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         hammer_mount_t hmp;
 121         int error = 0;
 122         int r;
 123         int s;
 124
 125         /*
 126          * Skip past the current record
 127          */
 128         hmp = cursor->trans->hmp;
 129         node = cursor->node->ondisk;
 130         if (node == NULL)
 131                 return(ENOENT);
 132         if (cursor->index < node->count &&
 133             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 134                 ++cursor->index;
 135         }
 136
 137         /*
 138          * HAMMER can wind up being cpu-bound.
 139          */
 140         if (++hmp->check_yield > hammer_yield_check) {
 141                 hmp->check_yield = 0;
 142                 lwkt_user_yield();
 143         }
 144
 145
 146         /*
 147          * Loop until an element is found or we are done.
 148          */
 149         for (;;) {
 150                 /*
 151                  * We iterate up the tree and then index over one element
 152                  * while we are at the last element in the current node.
 153                  *
 154                  * If we are at the root of the filesystem, cursor_up
 155                  * returns ENOENT.
 156                  *
 157                  * XXX this could be optimized by storing the information in
 158                  * the parent reference.
 159                  *
 160                  * XXX we can lose the node lock temporarily, this could mess
 161                  * up our scan.
 162                  */
 163                 ++hammer_stats_btree_iterations;
 164                 hammer_flusher_clean_loose_ios(hmp);
 165
 166                 if (cursor->index == node->count) {
 167                         if (hammer_debug_btree) {
 168                                 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
 169                                         (long long)cursor->node->node_offset,
 170                                         cursor->index,
 171                                         (long long)(cursor->parent ? cursor->parent->node_offset : -1),
 172                                         cursor->parent_index,
 173                                         curthread);
 174                         }
 175                         KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
 176                         error = hammer_cursor_up(cursor);
 177                         if (error)
 178                                 break;
 179                         /* reload stale pointer */
 180                         node = cursor->node->ondisk;
 181                         KKASSERT(cursor->index != node->count);
 182
 183                         /*
 184                          * If we are reblocking we want to return internal
 185                          * nodes.  Note that the internal node will be
 186                          * returned multiple times, on each upward recursion
 187                          * from its children.  The caller selects which
 188                          * revisit it cares about (usually first or last only).
 189                          */
 190                         if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
 191                                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 192                                 return(0);
 193                         }
 194                         ++cursor->index;
 195                         continue;
 196                 }
 197
 198                 /*
 199                  * Check internal or leaf element.  Determine if the record
 200                  * at the cursor has gone beyond the end of our range.
 201                  *
 202                  * We recurse down through internal nodes.
 203                  */
 204                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 205                         elm = &node->elms[cursor->index];
 206
 207                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 208                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 209                         if (hammer_debug_btree) {
 210                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
 211                                         (long long)cursor->node->node_offset,
 212                                         cursor->index,
 213                                         (long long)elm[0].internal.base.obj_id,
 214                                         elm[0].internal.base.rec_type,
 215                                         (long long)elm[0].internal.base.key,
 216                                         elm[0].internal.base.localization,
 217                                         r,
 218                                         curthread
 219                                 );
 220                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 221                                         (long long)cursor->node->node_offset,
 222                                         cursor->index + 1,
 223                                         (long long)elm[1].internal.base.obj_id,
 224                                         elm[1].internal.base.rec_type,
 225                                         (long long)elm[1].internal.base.key,
 226                                         elm[1].internal.base.localization,
 227                                         s
 228                                 );
 229                         }
 230
 231                         if (r < 0) {
 232                                 error = ENOENT;
 233                                 break;
 234                         }
 235                         if (r == 0 && (cursor->flags &
 236                                        HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 237                                 error = ENOENT;
 238                                 break;
 239                         }
 240                         KKASSERT(s <= 0);
 241
 242                         /*
 243                          * Better not be zero
 244                          */
 245                         KKASSERT(elm->internal.subtree_offset != 0);
 246
 247                         /*
 248                          * If running the mirror filter see if we can skip
 249                          * one or more entire sub-trees.  If we can we
 250                          * return the internal mode and the caller processes
 251                          * the skipped range (see mirror_read)
 252                          */
 253                         if (cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) {
 254                                 if (elm->internal.mirror_tid <
 255                                     cursor->cmirror->mirror_tid) {
 256                                         hammer_cursor_mirror_filter(cursor);
 257                                         return(0);
 258                                 }
 259                         }
 260
 261                         error = hammer_cursor_down(cursor);
 262                         if (error)
 263                                 break;
 264                         KKASSERT(cursor->index == 0);
 265                         /* reload stale pointer */
 266                         node = cursor->node->ondisk;
 267                         continue;
 268                 } else {
 269                         elm = &node->elms[cursor->index];
 270                         r = hammer_btree_cmp(&cursor->key_end, &elm->base);
 271                         if (hammer_debug_btree) {
 272                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 273                                         (long long)cursor->node->node_offset,
 274                                         cursor->index,
 275                                         (elm[0].leaf.base.btype ?
 276                                          elm[0].leaf.base.btype : '?'),
 277                                         (long long)elm[0].leaf.base.obj_id,
 278                                         elm[0].leaf.base.rec_type,
 279                                         (long long)elm[0].leaf.base.key,
 280                                         elm[0].leaf.base.localization,
 281                                         r
 282                                 );
 283                         }
 284                         if (r < 0) {
 285                                 error = ENOENT;
 286                                 break;
 287                         }
 288
 289                         /*
 290                          * We support both end-inclusive and
 291                          * end-exclusive searches.
 292                          */
 293                         if (r == 0 &&
 294                            (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 295                                 error = ENOENT;
 296                                 break;
 297                         }
 298
 299                         switch(elm->leaf.base.btype) {
 300                         case HAMMER_BTREE_TYPE_RECORD:
 301                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 302                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 303                                         ++cursor->index;
 304                                         continue;
 305                                 }
 306                                 error = 0;
 307                                 break;
 308                         default:
 309                                 error = EINVAL;
 310                                 break;
 311                         }
 312                         if (error)
 313                                 break;
 314                 }
 315                 /*
 316                  * node pointer invalid after loop
 317                  */
 318
 319                 /*
 320                  * Return entry
 321                  */
 322                 if (hammer_debug_btree) {
 323                         int i = cursor->index;
 324                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 325                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 326                                 cursor->node, i,
 327                                 (long long)elm->internal.base.obj_id,
 328                                 elm->internal.base.rec_type,
 329                                 (long long)elm->internal.base.key,
 330                                 elm->internal.base.localization
 331                         );
 332                 }
 333                 return(0);
 334         }
 335         return(error);
 336 }
 337
 338 /*
 339  * We hit an internal element that we could skip as part of a mirroring
 340  * scan.  Calculate the entire range being skipped.
 341  *
 342  * It is important to include any gaps between the parent's left_bound
 343  * and the node's left_bound, and same goes for the right side.
 344  */
 345 static void
 346 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
 347 {
 348         struct hammer_cmirror *cmirror;
 349         hammer_node_ondisk_t ondisk;
 350         hammer_btree_elm_t elm;
 351
 352         ondisk = cursor->node->ondisk;
 353         cmirror = cursor->cmirror;
 354
 355         /*
 356          * Calculate the skipped range
 357          */
 358         elm = &ondisk->elms[cursor->index];
 359         if (cursor->index == 0)
 360                 cmirror->skip_beg = *cursor->left_bound;
 361         else
 362                 cmirror->skip_beg = elm->internal.base;
 363         while (cursor->index < ondisk->count) {
 364                 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
 365                         break;
 366                 ++cursor->index;
 367                 ++elm;
 368         }
 369         if (cursor->index == ondisk->count)
 370                 cmirror->skip_end = *cursor->right_bound;
 371         else
 372                 cmirror->skip_end = elm->internal.base;
 373
 374         /*
 375          * clip the returned result.
 376          */
 377         if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
 378                 cmirror->skip_beg = cursor->key_beg;
 379         if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
 380                 cmirror->skip_end = cursor->key_end;
 381 }
 382
 383 /*
 384  * Iterate in the reverse direction.  This is used by the pruning code to
 385  * avoid overlapping records.
 386  */
 387 int
 388 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
 389 {
 390         hammer_node_ondisk_t node;
 391         hammer_btree_elm_t elm;
 392         int error = 0;
 393         int r;
 394         int s;
 395
 396         /* mirror filtering not supported for reverse iteration */
 397         KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
 398
 399         /*
 400          * Skip past the current record.  For various reasons the cursor
 401          * may end up set to -1 or set to point at the end of the current
 402          * node.  These cases must be addressed.
 403          */
 404         node = cursor->node->ondisk;
 405         if (node == NULL)
 406                 return(ENOENT);
 407         if (cursor->index != -1 &&
 408             (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
 409                 --cursor->index;
 410         }
 411         if (cursor->index == cursor->node->ondisk->count)
 412                 --cursor->index;
 413
 414         /*
 415          * Loop until an element is found or we are done.
 416          */
 417         for (;;) {
 418                 ++hammer_stats_btree_iterations;
 419                 hammer_flusher_clean_loose_ios(cursor->trans->hmp);
 420
 421                 /*
 422                  * We iterate up the tree and then index over one element
 423                  * while we are at the last element in the current node.
 424                  */
 425                 if (cursor->index == -1) {
 426                         error = hammer_cursor_up(cursor);
 427                         if (error) {
 428                                 cursor->index = 0; /* sanity */
 429                                 break;
 430                         }
 431                         /* reload stale pointer */
 432                         node = cursor->node->ondisk;
 433                         KKASSERT(cursor->index != node->count);
 434                         --cursor->index;
 435                         continue;
 436                 }
 437
 438                 /*
 439                  * Check internal or leaf element.  Determine if the record
 440                  * at the cursor has gone beyond the end of our range.
 441                  *
 442                  * We recurse down through internal nodes.
 443                  */
 444                 KKASSERT(cursor->index != node->count);
 445                 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
 446                         elm = &node->elms[cursor->index];
 447                         r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
 448                         s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
 449                         if (hammer_debug_btree) {
 450                                 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 451                                         (long long)cursor->node->node_offset,
 452                                         cursor->index,
 453                                         (long long)elm[0].internal.base.obj_id,
 454                                         elm[0].internal.base.rec_type,
 455                                         (long long)elm[0].internal.base.key,
 456                                         elm[0].internal.base.localization,
 457                                         r
 458                                 );
 459                                 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
 460                                         (long long)cursor->node->node_offset,
 461                                         cursor->index + 1,
 462                                         (long long)elm[1].internal.base.obj_id,
 463                                         elm[1].internal.base.rec_type,
 464                                         (long long)elm[1].internal.base.key,
 465                                         elm[1].internal.base.localization,
 466                                         s
 467                                 );
 468                         }
 469
 470                         if (s >= 0) {
 471                                 error = ENOENT;
 472                                 break;
 473                         }
 474                         KKASSERT(r >= 0);
 475
 476                         /*
 477                          * Better not be zero
 478                          */
 479                         KKASSERT(elm->internal.subtree_offset != 0);
 480
 481                         error = hammer_cursor_down(cursor);
 482                         if (error)
 483                                 break;
 484                         KKASSERT(cursor->index == 0);
 485                         /* reload stale pointer */
 486                         node = cursor->node->ondisk;
 487
 488                         /* this can assign -1 if the leaf was empty */
 489                         cursor->index = node->count - 1;
 490                         continue;
 491                 } else {
 492                         elm = &node->elms[cursor->index];
 493                         s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
 494                         if (hammer_debug_btree) {
 495                                 kprintf("ELEMENT  %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
 496                                         (long long)cursor->node->node_offset,
 497                                         cursor->index,
 498                                         (elm[0].leaf.base.btype ?
 499                                          elm[0].leaf.base.btype : '?'),
 500                                         (long long)elm[0].leaf.base.obj_id,
 501                                         elm[0].leaf.base.rec_type,
 502                                         (long long)elm[0].leaf.base.key,
 503                                         elm[0].leaf.base.localization,
 504                                         s
 505                                 );
 506                         }
 507                         if (s > 0) {
 508                                 error = ENOENT;
 509                                 break;
 510                         }
 511
 512                         switch(elm->leaf.base.btype) {
 513                         case HAMMER_BTREE_TYPE_RECORD:
 514                                 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
 515                                     hammer_btree_chkts(cursor->asof, &elm->base)) {
 516                                         --cursor->index;
 517                                         continue;
 518                                 }
 519                                 error = 0;
 520                                 break;
 521                         default:
 522                                 error = EINVAL;
 523                                 break;
 524                         }
 525                         if (error)
 526                                 break;
 527                 }
 528                 /*
 529                  * node pointer invalid after loop
 530                  */
 531
 532                 /*
 533                  * Return entry
 534                  */
 535                 if (hammer_debug_btree) {
 536                         int i = cursor->index;
 537                         hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
 538                         kprintf("ITERATE  %p:%d %016llx %02x %016llx lo=%02x\n",
 539                                 cursor->node, i,
 540                                 (long long)elm->internal.base.obj_id,
 541                                 elm->internal.base.rec_type,
 542                                 (long long)elm->internal.base.key,
 543                                 elm->internal.base.localization
 544                         );
 545                 }
 546                 return(0);
 547         }
 548         return(error);
 549 }
 550
 551 /*
 552  * Lookup cursor->key_beg.  0 is returned on success, ENOENT if the entry
 553  * could not be found, EDEADLK if inserting and a retry is needed, and a
 554  * fatal error otherwise.  When retrying, the caller must terminate the
 555  * cursor and reinitialize it.  EDEADLK cannot be returned if not inserting.
 556  *
 557  * The cursor is suitably positioned for a deletion on success, and suitably
 558  * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
 559  * specified.
 560  *
 561  * The cursor may begin anywhere, the search will traverse the tree in
 562  * either direction to locate the requested element.
 563  *
 564  * Most of the logic implementing historical searches is handled here.  We
 565  * do an initial lookup with create_tid set to the asof TID.  Due to the
 566  * way records are laid out, a backwards iteration may be required if
 567  * ENOENT is returned to locate the historical record.  Here's the
 568  * problem:
 569  *
 570  * create_tid:    10      15       20
 571  *                   LEAF1   LEAF2
 572  * records:         (11)        (18)
 573  *
 574  * Lets say we want to do a lookup AS-OF timestamp 17.  We will traverse
 575  * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
 576  * not visible and thus causes ENOENT to be returned.  We really need
 577  * to check record 11 in LEAF1.  If it also fails then the search fails
 578  * (e.g. it might represent the range 11-16 and thus still not match our
 579  * AS-OF timestamp of 17).  Note that LEAF1 could be empty, requiring
 580  * further iterations.
 581  *
 582  * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
 583  * and the cursor->create_check TID if an iteration might be needed.
 584  * In the above example create_check would be set to 14.
 585  */
 586 int
 587 hammer_btree_lookup(hammer_cursor_t cursor)
 588 {
 589         int error;
 590
 591         KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
 592                   cursor->trans->sync_lock_refs > 0);
 593         ++hammer_stats_btree_lookups;
 594         if (cursor->flags & HAMMER_CURSOR_ASOF) {
 595                 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
 596                 cursor->key_beg.create_tid = cursor->asof;
 597                 for (;;) {
 598                         cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
 599                         error = btree_search(cursor, 0);
 600                         if (error != ENOENT ||
 601                             (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
 602                                 /*
 603                                  * Stop if no error.
 604                                  * Stop if error other then ENOENT.
 605                                  * Stop if ENOENT and not special case.
 606                                  */
 607                                 break;
 608                         }
 609                         if (hammer_debug_btree) {
 610                                 kprintf("CREATE_CHECK %016llx\n",
 611                                         (long long)cursor->create_check);
 612                         }
 613                         cursor->key_beg.create_tid = cursor->create_check;
 614                         /* loop */
 615                 }
 616         } else {
 617                 error = btree_search(cursor, 0);
 618         }
 619         if (error == 0)
 620                 error = hammer_btree_extract(cursor, cursor->flags);
 621         return(error);
 622 }
 623
 624 /*
 625  * Execute the logic required to start an iteration.  The first record
 626  * located within the specified range is returned and iteration control
 627  * flags are adjusted for successive hammer_btree_iterate() calls.
 628  *
 629  * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
 630  * in a loop without worrying about it.  Higher-level merged searches will
 631  * adjust the flag appropriately.
 632  */
 633 int
 634 hammer_btree_first(hammer_cursor_t cursor)
 635 {
 636         int error;
 637
 638         error = hammer_btree_lookup(cursor);
 639         if (error == ENOENT) {
 640                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 641                 error = hammer_btree_iterate(cursor);
 642         }
 643         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 644         return(error);
 645 }
 646
 647 /*
 648  * Similarly but for an iteration in the reverse direction.
 649  *
 650  * Set ATEDISK when iterating backwards to skip the current entry,
 651  * which after an ENOENT lookup will be pointing beyond our end point.
 652  *
 653  * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
 654  * in a loop without worrying about it.  Higher-level merged searches will
 655  * adjust the flag appropriately.
 656  */
 657 int
 658 hammer_btree_last(hammer_cursor_t cursor)
 659 {
 660         struct hammer_base_elm save;
 661         int error;
 662
 663         save = cursor->key_beg;
 664         cursor->key_beg = cursor->key_end;
 665         error = hammer_btree_lookup(cursor);
 666         cursor->key_beg = save;
 667         if (error == ENOENT ||
 668             (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
 669                 cursor->flags |= HAMMER_CURSOR_ATEDISK;
 670                 error = hammer_btree_iterate_reverse(cursor);
 671         }
 672         cursor->flags |= HAMMER_CURSOR_ATEDISK;
 673         return(error);
 674 }
 675
 676 /*
 677  * Extract the record and/or data associated with the cursor's current
 678  * position.  Any prior record or data stored in the cursor is replaced.
 679  * The cursor must be positioned at a leaf node.
 680  *
 681  * NOTE: All extractions occur at the leaf of the B-Tree.
 682  */
 683 int
 684 hammer_btree_extract(hammer_cursor_t cursor, int flags)
 685 {
 686         hammer_node_ondisk_t node;
 687         hammer_btree_elm_t elm;
 688         hammer_off_t data_off;
 689         hammer_mount_t hmp;
 690         int32_t data_len;
 691         int error;
 692
 693         /*
 694          * The case where the data reference resolves to the same buffer
 695          * as the record reference must be handled.
 696          */
 697         node = cursor->node->ondisk;
 698         elm = &node->elms[cursor->index];
 699         cursor->data = NULL;
 700         hmp = cursor->node->hmp;
 701
 702         /*
 703          * There is nothing to extract for an internal element.
 704          */
 705         if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
 706                 return(EINVAL);
 707
 708         /*
 709          * Only record types have data.
 710          */
 711         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 712         cursor->leaf = &elm->leaf;
 713
 714         if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
 715                 return(0);
 716         if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
 717                 return(0);
 718         data_off = elm->leaf.data_offset;
 719         data_len = elm->leaf.data_len;
 720         if (data_off == 0)
 721                 return(0);
 722
 723         /*
 724          * Load the data
 725          */
 726         KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
 727         cursor->data = hammer_bread_ext(hmp, data_off, data_len,
 728                                         &error, &cursor->data_buffer);
 729         if (hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
 730                 kprintf("CRC DATA @ %016llx/%d FAILED\n",
 731                         (long long)elm->leaf.data_offset, elm->leaf.data_len);
 732                 if (hammer_debug_debug & 0x0001)
 733                         Debugger("CRC FAILED: DATA");
 734                 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
 735                         error = EDOM;   /* less critical (mirroring) */
 736                 else
 737                         error = EIO;    /* critical */
 738         }
 739         return(error);
 740 }
 741
 742
 743 /*
 744  * Insert a leaf element into the B-Tree at the current cursor position.
 745  * The cursor is positioned such that the element at and beyond the cursor
 746  * are shifted to make room for the new record.
 747  *
 748  * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
 749  * flag set and that call must return ENOENT before this function can be
 750  * called.
 751  *
 752  * The caller may depend on the cursor's exclusive lock after return to
 753  * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
 754  *
 755  * ENOSPC is returned if there is no room to insert a new record.
 756  */
 757 int
 758 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
 759                     int *doprop)
 760 {
 761         hammer_node_ondisk_t node;
 762         int i;
 763         int error;
 764
 765         *doprop = 0;
 766         if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
 767                 return(error);
 768         ++hammer_stats_btree_inserts;
 769
 770         /*
 771          * Insert the element at the leaf node and update the count in the
 772          * parent.  It is possible for parent to be NULL, indicating that
 773          * the filesystem's ROOT B-Tree node is a leaf itself, which is
 774          * possible.  The root inode can never be deleted so the leaf should
 775          * never be empty.
 776          *
 777          * Remember that the right-hand boundary is not included in the
 778          * count.
 779          */
 780         hammer_modify_node_all(cursor->trans, cursor->node);
 781         node = cursor->node->ondisk;
 782         i = cursor->index;
 783         KKASSERT(elm->base.btype != 0);
 784         KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
 785         KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
 786         if (i != node->count) {
 787                 bcopy(&node->elms[i], &node->elms[i+1],
 788                       (node->count - i) * sizeof(*elm));
 789         }
 790         node->elms[i].leaf = *elm;
 791         ++node->count;
 792         hammer_cursor_inserted_element(cursor->node, i);
 793
 794         /*
 795          * Update the leaf node's aggregate mirror_tid for mirroring
 796          * support.
 797          */
 798         if (node->mirror_tid < elm->base.delete_tid) {
 799                 node->mirror_tid = elm->base.delete_tid;
 800                 *doprop = 1;
 801         }
 802         if (node->mirror_tid < elm->base.create_tid) {
 803                 node->mirror_tid = elm->base.create_tid;
 804                 *doprop = 1;
 805         }
 806         hammer_modify_node_done(cursor->node);
 807
 808         /*
 809          * Debugging sanity checks.
 810          */
 811         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
 812         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
 813         if (i) {
 814                 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
 815         }
 816         if (i != node->count - 1)
 817                 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
 818
 819         return(0);
 820 }
 821
 822 /*
 823  * Delete a record from the B-Tree at the current cursor position.
 824  * The cursor is positioned such that the current element is the one
 825  * to be deleted.
 826  *
 827  * On return the cursor will be positioned after the deleted element and
 828  * MAY point to an internal node.  It will be suitable for the continuation
 829  * of an iteration but not for an insertion or deletion.
 830  *
 831  * Deletions will attempt to partially rebalance the B-Tree in an upward
 832  * direction, but will terminate rather then deadlock.  Empty internal nodes
 833  * are never allowed by a deletion which deadlocks may end up giving us an
 834  * empty leaf.  The pruner will clean up and rebalance the tree.
 835  *
 836  * This function can return EDEADLK, requiring the caller to retry the
 837  * operation after clearing the deadlock.
 838  */
 839 int
 840 hammer_btree_delete(hammer_cursor_t cursor)
 841 {
 842         hammer_node_ondisk_t ondisk;
 843         hammer_node_t node;
 844         hammer_node_t parent;
 845         int error;
 846         int i;
 847
 848         KKASSERT (cursor->trans->sync_lock_refs > 0);
 849         if ((error = hammer_cursor_upgrade(cursor)) != 0)
 850                 return(error);
 851         ++hammer_stats_btree_deletes;
 852
 853         /*
 854          * Delete the element from the leaf node.
 855          *
 856          * Remember that leaf nodes do not have boundaries.
 857          */
 858         node = cursor->node;
 859         ondisk = node->ondisk;
 860         i = cursor->index;
 861
 862         KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
 863         KKASSERT(i >= 0 && i < ondisk->count);
 864         hammer_modify_node_all(cursor->trans, node);
 865         if (i + 1 != ondisk->count) {
 866                 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
 867                       (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
 868         }
 869         --ondisk->count;
 870         hammer_modify_node_done(node);
 871         hammer_cursor_deleted_element(node, i);
 872
 873         /*
 874          * Validate local parent
 875          */
 876         if (ondisk->parent) {
 877                 parent = cursor->parent;
 878
 879                 KKASSERT(parent != NULL);
 880                 KKASSERT(parent->node_offset == ondisk->parent);
 881         }
 882
 883         /*
 884          * If the leaf becomes empty it must be detached from the parent,
 885          * potentially recursing through to the filesystem root.
 886          *
 887          * This may reposition the cursor at one of the parent's of the
 888          * current node.
 889          *
 890          * Ignore deadlock errors, that simply means that btree_remove
 891          * was unable to recurse and had to leave us with an empty leaf.
 892          */
 893         KKASSERT(cursor->index <= ondisk->count);
 894         if (ondisk->count == 0) {
 895                 error = btree_remove(cursor);
 896                 if (error == EDEADLK)
 897                         error = 0;
 898         } else {
 899                 error = 0;
 900         }
 901         KKASSERT(cursor->parent == NULL ||
 902                  cursor->parent_index < cursor->parent->ondisk->count);
 903         return(error);
 904 }
 905
 906 /*
 907  * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
 908  *
 909  * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
 910  *
 911  * The search can begin ANYWHERE in the B-Tree.  As a first step the search
 912  * iterates up the tree as necessary to properly position itself prior to
 913  * actually doing the sarch.
 914  *
 915  * INSERTIONS: The search will split full nodes and leaves on its way down
 916  * and guarentee that the leaf it ends up on is not full.  If we run out
 917  * of space the search continues to the leaf (to position the cursor for
 918  * the spike), but ENOSPC is returned.
 919  *
 920  * The search is only guarenteed to end up on a leaf if an error code of 0
 921  * is returned, or if inserting and an error code of ENOENT is returned.
 922  * Otherwise it can stop at an internal node.  On success a search returns
 923  * a leaf node.
 924  *
 925  * COMPLEXITY WARNING!  This is the core B-Tree search code for the entire
 926  * filesystem, and it is not simple code.  Please note the following facts:
 927  *
 928  * - Internal node recursions have a boundary on the left AND right.  The
 929  *   right boundary is non-inclusive.  The create_tid is a generic part
 930  *   of the key for internal nodes.
 931  *
 932  * - Leaf nodes contain terminal elements only now.
 933  *
 934  * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
 935  *   historical search.  ASOF and INSERT are mutually exclusive.  When
 936  *   doing an as-of lookup btree_search() checks for a right-edge boundary
 937  *   case.  If while recursing down the left-edge differs from the key
 938  *   by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
 939  *   with cursor->create_check.  This is used by btree_lookup() to iterate.
 940  *   The iteration backwards because as-of searches can wind up going
 941  *   down the wrong branch of the B-Tree.
 942  */
 943 static
 944 int
 945 btree_search(hammer_cursor_t cursor, int flags)
 946 {
 947         hammer_node_ondisk_t node;
 948         hammer_btree_elm_t elm;
 949         int error;
 950         int enospc = 0;
 951         int i;
 952         int r;
 953         int s;
 954
 955         flags |= cursor->flags;
 956         ++hammer_stats_btree_searches;
 957
 958         if (hammer_debug_btree) {
 959                 kprintf("SEARCH   %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
 960                         (long long)cursor->node->node_offset,
 961                         cursor->index,
 962                         (long long)cursor->key_beg.obj_id,
 963                         cursor->key_beg.rec_type,
 964                         (long long)cursor->key_beg.key,
 965                         (long long)cursor->key_beg.create_tid,
 966                         cursor->key_beg.localization,
 967                         curthread
 968                 );
 969                 if (cursor->parent)
 970                     kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
 971                         (long long)cursor->parent->node_offset,
 972                         cursor->parent_index,
 973                         (long long)cursor->left_bound->obj_id,
 974                         (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
 975                         (long long)cursor->right_bound->obj_id,
 976                         (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
 977                         cursor->left_bound,
 978                         &cursor->parent->ondisk->elms[cursor->parent_index],
 979                         cursor->right_bound,
 980                         &cursor->parent->ondisk->elms[cursor->parent_index+1]
 981                     );
 982         }
 983
 984         /*
 985          * Move our cursor up the tree until we find a node whos range covers
 986          * the key we are trying to locate.
 987          *
 988          * The left bound is inclusive, the right bound is non-inclusive.
 989          * It is ok to cursor up too far.
 990          */
 991         for (;;) {
 992                 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
 993                 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
 994                 if (r >= 0 && s < 0)
 995                         break;
 996                 KKASSERT(cursor->parent);
 997                 ++hammer_stats_btree_iterations;
 998                 error = hammer_cursor_up(cursor);
 999                 if (error)
1000                         goto done;
1001         }
1002
1003         /*
1004          * The delete-checks below are based on node, not parent.  Set the
1005          * initial delete-check based on the parent.
1006          */
1007         if (r == 1) {
1008                 KKASSERT(cursor->left_bound->create_tid != 1);
1009                 cursor->create_check = cursor->left_bound->create_tid - 1;
1010                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1011         }
1012
1013         /*
1014          * We better have ended up with a node somewhere.
1015          */
1016         KKASSERT(cursor->node != NULL);
1017
1018         /*
1019          * If we are inserting we can't start at a full node if the parent
1020          * is also full (because there is no way to split the node),
1021          * continue running up the tree until the requirement is satisfied
1022          * or we hit the root of the filesystem.
1023          *
1024          * (If inserting we aren't doing an as-of search so we don't have
1025          *  to worry about create_check).
1026          */
1027         while ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1028                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
1029                         if (btree_node_is_full(cursor->node->ondisk) == 0)
1030                                 break;
1031                 } else {
1032                         if (btree_node_is_full(cursor->node->ondisk) ==0)
1033                                 break;
1034                 }
1035                 if (cursor->node->ondisk->parent == 0 ||
1036                     cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1037                         break;
1038                 }
1039                 ++hammer_stats_btree_iterations;
1040                 error = hammer_cursor_up(cursor);
1041                 /* node may have become stale */
1042                 if (error)
1043                         goto done;
1044         }
1045
1046         /*
1047          * Push down through internal nodes to locate the requested key.
1048          */
1049         node = cursor->node->ondisk;
1050         while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1051                 /*
1052                  * Scan the node to find the subtree index to push down into.
1053                  * We go one-past, then back-up.
1054                  *
1055                  * We must proactively remove deleted elements which may
1056                  * have been left over from a deadlocked btree_remove().
1057                  *
1058                  * The left and right boundaries are included in the loop
1059                  * in order to detect edge cases.
1060                  *
1061                  * If the separator only differs by create_tid (r == 1)
1062                  * and we are doing an as-of search, we may end up going
1063                  * down a branch to the left of the one containing the
1064                  * desired key.  This requires numerous special cases.
1065                  */
1066                 ++hammer_stats_btree_iterations;
1067                 if (hammer_debug_btree) {
1068                         kprintf("SEARCH-I %016llx count=%d\n",
1069                                 (long long)cursor->node->node_offset,
1070                                 node->count);
1071                 }
1072
1073                 /*
1074                  * Try to shortcut the search before dropping into the
1075                  * linear loop.  Locate the first node where r <= 1.
1076                  */
1077                 i = hammer_btree_search_node(&cursor->key_beg, node);
1078                 while (i <= node->count) {
1079                         ++hammer_stats_btree_elements;
1080                         elm = &node->elms[i];
1081                         r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1082                         if (hammer_debug_btree > 2) {
1083                                 kprintf(" IELM %p %d r=%d\n",
1084                                         &node->elms[i], i, r);
1085                         }
1086                         if (r < 0)
1087                                 break;
1088                         if (r == 1) {
1089                                 KKASSERT(elm->base.create_tid != 1);
1090                                 cursor->create_check = elm->base.create_tid - 1;
1091                                 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1092                         }
1093                         ++i;
1094                 }
1095                 if (hammer_debug_btree) {
1096                         kprintf("SEARCH-I preI=%d/%d r=%d\n",
1097                                 i, node->count, r);
1098                 }
1099
1100                 /*
1101                  * These cases occur when the parent's idea of the boundary
1102                  * is wider then the child's idea of the boundary, and
1103                  * require special handling.  If not inserting we can
1104                  * terminate the search early for these cases but the
1105                  * child's boundaries cannot be unconditionally modified.
1106                  */
1107                 if (i == 0) {
1108                         /*
1109                          * If i == 0 the search terminated to the LEFT of the
1110                          * left_boundary but to the RIGHT of the parent's left
1111                          * boundary.
1112                          */
1113                         u_int8_t save;
1114
1115                         elm = &node->elms[0];
1116
1117                         /*
1118                          * If we aren't inserting we can stop here.
1119                          */
1120                         if ((flags & (HAMMER_CURSOR_INSERT |
1121                                       HAMMER_CURSOR_PRUNING)) == 0) {
1122                                 cursor->index = 0;
1123                                 return(ENOENT);
1124                         }
1125
1126                         /*
1127                          * Correct a left-hand boundary mismatch.
1128                          *
1129                          * We can only do this if we can upgrade the lock,
1130                          * and synchronized as a background cursor (i.e.
1131                          * inserting or pruning).
1132                          *
1133                          * WARNING: We can only do this if inserting, i.e.
1134                          * we are running on the backend.
1135                          */
1136                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1137                                 return(error);
1138                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1139                         hammer_modify_node_field(cursor->trans, cursor->node,
1140                                                  elms[0]);
1141                         save = node->elms[0].base.btype;
1142                         node->elms[0].base = *cursor->left_bound;
1143                         node->elms[0].base.btype = save;
1144                         hammer_modify_node_done(cursor->node);
1145                 } else if (i == node->count + 1) {
1146                         /*
1147                          * If i == node->count + 1 the search terminated to
1148                          * the RIGHT of the right boundary but to the LEFT
1149                          * of the parent's right boundary.  If we aren't
1150                          * inserting we can stop here.
1151                          *
1152                          * Note that the last element in this case is
1153                          * elms[i-2] prior to adjustments to 'i'.
1154                          */
1155                         --i;
1156                         if ((flags & (HAMMER_CURSOR_INSERT |
1157                                       HAMMER_CURSOR_PRUNING)) == 0) {
1158                                 cursor->index = i;
1159                                 return (ENOENT);
1160                         }
1161
1162                         /*
1163                          * Correct a right-hand boundary mismatch.
1164                          * (actual push-down record is i-2 prior to
1165                          * adjustments to i).
1166                          *
1167                          * We can only do this if we can upgrade the lock,
1168                          * and synchronized as a background cursor (i.e.
1169                          * inserting or pruning).
1170                          *
1171                          * WARNING: We can only do this if inserting, i.e.
1172                          * we are running on the backend.
1173                          */
1174                         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1175                                 return(error);
1176                         elm = &node->elms[i];
1177                         KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1178                         hammer_modify_node(cursor->trans, cursor->node,
1179                                            &elm->base, sizeof(elm->base));
1180                         elm->base = *cursor->right_bound;
1181                         hammer_modify_node_done(cursor->node);
1182                         --i;
1183                 } else {
1184                         /*
1185                          * The push-down index is now i - 1.  If we had
1186                          * terminated on the right boundary this will point
1187                          * us at the last element.
1188                          */
1189                         --i;
1190                 }
1191                 cursor->index = i;
1192                 elm = &node->elms[i];
1193
1194                 if (hammer_debug_btree) {
1195                         kprintf("RESULT-I %016llx[%d] %016llx %02x "
1196                                 "key=%016llx cre=%016llx lo=%02x\n",
1197                                 (long long)cursor->node->node_offset,
1198                                 i,
1199                                 (long long)elm->internal.base.obj_id,
1200                                 elm->internal.base.rec_type,
1201                                 (long long)elm->internal.base.key,
1202                                 (long long)elm->internal.base.create_tid,
1203                                 elm->internal.base.localization
1204                         );
1205                 }
1206
1207                 /*
1208                  * We better have a valid subtree offset.
1209                  */
1210                 KKASSERT(elm->internal.subtree_offset != 0);
1211
1212                 /*
1213                  * Handle insertion and deletion requirements.
1214                  *
1215                  * If inserting split full nodes.  The split code will
1216                  * adjust cursor->node and cursor->index if the current
1217                  * index winds up in the new node.
1218                  *
1219                  * If inserting and a left or right edge case was detected,
1220                  * we cannot correct the left or right boundary and must
1221                  * prepend and append an empty leaf node in order to make
1222                  * the boundary correction.
1223                  *
1224                  * If we run out of space we set enospc and continue on
1225                  * to a leaf to provide the spike code with a good point
1226                  * of entry.
1227                  */
1228                 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1229                         if (btree_node_is_full(node)) {
1230                                 error = btree_split_internal(cursor);
1231                                 if (error) {
1232                                         if (error != ENOSPC)
1233                                                 goto done;
1234                                         enospc = 1;
1235                                 }
1236                                 /*
1237                                  * reload stale pointers
1238                                  */
1239                                 i = cursor->index;
1240                                 node = cursor->node->ondisk;
1241                         }
1242                 }
1243
1244                 /*
1245                  * Push down (push into new node, existing node becomes
1246                  * the parent) and continue the search.
1247                  */
1248                 error = hammer_cursor_down(cursor);
1249                 /* node may have become stale */
1250                 if (error)
1251                         goto done;
1252                 node = cursor->node->ondisk;
1253         }
1254
1255         /*
1256          * We are at a leaf, do a linear search of the key array.
1257          *
1258          * On success the index is set to the matching element and 0
1259          * is returned.
1260          *
1261          * On failure the index is set to the insertion point and ENOENT
1262          * is returned.
1263          *
1264          * Boundaries are not stored in leaf nodes, so the index can wind
1265          * up to the left of element 0 (index == 0) or past the end of
1266          * the array (index == node->count).  It is also possible that the
1267          * leaf might be empty.
1268          */
1269         ++hammer_stats_btree_iterations;
1270         KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1271         KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1272         if (hammer_debug_btree) {
1273                 kprintf("SEARCH-L %016llx count=%d\n",
1274                         (long long)cursor->node->node_offset,
1275                         node->count);
1276         }
1277
1278         /*
1279          * Try to shortcut the search before dropping into the
1280          * linear loop.  Locate the first node where r <= 1.
1281          */
1282         i = hammer_btree_search_node(&cursor->key_beg, node);
1283         while (i < node->count) {
1284                 ++hammer_stats_btree_elements;
1285                 elm = &node->elms[i];
1286
1287                 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1288
1289                 if (hammer_debug_btree > 1)
1290                         kprintf("  ELM %p %d r=%d\n", &node->elms[i], i, r);
1291
1292                 /*
1293                  * We are at a record element.  Stop if we've flipped past
1294                  * key_beg, not counting the create_tid test.  Allow the
1295                  * r == 1 case (key_beg > element but differs only by its
1296                  * create_tid) to fall through to the AS-OF check.
1297                  */
1298                 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1299
1300                 if (r < 0)
1301                         goto failed;
1302                 if (r > 1) {
1303                         ++i;
1304                         continue;
1305                 }
1306
1307                 /*
1308                  * Check our as-of timestamp against the element.
1309                  */
1310                 if (flags & HAMMER_CURSOR_ASOF) {
1311                         if (hammer_btree_chkts(cursor->asof,
1312                                                &node->elms[i].base) != 0) {
1313                                 ++i;
1314                                 continue;
1315                         }
1316                         /* success */
1317                 } else {
1318                         if (r > 0) {    /* can only be +1 */
1319                                 ++i;
1320                                 continue;
1321                         }
1322                         /* success */
1323                 }
1324                 cursor->index = i;
1325                 error = 0;
1326                 if (hammer_debug_btree) {
1327                         kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1328                                 (long long)cursor->node->node_offset, i);
1329                 }
1330                 goto done;
1331         }
1332
1333         /*
1334          * The search of the leaf node failed.  i is the insertion point.
1335          */
1336 failed:
1337         if (hammer_debug_btree) {
1338                 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1339                         (long long)cursor->node->node_offset, i);
1340         }
1341
1342         /*
1343          * No exact match was found, i is now at the insertion point.
1344          *
1345          * If inserting split a full leaf before returning.  This
1346          * may have the side effect of adjusting cursor->node and
1347          * cursor->index.
1348          */
1349         cursor->index = i;
1350         if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1351              btree_node_is_full(node)) {
1352                 error = btree_split_leaf(cursor);
1353                 if (error) {
1354                         if (error != ENOSPC)
1355                                 goto done;
1356                         enospc = 1;
1357                 }
1358                 /*
1359                  * reload stale pointers
1360                  */
1361                 /* NOT USED
1362                 i = cursor->index;
1363                 node = &cursor->node->internal;
1364                 */
1365         }
1366
1367         /*
1368          * We reached a leaf but did not find the key we were looking for.
1369          * If this is an insert we will be properly positioned for an insert
1370          * (ENOENT) or spike (ENOSPC) operation.
1371          */
1372         error = enospc ? ENOSPC : ENOENT;
1373 done:
1374         return(error);
1375 }
1376
1377 /*
1378  * Heuristical search for the first element whos comparison is <= 1.  May
1379  * return an index whos compare result is > 1 but may only return an index
1380  * whos compare result is <= 1 if it is the first element with that result.
1381  */
1382 int
1383 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1384 {
1385         int b;
1386         int s;
1387         int i;
1388         int r;
1389
1390         /*
1391          * Don't bother if the node does not have very many elements
1392          */
1393         b = 0;
1394         s = node->count;
1395         while (s - b > 4) {
1396                 i = b + (s - b) / 2;
1397                 ++hammer_stats_btree_elements;
1398                 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1399                 if (r <= 1) {
1400                         s = i;
1401                 } else {
1402                         b = i;
1403                 }
1404         }
1405         return(b);
1406 }
1407
1408
1409 /************************************************************************
1410  *                         SPLITTING AND MERGING                        *
1411  ************************************************************************
1412  *
1413  * These routines do all the dirty work required to split and merge nodes.
1414  */
1415
1416 /*
1417  * Split an internal node into two nodes and move the separator at the split
1418  * point to the parent.
1419  *
1420  * (cursor->node, cursor->index) indicates the element the caller intends
1421  * to push into.  We will adjust node and index if that element winds
1422  * up in the split node.
1423  *
1424  * If we are at the root of the filesystem a new root must be created with
1425  * two elements, one pointing to the original root and one pointing to the
1426  * newly allocated split node.
1427  */
1428 static
1429 int
1430 btree_split_internal(hammer_cursor_t cursor)
1431 {
1432         hammer_node_ondisk_t ondisk;
1433         hammer_node_t node;
1434         hammer_node_t parent;
1435         hammer_node_t new_node;
1436         hammer_btree_elm_t elm;
1437         hammer_btree_elm_t parent_elm;
1438         struct hammer_node_lock lockroot;
1439         hammer_mount_t hmp = cursor->trans->hmp;
1440         hammer_off_t hint;
1441         int parent_index;
1442         int made_root;
1443         int split;
1444         int error;
1445         int i;
1446         const int esize = sizeof(*elm);
1447
1448         hammer_node_lock_init(&lockroot, cursor->node);
1449         error = hammer_btree_lock_children(cursor, 1, &lockroot);
1450         if (error)
1451                 goto done;
1452         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1453                 goto done;
1454         ++hammer_stats_btree_splits;
1455
1456         /*
1457          * We are splitting but elms[split] will be promoted to the parent,
1458          * leaving the right hand node with one less element.  If the
1459          * insertion point will be on the left-hand side adjust the split
1460          * point to give the right hand side one additional node.
1461          */
1462         node = cursor->node;
1463         ondisk = node->ondisk;
1464         split = (ondisk->count + 1) / 2;
1465         if (cursor->index <= split)
1466                 --split;
1467
1468         /*
1469          * If we are at the root of the filesystem, create a new root node
1470          * with 1 element and split normally.  Avoid making major
1471          * modifications until we know the whole operation will work.
1472          */
1473         if (ondisk->parent == 0) {
1474                 parent = hammer_alloc_btree(cursor->trans, node->node_offset,
1475                                             &error);
1476                 if (parent == NULL)
1477                         goto done;
1478                 hammer_lock_ex(&parent->lock);
1479                 hammer_modify_node_noundo(cursor->trans, parent);
1480                 ondisk = parent->ondisk;
1481                 ondisk->count = 1;
1482                 ondisk->parent = 0;
1483                 ondisk->mirror_tid = node->ondisk->mirror_tid;
1484                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1485                 ondisk->elms[0].base = hmp->root_btree_beg;
1486                 ondisk->elms[0].base.btype = node->ondisk->type;
1487                 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1488                 ondisk->elms[1].base = hmp->root_btree_end;
1489                 hammer_modify_node_done(parent);
1490                 /* ondisk->elms[1].base.btype - not used */
1491                 made_root = 1;
1492                 parent_index = 0;       /* index of current node in parent */
1493         } else {
1494                 made_root = 0;
1495                 parent = cursor->parent;
1496                 parent_index = cursor->parent_index;
1497         }
1498
1499         /*
1500          * Calculate a hint for the allocation of the new B-Tree node.
1501          * The most likely expansion is coming from the insertion point
1502          * at cursor->index, so try to localize the allocation of our
1503          * new node to accomodate that sub-tree.
1504          *
1505          * Use the right-most sub-tree when expandinging on the right edge.
1506          * This is a very common case when copying a directory tree.
1507          */
1508         if (cursor->index == ondisk->count)
1509                 hint = ondisk->elms[cursor->index - 1].internal.subtree_offset;
1510         else
1511                 hint = ondisk->elms[cursor->index].internal.subtree_offset;
1512
1513         /*
1514          * Split node into new_node at the split point.
1515          *
1516          *  B O O O P N N B     <-- P = node->elms[split] (index 4)
1517          *   0 1 2 3 4 5 6      <-- subtree indices
1518          *
1519          *       x x P x x
1520          *        s S S s
1521          *         /   \
1522          *  B O O O B    B N N B        <--- inner boundary points are 'P'
1523          *   0 1 2 3      4 5 6
1524          */
1525         new_node = hammer_alloc_btree(cursor->trans, hint, &error);
1526         if (new_node == NULL) {
1527                 if (made_root) {
1528                         hammer_unlock(&parent->lock);
1529                         hammer_delete_node(cursor->trans, parent);
1530                         hammer_rel_node(parent);
1531                 }
1532                 goto done;
1533         }
1534         hammer_lock_ex(&new_node->lock);
1535
1536         /*
1537          * Create the new node.  P becomes the left-hand boundary in the
1538          * new node.  Copy the right-hand boundary as well.
1539          *
1540          * elm is the new separator.
1541          */
1542         hammer_modify_node_noundo(cursor->trans, new_node);
1543         hammer_modify_node_all(cursor->trans, node);
1544         ondisk = node->ondisk;
1545         elm = &ondisk->elms[split];
1546         bcopy(elm, &new_node->ondisk->elms[0],
1547               (ondisk->count - split + 1) * esize);
1548         new_node->ondisk->count = ondisk->count - split;
1549         new_node->ondisk->parent = parent->node_offset;
1550         new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1551         new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1552         KKASSERT(ondisk->type == new_node->ondisk->type);
1553         hammer_cursor_split_node(node, new_node, split);
1554
1555         /*
1556          * Cleanup the original node.  Elm (P) becomes the new boundary,
1557          * its subtree_offset was moved to the new node.  If we had created
1558          * a new root its parent pointer may have changed.
1559          */
1560         elm->internal.subtree_offset = 0;
1561         ondisk->count = split;
1562
1563         /*
1564          * Insert the separator into the parent, fixup the parent's
1565          * reference to the original node, and reference the new node.
1566          * The separator is P.
1567          *
1568          * Remember that base.count does not include the right-hand boundary.
1569          */
1570         hammer_modify_node_all(cursor->trans, parent);
1571         ondisk = parent->ondisk;
1572         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1573         parent_elm = &ondisk->elms[parent_index+1];
1574         bcopy(parent_elm, parent_elm + 1,
1575               (ondisk->count - parent_index) * esize);
1576         parent_elm->internal.base = elm->base;  /* separator P */
1577         parent_elm->internal.base.btype = new_node->ondisk->type;
1578         parent_elm->internal.subtree_offset = new_node->node_offset;
1579         parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1580         ++ondisk->count;
1581         hammer_modify_node_done(parent);
1582         hammer_cursor_inserted_element(parent, parent_index + 1);
1583
1584         /*
1585          * The children of new_node need their parent pointer set to new_node.
1586          * The children have already been locked by
1587          * hammer_btree_lock_children().
1588          */
1589         for (i = 0; i < new_node->ondisk->count; ++i) {
1590                 elm = &new_node->ondisk->elms[i];
1591                 error = btree_set_parent(cursor->trans, new_node, elm);
1592                 if (error) {
1593                         panic("btree_split_internal: btree-fixup problem");
1594                 }
1595         }
1596         hammer_modify_node_done(new_node);
1597
1598         /*
1599          * The filesystem's root B-Tree pointer may have to be updated.
1600          */
1601         if (made_root) {
1602                 hammer_volume_t volume;
1603
1604                 volume = hammer_get_root_volume(hmp, &error);
1605                 KKASSERT(error == 0);
1606
1607                 hammer_modify_volume_field(cursor->trans, volume,
1608                                            vol0_btree_root);
1609                 volume->ondisk->vol0_btree_root = parent->node_offset;
1610                 hammer_modify_volume_done(volume);
1611                 node->ondisk->parent = parent->node_offset;
1612                 if (cursor->parent) {
1613                         hammer_unlock(&cursor->parent->lock);
1614                         hammer_rel_node(cursor->parent);
1615                 }
1616                 cursor->parent = parent;        /* lock'd and ref'd */
1617                 hammer_rel_volume(volume, 0);
1618         }
1619         hammer_modify_node_done(node);
1620
1621         /*
1622          * Ok, now adjust the cursor depending on which element the original
1623          * index was pointing at.  If we are >= the split point the push node
1624          * is now in the new node.
1625          *
1626          * NOTE: If we are at the split point itself we cannot stay with the
1627          * original node because the push index will point at the right-hand
1628          * boundary, which is illegal.
1629          *
1630          * NOTE: The cursor's parent or parent_index must be adjusted for
1631          * the case where a new parent (new root) was created, and the case
1632          * where the cursor is now pointing at the split node.
1633          */
1634         if (cursor->index >= split) {
1635                 cursor->parent_index = parent_index + 1;
1636                 cursor->index -= split;
1637                 hammer_unlock(&cursor->node->lock);
1638                 hammer_rel_node(cursor->node);
1639                 cursor->node = new_node;        /* locked and ref'd */
1640         } else {
1641                 cursor->parent_index = parent_index;
1642                 hammer_unlock(&new_node->lock);
1643                 hammer_rel_node(new_node);
1644         }
1645
1646         /*
1647          * Fixup left and right bounds
1648          */
1649         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1650         cursor->left_bound = &parent_elm[0].internal.base;
1651         cursor->right_bound = &parent_elm[1].internal.base;
1652         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1653                  &cursor->node->ondisk->elms[0].internal.base) <= 0);
1654         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1655                  &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1656
1657 done:
1658         hammer_btree_unlock_children(cursor, &lockroot);
1659         hammer_cursor_downgrade(cursor);
1660         return (error);
1661 }
1662
1663 /*
1664  * Same as the above, but splits a full leaf node.
1665  *
1666  * This function
1667  */
1668 static
1669 int
1670 btree_split_leaf(hammer_cursor_t cursor)
1671 {
1672         hammer_node_ondisk_t ondisk;
1673         hammer_node_t parent;
1674         hammer_node_t leaf;
1675         hammer_mount_t hmp;
1676         hammer_node_t new_leaf;
1677         hammer_btree_elm_t elm;
1678         hammer_btree_elm_t parent_elm;
1679         hammer_base_elm_t mid_boundary;
1680         hammer_off_t hint;
1681         int parent_index;
1682         int made_root;
1683         int split;
1684         int error;
1685         const size_t esize = sizeof(*elm);
1686
1687         if ((error = hammer_cursor_upgrade(cursor)) != 0)
1688                 return(error);
1689         ++hammer_stats_btree_splits;
1690
1691         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1692                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1693         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1694                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1695
1696         /*
1697          * Calculate the split point.  If the insertion point will be on
1698          * the left-hand side adjust the split point to give the right
1699          * hand side one additional node.
1700          *
1701          * Spikes are made up of two leaf elements which cannot be
1702          * safely split.
1703          */
1704         leaf = cursor->node;
1705         ondisk = leaf->ondisk;
1706         KKASSERT(ondisk->count > 2);
1707         split = (ondisk->count + 1) / 2;
1708         if (cursor->index <= split)
1709                 --split;
1710         error = 0;
1711         hmp = leaf->hmp;
1712
1713         elm = &ondisk->elms[split];
1714
1715         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1716         KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1717         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1718         KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1719
1720         /*
1721          * If we are at the root of the tree, create a new root node with
1722          * 1 element and split normally.  Avoid making major modifications
1723          * until we know the whole operation will work.
1724          */
1725         if (ondisk->parent == 0) {
1726                 parent = hammer_alloc_btree(cursor->trans, leaf->node_offset,
1727                                             &error);
1728                 if (parent == NULL)
1729                         goto done;
1730                 hammer_lock_ex(&parent->lock);
1731                 hammer_modify_node_noundo(cursor->trans, parent);
1732                 ondisk = parent->ondisk;
1733                 ondisk->count = 1;
1734                 ondisk->parent = 0;
1735                 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1736                 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1737                 ondisk->elms[0].base = hmp->root_btree_beg;
1738                 ondisk->elms[0].base.btype = leaf->ondisk->type;
1739                 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1740                 ondisk->elms[1].base = hmp->root_btree_end;
1741                 /* ondisk->elms[1].base.btype = not used */
1742                 hammer_modify_node_done(parent);
1743                 made_root = 1;
1744                 parent_index = 0;       /* insertion point in parent */
1745         } else {
1746                 made_root = 0;
1747                 parent = cursor->parent;
1748                 parent_index = cursor->parent_index;
1749         }
1750
1751         /*
1752          * Calculate a hint for the allocation of the new B-Tree leaf node.
1753          * For now just try to localize it within the same bigblock as
1754          * the current leaf.
1755          *
1756          * If the insertion point is at the end of the leaf we recognize a
1757          * likely append sequence of some sort (data, meta-data, inodes,
1758          * whatever).  Set the hint to zero to allocate out of linear space
1759          * instead of trying to completely fill previously hinted space.
1760          *
1761          * This also sets the stage for recursive splits to localize using
1762          * the new space.
1763          */
1764         ondisk = leaf->ondisk;
1765         if (cursor->index == ondisk->count)
1766                 hint = 0;
1767         else
1768                 hint = leaf->node_offset;
1769
1770         /*
1771          * Split leaf into new_leaf at the split point.  Select a separator
1772          * value in-between the two leafs but with a bent towards the right
1773          * leaf since comparisons use an 'elm >= separator' inequality.
1774          *
1775          *  L L L L L L L L
1776          *
1777          *       x x P x x
1778          *        s S S s
1779          *         /   \
1780          *  L L L L     L L L L
1781          */
1782         new_leaf = hammer_alloc_btree(cursor->trans, hint, &error);
1783         if (new_leaf == NULL) {
1784                 if (made_root) {
1785                         hammer_unlock(&parent->lock);
1786                         hammer_delete_node(cursor->trans, parent);
1787                         hammer_rel_node(parent);
1788                 }
1789                 goto done;
1790         }
1791         hammer_lock_ex(&new_leaf->lock);
1792
1793         /*
1794          * Create the new node and copy the leaf elements from the split
1795          * point on to the new node.
1796          */
1797         hammer_modify_node_all(cursor->trans, leaf);
1798         hammer_modify_node_noundo(cursor->trans, new_leaf);
1799         ondisk = leaf->ondisk;
1800         elm = &ondisk->elms[split];
1801         bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1802         new_leaf->ondisk->count = ondisk->count - split;
1803         new_leaf->ondisk->parent = parent->node_offset;
1804         new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1805         new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1806         KKASSERT(ondisk->type == new_leaf->ondisk->type);
1807         hammer_modify_node_done(new_leaf);
1808         hammer_cursor_split_node(leaf, new_leaf, split);
1809
1810         /*
1811          * Cleanup the original node.  Because this is a leaf node and
1812          * leaf nodes do not have a right-hand boundary, there
1813          * aren't any special edge cases to clean up.  We just fixup the
1814          * count.
1815          */
1816         ondisk->count = split;
1817
1818         /*
1819          * Insert the separator into the parent, fixup the parent's
1820          * reference to the original node, and reference the new node.
1821          * The separator is P.
1822          *
1823          * Remember that base.count does not include the right-hand boundary.
1824          * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1825          */
1826         hammer_modify_node_all(cursor->trans, parent);
1827         ondisk = parent->ondisk;
1828         KKASSERT(split != 0);
1829         KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1830         parent_elm = &ondisk->elms[parent_index+1];
1831         bcopy(parent_elm, parent_elm + 1,
1832               (ondisk->count - parent_index) * esize);
1833
1834         hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1835         parent_elm->internal.base.btype = new_leaf->ondisk->type;
1836         parent_elm->internal.subtree_offset = new_leaf->node_offset;
1837         parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1838         mid_boundary = &parent_elm->base;
1839         ++ondisk->count;
1840         hammer_modify_node_done(parent);
1841         hammer_cursor_inserted_element(parent, parent_index + 1);
1842
1843         /*
1844          * The filesystem's root B-Tree pointer may have to be updated.
1845          */
1846         if (made_root) {
1847                 hammer_volume_t volume;
1848
1849                 volume = hammer_get_root_volume(hmp, &error);
1850                 KKASSERT(error == 0);
1851
1852                 hammer_modify_volume_field(cursor->trans, volume,
1853                                            vol0_btree_root);
1854                 volume->ondisk->vol0_btree_root = parent->node_offset;
1855                 hammer_modify_volume_done(volume);
1856                 leaf->ondisk->parent = parent->node_offset;
1857                 if (cursor->parent) {
1858                         hammer_unlock(&cursor->parent->lock);
1859                         hammer_rel_node(cursor->parent);
1860                 }
1861                 cursor->parent = parent;        /* lock'd and ref'd */
1862                 hammer_rel_volume(volume, 0);
1863         }
1864         hammer_modify_node_done(leaf);
1865
1866         /*
1867          * Ok, now adjust the cursor depending on which element the original
1868          * index was pointing at.  If we are >= the split point the push node
1869          * is now in the new node.
1870          *
1871          * NOTE: If we are at the split point itself we need to select the
1872          * old or new node based on where key_beg's insertion point will be.
1873          * If we pick the wrong side the inserted element will wind up in
1874          * the wrong leaf node and outside that node's bounds.
1875          */
1876         if (cursor->index > split ||
1877             (cursor->index == split &&
1878              hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
1879                 cursor->parent_index = parent_index + 1;
1880                 cursor->index -= split;
1881                 hammer_unlock(&cursor->node->lock);
1882                 hammer_rel_node(cursor->node);
1883                 cursor->node = new_leaf;
1884         } else {
1885                 cursor->parent_index = parent_index;
1886                 hammer_unlock(&new_leaf->lock);
1887                 hammer_rel_node(new_leaf);
1888         }
1889
1890         /*
1891          * Fixup left and right bounds
1892          */
1893         parent_elm = &parent->ondisk->elms[cursor->parent_index];
1894         cursor->left_bound = &parent_elm[0].internal.base;
1895         cursor->right_bound = &parent_elm[1].internal.base;
1896
1897         /*
1898          * Assert that the bounds are correct.
1899          */
1900         KKASSERT(hammer_btree_cmp(cursor->left_bound,
1901                  &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1902         KKASSERT(hammer_btree_cmp(cursor->right_bound,
1903                  &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1904         KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
1905         KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
1906
1907 done:
1908         hammer_cursor_downgrade(cursor);
1909         return (error);
1910 }
1911
1912 #if 0
1913
1914 /*
1915  * Recursively correct the right-hand boundary's create_tid to (tid) as
1916  * long as the rest of the key matches.  We have to recurse upward in
1917  * the tree as well as down the left side of each parent's right node.
1918  *
1919  * Return EDEADLK if we were only partially successful, forcing the caller
1920  * to try again.  The original cursor is not modified.  This routine can
1921  * also fail with EDEADLK if it is forced to throw away a portion of its
1922  * record history.
1923  *
1924  * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
1925  */
1926 struct hammer_rhb {
1927         TAILQ_ENTRY(hammer_rhb) entry;
1928         hammer_node_t   node;
1929         int             index;
1930 };
1931
1932 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
1933
1934 int
1935 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
1936 {
1937         struct hammer_mount *hmp;
1938         struct hammer_rhb_list rhb_list;
1939         hammer_base_elm_t elm;
1940         hammer_node_t orig_node;
1941         struct hammer_rhb *rhb;
1942         int orig_index;
1943         int error;
1944
1945         TAILQ_INIT(&rhb_list);
1946         hmp = cursor->trans->hmp;
1947
1948         /*
1949          * Save our position so we can restore it on return.  This also
1950          * gives us a stable 'elm'.
1951          */
1952         orig_node = cursor->node;
1953         hammer_ref_node(orig_node);
1954         hammer_lock_sh(&orig_node->lock);
1955         orig_index = cursor->index;
1956         elm = &orig_node->ondisk->elms[orig_index].base;
1957
1958         /*
1959          * Now build a list of parents going up, allocating a rhb
1960          * structure for each one.
1961          */
1962         while (cursor->parent) {
1963                 /*
1964                  * Stop if we no longer have any right-bounds to fix up
1965                  */
1966                 if (elm->obj_id != cursor->right_bound->obj_id ||
1967                     elm->rec_type != cursor->right_bound->rec_type ||
1968                     elm->key != cursor->right_bound->key) {
1969                         break;
1970                 }
1971
1972                 /*
1973                  * Stop if the right-hand bound's create_tid does not
1974                  * need to be corrected.
1975                  */
1976                 if (cursor->right_bound->create_tid >= tid)
1977                         break;
1978
1979                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
1980                 rhb->node = cursor->parent;
1981                 rhb->index = cursor->parent_index;
1982                 hammer_ref_node(rhb->node);
1983                 hammer_lock_sh(&rhb->node->lock);
1984                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
1985
1986                 hammer_cursor_up(cursor);
1987         }
1988
1989         /*
1990          * now safely adjust the right hand bound for each rhb.  This may
1991          * also require taking the right side of the tree and iterating down
1992          * ITS left side.
1993          */
1994         error = 0;
1995         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
1996                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
1997                 if (error)
1998                         break;
1999                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2000                 hammer_unlock(&rhb->node->lock);
2001                 hammer_rel_node(rhb->node);
2002                 kfree(rhb, hmp->m_misc);
2003
2004                 switch (cursor->node->ondisk->type) {
2005                 case HAMMER_BTREE_TYPE_INTERNAL:
2006                         /*
2007                          * Right-boundary for parent at internal node
2008                          * is one element to the right of the element whos
2009                          * right boundary needs adjusting.  We must then
2010                          * traverse down the left side correcting any left
2011                          * bounds (which may now be too far to the left).
2012                          */
2013                         ++cursor->index;
2014                         error = hammer_btree_correct_lhb(cursor, tid);
2015                         break;
2016                 default:
2017                         panic("hammer_btree_correct_rhb(): Bad node type");
2018                         error = EINVAL;
2019                         break;
2020                 }
2021         }
2022
2023         /*
2024          * Cleanup
2025          */
2026         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2027                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2028                 hammer_unlock(&rhb->node->lock);
2029                 hammer_rel_node(rhb->node);
2030                 kfree(rhb, hmp->m_misc);
2031         }
2032         error = hammer_cursor_seek(cursor, orig_node, orig_index);
2033         hammer_unlock(&orig_node->lock);
2034         hammer_rel_node(orig_node);
2035         return (error);
2036 }
2037
2038 /*
2039  * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2040  * bound going downward starting at the current cursor position.
2041  *
2042  * This function does not restore the cursor after use.
2043  */
2044 int
2045 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2046 {
2047         struct hammer_rhb_list rhb_list;
2048         hammer_base_elm_t elm;
2049         hammer_base_elm_t cmp;
2050         struct hammer_rhb *rhb;
2051         struct hammer_mount *hmp;
2052         int error;
2053
2054         TAILQ_INIT(&rhb_list);
2055         hmp = cursor->trans->hmp;
2056
2057         cmp = &cursor->node->ondisk->elms[cursor->index].base;
2058
2059         /*
2060          * Record the node and traverse down the left-hand side for all
2061          * matching records needing a boundary correction.
2062          */
2063         error = 0;
2064         for (;;) {
2065                 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2066                 rhb->node = cursor->node;
2067                 rhb->index = cursor->index;
2068                 hammer_ref_node(rhb->node);
2069                 hammer_lock_sh(&rhb->node->lock);
2070                 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2071
2072                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2073                         /*
2074                          * Nothing to traverse down if we are at the right
2075                          * boundary of an internal node.
2076                          */
2077                         if (cursor->index == cursor->node->ondisk->count)
2078                                 break;
2079                 } else {
2080                         elm = &cursor->node->ondisk->elms[cursor->index].base;
2081                         if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2082                                 break;
2083                         panic("Illegal leaf record type %02x", elm->btype);
2084                 }
2085                 error = hammer_cursor_down(cursor);
2086                 if (error)
2087                         break;
2088
2089                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2090                 if (elm->obj_id != cmp->obj_id ||
2091                     elm->rec_type != cmp->rec_type ||
2092                     elm->key != cmp->key) {
2093                         break;
2094                 }
2095                 if (elm->create_tid >= tid)
2096                         break;
2097
2098         }
2099
2100         /*
2101          * Now we can safely adjust the left-hand boundary from the bottom-up.
2102          * The last element we remove from the list is the caller's right hand
2103          * boundary, which must also be adjusted.
2104          */
2105         while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2106                 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2107                 if (error)
2108                         break;
2109                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2110                 hammer_unlock(&rhb->node->lock);
2111                 hammer_rel_node(rhb->node);
2112                 kfree(rhb, hmp->m_misc);
2113
2114                 elm = &cursor->node->ondisk->elms[cursor->index].base;
2115                 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2116                         hammer_modify_node(cursor->trans, cursor->node,
2117                                            &elm->create_tid,
2118                                            sizeof(elm->create_tid));
2119                         elm->create_tid = tid;
2120                         hammer_modify_node_done(cursor->node);
2121                 } else {
2122                         panic("hammer_btree_correct_lhb(): Bad element type");
2123                 }
2124         }
2125
2126         /*
2127          * Cleanup
2128          */
2129         while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2130                 TAILQ_REMOVE(&rhb_list, rhb, entry);
2131                 hammer_unlock(&rhb->node->lock);
2132                 hammer_rel_node(rhb->node);
2133                 kfree(rhb, hmp->m_misc);
2134         }
2135         return (error);
2136 }
2137
2138 #endif
2139
2140 /*
2141  * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2142  * (cursor->node).  Returns 0 on success, EDEADLK if we could not complete
2143  * the operation due to a deadlock, or some other error.
2144  *
2145  * This routine is initially called with an empty leaf and may be
2146  * recursively called with single-element internal nodes.
2147  *
2148  * It should also be noted that when removing empty leaves we must be sure
2149  * to test and update mirror_tid because another thread may have deadlocked
2150  * against us (or someone) trying to propagate it up and cannot retry once
2151  * the node has been deleted.
2152  *
2153  * On return the cursor may end up pointing to an internal node, suitable
2154  * for further iteration but not for an immediate insertion or deletion.
2155  */
2156 static int
2157 btree_remove(hammer_cursor_t cursor)
2158 {
2159         hammer_node_ondisk_t ondisk;
2160         hammer_btree_elm_t elm;
2161         hammer_node_t node;
2162         hammer_node_t parent;
2163         const int esize = sizeof(*elm);
2164         int error;
2165
2166         node = cursor->node;
2167
2168         /*
2169          * When deleting the root of the filesystem convert it to
2170          * an empty leaf node.  Internal nodes cannot be empty.
2171          */
2172         ondisk = node->ondisk;
2173         if (ondisk->parent == 0) {
2174                 KKASSERT(cursor->parent == NULL);
2175                 hammer_modify_node_all(cursor->trans, node);
2176                 KKASSERT(ondisk == node->ondisk);
2177                 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2178                 ondisk->count = 0;
2179                 hammer_modify_node_done(node);
2180                 cursor->index = 0;
2181                 return(0);
2182         }
2183
2184         parent = cursor->parent;
2185         hammer_cursor_removed_node(node, parent, cursor->parent_index);
2186
2187         /*
2188          * Attempt to remove the parent's reference to the child.  If the
2189          * parent would become empty we have to recurse.  If we fail we
2190          * leave the parent pointing to an empty leaf node.
2191          *
2192          * We have to recurse successfully before we can delete the internal
2193          * node as it is illegal to have empty internal nodes.  Even though
2194          * the operation may be aborted we must still fixup any unlocked
2195          * cursors as if we had deleted the element prior to recursing
2196          * (by calling hammer_cursor_deleted_element()) so those cursors
2197          * are properly forced up the chain by the recursion.
2198          */
2199         if (parent->ondisk->count == 1) {
2200                 /*
2201                  * This special cursor_up_locked() call leaves the original
2202                  * node exclusively locked and referenced, leaves the
2203                  * original parent locked (as the new node), and locks the
2204                  * new parent.  It can return EDEADLK.
2205                  */
2206                 error = hammer_cursor_up_locked(cursor);
2207                 if (error == 0) {
2208                         hammer_cursor_deleted_element(cursor->node, 0);
2209                         error = btree_remove(cursor);
2210                         if (error == 0) {
2211                                 hammer_modify_node_all(cursor->trans, node);
2212                                 ondisk = node->ondisk;
2213                                 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2214                                 ondisk->count = 0;
2215                                 hammer_modify_node_done(node);
2216                                 hammer_flush_node(node);
2217                                 hammer_delete_node(cursor->trans, node);
2218                         } else {
2219                                 /*
2220                                  * Defer parent removal because we could not
2221                                  * get the lock, just let the leaf remain
2222                                  * empty.
2223                                  */
2224                                 /**/
2225                         }
2226                         hammer_unlock(&node->lock);
2227                         hammer_rel_node(node);
2228                 } else {
2229                         /*
2230                          * Defer parent removal because we could not
2231                          * get the lock, just let the leaf remain
2232                          * empty.
2233                          */
2234                         /**/
2235                 }
2236         } else {
2237                 KKASSERT(parent->ondisk->count > 1);
2238
2239                 hammer_modify_node_all(cursor->trans, parent);
2240                 ondisk = parent->ondisk;
2241                 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2242
2243                 elm = &ondisk->elms[cursor->parent_index];
2244                 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2245                 KKASSERT(ondisk->count > 0);
2246
2247                 /*
2248                  * We must retain the highest mirror_tid.  The deleted
2249                  * range is now encompassed by the element to the left.
2250                  * If we are already at the left edge the new left edge
2251                  * inherits mirror_tid.
2252                  *
2253                  * Note that bounds of the parent to our parent may create
2254                  * a gap to the left of our left-most node or to the right
2255                  * of our right-most node.  The gap is silently included
2256                  * in the mirror_tid's area of effect from the point of view
2257                  * of the scan.
2258                  */
2259                 if (cursor->parent_index) {
2260                         if (elm[-1].internal.mirror_tid <
2261                             elm[0].internal.mirror_tid) {
2262                                 elm[-1].internal.mirror_tid =
2263                                     elm[0].internal.mirror_tid;
2264                         }
2265                 } else {
2266                         if (elm[1].internal.mirror_tid <
2267                             elm[0].internal.mirror_tid) {
2268                                 elm[1].internal.mirror_tid =
2269                                     elm[0].internal.mirror_tid;
2270                         }
2271                 }
2272
2273                 /*
2274                  * Delete the subtree reference in the parent
2275                  */
2276                 bcopy(&elm[1], &elm[0],
2277                       (ondisk->count - cursor->parent_index) * esize);
2278                 --ondisk->count;
2279                 hammer_modify_node_done(parent);
2280                 hammer_cursor_deleted_element(parent, cursor->parent_index);
2281                 hammer_flush_node(node);
2282                 hammer_delete_node(cursor->trans, node);
2283
2284                 /*
2285                  * cursor->node is invalid, cursor up to make the cursor
2286                  * valid again.
2287                  */
2288                 error = hammer_cursor_up(cursor);
2289         }
2290         return (error);
2291 }
2292
2293 /*
2294  * Propagate cursor->trans->tid up the B-Tree starting at the current
2295  * cursor position using pseudofs info gleaned from the passed inode.
2296  *
2297  * The passed inode has no relationship to the cursor position other
2298  * then being in the same pseudofs as the insertion or deletion we
2299  * are propagating the mirror_tid for.
2300  *
2301  * WARNING!  Because we push and pop the passed cursor, it may be
2302  *           modified by other B-Tree operations while it is unlocked
2303  *           and things like the node & leaf pointers, and indexes might
2304  *           change.
2305  */
2306 void
2307 hammer_btree_do_propagation(hammer_cursor_t cursor,
2308                             hammer_pseudofs_inmem_t pfsm,
2309                             hammer_btree_leaf_elm_t leaf)
2310 {
2311         hammer_cursor_t ncursor;
2312         hammer_tid_t mirror_tid;
2313         int error;
2314
2315         /*
2316          * We do not propagate a mirror_tid if the filesystem was mounted
2317          * in no-mirror mode.
2318          */
2319         if (cursor->trans->hmp->master_id < 0)
2320                 return;
2321
2322         /*
2323          * This is a bit of a hack because we cannot deadlock or return
2324          * EDEADLK here.  The related operation has already completed and
2325          * we must propagate the mirror_tid now regardless.
2326          *
2327          * Generate a new cursor which inherits the original's locks and
2328          * unlock the original.  Use the new cursor to propagate the
2329          * mirror_tid.  Then clean up the new cursor and reacquire locks
2330          * on the original.
2331          *
2332          * hammer_dup_cursor() cannot dup locks.  The dup inherits the
2333          * original's locks and the original is tracked and must be
2334          * re-locked.
2335          */
2336         mirror_tid = cursor->node->ondisk->mirror_tid;
2337         KKASSERT(mirror_tid != 0);
2338         ncursor = hammer_push_cursor(cursor);
2339         error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2340         KKASSERT(error == 0);
2341         hammer_pop_cursor(cursor, ncursor);
2342         /* WARNING: cursor's leaf pointer may change after pop */
2343 }
2344
2345
2346 /*
2347  * Propagate a mirror TID update upwards through the B-Tree to the root.
2348  *
2349  * A locked internal node must be passed in.  The node will remain locked
2350  * on return.
2351  *
2352  * This function syncs mirror_tid at the specified internal node's element,
2353  * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2354  */
2355 static int
2356 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2357 {
2358         hammer_btree_internal_elm_t elm;
2359         hammer_node_t node;
2360         int error;
2361
2362         for (;;) {
2363                 error = hammer_cursor_up(cursor);
2364                 if (error == 0)
2365                         error = hammer_cursor_upgrade(cursor);
2366                 while (error == EDEADLK) {
2367                         hammer_recover_cursor(cursor);
2368                         error = hammer_cursor_upgrade(cursor);
2369                 }
2370                 if (error)
2371                         break;
2372                 node = cursor->node;
2373                 KKASSERT (node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2374
2375                 /*
2376                  * Adjust the node's element
2377                  */
2378                 elm = &node->ondisk->elms[cursor->index].internal;
2379                 if (elm->mirror_tid >= mirror_tid)
2380                         break;
2381                 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2382                                    sizeof(elm->mirror_tid));
2383                 elm->mirror_tid = mirror_tid;
2384                 hammer_modify_node_done(node);
2385                 if (hammer_debug_general & 0x0002) {
2386                         kprintf("mirror_propagate: propagate "
2387                                 "%016llx @%016llx:%d\n",
2388                                 (long long)mirror_tid,
2389                                 (long long)node->node_offset,
2390                                 cursor->index);
2391                 }
2392
2393
2394                 /*
2395                  * Adjust the node's mirror_tid aggregator
2396                  */
2397                 if (node->ondisk->mirror_tid >= mirror_tid)
2398                         return(0);
2399                 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2400                 node->ondisk->mirror_tid = mirror_tid;
2401                 hammer_modify_node_done(node);
2402                 if (hammer_debug_general & 0x0002) {
2403                         kprintf("mirror_propagate: propagate "
2404                                 "%016llx @%016llx\n",
2405                                 (long long)mirror_tid,
2406                                 (long long)node->node_offset);
2407                 }
2408         }
2409         if (error == ENOENT)
2410                 error = 0;
2411         return(error);
2412 }
2413
2414 hammer_node_t
2415 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2416                         int *parent_indexp, int *errorp, int try_exclusive)
2417 {
2418         hammer_node_t parent;
2419         hammer_btree_elm_t elm;
2420         int i;
2421
2422         /*
2423          * Get the node
2424          */
2425         parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2426         if (*errorp) {
2427                 KKASSERT(parent == NULL);
2428                 return(NULL);
2429         }
2430         KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2431
2432         /*
2433          * Lock the node
2434          */
2435         if (try_exclusive) {
2436                 if (hammer_lock_ex_try(&parent->lock)) {
2437                         hammer_rel_node(parent);
2438                         *errorp = EDEADLK;
2439                         return(NULL);
2440                 }
2441         } else {
2442                 hammer_lock_sh(&parent->lock);
2443         }
2444
2445         /*
2446          * Figure out which element in the parent is pointing to the
2447          * child.
2448          */
2449         if (node->ondisk->count) {
2450                 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2451                                              parent->ondisk);
2452         } else {
2453                 i = 0;
2454         }
2455         while (i < parent->ondisk->count) {
2456                 elm = &parent->ondisk->elms[i];
2457                 if (elm->internal.subtree_offset == node->node_offset)
2458                         break;
2459                 ++i;
2460         }
2461         if (i == parent->ondisk->count) {
2462                 hammer_unlock(&parent->lock);
2463                 panic("Bad B-Tree link: parent %p node %p\n", parent, node);
2464         }
2465         *parent_indexp = i;
2466         KKASSERT(*errorp == 0);
2467         return(parent);
2468 }
2469
2470 /*
2471  * The element (elm) has been moved to a new internal node (node).
2472  *
2473  * If the element represents a pointer to an internal node that node's
2474  * parent must be adjusted to the element's new location.
2475  *
2476  * XXX deadlock potential here with our exclusive locks
2477  */
2478 int
2479 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2480                  hammer_btree_elm_t elm)
2481 {
2482         hammer_node_t child;
2483         int error;
2484
2485         error = 0;
2486
2487         switch(elm->base.btype) {
2488         case HAMMER_BTREE_TYPE_INTERNAL:
2489         case HAMMER_BTREE_TYPE_LEAF:
2490                 child = hammer_get_node(trans, elm->internal.subtree_offset,
2491                                         0, &error);
2492                 if (error == 0) {
2493                         hammer_modify_node_field(trans, child, parent);
2494                         child->ondisk->parent = node->node_offset;
2495                         hammer_modify_node_done(child);
2496                         hammer_rel_node(child);
2497                 }
2498                 break;
2499         default:
2500                 break;
2501         }
2502         return(error);
2503 }
2504
2505 /*
2506  * Initialize the root of a recursive B-Tree node lock list structure.
2507  */
2508 void
2509 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2510 {
2511         TAILQ_INIT(&parent->list);
2512         parent->parent = NULL;
2513         parent->node = node;
2514         parent->index = -1;
2515         parent->count = node->ondisk->count;
2516         parent->copy = NULL;
2517         parent->flags = 0;
2518 }
2519
2520 /*
2521  * Exclusively lock all the children of node.  This is used by the split
2522  * code to prevent anyone from accessing the children of a cursor node
2523  * while we fix-up its parent offset.
2524  *
2525  * If we don't lock the children we can really mess up cursors which block
2526  * trying to cursor-up into our node.
2527  *
2528  * On failure EDEADLK (or some other error) is returned.  If a deadlock
2529  * error is returned the cursor is adjusted to block on termination.
2530  *
2531  * The caller is responsible for managing parent->node, the root's node
2532  * is usually aliased from a cursor.
2533  */
2534 int
2535 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2536                            hammer_node_lock_t parent)
2537 {
2538         hammer_node_t node;
2539         hammer_node_lock_t item;
2540         hammer_node_ondisk_t ondisk;
2541         hammer_btree_elm_t elm;
2542         hammer_node_t child;
2543         struct hammer_mount *hmp;
2544         int error;
2545         int i;
2546
2547         node = parent->node;
2548         ondisk = node->ondisk;
2549         error = 0;
2550         hmp = cursor->trans->hmp;
2551
2552         /*
2553          * We really do not want to block on I/O with exclusive locks held,
2554          * pre-get the children before trying to lock the mess.  This is
2555          * only done one-level deep for now.
2556          */
2557         for (i = 0; i < ondisk->count; ++i) {
2558                 ++hammer_stats_btree_elements;
2559                 elm = &ondisk->elms[i];
2560                 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2561                     elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2562                         continue;
2563                 }
2564                 child = hammer_get_node(cursor->trans,
2565                                         elm->internal.subtree_offset,
2566                                         0, &error);
2567                 if (child)
2568                         hammer_rel_node(child);
2569         }
2570
2571         /*
2572          * Do it for real
2573          */
2574         for (i = 0; error == 0 && i < ondisk->count; ++i) {
2575                 ++hammer_stats_btree_elements;
2576                 elm = &ondisk->elms[i];
2577
2578                 switch(elm->base.btype) {
2579                 case HAMMER_BTREE_TYPE_INTERNAL:
2580                 case HAMMER_BTREE_TYPE_LEAF:
2581                         KKASSERT(elm->internal.subtree_offset != 0);
2582                         child = hammer_get_node(cursor->trans,
2583                                                 elm->internal.subtree_offset,
2584                                                 0, &error);
2585                         break;
2586                 default:
2587                         child = NULL;
2588                         break;
2589                 }
2590                 if (child) {
2591                         if (hammer_lock_ex_try(&child->lock) != 0) {
2592                                 if (cursor->deadlk_node == NULL) {
2593                                         cursor->deadlk_node = child;
2594                                         hammer_ref_node(cursor->deadlk_node);
2595                                 }
2596                                 error = EDEADLK;
2597                                 hammer_rel_node(child);
2598                         } else {
2599                                 item = kmalloc(sizeof(*item), hmp->m_misc,
2600                                                M_WAITOK|M_ZERO);
2601                                 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2602                                 TAILQ_INIT(&item->list);
2603                                 item->parent = parent;
2604                                 item->node = child;
2605                                 item->index = i;
2606                                 item->count = child->ondisk->count;
2607
2608                                 /*
2609                                  * Recurse (used by the rebalancing code)
2610                                  */
2611                                 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2612                                         error = hammer_btree_lock_children(
2613                                                         cursor,
2614                                                         depth - 1,
2615                                                         item);
2616                                 }
2617                         }
2618                 }
2619         }
2620         if (error)
2621                 hammer_btree_unlock_children(cursor, parent);
2622         return(error);
2623 }
2624
2625 /*
2626  * Create an in-memory copy of all B-Tree nodes listed, recursively,
2627  * including the parent.
2628  */
2629 void
2630 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2631 {
2632         hammer_mount_t hmp = cursor->trans->hmp;
2633         hammer_node_lock_t item;
2634
2635         if (parent->copy == NULL) {
2636                 parent->copy = kmalloc(sizeof(*parent->copy), hmp->m_misc,
2637                                        M_WAITOK);
2638                 *parent->copy = *parent->node->ondisk;
2639         }
2640         TAILQ_FOREACH(item, &parent->list, entry) {
2641                 hammer_btree_lock_copy(cursor, item);
2642         }
2643 }
2644
2645 /*
2646  * Recursively sync modified copies to the media.
2647  */
2648 int
2649 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2650 {
2651         hammer_node_lock_t item;
2652         int count = 0;
2653
2654         if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2655                 ++count;
2656                 hammer_modify_node_all(cursor->trans, parent->node);
2657                 *parent->node->ondisk = *parent->copy;
2658                 hammer_modify_node_done(parent->node);
2659                 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2660                         hammer_flush_node(parent->node);
2661                         hammer_delete_node(cursor->trans, parent->node);
2662                 }
2663         }
2664         TAILQ_FOREACH(item, &parent->list, entry) {
2665                 count += hammer_btree_sync_copy(cursor, item);
2666         }
2667         return(count);
2668 }
2669
2670 /*
2671  * Release previously obtained node locks.  The caller is responsible for
2672  * cleaning up parent->node itself (its usually just aliased from a cursor),
2673  * but this function will take care of the copies.
2674  */
2675 void
2676 hammer_btree_unlock_children(hammer_cursor_t cursor, hammer_node_lock_t parent)
2677 {
2678         hammer_node_lock_t item;
2679
2680         if (parent->copy) {
2681                 kfree(parent->copy, cursor->trans->hmp->m_misc);
2682                 parent->copy = NULL;    /* safety */
2683         }
2684         while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2685                 TAILQ_REMOVE(&parent->list, item, entry);
2686                 hammer_btree_unlock_children(cursor, item);
2687                 hammer_unlock(&item->node->lock);
2688                 hammer_rel_node(item->node);
2689                 kfree(item, cursor->trans->hmp->m_misc);
2690         }
2691 }
2692
2693 /************************************************************************
2694  *                         MISCELLANIOUS SUPPORT                        *
2695  ************************************************************************/
2696
2697 /*
2698  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2699  *
2700  * Note that for this particular function a return value of -1, 0, or +1
2701  * can denote a match if create_tid is otherwise discounted.  A create_tid
2702  * of zero is considered to be 'infinity' in comparisons.
2703  *
2704  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2705  */
2706 int
2707 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2708 {
2709         if (key1->localization < key2->localization)
2710                 return(-5);
2711         if (key1->localization > key2->localization)
2712                 return(5);
2713
2714         if (key1->obj_id < key2->obj_id)
2715                 return(-4);
2716         if (key1->obj_id > key2->obj_id)
2717                 return(4);
2718
2719         if (key1->rec_type < key2->rec_type)
2720                 return(-3);
2721         if (key1->rec_type > key2->rec_type)
2722                 return(3);
2723
2724         if (key1->key < key2->key)
2725                 return(-2);
2726         if (key1->key > key2->key)
2727                 return(2);
2728
2729         /*
2730          * A create_tid of zero indicates a record which is undeletable
2731          * and must be considered to have a value of positive infinity.
2732          */
2733         if (key1->create_tid == 0) {
2734                 if (key2->create_tid == 0)
2735                         return(0);
2736                 return(1);
2737         }
2738         if (key2->create_tid == 0)
2739                 return(-1);
2740         if (key1->create_tid < key2->create_tid)
2741                 return(-1);
2742         if (key1->create_tid > key2->create_tid)
2743                 return(1);
2744         return(0);
2745 }
2746
2747 /*
2748  * Test a timestamp against an element to determine whether the
2749  * element is visible.  A timestamp of 0 means 'infinity'.
2750  */
2751 int
2752 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
2753 {
2754         if (asof == 0) {
2755                 if (base->delete_tid)
2756                         return(1);
2757                 return(0);
2758         }
2759         if (asof < base->create_tid)
2760                 return(-1);
2761         if (base->delete_tid && asof >= base->delete_tid)
2762                 return(1);
2763         return(0);
2764 }
2765
2766 /*
2767  * Create a separator half way inbetween key1 and key2.  For fields just
2768  * one unit apart, the separator will match key2.  key1 is on the left-hand
2769  * side and key2 is on the right-hand side.
2770  *
2771  * key2 must be >= the separator.  It is ok for the separator to match key2.
2772  *
2773  * NOTE: Even if key1 does not match key2, the separator may wind up matching
2774  * key2.
2775  *
2776  * NOTE: It might be beneficial to just scrap this whole mess and just
2777  * set the separator to key2.
2778  */
2779 #define MAKE_SEPARATOR(key1, key2, dest, field) \
2780         dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
2781
2782 static void
2783 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
2784                       hammer_base_elm_t dest)
2785 {
2786         bzero(dest, sizeof(*dest));
2787
2788         dest->rec_type = key2->rec_type;
2789         dest->key = key2->key;
2790         dest->obj_id = key2->obj_id;
2791         dest->create_tid = key2->create_tid;
2792
2793         MAKE_SEPARATOR(key1, key2, dest, localization);
2794         if (key1->localization == key2->localization) {
2795                 MAKE_SEPARATOR(key1, key2, dest, obj_id);
2796                 if (key1->obj_id == key2->obj_id) {
2797                         MAKE_SEPARATOR(key1, key2, dest, rec_type);
2798                         if (key1->rec_type == key2->rec_type) {
2799                                 MAKE_SEPARATOR(key1, key2, dest, key);
2800                                 /*
2801                                  * Don't bother creating a separator for
2802                                  * create_tid, which also conveniently avoids
2803                                  * having to handle the create_tid == 0
2804                                  * (infinity) case.  Just leave create_tid
2805                                  * set to key2.
2806                                  *
2807                                  * Worst case, dest matches key2 exactly,
2808                                  * which is acceptable.
2809                                  */
2810                         }
2811                 }
2812         }
2813 }
2814
2815 #undef MAKE_SEPARATOR
2816
2817 /*
2818  * Return whether a generic internal or leaf node is full
2819  */
2820 static int
2821 btree_node_is_full(hammer_node_ondisk_t node)
2822 {
2823         switch(node->type) {
2824         case HAMMER_BTREE_TYPE_INTERNAL:
2825                 if (node->count == HAMMER_BTREE_INT_ELMS)
2826                         return(1);
2827                 break;
2828         case HAMMER_BTREE_TYPE_LEAF:
2829                 if (node->count == HAMMER_BTREE_LEAF_ELMS)
2830                         return(1);
2831                 break;
2832         default:
2833                 panic("illegal btree subtype");
2834         }
2835         return(0);
2836 }
2837
2838 #if 0
2839 static int
2840 btree_max_elements(u_int8_t type)
2841 {
2842         if (type == HAMMER_BTREE_TYPE_LEAF)
2843                 return(HAMMER_BTREE_LEAF_ELMS);
2844         if (type == HAMMER_BTREE_TYPE_INTERNAL)
2845                 return(HAMMER_BTREE_INT_ELMS);
2846         panic("btree_max_elements: bad type %d\n", type);
2847 }
2848 #endif
2849
2850 void
2851 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
2852 {
2853         hammer_btree_elm_t elm;
2854         int i;
2855
2856         kprintf("node %p count=%d parent=%016llx type=%c\n",
2857                 ondisk, ondisk->count,
2858                 (long long)ondisk->parent, ondisk->type);
2859
2860         /*
2861          * Dump both boundary elements if an internal node
2862          */
2863         if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2864                 for (i = 0; i <= ondisk->count; ++i) {
2865                         elm = &ondisk->elms[i];
2866                         hammer_print_btree_elm(elm, ondisk->type, i);
2867                 }
2868         } else {
2869                 for (i = 0; i < ondisk->count; ++i) {
2870                         elm = &ondisk->elms[i];
2871                         hammer_print_btree_elm(elm, ondisk->type, i);
2872                 }
2873         }
2874 }
2875
2876 void
2877 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
2878 {
2879         kprintf("  %2d", i);
2880         kprintf("\tobj_id       = %016llx\n", (long long)elm->base.obj_id);
2881         kprintf("\tkey          = %016llx\n", (long long)elm->base.key);
2882         kprintf("\tcreate_tid   = %016llx\n", (long long)elm->base.create_tid);
2883         kprintf("\tdelete_tid   = %016llx\n", (long long)elm->base.delete_tid);
2884         kprintf("\trec_type     = %04x\n", elm->base.rec_type);
2885         kprintf("\tobj_type     = %02x\n", elm->base.obj_type);
2886         kprintf("\tbtype        = %02x (%c)\n",
2887                 elm->base.btype,
2888                 (elm->base.btype ? elm->base.btype : '?'));
2889         kprintf("\tlocalization = %02x\n", elm->base.localization);
2890
2891         switch(type) {
2892         case HAMMER_BTREE_TYPE_INTERNAL:
2893                 kprintf("\tsubtree_off  = %016llx\n",
2894                         (long long)elm->internal.subtree_offset);
2895                 break;
2896         case HAMMER_BTREE_TYPE_RECORD:
2897                 kprintf("\tdata_offset  = %016llx\n",
2898                         (long long)elm->leaf.data_offset);
2899                 kprintf("\tdata_len     = %08x\n", elm->leaf.data_len);
2900                 kprintf("\tdata_crc     = %08x\n", elm->leaf.data_crc);
2901                 break;
2902         }
2903 }