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