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  * NOTE!  EDEADLK *CANNOT* be returned by this procedure.
 114  */
 115 int
 116 hammer_btree_iterate(hammer_cursor_t cursor)
 117 {
 118         hammer_node_ondisk_t node;
 119         hammer_btree_elm_t elm;
 120         int error = 0;
 121         int r;
 122         int s;
 123
 124         /*
 125          * Skip past the current record
 126          */
 127         node = cursor->node->ondisk;
 128         if (node == NULL)
 129                 return(ENOENT);
 130         if (cursor->index < node->count &&
 131             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 132                 ++cursor->index;
 133         }
 134
 135         /*
 136          * Loop until an element is found or we are done.
 137          */
 138         for (;;) {
 139                 /*
 140                  * We iterate up the tree and then index over one element
 141                  * while we are at the last element in the current node.
 142                  *
 143                  * If we are at the root of the filesystem, cursor_up
 144                  * returns ENOENT.
 145                  *
 146                  * XXX this could be optimized by storing the information in
 147                  * the parent reference.
 148                  *
 149                  * XXX we can lose the node lock temporarily, this could mess
 150                  * up our scan.
 151                  */
 152                 ++hammer_stats_btree_iterations;
 153                 hammer_flusher_clean_loose_ios(cursor->trans->hmp);
 154
 155                 if (cursor->index == node->count) {
 156                         if (hammer_debug_btree) {
 157                                 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
 158                                         cursor->node->node_offset,
 159                                         cursor->index,
 160                                         (cursor->parent ? cursor->parent->node_offset : -1),
 161                                         cursor->parent_index,
 162                                         curthread);
 163                         }
 164                         KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
 165                         error = hammer_cursor_up(cursor);
 166                         if (error)
 167                                 break;
 168                         /* reload stale pointer */
 169                         node = cursor->node->ondisk;
 170                         KKASSERT(cursor->index != node->count);
 171
 172                         /*
 173                          * If we are reblocking we want to return internal
 174                          * nodes.  Note that the internal node will be
 175                          * returned multiple times, on each upward recursion
 176                          * from its children.  The caller selects which
 177                          * revisit it cares about (usually first or last only).
 178                          */
 179                         if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
 180                                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 181                                 return(0);
 182                         }
 183                         ++cursor->index;
 184                         continue;
 185                 }
 186
 187                 /*
 188                  * Check internal or leaf element.  Determine if the record
 189                  * at the cursor has gone beyond the end of our range.
 190                  *
 191                  * We recurse down through internal nodes.
 192                  */
 193                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 194                         elm = &node->elms[cursor->index];
 195
 196                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 197                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 198                         if (hammer_debug_btree) {
 199                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
 200                                         cursor->node->node_offset,
 201                                         cursor->index,
 202                                         elm[0].internal.base.obj_id,
 203                                         elm[0].internal.base.rec_type,
 204                                         elm[0].internal.base.key,
 205                                         elm[0].internal.base.localization,
 206                                         r,
 207                                         curthread
 208                                 );
 209                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 210                                         cursor->node->node_offset,
 211                                         cursor->index + 1,
 212                                         elm[1].internal.base.obj_id,
 213                                         elm[1].internal.base.rec_type,
 214                                         elm[1].internal.base.key,
 215                                         elm[1].internal.base.localization,
 216                                         s
 217                                 );
 218                         }
 219
 220                         if (r < 0) {
 221                                 error = ENOENT;
 222                                 break;
 223                         }
 224                         if (r == 0 && (cursor->flags &
 225                                        HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 226                                 error = ENOENT;
 227                                 break;
 228                         }
 229                         KKASSERT(s <= 0);
 230
 231                         /*
 232                          * Better not be zero
 233                          */
 234                         KKASSERT(elm->internal.subtree_offset != 0);
 235
 236                         /*
 237                          * If running the mirror filter see if we can skip
 238                          * one or more entire sub-trees.  If we can we
 239                          * return the internal mode and the caller processes
 240                          * the skipped range (see mirror_read)
 241                          */
 242                         if (cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) {
 243                                 if (elm->internal.mirror_tid <
 244                                     cursor->cmirror->mirror_tid) {
 245                                         hammer_cursor_mirror_filter(cursor);
 246                                         return(0);
 247                                 }
 248                         }
 249
 250                         error = hammer_cursor_down(cursor);
 251                         if (error)
 252                                 break;
 253                         KKASSERT(cursor->index == 0);
 254                         /* reload stale pointer */
 255                         node = cursor->node->ondisk;
 256                         continue;
 257                 } else {
 258                         elm = &node->elms[cursor->index];
 259                         r = hammer_btree_cmp(&cursor->key_end, &elm->base);
 260                         if (hammer_debug_btree) {
 261                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 262                                         cursor->node->node_offset,
 263                                         cursor->index,
 264                                         (elm[0].leaf.base.btype ?
 265                                          elm[0].leaf.base.btype : '?'),
 266                                         elm[0].leaf.base.obj_id,
 267                                         elm[0].leaf.base.rec_type,
 268                                         elm[0].leaf.base.key,
 269                                         elm[0].leaf.base.localization,
 270                                         r
 271                                 );
 272                         }
 273                         if (r < 0) {
 274                                 error = ENOENT;
 275                                 break;
 276                         }
 277
 278                         /*
 279                          * We support both end-inclusive and
 280                          * end-exclusive searches.
 281                          */
 282                         if (r == 0 &&
 283                            (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 284                                 error = ENOENT;
 285                                 break;
 286                         }
 287
 288                         switch(elm->leaf.base.btype) {
 289                         case HAMMER_BTREE_TYPE_RECORD:
 290                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 291                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 292                                         ++cursor->index;
 293                                         continue;
 294                                 }
 295                                 error = 0;
 296                                 break;
 297                         default:
 298                                 error = EINVAL;
 299                                 break;
 300                         }
 301                         if (error)
 302                                 break;
 303                 }
 304                 /*
 305                  * node pointer invalid after loop
 306                  */
 307
 308                 /*
 309                  * Return entry
 310                  */
 311                 if (hammer_debug_btree) {
 312                         int i = cursor->index;
 313                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 314                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 315                                 cursor->node, i,
 316                                 elm->internal.base.obj_id,
 317                                 elm->internal.base.rec_type,
 318                                 elm->internal.base.key,
 319                                 elm->internal.base.localization
 320                         );
 321                 }
 322                 return(0);
 323         }
 324         return(error);
 325 }
 326
 327 /*
 328  * We hit an internal element that we could skip as part of a mirroring
 329  * scan.  Calculate the entire range being skipped.
 330  *
 331  * It is important to include any gaps between the parent's left_bound
 332  * and the node's left_bound, and same goes for the right side.
 333  */
 334 static void
 335 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
 336 {
 337         struct hammer_cmirror *cmirror;
 338         hammer_node_ondisk_t ondisk;
 339         hammer_btree_elm_t elm;
 340
 341         ondisk = cursor->node->ondisk;
 342         cmirror = cursor->cmirror;
 343
 344         /*
 345          * Calculate the skipped range
 346          */
 347         elm = &ondisk->elms[cursor->index];
 348         if (cursor->index == 0)
 349                 cmirror->skip_beg = *cursor->left_bound;
 350         else
 351                 cmirror->skip_beg = elm->internal.base;
 352         while (cursor->index < ondisk->count) {
 353                 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
 354                         break;
 355                 ++cursor->index;
 356                 ++elm;
 357         }
 358         if (cursor->index == ondisk->count)
 359                 cmirror->skip_end = *cursor->right_bound;
 360         else
 361                 cmirror->skip_end = elm->internal.base;
 362
 363         /*
 364          * clip the returned result.
 365          */
 366         if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
 367                 cmirror->skip_beg = cursor->key_beg;
 368         if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
 369                 cmirror->skip_end = cursor->key_end;
 370 }
 371
 372 /*
 373  * Iterate in the reverse direction.  This is used by the pruning code to
 374  * avoid overlapping records.
 375  */
 376 int
 377 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
 378 {
 379         hammer_node_ondisk_t node;
 380         hammer_btree_elm_t elm;
 381         int error = 0;
 382         int r;
 383         int s;
 384
 385         /* mirror filtering not supported for reverse iteration */
 386         KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
 387
 388         /*
 389          * Skip past the current record.  For various reasons the cursor
 390          * may end up set to -1 or set to point at the end of the current
 391          * node.  These cases must be addressed.
 392          */
 393         node = cursor->node->ondisk;
 394         if (node == NULL)
 395                 return(ENOENT);
 396         if (cursor->index != -1 &&
 397             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 398                 --cursor->index;
 399         }
 400         if (cursor->index == cursor->node->ondisk->count)
 401                 --cursor->index;
 402
 403         /*
 404          * Loop until an element is found or we are done.
 405          */
 406         for (;;) {
 407                 ++hammer_stats_btree_iterations;
 408                 hammer_flusher_clean_loose_ios(cursor->trans->hmp);
 409
 410                 /*
 411                  * We iterate up the tree and then index over one element
 412                  * while we are at the last element in the current node.
 413                  */
 414                 if (cursor->index == -1) {
 415                         error = hammer_cursor_up(cursor);
 416                         if (error) {
 417                                 cursor->index = 0; /* sanity */
 418                                 break;
 419                         }
 420                         /* reload stale pointer */
 421                         node = cursor->node->ondisk;
 422                         KKASSERT(cursor->index != node->count);
 423                         --cursor->index;
 424                         continue;
 425                 }
 426
 427                 /*
 428                  * Check internal or leaf element.  Determine if the record
 429                  * at the cursor has gone beyond the end of our range.
 430                  *
 431                  * We recurse down through internal nodes.
 432                  */
 433                 KKASSERT(cursor->index != node->count);
 434                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 435                         elm = &node->elms[cursor->index];
 436                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 437                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 438                         if (hammer_debug_btree) {
 439                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 440                                         cursor->node->node_offset,
 441                                         cursor->index,
 442                                         elm[0].internal.base.obj_id,
 443                                         elm[0].internal.base.rec_type,
 444                                         elm[0].internal.base.key,
 445                                         elm[0].internal.base.localization,
 446                                         r
 447                                 );
 448                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 449                                         cursor->node->node_offset,
 450                                         cursor->index + 1,
 451                                         elm[1].internal.base.obj_id,
 452                                         elm[1].internal.base.rec_type,
 453                                         elm[1].internal.base.key,
 454                                         elm[1].internal.base.localization,
 455                                         s
 456                                 );
 457                         }
 458
 459                         if (s >= 0) {
 460                                 error = ENOENT;
 461                                 break;
 462                         }
 463                         KKASSERT(r >= 0);
 464
 465                         /*
 466                          * Better not be zero
 467                          */
 468                         KKASSERT(elm->internal.subtree_offset != 0);
 469
 470                         error = hammer_cursor_down(cursor);
 471                         if (error)
 472                                 break;
 473                         KKASSERT(cursor->index == 0);
 474                         /* reload stale pointer */
 475                         node = cursor->node->ondisk;
 476
 477                         /* this can assign -1 if the leaf was empty */
 478                         cursor->index = node->count - 1;
 479                         continue;
 480                 } else {
 481                         elm = &node->elms[cursor->index];
 482                         s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
 483                         if (hammer_debug_btree) {
 484                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 485                                         cursor->node->node_offset,
 486                                         cursor->index,
 487                                         (elm[0].leaf.base.btype ?
 488                                          elm[0].leaf.base.btype : '?'),
 489                                         elm[0].leaf.base.obj_id,
 490                                         elm[0].leaf.base.rec_type,
 491                                         elm[0].leaf.base.key,
 492                                         elm[0].leaf.base.localization,
 493                                         s
 494                                 );
 495                         }
 496                         if (s > 0) {
 497                                 error = ENOENT;
 498                                 break;
 499                         }
 500
 501                         switch(elm->leaf.base.btype) {
 502                         case HAMMER_BTREE_TYPE_RECORD:
 503                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 504                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 505                                         --cursor->index;
 506                                         continue;
 507                                 }
 508                                 error = 0;
 509                                 break;
 510                         default:
 511                                 error = EINVAL;
 512                                 break;
 513                         }
 514                         if (error)
 515                                 break;
 516                 }
 517                 /*
 518                  * node pointer invalid after loop
 519                  */
 520
 521                 /*
 522                  * Return entry
 523                  */
 524                 if (hammer_debug_btree) {
 525                         int i = cursor->index;
 526                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 527                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 528                                 cursor->node, i,
 529                                 elm->internal.base.obj_id,
 530                                 elm->internal.base.rec_type,
 531                                 elm->internal.base.key,
 532                                 elm->internal.base.localization
 533                         );
 534                 }
 535                 return(0);
 536         }
 537         return(error);
 538 }
 539
 540 /*
 541  * Lookup cursor->key_beg.  0 is returned on success, ENOENT if the entry
 542  * could not be found, EDEADLK if inserting and a retry is needed, and a
 543  * fatal error otherwise.  When retrying, the caller must terminate the
 544  * cursor and reinitialize it.  EDEADLK cannot be returned if not inserting.
 545  *
 546  * The cursor is suitably positioned for a deletion on success, and suitably
 547  * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
 548  * specified.
 549  *
 550  * The cursor may begin anywhere, the search will traverse the tree in
 551  * either direction to locate the requested element.
 552  *
 553  * Most of the logic implementing historical searches is handled here.  We
 554  * do an initial lookup with create_tid set to the asof TID.  Due to the
 555  * way records are laid out, a backwards iteration may be required if
 556  * ENOENT is returned to locate the historical record.  Here's the
 557  * problem:
 558  *
 559  * create_tid:    10      15       20
 560  *                   LEAF1   LEAF2
 561  * records:         (11)        (18)
 562  *
 563  * Lets say we want to do a lookup AS-OF timestamp 17.  We will traverse
 564  * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
 565  * not visible and thus causes ENOENT to be returned.  We really need
 566  * to check record 11 in LEAF1.  If it also fails then the search fails
 567  * (e.g. it might represent the range 11-16 and thus still not match our
 568  * AS-OF timestamp of 17).  Note that LEAF1 could be empty, requiring
 569  * further iterations.
 570  *
 571  * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
 572  * and the cursor->create_check TID if an iteration might be needed.
 573  * In the above example create_check would be set to 14.
 574  */
 575 int
 576 hammer_btree_lookup(hammer_cursor_t cursor)
 577 {
 578         int error;
 579
 580         KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
 581                   cursor->trans->sync_lock_refs > 0);
 582         ++hammer_stats_btree_lookups;
 583         if (cursor->flags & HAMMER_CURSOR_ASOF) {
 584                 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
 585                 cursor->key_beg.create_tid = cursor->asof;
 586                 for (;;) {
 587                         cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
 588                         error = btree_search(cursor, 0);
 589                         if (error != ENOENT ||
 590                             (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
 591                                 /*
 592                                  * Stop if no error.
 593                                  * Stop if error other then ENOENT.
 594                                  * Stop if ENOENT and not special case.
 595                                  */
 596                                 break;
 597                         }
 598                         if (hammer_debug_btree) {
 599                                 kprintf("CREATE_CHECK %016llx\n",
 600                                         cursor->create_check);
 601                         }
 602                         cursor->key_beg.create_tid = cursor->create_check;
 603                         /* loop */
 604                 }
 605         } else {
 606                 error = btree_search(cursor, 0);
 607         }
 608         if (error == 0)
 609                 error = hammer_btree_extract(cursor, cursor->flags);
 610         return(error);
 611 }
 612
 613 /*
 614  * Execute the logic required to start an iteration.  The first record
 615  * located within the specified range is returned and iteration control
 616  * flags are adjusted for successive hammer_btree_iterate() calls.
 617  *
 618  * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
 619  * in a loop without worrying about it.  Higher-level merged searches will
 620  * adjust the flag appropriately.
 621  */
 622 int
 623 hammer_btree_first(hammer_cursor_t cursor)
 624 {
 625         int error;
 626
 627         error = hammer_btree_lookup(cursor);
 628         if (error == ENOENT) {
 629                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 630                 error = hammer_btree_iterate(cursor);
 631         }
 632         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 633         return(error);
 634 }
 635
 636 /*
 637  * Similarly but for an iteration in the reverse direction.
 638  *
 639  * Set ATEDISK when iterating backwards to skip the current entry,
 640  * which after an ENOENT lookup will be pointing beyond our end point.
 641  *
 642  * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
 643  * in a loop without worrying about it.  Higher-level merged searches will
 644  * adjust the flag appropriately.
 645  */
 646 int
 647 hammer_btree_last(hammer_cursor_t cursor)
 648 {
 649         struct hammer_base_elm save;
 650         int error;
 651
 652         save = cursor->key_beg;
 653         cursor->key_beg = cursor->key_end;
 654         error = hammer_btree_lookup(cursor);
 655         cursor->key_beg = save;
 656         if (error == ENOENT ||
 657             (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 658                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 659                 error = hammer_btree_iterate_reverse(cursor);
 660         }
 661         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 662         return(error);
 663 }
 664
 665 /*
 666  * Extract the record and/or data associated with the cursor's current
 667  * position.  Any prior record or data stored in the cursor is replaced.
 668  * The cursor must be positioned at a leaf node.
 669  *
 670  * NOTE: All extractions occur at the leaf of the B-Tree.
 671  */
 672 int
 673 hammer_btree_extract(hammer_cursor_t cursor, int flags)
 674 {
 675         hammer_node_ondisk_t node;
 676         hammer_btree_elm_t elm;
 677         hammer_off_t data_off;
 678         hammer_mount_t hmp;
 679         int32_t data_len;
 680         int error;
 681
 682         /*
 683          * The case where the data reference resolves to the same buffer
 684          * as the record reference must be handled.
 685          */
 686         node = cursor->node->ondisk;
 687         elm = &node->elms[cursor->index];
 688         cursor->data = NULL;
 689         hmp = cursor->node->hmp;
 690
 691         /*
 692          * There is nothing to extract for an internal element.
 693          */
 694         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 695                 return(EINVAL);
 696
 697         /*
 698          * Only record types have data.
 699          */
 700         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 701         cursor->leaf = &elm->leaf;
 702
 703         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 704                 return(0);
 705         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 706                 return(0);
 707         data_off = elm->leaf.data_offset;
 708         data_len = elm->leaf.data_len;
 709         if (data_off == 0)
 710                 return(0);
 711
 712         /*
 713          * Load the data
 714          */
 715         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 716         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 717                                         &error, &cursor->data_buffer);
 718         if (hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 719                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 720                         elm->leaf.data_offset, elm->leaf.data_len);
 721                 if (hammer_debug_debug & 0x0001)
 722                         Debugger("CRC FAILED: DATA");
 723                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 724                         error = EDOM;   /* less critical (mirroring) */
 725                 else
 726                         error = EIO;    /* critical */
 727         }
 728         return(error);
 729 }
 730
 731
 732 /*
 733  * Insert a leaf element into the B-Tree at the current cursor position.
 734  * The cursor is positioned such that the element at and beyond the cursor
 735  * are shifted to make room for the new record.
 736  *
 737  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 738  * flag set and that call must return ENOENT before this function can be
 739  * called.
 740  *
 741  * The caller may depend on the cursor's exclusive lock after return to
 742  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 743  *
 744  * ENOSPC is returned if there is no room to insert a new record.
 745  */
 746 int
 747 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 748                     int *doprop)
 749 {
 750         hammer_node_ondisk_t node;
 751         int i;
 752         int error;
 753
 754         *doprop = 0;
 755         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 756                 return(error);
 757         ++hammer_stats_btree_inserts;
 758
 759         /*
 760          * Insert the element at the leaf node and update the count in the
 761          * parent.  It is possible for parent to be NULL, indicating that
 762          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 763          * possible.  The root inode can never be deleted so the leaf should
 764          * never be empty.
 765          *
 766          * Remember that the right-hand boundary is not included in the
 767          * count.
 768          */
 769         hammer_modify_node_all(cursor->trans, cursor->node);
 770         node = cursor->node->ondisk;
 771         i = cursor->index;
 772         KKASSERT(elm->base.btype != 0);
 773         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 774         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 775         if (i != node->count) {
 776                 bcopy(&node->elms[i], &node->elms[i+1],
 777                       (node->count - i) * sizeof(*elm));
 778         }
 779         node->elms[i].leaf = *elm;
 780         ++node->count;
 781         hammer_cursor_inserted_element(cursor->node, i);
 782
 783         /*
 784          * Update the leaf node's aggregate mirror_tid for mirroring
 785          * support.
 786          */
 787         if (node->mirror_tid < elm->base.delete_tid) {
 788                 node->mirror_tid = elm->base.delete_tid;
 789                 *doprop = 1;
 790         }
 791         if (node->mirror_tid < elm->base.create_tid) {
 792                 node->mirror_tid = elm->base.create_tid;
 793                 *doprop = 1;
 794         }
 795         hammer_modify_node_done(cursor->node);
 796
 797         /*
 798          * Debugging sanity checks.
 799          */
 800         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 801         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 802         if (i) {
 803                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 804         }
 805         if (i != node->count - 1)
 806                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 807
 808         return(0);
 809 }
 810
 811 /*
 812  * Delete a record from the B-Tree at the current cursor position.
 813  * The cursor is positioned such that the current element is the one
 814  * to be deleted.
 815  *
 816  * On return the cursor will be positioned after the deleted element and
 817  * MAY point to an internal node.  It will be suitable for the continuation
 818  * of an iteration but not for an insertion or deletion.
 819  *
 820  * Deletions will attempt to partially rebalance the B-Tree in an upward
 821  * direction, but will terminate rather then deadlock.  Empty internal nodes
 822  * are never allowed by a deletion which deadlocks may end up giving us an
 823  * empty leaf.  The pruner will clean up and rebalance the tree.
 824  *
 825  * This function can return EDEADLK, requiring the caller to retry the
 826  * operation after clearing the deadlock.
 827  */
 828 int
 829 hammer_btree_delete(hammer_cursor_t cursor)
 830 {
 831         hammer_node_ondisk_t ondisk;
 832         hammer_node_t node;
 833         hammer_node_t parent;
 834         int error;
 835         int i;
 836
 837         KKASSERT (cursor->trans->sync_lock_refs > 0);
 838         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 839                 return(error);
 840         ++hammer_stats_btree_deletes;
 841
 842         /*
 843          * Delete the element from the leaf node.
 844          *
 845          * Remember that leaf nodes do not have boundaries.
 846          */
 847         node = cursor->node;
 848         ondisk = node->ondisk;
 849         i = cursor->index;
 850
 851         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 852         KKASSERT(i >= 0 && i < ondisk->count);
 853         hammer_modify_node_all(cursor->trans, node);
 854         if (i + 1 != ondisk->count) {
 855                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 856                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 857         }
 858         --ondisk->count;
 859         hammer_modify_node_done(node);
 860         hammer_cursor_deleted_element(node, i);
 861
 862         /*
 863          * Validate local parent
 864          */
 865         if (ondisk->parent) {
 866                 parent = cursor->parent;
 867
 868                 KKASSERT(parent != NULL);
 869                 KKASSERT(parent->node_offset == ondisk->parent);
 870         }
 871
 872         /*
 873          * If the leaf becomes empty it must be detached from the parent,
 874          * potentially recursing through to the filesystem root.
 875          *
 876          * This may reposition the cursor at one of the parent's of the
 877          * current node.
 878          *
 879          * Ignore deadlock errors, that simply means that btree_remove
 880          * was unable to recurse and had to leave us with an empty leaf.
 881          */
 882         KKASSERT(cursor->index <= ondisk->count);
 883         if (ondisk->count == 0) {
 884                 error = btree_remove(cursor);
 885                 if (error == EDEADLK)
 886                         error = 0;
 887         } else {
 888                 error = 0;
 889         }
 890         KKASSERT(cursor->parent == NULL ||
 891                  cursor->parent_index < cursor->parent->ondisk->count);
 892         return(error);
 893 }
 894
 895 /*
 896  * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
 897  *
 898  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
 899  *
 900  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
 901  * iterates up the tree as necessary to properly position itself prior to
 902  * actually doing the sarch.
 903  *
 904  * INSERTIONS: The search will split full nodes and leaves on its way down
 905  * and guarentee that the leaf it ends up on is not full.  If we run out
 906  * of space the search continues to the leaf (to position the cursor for
 907  * the spike), but ENOSPC is returned.
 908  *
 909  * The search is only guarenteed to end up on a leaf if an error code of 0
 910  * is returned, or if inserting and an error code of ENOENT is returned.
 911  * Otherwise it can stop at an internal node.  On success a search returns
 912  * a leaf node.
 913  *
 914  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
 915  * filesystem, and it is not simple code.  Please note the following facts:
 916  *
 917  * - Internal node recursions have a boundary on the left AND right.  The
 918  *   right boundary is non-inclusive.  The create_tid is a generic part
 919  *   of the key for internal nodes.
 920  *
 921  * - Leaf nodes contain terminal elements only now.
 922  *
 923  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
 924  *   historical search.  ASOF and INSERT are mutually exclusive.  When
 925  *   doing an as-of lookup btree_search() checks for a right-edge boundary
 926  *   case.  If while recursing down the left-edge differs from the key
 927  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
 928  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
 929  *   The iteration backwards because as-of searches can wind up going
 930  *   down the wrong branch of the B-Tree.
 931  */
 932 static
 933 int
 934 btree_search(hammer_cursor_t cursor, int flags)
 935 {
 936         hammer_node_ondisk_t node;
 937         hammer_btree_elm_t elm;
 938         int error;
 939         int enospc = 0;
 940         int i;
 941         int r;
 942         int s;
 943
 944         flags |= cursor->flags;
 945         ++hammer_stats_btree_searches;
 946
 947         if (hammer_debug_btree) {
 948                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
 949                         cursor->node->node_offset,
 950                         cursor->index,
 951                         cursor->key_beg.obj_id,
 952                         cursor->key_beg.rec_type,
 953                         cursor->key_beg.key,
 954                         cursor->key_beg.create_tid,
 955                         cursor->key_beg.localization,
 956                         curthread
 957                 );
 958                 if (cursor->parent)
 959                     kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
 960                         cursor->parent->node_offset, cursor->parent_index,
 961                         cursor->left_bound->obj_id,
 962                         cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
 963                         cursor->right_bound->obj_id,
 964                         cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
 965                         cursor->left_bound,
 966                         &cursor->parent->ondisk->elms[cursor->parent_index],
 967                         cursor->right_bound,
 968                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
 969                     );
 970         }
 971
 972         /*
 973          * Move our cursor up the tree until we find a node whos range covers
 974          * the key we are trying to locate.
 975          *
 976          * The left bound is inclusive, the right bound is non-inclusive.
 977          * It is ok to cursor up too far.
 978          */
 979         for (;;) {
 980                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
 981                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
 982                 if (r >= 0 && s < 0)
 983                         break;
 984                 KKASSERT(cursor->parent);
 985                 ++hammer_stats_btree_iterations;
 986                 error = hammer_cursor_up(cursor);
 987                 if (error)
 988                         goto done;
 989         }
 990
 991         /*
 992          * The delete-checks below are based on node, not parent.  Set the
 993          * initial delete-check based on the parent.
 994          */
 995         if (r == 1) {
 996                 KKASSERT(cursor->left_bound->create_tid != 1);
 997                 cursor->create_check = cursor->left_bound->create_tid - 1;
 998                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
 999         }
1000
1001         /*
1002          * We better have ended up with a node somewhere.
1003          */
1004         KKASSERT(cursor->node != NULL);
1005
1006         /*
1007          * If we are inserting we can't start at a full node if the parent
1008          * is also full (because there is no way to split the node),
1009          * continue running up the tree until the requirement is satisfied
1010          * or we hit the root of the filesystem.
1011          *
1012          * (If inserting we aren't doing an as-of search so we don't have
1013          *  to worry about create_check).
1014          */
1015         while ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1016                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
1017                         if (btree_node_is_full(cursor->node->ondisk) == 0)
1018                                 break;
1019                 } else {
1020                         if (btree_node_is_full(cursor->node->ondisk) ==0)
1021                                 break;
1022                 }
1023                 if (cursor->node->ondisk->parent == 0 ||
1024                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1025                         break;
1026                 }
1027                 ++hammer_stats_btree_iterations;
1028                 error = hammer_cursor_up(cursor);
1029                 /* node may have become stale */
1030                 if (error)
1031                         goto done;
1032         }
1033
1034         /*
1035          * Push down through internal nodes to locate the requested key.
1036          */
1037         node = cursor->node->ondisk;
1038         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1039                 /*
1040                  * Scan the node to find the subtree index to push down into.
1041                  * We go one-past, then back-up.
1042                  *
1043                  * We must proactively remove deleted elements which may
1044                  * have been left over from a deadlocked btree_remove().
1045                  *
1046                  * The left and right boundaries are included in the loop
1047                  * in order to detect edge cases.
1048                  *
1049                  * If the separator only differs by create_tid (r == 1)
1050                  * and we are doing an as-of search, we may end up going
1051                  * down a branch to the left of the one containing the
1052                  * desired key.  This requires numerous special cases.
1053                  */
1054                 ++hammer_stats_btree_iterations;
1055                 if (hammer_debug_btree) {
1056                         kprintf("SEARCH-I %016llx count=%d\n",
1057                                 cursor->node->node_offset,
1058                                 node->count);
1059                 }
1060
1061                 /*
1062                  * Try to shortcut the search before dropping into the
1063                  * linear loop.  Locate the first node where r <= 1.
1064                  */
1065                 i = hammer_btree_search_node(&cursor->key_beg, node);
1066                 while (i <= node->count) {
1067                         ++hammer_stats_btree_elements;
1068                         elm = &node->elms[i];
1069                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1070                         if (hammer_debug_btree > 2) {
1071                                 kprintf(" IELM %p %d r=%d\n",
1072                                         &node->elms[i], i, r);
1073                         }
1074                         if (r < 0)
1075                                 break;
1076                         if (r == 1) {
1077                                 KKASSERT(elm->base.create_tid != 1);
1078                                 cursor->create_check = elm->base.create_tid - 1;
1079                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1080                         }
1081                         ++i;
1082                 }
1083                 if (hammer_debug_btree) {
1084                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1085                                 i, node->count, r);
1086                 }
1087
1088                 /*
1089                  * These cases occur when the parent's idea of the boundary
1090                  * is wider then the child's idea of the boundary, and
1091                  * require special handling.  If not inserting we can
1092                  * terminate the search early for these cases but the
1093                  * child's boundaries cannot be unconditionally modified.
1094                  */
1095                 if (i == 0) {
1096                         /*
1097                          * If i == 0 the search terminated to the LEFT of the
1098                          * left_boundary but to the RIGHT of the parent's left
1099                          * boundary.
1100                          */
1101                         u_int8_t save;
1102
1103                         elm = &node->elms[0];
1104
1105                         /*
1106                          * If we aren't inserting we can stop here.
1107                          */
1108                         if ((flags & (HAMMER_CURSOR_INSERT |
1109                                       HAMMER_CURSOR_PRUNING)) == 0) {
1110                                 cursor->index = 0;
1111                                 return(ENOENT);
1112                         }
1113
1114                         /*
1115                          * Correct a left-hand boundary mismatch.
1116                          *
1117                          * We can only do this if we can upgrade the lock,
1118                          * and synchronized as a background cursor (i.e.
1119                          * inserting or pruning).
1120                          *
1121                          * WARNING: We can only do this if inserting, i.e.
1122                          * we are running on the backend.
1123                          */
1124                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1125                                 return(error);
1126                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1127                         hammer_modify_node_field(cursor->trans, cursor->node,
1128                                                  elms[0]);
1129                         save = node->elms[0].base.btype;
1130                         node->elms[0].base = *cursor->left_bound;
1131                         node->elms[0].base.btype = save;
1132                         hammer_modify_node_done(cursor->node);
1133                 } else if (i == node->count + 1) {
1134                         /*
1135                          * If i == node->count + 1 the search terminated to
1136                          * the RIGHT of the right boundary but to the LEFT
1137                          * of the parent's right boundary.  If we aren't
1138                          * inserting we can stop here.
1139                          *
1140                          * Note that the last element in this case is
1141                          * elms[i-2] prior to adjustments to 'i'.
1142                          */
1143                         --i;
1144                         if ((flags & (HAMMER_CURSOR_INSERT |
1145                                       HAMMER_CURSOR_PRUNING)) == 0) {
1146                                 cursor->index = i;
1147                                 return (ENOENT);
1148                         }
1149
1150                         /*
1151                          * Correct a right-hand boundary mismatch.
1152                          * (actual push-down record is i-2 prior to
1153                          * adjustments to i).
1154                          *
1155                          * We can only do this if we can upgrade the lock,
1156                          * and synchronized as a background cursor (i.e.
1157                          * inserting or pruning).
1158                          *
1159                          * WARNING: We can only do this if inserting, i.e.
1160                          * we are running on the backend.
1161                          */
1162                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1163                                 return(error);
1164                         elm = &node->elms[i];
1165                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1166                         hammer_modify_node(cursor->trans, cursor->node,
1167                                            &elm->base, sizeof(elm->base));
1168                         elm->base = *cursor->right_bound;
1169                         hammer_modify_node_done(cursor->node);
1170                         --i;
1171                 } else {
1172                         /*
1173                          * The push-down index is now i - 1.  If we had
1174                          * terminated on the right boundary this will point
1175                          * us at the last element.
1176                          */
1177                         --i;
1178                 }
1179                 cursor->index = i;
1180                 elm = &node->elms[i];
1181
1182                 if (hammer_debug_btree) {
1183                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1184                                 "key=%016llx cre=%016llx lo=%02x\n",
1185                                 cursor->node->node_offset,
1186                                 i,
1187                                 elm->internal.base.obj_id,
1188                                 elm->internal.base.rec_type,
1189                                 elm->internal.base.key,
1190                                 elm->internal.base.create_tid,
1191                                 elm->internal.base.localization
1192                         );
1193                 }
1194
1195                 /*
1196                  * We better have a valid subtree offset.
1197                  */
1198                 KKASSERT(elm->internal.subtree_offset != 0);
1199
1200                 /*
1201                  * Handle insertion and deletion requirements.
1202                  *
1203                  * If inserting split full nodes.  The split code will
1204                  * adjust cursor->node and cursor->index if the current
1205                  * index winds up in the new node.
1206                  *
1207                  * If inserting and a left or right edge case was detected,
1208                  * we cannot correct the left or right boundary and must
1209                  * prepend and append an empty leaf node in order to make
1210                  * the boundary correction.
1211                  *
1212                  * If we run out of space we set enospc and continue on
1213                  * to a leaf to provide the spike code with a good point
1214                  * of entry.
1215                  */
1216                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1217                         if (btree_node_is_full(node)) {
1218                                 error = btree_split_internal(cursor);
1219                                 if (error) {
1220                                         if (error != ENOSPC)
1221                                                 goto done;
1222                                         enospc = 1;
1223                                 }
1224                                 /*
1225                                  * reload stale pointers
1226                                  */
1227                                 i = cursor->index;
1228                                 node = cursor->node->ondisk;
1229                         }
1230                 }
1231
1232                 /*
1233                  * Push down (push into new node, existing node becomes
1234                  * the parent) and continue the search.
1235                  */
1236                 error = hammer_cursor_down(cursor);
1237                 /* node may have become stale */
1238                 if (error)
1239                         goto done;
1240                 node = cursor->node->ondisk;
1241         }
1242
1243         /*
1244          * We are at a leaf, do a linear search of the key array.
1245          *
1246          * On success the index is set to the matching element and 0
1247          * is returned.
1248          *
1249          * On failure the index is set to the insertion point and ENOENT
1250          * is returned.
1251          *
1252          * Boundaries are not stored in leaf nodes, so the index can wind
1253          * up to the left of element 0 (index == 0) or past the end of
1254          * the array (index == node->count).  It is also possible that the
1255          * leaf might be empty.
1256          */
1257         ++hammer_stats_btree_iterations;
1258         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1259         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1260         if (hammer_debug_btree) {
1261                 kprintf("SEARCH-L %016llx count=%d\n",
1262                         cursor->node->node_offset,
1263                         node->count);
1264         }
1265
1266         /*
1267          * Try to shortcut the search before dropping into the
1268          * linear loop.  Locate the first node where r <= 1.
1269          */
1270         i = hammer_btree_search_node(&cursor->key_beg, node);
1271         while (i < node->count) {
1272                 ++hammer_stats_btree_elements;
1273                 elm = &node->elms[i];
1274
1275                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1276
1277                 if (hammer_debug_btree > 1)
1278                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1279
1280                 /*
1281                  * We are at a record element.  Stop if we've flipped past
1282                  * key_beg, not counting the create_tid test.  Allow the
1283                  * r == 1 case (key_beg > element but differs only by its
1284                  * create_tid) to fall through to the AS-OF check.
1285                  */
1286                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1287
1288                 if (r < 0)
1289                         goto failed;
1290                 if (r > 1) {
1291                         ++i;
1292                         continue;
1293                 }
1294
1295                 /*
1296                  * Check our as-of timestamp against the element.
1297                  */
1298                 if (flags & HAMMER_CURSOR_ASOF) {
1299                         if (hammer_btree_chkts(cursor->asof,
1300                                                &node->elms[i].base) != 0) {
1301                                 ++i;
1302                                 continue;
1303                         }
1304                         /* success */
1305                 } else {
1306                         if (r > 0) {    /* can only be +1 */
1307                                 ++i;
1308                                 continue;
1309                         }
1310                         /* success */
1311                 }
1312                 cursor->index = i;
1313                 error = 0;
1314                 if (hammer_debug_btree) {
1315                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1316                                 cursor->node->node_offset, i);
1317                 }
1318                 goto done;
1319         }
1320
1321         /*
1322          * The search of the leaf node failed.  i is the insertion point.
1323          */
1324 failed:
1325         if (hammer_debug_btree) {
1326                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1327                         cursor->node->node_offset, i);
1328         }
1329
1330         /*
1331          * No exact match was found, i is now at the insertion point.
1332          *
1333          * If inserting split a full leaf before returning.  This
1334          * may have the side effect of adjusting cursor->node and
1335          * cursor->index.
1336          */
1337         cursor->index = i;
1338         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1339              btree_node_is_full(node)) {
1340                 error = btree_split_leaf(cursor);
1341                 if (error) {
1342                         if (error != ENOSPC)
1343                                 goto done;
1344                         enospc = 1;
1345                 }
1346                 /*
1347                  * reload stale pointers
1348                  */
1349                 /* NOT USED
1350                 i = cursor->index;
1351                 node = &cursor->node->internal;
1352                 */
1353         }
1354
1355         /*
1356          * We reached a leaf but did not find the key we were looking for.
1357          * If this is an insert we will be properly positioned for an insert
1358          * (ENOENT) or spike (ENOSPC) operation.
1359          */
1360         error = enospc ? ENOSPC : ENOENT;
1361 done:
1362         return(error);
1363 }
1364
1365 /*
1366  * Heuristical search for the first element whos comparison is <= 1.  May
1367  * return an index whos compare result is > 1 but may only return an index
1368  * whos compare result is <= 1 if it is the first element with that result.
1369  */
1370 int
1371 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1372 {
1373         int b;
1374         int s;
1375         int i;
1376         int r;
1377
1378         /*
1379          * Don't bother if the node does not have very many elements
1380          */
1381         b = 0;
1382         s = node->count;
1383         while (s - b > 4) {
1384                 i = b + (s - b) / 2;
1385                 ++hammer_stats_btree_elements;
1386                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1387                 if (r <= 1) {
1388                         s = i;
1389                 } else {
1390                         b = i;
1391                 }
1392         }
1393         return(b);
1394 }
1395
1396
1397 /************************************************************************
1398  *                         SPLITTING AND MERGING                        *
1399  ************************************************************************
1400  *
1401  * These routines do all the dirty work required to split and merge nodes.
1402  */
1403
1404 /*
1405  * Split an internal node into two nodes and move the separator at the split
1406  * point to the parent.
1407  *
1408  * (cursor->node, cursor->index) indicates the element the caller intends
1409  * to push into.  We will adjust node and index if that element winds
1410  * up in the split node.
1411  *
1412  * If we are at the root of the filesystem a new root must be created with
1413  * two elements, one pointing to the original root and one pointing to the
1414  * newly allocated split node.
1415  */
1416 static
1417 int
1418 btree_split_internal(hammer_cursor_t cursor)
1419 {
1420         hammer_node_ondisk_t ondisk;
1421         hammer_node_t node;
1422         hammer_node_t parent;
1423         hammer_node_t new_node;
1424         hammer_btree_elm_t elm;
1425         hammer_btree_elm_t parent_elm;
1426         struct hammer_node_lock lockroot;
1427         hammer_mount_t hmp = cursor->trans->hmp;
1428         int parent_index;
1429         int made_root;
1430         int split;
1431         int error;
1432         int i;
1433         const int esize = sizeof(*elm);
1434
1435         hammer_node_lock_init(&lockroot, cursor->node);
1436         error = hammer_btree_lock_children(cursor, 1, &lockroot);
1437         if (error)
1438                 goto done;
1439         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1440                 goto done;
1441         ++hammer_stats_btree_splits;
1442
1443         /*
1444          * We are splitting but elms[split] will be promoted to the parent,
1445          * leaving the right hand node with one less element.  If the
1446          * insertion point will be on the left-hand side adjust the split
1447          * point to give the right hand side one additional node.
1448          */
1449         node = cursor->node;
1450         ondisk = node->ondisk;
1451         split = (ondisk->count + 1) / 2;
1452         if (cursor->index <= split)
1453                 --split;
1454
1455         /*
1456          * If we are at the root of the filesystem, create a new root node
1457          * with 1 element and split normally.  Avoid making major
1458          * modifications until we know the whole operation will work.
1459          */
1460         if (ondisk->parent == 0) {
1461                 parent = hammer_alloc_btree(cursor->trans, &error);
1462                 if (parent == NULL)
1463                         goto done;
1464                 hammer_lock_ex(&parent->lock);
1465                 hammer_modify_node_noundo(cursor->trans, parent);
1466                 ondisk = parent->ondisk;
1467                 ondisk->count = 1;
1468                 ondisk->parent = 0;
1469                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1470                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1471                 ondisk->elms[0].base = hmp->root_btree_beg;
1472                 ondisk->elms[0].base.btype = node->ondisk->type;
1473                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1474                 ondisk->elms[1].base = hmp->root_btree_end;
1475                 hammer_modify_node_done(parent);
1476                 /* ondisk->elms[1].base.btype - not used */
1477                 made_root = 1;
1478                 parent_index = 0;       /* index of current node in parent */
1479         } else {
1480                 made_root = 0;
1481                 parent = cursor->parent;
1482                 parent_index = cursor->parent_index;
1483         }
1484
1485         /*
1486          * Split node into new_node at the split point.
1487          *
1488          *  B O O O P N N B     <-- P = node->elms[split]
1489          *   0 1 2 3 4 5 6      <-- subtree indices
1490          *
1491          *       x x P x x
1492          *        s S S s
1493          *         /   \
1494          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1495          *   0 1 2 3      4 5 6
1496          *
1497          */
1498         new_node = hammer_alloc_btree(cursor->trans, &error);
1499         if (new_node == NULL) {
1500                 if (made_root) {
1501                         hammer_unlock(&parent->lock);
1502                         hammer_delete_node(cursor->trans, parent);
1503                         hammer_rel_node(parent);
1504                 }
1505                 goto done;
1506         }
1507         hammer_lock_ex(&new_node->lock);
1508
1509         /*
1510          * Create the new node.  P becomes the left-hand boundary in the
1511          * new node.  Copy the right-hand boundary as well.
1512          *
1513          * elm is the new separator.
1514          */
1515         hammer_modify_node_noundo(cursor->trans, new_node);
1516         hammer_modify_node_all(cursor->trans, node);
1517         ondisk = node->ondisk;
1518         elm = &ondisk->elms[split];
1519         bcopy(elm, &new_node->ondisk->elms[0],
1520               (ondisk->count - split + 1) * esize);
1521         new_node->ondisk->count = ondisk->count - split;
1522         new_node->ondisk->parent = parent->node_offset;
1523         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1524         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1525         KKASSERT(ondisk->type == new_node->ondisk->type);
1526         hammer_cursor_split_node(node, new_node, split);
1527
1528         /*
1529          * Cleanup the original node.  Elm (P) becomes the new boundary,
1530          * its subtree_offset was moved to the new node.  If we had created
1531          * a new root its parent pointer may have changed.
1532          */
1533         elm->internal.subtree_offset = 0;
1534         ondisk->count = split;
1535
1536         /*
1537          * Insert the separator into the parent, fixup the parent's
1538          * reference to the original node, and reference the new node.
1539          * The separator is P.
1540          *
1541          * Remember that base.count does not include the right-hand boundary.
1542          */
1543         hammer_modify_node_all(cursor->trans, parent);
1544         ondisk = parent->ondisk;
1545         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1546         parent_elm = &ondisk->elms[parent_index+1];
1547         bcopy(parent_elm, parent_elm + 1,
1548               (ondisk->count - parent_index) * esize);
1549         parent_elm->internal.base = elm->base;  /* separator P */
1550         parent_elm->internal.base.btype = new_node->ondisk->type;
1551         parent_elm->internal.subtree_offset = new_node->node_offset;
1552         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1553         ++ondisk->count;
1554         hammer_modify_node_done(parent);
1555         hammer_cursor_inserted_element(parent, parent_index + 1);
1556
1557         /*
1558          * The children of new_node need their parent pointer set to new_node.
1559          * The children have already been locked by
1560          * hammer_btree_lock_children().
1561          */
1562         for (i = 0; i < new_node->ondisk->count; ++i) {
1563                 elm = &new_node->ondisk->elms[i];
1564                 error = btree_set_parent(cursor->trans, new_node, elm);
1565                 if (error) {
1566                         panic("btree_split_internal: btree-fixup problem");
1567                 }
1568         }
1569         hammer_modify_node_done(new_node);
1570
1571         /*
1572          * The filesystem's root B-Tree pointer may have to be updated.
1573          */
1574         if (made_root) {
1575                 hammer_volume_t volume;
1576
1577                 volume = hammer_get_root_volume(hmp, &error);
1578                 KKASSERT(error == 0);
1579
1580                 hammer_modify_volume_field(cursor->trans, volume,
1581                                            vol0_btree_root);
1582                 volume->ondisk->vol0_btree_root = parent->node_offset;
1583                 hammer_modify_volume_done(volume);
1584                 node->ondisk->parent = parent->node_offset;
1585                 if (cursor->parent) {
1586                         hammer_unlock(&cursor->parent->lock);
1587                         hammer_rel_node(cursor->parent);
1588                 }
1589                 cursor->parent = parent;        /* lock'd and ref'd */
1590                 hammer_rel_volume(volume, 0);
1591         }
1592         hammer_modify_node_done(node);
1593
1594         /*
1595          * Ok, now adjust the cursor depending on which element the original
1596          * index was pointing at.  If we are >= the split point the push node
1597          * is now in the new node.
1598          *
1599          * NOTE: If we are at the split point itself we cannot stay with the
1600          * original node because the push index will point at the right-hand
1601          * boundary, which is illegal.
1602          *
1603          * NOTE: The cursor's parent or parent_index must be adjusted for
1604          * the case where a new parent (new root) was created, and the case
1605          * where the cursor is now pointing at the split node.
1606          */
1607         if (cursor->index >= split) {
1608                 cursor->parent_index = parent_index + 1;
1609                 cursor->index -= split;
1610                 hammer_unlock(&cursor->node->lock);
1611                 hammer_rel_node(cursor->node);
1612                 cursor->node = new_node;        /* locked and ref'd */
1613         } else {
1614                 cursor->parent_index = parent_index;
1615                 hammer_unlock(&new_node->lock);
1616                 hammer_rel_node(new_node);
1617         }
1618
1619         /*
1620          * Fixup left and right bounds
1621          */
1622         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1623         cursor->left_bound = &parent_elm[0].internal.base;
1624         cursor->right_bound = &parent_elm[1].internal.base;
1625         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1626                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1627         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1628                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1629
1630 done:
1631         hammer_btree_unlock_children(cursor, &lockroot);
1632         hammer_cursor_downgrade(cursor);
1633         return (error);
1634 }
1635
1636 /*
1637  * Same as the above, but splits a full leaf node.
1638  *
1639  * This function
1640  */
1641 static
1642 int
1643 btree_split_leaf(hammer_cursor_t cursor)
1644 {
1645         hammer_node_ondisk_t ondisk;
1646         hammer_node_t parent;
1647         hammer_node_t leaf;
1648         hammer_mount_t hmp;
1649         hammer_node_t new_leaf;
1650         hammer_btree_elm_t elm;
1651         hammer_btree_elm_t parent_elm;
1652         hammer_base_elm_t mid_boundary;
1653         int parent_index;
1654         int made_root;
1655         int split;
1656         int error;
1657         const size_t esize = sizeof(*elm);
1658
1659         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1660                 return(error);
1661         ++hammer_stats_btree_splits;
1662
1663         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1664                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1665         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1666                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1667
1668         /*
1669          * Calculate the split point.  If the insertion point will be on
1670          * the left-hand side adjust the split point to give the right
1671          * hand side one additional node.
1672          *
1673          * Spikes are made up of two leaf elements which cannot be
1674          * safely split.
1675          */
1676         leaf = cursor->node;
1677         ondisk = leaf->ondisk;
1678         split = (ondisk->count + 1) / 2;
1679         if (cursor->index <= split)
1680                 --split;
1681         error = 0;
1682         hmp = leaf->hmp;
1683
1684         elm = &ondisk->elms[split];
1685
1686         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1687         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1688         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1689         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1690
1691         /*
1692          * If we are at the root of the tree, create a new root node with
1693          * 1 element and split normally.  Avoid making major modifications
1694          * until we know the whole operation will work.
1695          */
1696         if (ondisk->parent == 0) {
1697                 parent = hammer_alloc_btree(cursor->trans, &error);
1698                 if (parent == NULL)
1699                         goto done;
1700                 hammer_lock_ex(&parent->lock);
1701                 hammer_modify_node_noundo(cursor->trans, parent);
1702                 ondisk = parent->ondisk;
1703                 ondisk->count = 1;
1704                 ondisk->parent = 0;
1705                 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1706                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1707                 ondisk->elms[0].base = hmp->root_btree_beg;
1708                 ondisk->elms[0].base.btype = leaf->ondisk->type;
1709                 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1710                 ondisk->elms[1].base = hmp->root_btree_end;
1711                 /* ondisk->elms[1].base.btype = not used */
1712                 hammer_modify_node_done(parent);
1713                 made_root = 1;
1714                 parent_index = 0;       /* insertion point in parent */
1715         } else {
1716                 made_root = 0;
1717                 parent = cursor->parent;
1718                 parent_index = cursor->parent_index;
1719         }
1720
1721         /*
1722          * Split leaf into new_leaf at the split point.  Select a separator
1723          * value in-between the two leafs but with a bent towards the right
1724          * leaf since comparisons use an 'elm >= separator' inequality.
1725          *
1726          *  L L L L L L L L
1727          *
1728          *       x x P x x
1729          *        s S S s
1730          *         /   \
1731          *  L L L L     L L L L
1732          */
1733         new_leaf = hammer_alloc_btree(cursor->trans, &error);
1734         if (new_leaf == NULL) {
1735                 if (made_root) {
1736                         hammer_unlock(&parent->lock);
1737                         hammer_delete_node(cursor->trans, parent);
1738                         hammer_rel_node(parent);
1739                 }
1740                 goto done;
1741         }
1742         hammer_lock_ex(&new_leaf->lock);
1743
1744         /*
1745          * Create the new node and copy the leaf elements from the split
1746          * point on to the new node.
1747          */
1748         hammer_modify_node_all(cursor->trans, leaf);
1749         hammer_modify_node_noundo(cursor->trans, new_leaf);
1750         ondisk = leaf->ondisk;
1751         elm = &ondisk->elms[split];
1752         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1753         new_leaf->ondisk->count = ondisk->count - split;
1754         new_leaf->ondisk->parent = parent->node_offset;
1755         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1756         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1757         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1758         hammer_modify_node_done(new_leaf);
1759         hammer_cursor_split_node(leaf, new_leaf, split);
1760
1761         /*
1762          * Cleanup the original node.  Because this is a leaf node and
1763          * leaf nodes do not have a right-hand boundary, there
1764          * aren't any special edge cases to clean up.  We just fixup the
1765          * count.
1766          */
1767         ondisk->count = split;
1768
1769         /*
1770          * Insert the separator into the parent, fixup the parent's
1771          * reference to the original node, and reference the new node.
1772          * The separator is P.
1773          *
1774          * Remember that base.count does not include the right-hand boundary.
1775          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1776          */
1777         hammer_modify_node_all(cursor->trans, parent);
1778         ondisk = parent->ondisk;
1779         KKASSERT(split != 0);
1780         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1781         parent_elm = &ondisk->elms[parent_index+1];
1782         bcopy(parent_elm, parent_elm + 1,
1783               (ondisk->count - parent_index) * esize);
1784
1785         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1786         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1787         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1788         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1789         mid_boundary = &parent_elm->base;
1790         ++ondisk->count;
1791         hammer_modify_node_done(parent);
1792         hammer_cursor_inserted_element(parent, parent_index + 1);
1793
1794         /*
1795          * The filesystem's root B-Tree pointer may have to be updated.
1796          */
1797         if (made_root) {
1798                 hammer_volume_t volume;
1799
1800                 volume = hammer_get_root_volume(hmp, &error);
1801                 KKASSERT(error == 0);
1802
1803                 hammer_modify_volume_field(cursor->trans, volume,
1804                                            vol0_btree_root);
1805                 volume->ondisk->vol0_btree_root = parent->node_offset;
1806                 hammer_modify_volume_done(volume);
1807                 leaf->ondisk->parent = parent->node_offset;
1808                 if (cursor->parent) {
1809                         hammer_unlock(&cursor->parent->lock);
1810                         hammer_rel_node(cursor->parent);
1811                 }
1812                 cursor->parent = parent;        /* lock'd and ref'd */
1813                 hammer_rel_volume(volume, 0);
1814         }
1815         hammer_modify_node_done(leaf);
1816
1817         /*
1818          * Ok, now adjust the cursor depending on which element the original
1819          * index was pointing at.  If we are >= the split point the push node
1820          * is now in the new node.
1821          *
1822          * NOTE: If we are at the split point itself we need to select the
1823          * old or new node based on where key_beg's insertion point will be.
1824          * If we pick the wrong side the inserted element will wind up in
1825          * the wrong leaf node and outside that node's bounds.
1826          */
1827         if (cursor->index > split ||
1828             (cursor->index == split &&
1829              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1830                 cursor->parent_index = parent_index + 1;
1831                 cursor->index -= split;
1832                 hammer_unlock(&cursor->node->lock);
1833                 hammer_rel_node(cursor->node);
1834                 cursor->node = new_leaf;
1835         } else {
1836                 cursor->parent_index = parent_index;
1837                 hammer_unlock(&new_leaf->lock);
1838                 hammer_rel_node(new_leaf);
1839         }
1840
1841         /*
1842          * Fixup left and right bounds
1843          */
1844         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1845         cursor->left_bound = &parent_elm[0].internal.base;
1846         cursor->right_bound = &parent_elm[1].internal.base;
1847
1848         /*
1849          * Assert that the bounds are correct.
1850          */
1851         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1852                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1853         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1854                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1855         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
1856         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
1857
1858 done:
1859         hammer_cursor_downgrade(cursor);
1860         return (error);
1861 }
1862
1863 #if 0
1864
1865 /*
1866  * Recursively correct the right-hand boundary's create_tid to (tid) as
1867  * long as the rest of the key matches.  We have to recurse upward in
1868  * the tree as well as down the left side of each parent's right node.
1869  *
1870  * Return EDEADLK if we were only partially successful, forcing the caller
1871  * to try again.  The original cursor is not modified.  This routine can
1872  * also fail with EDEADLK if it is forced to throw away a portion of its
1873  * record history.
1874  *
1875  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
1876  */
1877 struct hammer_rhb {
1878         TAILQ_ENTRY(hammer_rhb) entry;
1879         hammer_node_t   node;
1880         int             index;
1881 };
1882
1883 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
1884
1885 int
1886 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
1887 {
1888         struct hammer_mount *hmp;
1889         struct hammer_rhb_list rhb_list;
1890         hammer_base_elm_t elm;
1891         hammer_node_t orig_node;
1892         struct hammer_rhb *rhb;
1893         int orig_index;
1894         int error;
1895
1896         TAILQ_INIT(&rhb_list);
1897         hmp = cursor->trans->hmp;
1898
1899         /*
1900          * Save our position so we can restore it on return.  This also
1901          * gives us a stable 'elm'.
1902          */
1903         orig_node = cursor->node;
1904         hammer_ref_node(orig_node);
1905         hammer_lock_sh(&orig_node->lock);
1906         orig_index = cursor->index;
1907         elm = &orig_node->ondisk->elms[orig_index].base;
1908
1909         /*
1910          * Now build a list of parents going up, allocating a rhb
1911          * structure for each one.
1912          */
1913         while (cursor->parent) {
1914                 /*
1915                  * Stop if we no longer have any right-bounds to fix up
1916                  */
1917                 if (elm->obj_id != cursor->right_bound->obj_id ||
1918                     elm->rec_type != cursor->right_bound->rec_type ||
1919                     elm->key != cursor->right_bound->key) {
1920                         break;
1921                 }
1922
1923                 /*
1924                  * Stop if the right-hand bound's create_tid does not
1925                  * need to be corrected.
1926                  */
1927                 if (cursor->right_bound->create_tid >= tid)
1928                         break;
1929
1930                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
1931                 rhb->node = cursor->parent;
1932                 rhb->index = cursor->parent_index;
1933                 hammer_ref_node(rhb->node);
1934                 hammer_lock_sh(&rhb->node->lock);
1935                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
1936
1937                 hammer_cursor_up(cursor);
1938         }
1939
1940         /*
1941          * now safely adjust the right hand bound for each rhb.  This may
1942          * also require taking the right side of the tree and iterating down
1943          * ITS left side.
1944          */
1945         error = 0;
1946         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
1947                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
1948                 if (error)
1949                         break;
1950                 TAILQ_REMOVE(&rhb_list, rhb, entry);
1951                 hammer_unlock(&rhb->node->lock);
1952                 hammer_rel_node(rhb->node);
1953                 kfree(rhb, hmp->m_misc);
1954
1955                 switch (cursor->node->ondisk->type) {
1956                 case HAMMER_BTREE_TYPE_INTERNAL:
1957                         /*
1958                          * Right-boundary for parent at internal node
1959                          * is one element to the right of the element whos
1960                          * right boundary needs adjusting.  We must then
1961                          * traverse down the left side correcting any left
1962                          * bounds (which may now be too far to the left).
1963                          */
1964                         ++cursor->index;
1965                         error = hammer_btree_correct_lhb(cursor, tid);
1966                         break;
1967                 default:
1968                         panic("hammer_btree_correct_rhb(): Bad node type");
1969                         error = EINVAL;
1970                         break;
1971                 }
1972         }
1973
1974         /*
1975          * Cleanup
1976          */
1977         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
1978                 TAILQ_REMOVE(&rhb_list, rhb, entry);
1979                 hammer_unlock(&rhb->node->lock);
1980                 hammer_rel_node(rhb->node);
1981                 kfree(rhb, hmp->m_misc);
1982         }
1983         error = hammer_cursor_seek(cursor, orig_node, orig_index);
1984         hammer_unlock(&orig_node->lock);
1985         hammer_rel_node(orig_node);
1986         return (error);
1987 }
1988
1989 /*
1990  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
1991  * bound going downward starting at the current cursor position.
1992  *
1993  * This function does not restore the cursor after use.
1994  */
1995 int
1996 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
1997 {
1998         struct hammer_rhb_list rhb_list;
1999         hammer_base_elm_t elm;
2000         hammer_base_elm_t cmp;
2001         struct hammer_rhb *rhb;
2002         struct hammer_mount *hmp;
2003         int error;
2004
2005         TAILQ_INIT(&rhb_list);
2006         hmp = cursor->trans->hmp;
2007
2008         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2009
2010         /*
2011          * Record the node and traverse down the left-hand side for all
2012          * matching records needing a boundary correction.
2013          */
2014         error = 0;
2015         for (;;) {
2016                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2017                 rhb->node = cursor->node;
2018                 rhb->index = cursor->index;
2019                 hammer_ref_node(rhb->node);
2020                 hammer_lock_sh(&rhb->node->lock);
2021                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2022
2023                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2024                         /*
2025                          * Nothing to traverse down if we are at the right
2026                          * boundary of an internal node.
2027                          */
2028                         if (cursor->index == cursor->node->ondisk->count)
2029                                 break;
2030                 } else {
2031                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2032                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2033                                 break;
2034                         panic("Illegal leaf record type %02x", elm->btype);
2035                 }
2036                 error = hammer_cursor_down(cursor);
2037                 if (error)
2038                         break;
2039
2040                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2041                 if (elm->obj_id != cmp->obj_id ||
2042                     elm->rec_type != cmp->rec_type ||
2043                     elm->key != cmp->key) {
2044                         break;
2045                 }
2046                 if (elm->create_tid >= tid)
2047                         break;
2048
2049         }
2050
2051         /*
2052          * Now we can safely adjust the left-hand boundary from the bottom-up.
2053          * The last element we remove from the list is the caller's right hand
2054          * boundary, which must also be adjusted.
2055          */
2056         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2057                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2058                 if (error)
2059                         break;
2060                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2061                 hammer_unlock(&rhb->node->lock);
2062                 hammer_rel_node(rhb->node);
2063                 kfree(rhb, hmp->m_misc);
2064
2065                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2066                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2067                         hammer_modify_node(cursor->trans, cursor->node,
2068                                            &elm->create_tid,
2069                                            sizeof(elm->create_tid));
2070                         elm->create_tid = tid;
2071                         hammer_modify_node_done(cursor->node);
2072                 } else {
2073                         panic("hammer_btree_correct_lhb(): Bad element type");
2074                 }
2075         }
2076
2077         /*
2078          * Cleanup
2079          */
2080         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2081                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2082                 hammer_unlock(&rhb->node->lock);
2083                 hammer_rel_node(rhb->node);
2084                 kfree(rhb, hmp->m_misc);
2085         }
2086         return (error);
2087 }
2088
2089 #endif
2090
2091 /*
2092  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2093  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2094  * the operation due to a deadlock, or some other error.
2095  *
2096  * This routine is initially called with an empty leaf and may be
2097  * recursively called with single-element internal nodes.
2098  *
2099  * It should also be noted that when removing empty leaves we must be sure
2100  * to test and update mirror_tid because another thread may have deadlocked
2101  * against us (or someone) trying to propagate it up and cannot retry once
2102  * the node has been deleted.
2103  *
2104  * On return the cursor may end up pointing to an internal node, suitable
2105  * for further iteration but not for an immediate insertion or deletion.
2106  */
2107 static int
2108 btree_remove(hammer_cursor_t cursor)
2109 {
2110         hammer_node_ondisk_t ondisk;
2111         hammer_btree_elm_t elm;
2112         hammer_node_t node;
2113         hammer_node_t parent;
2114         const int esize = sizeof(*elm);
2115         int error;
2116
2117         node = cursor->node;
2118
2119         /*
2120          * When deleting the root of the filesystem convert it to
2121          * an empty leaf node.  Internal nodes cannot be empty.
2122          */
2123         ondisk = node->ondisk;
2124         if (ondisk->parent == 0) {
2125                 KKASSERT(cursor->parent == NULL);
2126                 hammer_modify_node_all(cursor->trans, node);
2127                 KKASSERT(ondisk == node->ondisk);
2128                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2129                 ondisk->count = 0;
2130                 hammer_modify_node_done(node);
2131                 cursor->index = 0;
2132                 return(0);
2133         }
2134
2135         parent = cursor->parent;
2136         hammer_cursor_removed_node(node, parent, cursor->parent_index);
2137
2138         /*
2139          * Attempt to remove the parent's reference to the child.  If the
2140          * parent would become empty we have to recurse.  If we fail we
2141          * leave the parent pointing to an empty leaf node.
2142          *
2143          * We have to recurse successfully before we can delete the internal
2144          * node as it is illegal to have empty internal nodes.  Even though
2145          * the operation may be aborted we must still fixup any unlocked
2146          * cursors as if we had deleted the element prior to recursing
2147          * (by calling hammer_cursor_deleted_element()) so those cursors
2148          * are properly forced up the chain by the recursion.
2149          */
2150         if (parent->ondisk->count == 1) {
2151                 /*
2152                  * This special cursor_up_locked() call leaves the original
2153                  * node exclusively locked and referenced, leaves the
2154                  * original parent locked (as the new node), and locks the
2155                  * new parent.  It can return EDEADLK.
2156                  */
2157                 error = hammer_cursor_up_locked(cursor);
2158                 if (error == 0) {
2159                         hammer_cursor_deleted_element(cursor->node, 0);
2160                         error = btree_remove(cursor);
2161                         if (error == 0) {
2162                                 hammer_modify_node_all(cursor->trans, node);
2163                                 ondisk = node->ondisk;
2164                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2165                                 ondisk->count = 0;
2166                                 hammer_modify_node_done(node);
2167                                 hammer_flush_node(node);
2168                                 hammer_delete_node(cursor->trans, node);
2169                         } else {
2170                                 /*
2171                                  * Defer parent removal because we could not
2172                                  * get the lock, just let the leaf remain
2173                                  * empty.
2174                                  */
2175                                 /**/
2176                         }
2177                         hammer_unlock(&node->lock);
2178                         hammer_rel_node(node);
2179                 } else {
2180                         /*
2181                          * Defer parent removal because we could not
2182                          * get the lock, just let the leaf remain
2183                          * empty.
2184                          */
2185                         /**/
2186                 }
2187         } else {
2188                 KKASSERT(parent->ondisk->count > 1);
2189
2190                 hammer_modify_node_all(cursor->trans, parent);
2191                 ondisk = parent->ondisk;
2192                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2193
2194                 elm = &ondisk->elms[cursor->parent_index];
2195                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2196                 KKASSERT(ondisk->count > 0);
2197
2198                 /*
2199                  * We must retain the highest mirror_tid.  The deleted
2200                  * range is now encompassed by the element to the left.
2201                  * If we are already at the left edge the new left edge
2202                  * inherits mirror_tid.
2203                  *
2204                  * Note that bounds of the parent to our parent may create
2205                  * a gap to the left of our left-most node or to the right
2206                  * of our right-most node.  The gap is silently included
2207                  * in the mirror_tid's area of effect from the point of view
2208                  * of the scan.
2209                  */
2210                 if (cursor->parent_index) {
2211                         if (elm[-1].internal.mirror_tid <
2212                             elm[0].internal.mirror_tid) {
2213                                 elm[-1].internal.mirror_tid =
2214                                     elm[0].internal.mirror_tid;
2215                         }
2216                 } else {
2217                         if (elm[1].internal.mirror_tid <
2218                             elm[0].internal.mirror_tid) {
2219                                 elm[1].internal.mirror_tid =
2220                                     elm[0].internal.mirror_tid;
2221                         }
2222                 }
2223
2224                 /*
2225                  * Delete the subtree reference in the parent
2226                  */
2227                 bcopy(&elm[1], &elm[0],
2228                       (ondisk->count - cursor->parent_index) * esize);
2229                 --ondisk->count;
2230                 hammer_modify_node_done(parent);
2231                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2232                 hammer_flush_node(node);
2233                 hammer_delete_node(cursor->trans, node);
2234
2235                 /*
2236                  * cursor->node is invalid, cursor up to make the cursor
2237                  * valid again.
2238                  */
2239                 error = hammer_cursor_up(cursor);
2240         }
2241         return (error);
2242 }
2243
2244 /*
2245  * Propagate cursor->trans->tid up the B-Tree starting at the current
2246  * cursor position using pseudofs info gleaned from the passed inode.
2247  *
2248  * The passed inode has no relationship to the cursor position other
2249  * then being in the same pseudofs as the insertion or deletion we
2250  * are propagating the mirror_tid for.
2251  */
2252 void
2253 hammer_btree_do_propagation(hammer_cursor_t cursor,
2254                             hammer_pseudofs_inmem_t pfsm,
2255                             hammer_btree_leaf_elm_t leaf)
2256 {
2257         hammer_cursor_t ncursor;
2258         hammer_tid_t mirror_tid;
2259         int error;
2260
2261         /*
2262          * We do not propagate a mirror_tid if the filesystem was mounted
2263          * in no-mirror mode.
2264          */
2265         if (cursor->trans->hmp->master_id < 0)
2266                 return;
2267
2268         /*
2269          * This is a bit of a hack because we cannot deadlock or return
2270          * EDEADLK here.  The related operation has already completed and
2271          * we must propagate the mirror_tid now regardless.
2272          *
2273          * Generate a new cursor which inherits the original's locks and
2274          * unlock the original.  Use the new cursor to propagate the
2275          * mirror_tid.  Then clean up the new cursor and reacquire locks
2276          * on the original.
2277          *
2278          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2279          * original's locks and the original is tracked and must be
2280          * re-locked.
2281          */
2282         mirror_tid = cursor->node->ondisk->mirror_tid;
2283         KKASSERT(mirror_tid != 0);
2284         ncursor = hammer_push_cursor(cursor);
2285         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2286         KKASSERT(error == 0);
2287         hammer_pop_cursor(cursor, ncursor);
2288 }
2289
2290
2291 /*
2292  * Propagate a mirror TID update upwards through the B-Tree to the root.
2293  *
2294  * A locked internal node must be passed in.  The node will remain locked
2295  * on return.
2296  *
2297  * This function syncs mirror_tid at the specified internal node's element,
2298  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2299  */
2300 static int
2301 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2302 {
2303         hammer_btree_internal_elm_t elm;
2304         hammer_node_t node;
2305         int error;
2306
2307         for (;;) {
2308                 error = hammer_cursor_up(cursor);
2309                 if (error == 0)
2310                         error = hammer_cursor_upgrade(cursor);
2311                 while (error == EDEADLK) {
2312                         hammer_recover_cursor(cursor);
2313                         error = hammer_cursor_upgrade(cursor);
2314                 }
2315                 if (error)
2316                         break;
2317                 node = cursor->node;
2318                 KKASSERT (node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2319
2320                 /*
2321                  * Adjust the node's element
2322                  */
2323                 elm = &node->ondisk->elms[cursor->index].internal;
2324                 if (elm->mirror_tid >= mirror_tid)
2325                         break;
2326                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2327                                    sizeof(elm->mirror_tid));
2328                 elm->mirror_tid = mirror_tid;
2329                 hammer_modify_node_done(node);
2330                 if (hammer_debug_general & 0x0002) {
2331                         kprintf("mirror_propagate: propagate "
2332                                 "%016llx @%016llx:%d\n",
2333                                 mirror_tid, node->node_offset, cursor->index);
2334                 }
2335
2336
2337                 /*
2338                  * Adjust the node's mirror_tid aggregator
2339                  */
2340                 if (node->ondisk->mirror_tid >= mirror_tid)
2341                         return(0);
2342                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2343                 node->ondisk->mirror_tid = mirror_tid;
2344                 hammer_modify_node_done(node);
2345                 if (hammer_debug_general & 0x0002) {
2346                         kprintf("mirror_propagate: propagate "
2347                                 "%016llx @%016llx\n",
2348                                 mirror_tid, node->node_offset);
2349                 }
2350         }
2351         if (error == ENOENT)
2352                 error = 0;
2353         return(error);
2354 }
2355
2356 hammer_node_t
2357 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2358                         int *parent_indexp, int *errorp, int try_exclusive)
2359 {
2360         hammer_node_t parent;
2361         hammer_btree_elm_t elm;
2362         int i;
2363
2364         /*
2365          * Get the node
2366          */
2367         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2368         if (*errorp) {
2369                 KKASSERT(parent == NULL);
2370                 return(NULL);
2371         }
2372         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2373
2374         /*
2375          * Lock the node
2376          */
2377         if (try_exclusive) {
2378                 if (hammer_lock_ex_try(&parent->lock)) {
2379                         hammer_rel_node(parent);
2380                         *errorp = EDEADLK;
2381                         return(NULL);
2382                 }
2383         } else {
2384                 hammer_lock_sh(&parent->lock);
2385         }
2386
2387         /*
2388          * Figure out which element in the parent is pointing to the
2389          * child.
2390          */
2391         if (node->ondisk->count) {
2392                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2393                                              parent->ondisk);
2394         } else {
2395                 i = 0;
2396         }
2397         while (i < parent->ondisk->count) {
2398                 elm = &parent->ondisk->elms[i];
2399                 if (elm->internal.subtree_offset == node->node_offset)
2400                         break;
2401                 ++i;
2402         }
2403         if (i == parent->ondisk->count) {
2404                 hammer_unlock(&parent->lock);
2405                 panic("Bad B-Tree link: parent %p node %p\n", parent, node);
2406         }
2407         *parent_indexp = i;
2408         KKASSERT(*errorp == 0);
2409         return(parent);
2410 }
2411
2412 /*
2413  * The element (elm) has been moved to a new internal node (node).
2414  *
2415  * If the element represents a pointer to an internal node that node's
2416  * parent must be adjusted to the element's new location.
2417  *
2418  * XXX deadlock potential here with our exclusive locks
2419  */
2420 int
2421 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2422                  hammer_btree_elm_t elm)
2423 {
2424         hammer_node_t child;
2425         int error;
2426
2427         error = 0;
2428
2429         switch(elm->base.btype) {
2430         case HAMMER_BTREE_TYPE_INTERNAL:
2431         case HAMMER_BTREE_TYPE_LEAF:
2432                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2433                                         0, &error);
2434                 if (error == 0) {
2435                         hammer_modify_node_field(trans, child, parent);
2436                         child->ondisk->parent = node->node_offset;
2437                         hammer_modify_node_done(child);
2438                         hammer_rel_node(child);
2439                 }
2440                 break;
2441         default:
2442                 break;
2443         }
2444         return(error);
2445 }
2446
2447 /*
2448  * Initialize the root of a recursive B-Tree node lock list structure.
2449  */
2450 void
2451 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2452 {
2453         TAILQ_INIT(&parent->list);
2454         parent->parent = NULL;
2455         parent->node = node;
2456         parent->index = -1;
2457         parent->count = node->ondisk->count;
2458         parent->copy = NULL;
2459         parent->flags = 0;
2460 }
2461
2462 /*
2463  * Exclusively lock all the children of node.  This is used by the split
2464  * code to prevent anyone from accessing the children of a cursor node
2465  * while we fix-up its parent offset.
2466  *
2467  * If we don't lock the children we can really mess up cursors which block
2468  * trying to cursor-up into our node.
2469  *
2470  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2471  * error is returned the cursor is adjusted to block on termination.
2472  *
2473  * The caller is responsible for managing parent->node, the root's node
2474  * is usually aliased from a cursor.
2475  */
2476 int
2477 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2478                            hammer_node_lock_t parent)
2479 {
2480         hammer_node_t node;
2481         hammer_node_lock_t item;
2482         hammer_node_ondisk_t ondisk;
2483         hammer_btree_elm_t elm;
2484         hammer_node_t child;
2485         struct hammer_mount *hmp;
2486         int error;
2487         int i;
2488
2489         node = parent->node;
2490         ondisk = node->ondisk;
2491         error = 0;
2492         hmp = cursor->trans->hmp;
2493
2494         /*
2495          * We really do not want to block on I/O with exclusive locks held,
2496          * pre-get the children before trying to lock the mess.  This is
2497          * only done one-level deep for now.
2498          */
2499         for (i = 0; i < ondisk->count; ++i) {
2500                 ++hammer_stats_btree_elements;
2501                 elm = &ondisk->elms[i];
2502                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2503                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2504                         continue;
2505                 }
2506                 child = hammer_get_node(cursor->trans,
2507                                         elm->internal.subtree_offset,
2508                                         0, &error);
2509                 if (child)
2510                         hammer_rel_node(child);
2511         }
2512
2513         /*
2514          * Do it for real
2515          */
2516         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2517                 ++hammer_stats_btree_elements;
2518                 elm = &ondisk->elms[i];
2519
2520                 switch(elm->base.btype) {
2521                 case HAMMER_BTREE_TYPE_INTERNAL:
2522                 case HAMMER_BTREE_TYPE_LEAF:
2523                         KKASSERT(elm->internal.subtree_offset != 0);
2524                         child = hammer_get_node(cursor->trans,
2525                                                 elm->internal.subtree_offset,
2526                                                 0, &error);
2527                         break;
2528                 default:
2529                         child = NULL;
2530                         break;
2531                 }
2532                 if (child) {
2533                         if (hammer_lock_ex_try(&child->lock) != 0) {
2534                                 if (cursor->deadlk_node == NULL) {
2535                                         cursor->deadlk_node = child;
2536                                         hammer_ref_node(cursor->deadlk_node);
2537                                 }
2538                                 error = EDEADLK;
2539                                 hammer_rel_node(child);
2540                         } else {
2541                                 item = kmalloc(sizeof(*item), hmp->m_misc,
2542                                                M_WAITOK|M_ZERO);
2543                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2544                                 TAILQ_INIT(&item->list);
2545                                 item->parent = parent;
2546                                 item->node = child;
2547                                 item->index = i;
2548                                 item->count = child->ondisk->count;
2549
2550                                 /*
2551                                  * Recurse (used by the rebalancing code)
2552                                  */
2553                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2554                                         error = hammer_btree_lock_children(
2555                                                         cursor,
2556                                                         depth - 1,
2557                                                         item);
2558                                 }
2559                         }
2560                 }
2561         }
2562         if (error)
2563                 hammer_btree_unlock_children(cursor, parent);
2564         return(error);
2565 }
2566
2567 /*
2568  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2569  * including the parent.
2570  */
2571 void
2572 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2573 {
2574         hammer_mount_t hmp = cursor->trans->hmp;
2575         hammer_node_lock_t item;
2576
2577         if (parent->copy == NULL) {
2578                 parent->copy = kmalloc(sizeof(*parent->copy), hmp->m_misc,
2579                                        M_WAITOK);
2580                 *parent->copy = *parent->node->ondisk;
2581         }
2582         TAILQ_FOREACH(item, &parent->list, entry) {
2583                 hammer_btree_lock_copy(cursor, item);
2584         }
2585 }
2586
2587 /*
2588  * Recursively sync modified copies to the media.
2589  */
2590 int
2591 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2592 {
2593         hammer_node_lock_t item;
2594         int count = 0;
2595
2596         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2597                 ++count;
2598                 hammer_modify_node_all(cursor->trans, parent->node);
2599                 *parent->node->ondisk = *parent->copy;
2600                 hammer_modify_node_done(parent->node);
2601                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2602                         hammer_flush_node(parent->node);
2603                         hammer_delete_node(cursor->trans, parent->node);
2604                 }
2605         }
2606         TAILQ_FOREACH(item, &parent->list, entry) {
2607                 count += hammer_btree_sync_copy(cursor, item);
2608         }
2609         return(count);
2610 }
2611
2612 /*
2613  * Release previously obtained node locks.  The caller is responsible for
2614  * cleaning up parent->node itself (its usually just aliased from a cursor),
2615  * but this function will take care of the copies.
2616  */
2617 void
2618 hammer_btree_unlock_children(hammer_cursor_t cursor, hammer_node_lock_t parent)
2619 {
2620         hammer_node_lock_t item;
2621
2622         if (parent->copy) {
2623                 kfree(parent->copy, cursor->trans->hmp->m_misc);
2624                 parent->copy = NULL;    /* safety */
2625         }
2626         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2627                 TAILQ_REMOVE(&parent->list, item, entry);
2628                 hammer_btree_unlock_children(cursor, item);
2629                 hammer_unlock(&item->node->lock);
2630                 hammer_rel_node(item->node);
2631                 kfree(item, cursor->trans->hmp->m_misc);
2632         }
2633 }
2634
2635 /************************************************************************
2636  *                         MISCELLANIOUS SUPPORT                        *
2637  ************************************************************************/
2638
2639 /*
2640  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2641  *
2642  * Note that for this particular function a return value of -1, 0, or +1
2643  * can denote a match if create_tid is otherwise discounted.  A create_tid
2644  * of zero is considered to be 'infinity' in comparisons.
2645  *
2646  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2647  */
2648 int
2649 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2650 {
2651         if (key1->localization < key2->localization)
2652                 return(-5);
2653         if (key1->localization > key2->localization)
2654                 return(5);
2655
2656         if (key1->obj_id < key2->obj_id)
2657                 return(-4);
2658         if (key1->obj_id > key2->obj_id)
2659                 return(4);
2660
2661         if (key1->rec_type < key2->rec_type)
2662                 return(-3);
2663         if (key1->rec_type > key2->rec_type)
2664                 return(3);
2665
2666         if (key1->key < key2->key)
2667                 return(-2);
2668         if (key1->key > key2->key)
2669                 return(2);
2670
2671         /*
2672          * A create_tid of zero indicates a record which is undeletable
2673          * and must be considered to have a value of positive infinity.
2674          */
2675         if (key1->create_tid == 0) {
2676                 if (key2->create_tid == 0)
2677                         return(0);
2678                 return(1);
2679         }
2680         if (key2->create_tid == 0)
2681                 return(-1);
2682         if (key1->create_tid < key2->create_tid)
2683                 return(-1);
2684         if (key1->create_tid > key2->create_tid)
2685                 return(1);
2686         return(0);
2687 }
2688
2689 /*
2690  * Test a timestamp against an element to determine whether the
2691  * element is visible.  A timestamp of 0 means 'infinity'.
2692  */
2693 int
2694 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2695 {
2696         if (asof == 0) {
2697                 if (base->delete_tid)
2698                         return(1);
2699                 return(0);
2700         }
2701         if (asof < base->create_tid)
2702                 return(-1);
2703         if (base->delete_tid && asof >= base->delete_tid)
2704                 return(1);
2705         return(0);
2706 }
2707
2708 /*
2709  * Create a separator half way inbetween key1 and key2.  For fields just
2710  * one unit apart, the separator will match key2.  key1 is on the left-hand
2711  * side and key2 is on the right-hand side.
2712  *
2713  * key2 must be >= the separator.  It is ok for the separator to match key2.
2714  *
2715  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2716  * key2.
2717  *
2718  * NOTE: It might be beneficial to just scrap this whole mess and just
2719  * set the separator to key2.
2720  */
2721 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2722         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2723
2724 static void
2725 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2726                       hammer_base_elm_t dest)
2727 {
2728         bzero(dest, sizeof(*dest));
2729
2730         dest->rec_type = key2->rec_type;
2731         dest->key = key2->key;
2732         dest->obj_id = key2->obj_id;
2733         dest->create_tid = key2->create_tid;
2734
2735         MAKE_SEPARATOR(key1, key2, dest, localization);
2736         if (key1->localization == key2->localization) {
2737                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
2738                 if (key1->obj_id == key2->obj_id) {
2739                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
2740                         if (key1->rec_type == key2->rec_type) {
2741                                 MAKE_SEPARATOR(key1, key2, dest, key);
2742                                 /*
2743                                  * Don't bother creating a separator for
2744                                  * create_tid, which also conveniently avoids
2745                                  * having to handle the create_tid == 0
2746                                  * (infinity) case.  Just leave create_tid
2747                                  * set to key2.
2748                                  *
2749                                  * Worst case, dest matches key2 exactly,
2750                                  * which is acceptable.
2751                                  */
2752                         }
2753                 }
2754         }
2755 }
2756
2757 #undef MAKE_SEPARATOR
2758
2759 /*
2760  * Return whether a generic internal or leaf node is full
2761  */
2762 static int
2763 btree_node_is_full(hammer_node_ondisk_t node)
2764 {
2765         switch(node->type) {
2766         case HAMMER_BTREE_TYPE_INTERNAL:
2767                 if (node->count == HAMMER_BTREE_INT_ELMS)
2768                         return(1);
2769                 break;
2770         case HAMMER_BTREE_TYPE_LEAF:
2771                 if (node->count == HAMMER_BTREE_LEAF_ELMS)
2772                         return(1);
2773                 break;
2774         default:
2775                 panic("illegal btree subtype");
2776         }
2777         return(0);
2778 }
2779
2780 #if 0
2781 static int
2782 btree_max_elements(u_int8_t type)
2783 {
2784         if (type == HAMMER_BTREE_TYPE_LEAF)
2785                 return(HAMMER_BTREE_LEAF_ELMS);
2786         if (type == HAMMER_BTREE_TYPE_INTERNAL)
2787                 return(HAMMER_BTREE_INT_ELMS);
2788         panic("btree_max_elements: bad type %d\n", type);
2789 }
2790 #endif
2791
2792 void
2793 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
2794 {
2795         hammer_btree_elm_t elm;
2796         int i;
2797
2798         kprintf("node %p count=%d parent=%016llx type=%c\n",
2799                 ondisk, ondisk->count, ondisk->parent, ondisk->type);
2800
2801         /*
2802          * Dump both boundary elements if an internal node
2803          */
2804         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2805                 for (i = 0; i <= ondisk->count; ++i) {
2806                         elm = &ondisk->elms[i];
2807                         hammer_print_btree_elm(elm, ondisk->type, i);
2808                 }
2809         } else {
2810                 for (i = 0; i < ondisk->count; ++i) {
2811                         elm = &ondisk->elms[i];
2812                         hammer_print_btree_elm(elm, ondisk->type, i);
2813                 }
2814         }
2815 }
2816
2817 void
2818 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
2819 {
2820         kprintf("  %2d", i);
2821         kprintf("\tobj_id       = %016llx\n", elm->base.obj_id);
2822         kprintf("\tkey          = %016llx\n", elm->base.key);
2823         kprintf("\tcreate_tid   = %016llx\n", elm->base.create_tid);
2824         kprintf("\tdelete_tid   = %016llx\n", elm->base.delete_tid);
2825         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
2826         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
2827         kprintf("\tbtype        = %02x (%c)\n",
2828                 elm->base.btype,
2829                 (elm->base.btype ? elm->base.btype : '?'));
2830         kprintf("\tlocalization = %02x\n", elm->base.localization);
2831
2832         switch(type) {
2833         case HAMMER_BTREE_TYPE_INTERNAL:
2834                 kprintf("\tsubtree_off  = %016llx\n",
2835                         elm->internal.subtree_offset);
2836                 break;
2837         case HAMMER_BTREE_TYPE_RECORD:
2838                 kprintf("\tdata_offset  = %016llx\n", elm->leaf.data_offset);
2839                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
2840                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
2841                 break;
2842         }
2843 }