sys/vfs/hammer/hammer_cursor.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_cursor.c,v 1.42 2008/08/06 15:38:58 dillon Exp $
  35  */
  36
  37 /*
  38  * HAMMER B-Tree index - cursor support routines
  39  */
  40 #include "hammer.h"
  41
  42 static int hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive);
  43
  44 /*
  45  * Initialize a fresh cursor using the B-Tree node cache.  If the cache
  46  * is not available initialize a fresh cursor at the root of the filesystem.
  47  */
  48 int
  49 hammer_init_cursor(hammer_transaction_t trans, hammer_cursor_t cursor,
  50                    hammer_node_cache_t cache, hammer_inode_t ip)
  51 {
  52         hammer_volume_t volume;
  53         hammer_node_t node;
  54         int error;
  55
  56         bzero(cursor, sizeof(*cursor));
  57
  58         cursor->trans = trans;
  59
  60         /*
  61          * If the cursor operation is on behalf of an inode, lock
  62          * the inode.
  63          */
  64         if ((cursor->ip = ip) != NULL) {
  65                 ++ip->cursor_ip_refs;
  66                 if (trans->type == HAMMER_TRANS_FLS)
  67                         hammer_lock_ex(&ip->lock);
  68                 else
  69                         hammer_lock_sh(&ip->lock);
  70         }
  71
  72         /*
  73          * Step 1 - acquire a locked node from the cache if possible
  74          */
  75         if (cache && cache->node) {
  76                 node = hammer_ref_node_safe(trans, cache, &error);
  77                 if (error == 0) {
  78                         hammer_lock_sh(&node->lock);
  79                         if (node->flags & HAMMER_NODE_DELETED) {
  80                                 hammer_unlock(&node->lock);
  81                                 hammer_rel_node(node);
  82                                 node = NULL;
  83                         }
  84                 }
  85                 if (node == NULL)
  86                         ++hammer_stats_btree_root_iterations;
  87         } else {
  88                 node = NULL;
  89                 ++hammer_stats_btree_root_iterations;
  90         }
  91
  92         /*
  93          * Step 2 - If we couldn't get a node from the cache, get
  94          * the one from the root of the filesystem.
  95          */
  96         while (node == NULL) {
  97                 volume = hammer_get_root_volume(trans->hmp, &error);
  98                 if (error)
  99                         break;
 100                 node = hammer_get_node(trans, volume->ondisk->vol0_btree_root,
 101                                        0, &error);
 102                 hammer_rel_volume(volume, 0);
 103                 if (error)
 104                         break;
 105                 hammer_lock_sh(&node->lock);
 106
 107                 /*
 108                  * If someone got in before we could lock the node, retry.
 109                  */
 110                 if (node->flags & HAMMER_NODE_DELETED) {
 111                         hammer_unlock(&node->lock);
 112                         hammer_rel_node(node);
 113                         node = NULL;
 114                         continue;
 115                 }
 116                 if (volume->ondisk->vol0_btree_root != node->node_offset) {
 117                         hammer_unlock(&node->lock);
 118                         hammer_rel_node(node);
 119                         node = NULL;
 120                         continue;
 121                 }
 122         }
 123
 124         /*
 125          * Step 3 - finish initializing the cursor by acquiring the parent
 126          */
 127         cursor->node = node;
 128         if (error == 0)
 129                 error = hammer_load_cursor_parent(cursor, 0);
 130         KKASSERT(error == 0);
 131         /* if (error) hammer_done_cursor(cursor); */
 132         return(error);
 133 }
 134
 135 /*
 136  * Normalize a cursor.  Sometimes cursors can be left in a state
 137  * where node is NULL.  If the cursor is in this state, cursor up.
 138  */
 139 void
 140 hammer_normalize_cursor(hammer_cursor_t cursor)
 141 {
 142         if (cursor->node == NULL) {
 143                 KKASSERT(cursor->parent != NULL);
 144                 hammer_cursor_up(cursor);
 145         }
 146 }
 147
 148
 149 /*
 150  * We are finished with a cursor.  We NULL out various fields as sanity
 151  * check, in case the structure is inappropriately used afterwords.
 152  */
 153 void
 154 hammer_done_cursor(hammer_cursor_t cursor)
 155 {
 156         hammer_inode_t ip;
 157
 158         KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
 159         if (cursor->parent) {
 160                 hammer_unlock(&cursor->parent->lock);
 161                 hammer_rel_node(cursor->parent);
 162                 cursor->parent = NULL;
 163         }
 164         if (cursor->node) {
 165                 hammer_unlock(&cursor->node->lock);
 166                 hammer_rel_node(cursor->node);
 167                 cursor->node = NULL;
 168         }
 169         if (cursor->data_buffer) {
 170                 hammer_rel_buffer(cursor->data_buffer, 0);
 171                 cursor->data_buffer = NULL;
 172         }
 173         if ((ip = cursor->ip) != NULL) {
 174                 KKASSERT(ip->cursor_ip_refs > 0);
 175                 --ip->cursor_ip_refs;
 176                 hammer_unlock(&ip->lock);
 177                 cursor->ip = NULL;
 178         }
 179         if (cursor->iprec) {
 180                 hammer_rel_mem_record(cursor->iprec);
 181                 cursor->iprec = NULL;
 182         }
 183
 184         /*
 185          * If we deadlocked this node will be referenced.  Do a quick
 186          * lock/unlock to wait for the deadlock condition to clear.
 187          */
 188         if (cursor->deadlk_node) {
 189                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 190                 hammer_unlock(&cursor->deadlk_node->lock);
 191                 hammer_rel_node(cursor->deadlk_node);
 192                 cursor->deadlk_node = NULL;
 193         }
 194         if (cursor->deadlk_rec) {
 195                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 196                 hammer_rel_mem_record(cursor->deadlk_rec);
 197                 cursor->deadlk_rec = NULL;
 198         }
 199
 200         cursor->data = NULL;
 201         cursor->leaf = NULL;
 202         cursor->left_bound = NULL;
 203         cursor->right_bound = NULL;
 204         cursor->trans = NULL;
 205 }
 206
 207 /*
 208  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 209  * function can return EDEADLK.
 210  *
 211  * The lock must already be either held shared or already held exclusively
 212  * by us.
 213  *
 214  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 215  * we add another reference to the node that failed and set
 216  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 217  */
 218 int
 219 hammer_cursor_upgrade(hammer_cursor_t cursor)
 220 {
 221         int error;
 222
 223         error = hammer_lock_upgrade(&cursor->node->lock);
 224         if (error && cursor->deadlk_node == NULL) {
 225                 cursor->deadlk_node = cursor->node;
 226                 hammer_ref_node(cursor->deadlk_node);
 227         } else if (error == 0 && cursor->parent) {
 228                 error = hammer_lock_upgrade(&cursor->parent->lock);
 229                 if (error && cursor->deadlk_node == NULL) {
 230                         cursor->deadlk_node = cursor->parent;
 231                         hammer_ref_node(cursor->deadlk_node);
 232                 }
 233         }
 234         return(error);
 235 }
 236
 237 int
 238 hammer_cursor_upgrade_node(hammer_cursor_t cursor)
 239 {
 240         int error;
 241
 242         error = hammer_lock_upgrade(&cursor->node->lock);
 243         if (error && cursor->deadlk_node == NULL) {
 244                 cursor->deadlk_node = cursor->node;
 245                 hammer_ref_node(cursor->deadlk_node);
 246         }
 247         return(error);
 248 }
 249
 250 /*
 251  * Downgrade cursor->node and cursor->parent to shared locks.  This
 252  * function can return EDEADLK.
 253  */
 254 void
 255 hammer_cursor_downgrade(hammer_cursor_t cursor)
 256 {
 257         if (hammer_lock_excl_owned(&cursor->node->lock, curthread))
 258                 hammer_lock_downgrade(&cursor->node->lock);
 259         if (cursor->parent &&
 260             hammer_lock_excl_owned(&cursor->parent->lock, curthread)) {
 261                 hammer_lock_downgrade(&cursor->parent->lock);
 262         }
 263 }
 264
 265 /*
 266  * Seek the cursor to the specified node and index.
 267  *
 268  * The caller must ref the node prior to calling this routine and release
 269  * it after it returns.  If the seek succeeds the cursor will gain its own
 270  * ref on the node.
 271  */
 272 int
 273 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 274 {
 275         int error;
 276
 277         hammer_cursor_downgrade(cursor);
 278         error = 0;
 279
 280         if (cursor->node != node) {
 281                 hammer_unlock(&cursor->node->lock);
 282                 hammer_rel_node(cursor->node);
 283                 cursor->node = node;
 284                 hammer_ref_node(node);
 285                 hammer_lock_sh(&node->lock);
 286                 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
 287
 288                 if (cursor->parent) {
 289                         hammer_unlock(&cursor->parent->lock);
 290                         hammer_rel_node(cursor->parent);
 291                         cursor->parent = NULL;
 292                         cursor->parent_index = 0;
 293                 }
 294                 error = hammer_load_cursor_parent(cursor, 0);
 295         }
 296         cursor->index = index;
 297         return (error);
 298 }
 299
 300 /*
 301  * Load the parent of cursor->node into cursor->parent.
 302  */
 303 static
 304 int
 305 hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive)
 306 {
 307         hammer_mount_t hmp;
 308         hammer_node_t parent;
 309         hammer_node_t node;
 310         hammer_btree_elm_t elm;
 311         int error;
 312         int parent_index;
 313
 314         hmp = cursor->trans->hmp;
 315
 316         if (cursor->node->ondisk->parent) {
 317                 node = cursor->node;
 318                 parent = hammer_btree_get_parent(cursor->trans, node,
 319                                                  &parent_index,
 320                                                  &error, try_exclusive);
 321                 if (error == 0) {
 322                         elm = &parent->ondisk->elms[parent_index];
 323                         cursor->parent = parent;
 324                         cursor->parent_index = parent_index;
 325                         cursor->left_bound = &elm[0].internal.base;
 326                         cursor->right_bound = &elm[1].internal.base;
 327                 }
 328         } else {
 329                 cursor->parent = NULL;
 330                 cursor->parent_index = 0;
 331                 cursor->left_bound = &hmp->root_btree_beg;
 332                 cursor->right_bound = &hmp->root_btree_end;
 333                 error = 0;
 334         }
 335         return(error);
 336 }
 337
 338 /*
 339  * Cursor up to our parent node.  Return ENOENT if we are at the root of
 340  * the filesystem.
 341  */
 342 int
 343 hammer_cursor_up(hammer_cursor_t cursor)
 344 {
 345         int error;
 346
 347         hammer_cursor_downgrade(cursor);
 348
 349         /*
 350          * If the parent is NULL we are at the root of the B-Tree and
 351          * return ENOENT.
 352          */
 353         if (cursor->parent == NULL)
 354                 return (ENOENT);
 355
 356         /*
 357          * Set the node to its parent.
 358          */
 359         hammer_unlock(&cursor->node->lock);
 360         hammer_rel_node(cursor->node);
 361         cursor->node = cursor->parent;
 362         cursor->index = cursor->parent_index;
 363         cursor->parent = NULL;
 364         cursor->parent_index = 0;
 365
 366         error = hammer_load_cursor_parent(cursor, 0);
 367         return(error);
 368 }
 369
 370 /*
 371  * Special cursor up given a locked cursor.  The orignal node is not
 372  * unlocked or released and the cursor is not downgraded.
 373  *
 374  * This function will recover from deadlocks.  EDEADLK cannot be returned.
 375  */
 376 int
 377 hammer_cursor_up_locked(hammer_cursor_t cursor)
 378 {
 379         hammer_node_t save;
 380         int error;
 381
 382         /*
 383          * If the parent is NULL we are at the root of the B-Tree and
 384          * return ENOENT.
 385          */
 386         if (cursor->parent == NULL)
 387                 return (ENOENT);
 388
 389         save = cursor->node;
 390
 391         /*
 392          * Set the node to its parent.
 393          */
 394         cursor->node = cursor->parent;
 395         cursor->index = cursor->parent_index;
 396         cursor->parent = NULL;
 397         cursor->parent_index = 0;
 398
 399         /*
 400          * load the new parent, attempt to exclusively lock it.  Note that
 401          * we are still holding the old parent (now cursor->node) exclusively
 402          * locked.  This can return EDEADLK.
 403          */
 404         error = hammer_load_cursor_parent(cursor, 1);
 405         if (error) {
 406                 cursor->parent = cursor->node;
 407                 cursor->parent_index = cursor->index;
 408                 cursor->node = save;
 409                 cursor->index = 0;
 410         }
 411         return(error);
 412 }
 413
 414
 415 /*
 416  * Cursor down through the current node, which must be an internal node.
 417  *
 418  * This routine adjusts the cursor and sets index to 0.
 419  */
 420 int
 421 hammer_cursor_down(hammer_cursor_t cursor)
 422 {
 423         hammer_node_t node;
 424         hammer_btree_elm_t elm;
 425         int error;
 426
 427         /*
 428          * The current node becomes the current parent
 429          */
 430         hammer_cursor_downgrade(cursor);
 431         node = cursor->node;
 432         KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
 433         if (cursor->parent) {
 434                 hammer_unlock(&cursor->parent->lock);
 435                 hammer_rel_node(cursor->parent);
 436         }
 437         cursor->parent = node;
 438         cursor->parent_index = cursor->index;
 439         cursor->node = NULL;
 440         cursor->index = 0;
 441
 442         /*
 443          * Extract element to push into at (node,index), set bounds.
 444          */
 445         elm = &node->ondisk->elms[cursor->parent_index];
 446
 447         /*
 448          * Ok, push down into elm.  If elm specifies an internal or leaf
 449          * node the current node must be an internal node.  If elm specifies
 450          * a spike then the current node must be a leaf node.
 451          */
 452         switch(elm->base.btype) {
 453         case HAMMER_BTREE_TYPE_INTERNAL:
 454         case HAMMER_BTREE_TYPE_LEAF:
 455                 KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
 456                 KKASSERT(elm->internal.subtree_offset != 0);
 457                 cursor->left_bound = &elm[0].internal.base;
 458                 cursor->right_bound = &elm[1].internal.base;
 459                 node = hammer_get_node(cursor->trans,
 460                                        elm->internal.subtree_offset, 0, &error);
 461                 if (error == 0) {
 462                         KASSERT(elm->base.btype == node->ondisk->type, ("BTYPE MISMATCH %c %c NODE %p\n", elm->base.btype, node->ondisk->type, node));
 463                         if (node->ondisk->parent != cursor->parent->node_offset)
 464                                 panic("node %p %016llx vs %016llx\n", node, (long long)node->ondisk->parent, (long long)cursor->parent->node_offset);
 465                         KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
 466                 }
 467                 break;
 468         default:
 469                 panic("hammer_cursor_down: illegal btype %02x (%c)\n",
 470                       elm->base.btype,
 471                       (elm->base.btype ? elm->base.btype : '?'));
 472                 break;
 473         }
 474         if (error == 0) {
 475                 hammer_lock_sh(&node->lock);
 476                 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
 477                 cursor->node = node;
 478                 cursor->index = 0;
 479         }
 480         return(error);
 481 }
 482
 483 /************************************************************************
 484  *                              DEADLOCK RECOVERY                       *
 485  ************************************************************************
 486  *
 487  * These are the new deadlock recovery functions.  Currently they are only
 488  * used for the mirror propagation and physical node removal cases but
 489  * ultimately the intention is to use them for all deadlock recovery
 490  * operations.
 491  */
 492 void
 493 hammer_unlock_cursor(hammer_cursor_t cursor)
 494 {
 495         hammer_node_t node;
 496
 497         KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
 498         KKASSERT(cursor->node);
 499
 500         /*
 501          * Release the cursor's locks and track B-Tree operations on node.
 502          * While being tracked our cursor can be modified by other threads
 503          * and the node may be replaced.
 504          */
 505         if (cursor->parent) {
 506                 hammer_unlock(&cursor->parent->lock);
 507                 hammer_rel_node(cursor->parent);
 508                 cursor->parent = NULL;
 509         }
 510         node = cursor->node;
 511         cursor->flags |= HAMMER_CURSOR_TRACKED;
 512         TAILQ_INSERT_TAIL(&node->cursor_list, cursor, deadlk_entry);
 513         hammer_unlock(&node->lock);
 514 }
 515
 516 /*
 517  * Get the cursor heated up again.  The cursor's node may have
 518  * changed and we might have to locate the new parent.
 519  *
 520  * If the exact element we were on got deleted RIPOUT will be
 521  * set and we must clear ATEDISK so an iteration does not skip
 522  * the element after it.
 523  */
 524 int
 525 hammer_lock_cursor(hammer_cursor_t cursor)
 526 {
 527         hammer_node_t node;
 528         int error;
 529
 530         KKASSERT(cursor->flags & HAMMER_CURSOR_TRACKED);
 531
 532         /*
 533          * Relock the node
 534          */
 535         for (;;) {
 536                 node = cursor->node;
 537                 hammer_ref_node(node);
 538                 hammer_lock_sh(&node->lock);
 539                 if (cursor->node == node) {
 540                         hammer_rel_node(node);
 541                         break;
 542                 }
 543                 hammer_unlock(&node->lock);
 544                 hammer_rel_node(node);
 545         }
 546
 547         /*
 548          * Untrack the cursor, clean up, and re-establish the parent node.
 549          */
 550         TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 551         cursor->flags &= ~HAMMER_CURSOR_TRACKED;
 552
 553         /*
 554          * If a ripout has occured iterations must re-test the (new)
 555          * current element.  Clearing ATEDISK prevents the element from
 556          * being skipped and RETEST causes it to be re-tested.
 557          */
 558         if (cursor->flags & HAMMER_CURSOR_TRACKED_RIPOUT) {
 559                 cursor->flags &= ~HAMMER_CURSOR_TRACKED_RIPOUT;
 560                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 561                 cursor->flags |= HAMMER_CURSOR_RETEST;
 562         }
 563         error = hammer_load_cursor_parent(cursor, 0);
 564         return(error);
 565 }
 566
 567 /*
 568  * Recover from a deadlocked cursor, tracking any node removals or
 569  * replacements.  If the cursor's current node is removed by another
 570  * thread (via btree_remove()) the cursor will be seeked upwards.
 571  *
 572  * The caller is working a modifying operation and must be holding the
 573  * sync lock (shared).  We do not release the sync lock because this
 574  * would break atomicy.
 575  */
 576 int
 577 hammer_recover_cursor(hammer_cursor_t cursor)
 578 {
 579         int error;
 580
 581         hammer_unlock_cursor(cursor);
 582         KKASSERT(cursor->trans->sync_lock_refs > 0);
 583
 584         /*
 585          * Wait for the deadlock to clear
 586          */
 587         if (cursor->deadlk_node) {
 588                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 589                 hammer_unlock(&cursor->deadlk_node->lock);
 590                 hammer_rel_node(cursor->deadlk_node);
 591                 cursor->deadlk_node = NULL;
 592         }
 593         if (cursor->deadlk_rec) {
 594                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 595                 hammer_rel_mem_record(cursor->deadlk_rec);
 596                 cursor->deadlk_rec = NULL;
 597         }
 598         error = hammer_lock_cursor(cursor);
 599         return(error);
 600 }
 601
 602 /*
 603  * Dup ocursor to ncursor.  ncursor inherits ocursor's locks and ocursor
 604  * is effectively unlocked and becomes tracked.  If ocursor was not locked
 605  * then ncursor also inherits the tracking.
 606  *
 607  * After the caller finishes working with ncursor it must be cleaned up
 608  * with hammer_done_cursor(), and the caller must re-lock ocursor.
 609  */
 610 hammer_cursor_t
 611 hammer_push_cursor(hammer_cursor_t ocursor)
 612 {
 613         hammer_cursor_t ncursor;
 614         hammer_inode_t ip;
 615         hammer_node_t node;
 616         hammer_mount_t hmp;
 617
 618         hmp = ocursor->trans->hmp;
 619         ncursor = kmalloc(sizeof(*ncursor), hmp->m_misc, M_WAITOK | M_ZERO);
 620         bcopy(ocursor, ncursor, sizeof(*ocursor));
 621
 622         node = ocursor->node;
 623         hammer_ref_node(node);
 624         if ((ocursor->flags & HAMMER_CURSOR_TRACKED) == 0) {
 625                 ocursor->flags |= HAMMER_CURSOR_TRACKED;
 626                 TAILQ_INSERT_TAIL(&node->cursor_list, ocursor, deadlk_entry);
 627         }
 628         if (ncursor->parent)
 629                 ocursor->parent = NULL;
 630         ocursor->data_buffer = NULL;
 631         ocursor->leaf = NULL;
 632         ocursor->data = NULL;
 633         if (ncursor->flags & HAMMER_CURSOR_TRACKED)
 634                 TAILQ_INSERT_TAIL(&node->cursor_list, ncursor, deadlk_entry);
 635         if ((ip = ncursor->ip) != NULL) {
 636                 ++ip->cursor_ip_refs;
 637         }
 638         if (ncursor->iprec)
 639                 hammer_ref(&ncursor->iprec->lock);
 640         return(ncursor);
 641 }
 642
 643 /*
 644  * Destroy ncursor and restore ocursor
 645  *
 646  * This is a temporary hack for the release.  We can't afford to lose
 647  * the IP lock until the IP object scan code is able to deal with it,
 648  * so have ocursor inherit it back.
 649  */
 650 void
 651 hammer_pop_cursor(hammer_cursor_t ocursor, hammer_cursor_t ncursor)
 652 {
 653         hammer_mount_t hmp;
 654         hammer_inode_t ip;
 655
 656         hmp = ncursor->trans->hmp;
 657         ip = ncursor->ip;
 658         ncursor->ip = NULL;
 659         if (ip)
 660                 --ip->cursor_ip_refs;
 661         hammer_done_cursor(ncursor);
 662         kfree(ncursor, hmp->m_misc);
 663         KKASSERT(ocursor->ip == ip);
 664         hammer_lock_cursor(ocursor);
 665 }
 666
 667 /*
 668  * onode is being replaced by nnode by the reblocking code.
 669  */
 670 void
 671 hammer_cursor_replaced_node(hammer_node_t onode, hammer_node_t nnode)
 672 {
 673         hammer_cursor_t cursor;
 674
 675         while ((cursor = TAILQ_FIRST(&onode->cursor_list)) != NULL) {
 676                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 677                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 678                 KKASSERT(cursor->node == onode);
 679                 cursor->node = nnode;
 680                 hammer_ref_node(nnode);
 681                 hammer_rel_node(onode);
 682         }
 683 }
 684
 685 /*
 686  * node is being removed, cursors in deadlock recovery are seeked upward
 687  * to the parent.
 688  */
 689 void
 690 hammer_cursor_removed_node(hammer_node_t node, hammer_node_t parent, int index)
 691 {
 692         hammer_cursor_t cursor;
 693
 694         KKASSERT(parent != NULL);
 695         while ((cursor = TAILQ_FIRST(&node->cursor_list)) != NULL) {
 696                 KKASSERT(cursor->node == node);
 697                 KKASSERT(cursor->index == 0);
 698                 TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 699                 TAILQ_INSERT_TAIL(&parent->cursor_list, cursor, deadlk_entry);
 700                 cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
 701                 cursor->node = parent;
 702                 cursor->index = index;
 703                 hammer_ref_node(parent);
 704                 hammer_rel_node(node);
 705         }
 706 }
 707
 708 /*
 709  * node was split at (onode, index) with elements >= index moved to nnode.
 710  */
 711 void
 712 hammer_cursor_split_node(hammer_node_t onode, hammer_node_t nnode, int index)
 713 {
 714         hammer_cursor_t cursor;
 715
 716 again:
 717         TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
 718                 KKASSERT(cursor->node == onode);
 719                 if (cursor->index < index)
 720                         continue;
 721                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 722                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 723                 cursor->node = nnode;
 724                 cursor->index -= index;
 725                 hammer_ref_node(nnode);
 726                 hammer_rel_node(onode);
 727                 goto again;
 728         }
 729 }
 730
 731 /*
 732  * An element was moved from one node to another or within a node.  The
 733  * index may also represent the end of the node (index == numelements).
 734  *
 735  * This is used by the rebalancing code.  This is not an insertion or
 736  * deletion and any additional elements, including the degenerate case at
 737  * the end of the node, will be dealt with by additional distinct calls.
 738  */
 739 void
 740 hammer_cursor_moved_element(hammer_node_t onode, hammer_node_t nnode,
 741                             int oindex, int nindex)
 742 {
 743         hammer_cursor_t cursor;
 744
 745 again:
 746         TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
 747                 KKASSERT(cursor->node == onode);
 748                 if (cursor->index != oindex)
 749                         continue;
 750                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 751                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 752                 cursor->node = nnode;
 753                 cursor->index = nindex;
 754                 hammer_ref_node(nnode);
 755                 hammer_rel_node(onode);
 756                 goto again;
 757         }
 758 }
 759
 760 /*
 761  * The B-Tree element pointing to the specified node was moved from (oparent)
 762  * to (nparent, nindex).  We must locate any tracked cursors pointing at
 763  * node and adjust their parent accordingly.
 764  *
 765  * This is used by the rebalancing code when packing elements causes an
 766  * element to shift from one node to another.
 767  */
 768 void
 769 hammer_cursor_parent_changed(hammer_node_t node, hammer_node_t oparent,
 770                              hammer_node_t nparent, int nindex)
 771 {
 772         hammer_cursor_t cursor;
 773
 774 again:
 775         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 776                 KKASSERT(cursor->node == node);
 777                 if (cursor->parent == oparent) {
 778                         cursor->parent = nparent;
 779                         cursor->parent_index = nindex;
 780                         hammer_ref_node(nparent);
 781                         hammer_rel_node(oparent);
 782                         goto again;
 783                 }
 784         }
 785 }
 786
 787 /*
 788  * Deleted element at (node, index)
 789  *
 790  * Shift indexes >= index
 791  */
 792 void
 793 hammer_cursor_deleted_element(hammer_node_t node, int index)
 794 {
 795         hammer_cursor_t cursor;
 796
 797         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 798                 KKASSERT(cursor->node == node);
 799                 if (cursor->index == index) {
 800                         cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
 801                 } else if (cursor->index > index) {
 802                         --cursor->index;
 803                 }
 804         }
 805 }
 806
 807 /*
 808  * Inserted element at (node, index)
 809  *
 810  * Shift indexes >= index
 811  */
 812 void
 813 hammer_cursor_inserted_element(hammer_node_t node, int index)
 814 {
 815         hammer_cursor_t cursor;
 816
 817         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 818                 KKASSERT(cursor->node == node);
 819                 if (cursor->index >= index)
 820                         ++cursor->index;
 821         }
 822 }
 823