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  * $DragonFly: src/sys/vfs/hammer/hammer_btree.c,v 1.76 2008/08/06 15:38:58 dillon Exp $
  35  */
  36
  37 /*
  38  * HAMMER B-Tree index
  39  *
  40  * HAMMER implements a modified B+Tree.  In documentation this will
  41  * simply be refered to as the HAMMER B-Tree.  Basically a HAMMER B-Tree
  42  * looks like a B+Tree (A B-Tree which stores its records only at the leafs
  43  * of the tree), but adds two additional boundary elements which describe
  44  * the left-most and right-most element a node is able to represent.  In
  45  * otherwords, we have boundary elements at the two ends of a B-Tree node
  46  * instead of sub-tree pointers.
  47  *
  48  * A B-Tree internal node looks like this:
  49  *
  50  *      B N N N N N N B   <-- boundary and internal elements
  51  *       S S S S S S S    <-- subtree pointers
  52  *
  53  * A B-Tree leaf node basically looks like this:
  54  *
  55  *      L L L L L L L L   <-- leaf elemenets
  56  *
  57  * The radix for an internal node is 1 less then a leaf but we get a
  58  * number of significant benefits for our troubles.
  59  *
  60  * The big benefit to using a B-Tree containing boundary information
  61  * is that it is possible to cache pointers into the middle of the tree
  62  * and not have to start searches, insertions, OR deletions at the root
  63  * node.   In particular, searches are able to progress in a definitive
  64  * direction from any point in the tree without revisting nodes.  This
  65  * greatly improves the efficiency of many operations, most especially
  66  * record appends.
  67  *
  68  * B-Trees also make the stacking of trees fairly straightforward.
  69  *
  70  * INSERTIONS:  A search performed with the intention of doing
  71  * an insert will guarantee that the terminal leaf node is not full by
  72  * splitting full nodes.  Splits occur top-down during the dive down the
  73  * B-Tree.
  74  *
  75  * DELETIONS: A deletion makes no attempt to proactively balance the
  76  * tree and will recursively remove nodes that become empty.  If a
  77  * deadlock occurs a deletion may not be able to remove an empty leaf.
  78  * Deletions never allow internal nodes to become empty (that would blow
  79  * up the boundaries).
  80  */
  81 #include "hammer.h"
  82 #include <sys/buf.h>
  83 #include <sys/buf2.h>
  84
  85 static int btree_search(hammer_cursor_t cursor, int flags);
  86 static int btree_split_internal(hammer_cursor_t cursor);
  87 static int btree_split_leaf(hammer_cursor_t cursor);
  88 static int btree_remove(hammer_cursor_t cursor);
  89 static int btree_node_is_full(hammer_node_ondisk_t node);
  90 static int hammer_btree_mirror_propagate(hammer_cursor_t cursor,
  91                         hammer_tid_t mirror_tid);
  92 static void hammer_make_separator(hammer_base_elm_t key1,
  93                         hammer_base_elm_t key2, hammer_base_elm_t dest);
  94 static void hammer_cursor_mirror_filter(hammer_cursor_t cursor);
  95
  96 /*
  97  * Iterate records after a search.  The cursor is iterated forwards past
  98  * the current record until a record matching the key-range requirements
  99  * is found.  ENOENT is returned if the iteration goes past the ending
 100  * key.
 101  *
 102  * The iteration is inclusive of key_beg and can be inclusive or exclusive
 103  * of key_end depending on whether HAMMER_CURSOR_END_INCLUSIVE is set.
 104  *
 105  * When doing an as-of search (cursor->asof != 0), key_beg.create_tid
 106  * may be modified by B-Tree functions.
 107  *
 108  * cursor->key_beg may or may not be modified by this function during
 109  * the iteration.  XXX future - in case of an inverted lock we may have
 110  * to reinitiate the lookup and set key_beg to properly pick up where we
 111  * left off.
 112  *
 113  * If HAMMER_CURSOR_ITERATE_CHECK is set it is possible that the cursor
 114  * was reverse indexed due to being moved to a parent while unlocked,
 115  * and something else might have inserted an element outside the iteration
 116  * range.  When this case occurs the iterator just keeps iterating until
 117  * it gets back into the iteration range (instead of asserting).
 118  *
 119  * NOTE!  EDEADLK *CANNOT* be returned by this procedure.
 120  */
 121 int
 122 hammer_btree_iterate(hammer_cursor_t cursor)
 123 {
 124         hammer_node_ondisk_t node;
 125         hammer_btree_elm_t elm;
 126         hammer_mount_t hmp;
 127         int error = 0;
 128         int r;
 129         int s;
 130
 131         /*
 132          * Skip past the current record
 133          */
 134         hmp = cursor->trans->hmp;
 135         node = cursor->node->ondisk;
 136         if (node == NULL)
 137                 return(ENOENT);
 138         if (cursor->index < node->count &&
 139             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 140                 ++cursor->index;
 141         }
 142
 143         /*
 144          * HAMMER can wind up being cpu-bound.
 145          */
 146         if (++hmp->check_yield > hammer_yield_check) {
 147                 hmp->check_yield = 0;
 148                 lwkt_user_yield();
 149         }
 150
 151
 152         /*
 153          * Loop until an element is found or we are done.
 154          */
 155         for (;;) {
 156                 /*
 157                  * We iterate up the tree and then index over one element
 158                  * while we are at the last element in the current node.
 159                  *
 160                  * If we are at the root of the filesystem, cursor_up
 161                  * returns ENOENT.
 162                  *
 163                  * XXX this could be optimized by storing the information in
 164                  * the parent reference.
 165                  *
 166                  * XXX we can lose the node lock temporarily, this could mess
 167                  * up our scan.
 168                  */
 169                 ++hammer_stats_btree_iterations;
 170                 hammer_flusher_clean_loose_ios(hmp);
 171
 172                 if (cursor->index == node->count) {
 173                         if (hammer_debug_btree) {
 174                                 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
 175                                         (long long)cursor->node->node_offset,
 176                                         cursor->index,
 177                                         (long long)(cursor->parent ? cursor->parent->node_offset : -1),
 178                                         cursor->parent_index,
 179                                         curthread);
 180                         }
 181                         KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
 182                         error = hammer_cursor_up(cursor);
 183                         if (error)
 184                                 break;
 185                         /* reload stale pointer */
 186                         node = cursor->node->ondisk;
 187                         KKASSERT(cursor->index != node->count);
 188
 189                         /*
 190                          * If we are reblocking we want to return internal
 191                          * nodes.  Note that the internal node will be
 192                          * returned multiple times, on each upward recursion
 193                          * from its children.  The caller selects which
 194                          * revisit it cares about (usually first or last only).
 195                          */
 196                         if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
 197                                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 198                                 return(0);
 199                         }
 200                         ++cursor->index;
 201                         continue;
 202                 }
 203
 204                 /*
 205                  * Check internal or leaf element.  Determine if the record
 206                  * at the cursor has gone beyond the end of our range.
 207                  *
 208                  * We recurse down through internal nodes.
 209                  */
 210                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 211                         elm = &node->elms[cursor->index];
 212
 213                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 214                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 215                         if (hammer_debug_btree) {
 216                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
 217                                         (long long)cursor->node->node_offset,
 218                                         cursor->index,
 219                                         (long long)elm[0].internal.base.obj_id,
 220                                         elm[0].internal.base.rec_type,
 221                                         (long long)elm[0].internal.base.key,
 222                                         elm[0].internal.base.localization,
 223                                         r,
 224                                         curthread
 225                                 );
 226                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 227                                         (long long)cursor->node->node_offset,
 228                                         cursor->index + 1,
 229                                         (long long)elm[1].internal.base.obj_id,
 230                                         elm[1].internal.base.rec_type,
 231                                         (long long)elm[1].internal.base.key,
 232                                         elm[1].internal.base.localization,
 233                                         s
 234                                 );
 235                         }
 236
 237                         if (r < 0) {
 238                                 error = ENOENT;
 239                                 break;
 240                         }
 241                         if (r == 0 && (cursor->flags &
 242                                        HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 243                                 error = ENOENT;
 244                                 break;
 245                         }
 246
 247                         /*
 248                          * Better not be zero
 249                          */
 250                         KKASSERT(elm->internal.subtree_offset != 0);
 251
 252                         if (s <= 0) {
 253                                 /*
 254                                  * If running the mirror filter see if we
 255                                  * can skip one or more entire sub-trees.
 256                                  * If we can we return the internal node
 257                                  * and the caller processes the skipped
 258                                  * range (see mirror_read).
 259                                  */
 260                                 if (cursor->flags &
 261                                     HAMMER_CURSOR_MIRROR_FILTERED) {
 262                                         if (elm->internal.mirror_tid <
 263                                             cursor->cmirror->mirror_tid) {
 264                                                 hammer_cursor_mirror_filter(cursor);
 265                                                 return(0);
 266                                         }
 267                                 }
 268                         } else {
 269                                 /*
 270                                  * Normally it would be impossible for the
 271                                  * cursor to have gotten back-indexed,
 272                                  * but it can happen if a node is deleted
 273                                  * and the cursor is moved to its parent
 274                                  * internal node.  ITERATE_CHECK will be set.
 275                                  */
 276                                 KKASSERT(cursor->flags &
 277                                          HAMMER_CURSOR_ITERATE_CHECK);
 278                                 kprintf("hammer_btree_iterate: "
 279                                         "DEBUG: Caught parent seek "
 280                                         "in internal iteration\n");
 281                         }
 282
 283                         error = hammer_cursor_down(cursor);
 284                         if (error)
 285                                 break;
 286                         KKASSERT(cursor->index == 0);
 287                         /* reload stale pointer */
 288                         node = cursor->node->ondisk;
 289                         continue;
 290                 } else {
 291                         elm = &node->elms[cursor->index];
 292                         r = hammer_btree_cmp(&cursor->key_end, &elm->base);
 293                         if (hammer_debug_btree) {
 294                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 295                                         (long long)cursor->node->node_offset,
 296                                         cursor->index,
 297                                         (elm[0].leaf.base.btype ?
 298                                          elm[0].leaf.base.btype : '?'),
 299                                         (long long)elm[0].leaf.base.obj_id,
 300                                         elm[0].leaf.base.rec_type,
 301                                         (long long)elm[0].leaf.base.key,
 302                                         elm[0].leaf.base.localization,
 303                                         r
 304                                 );
 305                         }
 306                         if (r < 0) {
 307                                 error = ENOENT;
 308                                 break;
 309                         }
 310
 311                         /*
 312                          * We support both end-inclusive and
 313                          * end-exclusive searches.
 314                          */
 315                         if (r == 0 &&
 316                            (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 317                                 error = ENOENT;
 318                                 break;
 319                         }
 320
 321                         /*
 322                          * If ITERATE_CHECK is set an unlocked cursor may
 323                          * have been moved to a parent and the iterate can
 324                          * happen upon elements that are not in the requested
 325                          * range.
 326                          */
 327                         if (cursor->flags & HAMMER_CURSOR_ITERATE_CHECK) {
 328                                 s = hammer_btree_cmp(&cursor->key_beg,
 329                                                      &elm->base);
 330                                 if (s > 0) {
 331                                         kprintf("hammer_btree_iterate: "
 332                                                 "DEBUG: Caught parent seek "
 333                                                 "in leaf iteration\n");
 334                                         ++cursor->index;
 335                                         continue;
 336                                 }
 337                         }
 338                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 339
 340                         /*
 341                          * Return the element
 342                          */
 343                         switch(elm->leaf.base.btype) {
 344                         case HAMMER_BTREE_TYPE_RECORD:
 345                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 346                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 347                                         ++cursor->index;
 348                                         continue;
 349                                 }
 350                                 error = 0;
 351                                 break;
 352                         default:
 353                                 error = EINVAL;
 354                                 break;
 355                         }
 356                         if (error)
 357                                 break;
 358                 }
 359                 /*
 360                  * node pointer invalid after loop
 361                  */
 362
 363                 /*
 364                  * Return entry
 365                  */
 366                 if (hammer_debug_btree) {
 367                         int i = cursor->index;
 368                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 369                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 370                                 cursor->node, i,
 371                                 (long long)elm->internal.base.obj_id,
 372                                 elm->internal.base.rec_type,
 373                                 (long long)elm->internal.base.key,
 374                                 elm->internal.base.localization
 375                         );
 376                 }
 377                 return(0);
 378         }
 379         return(error);
 380 }
 381
 382 /*
 383  * We hit an internal element that we could skip as part of a mirroring
 384  * scan.  Calculate the entire range being skipped.
 385  *
 386  * It is important to include any gaps between the parent's left_bound
 387  * and the node's left_bound, and same goes for the right side.
 388  */
 389 static void
 390 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
 391 {
 392         struct hammer_cmirror *cmirror;
 393         hammer_node_ondisk_t ondisk;
 394         hammer_btree_elm_t elm;
 395
 396         ondisk = cursor->node->ondisk;
 397         cmirror = cursor->cmirror;
 398
 399         /*
 400          * Calculate the skipped range
 401          */
 402         elm = &ondisk->elms[cursor->index];
 403         if (cursor->index == 0)
 404                 cmirror->skip_beg = *cursor->left_bound;
 405         else
 406                 cmirror->skip_beg = elm->internal.base;
 407         while (cursor->index < ondisk->count) {
 408                 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
 409                         break;
 410                 ++cursor->index;
 411                 ++elm;
 412         }
 413         if (cursor->index == ondisk->count)
 414                 cmirror->skip_end = *cursor->right_bound;
 415         else
 416                 cmirror->skip_end = elm->internal.base;
 417
 418         /*
 419          * clip the returned result.
 420          */
 421         if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
 422                 cmirror->skip_beg = cursor->key_beg;
 423         if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
 424                 cmirror->skip_end = cursor->key_end;
 425 }
 426
 427 /*
 428  * Iterate in the reverse direction.  This is used by the pruning code to
 429  * avoid overlapping records.
 430  */
 431 int
 432 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
 433 {
 434         hammer_node_ondisk_t node;
 435         hammer_btree_elm_t elm;
 436         int error = 0;
 437         int r;
 438         int s;
 439
 440         /* mirror filtering not supported for reverse iteration */
 441         KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
 442
 443         /*
 444          * Skip past the current record.  For various reasons the cursor
 445          * may end up set to -1 or set to point at the end of the current
 446          * node.  These cases must be addressed.
 447          */
 448         node = cursor->node->ondisk;
 449         if (node == NULL)
 450                 return(ENOENT);
 451         if (cursor->index != -1 &&
 452             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 453                 --cursor->index;
 454         }
 455         if (cursor->index == cursor->node->ondisk->count)
 456                 --cursor->index;
 457
 458         /*
 459          * Loop until an element is found or we are done.
 460          */
 461         for (;;) {
 462                 ++hammer_stats_btree_iterations;
 463                 hammer_flusher_clean_loose_ios(cursor->trans->hmp);
 464
 465                 /*
 466                  * We iterate up the tree and then index over one element
 467                  * while we are at the last element in the current node.
 468                  */
 469                 if (cursor->index == -1) {
 470                         error = hammer_cursor_up(cursor);
 471                         if (error) {
 472                                 cursor->index = 0; /* sanity */
 473                                 break;
 474                         }
 475                         /* reload stale pointer */
 476                         node = cursor->node->ondisk;
 477                         KKASSERT(cursor->index != node->count);
 478                         --cursor->index;
 479                         continue;
 480                 }
 481
 482                 /*
 483                  * Check internal or leaf element.  Determine if the record
 484                  * at the cursor has gone beyond the end of our range.
 485                  *
 486                  * We recurse down through internal nodes.
 487                  */
 488                 KKASSERT(cursor->index != node->count);
 489                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 490                         elm = &node->elms[cursor->index];
 491                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 492                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 493                         if (hammer_debug_btree) {
 494                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 495                                         (long long)cursor->node->node_offset,
 496                                         cursor->index,
 497                                         (long long)elm[0].internal.base.obj_id,
 498                                         elm[0].internal.base.rec_type,
 499                                         (long long)elm[0].internal.base.key,
 500                                         elm[0].internal.base.localization,
 501                                         r
 502                                 );
 503                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 504                                         (long long)cursor->node->node_offset,
 505                                         cursor->index + 1,
 506                                         (long long)elm[1].internal.base.obj_id,
 507                                         elm[1].internal.base.rec_type,
 508                                         (long long)elm[1].internal.base.key,
 509                                         elm[1].internal.base.localization,
 510                                         s
 511                                 );
 512                         }
 513
 514                         if (s >= 0) {
 515                                 error = ENOENT;
 516                                 break;
 517                         }
 518
 519                         /*
 520                          * It shouldn't be possible to be seeked past key_end,
 521                          * even if the cursor got moved to a parent.
 522                          */
 523                         KKASSERT(r >= 0);
 524
 525                         /*
 526                          * Better not be zero
 527                          */
 528                         KKASSERT(elm->internal.subtree_offset != 0);
 529
 530                         error = hammer_cursor_down(cursor);
 531                         if (error)
 532                                 break;
 533                         KKASSERT(cursor->index == 0);
 534                         /* reload stale pointer */
 535                         node = cursor->node->ondisk;
 536
 537                         /* this can assign -1 if the leaf was empty */
 538                         cursor->index = node->count - 1;
 539                         continue;
 540                 } else {
 541                         elm = &node->elms[cursor->index];
 542                         s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
 543                         if (hammer_debug_btree) {
 544                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 545                                         (long long)cursor->node->node_offset,
 546                                         cursor->index,
 547                                         (elm[0].leaf.base.btype ?
 548                                          elm[0].leaf.base.btype : '?'),
 549                                         (long long)elm[0].leaf.base.obj_id,
 550                                         elm[0].leaf.base.rec_type,
 551                                         (long long)elm[0].leaf.base.key,
 552                                         elm[0].leaf.base.localization,
 553                                         s
 554                                 );
 555                         }
 556                         if (s > 0) {
 557                                 error = ENOENT;
 558                                 break;
 559                         }
 560
 561                         /*
 562                          * It shouldn't be possible to be seeked past key_end,
 563                          * even if the cursor got moved to a parent.
 564                          */
 565                         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 566
 567                         /*
 568                          * Return the element
 569                          */
 570                         switch(elm->leaf.base.btype) {
 571                         case HAMMER_BTREE_TYPE_RECORD:
 572                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 573                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 574                                         --cursor->index;
 575                                         continue;
 576                                 }
 577                                 error = 0;
 578                                 break;
 579                         default:
 580                                 error = EINVAL;
 581                                 break;
 582                         }
 583                         if (error)
 584                                 break;
 585                 }
 586                 /*
 587                  * node pointer invalid after loop
 588                  */
 589
 590                 /*
 591                  * Return entry
 592                  */
 593                 if (hammer_debug_btree) {
 594                         int i = cursor->index;
 595                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 596                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 597                                 cursor->node, i,
 598                                 (long long)elm->internal.base.obj_id,
 599                                 elm->internal.base.rec_type,
 600                                 (long long)elm->internal.base.key,
 601                                 elm->internal.base.localization
 602                         );
 603                 }
 604                 return(0);
 605         }
 606         return(error);
 607 }
 608
 609 /*
 610  * Lookup cursor->key_beg.  0 is returned on success, ENOENT if the entry
 611  * could not be found, EDEADLK if inserting and a retry is needed, and a
 612  * fatal error otherwise.  When retrying, the caller must terminate the
 613  * cursor and reinitialize it.  EDEADLK cannot be returned if not inserting.
 614  *
 615  * The cursor is suitably positioned for a deletion on success, and suitably
 616  * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
 617  * specified.
 618  *
 619  * The cursor may begin anywhere, the search will traverse the tree in
 620  * either direction to locate the requested element.
 621  *
 622  * Most of the logic implementing historical searches is handled here.  We
 623  * do an initial lookup with create_tid set to the asof TID.  Due to the
 624  * way records are laid out, a backwards iteration may be required if
 625  * ENOENT is returned to locate the historical record.  Here's the
 626  * problem:
 627  *
 628  * create_tid:    10      15       20
 629  *                   LEAF1   LEAF2
 630  * records:         (11)        (18)
 631  *
 632  * Lets say we want to do a lookup AS-OF timestamp 17.  We will traverse
 633  * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
 634  * not visible and thus causes ENOENT to be returned.  We really need
 635  * to check record 11 in LEAF1.  If it also fails then the search fails
 636  * (e.g. it might represent the range 11-16 and thus still not match our
 637  * AS-OF timestamp of 17).  Note that LEAF1 could be empty, requiring
 638  * further iterations.
 639  *
 640  * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
 641  * and the cursor->create_check TID if an iteration might be needed.
 642  * In the above example create_check would be set to 14.
 643  */
 644 int
 645 hammer_btree_lookup(hammer_cursor_t cursor)
 646 {
 647         int error;
 648
 649         cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
 650         KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
 651                   cursor->trans->sync_lock_refs > 0);
 652         ++hammer_stats_btree_lookups;
 653         if (cursor->flags & HAMMER_CURSOR_ASOF) {
 654                 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
 655                 cursor->key_beg.create_tid = cursor->asof;
 656                 for (;;) {
 657                         cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
 658                         error = btree_search(cursor, 0);
 659                         if (error != ENOENT ||
 660                             (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
 661                                 /*
 662                                  * Stop if no error.
 663                                  * Stop if error other then ENOENT.
 664                                  * Stop if ENOENT and not special case.
 665                                  */
 666                                 break;
 667                         }
 668                         if (hammer_debug_btree) {
 669                                 kprintf("CREATE_CHECK %016llx\n",
 670                                         (long long)cursor->create_check);
 671                         }
 672                         cursor->key_beg.create_tid = cursor->create_check;
 673                         /* loop */
 674                 }
 675         } else {
 676                 error = btree_search(cursor, 0);
 677         }
 678         if (error == 0)
 679                 error = hammer_btree_extract(cursor, cursor->flags);
 680         return(error);
 681 }
 682
 683 /*
 684  * Execute the logic required to start an iteration.  The first record
 685  * located within the specified range is returned and iteration control
 686  * flags are adjusted for successive hammer_btree_iterate() calls.
 687  *
 688  * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
 689  * in a loop without worrying about it.  Higher-level merged searches will
 690  * adjust the flag appropriately.
 691  */
 692 int
 693 hammer_btree_first(hammer_cursor_t cursor)
 694 {
 695         int error;
 696
 697         error = hammer_btree_lookup(cursor);
 698         if (error == ENOENT) {
 699                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 700                 error = hammer_btree_iterate(cursor);
 701         }
 702         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 703         return(error);
 704 }
 705
 706 /*
 707  * Similarly but for an iteration in the reverse direction.
 708  *
 709  * Set ATEDISK when iterating backwards to skip the current entry,
 710  * which after an ENOENT lookup will be pointing beyond our end point.
 711  *
 712  * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
 713  * in a loop without worrying about it.  Higher-level merged searches will
 714  * adjust the flag appropriately.
 715  */
 716 int
 717 hammer_btree_last(hammer_cursor_t cursor)
 718 {
 719         struct hammer_base_elm save;
 720         int error;
 721
 722         save = cursor->key_beg;
 723         cursor->key_beg = cursor->key_end;
 724         error = hammer_btree_lookup(cursor);
 725         cursor->key_beg = save;
 726         if (error == ENOENT ||
 727             (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 728                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 729                 error = hammer_btree_iterate_reverse(cursor);
 730         }
 731         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 732         return(error);
 733 }
 734
 735 /*
 736  * Extract the record and/or data associated with the cursor's current
 737  * position.  Any prior record or data stored in the cursor is replaced.
 738  * The cursor must be positioned at a leaf node.
 739  *
 740  * NOTE: All extractions occur at the leaf of the B-Tree.
 741  */
 742 int
 743 hammer_btree_extract(hammer_cursor_t cursor, int flags)
 744 {
 745         hammer_node_ondisk_t node;
 746         hammer_btree_elm_t elm;
 747         hammer_off_t data_off;
 748         hammer_mount_t hmp;
 749         int32_t data_len;
 750         int error;
 751
 752         /*
 753          * The case where the data reference resolves to the same buffer
 754          * as the record reference must be handled.
 755          */
 756         node = cursor->node->ondisk;
 757         elm = &node->elms[cursor->index];
 758         cursor->data = NULL;
 759         hmp = cursor->node->hmp;
 760
 761         /*
 762          * There is nothing to extract for an internal element.
 763          */
 764         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 765                 return(EINVAL);
 766
 767         /*
 768          * Only record types have data.
 769          */
 770         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 771         cursor->leaf = &elm->leaf;
 772
 773         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 774                 return(0);
 775         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 776                 return(0);
 777         data_off = elm->leaf.data_offset;
 778         data_len = elm->leaf.data_len;
 779         if (data_off == 0)
 780                 return(0);
 781
 782         /*
 783          * Load the data
 784          */
 785         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 786         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 787                                         &error, &cursor->data_buffer);
 788
 789         /*
 790          * Mark the data buffer as not being meta-data if it isn't
 791          * meta-data (sometimes bulk data is accessed via a volume
 792          * block device).
 793          */
 794         if (error == 0) {
 795                 switch(elm->leaf.base.rec_type) {
 796                 case HAMMER_RECTYPE_DATA:
 797                 case HAMMER_RECTYPE_DB:
 798                         hammer_io_notmeta(cursor->data_buffer);
 799                         break;
 800                 default:
 801                         break;
 802                 }
 803         }
 804
 805         /*
 806          * Deal with CRC errors on the extracted data.
 807          */
 808         if (error == 0 &&
 809             hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 810                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 811                         (long long)elm->leaf.data_offset, elm->leaf.data_len);
 812                 if (hammer_debug_critical)
 813                         Debugger("CRC FAILED: DATA");
 814                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 815                         error = EDOM;   /* less critical (mirroring) */
 816                 else
 817                         error = EIO;    /* critical */
 818         }
 819         return(error);
 820 }
 821
 822
 823 /*
 824  * Insert a leaf element into the B-Tree at the current cursor position.
 825  * The cursor is positioned such that the element at and beyond the cursor
 826  * are shifted to make room for the new record.
 827  *
 828  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 829  * flag set and that call must return ENOENT before this function can be
 830  * called.
 831  *
 832  * The caller may depend on the cursor's exclusive lock after return to
 833  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 834  *
 835  * ENOSPC is returned if there is no room to insert a new record.
 836  */
 837 int
 838 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 839                     int *doprop)
 840 {
 841         hammer_node_ondisk_t node;
 842         int i;
 843         int error;
 844
 845         *doprop = 0;
 846         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 847                 return(error);
 848         ++hammer_stats_btree_inserts;
 849
 850         /*
 851          * Insert the element at the leaf node and update the count in the
 852          * parent.  It is possible for parent to be NULL, indicating that
 853          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 854          * possible.  The root inode can never be deleted so the leaf should
 855          * never be empty.
 856          *
 857          * Remember that the right-hand boundary is not included in the
 858          * count.
 859          */
 860         hammer_modify_node_all(cursor->trans, cursor->node);
 861         node = cursor->node->ondisk;
 862         i = cursor->index;
 863         KKASSERT(elm->base.btype != 0);
 864         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 865         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 866         if (i != node->count) {
 867                 bcopy(&node->elms[i], &node->elms[i+1],
 868                       (node->count - i) * sizeof(*elm));
 869         }
 870         node->elms[i].leaf = *elm;
 871         ++node->count;
 872         hammer_cursor_inserted_element(cursor->node, i);
 873
 874         /*
 875          * Update the leaf node's aggregate mirror_tid for mirroring
 876          * support.
 877          */
 878         if (node->mirror_tid < elm->base.delete_tid) {
 879                 node->mirror_tid = elm->base.delete_tid;
 880                 *doprop = 1;
 881         }
 882         if (node->mirror_tid < elm->base.create_tid) {
 883                 node->mirror_tid = elm->base.create_tid;
 884                 *doprop = 1;
 885         }
 886         hammer_modify_node_done(cursor->node);
 887
 888         /*
 889          * Debugging sanity checks.
 890          */
 891         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 892         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 893         if (i) {
 894                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 895         }
 896         if (i != node->count - 1)
 897                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 898
 899         return(0);
 900 }
 901
 902 /*
 903  * Delete a record from the B-Tree at the current cursor position.
 904  * The cursor is positioned such that the current element is the one
 905  * to be deleted.
 906  *
 907  * On return the cursor will be positioned after the deleted element and
 908  * MAY point to an internal node.  It will be suitable for the continuation
 909  * of an iteration but not for an insertion or deletion.
 910  *
 911  * Deletions will attempt to partially rebalance the B-Tree in an upward
 912  * direction, but will terminate rather then deadlock.  Empty internal nodes
 913  * are never allowed by a deletion which deadlocks may end up giving us an
 914  * empty leaf.  The pruner will clean up and rebalance the tree.
 915  *
 916  * This function can return EDEADLK, requiring the caller to retry the
 917  * operation after clearing the deadlock.
 918  */
 919 int
 920 hammer_btree_delete(hammer_cursor_t cursor)
 921 {
 922         hammer_node_ondisk_t ondisk;
 923         hammer_node_t node;
 924         hammer_node_t parent;
 925         int error;
 926         int i;
 927
 928         KKASSERT (cursor->trans->sync_lock_refs > 0);
 929         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 930                 return(error);
 931         ++hammer_stats_btree_deletes;
 932
 933         /*
 934          * Delete the element from the leaf node.
 935          *
 936          * Remember that leaf nodes do not have boundaries.
 937          */
 938         node = cursor->node;
 939         ondisk = node->ondisk;
 940         i = cursor->index;
 941
 942         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 943         KKASSERT(i >= 0 && i < ondisk->count);
 944         hammer_modify_node_all(cursor->trans, node);
 945         if (i + 1 != ondisk->count) {
 946                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 947                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 948         }
 949         --ondisk->count;
 950         hammer_modify_node_done(node);
 951         hammer_cursor_deleted_element(node, i);
 952
 953         /*
 954          * Validate local parent
 955          */
 956         if (ondisk->parent) {
 957                 parent = cursor->parent;
 958
 959                 KKASSERT(parent != NULL);
 960                 KKASSERT(parent->node_offset == ondisk->parent);
 961         }
 962
 963         /*
 964          * If the leaf becomes empty it must be detached from the parent,
 965          * potentially recursing through to the filesystem root.
 966          *
 967          * This may reposition the cursor at one of the parent's of the
 968          * current node.
 969          *
 970          * Ignore deadlock errors, that simply means that btree_remove
 971          * was unable to recurse and had to leave us with an empty leaf.
 972          */
 973         KKASSERT(cursor->index <= ondisk->count);
 974         if (ondisk->count == 0) {
 975                 error = btree_remove(cursor);
 976                 if (error == EDEADLK)
 977                         error = 0;
 978         } else {
 979                 error = 0;
 980         }
 981         KKASSERT(cursor->parent == NULL ||
 982                  cursor->parent_index < cursor->parent->ondisk->count);
 983         return(error);
 984 }
 985
 986 /*
 987  * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
 988  *
 989  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
 990  *
 991  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
 992  * iterates up the tree as necessary to properly position itself prior to
 993  * actually doing the sarch.
 994  *
 995  * INSERTIONS: The search will split full nodes and leaves on its way down
 996  * and guarentee that the leaf it ends up on is not full.  If we run out
 997  * of space the search continues to the leaf (to position the cursor for
 998  * the spike), but ENOSPC is returned.
 999  *
1000  * The search is only guarenteed to end up on a leaf if an error code of 0
1001  * is returned, or if inserting and an error code of ENOENT is returned.
1002  * Otherwise it can stop at an internal node.  On success a search returns
1003  * a leaf node.
1004  *
1005  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
1006  * filesystem, and it is not simple code.  Please note the following facts:
1007  *
1008  * - Internal node recursions have a boundary on the left AND right.  The
1009  *   right boundary is non-inclusive.  The create_tid is a generic part
1010  *   of the key for internal nodes.
1011  *
1012  * - Leaf nodes contain terminal elements only now.
1013  *
1014  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
1015  *   historical search.  ASOF and INSERT are mutually exclusive.  When
1016  *   doing an as-of lookup btree_search() checks for a right-edge boundary
1017  *   case.  If while recursing down the left-edge differs from the key
1018  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
1019  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
1020  *   The iteration backwards because as-of searches can wind up going
1021  *   down the wrong branch of the B-Tree.
1022  */
1023 static
1024 int
1025 btree_search(hammer_cursor_t cursor, int flags)
1026 {
1027         hammer_node_ondisk_t node;
1028         hammer_btree_elm_t elm;
1029         int error;
1030         int enospc = 0;
1031         int i;
1032         int r;
1033         int s;
1034
1035         flags |= cursor->flags;
1036         ++hammer_stats_btree_searches;
1037
1038         if (hammer_debug_btree) {
1039                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
1040                         (long long)cursor->node->node_offset,
1041                         cursor->index,
1042                         (long long)cursor->key_beg.obj_id,
1043                         cursor->key_beg.rec_type,
1044                         (long long)cursor->key_beg.key,
1045                         (long long)cursor->key_beg.create_tid,
1046                         cursor->key_beg.localization,
1047                         curthread
1048                 );
1049                 if (cursor->parent)
1050                     kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
1051                         (long long)cursor->parent->node_offset,
1052                         cursor->parent_index,
1053                         (long long)cursor->left_bound->obj_id,
1054                         (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
1055                         (long long)cursor->right_bound->obj_id,
1056                         (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
1057                         cursor->left_bound,
1058                         &cursor->parent->ondisk->elms[cursor->parent_index],
1059                         cursor->right_bound,
1060                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
1061                     );
1062         }
1063
1064         /*
1065          * Move our cursor up the tree until we find a node whos range covers
1066          * the key we are trying to locate.
1067          *
1068          * The left bound is inclusive, the right bound is non-inclusive.
1069          * It is ok to cursor up too far.
1070          */
1071         for (;;) {
1072                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
1073                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
1074                 if (r >= 0 && s < 0)
1075                         break;
1076                 KKASSERT(cursor->parent);
1077                 ++hammer_stats_btree_iterations;
1078                 error = hammer_cursor_up(cursor);
1079                 if (error)
1080                         goto done;
1081         }
1082
1083         /*
1084          * The delete-checks below are based on node, not parent.  Set the
1085          * initial delete-check based on the parent.
1086          */
1087         if (r == 1) {
1088                 KKASSERT(cursor->left_bound->create_tid != 1);
1089                 cursor->create_check = cursor->left_bound->create_tid - 1;
1090                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1091         }
1092
1093         /*
1094          * We better have ended up with a node somewhere.
1095          */
1096         KKASSERT(cursor->node != NULL);
1097
1098         /*
1099          * If we are inserting we can't start at a full node if the parent
1100          * is also full (because there is no way to split the node),
1101          * continue running up the tree until the requirement is satisfied
1102          * or we hit the root of the filesystem.
1103          *
1104          * (If inserting we aren't doing an as-of search so we don't have
1105          *  to worry about create_check).
1106          */
1107         while ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1108                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
1109                         if (btree_node_is_full(cursor->node->ondisk) == 0)
1110                                 break;
1111                 } else {
1112                         if (btree_node_is_full(cursor->node->ondisk) ==0)
1113                                 break;
1114                 }
1115                 if (cursor->node->ondisk->parent == 0 ||
1116                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1117                         break;
1118                 }
1119                 ++hammer_stats_btree_iterations;
1120                 error = hammer_cursor_up(cursor);
1121                 /* node may have become stale */
1122                 if (error)
1123                         goto done;
1124         }
1125
1126         /*
1127          * Push down through internal nodes to locate the requested key.
1128          */
1129         node = cursor->node->ondisk;
1130         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1131                 /*
1132                  * Scan the node to find the subtree index to push down into.
1133                  * We go one-past, then back-up.
1134                  *
1135                  * We must proactively remove deleted elements which may
1136                  * have been left over from a deadlocked btree_remove().
1137                  *
1138                  * The left and right boundaries are included in the loop
1139                  * in order to detect edge cases.
1140                  *
1141                  * If the separator only differs by create_tid (r == 1)
1142                  * and we are doing an as-of search, we may end up going
1143                  * down a branch to the left of the one containing the
1144                  * desired key.  This requires numerous special cases.
1145                  */
1146                 ++hammer_stats_btree_iterations;
1147                 if (hammer_debug_btree) {
1148                         kprintf("SEARCH-I %016llx count=%d\n",
1149                                 (long long)cursor->node->node_offset,
1150                                 node->count);
1151                 }
1152
1153                 /*
1154                  * Try to shortcut the search before dropping into the
1155                  * linear loop.  Locate the first node where r <= 1.
1156                  */
1157                 i = hammer_btree_search_node(&cursor->key_beg, node);
1158                 while (i <= node->count) {
1159                         ++hammer_stats_btree_elements;
1160                         elm = &node->elms[i];
1161                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1162                         if (hammer_debug_btree > 2) {
1163                                 kprintf(" IELM %p %d r=%d\n",
1164                                         &node->elms[i], i, r);
1165                         }
1166                         if (r < 0)
1167                                 break;
1168                         if (r == 1) {
1169                                 KKASSERT(elm->base.create_tid != 1);
1170                                 cursor->create_check = elm->base.create_tid - 1;
1171                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1172                         }
1173                         ++i;
1174                 }
1175                 if (hammer_debug_btree) {
1176                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1177                                 i, node->count, r);
1178                 }
1179
1180                 /*
1181                  * These cases occur when the parent's idea of the boundary
1182                  * is wider then the child's idea of the boundary, and
1183                  * require special handling.  If not inserting we can
1184                  * terminate the search early for these cases but the
1185                  * child's boundaries cannot be unconditionally modified.
1186                  */
1187                 if (i == 0) {
1188                         /*
1189                          * If i == 0 the search terminated to the LEFT of the
1190                          * left_boundary but to the RIGHT of the parent's left
1191                          * boundary.
1192                          */
1193                         u_int8_t save;
1194
1195                         elm = &node->elms[0];
1196
1197                         /*
1198                          * If we aren't inserting we can stop here.
1199                          */
1200                         if ((flags & (HAMMER_CURSOR_INSERT |
1201                                       HAMMER_CURSOR_PRUNING)) == 0) {
1202                                 cursor->index = 0;
1203                                 return(ENOENT);
1204                         }
1205
1206                         /*
1207                          * Correct a left-hand boundary mismatch.
1208                          *
1209                          * We can only do this if we can upgrade the lock,
1210                          * and synchronized as a background cursor (i.e.
1211                          * inserting or pruning).
1212                          *
1213                          * WARNING: We can only do this if inserting, i.e.
1214                          * we are running on the backend.
1215                          */
1216                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1217                                 return(error);
1218                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1219                         hammer_modify_node_field(cursor->trans, cursor->node,
1220                                                  elms[0]);
1221                         save = node->elms[0].base.btype;
1222                         node->elms[0].base = *cursor->left_bound;
1223                         node->elms[0].base.btype = save;
1224                         hammer_modify_node_done(cursor->node);
1225                 } else if (i == node->count + 1) {
1226                         /*
1227                          * If i == node->count + 1 the search terminated to
1228                          * the RIGHT of the right boundary but to the LEFT
1229                          * of the parent's right boundary.  If we aren't
1230                          * inserting we can stop here.
1231                          *
1232                          * Note that the last element in this case is
1233                          * elms[i-2] prior to adjustments to 'i'.
1234                          */
1235                         --i;
1236                         if ((flags & (HAMMER_CURSOR_INSERT |
1237                                       HAMMER_CURSOR_PRUNING)) == 0) {
1238                                 cursor->index = i;
1239                                 return (ENOENT);
1240                         }
1241
1242                         /*
1243                          * Correct a right-hand boundary mismatch.
1244                          * (actual push-down record is i-2 prior to
1245                          * adjustments to i).
1246                          *
1247                          * We can only do this if we can upgrade the lock,
1248                          * and synchronized as a background cursor (i.e.
1249                          * inserting or pruning).
1250                          *
1251                          * WARNING: We can only do this if inserting, i.e.
1252                          * we are running on the backend.
1253                          */
1254                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1255                                 return(error);
1256                         elm = &node->elms[i];
1257                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1258                         hammer_modify_node(cursor->trans, cursor->node,
1259                                            &elm->base, sizeof(elm->base));
1260                         elm->base = *cursor->right_bound;
1261                         hammer_modify_node_done(cursor->node);
1262                         --i;
1263                 } else {
1264                         /*
1265                          * The push-down index is now i - 1.  If we had
1266                          * terminated on the right boundary this will point
1267                          * us at the last element.
1268                          */
1269                         --i;
1270                 }
1271                 cursor->index = i;
1272                 elm = &node->elms[i];
1273
1274                 if (hammer_debug_btree) {
1275                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1276                                 "key=%016llx cre=%016llx lo=%02x\n",
1277                                 (long long)cursor->node->node_offset,
1278                                 i,
1279                                 (long long)elm->internal.base.obj_id,
1280                                 elm->internal.base.rec_type,
1281                                 (long long)elm->internal.base.key,
1282                                 (long long)elm->internal.base.create_tid,
1283                                 elm->internal.base.localization
1284                         );
1285                 }
1286
1287                 /*
1288                  * We better have a valid subtree offset.
1289                  */
1290                 KKASSERT(elm->internal.subtree_offset != 0);
1291
1292                 /*
1293                  * Handle insertion and deletion requirements.
1294                  *
1295                  * If inserting split full nodes.  The split code will
1296                  * adjust cursor->node and cursor->index if the current
1297                  * index winds up in the new node.
1298                  *
1299                  * If inserting and a left or right edge case was detected,
1300                  * we cannot correct the left or right boundary and must
1301                  * prepend and append an empty leaf node in order to make
1302                  * the boundary correction.
1303                  *
1304                  * If we run out of space we set enospc and continue on
1305                  * to a leaf to provide the spike code with a good point
1306                  * of entry.
1307                  */
1308                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1309                         if (btree_node_is_full(node)) {
1310                                 error = btree_split_internal(cursor);
1311                                 if (error) {
1312                                         if (error != ENOSPC)
1313                                                 goto done;
1314                                         enospc = 1;
1315                                 }
1316                                 /*
1317                                  * reload stale pointers
1318                                  */
1319                                 i = cursor->index;
1320                                 node = cursor->node->ondisk;
1321                         }
1322                 }
1323
1324                 /*
1325                  * Push down (push into new node, existing node becomes
1326                  * the parent) and continue the search.
1327                  */
1328                 error = hammer_cursor_down(cursor);
1329                 /* node may have become stale */
1330                 if (error)
1331                         goto done;
1332                 node = cursor->node->ondisk;
1333         }
1334
1335         /*
1336          * We are at a leaf, do a linear search of the key array.
1337          *
1338          * On success the index is set to the matching element and 0
1339          * is returned.
1340          *
1341          * On failure the index is set to the insertion point and ENOENT
1342          * is returned.
1343          *
1344          * Boundaries are not stored in leaf nodes, so the index can wind
1345          * up to the left of element 0 (index == 0) or past the end of
1346          * the array (index == node->count).  It is also possible that the
1347          * leaf might be empty.
1348          */
1349         ++hammer_stats_btree_iterations;
1350         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1351         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1352         if (hammer_debug_btree) {
1353                 kprintf("SEARCH-L %016llx count=%d\n",
1354                         (long long)cursor->node->node_offset,
1355                         node->count);
1356         }
1357
1358         /*
1359          * Try to shortcut the search before dropping into the
1360          * linear loop.  Locate the first node where r <= 1.
1361          */
1362         i = hammer_btree_search_node(&cursor->key_beg, node);
1363         while (i < node->count) {
1364                 ++hammer_stats_btree_elements;
1365                 elm = &node->elms[i];
1366
1367                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1368
1369                 if (hammer_debug_btree > 1)
1370                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1371
1372                 /*
1373                  * We are at a record element.  Stop if we've flipped past
1374                  * key_beg, not counting the create_tid test.  Allow the
1375                  * r == 1 case (key_beg > element but differs only by its
1376                  * create_tid) to fall through to the AS-OF check.
1377                  */
1378                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1379
1380                 if (r < 0)
1381                         goto failed;
1382                 if (r > 1) {
1383                         ++i;
1384                         continue;
1385                 }
1386
1387                 /*
1388                  * Check our as-of timestamp against the element.
1389                  */
1390                 if (flags & HAMMER_CURSOR_ASOF) {
1391                         if (hammer_btree_chkts(cursor->asof,
1392                                                &node->elms[i].base) != 0) {
1393                                 ++i;
1394                                 continue;
1395                         }
1396                         /* success */
1397                 } else {
1398                         if (r > 0) {    /* can only be +1 */
1399                                 ++i;
1400                                 continue;
1401                         }
1402                         /* success */
1403                 }
1404                 cursor->index = i;
1405                 error = 0;
1406                 if (hammer_debug_btree) {
1407                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1408                                 (long long)cursor->node->node_offset, i);
1409                 }
1410                 goto done;
1411         }
1412
1413         /*
1414          * The search of the leaf node failed.  i is the insertion point.
1415          */
1416 failed:
1417         if (hammer_debug_btree) {
1418                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1419                         (long long)cursor->node->node_offset, i);
1420         }
1421
1422         /*
1423          * No exact match was found, i is now at the insertion point.
1424          *
1425          * If inserting split a full leaf before returning.  This
1426          * may have the side effect of adjusting cursor->node and
1427          * cursor->index.
1428          */
1429         cursor->index = i;
1430         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1431              btree_node_is_full(node)) {
1432                 error = btree_split_leaf(cursor);
1433                 if (error) {
1434                         if (error != ENOSPC)
1435                                 goto done;
1436                         enospc = 1;
1437                 }
1438                 /*
1439                  * reload stale pointers
1440                  */
1441                 /* NOT USED
1442                 i = cursor->index;
1443                 node = &cursor->node->internal;
1444                 */
1445         }
1446
1447         /*
1448          * We reached a leaf but did not find the key we were looking for.
1449          * If this is an insert we will be properly positioned for an insert
1450          * (ENOENT) or spike (ENOSPC) operation.
1451          */
1452         error = enospc ? ENOSPC : ENOENT;
1453 done:
1454         return(error);
1455 }
1456
1457 /*
1458  * Heuristical search for the first element whos comparison is <= 1.  May
1459  * return an index whos compare result is > 1 but may only return an index
1460  * whos compare result is <= 1 if it is the first element with that result.
1461  */
1462 int
1463 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1464 {
1465         int b;
1466         int s;
1467         int i;
1468         int r;
1469
1470         /*
1471          * Don't bother if the node does not have very many elements
1472          */
1473         b = 0;
1474         s = node->count;
1475         while (s - b > 4) {
1476                 i = b + (s - b) / 2;
1477                 ++hammer_stats_btree_elements;
1478                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1479                 if (r <= 1) {
1480                         s = i;
1481                 } else {
1482                         b = i;
1483                 }
1484         }
1485         return(b);
1486 }
1487
1488
1489 /************************************************************************
1490  *                         SPLITTING AND MERGING                        *
1491  ************************************************************************
1492  *
1493  * These routines do all the dirty work required to split and merge nodes.
1494  */
1495
1496 /*
1497  * Split an internal node into two nodes and move the separator at the split
1498  * point to the parent.
1499  *
1500  * (cursor->node, cursor->index) indicates the element the caller intends
1501  * to push into.  We will adjust node and index if that element winds
1502  * up in the split node.
1503  *
1504  * If we are at the root of the filesystem a new root must be created with
1505  * two elements, one pointing to the original root and one pointing to the
1506  * newly allocated split node.
1507  */
1508 static
1509 int
1510 btree_split_internal(hammer_cursor_t cursor)
1511 {
1512         hammer_node_ondisk_t ondisk;
1513         hammer_node_t node;
1514         hammer_node_t parent;
1515         hammer_node_t new_node;
1516         hammer_btree_elm_t elm;
1517         hammer_btree_elm_t parent_elm;
1518         struct hammer_node_lock lockroot;
1519         hammer_mount_t hmp = cursor->trans->hmp;
1520         hammer_off_t hint;
1521         int parent_index;
1522         int made_root;
1523         int split;
1524         int error;
1525         int i;
1526         const int esize = sizeof(*elm);
1527
1528         hammer_node_lock_init(&lockroot, cursor->node);
1529         error = hammer_btree_lock_children(cursor, 1, &lockroot);
1530         if (error)
1531                 goto done;
1532         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1533                 goto done;
1534         ++hammer_stats_btree_splits;
1535
1536         /*
1537          * Calculate the split point.  If the insertion point is at the
1538          * end of the leaf we adjust the split point significantly to the
1539          * right to try to optimize node fill and flag it.  If we hit
1540          * that same leaf again our heuristic failed and we don't try
1541          * to optimize node fill (it could lead to a degenerate case).
1542          */
1543         node = cursor->node;
1544         ondisk = node->ondisk;
1545         KKASSERT(ondisk->count > 4);
1546         if (cursor->index == ondisk->count &&
1547             (node->flags & HAMMER_NODE_NONLINEAR) == 0) {
1548                 split = (ondisk->count + 1) * 3 / 4;
1549                 node->flags |= HAMMER_NODE_NONLINEAR;
1550         } else {
1551                 /*
1552                  * We are splitting but elms[split] will be promoted to
1553                  * the parent, leaving the right hand node with one less
1554                  * element.  If the insertion point will be on the
1555                  * left-hand side adjust the split point to give the
1556                  * right hand side one additional node.
1557                  */
1558                 split = (ondisk->count + 1) / 2;
1559                 if (cursor->index <= split)
1560                         --split;
1561         }
1562
1563         /*
1564          * If we are at the root of the filesystem, create a new root node
1565          * with 1 element and split normally.  Avoid making major
1566          * modifications until we know the whole operation will work.
1567          */
1568         if (ondisk->parent == 0) {
1569                 parent = hammer_alloc_btree(cursor->trans, node->node_offset,
1570                                             &error);
1571                 if (parent == NULL)
1572                         goto done;
1573                 hammer_lock_ex(&parent->lock);
1574                 hammer_modify_node_noundo(cursor->trans, parent);
1575                 ondisk = parent->ondisk;
1576                 ondisk->count = 1;
1577                 ondisk->parent = 0;
1578                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1579                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1580                 ondisk->elms[0].base = hmp->root_btree_beg;
1581                 ondisk->elms[0].base.btype = node->ondisk->type;
1582                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1583                 ondisk->elms[1].base = hmp->root_btree_end;
1584                 hammer_modify_node_done(parent);
1585                 /* ondisk->elms[1].base.btype - not used */
1586                 made_root = 1;
1587                 parent_index = 0;       /* index of current node in parent */
1588         } else {
1589                 made_root = 0;
1590                 parent = cursor->parent;
1591                 parent_index = cursor->parent_index;
1592         }
1593
1594         /*
1595          * Calculate a hint for the allocation of the new B-Tree node.
1596          * The most likely expansion is coming from the insertion point
1597          * at cursor->index, so try to localize the allocation of our
1598          * new node to accomodate that sub-tree.
1599          *
1600          * Use the right-most sub-tree when expandinging on the right edge.
1601          * This is a very common case when copying a directory tree.
1602          */
1603         if (cursor->index == ondisk->count)
1604                 hint = ondisk->elms[cursor->index - 1].internal.subtree_offset;
1605         else
1606                 hint = ondisk->elms[cursor->index].internal.subtree_offset;
1607
1608         /*
1609          * Split node into new_node at the split point.
1610          *
1611          *  B O O O P N N B     <-- P = node->elms[split] (index 4)
1612          *   0 1 2 3 4 5 6      <-- subtree indices
1613          *
1614          *       x x P x x
1615          *        s S S s
1616          *         /   \
1617          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1618          *   0 1 2 3      4 5 6
1619          */
1620         new_node = hammer_alloc_btree(cursor->trans, hint, &error);
1621         if (new_node == NULL) {
1622                 if (made_root) {
1623                         hammer_unlock(&parent->lock);
1624                         hammer_delete_node(cursor->trans, parent);
1625                         hammer_rel_node(parent);
1626                 }
1627                 goto done;
1628         }
1629         hammer_lock_ex(&new_node->lock);
1630
1631         /*
1632          * Create the new node.  P becomes the left-hand boundary in the
1633          * new node.  Copy the right-hand boundary as well.
1634          *
1635          * elm is the new separator.
1636          */
1637         hammer_modify_node_noundo(cursor->trans, new_node);
1638         hammer_modify_node_all(cursor->trans, node);
1639         ondisk = node->ondisk;
1640         elm = &ondisk->elms[split];
1641         bcopy(elm, &new_node->ondisk->elms[0],
1642               (ondisk->count - split + 1) * esize);
1643         new_node->ondisk->count = ondisk->count - split;
1644         new_node->ondisk->parent = parent->node_offset;
1645         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1646         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1647         KKASSERT(ondisk->type == new_node->ondisk->type);
1648         hammer_cursor_split_node(node, new_node, split);
1649
1650         /*
1651          * Cleanup the original node.  Elm (P) becomes the new boundary,
1652          * its subtree_offset was moved to the new node.  If we had created
1653          * a new root its parent pointer may have changed.
1654          */
1655         elm->internal.subtree_offset = 0;
1656         ondisk->count = split;
1657
1658         /*
1659          * Insert the separator into the parent, fixup the parent's
1660          * reference to the original node, and reference the new node.
1661          * The separator is P.
1662          *
1663          * Remember that base.count does not include the right-hand boundary.
1664          */
1665         hammer_modify_node_all(cursor->trans, parent);
1666         ondisk = parent->ondisk;
1667         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1668         parent_elm = &ondisk->elms[parent_index+1];
1669         bcopy(parent_elm, parent_elm + 1,
1670               (ondisk->count - parent_index) * esize);
1671         parent_elm->internal.base = elm->base;  /* separator P */
1672         parent_elm->internal.base.btype = new_node->ondisk->type;
1673         parent_elm->internal.subtree_offset = new_node->node_offset;
1674         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1675         ++ondisk->count;
1676         hammer_modify_node_done(parent);
1677         hammer_cursor_inserted_element(parent, parent_index + 1);
1678
1679         /*
1680          * The children of new_node need their parent pointer set to new_node.
1681          * The children have already been locked by
1682          * hammer_btree_lock_children().
1683          */
1684         for (i = 0; i < new_node->ondisk->count; ++i) {
1685                 elm = &new_node->ondisk->elms[i];
1686                 error = btree_set_parent(cursor->trans, new_node, elm);
1687                 if (error) {
1688                         panic("btree_split_internal: btree-fixup problem");
1689                 }
1690         }
1691         hammer_modify_node_done(new_node);
1692
1693         /*
1694          * The filesystem's root B-Tree pointer may have to be updated.
1695          */
1696         if (made_root) {
1697                 hammer_volume_t volume;
1698
1699                 volume = hammer_get_root_volume(hmp, &error);
1700                 KKASSERT(error == 0);
1701
1702                 hammer_modify_volume_field(cursor->trans, volume,
1703                                            vol0_btree_root);
1704                 volume->ondisk->vol0_btree_root = parent->node_offset;
1705                 hammer_modify_volume_done(volume);
1706                 node->ondisk->parent = parent->node_offset;
1707                 if (cursor->parent) {
1708                         hammer_unlock(&cursor->parent->lock);
1709                         hammer_rel_node(cursor->parent);
1710                 }
1711                 cursor->parent = parent;        /* lock'd and ref'd */
1712                 hammer_rel_volume(volume, 0);
1713         }
1714         hammer_modify_node_done(node);
1715
1716         /*
1717          * Ok, now adjust the cursor depending on which element the original
1718          * index was pointing at.  If we are >= the split point the push node
1719          * is now in the new node.
1720          *
1721          * NOTE: If we are at the split point itself we cannot stay with the
1722          * original node because the push index will point at the right-hand
1723          * boundary, which is illegal.
1724          *
1725          * NOTE: The cursor's parent or parent_index must be adjusted for
1726          * the case where a new parent (new root) was created, and the case
1727          * where the cursor is now pointing at the split node.
1728          */
1729         if (cursor->index >= split) {
1730                 cursor->parent_index = parent_index + 1;
1731                 cursor->index -= split;
1732                 hammer_unlock(&cursor->node->lock);
1733                 hammer_rel_node(cursor->node);
1734                 cursor->node = new_node;        /* locked and ref'd */
1735         } else {
1736                 cursor->parent_index = parent_index;
1737                 hammer_unlock(&new_node->lock);
1738                 hammer_rel_node(new_node);
1739         }
1740
1741         /*
1742          * Fixup left and right bounds
1743          */
1744         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1745         cursor->left_bound = &parent_elm[0].internal.base;
1746         cursor->right_bound = &parent_elm[1].internal.base;
1747         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1748                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1749         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1750                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1751
1752 done:
1753         hammer_btree_unlock_children(cursor, &lockroot);
1754         hammer_cursor_downgrade(cursor);
1755         return (error);
1756 }
1757
1758 /*
1759  * Same as the above, but splits a full leaf node.
1760  *
1761  * This function
1762  */
1763 static
1764 int
1765 btree_split_leaf(hammer_cursor_t cursor)
1766 {
1767         hammer_node_ondisk_t ondisk;
1768         hammer_node_t parent;
1769         hammer_node_t leaf;
1770         hammer_mount_t hmp;
1771         hammer_node_t new_leaf;
1772         hammer_btree_elm_t elm;
1773         hammer_btree_elm_t parent_elm;
1774         hammer_base_elm_t mid_boundary;
1775         hammer_off_t hint;
1776         int parent_index;
1777         int made_root;
1778         int split;
1779         int error;
1780         const size_t esize = sizeof(*elm);
1781
1782         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1783                 return(error);
1784         ++hammer_stats_btree_splits;
1785
1786         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1787                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1788         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1789                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1790
1791         /*
1792          * Calculate the split point.  If the insertion point is at the
1793          * end of the leaf we adjust the split point significantly to the
1794          * right to try to optimize node fill and flag it.  If we hit
1795          * that same leaf again our heuristic failed and we don't try
1796          * to optimize node fill (it could lead to a degenerate case).
1797          *
1798          * Spikes are made up of two leaf elements which cannot be
1799          * safely split.
1800          */
1801         leaf = cursor->node;
1802         ondisk = leaf->ondisk;
1803         KKASSERT(ondisk->count > 4);
1804         if (cursor->index == ondisk->count &&
1805             (leaf->flags & HAMMER_NODE_NONLINEAR) == 0) {
1806                 split = (ondisk->count + 1) * 3 / 4;
1807                 leaf->flags |= HAMMER_NODE_NONLINEAR;
1808         } else {
1809                 split = (ondisk->count + 1) / 2;
1810         }
1811
1812 #if 0
1813         /*
1814          * If the insertion point is at the split point shift the
1815          * split point left so we don't have to worry about
1816          */
1817         if (cursor->index == split)
1818                 --split;
1819 #endif
1820         KKASSERT(split > 0 && split < ondisk->count);
1821
1822         error = 0;
1823         hmp = leaf->hmp;
1824
1825         elm = &ondisk->elms[split];
1826
1827         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1828         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1829         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1830         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1831
1832         /*
1833          * If we are at the root of the tree, create a new root node with
1834          * 1 element and split normally.  Avoid making major modifications
1835          * until we know the whole operation will work.
1836          */
1837         if (ondisk->parent == 0) {
1838                 parent = hammer_alloc_btree(cursor->trans, leaf->node_offset,
1839                                             &error);
1840                 if (parent == NULL)
1841                         goto done;
1842                 hammer_lock_ex(&parent->lock);
1843                 hammer_modify_node_noundo(cursor->trans, parent);
1844                 ondisk = parent->ondisk;
1845                 ondisk->count = 1;
1846                 ondisk->parent = 0;
1847                 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1848                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1849                 ondisk->elms[0].base = hmp->root_btree_beg;
1850                 ondisk->elms[0].base.btype = leaf->ondisk->type;
1851                 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1852                 ondisk->elms[1].base = hmp->root_btree_end;
1853                 /* ondisk->elms[1].base.btype = not used */
1854                 hammer_modify_node_done(parent);
1855                 made_root = 1;
1856                 parent_index = 0;       /* insertion point in parent */
1857         } else {
1858                 made_root = 0;
1859                 parent = cursor->parent;
1860                 parent_index = cursor->parent_index;
1861         }
1862
1863         /*
1864          * Calculate a hint for the allocation of the new B-Tree leaf node.
1865          * For now just try to localize it within the same bigblock as
1866          * the current leaf.
1867          *
1868          * If the insertion point is at the end of the leaf we recognize a
1869          * likely append sequence of some sort (data, meta-data, inodes,
1870          * whatever).  Set the hint to zero to allocate out of linear space
1871          * instead of trying to completely fill previously hinted space.
1872          *
1873          * This also sets the stage for recursive splits to localize using
1874          * the new space.
1875          */
1876         ondisk = leaf->ondisk;
1877         if (cursor->index == ondisk->count)
1878                 hint = 0;
1879         else
1880                 hint = leaf->node_offset;
1881
1882         /*
1883          * Split leaf into new_leaf at the split point.  Select a separator
1884          * value in-between the two leafs but with a bent towards the right
1885          * leaf since comparisons use an 'elm >= separator' inequality.
1886          *
1887          *  L L L L L L L L
1888          *
1889          *       x x P x x
1890          *        s S S s
1891          *         /   \
1892          *  L L L L     L L L L
1893          */
1894         new_leaf = hammer_alloc_btree(cursor->trans, hint, &error);
1895         if (new_leaf == NULL) {
1896                 if (made_root) {
1897                         hammer_unlock(&parent->lock);
1898                         hammer_delete_node(cursor->trans, parent);
1899                         hammer_rel_node(parent);
1900                 }
1901                 goto done;
1902         }
1903         hammer_lock_ex(&new_leaf->lock);
1904
1905         /*
1906          * Create the new node and copy the leaf elements from the split
1907          * point on to the new node.
1908          */
1909         hammer_modify_node_all(cursor->trans, leaf);
1910         hammer_modify_node_noundo(cursor->trans, new_leaf);
1911         ondisk = leaf->ondisk;
1912         elm = &ondisk->elms[split];
1913         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1914         new_leaf->ondisk->count = ondisk->count - split;
1915         new_leaf->ondisk->parent = parent->node_offset;
1916         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1917         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1918         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1919         hammer_modify_node_done(new_leaf);
1920         hammer_cursor_split_node(leaf, new_leaf, split);
1921
1922         /*
1923          * Cleanup the original node.  Because this is a leaf node and
1924          * leaf nodes do not have a right-hand boundary, there
1925          * aren't any special edge cases to clean up.  We just fixup the
1926          * count.
1927          */
1928         ondisk->count = split;
1929
1930         /*
1931          * Insert the separator into the parent, fixup the parent's
1932          * reference to the original node, and reference the new node.
1933          * The separator is P.
1934          *
1935          * Remember that base.count does not include the right-hand boundary.
1936          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1937          */
1938         hammer_modify_node_all(cursor->trans, parent);
1939         ondisk = parent->ondisk;
1940         KKASSERT(split != 0);
1941         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1942         parent_elm = &ondisk->elms[parent_index+1];
1943         bcopy(parent_elm, parent_elm + 1,
1944               (ondisk->count - parent_index) * esize);
1945
1946         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1947         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1948         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1949         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1950         mid_boundary = &parent_elm->base;
1951         ++ondisk->count;
1952         hammer_modify_node_done(parent);
1953         hammer_cursor_inserted_element(parent, parent_index + 1);
1954
1955         /*
1956          * The filesystem's root B-Tree pointer may have to be updated.
1957          */
1958         if (made_root) {
1959                 hammer_volume_t volume;
1960
1961                 volume = hammer_get_root_volume(hmp, &error);
1962                 KKASSERT(error == 0);
1963
1964                 hammer_modify_volume_field(cursor->trans, volume,
1965                                            vol0_btree_root);
1966                 volume->ondisk->vol0_btree_root = parent->node_offset;
1967                 hammer_modify_volume_done(volume);
1968                 leaf->ondisk->parent = parent->node_offset;
1969                 if (cursor->parent) {
1970                         hammer_unlock(&cursor->parent->lock);
1971                         hammer_rel_node(cursor->parent);
1972                 }
1973                 cursor->parent = parent;        /* lock'd and ref'd */
1974                 hammer_rel_volume(volume, 0);
1975         }
1976         hammer_modify_node_done(leaf);
1977
1978         /*
1979          * Ok, now adjust the cursor depending on which element the original
1980          * index was pointing at.  If we are >= the split point the push node
1981          * is now in the new node.
1982          *
1983          * NOTE: If we are at the split point itself we need to select the
1984          * old or new node based on where key_beg's insertion point will be.
1985          * If we pick the wrong side the inserted element will wind up in
1986          * the wrong leaf node and outside that node's bounds.
1987          */
1988         if (cursor->index > split ||
1989             (cursor->index == split &&
1990              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1991                 cursor->parent_index = parent_index + 1;
1992                 cursor->index -= split;
1993                 hammer_unlock(&cursor->node->lock);
1994                 hammer_rel_node(cursor->node);
1995                 cursor->node = new_leaf;
1996         } else {
1997                 cursor->parent_index = parent_index;
1998                 hammer_unlock(&new_leaf->lock);
1999                 hammer_rel_node(new_leaf);
2000         }
2001
2002         /*
2003          * Fixup left and right bounds
2004          */
2005         parent_elm = &parent->ondisk->elms[cursor->parent_index];
2006         cursor->left_bound = &parent_elm[0].internal.base;
2007         cursor->right_bound = &parent_elm[1].internal.base;
2008
2009         /*
2010          * Assert that the bounds are correct.
2011          */
2012         KKASSERT(hammer_btree_cmp(cursor->left_bound,
2013                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
2014         KKASSERT(hammer_btree_cmp(cursor->right_bound,
2015                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
2016         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
2017         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
2018
2019 done:
2020         hammer_cursor_downgrade(cursor);
2021         return (error);
2022 }
2023
2024 #if 0
2025
2026 /*
2027  * Recursively correct the right-hand boundary's create_tid to (tid) as
2028  * long as the rest of the key matches.  We have to recurse upward in
2029  * the tree as well as down the left side of each parent's right node.
2030  *
2031  * Return EDEADLK if we were only partially successful, forcing the caller
2032  * to try again.  The original cursor is not modified.  This routine can
2033  * also fail with EDEADLK if it is forced to throw away a portion of its
2034  * record history.
2035  *
2036  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
2037  */
2038 struct hammer_rhb {
2039         TAILQ_ENTRY(hammer_rhb) entry;
2040         hammer_node_t   node;
2041         int             index;
2042 };
2043
2044 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
2045
2046 int
2047 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
2048 {
2049         struct hammer_mount *hmp;
2050         struct hammer_rhb_list rhb_list;
2051         hammer_base_elm_t elm;
2052         hammer_node_t orig_node;
2053         struct hammer_rhb *rhb;
2054         int orig_index;
2055         int error;
2056
2057         TAILQ_INIT(&rhb_list);
2058         hmp = cursor->trans->hmp;
2059
2060         /*
2061          * Save our position so we can restore it on return.  This also
2062          * gives us a stable 'elm'.
2063          */
2064         orig_node = cursor->node;
2065         hammer_ref_node(orig_node);
2066         hammer_lock_sh(&orig_node->lock);
2067         orig_index = cursor->index;
2068         elm = &orig_node->ondisk->elms[orig_index].base;
2069
2070         /*
2071          * Now build a list of parents going up, allocating a rhb
2072          * structure for each one.
2073          */
2074         while (cursor->parent) {
2075                 /*
2076                  * Stop if we no longer have any right-bounds to fix up
2077                  */
2078                 if (elm->obj_id != cursor->right_bound->obj_id ||
2079                     elm->rec_type != cursor->right_bound->rec_type ||
2080                     elm->key != cursor->right_bound->key) {
2081                         break;
2082                 }
2083
2084                 /*
2085                  * Stop if the right-hand bound's create_tid does not
2086                  * need to be corrected.
2087                  */
2088                 if (cursor->right_bound->create_tid >= tid)
2089                         break;
2090
2091                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2092                 rhb->node = cursor->parent;
2093                 rhb->index = cursor->parent_index;
2094                 hammer_ref_node(rhb->node);
2095                 hammer_lock_sh(&rhb->node->lock);
2096                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2097
2098                 hammer_cursor_up(cursor);
2099         }
2100
2101         /*
2102          * now safely adjust the right hand bound for each rhb.  This may
2103          * also require taking the right side of the tree and iterating down
2104          * ITS left side.
2105          */
2106         error = 0;
2107         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2108                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2109                 if (error)
2110                         break;
2111                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2112                 hammer_unlock(&rhb->node->lock);
2113                 hammer_rel_node(rhb->node);
2114                 kfree(rhb, hmp->m_misc);
2115
2116                 switch (cursor->node->ondisk->type) {
2117                 case HAMMER_BTREE_TYPE_INTERNAL:
2118                         /*
2119                          * Right-boundary for parent at internal node
2120                          * is one element to the right of the element whos
2121                          * right boundary needs adjusting.  We must then
2122                          * traverse down the left side correcting any left
2123                          * bounds (which may now be too far to the left).
2124                          */
2125                         ++cursor->index;
2126                         error = hammer_btree_correct_lhb(cursor, tid);
2127                         break;
2128                 default:
2129                         panic("hammer_btree_correct_rhb(): Bad node type");
2130                         error = EINVAL;
2131                         break;
2132                 }
2133         }
2134
2135         /*
2136          * Cleanup
2137          */
2138         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2139                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2140                 hammer_unlock(&rhb->node->lock);
2141                 hammer_rel_node(rhb->node);
2142                 kfree(rhb, hmp->m_misc);
2143         }
2144         error = hammer_cursor_seek(cursor, orig_node, orig_index);
2145         hammer_unlock(&orig_node->lock);
2146         hammer_rel_node(orig_node);
2147         return (error);
2148 }
2149
2150 /*
2151  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2152  * bound going downward starting at the current cursor position.
2153  *
2154  * This function does not restore the cursor after use.
2155  */
2156 int
2157 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2158 {
2159         struct hammer_rhb_list rhb_list;
2160         hammer_base_elm_t elm;
2161         hammer_base_elm_t cmp;
2162         struct hammer_rhb *rhb;
2163         struct hammer_mount *hmp;
2164         int error;
2165
2166         TAILQ_INIT(&rhb_list);
2167         hmp = cursor->trans->hmp;
2168
2169         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2170
2171         /*
2172          * Record the node and traverse down the left-hand side for all
2173          * matching records needing a boundary correction.
2174          */
2175         error = 0;
2176         for (;;) {
2177                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2178                 rhb->node = cursor->node;
2179                 rhb->index = cursor->index;
2180                 hammer_ref_node(rhb->node);
2181                 hammer_lock_sh(&rhb->node->lock);
2182                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2183
2184                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2185                         /*
2186                          * Nothing to traverse down if we are at the right
2187                          * boundary of an internal node.
2188                          */
2189                         if (cursor->index == cursor->node->ondisk->count)
2190                                 break;
2191                 } else {
2192                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2193                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2194                                 break;
2195                         panic("Illegal leaf record type %02x", elm->btype);
2196                 }
2197                 error = hammer_cursor_down(cursor);
2198                 if (error)
2199                         break;
2200
2201                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2202                 if (elm->obj_id != cmp->obj_id ||
2203                     elm->rec_type != cmp->rec_type ||
2204                     elm->key != cmp->key) {
2205                         break;
2206                 }
2207                 if (elm->create_tid >= tid)
2208                         break;
2209
2210         }
2211
2212         /*
2213          * Now we can safely adjust the left-hand boundary from the bottom-up.
2214          * The last element we remove from the list is the caller's right hand
2215          * boundary, which must also be adjusted.
2216          */
2217         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2218                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2219                 if (error)
2220                         break;
2221                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2222                 hammer_unlock(&rhb->node->lock);
2223                 hammer_rel_node(rhb->node);
2224                 kfree(rhb, hmp->m_misc);
2225
2226                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2227                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2228                         hammer_modify_node(cursor->trans, cursor->node,
2229                                            &elm->create_tid,
2230                                            sizeof(elm->create_tid));
2231                         elm->create_tid = tid;
2232                         hammer_modify_node_done(cursor->node);
2233                 } else {
2234                         panic("hammer_btree_correct_lhb(): Bad element type");
2235                 }
2236         }
2237
2238         /*
2239          * Cleanup
2240          */
2241         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2242                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2243                 hammer_unlock(&rhb->node->lock);
2244                 hammer_rel_node(rhb->node);
2245                 kfree(rhb, hmp->m_misc);
2246         }
2247         return (error);
2248 }
2249
2250 #endif
2251
2252 /*
2253  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2254  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2255  * the operation due to a deadlock, or some other error.
2256  *
2257  * This routine is initially called with an empty leaf and may be
2258  * recursively called with single-element internal nodes.
2259  *
2260  * It should also be noted that when removing empty leaves we must be sure
2261  * to test and update mirror_tid because another thread may have deadlocked
2262  * against us (or someone) trying to propagate it up and cannot retry once
2263  * the node has been deleted.
2264  *
2265  * On return the cursor may end up pointing to an internal node, suitable
2266  * for further iteration but not for an immediate insertion or deletion.
2267  */
2268 static int
2269 btree_remove(hammer_cursor_t cursor)
2270 {
2271         hammer_node_ondisk_t ondisk;
2272         hammer_btree_elm_t elm;
2273         hammer_node_t node;
2274         hammer_node_t parent;
2275         const int esize = sizeof(*elm);
2276         int error;
2277
2278         node = cursor->node;
2279
2280         /*
2281          * When deleting the root of the filesystem convert it to
2282          * an empty leaf node.  Internal nodes cannot be empty.
2283          */
2284         ondisk = node->ondisk;
2285         if (ondisk->parent == 0) {
2286                 KKASSERT(cursor->parent == NULL);
2287                 hammer_modify_node_all(cursor->trans, node);
2288                 KKASSERT(ondisk == node->ondisk);
2289                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2290                 ondisk->count = 0;
2291                 hammer_modify_node_done(node);
2292                 cursor->index = 0;
2293                 return(0);
2294         }
2295
2296         parent = cursor->parent;
2297
2298         /*
2299          * Attempt to remove the parent's reference to the child.  If the
2300          * parent would become empty we have to recurse.  If we fail we
2301          * leave the parent pointing to an empty leaf node.
2302          *
2303          * We have to recurse successfully before we can delete the internal
2304          * node as it is illegal to have empty internal nodes.  Even though
2305          * the operation may be aborted we must still fixup any unlocked
2306          * cursors as if we had deleted the element prior to recursing
2307          * (by calling hammer_cursor_deleted_element()) so those cursors
2308          * are properly forced up the chain by the recursion.
2309          */
2310         if (parent->ondisk->count == 1) {
2311                 /*
2312                  * This special cursor_up_locked() call leaves the original
2313                  * node exclusively locked and referenced, leaves the
2314                  * original parent locked (as the new node), and locks the
2315                  * new parent.  It can return EDEADLK.
2316                  *
2317                  * We cannot call hammer_cursor_removed_node() until we are
2318                  * actually able to remove the node.  If we did then tracked
2319                  * cursors in the middle of iterations could be repointed
2320                  * to a parent node.  If this occurs they could end up
2321                  * scanning newly inserted records into the node (that could
2322                  * not be deleted) when they push down again.
2323                  *
2324                  * Due to the way the recursion works the final parent is left
2325                  * in cursor->parent after the recursion returns.  Each
2326                  * layer on the way back up is thus able to call
2327                  * hammer_cursor_removed_node() and 'jump' the node up to
2328                  * the (same) final parent.
2329                  *
2330                  * NOTE!  The local variable 'parent' is invalid after we
2331                  *        call hammer_cursor_up_locked().
2332                  */
2333                 error = hammer_cursor_up_locked(cursor);
2334                 parent = NULL;
2335
2336                 if (error == 0) {
2337                         hammer_cursor_deleted_element(cursor->node, 0);
2338                         error = btree_remove(cursor);
2339                         if (error == 0) {
2340                                 KKASSERT(node != cursor->node);
2341                                 hammer_cursor_removed_node(
2342                                         node, cursor->node,
2343                                         cursor->index);
2344                                 hammer_modify_node_all(cursor->trans, node);
2345                                 ondisk = node->ondisk;
2346                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2347                                 ondisk->count = 0;
2348                                 hammer_modify_node_done(node);
2349                                 hammer_flush_node(node, 0);
2350                                 hammer_delete_node(cursor->trans, node);
2351                         } else {
2352                                 /*
2353                                  * Defer parent removal because we could not
2354                                  * get the lock, just let the leaf remain
2355                                  * empty.
2356                                  */
2357                                 /**/
2358                         }
2359                         hammer_unlock(&node->lock);
2360                         hammer_rel_node(node);
2361                 } else {
2362                         /*
2363                          * Defer parent removal because we could not
2364                          * get the lock, just let the leaf remain
2365                          * empty.
2366                          */
2367                         /**/
2368                 }
2369         } else {
2370                 KKASSERT(parent->ondisk->count > 1);
2371
2372                 hammer_modify_node_all(cursor->trans, parent);
2373                 ondisk = parent->ondisk;
2374                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2375
2376                 elm = &ondisk->elms[cursor->parent_index];
2377                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2378                 KKASSERT(ondisk->count > 0);
2379
2380                 /*
2381                  * We must retain the highest mirror_tid.  The deleted
2382                  * range is now encompassed by the element to the left.
2383                  * If we are already at the left edge the new left edge
2384                  * inherits mirror_tid.
2385                  *
2386                  * Note that bounds of the parent to our parent may create
2387                  * a gap to the left of our left-most node or to the right
2388                  * of our right-most node.  The gap is silently included
2389                  * in the mirror_tid's area of effect from the point of view
2390                  * of the scan.
2391                  */
2392                 if (cursor->parent_index) {
2393                         if (elm[-1].internal.mirror_tid <
2394                             elm[0].internal.mirror_tid) {
2395                                 elm[-1].internal.mirror_tid =
2396                                     elm[0].internal.mirror_tid;
2397                         }
2398                 } else {
2399                         if (elm[1].internal.mirror_tid <
2400                             elm[0].internal.mirror_tid) {
2401                                 elm[1].internal.mirror_tid =
2402                                     elm[0].internal.mirror_tid;
2403                         }
2404                 }
2405
2406                 /*
2407                  * Delete the subtree reference in the parent.  Include
2408                  * boundary element at end.
2409                  */
2410                 bcopy(&elm[1], &elm[0],
2411                       (ondisk->count - cursor->parent_index) * esize);
2412                 --ondisk->count;
2413                 hammer_modify_node_done(parent);
2414                 hammer_cursor_removed_node(node, parent, cursor->parent_index);
2415                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2416                 hammer_flush_node(node, 0);
2417                 hammer_delete_node(cursor->trans, node);
2418
2419                 /*
2420                  * cursor->node is invalid, cursor up to make the cursor
2421                  * valid again.  We have to flag the condition in case
2422                  * another thread wiggles an insertion in during an
2423                  * iteration.
2424                  */
2425                 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
2426                 error = hammer_cursor_up(cursor);
2427         }
2428         return (error);
2429 }
2430
2431 /*
2432  * Propagate cursor->trans->tid up the B-Tree starting at the current
2433  * cursor position using pseudofs info gleaned from the passed inode.
2434  *
2435  * The passed inode has no relationship to the cursor position other
2436  * then being in the same pseudofs as the insertion or deletion we
2437  * are propagating the mirror_tid for.
2438  *
2439  * WARNING!  Because we push and pop the passed cursor, it may be
2440  *           modified by other B-Tree operations while it is unlocked
2441  *           and things like the node & leaf pointers, and indexes might
2442  *           change.
2443  */
2444 void
2445 hammer_btree_do_propagation(hammer_cursor_t cursor,
2446                             hammer_pseudofs_inmem_t pfsm,
2447                             hammer_btree_leaf_elm_t leaf)
2448 {
2449         hammer_cursor_t ncursor;
2450         hammer_tid_t mirror_tid;
2451         int error;
2452
2453         /*
2454          * We do not propagate a mirror_tid if the filesystem was mounted
2455          * in no-mirror mode.
2456          */
2457         if (cursor->trans->hmp->master_id < 0)
2458                 return;
2459
2460         /*
2461          * This is a bit of a hack because we cannot deadlock or return
2462          * EDEADLK here.  The related operation has already completed and
2463          * we must propagate the mirror_tid now regardless.
2464          *
2465          * Generate a new cursor which inherits the original's locks and
2466          * unlock the original.  Use the new cursor to propagate the
2467          * mirror_tid.  Then clean up the new cursor and reacquire locks
2468          * on the original.
2469          *
2470          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2471          * original's locks and the original is tracked and must be
2472          * re-locked.
2473          */
2474         mirror_tid = cursor->node->ondisk->mirror_tid;
2475         KKASSERT(mirror_tid != 0);
2476         ncursor = hammer_push_cursor(cursor);
2477         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2478         KKASSERT(error == 0);
2479         hammer_pop_cursor(cursor, ncursor);
2480         /* WARNING: cursor's leaf pointer may change after pop */
2481 }
2482
2483
2484 /*
2485  * Propagate a mirror TID update upwards through the B-Tree to the root.
2486  *
2487  * A locked internal node must be passed in.  The node will remain locked
2488  * on return.
2489  *
2490  * This function syncs mirror_tid at the specified internal node's element,
2491  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2492  */
2493 static int
2494 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2495 {
2496         hammer_btree_internal_elm_t elm;
2497         hammer_node_t node;
2498         int error;
2499
2500         for (;;) {
2501                 error = hammer_cursor_up(cursor);
2502                 if (error == 0)
2503                         error = hammer_cursor_upgrade(cursor);
2504
2505                 /*
2506                  * We can ignore HAMMER_CURSOR_ITERATE_CHECK, the
2507                  * cursor will still be properly positioned for
2508                  * mirror propagation, just not for iterations.
2509                  */
2510                 while (error == EDEADLK) {
2511                         hammer_recover_cursor(cursor);
2512                         error = hammer_cursor_upgrade(cursor);
2513                 }
2514                 if (error)
2515                         break;
2516
2517                 /*
2518                  * If the cursor deadlocked it could end up at a leaf
2519                  * after we lost the lock.
2520                  */
2521                 node = cursor->node;
2522                 if (node->ondisk->type != HAMMER_BTREE_TYPE_INTERNAL)
2523                         continue;
2524
2525                 /*
2526                  * Adjust the node's element
2527                  */
2528                 elm = &node->ondisk->elms[cursor->index].internal;
2529                 if (elm->mirror_tid >= mirror_tid)
2530                         break;
2531                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2532                                    sizeof(elm->mirror_tid));
2533                 elm->mirror_tid = mirror_tid;
2534                 hammer_modify_node_done(node);
2535                 if (hammer_debug_general & 0x0002) {
2536                         kprintf("mirror_propagate: propagate "
2537                                 "%016llx @%016llx:%d\n",
2538                                 (long long)mirror_tid,
2539                                 (long long)node->node_offset,
2540                                 cursor->index);
2541                 }
2542
2543
2544                 /*
2545                  * Adjust the node's mirror_tid aggregator
2546                  */
2547                 if (node->ondisk->mirror_tid >= mirror_tid)
2548                         return(0);
2549                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2550                 node->ondisk->mirror_tid = mirror_tid;
2551                 hammer_modify_node_done(node);
2552                 if (hammer_debug_general & 0x0002) {
2553                         kprintf("mirror_propagate: propagate "
2554                                 "%016llx @%016llx\n",
2555                                 (long long)mirror_tid,
2556                                 (long long)node->node_offset);
2557                 }
2558         }
2559         if (error == ENOENT)
2560                 error = 0;
2561         return(error);
2562 }
2563
2564 hammer_node_t
2565 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2566                         int *parent_indexp, int *errorp, int try_exclusive)
2567 {
2568         hammer_node_t parent;
2569         hammer_btree_elm_t elm;
2570         int i;
2571
2572         /*
2573          * Get the node
2574          */
2575         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2576         if (*errorp) {
2577                 KKASSERT(parent == NULL);
2578                 return(NULL);
2579         }
2580         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2581
2582         /*
2583          * Lock the node
2584          */
2585         if (try_exclusive) {
2586                 if (hammer_lock_ex_try(&parent->lock)) {
2587                         hammer_rel_node(parent);
2588                         *errorp = EDEADLK;
2589                         return(NULL);
2590                 }
2591         } else {
2592                 hammer_lock_sh(&parent->lock);
2593         }
2594
2595         /*
2596          * Figure out which element in the parent is pointing to the
2597          * child.
2598          */
2599         if (node->ondisk->count) {
2600                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2601                                              parent->ondisk);
2602         } else {
2603                 i = 0;
2604         }
2605         while (i < parent->ondisk->count) {
2606                 elm = &parent->ondisk->elms[i];
2607                 if (elm->internal.subtree_offset == node->node_offset)
2608                         break;
2609                 ++i;
2610         }
2611         if (i == parent->ondisk->count) {
2612                 hammer_unlock(&parent->lock);
2613                 panic("Bad B-Tree link: parent %p node %p\n", parent, node);
2614         }
2615         *parent_indexp = i;
2616         KKASSERT(*errorp == 0);
2617         return(parent);
2618 }
2619
2620 /*
2621  * The element (elm) has been moved to a new internal node (node).
2622  *
2623  * If the element represents a pointer to an internal node that node's
2624  * parent must be adjusted to the element's new location.
2625  *
2626  * XXX deadlock potential here with our exclusive locks
2627  */
2628 int
2629 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2630                  hammer_btree_elm_t elm)
2631 {
2632         hammer_node_t child;
2633         int error;
2634
2635         error = 0;
2636
2637         switch(elm->base.btype) {
2638         case HAMMER_BTREE_TYPE_INTERNAL:
2639         case HAMMER_BTREE_TYPE_LEAF:
2640                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2641                                         0, &error);
2642                 if (error == 0) {
2643                         hammer_modify_node_field(trans, child, parent);
2644                         child->ondisk->parent = node->node_offset;
2645                         hammer_modify_node_done(child);
2646                         hammer_rel_node(child);
2647                 }
2648                 break;
2649         default:
2650                 break;
2651         }
2652         return(error);
2653 }
2654
2655 /*
2656  * Initialize the root of a recursive B-Tree node lock list structure.
2657  */
2658 void
2659 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2660 {
2661         TAILQ_INIT(&parent->list);
2662         parent->parent = NULL;
2663         parent->node = node;
2664         parent->index = -1;
2665         parent->count = node->ondisk->count;
2666         parent->copy = NULL;
2667         parent->flags = 0;
2668 }
2669
2670 /*
2671  * Exclusively lock all the children of node.  This is used by the split
2672  * code to prevent anyone from accessing the children of a cursor node
2673  * while we fix-up its parent offset.
2674  *
2675  * If we don't lock the children we can really mess up cursors which block
2676  * trying to cursor-up into our node.
2677  *
2678  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2679  * error is returned the cursor is adjusted to block on termination.
2680  *
2681  * The caller is responsible for managing parent->node, the root's node
2682  * is usually aliased from a cursor.
2683  */
2684 int
2685 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2686                            hammer_node_lock_t parent)
2687 {
2688         hammer_node_t node;
2689         hammer_node_lock_t item;
2690         hammer_node_ondisk_t ondisk;
2691         hammer_btree_elm_t elm;
2692         hammer_node_t child;
2693         struct hammer_mount *hmp;
2694         int error;
2695         int i;
2696
2697         node = parent->node;
2698         ondisk = node->ondisk;
2699         error = 0;
2700         hmp = cursor->trans->hmp;
2701
2702         /*
2703          * We really do not want to block on I/O with exclusive locks held,
2704          * pre-get the children before trying to lock the mess.  This is
2705          * only done one-level deep for now.
2706          */
2707         for (i = 0; i < ondisk->count; ++i) {
2708                 ++hammer_stats_btree_elements;
2709                 elm = &ondisk->elms[i];
2710                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2711                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2712                         continue;
2713                 }
2714                 child = hammer_get_node(cursor->trans,
2715                                         elm->internal.subtree_offset,
2716                                         0, &error);
2717                 if (child)
2718                         hammer_rel_node(child);
2719         }
2720
2721         /*
2722          * Do it for real
2723          */
2724         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2725                 ++hammer_stats_btree_elements;
2726                 elm = &ondisk->elms[i];
2727
2728                 switch(elm->base.btype) {
2729                 case HAMMER_BTREE_TYPE_INTERNAL:
2730                 case HAMMER_BTREE_TYPE_LEAF:
2731                         KKASSERT(elm->internal.subtree_offset != 0);
2732                         child = hammer_get_node(cursor->trans,
2733                                                 elm->internal.subtree_offset,
2734                                                 0, &error);
2735                         break;
2736                 default:
2737                         child = NULL;
2738                         break;
2739                 }
2740                 if (child) {
2741                         if (hammer_lock_ex_try(&child->lock) != 0) {
2742                                 if (cursor->deadlk_node == NULL) {
2743                                         cursor->deadlk_node = child;
2744                                         hammer_ref_node(cursor->deadlk_node);
2745                                 }
2746                                 error = EDEADLK;
2747                                 hammer_rel_node(child);
2748                         } else {
2749                                 item = kmalloc(sizeof(*item), hmp->m_misc,
2750                                                M_WAITOK|M_ZERO);
2751                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2752                                 TAILQ_INIT(&item->list);
2753                                 item->parent = parent;
2754                                 item->node = child;
2755                                 item->index = i;
2756                                 item->count = child->ondisk->count;
2757
2758                                 /*
2759                                  * Recurse (used by the rebalancing code)
2760                                  */
2761                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2762                                         error = hammer_btree_lock_children(
2763                                                         cursor,
2764                                                         depth - 1,
2765                                                         item);
2766                                 }
2767                         }
2768                 }
2769         }
2770         if (error)
2771                 hammer_btree_unlock_children(cursor, parent);
2772         return(error);
2773 }
2774
2775 /*
2776  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2777  * including the parent.
2778  */
2779 void
2780 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2781 {
2782         hammer_mount_t hmp = cursor->trans->hmp;
2783         hammer_node_lock_t item;
2784
2785         if (parent->copy == NULL) {
2786                 parent->copy = kmalloc(sizeof(*parent->copy), hmp->m_misc,
2787                                        M_WAITOK);
2788                 *parent->copy = *parent->node->ondisk;
2789         }
2790         TAILQ_FOREACH(item, &parent->list, entry) {
2791                 hammer_btree_lock_copy(cursor, item);
2792         }
2793 }
2794
2795 /*
2796  * Recursively sync modified copies to the media.
2797  */
2798 int
2799 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2800 {
2801         hammer_node_lock_t item;
2802         int count = 0;
2803
2804         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2805                 ++count;
2806                 hammer_modify_node_all(cursor->trans, parent->node);
2807                 *parent->node->ondisk = *parent->copy;
2808                 hammer_modify_node_done(parent->node);
2809                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2810                         hammer_flush_node(parent->node, 0);
2811                         hammer_delete_node(cursor->trans, parent->node);
2812                 }
2813         }
2814         TAILQ_FOREACH(item, &parent->list, entry) {
2815                 count += hammer_btree_sync_copy(cursor, item);
2816         }
2817         return(count);
2818 }
2819
2820 /*
2821  * Release previously obtained node locks.  The caller is responsible for
2822  * cleaning up parent->node itself (its usually just aliased from a cursor),
2823  * but this function will take care of the copies.
2824  */
2825 void
2826 hammer_btree_unlock_children(hammer_cursor_t cursor, hammer_node_lock_t parent)
2827 {
2828         hammer_node_lock_t item;
2829
2830         if (parent->copy) {
2831                 kfree(parent->copy, cursor->trans->hmp->m_misc);
2832                 parent->copy = NULL;    /* safety */
2833         }
2834         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2835                 TAILQ_REMOVE(&parent->list, item, entry);
2836                 hammer_btree_unlock_children(cursor, item);
2837                 hammer_unlock(&item->node->lock);
2838                 hammer_rel_node(item->node);
2839                 kfree(item, cursor->trans->hmp->m_misc);
2840         }
2841 }
2842
2843 /************************************************************************
2844  *                         MISCELLANIOUS SUPPORT                        *
2845  ************************************************************************/
2846
2847 /*
2848  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2849  *
2850  * Note that for this particular function a return value of -1, 0, or +1
2851  * can denote a match if create_tid is otherwise discounted.  A create_tid
2852  * of zero is considered to be 'infinity' in comparisons.
2853  *
2854  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2855  */
2856 int
2857 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2858 {
2859         if (key1->localization < key2->localization)
2860                 return(-5);
2861         if (key1->localization > key2->localization)
2862                 return(5);
2863
2864         if (key1->obj_id < key2->obj_id)
2865                 return(-4);
2866         if (key1->obj_id > key2->obj_id)
2867                 return(4);
2868
2869         if (key1->rec_type < key2->rec_type)
2870                 return(-3);
2871         if (key1->rec_type > key2->rec_type)
2872                 return(3);
2873
2874         if (key1->key < key2->key)
2875                 return(-2);
2876         if (key1->key > key2->key)
2877                 return(2);
2878
2879         /*
2880          * A create_tid of zero indicates a record which is undeletable
2881          * and must be considered to have a value of positive infinity.
2882          */
2883         if (key1->create_tid == 0) {
2884                 if (key2->create_tid == 0)
2885                         return(0);
2886                 return(1);
2887         }
2888         if (key2->create_tid == 0)
2889                 return(-1);
2890         if (key1->create_tid < key2->create_tid)
2891                 return(-1);
2892         if (key1->create_tid > key2->create_tid)
2893                 return(1);
2894         return(0);
2895 }
2896
2897 /*
2898  * Test a timestamp against an element to determine whether the
2899  * element is visible.  A timestamp of 0 means 'infinity'.
2900  */
2901 int
2902 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2903 {
2904         if (asof == 0) {
2905                 if (base->delete_tid)
2906                         return(1);
2907                 return(0);
2908         }
2909         if (asof < base->create_tid)
2910                 return(-1);
2911         if (base->delete_tid && asof >= base->delete_tid)
2912                 return(1);
2913         return(0);
2914 }
2915
2916 /*
2917  * Create a separator half way inbetween key1 and key2.  For fields just
2918  * one unit apart, the separator will match key2.  key1 is on the left-hand
2919  * side and key2 is on the right-hand side.
2920  *
2921  * key2 must be >= the separator.  It is ok for the separator to match key2.
2922  *
2923  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2924  * key2.
2925  *
2926  * NOTE: It might be beneficial to just scrap this whole mess and just
2927  * set the separator to key2.
2928  */
2929 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2930         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2931
2932 static void
2933 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2934                       hammer_base_elm_t dest)
2935 {
2936         bzero(dest, sizeof(*dest));
2937
2938         dest->rec_type = key2->rec_type;
2939         dest->key = key2->key;
2940         dest->obj_id = key2->obj_id;
2941         dest->create_tid = key2->create_tid;
2942
2943         MAKE_SEPARATOR(key1, key2, dest, localization);
2944         if (key1->localization == key2->localization) {
2945                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
2946                 if (key1->obj_id == key2->obj_id) {
2947                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
2948                         if (key1->rec_type == key2->rec_type) {
2949                                 MAKE_SEPARATOR(key1, key2, dest, key);
2950                                 /*
2951                                  * Don't bother creating a separator for
2952                                  * create_tid, which also conveniently avoids
2953                                  * having to handle the create_tid == 0
2954                                  * (infinity) case.  Just leave create_tid
2955                                  * set to key2.
2956                                  *
2957                                  * Worst case, dest matches key2 exactly,
2958                                  * which is acceptable.
2959                                  */
2960                         }
2961                 }
2962         }
2963 }
2964
2965 #undef MAKE_SEPARATOR
2966
2967 /*
2968  * Return whether a generic internal or leaf node is full
2969  */
2970 static int
2971 btree_node_is_full(hammer_node_ondisk_t node)
2972 {
2973         switch(node->type) {
2974         case HAMMER_BTREE_TYPE_INTERNAL:
2975                 if (node->count == HAMMER_BTREE_INT_ELMS)
2976                         return(1);
2977                 break;
2978         case HAMMER_BTREE_TYPE_LEAF:
2979                 if (node->count == HAMMER_BTREE_LEAF_ELMS)
2980                         return(1);
2981                 break;
2982         default:
2983                 panic("illegal btree subtype");
2984         }
2985         return(0);
2986 }
2987
2988 #if 0
2989 static int
2990 btree_max_elements(u_int8_t type)
2991 {
2992         if (type == HAMMER_BTREE_TYPE_LEAF)
2993                 return(HAMMER_BTREE_LEAF_ELMS);
2994         if (type == HAMMER_BTREE_TYPE_INTERNAL)
2995                 return(HAMMER_BTREE_INT_ELMS);
2996         panic("btree_max_elements: bad type %d\n", type);
2997 }
2998 #endif
2999
3000 void
3001 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
3002 {
3003         hammer_btree_elm_t elm;
3004         int i;
3005
3006         kprintf("node %p count=%d parent=%016llx type=%c\n",
3007                 ondisk, ondisk->count,
3008                 (long long)ondisk->parent, ondisk->type);
3009
3010         /*
3011          * Dump both boundary elements if an internal node
3012          */
3013         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
3014                 for (i = 0; i <= ondisk->count; ++i) {
3015                         elm = &ondisk->elms[i];
3016                         hammer_print_btree_elm(elm, ondisk->type, i);
3017                 }
3018         } else {
3019                 for (i = 0; i < ondisk->count; ++i) {
3020                         elm = &ondisk->elms[i];
3021                         hammer_print_btree_elm(elm, ondisk->type, i);
3022                 }
3023         }
3024 }
3025
3026 void
3027 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
3028 {
3029         kprintf("  %2d", i);
3030         kprintf("\tobj_id       = %016llx\n", (long long)elm->base.obj_id);
3031         kprintf("\tkey          = %016llx\n", (long long)elm->base.key);
3032         kprintf("\tcreate_tid   = %016llx\n", (long long)elm->base.create_tid);
3033         kprintf("\tdelete_tid   = %016llx\n", (long long)elm->base.delete_tid);
3034         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
3035         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
3036         kprintf("\tbtype        = %02x (%c)\n",
3037                 elm->base.btype,
3038                 (elm->base.btype ? elm->base.btype : '?'));
3039         kprintf("\tlocalization = %02x\n", elm->base.localization);
3040
3041         switch(type) {
3042         case HAMMER_BTREE_TYPE_INTERNAL:
3043                 kprintf("\tsubtree_off  = %016llx\n",
3044                         (long long)elm->internal.subtree_offset);
3045                 break;
3046         case HAMMER_BTREE_TYPE_RECORD:
3047                 kprintf("\tdata_offset  = %016llx\n",
3048                         (long long)elm->leaf.data_offset);
3049                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
3050                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
3051                 break;
3052         }
3053 }