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 1.37 2008/07/05 18:59:27 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_lowpri(&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_lowpri(&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         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 (cursor->record_buffer) {
 171                 hammer_rel_buffer(cursor->record_buffer, 0);
 172                 cursor->record_buffer = NULL;
 173         }
 174         if ((ip = cursor->ip) != NULL) {
 175                 if (cursor->iprec) {
 176                         hammer_rel_mem_record(cursor->iprec);
 177                         cursor->iprec = NULL;
 178                 }
 179                 KKASSERT(ip->cursor_ip_refs > 0);
 180                 --ip->cursor_ip_refs;
 181                 hammer_unlock(&ip->lock);
 182                 cursor->ip = NULL;
 183         }
 184
 185         /*
 186          * If we deadlocked this node will be referenced.  Do a quick
 187          * lock/unlock to wait for the deadlock condition to clear.
 188          */
 189         if (cursor->deadlk_node) {
 190                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 191                 hammer_unlock(&cursor->deadlk_node->lock);
 192                 hammer_rel_node(cursor->deadlk_node);
 193                 cursor->deadlk_node = NULL;
 194         }
 195         if (cursor->deadlk_rec) {
 196                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 197                 hammer_rel_mem_record(cursor->deadlk_rec);
 198                 cursor->deadlk_rec = NULL;
 199         }
 200
 201         cursor->data = NULL;
 202         cursor->leaf = NULL;
 203         cursor->left_bound = NULL;
 204         cursor->right_bound = NULL;
 205         cursor->trans = NULL;
 206 }
 207
 208 /*
 209  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 210  * function can return EDEADLK.
 211  *
 212  * The lock must already be either held shared or already held exclusively
 213  * by us.
 214  *
 215  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 216  * we add another reference to the node that failed and set
 217  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 218  */
 219 int
 220 hammer_cursor_upgrade(hammer_cursor_t cursor)
 221 {
 222         int error;
 223
 224         error = hammer_lock_upgrade(&cursor->node->lock);
 225         if (error && cursor->deadlk_node == NULL) {
 226                 cursor->deadlk_node = cursor->node;
 227                 hammer_ref_node(cursor->deadlk_node);
 228         } else if (error == 0 && cursor->parent) {
 229                 error = hammer_lock_upgrade(&cursor->parent->lock);
 230                 if (error && cursor->deadlk_node == NULL) {
 231                         cursor->deadlk_node = cursor->parent;
 232                         hammer_ref_node(cursor->deadlk_node);
 233                 }
 234         }
 235         return(error);
 236 }
 237
 238 int
 239 hammer_cursor_upgrade_node(hammer_cursor_t cursor)
 240 {
 241         int error;
 242
 243         error = hammer_lock_upgrade(&cursor->node->lock);
 244         if (error && cursor->deadlk_node == NULL) {
 245                 cursor->deadlk_node = cursor->node;
 246                 hammer_ref_node(cursor->deadlk_node);
 247         }
 248         return(error);
 249 }
 250
 251 /*
 252  * Downgrade cursor->node and cursor->parent to shared locks.  This
 253  * function can return EDEADLK.
 254  */
 255 void
 256 hammer_cursor_downgrade(hammer_cursor_t cursor)
 257 {
 258         if (hammer_lock_excl_owned(&cursor->node->lock, curthread))
 259                 hammer_lock_downgrade(&cursor->node->lock);
 260         if (cursor->parent &&
 261             hammer_lock_excl_owned(&cursor->parent->lock, curthread)) {
 262                 hammer_lock_downgrade(&cursor->parent->lock);
 263         }
 264 }
 265
 266 /*
 267  * Seek the cursor to the specified node and index.
 268  *
 269  * The caller must ref the node prior to calling this routine and release
 270  * it after it returns.  If the seek succeeds the cursor will gain its own
 271  * ref on the node.
 272  */
 273 int
 274 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 275 {
 276         int error;
 277
 278         hammer_cursor_downgrade(cursor);
 279         error = 0;
 280
 281         if (cursor->node != node) {
 282                 hammer_unlock(&cursor->node->lock);
 283                 hammer_rel_node(cursor->node);
 284                 cursor->node = node;
 285                 hammer_ref_node(node);
 286                 hammer_lock_sh(&node->lock);
 287                 KKASSERT ((node->flags & HAMMER_NODE_DELETED) == 0);
 288
 289                 if (cursor->parent) {
 290                         hammer_unlock(&cursor->parent->lock);
 291                         hammer_rel_node(cursor->parent);
 292                         cursor->parent = NULL;
 293                         cursor->parent_index = 0;
 294                 }
 295                 error = hammer_load_cursor_parent(cursor, 0);
 296         }
 297         cursor->index = index;
 298         return (error);
 299 }
 300
 301 /*
 302  * Load the parent of cursor->node into cursor->parent.
 303  */
 304 static
 305 int
 306 hammer_load_cursor_parent(hammer_cursor_t cursor, int try_exclusive)
 307 {
 308         hammer_mount_t hmp;
 309         hammer_node_t parent;
 310         hammer_node_t node;
 311         hammer_btree_elm_t elm;
 312         int error;
 313         int parent_index;
 314
 315         hmp = cursor->trans->hmp;
 316
 317         if (cursor->node->ondisk->parent) {
 318                 node = cursor->node;
 319                 parent = hammer_btree_get_parent(node, &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->hmp,
 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, node->ondisk->parent, 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
 493 /*
 494  * Recover from a deadlocked cursor, tracking any node removals or
 495  * replacements.  If the cursor's current node is removed by another
 496  * thread (via btree_remove()) the cursor will be seeked upwards.
 497  */
 498 int
 499 hammer_recover_cursor(hammer_cursor_t cursor)
 500 {
 501         hammer_inode_t ip;
 502         hammer_node_t node;
 503         int status;
 504         int error;
 505
 506 again:
 507         KKASSERT((cursor->flags & HAMMER_CURSOR_DEADLK_RECOVER) == 0);
 508         KKASSERT(cursor->node);
 509         /*
 510          * Release the cursor's locks and track B-Tree operations on node.
 511          * While being tracked our cursor can be modified by other threads
 512          * and node may be replaced.
 513          */
 514         if (cursor->parent) {
 515                 hammer_unlock(&cursor->parent->lock);
 516                 hammer_rel_node(cursor->parent);
 517                 cursor->parent = NULL;
 518         }
 519         node = cursor->node;
 520         cursor->flags |= HAMMER_CURSOR_DEADLK_RECOVER;
 521         TAILQ_INSERT_TAIL(&node->cursor_list, cursor, deadlk_entry);
 522         status = hammer_lock_status(&node->lock);
 523         hammer_unlock(&node->lock);
 524
 525         if ((ip = cursor->ip) != NULL)
 526                 hammer_unlock(&ip->lock);
 527
 528         /*
 529          * Wait for the deadlock to clear
 530          */
 531         if (cursor->deadlk_node) {
 532                 hammer_lock_ex_ident(&cursor->deadlk_node->lock, "hmrdlk");
 533                 hammer_unlock(&cursor->deadlk_node->lock);
 534                 hammer_rel_node(cursor->deadlk_node);
 535                 cursor->deadlk_node = NULL;
 536         }
 537         if (cursor->deadlk_rec) {
 538                 hammer_wait_mem_record_ident(cursor->deadlk_rec, "hmmdlr");
 539                 hammer_rel_mem_record(cursor->deadlk_rec);
 540                 cursor->deadlk_rec = NULL;
 541         }
 542
 543         /*
 544          * Get the cursor heated up again.  The cursor's node may have
 545          * changed and we might have to locate the new parent.
 546          *
 547          * If the exact element we were on got deleted RIPOUT will be
 548          * set and we must clear ATEDISK so an iteration does not skip
 549          * the element after it.
 550          */
 551         KKASSERT(cursor->flags & HAMMER_CURSOR_DEADLK_RECOVER);
 552         node = cursor->node;
 553         TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 554         cursor->flags &= ~HAMMER_CURSOR_DEADLK_RECOVER;
 555         if (cursor->flags & HAMMER_CURSOR_DEADLK_RIPOUT) {
 556                 cursor->flags &= ~HAMMER_CURSOR_DEADLK_RIPOUT;
 557                 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
 558         }
 559         hammer_lock_sh(&node->lock);
 560         error = hammer_load_cursor_parent(cursor, 0);
 561         if (error == 0) {
 562                 if (status > 0) {
 563                         error = hammer_cursor_upgrade(cursor);
 564                         if (error == EDEADLK) {
 565                                 kprintf("r");
 566                                 goto again;
 567                         }
 568                 }
 569         }
 570         return(error);
 571 }
 572
 573 /*
 574  * onode is being replaced by nnode by the reblocking code.
 575  */
 576 void
 577 hammer_cursor_replaced_node(hammer_node_t onode, hammer_node_t nnode)
 578 {
 579         hammer_cursor_t cursor;
 580
 581         while ((cursor = TAILQ_FIRST(&onode->cursor_list)) != NULL) {
 582                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 583                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 584                 KKASSERT(cursor->node == onode);
 585                 cursor->node = nnode;
 586                 hammer_ref_node(nnode);
 587                 hammer_rel_node(onode);
 588         }
 589 }
 590
 591 /*
 592  * node is being removed, cursors in deadlock recovery are seeked upward
 593  * to the parent.
 594  */
 595 void
 596 hammer_cursor_removed_node(hammer_node_t node, hammer_node_t parent, int index)
 597 {
 598         hammer_cursor_t cursor;
 599
 600         KKASSERT(parent != NULL);
 601         while ((cursor = TAILQ_FIRST(&node->cursor_list)) != NULL) {
 602                 KKASSERT(cursor->node == node);
 603                 KKASSERT(cursor->index == 0);
 604                 TAILQ_REMOVE(&node->cursor_list, cursor, deadlk_entry);
 605                 TAILQ_INSERT_TAIL(&parent->cursor_list, cursor, deadlk_entry);
 606                 cursor->flags |= HAMMER_CURSOR_DEADLK_RIPOUT;
 607                 cursor->node = parent;
 608                 cursor->index = index;
 609                 hammer_ref_node(parent);
 610                 hammer_rel_node(node);
 611         }
 612 }
 613
 614 /*
 615  * node was split at (onode, index) with elements >= index moved to nnode.
 616  */
 617 void
 618 hammer_cursor_split_node(hammer_node_t onode, hammer_node_t nnode, int index)
 619 {
 620         hammer_cursor_t cursor;
 621
 622 again:
 623         TAILQ_FOREACH(cursor, &onode->cursor_list, deadlk_entry) {
 624                 KKASSERT(cursor->node == onode);
 625                 if (cursor->index < index)
 626                         continue;
 627                 TAILQ_REMOVE(&onode->cursor_list, cursor, deadlk_entry);
 628                 TAILQ_INSERT_TAIL(&nnode->cursor_list, cursor, deadlk_entry);
 629                 cursor->node = nnode;
 630                 cursor->index -= index;
 631                 hammer_ref_node(nnode);
 632                 hammer_rel_node(onode);
 633                 goto again;
 634         }
 635 }
 636
 637 /*
 638  * Inserted element at (node, index)
 639  *
 640  * Shift indexes >= index
 641  */
 642 void
 643 hammer_cursor_deleted_element(hammer_node_t node, int index)
 644 {
 645         hammer_cursor_t cursor;
 646
 647         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 648                 KKASSERT(cursor->node == node);
 649                 if (cursor->index == index) {
 650                         cursor->flags |= HAMMER_CURSOR_DEADLK_RIPOUT;
 651                 } else if (cursor->index > index) {
 652                         --cursor->index;
 653                 }
 654         }
 655 }
 656
 657 /*
 658  * Deleted element at (node, index)
 659  *
 660  * Shift indexes >= index
 661  */
 662 void
 663 hammer_cursor_inserted_element(hammer_node_t node, int index)
 664 {
 665         hammer_cursor_t cursor;
 666
 667         TAILQ_FOREACH(cursor, &node->cursor_list, deadlk_entry) {
 668                 KKASSERT(cursor->node == node);
 669                 if (cursor->index >= index)
 670                         ++cursor->index;
 671         }
 672 }
 673