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 1.41 2008/07/11 01:22:29 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->hmp,
  98                                        volume->ondisk->vol0_btree_root,
  99                                        0, &error);
 100                 hammer_rel_volume(volume, 0);
 101                 if (error)
 102                         break;
 103                 hammer_lock_sh(&node->lock);
 104
 105                 /*
 106                  * If someone got in before we could lock the node, retry.
 107                  */
 108                 if (node->flags & HAMMER_NODE_DELETED) {
 109                         hammer_unlock(&node->lock);
 110                         hammer_rel_node(node);
 111                         node = NULL;
 112                         continue;
 113                 }
 114                 if (volume->ondisk->vol0_btree_root != node->node_offset) {
 115                         hammer_unlock(&node->lock);
 116                         hammer_rel_node(node);
 117                         node = NULL;
 118                         continue;
 119                 }
 120         }
 121
 122         /*
 123          * Step 3 - finish initializing the cursor by acquiring the parent
 124          */
 125         cursor->node = node;
 126         if (error == 0)
 127                 error = hammer_load_cursor_parent(cursor, 0);
 128         KKASSERT(error == 0);
 129         /* if (error) hammer_done_cursor(cursor); */
 130         return(error);
 131 }
 132
 133 /*
 134  * Normalize a cursor.  Sometimes cursors can be left in a state
 135  * where node is NULL.  If the cursor is in this state, cursor up.
 136  */
 137 void
 138 hammer_normalize_cursor(hammer_cursor_t cursor)
 139 {
 140         if (cursor->node == NULL) {
 141                 KKASSERT(cursor->parent != NULL);
 142                 hammer_cursor_up(cursor);
 143         }
 144 }
 145
 146
 147 /*
 148  * We are finished with a cursor.  We NULL out various fields as sanity
 149  * check, in case the structure is inappropriately used afterwords.
 150  */
 151 void
 152 hammer_done_cursor(hammer_cursor_t cursor)
 153 {
 154         hammer_inode_t ip;
 155
 156         KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
 157         if (cursor->parent) {
 158                 hammer_unlock(&cursor->parent->lock);
 159                 hammer_rel_node(cursor->parent);
 160                 cursor->parent = NULL;
 161         }
 162         if (cursor->node) {
 163                 hammer_unlock(&cursor->node->lock);
 164                 hammer_rel_node(cursor->node);
 165                 cursor->node = NULL;
 166         }
 167         if (cursor->data_buffer) {
 168                 hammer_rel_buffer(cursor->data_buffer, 0);
 169                 cursor->data_buffer = NULL;
 170         }
 171         if ((ip = cursor->ip) != NULL) {
 172                 KKASSERT(ip->cursor_ip_refs > 0);
 173                 --ip->cursor_ip_refs;
 174                 hammer_unlock(&ip->lock);
 175                 cursor->ip = NULL;
 176         }
 177         if (cursor->iprec) {
 178                 hammer_rel_mem_record(cursor->iprec);
 179                 cursor->iprec = NULL;
 180         }
 181
 182         /*
 183          * If we deadlocked this node will be referenced.  Do a quick
 184          * lock/unlock to wait for the deadlock condition to clear.
 185          */
 186         if (cursor->deadlk_node) {
 187                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 188                 hammer_unlock(&cursor->deadlk_node->lock);
 189                 hammer_rel_node(cursor->deadlk_node);
 190                 cursor->deadlk_node = NULL;
 191         }
 192         if (cursor->deadlk_rec) {
 193                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 194                 hammer_rel_mem_record(cursor->deadlk_rec);
 195                 cursor->deadlk_rec = NULL;
 196         }
 197
 198         cursor->data = NULL;
 199         cursor->leaf = NULL;
 200         cursor->left_bound = NULL;
 201         cursor->right_bound = NULL;
 202         cursor->trans = NULL;
 203 }
 204
 205 /*
 206  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 207  * function can return EDEADLK.
 208  *
 209  * The lock must already be either held shared or already held exclusively
 210  * by us.
 211  *
 212  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 213  * we add another reference to the node that failed and set
 214  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 215  */
 216 int
 217 hammer_cursor_upgrade(hammer_cursor_t cursor)
 218 {
 219         int error;
 220
 221         error = hammer_lock_upgrade(&cursor->node->lock);
 222         if (error && cursor->deadlk_node == NULL) {
 223                 cursor->deadlk_node = cursor->node;
 224                 hammer_ref_node(cursor->deadlk_node);
 225         } else if (error == 0 && cursor->parent) {
 226                 error = hammer_lock_upgrade(&cursor->parent->lock);
 227                 if (error && cursor->deadlk_node == NULL) {
 228                         cursor->deadlk_node = cursor->parent;
 229                         hammer_ref_node(cursor->deadlk_node);
 230                 }
 231         }
 232         return(error);
 233 }
 234
 235 int
 236 hammer_cursor_upgrade_node(hammer_cursor_t cursor)
 237 {
 238         int error;
 239
 240         error = hammer_lock_upgrade(&cursor->node->lock);
 241         if (error && cursor->deadlk_node == NULL) {
 242                 cursor->deadlk_node = cursor->node;
 243                 hammer_ref_node(cursor->deadlk_node);
 244         }
 245         return(error);
 246 }
 247
 248 /*
 249  * Downgrade cursor->node and cursor->parent to shared locks.  This
 250  * function can return EDEADLK.
 251  */
 252 void
 253 hammer_cursor_downgrade(hammer_cursor_t cursor)
 254 {
 255         if (hammer_lock_excl_owned(&cursor->node->lock, curthread))
 256                 hammer_lock_downgrade(&cursor->node->lock);
 257         if (cursor->parent &&
 258             hammer_lock_excl_owned(&cursor->parent->lock, curthread)) {
 259                 hammer_lock_downgrade(&cursor->parent->lock);
 260         }
 261 }
 262
 263 /*
 264  * Seek the cursor to the specified node and index.
 265  *
 266  * The caller must ref the node prior to calling this routine and release
 267  * it after it returns.  If the seek succeeds the cursor will gain its own
 268  * ref on the node.
 269  */
 270 int
 271 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 272 {
 273         int error;
 274
 275         hammer_cursor_downgrade(cursor);
 276         error = 0;
 277
 278         if (cursor->node != node) {
 279                 hammer_unlock(&cursor->node->lock);
 280                 hammer_rel_node(cursor->node);
 281                 cursor->node = node;
 282                 hammer_ref_node(node);
 283                 hammer_lock_sh(&node->lock);
 284                 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
 285
 286                 if (cursor->parent) {
 287                         hammer_unlock(&cursor->parent->lock);
 288                         hammer_rel_node(cursor->parent);
 289                         cursor->parent = NULL;
 290                         cursor->parent_index = 0;
 291                 }
 292                 error = hammer_load_cursor_parent(cursor, 0);
 293         }
 294         cursor->index = index;
 295         return (error);
 296 }
 297
 298 /*
 299  * Load the parent of cursor->node into cursor->parent.
 300  */
 301 static
 302 int
 303 hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive)
 304 {
 305         hammer_mount_t hmp;
 306         hammer_node_t parent;
 307         hammer_node_t node;
 308         hammer_btree_elm_t elm;
 309         int error;
 310         int parent_index;
 311
 312         hmp = cursor->trans->hmp;
 313
 314         if (cursor->node->ondisk->parent) {
 315                 node = cursor->node;
 316                 parent = hammer_btree_get_parent(node, &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->hmp,
 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, int also_ip)
 491 {
 492         hammer_node_t node;
 493         hammer_inode_t ip;
 494
 495         KKASSERT((cursor->flags & HAMMER_CURSOR_TRACKED) == 0);
 496         KKASSERT(cursor->node);
 497         /*
 498          * Release the cursor's locks and track B-Tree operations on node.
 499          * While being tracked our cursor can be modified by other threads
 500          * and node may be replaced.
 501          */
 502         if (cursor->parent) {
 503                 hammer_unlock(&cursor->parent->lock);
 504                 hammer_rel_node(cursor->parent);
 505                 cursor->parent = NULL;
 506         }
 507         node = cursor->node;
 508         cursor->flags |= HAMMER_CURSOR_TRACKED;
 509         TAILQ_INSERT_TAIL(&node->cursor_list, cursor, deadlk_entry);
 510         hammer_unlock(&node->lock);
 511
 512         if (also_ip && (ip = cursor->ip) != NULL)
 513                 hammer_unlock(&ip->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, int also_ip)
 526 {
 527         hammer_inode_t ip;
 528         hammer_node_t node;
 529         int error;
 530
 531         KKASSERT(cursor->flags & HAMMER_CURSOR_TRACKED);
 532
 533         /*
 534          * Relock the inode
 535          */
 536         if (also_ip && (ip = cursor->ip) != NULL) {
 537                 if (cursor->trans->type == HAMMER_TRANS_FLS)
 538                         hammer_lock_ex(&ip->lock);
 539                 else
 540                         hammer_lock_sh(&ip->lock);
 541         }
 542
 543         /*
 544          * Relock the node
 545          */
 546         for (;;) {
 547                 node = cursor->node;
 548                 hammer_ref_node(node);
 549                 hammer_lock_sh(&node->lock);
 550                 if (cursor->node == node) {
 551                         hammer_rel_node(node);
 552                         break;
 553                 }
 554                 hammer_unlock(&node->lock);
 555                 hammer_rel_node(node);
 556         }
 557
 558         /*
 559          * Untrack the cursor, clean up, and re-establish the parent node.
 560          */
 561         TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 562         cursor->flags &= ~HAMMER_CURSOR_TRACKED;
 563
 564         if (cursor->flags & HAMMER_CURSOR_TRACKED_RIPOUT) {
 565                 cursor->flags &= ~HAMMER_CURSOR_TRACKED_RIPOUT;
 566                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 567         }
 568         error = hammer_load_cursor_parent(cursor, 0);
 569         return(error);
 570 }
 571
 572 /*
 573  * Recover from a deadlocked cursor, tracking any node removals or
 574  * replacements.  If the cursor's current node is removed by another
 575  * thread (via btree_remove()) the cursor will be seeked upwards.
 576  *
 577  * The caller is working a modifying operation and must be holding the
 578  * sync lock (shared).  We do not release the sync lock because this
 579  * would break atomicy.
 580  */
 581 int
 582 hammer_recover_cursor(hammer_cursor_t cursor)
 583 {
 584         int error;
 585
 586         hammer_unlock_cursor(cursor, 0);
 587         KKASSERT(cursor->trans->sync_lock_refs > 0);
 588
 589         /*
 590          * Wait for the deadlock to clear
 591          */
 592         if (cursor->deadlk_node) {
 593                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 594                 hammer_unlock(&cursor->deadlk_node->lock);
 595                 hammer_rel_node(cursor->deadlk_node);
 596                 cursor->deadlk_node = NULL;
 597         }
 598         if (cursor->deadlk_rec) {
 599                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 600                 hammer_rel_mem_record(cursor->deadlk_rec);
 601                 cursor->deadlk_rec = NULL;
 602         }
 603         error = hammer_lock_cursor(cursor, 0);
 604         return(error);
 605 }
 606
 607 /*
 608  * Dup ocursor to ncursor.  ncursor inherits ocursor's locks and ocursor
 609  * is effectively unlocked and becomes tracked.  If ocursor was not locked
 610  * then ncursor also inherits the tracking.
 611  *
 612  * After the caller finishes working with ncursor it must be cleaned up
 613  * with hammer_done_cursor(), and the caller must re-lock ocursor.
 614  */
 615 hammer_cursor_t
 616 hammer_push_cursor(hammer_cursor_t ocursor)
 617 {
 618         hammer_cursor_t ncursor;
 619         hammer_inode_t ip;
 620         hammer_node_t node;
 621
 622         ncursor = kmalloc(sizeof(*ncursor), M_HAMMER, M_WAITOK | M_ZERO);
 623         bcopy(ocursor, ncursor, sizeof(*ocursor));
 624
 625         node = ocursor->node;
 626         hammer_ref_node(node);
 627         if ((ocursor->flags & HAMMER_CURSOR_TRACKED) == 0) {
 628                 ocursor->flags |= HAMMER_CURSOR_TRACKED;
 629                 TAILQ_INSERT_TAIL(&node->cursor_list, ocursor, deadlk_entry);
 630         }
 631         if (ncursor->parent)
 632                 ocursor->parent = NULL;
 633         ocursor->data_buffer = NULL;
 634         ocursor->leaf = NULL;
 635         ocursor->data = NULL;
 636         if (ncursor->flags & HAMMER_CURSOR_TRACKED)
 637                 TAILQ_INSERT_TAIL(&node->cursor_list, ncursor, deadlk_entry);
 638         if ((ip = ncursor->ip) != NULL) {
 639                 ++ip->cursor_ip_refs;
 640         }
 641         if (ncursor->iprec)
 642                 hammer_ref(&ncursor->iprec->lock);
 643         return(ncursor);
 644 }
 645
 646 /*
 647  * Destroy ncursor and restore ocursor
 648  *
 649  * This is a temporary hack for the release.  We can't afford to lose
 650  * the IP lock until the IP object scan code is able to deal with it,
 651  * so have ocursor inherit it back.
 652  */
 653 void
 654 hammer_pop_cursor(hammer_cursor_t ocursor, hammer_cursor_t ncursor)
 655 {
 656         hammer_inode_t ip;
 657
 658         ip = ncursor->ip;
 659         ncursor->ip = NULL;
 660         if (ip)
 661                 --ip->cursor_ip_refs;
 662         hammer_done_cursor(ncursor);
 663         kfree(ncursor, M_HAMMER);
 664         KKASSERT(ocursor->ip == ip);
 665         hammer_lock_cursor(ocursor, 0);
 666 }
 667
 668 /*
 669  * onode is being replaced by nnode by the reblocking code.
 670  */
 671 void
 672 hammer_cursor_replaced_node(hammer_node_t onode, hammer_node_t nnode)
 673 {
 674         hammer_cursor_t cursor;
 675
 676         while ((cursor = TAILQ_FIRST(&onode->cursor_list)) != NULL) {
 677                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 678                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 679                 KKASSERT(cursor->node == onode);
 680                 cursor->node = nnode;
 681                 hammer_ref_node(nnode);
 682                 hammer_rel_node(onode);
 683         }
 684 }
 685
 686 /*
 687  * node is being removed, cursors in deadlock recovery are seeked upward
 688  * to the parent.
 689  */
 690 void
 691 hammer_cursor_removed_node(hammer_node_t node, hammer_node_t parent, int index)
 692 {
 693         hammer_cursor_t cursor;
 694
 695         KKASSERT(parent != NULL);
 696         while ((cursor = TAILQ_FIRST(&node->cursor_list)) != NULL) {
 697                 KKASSERT(cursor->node == node);
 698                 KKASSERT(cursor->index == 0);
 699                 TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 700                 TAILQ_INSERT_TAIL(&parent->cursor_list, cursor, deadlk_entry);
 701                 cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
 702                 cursor->node = parent;
 703                 cursor->index = index;
 704                 hammer_ref_node(parent);
 705                 hammer_rel_node(node);
 706         }
 707 }
 708
 709 /*
 710  * node was split at (onode, index) with elements >= index moved to nnode.
 711  */
 712 void
 713 hammer_cursor_split_node(hammer_node_t onode, hammer_node_t nnode, int index)
 714 {
 715         hammer_cursor_t cursor;
 716
 717 again:
 718         TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
 719                 KKASSERT(cursor->node == onode);
 720                 if (cursor->index < index)
 721                         continue;
 722                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 723                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 724                 cursor->node = nnode;
 725                 cursor->index -= index;
 726                 hammer_ref_node(nnode);
 727                 hammer_rel_node(onode);
 728                 goto again;
 729         }
 730 }
 731
 732 /*
 733  * Deleted element at (node, index)
 734  *
 735  * Shift indexes >= index
 736  */
 737 void
 738 hammer_cursor_deleted_element(hammer_node_t node, int index)
 739 {
 740         hammer_cursor_t cursor;
 741
 742         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 743                 KKASSERT(cursor->node == node);
 744                 if (cursor->index == index) {
 745                         cursor->flags |= HAMMER_CURSOR_TRACKED_RIPOUT;
 746                 } else if (cursor->index > index) {
 747                         --cursor->index;
 748                 }
 749         }
 750 }
 751
 752 /*
 753  * Inserted element at (node, index)
 754  *
 755  * Shift indexes >= index
 756  */
 757 void
 758 hammer_cursor_inserted_element(hammer_node_t node, int index)
 759 {
 760         hammer_cursor_t cursor;
 761
 762         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 763                 KKASSERT(cursor->node == node);
 764                 if (cursor->index >= index)
 765                         ++cursor->index;
 766         }
 767 }
 768