lustre/ldlm/interval_tree.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  19  *
  20  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  21  * CA 95054 USA or visit www.sun.com if you need additional information or
  22  * have any questions.
  23  *
  24  * GPL HEADER END
  25  */
  26 /*
  27  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 /*
  31  * This file is part of Lustre, http://www.lustre.org/
  32  * Lustre is a trademark of Sun Microsystems, Inc.
  33  *
  34  * lustre/ldlm/interval_tree.c
  35  *
  36  * Interval tree library used by ldlm extent lock code
  37  *
  38  * Author: Huang Wei <huangwei@clusterfs.com>
  39  * Author: Jay Xiong <jinshan.xiong@sun.com>
  40  */
  41 #ifdef __KERNEL__
  42 # include <lustre_dlm.h>
  43 #else
  44 # include <liblustre.h>
  45 #endif
  46 #include <obd_support.h>
  47 #include <interval_tree.h>
  48
  49 enum {
  50         INTERVAL_RED = 0,
  51         INTERVAL_BLACK = 1
  52 };
  53
  54 static inline int node_is_left_child(struct interval_node *node)
  55 {
  56         LASSERT(node->in_parent != NULL);
  57         return node == node->in_parent->in_left;
  58 }
  59
  60 static inline int node_is_right_child(struct interval_node *node)
  61 {
  62         LASSERT(node->in_parent != NULL);
  63         return node == node->in_parent->in_right;
  64 }
  65
  66 static inline int node_is_red(struct interval_node *node)
  67 {
  68         return node->in_color == INTERVAL_RED;
  69 }
  70
  71 static inline int node_is_black(struct interval_node *node)
  72 {
  73         return node->in_color == INTERVAL_BLACK;
  74 }
  75
  76 static inline int extent_compare(struct interval_node_extent *e1,
  77                                  struct interval_node_extent *e2)
  78 {
  79         int rc;
  80         if (e1->start == e2->start) {
  81                 if (e1->end < e2->end)
  82                         rc = -1;
  83                 else if (e1->end > e2->end)
  84                         rc = 1;
  85                 else
  86                         rc = 0;
  87         } else {
  88                 if (e1->start < e2->start)
  89                         rc = -1;
  90                 else
  91                         rc = 1;
  92         }
  93         return rc;
  94 }
  95
  96 static inline int extent_equal(struct interval_node_extent *e1,
  97                                struct interval_node_extent *e2)
  98 {
  99         return (e1->start == e2->start) && (e1->end == e2->end);
 100 }
 101
 102 static inline int extent_overlapped(struct interval_node_extent *e1,
 103                                     struct interval_node_extent *e2)
 104 {
 105         return (e1->start <= e2->end) && (e2->start <= e1->end);
 106 }
 107
 108 static inline int node_compare(struct interval_node *n1,
 109                                struct interval_node *n2)
 110 {
 111         return extent_compare(&n1->in_extent, &n2->in_extent);
 112 }
 113
 114 static inline int node_equal(struct interval_node *n1,
 115                              struct interval_node *n2)
 116 {
 117         return extent_equal(&n1->in_extent, &n2->in_extent);
 118 }
 119
 120 static inline __u64 max_u64(__u64 x, __u64 y)
 121 {
 122         return x > y ? x : y;
 123 }
 124
 125 static inline __u64 min_u64(__u64 x, __u64 y)
 126 {
 127         return x < y ? x : y;
 128 }
 129
 130 #define interval_for_each(node, root)                   \
 131 for (node = interval_first(root); node != NULL;         \
 132      node = interval_next(node))
 133
 134 #define interval_for_each_reverse(node, root)           \
 135 for (node = interval_last(root); node != NULL;          \
 136      node = interval_prev(node))
 137
 138 static struct interval_node *interval_first(struct interval_node *node)
 139 {
 140         ENTRY;
 141
 142         if (!node)
 143                 RETURN(NULL);
 144         while (node->in_left)
 145                 node = node->in_left;
 146         RETURN(node);
 147 }
 148
 149 static struct interval_node *interval_last(struct interval_node *node)
 150 {
 151         ENTRY;
 152
 153         if (!node)
 154                 RETURN(NULL);
 155         while (node->in_right)
 156                 node = node->in_right;
 157         RETURN(node);
 158 }
 159
 160 static struct interval_node *interval_next(struct interval_node *node)
 161 {
 162         ENTRY;
 163
 164         if (!node)
 165                 RETURN(NULL);
 166         if (node->in_right)
 167                 RETURN(interval_first(node->in_right));
 168         while (node->in_parent && node_is_right_child(node))
 169                 node = node->in_parent;
 170         RETURN(node->in_parent);
 171 }
 172
 173 static struct interval_node *interval_prev(struct interval_node *node)
 174 {
 175         ENTRY;
 176
 177         if (!node)
 178                 RETURN(NULL);
 179
 180         if (node->in_left)
 181                 RETURN(interval_last(node->in_left));
 182
 183         while (node->in_parent && node_is_left_child(node))
 184                 node = node->in_parent;
 185
 186         RETURN(node->in_parent);
 187 }
 188
 189 enum interval_iter interval_iterate(struct interval_node *root,
 190                                     interval_callback_t func,
 191                                     void *data)
 192 {
 193         struct interval_node *node;
 194         enum interval_iter rc = INTERVAL_ITER_CONT;
 195         ENTRY;
 196
 197         interval_for_each(node, root) {
 198                 rc = func(node, data);
 199                 if (rc == INTERVAL_ITER_STOP)
 200                         break;
 201         }
 202
 203         RETURN(rc);
 204 }
 205 EXPORT_SYMBOL(interval_iterate);
 206
 207 enum interval_iter interval_iterate_reverse(struct interval_node *root,
 208                                             interval_callback_t func,
 209                                             void *data)
 210 {
 211         struct interval_node *node;
 212         enum interval_iter rc = INTERVAL_ITER_CONT;
 213         ENTRY;
 214
 215         interval_for_each_reverse(node, root) {
 216                 rc = func(node, data);
 217                 if (rc == INTERVAL_ITER_STOP)
 218                         break;
 219         }
 220
 221         RETURN(rc);
 222 }
 223 EXPORT_SYMBOL(interval_iterate_reverse);
 224
 225 /* try to find a node with same interval in the tree,
 226  * if found, return the pointer to the node, otherwise return NULL*/
 227 struct interval_node *interval_find(struct interval_node *root,
 228                                     struct interval_node_extent *ex)
 229 {
 230         struct interval_node *walk = root;
 231         int rc;
 232         ENTRY;
 233
 234         while (walk) {
 235                 rc = extent_compare(ex, &walk->in_extent);
 236                 if (rc == 0)
 237                         break;
 238                 else if (rc < 0)
 239                         walk = walk->in_left;
 240                 else
 241                         walk = walk->in_right;
 242         }
 243
 244         RETURN(walk);
 245 }
 246 EXPORT_SYMBOL(interval_find);
 247
 248 static void __rotate_change_maxhigh(struct interval_node *node,
 249                                     struct interval_node *rotate)
 250 {
 251         __u64 left_max, right_max;
 252
 253         rotate->in_max_high = node->in_max_high;
 254         left_max = node->in_left ? node->in_left->in_max_high : 0;
 255         right_max = node->in_right ? node->in_right->in_max_high : 0;
 256         node->in_max_high  = max_u64(interval_high(node),
 257                                      max_u64(left_max,right_max));
 258 }
 259
 260 /* The left rotation "pivots" around the link from node to node->right, and
 261  * - node will be linked to node->right's left child, and
 262  * - node->right's left child will be linked to node's right child.  */
 263 static void __rotate_left(struct interval_node *node,
 264                           struct interval_node **root)
 265 {
 266         struct interval_node *right = node->in_right;
 267         struct interval_node *parent = node->in_parent;
 268
 269         node->in_right = right->in_left;
 270         if (node->in_right)
 271                 right->in_left->in_parent = node;
 272
 273         right->in_left = node;
 274         right->in_parent = parent;
 275         if (parent) {
 276                 if (node_is_left_child(node))
 277                         parent->in_left = right;
 278                 else
 279                         parent->in_right = right;
 280         } else {
 281                 *root = right;
 282         }
 283         node->in_parent = right;
 284
 285         /* update max_high for node and right */
 286         __rotate_change_maxhigh(node, right);
 287 }
 288
 289 /* The right rotation "pivots" around the link from node to node->left, and
 290  * - node will be linked to node->left's right child, and
 291  * - node->left's right child will be linked to node's left child.  */
 292 static void __rotate_right(struct interval_node *node,
 293                            struct interval_node **root)
 294 {
 295         struct interval_node *left = node->in_left;
 296         struct interval_node *parent = node->in_parent;
 297
 298         node->in_left = left->in_right;
 299         if (node->in_left)
 300                 left->in_right->in_parent = node;
 301         left->in_right = node;
 302
 303         left->in_parent = parent;
 304         if (parent) {
 305                 if (node_is_right_child(node))
 306                         parent->in_right = left;
 307                 else
 308                         parent->in_left = left;
 309         } else {
 310                 *root = left;
 311         }
 312         node->in_parent = left;
 313
 314         /* update max_high for node and left */
 315         __rotate_change_maxhigh(node, left);
 316 }
 317
 318 #define interval_swap(a, b) do {                        \
 319         struct interval_node *c = a; a = b; b = c;      \
 320 } while (0)
 321
 322 /*
 323  * Operations INSERT and DELETE, when run on a tree with n keys,
 324  * take O(logN) time.Because they modify the tree, the result
 325  * may violate the red-black properties.To restore these properties,
 326  * we must change the colors of some of the nodes in the tree
 327  * and also change the pointer structure.
 328  */
 329 static void interval_insert_color(struct interval_node *node,
 330                                   struct interval_node **root)
 331 {
 332         struct interval_node *parent, *gparent;
 333         ENTRY;
 334
 335         while ((parent = node->in_parent) && node_is_red(parent)) {
 336                 gparent = parent->in_parent;
 337                 /* Parent is RED, so gparent must not be NULL */
 338                 if (node_is_left_child(parent)) {
 339                         struct interval_node *uncle;
 340                         uncle = gparent->in_right;
 341                         if (uncle && node_is_red(uncle)) {
 342                                 uncle->in_color = INTERVAL_BLACK;
 343                                 parent->in_color = INTERVAL_BLACK;
 344                                 gparent->in_color = INTERVAL_RED;
 345                                 node = gparent;
 346                                 continue;
 347                         }
 348
 349                         if (parent->in_right == node) {
 350                                 __rotate_left(parent, root);
 351                                 interval_swap(node, parent);
 352                         }
 353
 354                         parent->in_color = INTERVAL_BLACK;
 355                         gparent->in_color = INTERVAL_RED;
 356                         __rotate_right(gparent, root);
 357                 } else {
 358                         struct interval_node *uncle;
 359                         uncle = gparent->in_left;
 360                         if (uncle && node_is_red(uncle)) {
 361                                 uncle->in_color = INTERVAL_BLACK;
 362                                 parent->in_color = INTERVAL_BLACK;
 363                                 gparent->in_color = INTERVAL_RED;
 364                                 node = gparent;
 365                                 continue;
 366                         }
 367
 368                         if (node_is_left_child(node)) {
 369                                 __rotate_right(parent, root);
 370                                 interval_swap(node, parent);
 371                         }
 372
 373                         parent->in_color = INTERVAL_BLACK;
 374                         gparent->in_color = INTERVAL_RED;
 375                         __rotate_left(gparent, root);
 376                 }
 377         }
 378
 379         (*root)->in_color = INTERVAL_BLACK;
 380         EXIT;
 381 }
 382
 383 struct interval_node *interval_insert(struct interval_node *node,
 384                                       struct interval_node **root)
 385
 386 {
 387         struct interval_node **p, *parent = NULL;
 388         ENTRY;
 389
 390         LASSERT(!interval_is_intree(node));
 391         p = root;
 392         while (*p) {
 393                 parent = *p;
 394                 if (node_equal(parent, node))
 395                         RETURN(parent);
 396
 397                 /* max_high field must be updated after each iteration */
 398                 if (parent->in_max_high < interval_high(node))
 399                         parent->in_max_high = interval_high(node);
 400
 401                 if (node_compare(node, parent) < 0)
 402                         p = &parent->in_left;
 403                 else
 404                         p = &parent->in_right;
 405         }
 406
 407         /* link node into the tree */
 408         node->in_parent = parent;
 409         node->in_color = INTERVAL_RED;
 410         node->in_left = node->in_right = NULL;
 411         *p = node;
 412
 413         interval_insert_color(node, root);
 414         node->in_intree = 1;
 415
 416         RETURN(NULL);
 417 }
 418 EXPORT_SYMBOL(interval_insert);
 419
 420 static inline int node_is_black_or_0(struct interval_node *node)
 421 {
 422         return !node || node_is_black(node);
 423 }
 424
 425 static void interval_erase_color(struct interval_node *node,
 426                                  struct interval_node *parent,
 427                                  struct interval_node **root)
 428 {
 429         struct interval_node *tmp;
 430         ENTRY;
 431
 432         while (node_is_black_or_0(node) && node != *root) {
 433                 if (parent->in_left == node) {
 434                         tmp = parent->in_right;
 435                         if (node_is_red(tmp)) {
 436                                 tmp->in_color = INTERVAL_BLACK;
 437                                 parent->in_color = INTERVAL_RED;
 438                                 __rotate_left(parent, root);
 439                                 tmp = parent->in_right;
 440                         }
 441                         if (node_is_black_or_0(tmp->in_left) &&
 442                             node_is_black_or_0(tmp->in_right)) {
 443                                 tmp->in_color = INTERVAL_RED;
 444                                 node = parent;
 445                                 parent = node->in_parent;
 446                         } else {
 447                                 if (node_is_black_or_0(tmp->in_right)) {
 448                                         struct interval_node *o_left;
 449                                         if ((o_left = tmp->in_left))
 450                                              o_left->in_color = INTERVAL_BLACK;
 451                                         tmp->in_color = INTERVAL_RED;
 452                                         __rotate_right(tmp, root);
 453                                         tmp = parent->in_right;
 454                                 }
 455                                 tmp->in_color = parent->in_color;
 456                                 parent->in_color = INTERVAL_BLACK;
 457                                 if (tmp->in_right)
 458                                     tmp->in_right->in_color = INTERVAL_BLACK;
 459                                 __rotate_left(parent, root);
 460                                 node = *root;
 461                                 break;
 462                         }
 463                 } else {
 464                         tmp = parent->in_left;
 465                         if (node_is_red(tmp)) {
 466                                 tmp->in_color = INTERVAL_BLACK;
 467                                 parent->in_color = INTERVAL_RED;
 468                                 __rotate_right(parent, root);
 469                                 tmp = parent->in_left;
 470                         }
 471                         if (node_is_black_or_0(tmp->in_left) &&
 472                             node_is_black_or_0(tmp->in_right)) {
 473                                 tmp->in_color = INTERVAL_RED;
 474                                 node = parent;
 475                                 parent = node->in_parent;
 476                         } else {
 477                                 if (node_is_black_or_0(tmp->in_left)) {
 478                                         struct interval_node *o_right;
 479                                         if ((o_right = tmp->in_right))
 480                                             o_right->in_color = INTERVAL_BLACK;
 481                                         tmp->in_color = INTERVAL_RED;
 482                                         __rotate_left(tmp, root);
 483                                         tmp = parent->in_left;
 484                                 }
 485                                 tmp->in_color = parent->in_color;
 486                                 parent->in_color = INTERVAL_BLACK;
 487                                 if (tmp->in_left)
 488                                         tmp->in_left->in_color = INTERVAL_BLACK;
 489                                 __rotate_right(parent, root);
 490                                 node = *root;
 491                                 break;
 492                         }
 493                 }
 494         }
 495         if (node)
 496                 node->in_color = INTERVAL_BLACK;
 497         EXIT;
 498 }
 499
 500 /*
 501  * if the @max_high value of @node is changed, this function traverse  a path
 502  * from node  up to the root to update max_high for the whole tree.
 503  */
 504 static void update_maxhigh(struct interval_node *node,
 505                            __u64  old_maxhigh)
 506 {
 507         __u64 left_max, right_max;
 508         ENTRY;
 509
 510         while (node) {
 511                 left_max = node->in_left ? node->in_left->in_max_high : 0;
 512                 right_max = node->in_right ? node->in_right->in_max_high : 0;
 513                 node->in_max_high = max_u64(interval_high(node),
 514                                             max_u64(left_max, right_max));
 515
 516                 if (node->in_max_high >= old_maxhigh)
 517                         break;
 518                 node = node->in_parent;
 519         }
 520         EXIT;
 521 }
 522
 523 void interval_erase(struct interval_node *node,
 524                     struct interval_node **root)
 525 {
 526         struct interval_node *child, *parent;
 527         int color;
 528         ENTRY;
 529
 530         LASSERT(interval_is_intree(node));
 531         node->in_intree = 0;
 532         if (!node->in_left) {
 533                 child = node->in_right;
 534         } else if (!node->in_right) {
 535                 child = node->in_left;
 536         } else { /* Both left and right child are not NULL */
 537                 struct interval_node *old = node;
 538
 539                 node = interval_next(node);
 540                 child = node->in_right;
 541                 parent = node->in_parent;
 542                 color = node->in_color;
 543
 544                 if (child)
 545                         child->in_parent = parent;
 546                 if (parent == old)
 547                         parent->in_right = child;
 548                 else
 549                         parent->in_left = child;
 550
 551                 node->in_color = old->in_color;
 552                 node->in_right = old->in_right;
 553                 node->in_left = old->in_left;
 554                 node->in_parent = old->in_parent;
 555
 556                 if (old->in_parent) {
 557                         if (node_is_left_child(old))
 558                                 old->in_parent->in_left = node;
 559                         else
 560                                 old->in_parent->in_right = node;
 561                 } else {
 562                         *root = node;
 563                 }
 564
 565                 old->in_left->in_parent = node;
 566                 if (old->in_right)
 567                         old->in_right->in_parent = node;
 568                 update_maxhigh(child ? : parent, node->in_max_high);
 569                 update_maxhigh(node, old->in_max_high);
 570                 if (parent == old)
 571                          parent = node;
 572                 goto color;
 573         }
 574         parent = node->in_parent;
 575         color = node->in_color;
 576
 577         if (child)
 578                 child->in_parent = parent;
 579         if (parent) {
 580                 if (node_is_left_child(node))
 581                         parent->in_left = child;
 582                 else
 583                         parent->in_right = child;
 584         } else {
 585                 *root = child;
 586         }
 587
 588         update_maxhigh(child ? : parent, node->in_max_high);
 589
 590 color:
 591         if (color == INTERVAL_BLACK)
 592                 interval_erase_color(child, parent, root);
 593         EXIT;
 594 }
 595 EXPORT_SYMBOL(interval_erase);
 596
 597 static inline int interval_may_overlap(struct interval_node *node,
 598                                           struct interval_node_extent *ext)
 599 {
 600         return (ext->start <= node->in_max_high &&
 601                 ext->end >= interval_low(node));
 602 }
 603
 604 /*
 605  * This function finds all intervals that overlap interval ext,
 606  * and calls func to handle resulted intervals one by one.
 607  * in lustre, this function will find all conflicting locks in
 608  * the granted queue and add these locks to the ast work list.
 609  *
 610  * {
 611  *       if (node == NULL)
 612  *               return 0;
 613  *       if (ext->end < interval_low(node)) {
 614  *               interval_search(node->in_left, ext, func, data);
 615  *       } else if (interval_may_overlap(node, ext)) {
 616  *               if (extent_overlapped(ext, &node->in_extent))
 617  *                       func(node, data);
 618  *               interval_search(node->in_left, ext, func, data);
 619  *               interval_search(node->in_right, ext, func, data);
 620  *       }
 621  *       return 0;
 622  * }
 623  *
 624  */
 625 enum interval_iter interval_search(struct interval_node *node,
 626                                    struct interval_node_extent *ext,
 627                                    interval_callback_t func,
 628                                    void *data)
 629 {
 630         struct interval_node *parent;
 631         enum interval_iter rc = INTERVAL_ITER_CONT;
 632
 633         LASSERT(ext != NULL);
 634         LASSERT(func != NULL);
 635
 636         while (node) {
 637                 if (ext->end < interval_low(node)) {
 638                         if (node->in_left) {
 639                                 node = node->in_left;
 640                                 continue;
 641                         }
 642                 } else if (interval_may_overlap(node, ext)) {
 643                         if (extent_overlapped(ext, &node->in_extent)) {
 644                                 rc = func(node, data);
 645                                 if (rc == INTERVAL_ITER_STOP)
 646                                         break;
 647                         }
 648
 649                         if (node->in_left) {
 650                                 node = node->in_left;
 651                                 continue;
 652                         }
 653                         if (node->in_right) {
 654                                 node = node->in_right;
 655                                 continue;
 656                         }
 657                 }
 658
 659                 parent = node->in_parent;
 660                 while (parent) {
 661                         if (node_is_left_child(node) &&
 662                             parent->in_right) {
 663                                 /* If we ever got the left, it means that the
 664                                  * parent met ext->end<interval_low(parent), or
 665                                  * may_overlap(parent). If the former is true,
 666                                  * we needn't go back. So stop early and check
 667                                  * may_overlap(parent) after this loop.  */
 668                                 node = parent->in_right;
 669                                 break;
 670                         }
 671                         node = parent;
 672                         parent = parent->in_parent;
 673                 }
 674                 if (parent == NULL || !interval_may_overlap(parent, ext))
 675                         break;
 676         }
 677
 678         return rc;
 679 }
 680 EXPORT_SYMBOL(interval_search);
 681
 682 static enum interval_iter interval_overlap_cb(struct interval_node *n,
 683                                               void *args)
 684 {
 685         *(int *)args = 1;
 686         return INTERVAL_ITER_STOP;
 687 }
 688
 689 int interval_is_overlapped(struct interval_node *root,
 690                            struct interval_node_extent *ext)
 691 {
 692         int has = 0;
 693         (void)interval_search(root, ext, interval_overlap_cb, &has);
 694         return has;
 695 }
 696 EXPORT_SYMBOL(interval_is_overlapped);
 697
 698 /* Don't expand to low. Expanding downwards is expensive, and meaningless to
 699  * some extents, because programs seldom do IO backward.
 700  *
 701  * The recursive algorithm of expanding low:
 702  * expand_low {
 703  *        struct interval_node *tmp;
 704  *        static __u64 res = 0;
 705  *
 706  *        if (root == NULL)
 707  *                return res;
 708  *        if (root->in_max_high < low) {
 709  *                res = max_u64(root->in_max_high + 1, res);
 710  *                return res;
 711  *        } else if (low < interval_low(root)) {
 712  *                interval_expand_low(root->in_left, low);
 713  *                return res;
 714  *        }
 715  *
 716  *        if (interval_high(root) < low)
 717  *                res = max_u64(interval_high(root) + 1, res);
 718  *        interval_expand_low(root->in_left, low);
 719  *        interval_expand_low(root->in_right, low);
 720  *
 721  *        return res;
 722  * }
 723  *
 724  * It's much easy to eliminate the recursion, see interval_search for
 725  * an example. -jay
 726  */
 727 static inline __u64 interval_expand_low(struct interval_node *root, __u64 low)
 728 {
 729         /* we only concern the empty tree right now. */
 730         if (root == NULL)
 731                 return 0;
 732         return low;
 733 }
 734
 735 static inline __u64 interval_expand_high(struct interval_node *node, __u64 high)
 736 {
 737         __u64 result = ~0;
 738
 739         while (node != NULL) {
 740                 if (node->in_max_high < high)
 741                         break;
 742
 743                 if (interval_low(node) > high) {
 744                         result = interval_low(node) - 1;
 745                         node = node->in_left;
 746                 } else {
 747                         node = node->in_right;
 748                 }
 749         }
 750
 751         return result;
 752 }
 753
 754 /* expanding the extent based on @ext. */
 755 void interval_expand(struct interval_node *root,
 756                      struct interval_node_extent *ext,
 757                      struct interval_node_extent *limiter)
 758 {
 759         /* The assertion of interval_is_overlapped is expensive because we may
 760          * travel many nodes to find the overlapped node. */
 761         LASSERT(interval_is_overlapped(root, ext) == 0);
 762         if (!limiter || limiter->start < ext->start)
 763                 ext->start = interval_expand_low(root, ext->start);
 764         if (!limiter || limiter->end > ext->end)
 765                 ext->end = interval_expand_high(root, ext->end);
 766         LASSERT(interval_is_overlapped(root, ext) == 0);
 767 }
 768 EXPORT_SYMBOL(interval_expand);