  * and the node's left_bound, and same goes for the right side.
 386  */
 387 static void
 388 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
 389 {
 390         struct hammer_cmirror *cmirror;
 391         hammer_node_ondisk_t ondisk;
 392         hammer_btree_elm_t elm;
 393
 394         ondisk = cursor->node->ondisk;
 395         cmirror = cursor->cmirror;
 396
 397         /*
 398          * Calculate the skipped range
 399          */
 400         elm = &ondisk->elms[cursor->index];
 401         if (cursor->index == 0)
 402                 cmirror->skip_beg = *cursor->left_bound;
 403         else
 404                 cmirror->skip_beg = elm->internal.base;
 405         while (cursor->index < ondisk->count) {
 406                 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
 407                         break;
 408                 ++cursor->index;
 409                 ++elm;
 410         }
 411         if (cursor->index == ondisk->count)
 412                 cmirror->skip_end = *cursor->right_bound;
 413         else
 414                 cmirror->skip_end = elm->internal.base;
 415
 416         /*
 417          * clip the returned result.
 418          */
 419         if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
 420                 cmirror->skip_beg = cursor->key_beg;
 421         if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
 422                 cmirror->skip_end = cursor->key_end;
 423 }
 424
 425 /*
 426  * Iterate in the reverse direction.  This is used by the pruning code to
 427  * avoid overlapping records.
 428  */
 429 int
 430 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
 431 {
 432         hammer_node_ondisk_t node;
 433         hammer_btree_elm_t elm;
 434         hammer_mount_t hmp;
 435         int error = 0;
 436         int r;
 437         int s;
 438
 439         /* mirror filtering not supported for reverse iteration */
 440         KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
 441
 442         /*
 443          * Skip past the current record.  For various reasons the cursor
 444          * may end up set to -1 or set to point at the end of the current
 445          * node.  These cases must be addressed.
 446          */
 447         node = cursor->node->ondisk;
 448         if (node == NULL)
 449                 return(ENOENT);
 450         if (cursor->index != -1 &&
 451             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 452                 --cursor->index;
 453         }
 454         if (cursor->index == cursor->node->ondisk->count)
 455                 --cursor->index;
 456
 457         /*
 458          * HAMMER can wind up being cpu-bound.
 459          */
 460         hmp = cursor->trans->hmp;
 461         if (++hmp->check_yield > hammer_yield_check) {
 462                 hmp->check_yield = 0;
 463                 lwkt_user_yield();
 464         }
 465
 466         /*
 467          * Loop until an element is found or we are done.
 468          */
 469         for (;;) {
 470                 ++hammer_stats_btree_iterations;
 471                 hammer_flusher_clean_loose_ios(hmp);
 472
 473                 /*
 474                  * We iterate up the tree and then index over one element
 475                  * while we are at the last element in the current node.
 476                  */
 477                 if (cursor->index == -1) {
 478                         error = hammer_cursor_up(cursor);
 479                         if (error) {
 480                                 cursor->index = 0; /* sanity */
 481                                 break;
 482                         }
 483                         /* reload stale pointer */
 484                         node = cursor->node->ondisk;
 485                         KKASSERT(cursor->index != node->count);
 486                         --cursor->index;
 487                         continue;
 488                 }
 489
 490                 /*
 491                  * Check internal or leaf element.  Determine if the record
 492                  * at the cursor has gone beyond the end of our range.
 493                  *
 494                  * We recurse down through internal nodes.
 495                  */
 496                 KKASSERT(cursor->index != node->count);
 497                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 498                         elm = &node->elms[cursor->index];
 499                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 500                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 501                         if (hammer_debug_btree) {
 502                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 503                                         (long long)cursor->node->node_offset,
 504                                         cursor->index,
 505                                         (long long)elm[0].internal.base.obj_id,
 506                                         elm[0].internal.base.rec_type,
 507                                         (long long)elm[0].internal.base.key,
 508                                         elm[0].internal.base.localization,
 509                                         r
 510                                 );
 511                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 512                                         (long long)cursor->node->node_offset,
 513                                         cursor->index + 1,
 514                                         (long long)elm[1].internal.base.obj_id,
 515                                         elm[1].internal.base.rec_type,
 516                                         (long long)elm[1].internal.base.key,
 517                                         elm[1].internal.base.localization,
 518                                         s
 519                                 );
 520                         }
 521
 522                         if (s >= 0) {
 523                                 error = ENOENT;
 524                                 break;
 525                         }
 526
 527                         /*
 528                          * It shouldn't be possible to be seeked past key_end,
 529                          * even if the cursor got moved to a parent.
 530                          */
 531                         KKASSERT(r >= 0);
 532
 533                         /*
 534                          * Better not be zero
 535                          */
 536                         KKASSERT(elm->internal.subtree_offset != 0);
 537
 538                         error = hammer_cursor_down(cursor);
 539                         if (error)
 540                                 break;
 541                         KKASSERT(cursor->index == 0);
 542                         /* reload stale pointer */
 543                         node = cursor->node->ondisk;
 544
 545                         /* this can assign -1 if the leaf was empty */
 546                         cursor->index = node->count - 1;
 547                         continue;
 548                 } else {
 549                         elm = &node->elms[cursor->index];
 550                         s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
 551                         if (hammer_debug_btree) {
 552                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 553                                         (long long)cursor->node->node_offset,
 554                                         cursor->index,
 555                                         (elm[0].leaf.base.btype ?
 556                                          elm[0].leaf.base.btype : '?'),
 557                                         (long long)elm[0].leaf.base.obj_id,
 558                                         elm[0].leaf.base.rec_type,
 559                                         (long long)elm[0].leaf.base.key,
 560                                         elm[0].leaf.base.localization,
 561                                         s
 562                                 );
 563                         }
 564                         if (s > 0) {
 565                                 error = ENOENT;
 566                                 break;
 567                         }
 568
 569                         /*
 570                          * It shouldn't be possible to be seeked past key_end,
 571                          * even if the cursor got moved to a parent.
 572                          */
 573                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 574
 575                         /*
 576                          * Return the element
 577                          */
 578                         switch(elm->leaf.base.btype) {
 579                         case HAMMER_BTREE_TYPE_RECORD:
 580                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 581                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 582                                         --cursor->index;
 583                                         continue;
 584                                 }
 585                                 error = 0;
 586                                 break;
 587                         default:
 588                                 error = EINVAL;
 589                                 break;
 590                         }
 591                         if (error)
 592                                 break;
 593                 }
 594                 /*
 595                  * node pointer invalid after loop
 596                  */
 597
 598                 /*
 599                  * Return entry
 600                  */
 601                 if (hammer_debug_btree) {
 602                         int i = cursor->index;
 603                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 604                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 605                                 cursor->node, i,
 606                                 (long long)elm->internal.base.obj_id,
 607                                 elm->internal.base.rec_type,
 608                                 (long long)elm->internal.base.key,
 609                                 elm->internal.base.localization
 610                         );
 611                 }
 612                 return(0);
 613         }
 614         return(error);
 615 }
 616
 617 /*
 618  * Lookup cursor->key_beg.  0 is returned on success, ENOENT if the entry
 619  * could not be found, EDEADLK if inserting and a retry is needed, and a
 620  * fatal error otherwise.  When retrying, the caller must terminate the
 621  * cursor and reinitialize it.  EDEADLK cannot be returned if not inserting.
 622  *
 623  * The cursor is suitably positioned for a deletion on success, and suitably
 624  * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
 625  * specified.
 626  *
 627  * The cursor may begin anywhere, the search will traverse the tree in
 628  * either direction to locate the requested element.
 629  *
 630  * Most of the logic implementing historical searches is handled here.  We
 631  * do an initial lookup with create_tid set to the asof TID.  Due to the
 632  * way records are laid out, a backwards iteration may be required if
 633  * ENOENT is returned to locate the historical record.  Here's the
 634  * problem:
 635  *
 636  * create_tid:    10      15       20
 637  *                   LEAF1   LEAF2
 638  * records:         (11)        (18)
 639  *
 640  * Lets say we want to do a lookup AS-OF timestamp 17.  We will traverse
 641  * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
 642  * not visible and thus causes ENOENT to be returned.  We really need
 643  * to check record 11 in LEAF1.  If it also fails then the search fails
 644  * (e.g. it might represent the range 11-16 and thus still not match our
 645  * AS-OF timestamp of 17).  Note that LEAF1 could be empty, requiring
 646  * further iterations.
 647  *
 648  * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
 649  * and the cursor->create_check TID if an iteration might be needed.
 650  * In the above example create_check would be set to 14.
 651  */
 652 int
 653 hammer_btree_lookup(hammer_cursor_t cursor)
 654 {
 655         int error;
 656
 657         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 658         KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
 659                   cursor->trans->sync_lock_refs > 0);
 660         ++hammer_stats_btree_lookups;
 661         if (cursor->flags & HAMMER_CURSOR_ASOF) {
 662                 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
 663                 cursor->key_beg.create_tid = cursor->asof;
 664                 for (;;) {
 665                         cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
 666                         error = btree_search(cursor, 0);
 667                         if (error != ENOENT ||
 668                             (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
 669                                 /*
 670                                  * Stop if no error.
 671                                  * Stop if error other then ENOENT.
 672                                  * Stop if ENOENT and not special case.
 673                                  */
 674                                 break;
 675                         }
 676                         if (hammer_debug_btree) {
 677                                 kprintf("CREATE_CHECK %016llx\n",
 678                                         (long long)cursor->create_check);
 679                         }
 680                         cursor->key_beg.create_tid = cursor->create_check;
 681                         /* loop */
 682                 }
 683         } else {
 684                 error = btree_search(cursor, 0);
 685         }
 686         if (error == 0)
 687                 error = hammer_btree_extract(cursor, cursor->flags);
 688         return(error);
 689 }
 690
 691 /*
 692  * Execute the logic required to start an iteration.  The first record
 693  * located within the specified range is returned and iteration control
 694  * flags are adjusted for successive hammer_btree_iterate() calls.
 695  *
 696  * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
 697  * in a loop without worrying about it.  Higher-level merged searches will
 698  * adjust the flag appropriately.
 699  */
 700 int
 701 hammer_btree_first(hammer_cursor_t cursor)
 702 {
 703         int error;
 704
 705         error = hammer_btree_lookup(cursor);
 706         if (error == ENOENT) {
 707                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 708                 error = hammer_btree_iterate(cursor);
 709         }
 710         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 711         return(error);
 712 }
 713
 714 /*
 715  * Similarly but for an iteration in the reverse direction.
 716  *
 717  * Set ATEDISK when iterating backwards to skip the current entry,
 718  * which after an ENOENT lookup will be pointing beyond our end point.
 719  *
 720  * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
 721  * in a loop without worrying about it.  Higher-level merged searches will
 722  * adjust the flag appropriately.
 723  */
 724 int
 725 hammer_btree_last(hammer_cursor_t cursor)
 726 {
 727         struct hammer_base_elm save;
 728         int error;
 729
 730         save = cursor->key_beg;
 731         cursor->key_beg = cursor->key_end;
 732         error = hammer_btree_lookup(cursor);
 733         cursor->key_beg = save;
 734         if (error == ENOENT ||
 735             (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 736                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 737                 error = hammer_btree_iterate_reverse(cursor);
 738         }
 739         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 740         return(error);
 741 }
 742
 743 /*
 744  * Extract the record and/or data associated with the cursor's current
 745  * position.  Any prior record or data stored in the cursor is replaced.
 746  * The cursor must be positioned at a leaf node.
 747  *
 748  * NOTE: All extractions occur at the leaf of the B-Tree.
 749  */
 750 int
 751 hammer_btree_extract(hammer_cursor_t cursor, int flags)
 752 {
 753         hammer_node_ondisk_t node;
 754         hammer_btree_elm_t elm;
 755         hammer_off_t data_off;
 756         hammer_mount_t hmp;
 757         int32_t data_len;
 758         int error;
 759
 760         /*
 761          * The case where the data reference resolves to the same buffer
 762          * as the record reference must be handled.
 763          */
 764         node = cursor->node->ondisk;
 765         elm = &node->elms[cursor->index];
 766         cursor->data = NULL;
 767         hmp = cursor->node->hmp;
 768
 769         /*
 770          * There is nothing to extract for an internal element.
 771          */
 772         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 773                 return(EINVAL);
 774
 775         /*
 776          * Only record types have data.
 777          */
 778         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 779         cursor->leaf = &elm->leaf;
 780
 781         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 782                 return(0);
 783         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 784                 return(0);
 785         data_off = elm->leaf.data_offset;
 786         data_len = elm->leaf.data_len;
 787         if (data_off == 0)
 788                 return(0);
 789
 790         /*
 791          * Load the data
 792          */
 793         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 794         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 795                                         &error, &cursor->data_buffer);
 796
 797         /*
 798          * Mark the data buffer as not being meta-data if it isn't
 799          * meta-data (sometimes bulk data is accessed via a volume
 800          * block device).
 801          */
 802         if (error == 0) {
 803                 switch(elm->leaf.base.rec_type) {
 804                 case HAMMER_RECTYPE_DATA:
 805                 case HAMMER_RECTYPE_DB:
 806                         if ((data_off & HAMMER_ZONE_LARGE_DATA) == 0)
 807                                 break;
 808                         if (hammer_double_buffer == 0 ||
 809                             (cursor->flags & HAMMER_CURSOR_NOSWAPCACHE)) {
 810                                 hammer_io_notmeta(cursor->data_buffer);
 811                         }
 812                         break;
 813                 default:
 814                         break;
 815                 }
 816         }
 817
 818         /*
 819          * Deal with CRC errors on the extracted data.
 820          */
 821         if (error == 0 &&
 822             hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 823                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 824                         (long long)elm->leaf.data_offset, elm->leaf.data_len);
 825                 if (hammer_debug_critical)
 826                         Debugger("CRC FAILED: DATA");
 827                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 828                         error = EDOM;   /* less critical (mirroring) */
 829                 else
 830                         error = EIO;    /* critical */
 831         }
 832         return(error);
 833 }
 834
 835
 836 /*
 837  * Insert a leaf element into the B-Tree at the current cursor position.
 838  * The cursor is positioned such that the element at and beyond the cursor
 839  * are shifted to make room for the new record.
 840  *
 841  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 842  * flag set and that call must return ENOENT before this function can be
 843  * called.
 844  *
 845  * The caller may depend on the cursor's exclusive lock after return to
 846  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 847  *
 848  * ENOSPC is returned if there is no room to insert a new record.
 849  */
 850 int
 851 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 852                     int *doprop)
 853 {
 854         hammer_node_ondisk_t node;
 855         int i;
 856         int error;
 857
 858         *doprop = 0;
 859         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 860                 return(error);
 861         ++hammer_stats_btree_inserts;
 862
 863         /*
 864          * Insert the element at the leaf node and update the count in the
 865          * parent.  It is possible for parent to be NULL, indicating that
 866          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 867          * possible.  The root inode can never be deleted so the leaf should
 868          * never be empty.
 869          *
 870          * Remember that the right-hand boundary is not included in the
 871          * count.
 872          */
 873         hammer_modify_node_all(cursor->trans, cursor->node);
 874         node = cursor->node->ondisk;
 875         i = cursor->index;
 876         KKASSERT(elm->base.btype != 0);
 877         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 878         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 879         if (i != node->count) {
 880                 bcopy(&node->elms[i], &node->elms[i+1],
 881                       (node->count - i) * sizeof(*elm));
 882         }
 883         node->elms[i].leaf = *elm;
 884         ++node->count;
 885         hammer_cursor_inserted_element(cursor->node, i);
 886
 887         /*
 888          * Update the leaf node's aggregate mirror_tid for mirroring
 889          * support.
 890          */
 891         if (node->mirror_tid < elm->base.delete_tid) {
 892                 node->mirror_tid = elm->base.delete_tid;
 893                 *doprop = 1;
 894         }
 895         if (node->mirror_tid < elm->base.create_tid) {
 896                 node->mirror_tid = elm->base.create_tid;
 897                 *doprop = 1;
 898         }
 899         hammer_modify_node_done(cursor->node);
 900
 901         /*
 902          * Debugging sanity checks.
 903          */
 904         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 905         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 906         if (i) {
 907                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 908         }
 909         if (i != node->count - 1)
 910                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 911
 912         return(0);
 913 }
 914
 915 /*
 916  * Delete a record from the B-Tree at the current cursor position.
 917  * The cursor is positioned such that the current element is the one
 918  * to be deleted.
 919  *
 920  * On return the cursor will be positioned after the deleted element and
 921  * MAY point to an internal node.  It will be suitable for the continuation
 922  * of an iteration but not for an insertion or deletion.
 923  *
 924  * Deletions will attempt to partially rebalance the B-Tree in an upward
 925  * direction, but will terminate rather then deadlock.  Empty internal nodes
 926  * are never allowed by a deletion which deadlocks may end up giving us an
 927  * empty leaf.  The pruner will clean up and rebalance the tree.
 928  *
 929  * This function can return EDEADLK, requiring the caller to retry the
 930  * operation after clearing the deadlock.
 931  */
 932 int
 933 hammer_btree_delete(hammer_cursor_t cursor)
 934 {
 935         hammer_node_ondisk_t ondisk;
 936         hammer_node_t node;
 937         hammer_node_t parent __debugvar;
 938         int error;
 939         int i;
 940
 941         KKASSERT (cursor->trans->sync_lock_refs > 0);
 942         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 943                 return(error);
 944         ++hammer_stats_btree_deletes;
 945
 946         /*
 947          * Delete the element from the leaf node.
 948          *
 949          * Remember that leaf nodes do not have boundaries.
 950          */
 951         node = cursor->node;
 952         ondisk = node->ondisk;
 953         i = cursor->index;
 954
 955         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 956         KKASSERT(i >= 0 && i < ondisk->count);
 957         hammer_modify_node_all(cursor->trans, node);
 958         if (i + 1 != ondisk->count) {
 959                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 960                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 961         }
 962         --ondisk->count;
 963         hammer_modify_node_done(node);
 964         hammer_cursor_deleted_element(node, i);
 965
 966         /*
 967          * Validate local parent
 968          */
 969         if (ondisk->parent) {
 970                 parent = cursor->parent;
 971
 972                 KKASSERT(parent != NULL);
 973                 KKASSERT(parent->node_offset == ondisk->parent);
 974         }
 975
 976         /*
 977          * If the leaf becomes empty it must be detached from the parent,
 978          * potentially recursing through to the filesystem root.
 979          *
 980          * This may reposition the cursor at one of the parent's of the
 981          * current node.
 982          *
 983          * Ignore deadlock errors, that simply means that btree_remove
 984          * was unable to recurse and had to leave us with an empty leaf.
 985          */
 986         KKASSERT(cursor->index <= ondisk->count);
 987         if (ondisk->count == 0) {
 988                 error = btree_remove(cursor);
 989                 if (error == EDEADLK)
 990                         error = 0;
 991         } else {
 992                 error = 0;
 993         }
 994         KKASSERT(cursor->parent == NULL ||
 995                  cursor->parent_index < cursor->parent->ondisk->count);
 996         return(error);
 997 }
 998
 999 /*
1000  * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
1001  *
1002  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
1003  *
1004  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
1005  * iterates up the tree as necessary to properly position itself prior to
1006  * actually doing the sarch.
1007  *
1008  * INSERTIONS: The search will split full nodes and leaves on its way down
1009  * and guarentee that the leaf it ends up on is not full.  If we run out
1010  * of space the search continues to the leaf, but ENOSPC is returned.
1011  *
1012  * The search is only guarenteed to end up on a leaf if an error code of 0
1013  * is returned, or if inserting and an error code of ENOENT is returned.
1014  * Otherwise it can stop at an internal node.  On success a search returns
1015  * a leaf node.
1016  *
1017  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
1018  * filesystem, and it is not simple code.  Please note the following facts:
1019  *
1020  * - Internal node recursions have a boundary on the left AND right.  The
1021  *   right boundary is non-inclusive.  The create_tid is a generic part
1022  *   of the key for internal nodes.
1023  *
1024  * - Leaf nodes contain terminal elements only now.
1025  *
1026  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
1027  *   historical search.  ASOF and INSERT are mutually exclusive.  When
1028  *   doing an as-of lookup btree_search() checks for a right-edge boundary
1029  *   case.  If while recursing down the left-edge differs from the key
1030  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
1031  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
1032  *   The iteration backwards because as-of searches can wind up going
1033  *   down the wrong branch of the B-Tree.
1034  */
1035 static
1036 int
1037 btree_search(hammer_cursor_t cursor, int flags)
1038 {
1039         hammer_node_ondisk_t node;
1040         hammer_btree_elm_t elm;
1041         int error;
1042         int enospc = 0;
1043         int i;
1044         int r;
1045         int s;
1046
1047         flags |= cursor->flags;
1048         ++hammer_stats_btree_searches;
1049
1050         if (hammer_debug_btree) {
1051                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
1052                         (long long)cursor->node->node_offset,
1053                         cursor->index,
1054                         (long long)cursor->key_beg.obj_id,
1055                         cursor->key_beg.rec_type,
1056                         (long long)cursor->key_beg.key,
1057                         (long long)cursor->key_beg.create_tid,
1058                         cursor->key_beg.localization,
1059                         curthread
1060                 );
1061                 if (cursor->parent)
1062                     kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
1063                         (long long)cursor->parent->node_offset,
1064                         cursor->parent_index,
1065                         (long long)cursor->left_bound->obj_id,
1066                         (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
1067                         (long long)cursor->right_bound->obj_id,
1068                         (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
1069                         cursor->left_bound,
1070                         &cursor->parent->ondisk->elms[cursor->parent_index],
1071                         cursor->right_bound,
1072                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
1073                     );
1074         }
1075
1076         /*
1077          * Move our cursor up the tree until we find a node whos range covers
1078          * the key we are trying to locate.
1079          *
1080          * The left bound is inclusive, the right bound is non-inclusive.
1081          * It is ok to cursor up too far.
1082          */
1083         for (;;) {
1084                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
1085                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
1086                 if (r >= 0 && s < 0)
1087                         break;
1088                 KKASSERT(cursor->parent);
1089                 ++hammer_stats_btree_iterations;
1090                 error = hammer_cursor_up(cursor);
1091                 if (error)
1092                         goto done;
1093         }
1094
1095         /*
1096          * The delete-checks below are based on node, not parent.  Set the
1097          * initial delete-check based on the parent.
1098          */
1099         if (r == 1) {
1100                 KKASSERT(cursor->left_bound->create_tid != 1);
1101                 cursor->create_check = cursor->left_bound->create_tid - 1;
1102                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1103         }
1104
1105         /*
1106          * We better have ended up with a node somewhere.
1107          */
1108         KKASSERT(cursor->node != NULL);
1109
1110         /*
1111          * If we are inserting we can't start at a full node if the parent
1112          * is also full (because there is no way to split the node),
1113          * continue running up the tree until the requirement is satisfied
1114          * or we hit the root of the filesystem.
1115          *
1116          * (If inserting we aren't doing an as-of search so we don't have
1117          *  to worry about create_check).
1118          */
1119         while (flags & HAMMER_CURSOR_INSERT) {
1120                 if (btree_node_is_full(cursor->node->ondisk) == 0)
1121                         break;
1122                 if (cursor->node->ondisk->parent == 0 ||
1123                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1124                         break;
1125                 }
1126                 ++hammer_stats_btree_iterations;
1127                 error = hammer_cursor_up(cursor);
1128                 /* node may have become stale */
1129                 if (error)
1130                         goto done;
1131         }
1132
1133         /*
1134          * Push down through internal nodes to locate the requested key.
1135          */
1136         node = cursor->node->ondisk;
1137         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1138                 /*
1139                  * Scan the node to find the subtree index to push down into.
1140                  * We go one-past, then back-up.
1141                  *
1142                  * We must proactively remove deleted elements which may
1143                  * have been left over from a deadlocked btree_remove().
1144                  *
1145                  * The left and right boundaries are included in the loop
1146                  * in order to detect edge cases.
1147                  *
1148                  * If the separator only differs by create_tid (r == 1)
1149                  * and we are doing an as-of search, we may end up going
1150                  * down a branch to the left of the one containing the
1151                  * desired key.  This requires numerous special cases.
1152                  */
1153                 ++hammer_stats_btree_iterations;
1154                 if (hammer_debug_btree) {
1155                         kprintf("SEARCH-I %016llx count=%d\n",
1156                                 (long long)cursor->node->node_offset,
1157                                 node->count);
1158                 }
1159
1160                 /*
1161                  * Try to shortcut the search before dropping into the
1162                  * linear loop.  Locate the first node where r <= 1.
1163                  */
1164                 i = hammer_btree_search_node(&cursor->key_beg, node);
1165                 while (i <= node->count) {
1166                         ++hammer_stats_btree_elements;
1167                         elm = &node->elms[i];
1168                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1169                         if (hammer_debug_btree > 2) {
1170                                 kprintf(" IELM %p %d r=%d\n",
1171                                         &node->elms[i], i, r);
1172                         }
1173                         if (r < 0)
1174                                 break;
1175                         if (r == 1) {
1176                                 KKASSERT(elm->base.create_tid != 1);
1177                                 cursor->create_check = elm->base.create_tid - 1;
1178                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1179                         }
1180                         ++i;
1181                 }
1182                 if (hammer_debug_btree) {
1183                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1184                                 i, node->count, r);
1185                 }
1186
1187                 /*
1188                  * These cases occur when the parent's idea of the boundary
1189                  * is wider then the child's idea of the boundary, and
1190                  * require special handling.  If not inserting we can
1191                  * terminate the search early for these cases but the
1192                  * child's boundaries cannot be unconditionally modified.
1193                  */
1194                 if (i == 0) {
1195                         /*
1196                          * If i == 0 the search terminated to the LEFT of the
1197                          * left_boundary but to the RIGHT of the parent's left
1198                          * boundary.
1199                          */
1200                         u_int8_t save;
1201
1202                         elm = &node->elms[0];
1203
1204                         /*
1205                          * If we aren't inserting we can stop here.
1206                          */
1207                         if ((flags & (HAMMER_CURSOR_INSERT |
1208                                       HAMMER_CURSOR_PRUNING)) == 0) {
1209                                 cursor->index = 0;
1210                                 return(ENOENT);
1211                         }
1212
1213                         /*
1214                          * Correct a left-hand boundary mismatch.
1215                          *
1216                          * We can only do this if we can upgrade the lock,
1217                          * and synchronized as a background cursor (i.e.
1218                          * inserting or pruning).
1219                          *
1220                          * WARNING: We can only do this if inserting, i.e.
1221                          * we are running on the backend.
1222                          */
1223                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1224                                 return(error);
1225                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1226                         hammer_modify_node_field(cursor->trans, cursor->node,
1227                                                  elms[0]);
1228                         save = node->elms[0].base.btype;
1229                         node->elms[0].base = *cursor->left_bound;
1230                         node->elms[0].base.btype = save;
1231                         hammer_modify_node_done(cursor->node);
1232                 } else if (i == node->count + 1) {
1233                         /*
1234                          * If i == node->count + 1 the search terminated to
1235                          * the RIGHT of the right boundary but to the LEFT
1236                          * of the parent's right boundary.  If we aren't
1237                          * inserting we can stop here.
1238                          *
1239                          * Note that the last element in this case is
1240                          * elms[i-2] prior to adjustments to 'i'.
1241                          */
1242                         --i;
1243                         if ((flags & (HAMMER_CURSOR_INSERT |
1244                                       HAMMER_CURSOR_PRUNING)) == 0) {
1245                                 cursor->index = i;
1246                                 return (ENOENT);
1247                         }
1248
1249                         /*
1250                          * Correct a right-hand boundary mismatch.
1251                          * (actual push-down record is i-2 prior to
1252                          * adjustments to i).
1253                          *
1254                          * We can only do this if we can upgrade the lock,
1255                          * and synchronized as a background cursor (i.e.
1256                          * inserting or pruning).
1257                          *
1258                          * WARNING: We can only do this if inserting, i.e.
1259                          * we are running on the backend.
1260                          */
1261                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1262                                 return(error);
1263                         elm = &node->elms[i];
1264                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1265                         hammer_modify_node(cursor->trans, cursor->node,
1266                                            &elm->base, sizeof(elm->base));
1267                         elm->base = *cursor->right_bound;
1268                         hammer_modify_node_done(cursor->node);
1269                         --i;
1270                 } else {
1271                         /*
1272                          * The push-down index is now i - 1.  If we had
1273                          * terminated on the right boundary this will point
1274                          * us at the last element.
1275                          */
1276                         --i;
1277                 }
1278                 cursor->index = i;
1279                 elm = &node->elms[i];
1280
1281                 if (hammer_debug_btree) {
1282                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1283                                 "key=%016llx cre=%016llx lo=%02x\n",
1284                                 (long long)cursor->node->node_offset,
1285                                 i,
1286                                 (long long)elm->internal.base.obj_id,
1287                                 elm->internal.base.rec_type,
1288                                 (long long)elm->internal.base.key,
1289                                 (long long)elm->internal.base.create_tid,
1290                                 elm->internal.base.localization
1291                         );
1292                 }
1293
1294                 /*
1295                  * We better have a valid subtree offset.
1296                  */
1297                 KKASSERT(elm->internal.subtree_offset != 0);
1298
1299                 /*
1300                  * Handle insertion and deletion requirements.
1301                  *
1302                  * If inserting split full nodes.  The split code will
1303                  * adjust cursor->node and cursor->index if the current
1304                  * index winds up in the new node.
1305                  *
1306                  * If inserting and a left or right edge case was detected,
1307                  * we cannot correct the left or right boundary and must
1308                  * prepend and append an empty leaf node in order to make
1309                  * the boundary correction.
1310                  *
1311                  * If we run out of space we set enospc but continue on
1312                  * to a leaf.
1313                  */
1314                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1315                         if (btree_node_is_full(node)) {
1316                                 error = btree_split_internal(cursor);
1317                                 if (error) {
1318                                         if (error != ENOSPC)
1319                                                 goto done;
1320                                         enospc = 1;
1321                                 }
1322                                 /*
1323                                  * reload stale pointers
1324                                  */
1325                                 i = cursor->index;
1326                                 node = cursor->node->ondisk;
1327                         }
1328                 }
1329
1330                 /*
1331                  * Push down (push into new node, existing node becomes
1332                  * the parent) and continue the search.
1333                  */
1334                 error = hammer_cursor_down(cursor);
1335                 /* node may have become stale */
1336                 if (error)
1337                         goto done;
1338                 node = cursor->node->ondisk;
1339         }
1340
1341         /*
1342          * We are at a leaf, do a linear search of the key array.
1343          *
1344          * On success the index is set to the matching element and 0
1345          * is returned.
1346          *
1347          * On failure the index is set to the insertion point and ENOENT
1348          * is returned.
1349          *
1350          * Boundaries are not stored in leaf nodes, so the index can wind
1351          * up to the left of element 0 (index == 0) or past the end of
1352          * the array (index == node->count).  It is also possible that the
1353          * leaf might be empty.
1354          */
1355         ++hammer_stats_btree_iterations;
1356         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1357         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1358         if (hammer_debug_btree) {
1359                 kprintf("SEARCH-L %016llx count=%d\n",
1360                         (long long)cursor->node->node_offset,
1361                         node->count);
1362         }
1363
1364         /*
1365          * Try to shortcut the search before dropping into the
1366          * linear loop.  Locate the first node where r <= 1.
1367          */
1368         i = hammer_btree_search_node(&cursor->key_beg, node);
1369         while (i < node->count) {
1370                 ++hammer_stats_btree_elements;
1371                 elm = &node->elms[i];
1372
1373                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1374
1375                 if (hammer_debug_btree > 1)
1376                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1377
1378                 /*
1379                  * We are at a record element.  Stop if we've flipped past
1380                  * key_beg, not counting the create_tid test.  Allow the
1381                  * r == 1 case (key_beg > element but differs only by its
1382                  * create_tid) to fall through to the AS-OF check.
1383                  */
1384                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1385
1386                 if (r < 0)
1387                         goto failed;
1388                 if (r > 1) {
1389                         ++i;
1390                         continue;
1391                 }
1392
1393                 /*
1394                  * Check our as-of timestamp against the element.
1395                  */
1396                 if (flags & HAMMER_CURSOR_ASOF) {
1397                         if (hammer_btree_chkts(cursor->asof,
1398                                                &node->elms[i].base) != 0) {
1399                                 ++i;
1400                                 continue;
1401                         }
1402                         /* success */
1403                 } else {
1404                         if (r > 0) {    /* can only be +1 */
1405                                 ++i;
1406                                 continue;
1407                         }
1408                         /* success */
1409                 }
1410                 cursor->index = i;
1411                 error = 0;
1412                 if (hammer_debug_btree) {
1413                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1414                                 (long long)cursor->node->node_offset, i);
1415                 }
1416                 goto done;
1417         }
1418
1419         /*
1420          * The search of the leaf node failed.  i is the insertion point.
1421          */
1422 failed:
1423         if (hammer_debug_btree) {
1424                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1425                         (long long)cursor->node->node_offset, i);
1426         }
1427
1428         /*
1429          * No exact match was found, i is now at the insertion point.
1430          *
1431          * If inserting split a full leaf before returning.  This
1432          * may have the side effect of adjusting cursor->node and
1433          * cursor->index.
1434          */
1435         cursor->index = i;
1436         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1437              btree_node_is_full(node)) {
1438                 error = btree_split_leaf(cursor);
1439                 if (error) {
1440                         if (error != ENOSPC)
1441                                 goto done;
1442                         enospc = 1;
1443                 }
1444                 /*
1445                  * reload stale pointers
1446                  */
1447                 /* NOT USED
1448                 i = cursor->index;
1449                 node = &cursor->node->internal;
1450                 */
1451         }
1452
1453         /*
1454          * We reached a leaf but did not find the key we were looking for.
1455          * If this is an insert we will be properly positioned for an insert
1456          * (ENOENT) or unable to insert (ENOSPC).
1457          */
1458         error = enospc ? ENOSPC : ENOENT;
1459 done:
1460         return(error);
1461 }
1462
1463 /*
1464  * Heuristical search for the first element whos comparison is <= 1.  May
1465  * return an index whos compare result is > 1 but may only return an index
1466  * whos compare result is <= 1 if it is the first element with that result.
1467  */
1468 int
1469 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1470 {
1471         int b;
1472         int s;
1473         int i;
1474         int r;
1475
1476         /*
1477          * Don't bother if the node does not have very many elements
1478          */
1479         b = 0;
1480         s = node->count;
1481         while (s - b > 4) {
1482                 i = b + (s - b) / 2;
1483                 ++hammer_stats_btree_elements;
1484                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1485                 if (r <= 1) {
1486                         s = i;
1487                 } else {
1488                         b = i;
1489                 }
1490         }
1491         return(b);
1492 }
1493
1494
1495 /************************************************************************
1496  *                         SPLITTING AND MERGING                        *
1497  ************************************************************************
1498  *
1499  * These routines do all the dirty work required to split and merge nodes.
1500  */
1501
1502 /*
1503  * Split an internal node into two nodes and move the separator at the split
1504  * point to the parent.
1505  *
1506  * (cursor->node, cursor->index) indicates the element the caller intends
1507  * to push into.  We will adjust node and index if that element winds
1508  * up in the split node.
1509  *
1510  * If we are at the root of the filesystem a new root must be created with
1511  * two elements, one pointing to the original root and one pointing to the
1512  * newly allocated split node.
1513  */
1514 static
1515 int
1516 btree_split_internal(hammer_cursor_t cursor)
1517 {
1518         hammer_node_ondisk_t ondisk;
1519         hammer_node_t node;
1520         hammer_node_t parent;
1521         hammer_node_t new_node;
1522         hammer_btree_elm_t elm;
1523         hammer_btree_elm_t parent_elm;
1524         struct hammer_node_lock lockroot;
1525         hammer_mount_t hmp = cursor->trans->hmp;
1526         int parent_index;
1527         int made_root;
1528         int split;
1529         int error;
1530         int i;
1531         const int esize = sizeof(*elm);
1532
1533         hammer_node_lock_init(&lockroot, cursor->node);
1534         error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
1535         if (error)
1536                 goto done;
1537         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1538                 goto done;
1539         ++hammer_stats_btree_splits;
1540
1541         /*
1542          * Calculate the split point.  If the insertion point is at the
1543          * end of the leaf we adjust the split point significantly to the
1544          * right to try to optimize node fill and flag it.  If we hit
1545          * that same leaf again our heuristic failed and we don't try
1546          * to optimize node fill (it could lead to a degenerate case).
1547          */
1548         node = cursor->node;
1549         ondisk = node->ondisk;
1550         KKASSERT(ondisk->count > 4);
1551         if (cursor->index == ondisk->count &&
1552             (node->flags & HAMMER_NODE_NONLINEAR) == 0) {
1553                 split = (ondisk->count + 1) * 3 / 4;
1554                 node->flags |= HAMMER_NODE_NONLINEAR;
1555         } else {
1556                 /*
1557                  * We are splitting but elms[split] will be promoted to
1558                  * the parent, leaving the right hand node with one less
1559                  * element.  If the insertion point will be on the
1560                  * left-hand side adjust the split point to give the
1561                  * right hand side one additional node.
1562                  */
1563                 split = (ondisk->count + 1) / 2;
1564                 if (cursor->index <= split)
1565                         --split;
1566         }
1567
1568         /*
1569          * If we are at the root of the filesystem, create a new root node
1570          * with 1 element and split normally.  Avoid making major
1571          * modifications until we know the whole operation will work.
1572          */
1573         if (ondisk->parent == 0) {
1574                 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1575                 if (parent == NULL)
1576                         goto done;
1577                 hammer_lock_ex(&parent->lock);
1578                 hammer_modify_node_noundo(cursor->trans, parent);
1579                 ondisk = parent->ondisk;
1580                 ondisk->count = 1;
1581                 ondisk->parent = 0;
1582                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1583                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1584                 ondisk->elms[0].base = hmp->root_btree_beg;
1585                 ondisk->elms[0].base.btype = node->ondisk->type;
1586                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1587                 ondisk->elms[1].base = hmp->root_btree_end;
1588                 hammer_modify_node_done(parent);
1589                 /* ondisk->elms[1].base.btype - not used */
1590                 made_root = 1;
1591                 parent_index = 0;       /* index of current node in parent */
1592         } else {
1593                 made_root = 0;
1594                 parent = cursor->parent;
1595                 parent_index = cursor->parent_index;
1596         }
1597
1598         /*
1599          * Split node into new_node at the split point.
1600          *
1601          *  B O O O P N N B     <-- P = node->elms[split] (index 4)
1602          *   0 1 2 3 4 5 6      <-- subtree indices
1603          *
1604          *       x x P x x
1605          *        s S S s
1606          *         /   \
1607          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1608          *   0 1 2 3      4 5 6
1609          */
1610         new_node = hammer_alloc_btree(cursor->trans, 0, &error);
1611         if (new_node == NULL) {
1612                 if (made_root) {
1613                         hammer_unlock(&parent->lock);
1614                         hammer_delete_node(cursor->trans, parent);
1615                         hammer_rel_node(parent);
1616                 }
1617                 goto done;
1618         }
1619         hammer_lock_ex(&new_node->lock);
1620
1621         /*
1622          * Create the new node.  P becomes the left-hand boundary in the
1623          * new node.  Copy the right-hand boundary as well.
1624          *
1625          * elm is the new separator.
1626          */
1627         hammer_modify_node_noundo(cursor->trans, new_node);
1628         hammer_modify_node_all(cursor->trans, node);
1629         ondisk = node->ondisk;
1630         elm = &ondisk->elms[split];
1631         bcopy(elm, &new_node->ondisk->elms[0],
1632               (ondisk->count - split + 1) * esize);
1633         new_node->ondisk->count = ondisk->count - split;
1634         new_node->ondisk->parent = parent->node_offset;
1635         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1636         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1637         KKASSERT(ondisk->type == new_node->ondisk->type);
1638         hammer_cursor_split_node(node, new_node, split);
1639
1640         /*
1641          * Cleanup the original node.  Elm (P) becomes the new boundary,
1642          * its subtree_offset was moved to the new node.  If we had created
1643          * a new root its parent pointer may have changed.
1644          */
1645         elm->internal.subtree_offset = 0;
1646         ondisk->count = split;
1647
1648         /*
1649          * Insert the separator into the parent, fixup the parent's
1650          * reference to the original node, and reference the new node.
1651          * The separator is P.
1652          *
1653          * Remember that base.count does not include the right-hand boundary.
1654          */
1655         hammer_modify_node_all(cursor->trans, parent);
1656         ondisk = parent->ondisk;
1657         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1658         parent_elm = &ondisk->elms[parent_index+1];
1659         bcopy(parent_elm, parent_elm + 1,
1660               (ondisk->count - parent_index) * esize);
1661         parent_elm->internal.base = elm->base;  /* separator P */
1662         parent_elm->internal.base.btype = new_node->ondisk->type;
1663         parent_elm->internal.subtree_offset = new_node->node_offset;
1664         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1665         ++ondisk->count;
1666         hammer_modify_node_done(parent);
1667         hammer_cursor_inserted_element(parent, parent_index + 1);
1668
1669         /*
1670          * The children of new_node need their parent pointer set to new_node.
1671          * The children have already been locked by
1672          * hammer_btree_lock_children().
1673          */
1674         for (i = 0; i < new_node->ondisk->count; ++i) {
1675                 elm = &new_node->ondisk->elms[i];
1676                 error = btree_set_parent(cursor->trans, new_node, elm);
1677                 if (error) {
1678                         panic("btree_split_internal: btree-fixup problem");
1679                 }
1680         }
1681         hammer_modify_node_done(new_node);
1682
1683         /*
1684          * The filesystem's root B-Tree pointer may have to be updated.
1685          */
1686         if (made_root) {
1687                 hammer_volume_t volume;
1688
1689                 volume = hammer_get_root_volume(hmp, &error);
1690                 KKASSERT(error == 0);
1691
1692                 hammer_modify_volume_field(cursor->trans, volume,
1693                                            vol0_btree_root);
1694                 volume->ondisk->vol0_btree_root = parent->node_offset;
1695                 hammer_modify_volume_done(volume);
1696                 node->ondisk->parent = parent->node_offset;
1697                 if (cursor->parent) {
1698                         hammer_unlock(&cursor->parent->lock);
1699                         hammer_rel_node(cursor->parent);
1700                 }
1701                 cursor->parent = parent;        /* lock'd and ref'd */
1702                 hammer_rel_volume(volume, 0);
1703         }
1704         hammer_modify_node_done(node);
1705
1706         /*
1707          * Ok, now adjust the cursor depending on which element the original
1708          * index was pointing at.  If we are >= the split point the push node
1709          * is now in the new node.
1710          *
1711          * NOTE: If we are at the split point itself we cannot stay with the
1712          * original node because the push index will point at the right-hand
1713          * boundary, which is illegal.
1714          *
1715          * NOTE: The cursor's parent or parent_index must be adjusted for
1716          * the case where a new parent (new root) was created, and the case
1717          * where the cursor is now pointing at the split node.
1718          */
1719         if (cursor->index >= split) {
1720                 cursor->parent_index = parent_index + 1;
1721                 cursor->index -= split;
1722                 hammer_unlock(&cursor->node->lock);
1723                 hammer_rel_node(cursor->node);
1724                 cursor->node = new_node;        /* locked and ref'd */
1725         } else {
1726                 cursor->parent_index = parent_index;
1727                 hammer_unlock(&new_node->lock);
1728                 hammer_rel_node(new_node);
1729         }
1730
1731         /*
1732          * Fixup left and right bounds
1733          */
1734         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1735         cursor->left_bound = &parent_elm[0].internal.base;
1736         cursor->right_bound = &parent_elm[1].internal.base;
1737         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1738                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1739         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1740                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1741
1742 done:
1743         hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
1744         hammer_cursor_downgrade(cursor);
1745         return (error);
1746 }
1747
1748 /*
1749  * Same as the above, but splits a full leaf node.
1750  *
1751  * This function
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[1].base = hmp->root_btree_end;
1838                 /* ondisk->elms[1].base.btype = not used */
1839                 hammer_modify_node_done(parent);
1840                 made_root = 1;
1841                 parent_index = 0;       /* insertion point in parent */
1842         } else {
1843                 made_root = 0;
1844                 parent = cursor->parent;
1845                 parent_index = cursor->parent_index;
1846         }
1847
1848         /*
1849          * Split leaf into new_leaf at the split point.  Select a separator
1850          * value in-between the two leafs but with a bent towards the right
1851          * leaf since comparisons use an 'elm >= separator' inequality.
1852          *
1853          *  L L L L L L L L
1854          *
1855          *       x x P x x
1856          *        s S S s
1857          *         /   \
1858          *  L L L L     L L L L
1859          */
1860         new_leaf = hammer_alloc_btree(cursor->trans, 0, &error);
1861         if (new_leaf == NULL) {
1862                 if (made_root) {
1863                         hammer_unlock(&parent->lock);
1864                         hammer_delete_node(cursor->trans, parent);
1865                         hammer_rel_node(parent);
1866                 }
1867                 goto done;
1868         }
1869         hammer_lock_ex(&new_leaf->lock);
1870
1871         /*
1872          * Create the new node and copy the leaf elements from the split
1873          * point on to the new node.
1874          */
1875         hammer_modify_node_all(cursor->trans, leaf);
1876         hammer_modify_node_noundo(cursor->trans, new_leaf);
1877         ondisk = leaf->ondisk;
1878         elm = &ondisk->elms[split];
1879         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1880         new_leaf->ondisk->count = ondisk->count - split;
1881         new_leaf->ondisk->parent = parent->node_offset;
1882         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1883         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1884         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1885         hammer_modify_node_done(new_leaf);
1886         hammer_cursor_split_node(leaf, new_leaf, split);
1887
1888         /*
1889          * Cleanup the original node.  Because this is a leaf node and
1890          * leaf nodes do not have a right-hand boundary, there
1891          * aren't any special edge cases to clean up.  We just fixup the
1892          * count.
1893          */
1894         ondisk->count = split;
1895
1896         /*
1897          * Insert the separator into the parent, fixup the parent's
1898          * reference to the original node, and reference the new node.
1899          * The separator is P.
1900          *
1901          * Remember that base.count does not include the right-hand boundary.
1902          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1903          */
1904         hammer_modify_node_all(cursor->trans, parent);
1905         ondisk = parent->ondisk;
1906         KKASSERT(split != 0);
1907         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1908         parent_elm = &ondisk->elms[parent_index+1];
1909         bcopy(parent_elm, parent_elm + 1,
1910               (ondisk->count - parent_index) * esize);
1911
1912         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1913         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1914         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1915         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1916         mid_boundary = &parent_elm->base;
1917         ++ondisk->count;
1918         hammer_modify_node_done(parent);
1919         hammer_cursor_inserted_element(parent, parent_index + 1);
1920
1921         /*
1922          * The filesystem's root B-Tree pointer may have to be updated.
1923          */
1924         if (made_root) {
1925                 hammer_volume_t volume;
1926
1927                 volume = hammer_get_root_volume(hmp, &error);
1928                 KKASSERT(error == 0);
1929
1930                 hammer_modify_volume_field(cursor->trans, volume,
1931                                            vol0_btree_root);
1932                 volume->ondisk->vol0_btree_root = parent->node_offset;
1933                 hammer_modify_volume_done(volume);
1934                 leaf->ondisk->parent = parent->node_offset;
1935                 if (cursor->parent) {
1936                         hammer_unlock(&cursor->parent->lock);
1937                         hammer_rel_node(cursor->parent);
1938                 }
1939                 cursor->parent = parent;        /* lock'd and ref'd */
1940                 hammer_rel_volume(volume, 0);
1941         }
1942         hammer_modify_node_done(leaf);
1943
1944         /*
1945          * Ok, now adjust the cursor depending on which element the original
1946          * index was pointing at.  If we are >= the split point the push node
1947          * is now in the new node.
1948          *
1949          * NOTE: If we are at the split point itself we need to select the
1950          * old or new node based on where key_beg's insertion point will be.
1951          * If we pick the wrong side the inserted element will wind up in
1952          * the wrong leaf node and outside that node's bounds.
1953          */
1954         if (cursor->index > split ||
1955             (cursor->index == split &&
1956              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1957                 cursor->parent_index = parent_index + 1;
1958                 cursor->index -= split;
1959                 hammer_unlock(&cursor->node->lock);
1960                 hammer_rel_node(cursor->node);
1961                 cursor->node = new_leaf;
1962         } else {
1963                 cursor->parent_index = parent_index;
1964                 hammer_unlock(&new_leaf->lock);
1965                 hammer_rel_node(new_leaf);
1966         }
1967
1968         /*
1969          * Fixup left and right bounds
1970          */
1971         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1972         cursor->left_bound = &parent_elm[0].internal.base;
1973         cursor->right_bound = &parent_elm[1].internal.base;
1974
1975         /*
1976          * Assert that the bounds are correct.
1977          */
1978         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1979                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1980         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1981                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1982         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
1983         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
1984
1985 done:
1986         hammer_cursor_downgrade(cursor);
1987         return (error);
1988 }
1989
1990 #if 0
1991
1992 /*
1993  * Recursively correct the right-hand boundary's create_tid to (tid) as
1994  * long as the rest of the key matches.  We have to recurse upward in
1995  * the tree as well as down the left side of each parent's right node.
1996  *
1997  * Return EDEADLK if we were only partially successful, forcing the caller
1998  * to try again.  The original cursor is not modified.  This routine can
1999  * also fail with EDEADLK if it is forced to throw away a portion of its
2000  * record history.
2001  *
2002  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
2003  */
2004 struct hammer_rhb {
2005         TAILQ_ENTRY(hammer_rhb) entry;
2006         hammer_node_t   node;
2007         int             index;
2008 };
2009
2010 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
2011
2012 int
2013 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
2014 {
2015         struct hammer_mount *hmp;
2016         struct hammer_rhb_list rhb_list;
2017         hammer_base_elm_t elm;
2018         hammer_node_t orig_node;
2019         struct hammer_rhb *rhb;
2020         int orig_index;
2021         int error;
2022
2023         TAILQ_INIT(&rhb_list);
2024         hmp = cursor->trans->hmp;
2025
2026         /*
2027          * Save our position so we can restore it on return.  This also
2028          * gives us a stable 'elm'.
2029          */
2030         orig_node = cursor->node;
2031         hammer_ref_node(orig_node);
2032         hammer_lock_sh(&orig_node->lock);
2033         orig_index = cursor->index;
2034         elm = &orig_node->ondisk->elms[orig_index].base;
2035
2036         /*
2037          * Now build a list of parents going up, allocating a rhb
2038          * structure for each one.
2039          */
2040         while (cursor->parent) {
2041                 /*
2042                  * Stop if we no longer have any right-bounds to fix up
2043                  */
2044                 if (elm->obj_id != cursor->right_bound->obj_id ||
2045                     elm->rec_type != cursor->right_bound->rec_type ||
2046                     elm->key != cursor->right_bound->key) {
2047                         break;
2048                 }
2049
2050                 /*
2051                  * Stop if the right-hand bound's create_tid does not
2052                  * need to be corrected.
2053                  */
2054                 if (cursor->right_bound->create_tid >= tid)
2055                         break;
2056
2057                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2058                 rhb->node = cursor->parent;
2059                 rhb->index = cursor->parent_index;
2060                 hammer_ref_node(rhb->node);
2061                 hammer_lock_sh(&rhb->node->lock);
2062                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2063
2064                 hammer_cursor_up(cursor);
2065         }
2066
2067         /*
2068          * now safely adjust the right hand bound for each rhb.  This may
2069          * also require taking the right side of the tree and iterating down
2070          * ITS left side.
2071          */
2072         error = 0;
2073         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2074                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2075                 if (error)
2076                         break;
2077                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2078                 hammer_unlock(&rhb->node->lock);
2079                 hammer_rel_node(rhb->node);
2080                 kfree(rhb, hmp->m_misc);
2081
2082                 switch (cursor->node->ondisk->type) {
2083                 case HAMMER_BTREE_TYPE_INTERNAL:
2084                         /*
2085                          * Right-boundary for parent at internal node
2086                          * is one element to the right of the element whos
2087                          * right boundary needs adjusting.  We must then
2088                          * traverse down the left side correcting any left
2089                          * bounds (which may now be too far to the left).
2090                          */
2091                         ++cursor->index;
2092                         error = hammer_btree_correct_lhb(cursor, tid);
2093                         break;
2094                 default:
2095                         panic("hammer_btree_correct_rhb(): Bad node type");
2096                         error = EINVAL;
2097                         break;
2098                 }
2099         }
2100
2101         /*
2102          * Cleanup
2103          */
2104         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2105                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2106                 hammer_unlock(&rhb->node->lock);
2107                 hammer_rel_node(rhb->node);
2108                 kfree(rhb, hmp->m_misc);
2109         }
2110         error = hammer_cursor_seek(cursor, orig_node, orig_index);
2111         hammer_unlock(&orig_node->lock);
2112         hammer_rel_node(orig_node);
2113         return (error);
2114 }
2115
2116 /*
2117  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2118  * bound going downward starting at the current cursor position.
2119  *
2120  * This function does not restore the cursor after use.
2121  */
2122 int
2123 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2124 {
2125         struct hammer_rhb_list rhb_list;
2126         hammer_base_elm_t elm;
2127         hammer_base_elm_t cmp;
2128         struct hammer_rhb *rhb;
2129         struct hammer_mount *hmp;
2130         int error;
2131
2132         TAILQ_INIT(&rhb_list);
2133         hmp = cursor->trans->hmp;
2134
2135         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2136
2137         /*
2138          * Record the node and traverse down the left-hand side for all
2139          * matching records needing a boundary correction.
2140          */
2141         error = 0;
2142         for (;;) {
2143                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2144                 rhb->node = cursor->node;
2145                 rhb->index = cursor->index;
2146                 hammer_ref_node(rhb->node);
2147                 hammer_lock_sh(&rhb->node->lock);
2148                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2149
2150                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2151                         /*
2152                          * Nothing to traverse down if we are at the right
2153                          * boundary of an internal node.
2154                          */
2155                         if (cursor->index == cursor->node->ondisk->count)
2156                                 break;
2157                 } else {
2158                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2159                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2160                                 break;
2161                         panic("Illegal leaf record type %02x", elm->btype);
2162                 }
2163                 error = hammer_cursor_down(cursor);
2164                 if (error)
2165                         break;
2166
2167                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2168                 if (elm->obj_id != cmp->obj_id ||
2169                     elm->rec_type != cmp->rec_type ||
2170                     elm->key != cmp->key) {
2171                         break;
2172                 }
2173                 if (elm->create_tid >= tid)
2174                         break;
2175
2176         }
2177
2178         /*
2179          * Now we can safely adjust the left-hand boundary from the bottom-up.
2180          * The last element we remove from the list is the caller's right hand
2181          * boundary, which must also be adjusted.
2182          */
2183         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2184                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2185                 if (error)
2186                         break;
2187                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2188                 hammer_unlock(&rhb->node->lock);
2189                 hammer_rel_node(rhb->node);
2190                 kfree(rhb, hmp->m_misc);
2191
2192                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2193                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2194                         hammer_modify_node(cursor->trans, cursor->node,
2195                                            &elm->create_tid,
2196                                            sizeof(elm->create_tid));
2197                         elm->create_tid = tid;
2198                         hammer_modify_node_done(cursor->node);
2199                 } else {
2200                         panic("hammer_btree_correct_lhb(): Bad element type");
2201                 }
2202         }
2203
2204         /*
2205          * Cleanup
2206          */
2207         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2208                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2209                 hammer_unlock(&rhb->node->lock);
2210                 hammer_rel_node(rhb->node);
2211                 kfree(rhb, hmp->m_misc);
2212         }
2213         return (error);
2214 }
2215
2216 #endif
2217
2218 /*
2219  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2220  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2221  * the operation due to a deadlock, or some other error.
2222  *
2223  * This routine is initially called with an empty leaf and may be
2224  * recursively called with single-element internal nodes.
2225  *
2226  * It should also be noted that when removing empty leaves we must be sure
2227  * to test and update mirror_tid because another thread may have deadlocked
2228  * against us (or someone) trying to propagate it up and cannot retry once
2229  * the node has been deleted.
2230  *
2231  * On return the cursor may end up pointing to an internal node, suitable
2232  * for further iteration but not for an immediate insertion or deletion.
2233  */
2234 static int
2235 btree_remove(hammer_cursor_t cursor)
2236 {
2237         hammer_node_ondisk_t ondisk;
2238         hammer_btree_elm_t elm;
2239         hammer_node_t node;
2240         hammer_node_t parent;
2241         const int esize = sizeof(*elm);
2242         int error;
2243
2244         node = cursor->node;
2245
2246         /*
2247          * When deleting the root of the filesystem convert it to
2248          * an empty leaf node.  Internal nodes cannot be empty.
2249          */
2250         ondisk = node->ondisk;
2251         if (ondisk->parent == 0) {
2252                 KKASSERT(cursor->parent == NULL);
2253                 hammer_modify_node_all(cursor->trans, node);
2254                 KKASSERT(ondisk == node->ondisk);
2255                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2256                 ondisk->count = 0;
2257                 hammer_modify_node_done(node);
2258                 cursor->index = 0;
2259                 return(0);
2260         }
2261
2262         parent = cursor->parent;
2263
2264         /*
2265          * Attempt to remove the parent's reference to the child.  If the
2266          * parent would become empty we have to recurse.  If we fail we
2267          * leave the parent pointing to an empty leaf node.
2268          *
2269          * We have to recurse successfully before we can delete the internal
2270          * node as it is illegal to have empty internal nodes.  Even though
2271          * the operation may be aborted we must still fixup any unlocked
2272          * cursors as if we had deleted the element prior to recursing
2273          * (by calling hammer_cursor_deleted_element()) so those cursors
2274          * are properly forced up the chain by the recursion.
2275          */
2276         if (parent->ondisk->count == 1) {
2277                 /*
2278                  * This special cursor_up_locked() call leaves the original
2279                  * node exclusively locked and referenced, leaves the
2280                  * original parent locked (as the new node), and locks the
2281                  * new parent.  It can return EDEADLK.
2282                  *
2283                  * We cannot call hammer_cursor_removed_node() until we are
2284                  * actually able to remove the node.  If we did then tracked
2285                  * cursors in the middle of iterations could be repointed
2286                  * to a parent node.  If this occurs they could end up
2287                  * scanning newly inserted records into the node (that could
2288                  * not be deleted) when they push down again.
2289                  *
2290                  * Due to the way the recursion works the final parent is left
2291                  * in cursor->parent after the recursion returns.  Each
2292                  * layer on the way back up is thus able to call
2293                  * hammer_cursor_removed_node() and 'jump' the node up to
2294                  * the (same) final parent.
2295                  *
2296                  * NOTE!  The local variable 'parent' is invalid after we
2297                  *        call hammer_cursor_up_locked().
2298                  */
2299                 error = hammer_cursor_up_locked(cursor);
2300                 parent = NULL;
2301
2302                 if (error == 0) {
2303                         hammer_cursor_deleted_element(cursor->node, 0);
2304                         error = btree_remove(cursor);
2305                         if (error == 0) {
2306                                 KKASSERT(node != cursor->node);
2307                                 hammer_cursor_removed_node(
2308                                         node, cursor->node,
2309                                         cursor->index);
2310                                 hammer_modify_node_all(cursor->trans, node);
2311                                 ondisk = node->ondisk;
2312                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2313                                 ondisk->count = 0;
2314                                 hammer_modify_node_done(node);
2315                                 hammer_flush_node(node, 0);
2316                                 hammer_delete_node(cursor->trans, node);
2317                         } else {
2318                                 /*
2319                                  * Defer parent removal because we could not
2320                                  * get the lock, just let the leaf remain
2321                                  * empty.
2322                                  */
2323                                 /**/
2324                         }
2325                         hammer_unlock(&node->lock);
2326                         hammer_rel_node(node);
2327                 } else {
2328                         /*
2329                          * Defer parent removal because we could not
2330                          * get the lock, just let the leaf remain
2331                          * empty.
2332                          */
2333                         /**/
2334                 }
2335         } else {
2336                 KKASSERT(parent->ondisk->count > 1);
2337
2338                 hammer_modify_node_all(cursor->trans, parent);
2339                 ondisk = parent->ondisk;
2340                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2341
2342                 elm = &ondisk->elms[cursor->parent_index];
2343                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2344                 KKASSERT(ondisk->count > 0);
2345
2346                 /*
2347                  * We must retain the highest mirror_tid.  The deleted
2348                  * range is now encompassed by the element to the left.
2349                  * If we are already at the left edge the new left edge
2350                  * inherits mirror_tid.
2351                  *
2352                  * Note that bounds of the parent to our parent may create
2353                  * a gap to the left of our left-most node or to the right
2354                  * of our right-most node.  The gap is silently included
2355                  * in the mirror_tid's area of effect from the point of view
2356                  * of the scan.
2357                  */
2358                 if (cursor->parent_index) {
2359                         if (elm[-1].internal.mirror_tid <
2360                             elm[0].internal.mirror_tid) {
2361                                 elm[-1].internal.mirror_tid =
2362                                     elm[0].internal.mirror_tid;
2363                         }
2364                 } else {
2365                         if (elm[1].internal.mirror_tid <
2366                             elm[0].internal.mirror_tid) {
2367                                 elm[1].internal.mirror_tid =
2368                                     elm[0].internal.mirror_tid;
2369                         }
2370                 }
2371
2372                 /*
2373                  * Delete the subtree reference in the parent.  Include
2374                  * boundary element at end.
2375                  */
2376                 bcopy(&elm[1], &elm[0],
2377                       (ondisk->count - cursor->parent_index) * esize);
2378                 --ondisk->count;
2379                 hammer_modify_node_done(parent);
2380                 hammer_cursor_removed_node(node, parent, cursor->parent_index);
2381                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2382                 hammer_flush_node(node, 0);
2383                 hammer_delete_node(cursor->trans, node);
2384
2385                 /*
2386                  * cursor->node is invalid, cursor up to make the cursor
2387                  * valid again.  We have to flag the condition in case
2388                  * another thread wiggles an insertion in during an
2389                  * iteration.
2390                  */
2391                 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
2392                 error = hammer_cursor_up(cursor);
2393         }
2394         return (error);
2395 }
2396
2397 /*
2398  * Propagate cursor->trans->tid up the B-Tree starting at the current
2399  * cursor position using pseudofs info gleaned from the passed inode.
2400  *
2401  * The passed inode has no relationship to the cursor position other
2402  * then being in the same pseudofs as the insertion or deletion we
2403  * are propagating the mirror_tid for.
2404  *
2405  * WARNING!  Because we push and pop the passed cursor, it may be
2406  *           modified by other B-Tree operations while it is unlocked
2407  *           and things like the node & leaf pointers, and indexes might
2408  *           change.
2409  */
2410 void
2411 hammer_btree_do_propagation(hammer_cursor_t cursor,
2412                             hammer_pseudofs_inmem_t pfsm,
2413                             hammer_btree_leaf_elm_t leaf)
2414 {
2415         hammer_cursor_t ncursor;
2416         hammer_tid_t mirror_tid;
2417         int error __debugvar;
2418
2419         /*
2420          * We do not propagate a mirror_tid if the filesystem was mounted
2421          * in no-mirror mode.
2422          */
2423         if (cursor->trans->hmp->master_id < 0)
2424                 return;
2425
2426         /*
2427          * This is a bit of a hack because we cannot deadlock or return
2428          * EDEADLK here.  The related operation has already completed and
2429          * we must propagate the mirror_tid now regardless.
2430          *
2431          * Generate a new cursor which inherits the original's locks and
2432          * unlock the original.  Use the new cursor to propagate the
2433          * mirror_tid.  Then clean up the new cursor and reacquire locks
2434          * on the original.
2435          *
2436          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2437          * original's locks and the original is tracked and must be
2438          * re-locked.
2439          */
2440         mirror_tid = cursor->node->ondisk->mirror_tid;
2441         KKASSERT(mirror_tid != 0);
2442         ncursor = hammer_push_cursor(cursor);
2443         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2444         KKASSERT(error == 0);
2445         hammer_pop_cursor(cursor, ncursor);
2446         /* WARNING: cursor's leaf pointer may change after pop */
2447 }
2448
2449
2450 /*
2451  * Propagate a mirror TID update upwards through the B-Tree to the root.
2452  *
2453  * A locked internal node must be passed in.  The node will remain locked
2454  * on return.
2455  *
2456  * This function syncs mirror_tid at the specified internal node's element,
2457  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2458  */
2459 static int
2460 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2461 {
2462         hammer_btree_internal_elm_t elm;
2463         hammer_node_t node;
2464         int error;
2465
2466         for (;;) {
2467                 error = hammer_cursor_up(cursor);
2468                 if (error == 0)
2469                         error = hammer_cursor_upgrade(cursor);
2470
2471                 /*
2472                  * We can ignore HAMMER_CURSOR_ITERATE_CHECK, the
2473                  * cursor will still be properly positioned for
2474                  * mirror propagation, just not for iterations.
2475                  */
2476                 while (error == EDEADLK) {
2477                         hammer_recover_cursor(cursor);
2478                         error = hammer_cursor_upgrade(cursor);
2479                 }
2480                 if (error)
2481                         break;
2482
2483                 /*
2484                  * If the cursor deadlocked it could end up at a leaf
2485                  * after we lost the lock.
2486                  */
2487                 node = cursor->node;
2488                 if (node->ondisk->type != HAMMER_BTREE_TYPE_INTERNAL)
2489                         continue;
2490
2491                 /*
2492                  * Adjust the node's element
2493                  */
2494                 elm = &node->ondisk->elms[cursor->index].internal;
2495                 if (elm->mirror_tid >= mirror_tid)
2496                         break;
2497                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2498                                    sizeof(elm->mirror_tid));
2499                 elm->mirror_tid = mirror_tid;
2500                 hammer_modify_node_done(node);
2501                 if (hammer_debug_general & 0x0002) {
2502                         kprintf("mirror_propagate: propagate "
2503                                 "%016llx @%016llx:%d\n",
2504                                 (long long)mirror_tid,
2505                                 (long long)node->node_offset,
2506                                 cursor->index);
2507                 }
2508
2509
2510                 /*
2511                  * Adjust the node's mirror_tid aggregator
2512                  */
2513                 if (node->ondisk->mirror_tid >= mirror_tid)
2514                         return(0);
2515                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2516                 node->ondisk->mirror_tid = mirror_tid;
2517                 hammer_modify_node_done(node);
2518                 if (hammer_debug_general & 0x0002) {
2519                         kprintf("mirror_propagate: propagate "
2520                                 "%016llx @%016llx\n",
2521                                 (long long)mirror_tid,
2522                                 (long long)node->node_offset);
2523                 }
2524         }
2525         if (error == ENOENT)
2526                 error = 0;
2527         return(error);
2528 }
2529
2530 hammer_node_t
2531 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2532                         int *parent_indexp, int *errorp, int try_exclusive)
2533 {
2534         hammer_node_t parent;
2535         hammer_btree_elm_t elm;
2536         int i;
2537
2538         /*
2539          * Get the node
2540          */
2541         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2542         if (*errorp) {
2543                 KKASSERT(parent == NULL);
2544                 return(NULL);
2545         }
2546         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2547
2548         /*
2549          * Lock the node
2550          */
2551         if (try_exclusive) {
2552                 if (hammer_lock_ex_try(&parent->lock)) {
2553                         hammer_rel_node(parent);
2554                         *errorp = EDEADLK;
2555                         return(NULL);
2556                 }
2557         } else {
2558                 hammer_lock_sh(&parent->lock);
2559         }
2560
2561         /*
2562          * Figure out which element in the parent is pointing to the
2563          * child.
2564          */
2565         if (node->ondisk->count) {
2566                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2567                                              parent->ondisk);
2568         } else {
2569                 i = 0;
2570         }
2571         while (i < parent->ondisk->count) {
2572                 elm = &parent->ondisk->elms[i];
2573                 if (elm->internal.subtree_offset == node->node_offset)
2574                         break;
2575                 ++i;
2576         }
2577         if (i == parent->ondisk->count) {
2578                 hammer_unlock(&parent->lock);
2579                 panic("Bad B-Tree link: parent %p node %p", parent, node);
2580         }
2581         *parent_indexp = i;
2582         KKASSERT(*errorp == 0);
2583         return(parent);
2584 }
2585
2586 /*
2587  * The element (elm) has been moved to a new internal node (node).
2588  *
2589  * If the element represents a pointer to an internal node that node's
2590  * parent must be adjusted to the element's new location.
2591  *
2592  * XXX deadlock potential here with our exclusive locks
2593  */
2594 int
2595 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2596                  hammer_btree_elm_t elm)
2597 {
2598         hammer_node_t child;
2599         int error;
2600
2601         error = 0;
2602
2603         switch(elm->base.btype) {
2604         case HAMMER_BTREE_TYPE_INTERNAL:
2605         case HAMMER_BTREE_TYPE_LEAF:
2606                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2607                                         0, &error);
2608                 if (error == 0) {
2609                         hammer_modify_node_field(trans, child, parent);
2610                         child->ondisk->parent = node->node_offset;
2611                         hammer_modify_node_done(child);
2612                         hammer_rel_node(child);
2613                 }
2614                 break;
2615         default:
2616                 break;
2617         }
2618         return(error);
2619 }
2620
2621 /*
2622  * Initialize the root of a recursive B-Tree node lock list structure.
2623  */
2624 void
2625 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2626 {
2627         TAILQ_INIT(&parent->list);
2628         parent->parent = NULL;
2629         parent->node = node;
2630         parent->index = -1;
2631         parent->count = node->ondisk->count;
2632         parent->copy = NULL;
2633         parent->flags = 0;
2634 }
2635
2636 /*
2637  * Initialize a cache of hammer_node_lock's including space allocated
2638  * for node copies.
2639  *
2640  * This is used by the rebalancing code to preallocate the copy space
2641  * for ~4096 B-Tree nodes (16MB of data) prior to acquiring any HAMMER
2642  * locks, otherwise we can blow out the pageout daemon's emergency
2643  * reserve and deadlock it.
2644  *
2645  * NOTE: HAMMER_NODE_LOCK_LCACHE is not set on items cached in the lcache.
2646  *       The flag is set when the item is pulled off the cache for use.
2647  */
2648 void
2649 hammer_btree_lcache_init(hammer_mount_t hmp, hammer_node_lock_t lcache,
2650                          int depth)
2651 {
2652         hammer_node_lock_t item;
2653         int count;
2654
2655         for (count = 1; depth; --depth)
2656                 count *= HAMMER_BTREE_LEAF_ELMS;
2657         bzero(lcache, sizeof(*lcache));
2658         TAILQ_INIT(&lcache->list);
2659         while (count) {
2660                 item = kmalloc(sizeof(*item), hmp->m_misc, M_WAITOK|M_ZERO);
2661                 item->copy = kmalloc(sizeof(*item->copy),
2662                                      hmp->m_misc, M_WAITOK);
2663                 TAILQ_INIT(&item->list);
2664                 TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2665                 --count;
2666         }
2667 }
2668
2669 void
2670 hammer_btree_lcache_free(hammer_mount_t hmp, hammer_node_lock_t lcache)
2671 {
2672         hammer_node_lock_t item;
2673
2674         while ((item = TAILQ_FIRST(&lcache->list)) != NULL) {
2675                 TAILQ_REMOVE(&lcache->list, item, entry);
2676                 KKASSERT(item->copy);
2677                 KKASSERT(TAILQ_EMPTY(&item->list));
2678                 kfree(item->copy, hmp->m_misc);
2679                 kfree(item, hmp->m_misc);
2680         }
2681         KKASSERT(lcache->copy == NULL);
2682 }
2683
2684 /*
2685  * Exclusively lock all the children of node.  This is used by the split
2686  * code to prevent anyone from accessing the children of a cursor node
2687  * while we fix-up its parent offset.
2688  *
2689  * If we don't lock the children we can really mess up cursors which block
2690  * trying to cursor-up into our node.
2691  *
2692  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2693  * error is returned the cursor is adjusted to block on termination.
2694  *
2695  * The caller is responsible for managing parent->node, the root's node
2696  * is usually aliased from a cursor.
2697  */
2698 int
2699 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2700                            hammer_node_lock_t parent,
2701                            hammer_node_lock_t lcache)
2702 {
2703         hammer_node_t node;
2704         hammer_node_lock_t item;
2705         hammer_node_ondisk_t ondisk;
2706         hammer_btree_elm_t elm;
2707         hammer_node_t child;
2708         struct hammer_mount *hmp;
2709         int error;
2710         int i;
2711
2712         node = parent->node;
2713         ondisk = node->ondisk;
2714         error = 0;
2715         hmp = cursor->trans->hmp;
2716
2717         /*
2718          * We really do not want to block on I/O with exclusive locks held,
2719          * pre-get the children before trying to lock the mess.  This is
2720          * only done one-level deep for now.
2721          */
2722         for (i = 0; i < ondisk->count; ++i) {
2723                 ++hammer_stats_btree_elements;
2724                 elm = &ondisk->elms[i];
2725                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2726                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2727                         continue;
2728                 }
2729                 child = hammer_get_node(cursor->trans,
2730                                         elm->internal.subtree_offset,
2731                                         0, &error);
2732                 if (child)
2733                         hammer_rel_node(child);
2734         }
2735
2736         /*
2737          * Do it for real
2738          */
2739         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2740                 ++hammer_stats_btree_elements;
2741                 elm = &ondisk->elms[i];
2742
2743                 switch(elm->base.btype) {
2744                 case HAMMER_BTREE_TYPE_INTERNAL:
2745                 case HAMMER_BTREE_TYPE_LEAF:
2746                         KKASSERT(elm->internal.subtree_offset != 0);
2747                         child = hammer_get_node(cursor->trans,
2748                                                 elm->internal.subtree_offset,
2749                                                 0, &error);
2750                         break;
2751                 default:
2752                         child = NULL;
2753                         break;
2754                 }
2755                 if (child) {
2756                         if (hammer_lock_ex_try(&child->lock) != 0) {
2757                                 if (cursor->deadlk_node == NULL) {
2758                                         cursor->deadlk_node = child;
2759                                         hammer_ref_node(cursor->deadlk_node);
2760                                 }
2761                                 error = EDEADLK;
2762                                 hammer_rel_node(child);
2763                         } else {
2764                                 if (lcache) {
2765                                         item = TAILQ_FIRST(&lcache->list);
2766                                         KKASSERT(item != NULL);
2767                                         item->flags |= HAMMER_NODE_LOCK_LCACHE;
2768                                         TAILQ_REMOVE(&lcache->list,
2769                                                      item, entry);
2770                                 } else {
2771                                         item = kmalloc(sizeof(*item),
2772                                                        hmp->m_misc,
2773                                                        M_WAITOK|M_ZERO);
2774                                         TAILQ_INIT(&item->list);
2775                                 }
2776
2777                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2778                                 item->parent = parent;
2779                                 item->node = child;
2780                                 item->index = i;
2781                                 item->count = child->ondisk->count;
2782
2783                                 /*
2784                                  * Recurse (used by the rebalancing code)
2785                                  */
2786                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2787                                         error = hammer_btree_lock_children(
2788                                                         cursor,
2789                                                         depth - 1,
2790                                                         item,
2791                                                         lcache);
2792                                 }
2793                         }
2794                 }
2795         }
2796         if (error)
2797                 hammer_btree_unlock_children(hmp, parent, lcache);
2798         return(error);
2799 }
2800
2801 /*
2802  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2803  * including the parent.
2804  */
2805 void
2806 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2807 {
2808         hammer_mount_t hmp = cursor->trans->hmp;
2809         hammer_node_lock_t item;
2810
2811         if (parent->copy == NULL) {
2812                 KKASSERT((parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0);
2813                 parent->copy = kmalloc(sizeof(*parent->copy),
2814                                        hmp->m_misc, M_WAITOK);
2815         }
2816         KKASSERT((parent->flags & HAMMER_NODE_LOCK_UPDATED) == 0);
2817         *parent->copy = *parent->node->ondisk;
2818         TAILQ_FOREACH(item, &parent->list, entry) {
2819                 hammer_btree_lock_copy(cursor, item);
2820         }
2821 }
2822
2823 /*
2824  * Recursively sync modified copies to the media.
2825  */
2826 int
2827 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2828 {
2829         hammer_node_lock_t item;
2830         int count = 0;
2831
2832         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2833                 ++count;
2834                 hammer_modify_node_all(cursor->trans, parent->node);
2835                 *parent->node->ondisk = *parent->copy;
2836                 hammer_modify_node_done(parent->node);
2837                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2838                         hammer_flush_node(parent->node, 0);
2839                         hammer_delete_node(cursor->trans, parent->node);
2840                 }
2841         }
2842         TAILQ_FOREACH(item, &parent->list, entry) {
2843                 count += hammer_btree_sync_copy(cursor, item);
2844         }
2845         return(count);
2846 }
2847
2848 /*
2849  * Release previously obtained node locks.  The caller is responsible for
2850  * cleaning up parent->node itself (its usually just aliased from a cursor),
2851  * but this function will take care of the copies.
2852  *
2853  * NOTE: The root node is not placed in the lcache and node->copy is not
2854  *       deallocated when lcache != NULL.
2855  */
2856 void
2857 hammer_btree_unlock_children(hammer_mount_t hmp, hammer_node_lock_t parent,
2858                              hammer_node_lock_t lcache)
2859 {
2860         hammer_node_lock_t item;
2861         hammer_node_ondisk_t copy;
2862
2863         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2864                 TAILQ_REMOVE(&parent->list, item, entry);
2865                 hammer_btree_unlock_children(hmp, item, lcache);
2866                 hammer_unlock(&item->node->lock);
2867                 hammer_rel_node(item->node);
2868                 if (lcache) {
2869                         /*
2870                          * NOTE: When placing the item back in the lcache
2871                          *       the flag is cleared by the bzero().
2872                          *       Remaining fields are cleared as a safety
2873                          *       measure.
2874                          */
2875                         KKASSERT(item->flags & HAMMER_NODE_LOCK_LCACHE);
2876                         KKASSERT(TAILQ_EMPTY(&item->list));
2877                         copy = item->copy;
2878                         bzero(item, sizeof(*item));
2879                         TAILQ_INIT(&item->list);
2880                         item->copy = copy;
2881                         if (copy)
2882                                 bzero(copy, sizeof(*copy));
2883                         TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2884                 } else {
2885                         kfree(item, hmp->m_misc);
2886                 }
2887         }
2888         if (parent->copy && (parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0) {
2889                 kfree(parent->copy, hmp->m_misc);
2890                 parent->copy = NULL;    /* safety */
2891         }
2892 }
2893
2894 /************************************************************************
2895  *                         MISCELLANIOUS SUPPORT                        *
2896  ************************************************************************/
2897
2898 /*
2899  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2900  *
2901  * Note that for this particular function a return value of -1, 0, or +1
2902  * can denote a match if create_tid is otherwise discounted.  A create_tid
2903  * of zero is considered to be 'infinity' in comparisons.
2904  *
2905  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2906  */
2907 int
2908 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2909 {
2910         if (key1->localization < key2->localization)
2911                 return(-5);
2912         if (key1->localization > key2->localization)
2913                 return(5);
2914
2915         if (key1->obj_id < key2->obj_id)
2916                 return(-4);
2917         if (key1->obj_id > key2->obj_id)
2918                 return(4);
2919
2920         if (key1->rec_type < key2->rec_type)
2921                 return(-3);
2922         if (key1->rec_type > key2->rec_type)
2923                 return(3);
2924
2925         if (key1->key < key2->key)
2926                 return(-2);
2927         if (key1->key > key2->key)
2928                 return(2);
2929
2930         /*
2931          * A create_tid of zero indicates a record which is undeletable
2932          * and must be considered to have a value of positive infinity.
2933          */
2934         if (key1->create_tid == 0) {
2935                 if (key2->create_tid == 0)
2936                         return(0);
2937                 return(1);
2938         }
2939         if (key2->create_tid == 0)
2940                 return(-1);
2941         if (key1->create_tid < key2->create_tid)
2942                 return(-1);
2943         if (key1->create_tid > key2->create_tid)
2944                 return(1);
2945         return(0);
2946 }
2947
2948 /*
2949  * Test a timestamp against an element to determine whether the
2950  * element is visible.  A timestamp of 0 means 'infinity'.
2951  */
2952 int
2953 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2954 {
2955         if (asof == 0) {
2956                 if (base->delete_tid)
2957                         return(1);
2958                 return(0);
2959         }
2960         if (asof < base->create_tid)
2961                 return(-1);
2962         if (base->delete_tid && asof >= base->delete_tid)
2963                 return(1);
2964         return(0);
2965 }
2966
2967 /*
2968  * Create a separator half way inbetween key1 and key2.  For fields just
2969  * one unit apart, the separator will match key2.  key1 is on the left-hand
2970  * side and key2 is on the right-hand side.
2971  *
2972  * key2 must be >= the separator.  It is ok for the separator to match key2.
2973  *
2974  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2975  * key2.
2976  *
2977  * NOTE: It might be beneficial to just scrap this whole mess and just
2978  * set the separator to key2.
2979  */
2980 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2981         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2982
2983 static void
2984 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2985                       hammer_base_elm_t dest)
2986 {
2987         bzero(dest, sizeof(*dest));
2988
2989         dest->rec_type = key2->rec_type;
2990         dest->key = key2->key;
2991         dest->obj_id = key2->obj_id;
2992         dest->create_tid = key2->create_tid;
2993
2994         MAKE_SEPARATOR(key1, key2, dest, localization);
2995         if (key1->localization == key2->localization) {
2996                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
2997                 if (key1->obj_id == key2->obj_id) {
2998                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
2999                         if (key1->rec_type == key2->rec_type) {
3000                                 MAKE_SEPARATOR(key1, key2, dest, key);
3001                                 /*
3002                                  * Don't bother creating a separator for
3003                                  * create_tid, which also conveniently avoids
3004                                  * having to handle the create_tid == 0
3005                                  * (infinity) case.  Just leave create_tid
3006                                  * set to key2.
3007                                  *
3008                                  * Worst case, dest matches key2 exactly,
3009                                  * which is acceptable.
3010                                  */
3011                         }
3012                 }
3013         }
3014 }
3015
3016 #undef MAKE_SEPARATOR
3017
3018 /*
3019  * Return whether a generic internal or leaf node is full
3020  */
3021 static int
3022 btree_node_is_full(hammer_node_ondisk_t node)
3023 {
3024         switch(node->type) {
3025         case HAMMER_BTREE_TYPE_INTERNAL:
3026                 if (node->count == HAMMER_BTREE_INT_ELMS)
3027                         return(1);
3028                 break;
3029         case HAMMER_BTREE_TYPE_LEAF:
3030                 if (node->count == HAMMER_BTREE_LEAF_ELMS)
3031                         return(1);
3032                 break;
3033         default:
3034                 panic("illegal btree type");
3035         }
3036         return(0);
3037 }
3038
3039 #if 0
3040 static int
3041 btree_max_elements(u_int8_t type)
3042 {
3043         if (type == HAMMER_BTREE_TYPE_LEAF)
3044                 return(HAMMER_BTREE_LEAF_ELMS);
3045         if (type == HAMMER_BTREE_TYPE_INTERNAL)
3046                 return(HAMMER_BTREE_INT_ELMS);
3047         panic("btree_max_elements: bad type %d", type);
3048 }
3049 #endif
3050
3051 void
3052 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
3053 {
3054         hammer_btree_elm_t elm;
3055         int i;
3056
3057         kprintf("node %p count=%d parent=%016llx type=%c\n",
3058                 ondisk, ondisk->count,
3059                 (long long)ondisk->parent, ondisk->type);
3060
3061         /*
3062          * Dump both boundary elements if an internal node
3063          */
3064         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
3065                 for (i = 0; i <= ondisk->count; ++i) {
3066                         elm = &ondisk->elms[i];
3067                         hammer_print_btree_elm(elm, ondisk->type, i);
3068                 }
3069         } else {
3070                 for (i = 0; i < ondisk->count; ++i) {
3071                         elm = &ondisk->elms[i];
3072                         hammer_print_btree_elm(elm, ondisk->type, i);
3073                 }
3074         }
3075 }
3076
3077 void
3078 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
3079 {
3080         kprintf("  %2d", i);
3081         kprintf("\tobj_id       = %016llx\n", (long long)elm->base.obj_id);
3082         kprintf("\tkey          = %016llx\n", (long long)elm->base.key);
3083         kprintf("\tcreate_tid   = %016llx\n", (long long)elm->base.create_tid);
3084         kprintf("\tdelete_tid   = %016llx\n", (long long)elm->base.delete_tid);
3085         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
3086         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
3087         kprintf("\tbtype        = %02x (%c)\n",
3088                 elm->base.btype,
3089                 (elm->base.btype ? elm->base.btype : '?'));
3090         kprintf("\tlocalization = %02x\n", elm->base.localization);
3091
3092         switch(type) {
3093         case HAMMER_BTREE_TYPE_INTERNAL:
3094                 kprintf("\tsubtree_off  = %016llx\n",
3095                         (long long)elm->internal.subtree_offset);
3096                 break;
3097         case HAMMER_BTREE_TYPE_RECORD:
3098                 kprintf("\tdata_offset  = %016llx\n",
3099                         (long long)elm->leaf.data_offset);
3100                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
3101                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
3102                 break;
3103         }
3104 }