lustre/ldlm/interval_tree.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * GPL HEADER START
   5  *
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License version 2 for more details (a copy is included
  16  * in the LICENSE file that accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * version 2 along with this program; If not, see
  20  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  25  *
  26  * GPL HEADER END
  27  */
  28 /*
  29  * Copyright  2008 Sun Microsystems, Inc. All rights reserved
  30  * Use is subject to license terms.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * lustre/ldlm/interval_tree.c
  37  *
  38  * Interval tree library used by ldlm extent lock code
  39  *
  40  * Author: Huang Wei <huangwei@clusterfs.com>
  41  * Author: Jay Xiong <jinshan.xiong@sun.com>
  42  */
  43 #ifdef __KERNEL__
  44 # include <lustre_dlm.h>
  45 #else
  46 # include <liblustre.h>
  47 #endif
  48 #include <obd_support.h>
  49 #include <interval_tree.h>
  50
  51 enum {
  52         INTERVAL_RED = 0,
  53         INTERVAL_BLACK = 1
  54 };
  55
  56 static inline int node_is_left_child(struct interval_node *node)
  57 {
  58         LASSERT(node->in_parent != NULL);
  59         return node == node->in_parent->in_left;
  60 }
  61
  62 static inline int node_is_right_child(struct interval_node *node)
  63 {
  64         LASSERT(node->in_parent != NULL);
  65         return node == node->in_parent->in_right;
  66 }
  67
  68 static inline int node_is_red(struct interval_node *node)
  69 {
  70         return node->in_color == INTERVAL_RED;
  71 }
  72
  73 static inline int node_is_black(struct interval_node *node)
  74 {
  75         return node->in_color == INTERVAL_BLACK;
  76 }
  77
  78 static inline int extent_compare(struct interval_node_extent *e1,
  79                                  struct interval_node_extent *e2)
  80 {
  81         int rc;
  82         if (e1->start == e2->start) {
  83                 if (e1->end < e2->end)
  84                         rc = -1;
  85                 else if (e1->end > e2->end)
  86                         rc = 1;
  87                 else
  88                         rc = 0;
  89         } else {
  90                 if (e1->start < e2->start)
  91                         rc = -1;
  92                 else
  93                         rc = 1;
  94         }
  95         return rc;
  96 }
  97
  98 static inline int extent_equal(struct interval_node_extent *e1,
  99                                struct interval_node_extent *e2)
 100 {
 101         return (e1->start == e2->start) && (e1->end == e2->end);
 102 }
 103
 104 static inline int extent_overlapped(struct interval_node_extent *e1,
 105                                     struct interval_node_extent *e2)
 106 {
 107         return (e1->start <= e2->end) && (e2->start <= e1->end);
 108 }
 109
 110 static inline int node_compare(struct interval_node *n1,
 111                                struct interval_node *n2)
 112 {
 113         return extent_compare(&n1->in_extent, &n2->in_extent);
 114 }
 115
 116 static inline int node_equal(struct interval_node *n1,
 117                              struct interval_node *n2)
 118 {
 119         return extent_equal(&n1->in_extent, &n2->in_extent);
 120 }
 121
 122 static inline __u64 max_u64(__u64 x, __u64 y)
 123 {
 124         return x > y ? x : y;
 125 }
 126
 127 static inline __u64 min_u64(__u64 x, __u64 y)
 128 {
 129         return x < y ? x : y;
 130 }
 131
 132 #define interval_for_each(node, root)                   \
 133 for (node = interval_first(root); node != NULL;         \
 134      node = interval_next(node))
 135
 136 #define interval_for_each_reverse(node, root)           \
 137 for (node = interval_last(root); node != NULL;          \
 138      node = interval_prev(node))
 139
 140 static struct interval_node *interval_first(struct interval_node *node)
 141 {
 142         ENTRY;
 143
 144         if (!node)
 145                 RETURN(NULL);
 146         while (node->in_left)
 147                 node = node->in_left;
 148         RETURN(node);
 149 }
 150
 151 static struct interval_node *interval_last(struct interval_node *node)
 152 {
 153         ENTRY;
 154
 155         if (!node)
 156                 RETURN(NULL);
 157         while (node->in_right)
 158                 node = node->in_right;
 159         RETURN(node);
 160 }
 161
 162 static struct interval_node *interval_next(struct interval_node *node)
 163 {
 164         ENTRY;
 165
 166         if (!node)
 167                 RETURN(NULL);
 168         if (node->in_right)
 169                 RETURN(interval_first(node->in_right));
 170         while (node->in_parent && node_is_right_child(node))
 171                 node = node->in_parent;
 172         RETURN(node->in_parent);
 173 }
 174
 175 static struct interval_node *interval_prev(struct interval_node *node)
 176 {
 177         ENTRY;
 178
 179         if (!node)
 180                 RETURN(NULL);
 181
 182         if (node->in_left)
 183                 RETURN(interval_last(node->in_left));
 184
 185         while (node->in_parent && node_is_left_child(node))
 186                 node = node->in_parent;
 187
 188         RETURN(node->in_parent);
 189 }
 190
 191 enum interval_iter interval_iterate(struct interval_node *root,
 192                                     interval_callback_t func,
 193                                     void *data)
 194 {
 195         struct interval_node *node;
 196         enum interval_iter rc = INTERVAL_ITER_CONT;
 197         ENTRY;
 198
 199         interval_for_each(node, root) {
 200                 rc = func(node, data);
 201                 if (rc == INTERVAL_ITER_STOP)
 202                         break;
 203         }
 204
 205         RETURN(rc);
 206 }
 207 EXPORT_SYMBOL(interval_iterate);
 208
 209 enum interval_iter interval_iterate_reverse(struct interval_node *root,
 210                                             interval_callback_t func,
 211                                             void *data)
 212 {
 213         struct interval_node *node;
 214         enum interval_iter rc = INTERVAL_ITER_CONT;
 215         ENTRY;
 216
 217         interval_for_each_reverse(node, root) {
 218                 rc = func(node, data);
 219                 if (rc == INTERVAL_ITER_STOP)
 220                         break;
 221         }
 222
 223         RETURN(rc);
 224 }
 225 EXPORT_SYMBOL(interval_iterate_reverse);
 226
 227 /* try to find a node with same interval in the tree,
 228  * if found, return the pointer to the node, otherwise return NULL*/
 229 struct interval_node *interval_find(struct interval_node *root,
 230                                     struct interval_node_extent *ex)
 231 {
 232         struct interval_node *walk = root;
 233         int rc;
 234         ENTRY;
 235
 236         while (walk) {
 237                 rc = extent_compare(ex, &walk->in_extent);
 238                 if (rc == 0)
 239                         break;
 240                 else if (rc < 0)
 241                         walk = walk->in_left;
 242                 else
 243                         walk = walk->in_right;
 244         }
 245
 246         RETURN(walk);
 247 }
 248 EXPORT_SYMBOL(interval_find);
 249
 250 static void __rotate_change_maxhigh(struct interval_node *node,
 251                                     struct interval_node *rotate)
 252 {
 253         __u64 left_max, right_max;
 254
 255         rotate->in_max_high = node->in_max_high;
 256         left_max = node->in_left ? node->in_left->in_max_high : 0;
 257         right_max = node->in_right ? node->in_right->in_max_high : 0;
 258         node->in_max_high  = max_u64(interval_high(node),
 259                                      max_u64(left_max,right_max));
 260 }
 261
 262 /* The left rotation "pivots" around the link from node to node->right, and
 263  * - node will be linked to node->right's left child, and
 264  * - node->right's left child will be linked to node's right child.  */
 265 static void __rotate_left(struct interval_node *node,
 266                           struct interval_node **root)
 267 {
 268         struct interval_node *right = node->in_right;
 269         struct interval_node *parent = node->in_parent;
 270
 271         node->in_right = right->in_left;
 272         if (node->in_right)
 273                 right->in_left->in_parent = node;
 274
 275         right->in_left = node;
 276         right->in_parent = parent;
 277         if (parent) {
 278                 if (node_is_left_child(node))
 279                         parent->in_left = right;
 280                 else
 281                         parent->in_right = right;
 282         } else {
 283                 *root = right;
 284         }
 285         node->in_parent = right;
 286
 287         /* update max_high for node and right */
 288         __rotate_change_maxhigh(node, right);
 289 }
 290
 291 /* The right rotation "pivots" around the link from node to node->left, and
 292  * - node will be linked to node->left's right child, and
 293  * - node->left's right child will be linked to node's left child.  */
 294 static void __rotate_right(struct interval_node *node,
 295                            struct interval_node **root)
 296 {
 297         struct interval_node *left = node->in_left;
 298         struct interval_node *parent = node->in_parent;
 299
 300         node->in_left = left->in_right;
 301         if (node->in_left)
 302                 left->in_right->in_parent = node;
 303         left->in_right = node;
 304
 305         left->in_parent = parent;
 306         if (parent) {
 307                 if (node_is_right_child(node))
 308                         parent->in_right = left;
 309                 else
 310                         parent->in_left = left;
 311         } else {
 312                 *root = left;
 313         }
 314         node->in_parent = left;
 315
 316         /* update max_high for node and left */
 317         __rotate_change_maxhigh(node, left);
 318 }
 319
 320 #define interval_swap(a, b) do {                        \
 321         struct interval_node *c = a; a = b; b = c;      \
 322 } while (0)
 323
 324 /*
 325  * Operations INSERT and DELETE, when run on a tree with n keys,
 326  * take O(logN) time.Because they modify the tree, the result
 327  * may violate the red-black properties.To restore these properties,
 328  * we must change the colors of some of the nodes in the tree
 329  * and also change the pointer structure.
 330  */
 331 static void interval_insert_color(struct interval_node *node,
 332                                   struct interval_node **root)
 333 {
 334         struct interval_node *parent, *gparent;
 335         ENTRY;
 336
 337         while ((parent = node->in_parent) && node_is_red(parent)) {
 338                 gparent = parent->in_parent;
 339                 /* Parent is RED, so gparent must not be NULL */
 340                 if (node_is_left_child(parent)) {
 341                         struct interval_node *uncle;
 342                         uncle = gparent->in_right;
 343                         if (uncle && node_is_red(uncle)) {
 344                                 uncle->in_color = INTERVAL_BLACK;
 345                                 parent->in_color = INTERVAL_BLACK;
 346                                 gparent->in_color = INTERVAL_RED;
 347                                 node = gparent;
 348                                 continue;
 349                         }
 350
 351                         if (parent->in_right == node) {
 352                                 __rotate_left(parent, root);
 353                                 interval_swap(node, parent);
 354                         }
 355
 356                         parent->in_color = INTERVAL_BLACK;
 357                         gparent->in_color = INTERVAL_RED;
 358                         __rotate_right(gparent, root);
 359                 } else {
 360                         struct interval_node *uncle;
 361                         uncle = gparent->in_left;
 362                         if (uncle && node_is_red(uncle)) {
 363                                 uncle->in_color = INTERVAL_BLACK;
 364                                 parent->in_color = INTERVAL_BLACK;
 365                                 gparent->in_color = INTERVAL_RED;
 366                                 node = gparent;
 367                                 continue;
 368                         }
 369
 370                         if (node_is_left_child(node)) {
 371                                 __rotate_right(parent, root);
 372                                 interval_swap(node, parent);
 373                         }
 374
 375                         parent->in_color = INTERVAL_BLACK;
 376                         gparent->in_color = INTERVAL_RED;
 377                         __rotate_left(gparent, root);
 378                 }
 379         }
 380
 381         (*root)->in_color = INTERVAL_BLACK;
 382         EXIT;
 383 }
 384
 385 struct interval_node *interval_insert(struct interval_node *node,
 386                                       struct interval_node **root)
 387
 388 {
 389         struct interval_node **p, *parent = NULL;
 390         ENTRY;
 391
 392         LASSERT(!interval_is_intree(node));
 393         p = root;
 394         while (*p) {
 395                 parent = *p;
 396                 if (node_equal(parent, node))
 397                         RETURN(parent);
 398
 399                 /* max_high field must be updated after each iteration */
 400                 if (parent->in_max_high < interval_high(node))
 401                         parent->in_max_high = interval_high(node);
 402
 403                 if (node_compare(node, parent) < 0)
 404                         p = &parent->in_left;
 405                 else
 406                         p = &parent->in_right;
 407         }
 408
 409         /* link node into the tree */
 410         node->in_parent = parent;
 411         node->in_color = INTERVAL_RED;
 412         node->in_left = node->in_right = NULL;
 413         *p = node;
 414
 415         interval_insert_color(node, root);
 416         node->in_intree = 1;
 417
 418         RETURN(NULL);
 419 }
 420 EXPORT_SYMBOL(interval_insert);
 421
 422 static inline int node_is_black_or_0(struct interval_node *node)
 423 {
 424         return !node || node_is_black(node);
 425 }
 426
 427 static void interval_erase_color(struct interval_node *node,
 428                                  struct interval_node *parent,
 429                                  struct interval_node **root)
 430 {
 431         struct interval_node *tmp;
 432         ENTRY;
 433
 434         while (node_is_black_or_0(node) && node != *root) {
 435                 if (parent->in_left == node) {
 436                         tmp = parent->in_right;
 437                         if (node_is_red(tmp)) {
 438                                 tmp->in_color = INTERVAL_BLACK;
 439                                 parent->in_color = INTERVAL_RED;
 440                                 __rotate_left(parent, root);
 441                                 tmp = parent->in_right;
 442                         }
 443                         if (node_is_black_or_0(tmp->in_left) &&
 444                             node_is_black_or_0(tmp->in_right)) {
 445                                 tmp->in_color = INTERVAL_RED;
 446                                 node = parent;
 447                                 parent = node->in_parent;
 448                         } else {
 449                                 if (node_is_black_or_0(tmp->in_right)) {
 450                                         struct interval_node *o_left;
 451                                         if ((o_left = tmp->in_left))
 452                                              o_left->in_color = INTERVAL_BLACK;
 453                                         tmp->in_color = INTERVAL_RED;
 454                                         __rotate_right(tmp, root);
 455                                         tmp = parent->in_right;
 456                                 }
 457                                 tmp->in_color = parent->in_color;
 458                                 parent->in_color = INTERVAL_BLACK;
 459                                 if (tmp->in_right)
 460                                     tmp->in_right->in_color = INTERVAL_BLACK;
 461                                 __rotate_left(parent, root);
 462                                 node = *root;
 463                                 break;
 464                         }
 465                 } else {
 466                         tmp = parent->in_left;
 467                         if (node_is_red(tmp)) {
 468                                 tmp->in_color = INTERVAL_BLACK;
 469                                 parent->in_color = INTERVAL_RED;
 470                                 __rotate_right(parent, root);
 471                                 tmp = parent->in_left;
 472                         }
 473                         if (node_is_black_or_0(tmp->in_left) &&
 474                             node_is_black_or_0(tmp->in_right)) {
 475                                 tmp->in_color = INTERVAL_RED;
 476                                 node = parent;
 477                                 parent = node->in_parent;
 478                         } else {
 479                                 if (node_is_black_or_0(tmp->in_left)) {
 480                                         struct interval_node *o_right;
 481                                         if ((o_right = tmp->in_right))
 482                                             o_right->in_color = INTERVAL_BLACK;
 483                                         tmp->in_color = INTERVAL_RED;
 484                                         __rotate_left(tmp, root);
 485                                         tmp = parent->in_left;
 486                                 }
 487                                 tmp->in_color = parent->in_color;
 488                                 parent->in_color = INTERVAL_BLACK;
 489                                 if (tmp->in_left)
 490                                         tmp->in_left->in_color = INTERVAL_BLACK;
 491                                 __rotate_right(parent, root);
 492                                 node = *root;
 493                                 break;
 494                         }
 495                 }
 496         }
 497         if (node)
 498                 node->in_color = INTERVAL_BLACK;
 499         EXIT;
 500 }
 501
 502 /*
 503  * if the @max_high value of @node is changed, this function traverse  a path
 504  * from node  up to the root to update max_high for the whole tree.
 505  */
 506 static void update_maxhigh(struct interval_node *node,
 507                            __u64  old_maxhigh)
 508 {
 509         __u64 left_max, right_max;
 510         ENTRY;
 511
 512         while (node) {
 513                 left_max = node->in_left ? node->in_left->in_max_high : 0;
 514                 right_max = node->in_right ? node->in_right->in_max_high : 0;
 515                 node->in_max_high = max_u64(interval_high(node),
 516                                             max_u64(left_max, right_max));
 517
 518                 if (node->in_max_high >= old_maxhigh)
 519                         break;
 520                 node = node->in_parent;
 521         }
 522         EXIT;
 523 }
 524
 525 void interval_erase(struct interval_node *node,
 526                     struct interval_node **root)
 527 {
 528         struct interval_node *child, *parent;
 529         int color;
 530         ENTRY;
 531
 532         LASSERT(interval_is_intree(node));
 533         node->in_intree = 0;
 534         if (!node->in_left) {
 535                 child = node->in_right;
 536         } else if (!node->in_right) {
 537                 child = node->in_left;
 538         } else { /* Both left and right child are not NULL */
 539                 struct interval_node *old = node;
 540
 541                 node = interval_next(node);
 542                 child = node->in_right;
 543                 parent = node->in_parent;
 544                 color = node->in_color;
 545
 546                 if (child)
 547                         child->in_parent = parent;
 548                 if (parent == old)
 549                         parent->in_right = child;
 550                 else
 551                         parent->in_left = child;
 552
 553                 node->in_color = old->in_color;
 554                 node->in_right = old->in_right;
 555                 node->in_left = old->in_left;
 556                 node->in_parent = old->in_parent;
 557
 558                 if (old->in_parent) {
 559                         if (node_is_left_child(old))
 560                                 old->in_parent->in_left = node;
 561                         else
 562                                 old->in_parent->in_right = node;
 563                 } else {
 564                         *root = node;
 565                 }
 566
 567                 old->in_left->in_parent = node;
 568                 if (old->in_right)
 569                         old->in_right->in_parent = node;
 570                 update_maxhigh(child ? : parent, node->in_max_high);
 571                 update_maxhigh(node, old->in_max_high);
 572                 if (parent == old)
 573                          parent = node;
 574                 goto color;
 575         }
 576         parent = node->in_parent;
 577         color = node->in_color;
 578
 579         if (child)
 580                 child->in_parent = parent;
 581         if (parent) {
 582                 if (node_is_left_child(node))
 583                         parent->in_left = child;
 584                 else
 585                         parent->in_right = child;
 586         } else {
 587                 *root = child;
 588         }
 589
 590         update_maxhigh(child ? : parent, node->in_max_high);
 591
 592 color:
 593         if (color == INTERVAL_BLACK)
 594                 interval_erase_color(child, parent, root);
 595         EXIT;
 596 }
 597 EXPORT_SYMBOL(interval_erase);
 598
 599 static inline int interval_may_overlap(struct interval_node *node,
 600                                           struct interval_node_extent *ext)
 601 {
 602         return (ext->start <= node->in_max_high &&
 603                 ext->end >= interval_low(node));
 604 }
 605
 606 /*
 607  * This function finds all intervals that overlap interval ext,
 608  * and calls func to handle resulted intervals one by one.
 609  * in lustre, this function will find all conflicting locks in
 610  * the granted queue and add these locks to the ast work list.
 611  *
 612  * {
 613  *       if (node == NULL)
 614  *               return 0;
 615  *       if (ext->end < interval_low(node)) {
 616  *               interval_search(node->in_left, ext, func, data);
 617  *       } else if (interval_may_overlap(node, ext)) {
 618  *               if (extent_overlapped(ext, &node->in_extent))
 619  *                       func(node, data);
 620  *               interval_search(node->in_left, ext, func, data);
 621  *               interval_search(node->in_right, ext, func, data);
 622  *       }
 623  *       return 0;
 624  * }
 625  *
 626  */
 627 enum interval_iter interval_search(struct interval_node *node,
 628                                    struct interval_node_extent *ext,
 629                                    interval_callback_t func,
 630                                    void *data)
 631 {
 632         struct interval_node *parent;
 633         enum interval_iter rc = INTERVAL_ITER_CONT;
 634
 635         LASSERT(ext != NULL);
 636         LASSERT(func != NULL);
 637
 638         while (node) {
 639                 if (ext->end < interval_low(node)) {
 640                         if (node->in_left) {
 641                                 node = node->in_left;
 642                                 continue;
 643                         }
 644                 } else if (interval_may_overlap(node, ext)) {
 645                         if (extent_overlapped(ext, &node->in_extent)) {
 646                                 rc = func(node, data);
 647                                 if (rc == INTERVAL_ITER_STOP)
 648                                         break;
 649                         }
 650
 651                         if (node->in_left) {
 652                                 node = node->in_left;
 653                                 continue;
 654                         }
 655                         if (node->in_right) {
 656                                 node = node->in_right;
 657                                 continue;
 658                         }
 659                 }
 660
 661                 parent = node->in_parent;
 662                 while (parent) {
 663                         if (node_is_left_child(node) &&
 664                             parent->in_right) {
 665                                 /* If we ever got the left, it means that the
 666                                  * parent met ext->end<interval_low(parent), or
 667                                  * may_overlap(parent). If the former is true,
 668                                  * we needn't go back. So stop early and check
 669                                  * may_overlap(parent) after this loop.  */
 670                                 node = parent->in_right;
 671                                 break;
 672                         }
 673                         node = parent;
 674                         parent = parent->in_parent;
 675                 }
 676                 if (parent == NULL || !interval_may_overlap(parent, ext))
 677                         break;
 678         }
 679
 680         return rc;
 681 }
 682 EXPORT_SYMBOL(interval_search);
 683
 684 enum interval_iter interval_search_expand_extent( struct interval_node *node,
 685                                        struct interval_node_extent *ext,
 686                                        struct interval_node_extent *result_ext,
 687                                        interval_callback_t func, void *data)
 688 {
 689         struct interval_node *parent;
 690         enum interval_iter rc = INTERVAL_ITER_CONT;
 691
 692         LASSERT(ext != NULL);
 693         LASSERT(func != NULL);
 694
 695         while (node) {
 696                 if (ext->end < interval_low(node)) {
 697                         if (result_ext->end > interval_low(node) - 1)
 698                                 result_ext->end = interval_low(node) - 1;
 699                         if (node->in_left) {
 700                                 node = node->in_left;
 701                                 continue;
 702                         }
 703                 } else if (ext->start > node->in_max_high) {
 704                         if (result_ext->start < node->in_max_high + 1)
 705                                 result_ext->start = node->in_max_high + 1;
 706                 } else {
 707                         if (extent_overlapped(ext, &node->in_extent)) {
 708                                 rc = func(node, data);
 709                                 if (rc == INTERVAL_ITER_STOP)
 710                                         break;
 711                         }
 712
 713                         if (node->in_left) {
 714                                 node = node->in_left;
 715                                 continue;
 716                         }
 717                         if (node->in_right) {
 718                                 node = node->in_right;
 719                                 continue;
 720                         }
 721                 }
 722
 723                 parent = node->in_parent;
 724                 while (parent) {
 725                         if (node_is_left_child(node) && parent->in_right) {
 726                                 node = parent->in_right;
 727                                 break;
 728                         }
 729                         node = parent;
 730                         parent = node->in_parent;
 731                 }
 732                 if (parent == NULL)
 733                         break;
 734         }
 735         return rc;
 736 }
 737
 738 static enum interval_iter interval_overlap_cb(struct interval_node *n,
 739                                               void *args)
 740 {
 741         *(int *)args = 1;
 742         return INTERVAL_ITER_STOP;
 743 }
 744
 745 int interval_is_overlapped(struct interval_node *root,
 746                            struct interval_node_extent *ext)
 747 {
 748         int has = 0;
 749         (void)interval_search(root, ext, interval_overlap_cb, &has);
 750         return has;
 751 }
 752 EXPORT_SYMBOL(interval_is_overlapped);
 753
 754 /* Don't expand to low. Expanding downwards is expensive, and meaningless to
 755  * some extents, because programs seldom do IO backward.
 756  *
 757  * The recursive algorithm of expanding low:
 758  * expand_low {
 759  *        struct interval_node *tmp;
 760  *        static __u64 res = 0;
 761  *
 762  *        if (root == NULL)
 763  *                return res;
 764  *        if (root->in_max_high < low) {
 765  *                res = max_u64(root->in_max_high + 1, res);
 766  *                return res;
 767  *        } else if (low < interval_low(root)) {
 768  *                interval_expand_low(root->in_left, low);
 769  *                return res;
 770  *        }
 771  *
 772  *        if (interval_high(root) < low)
 773  *                res = max_u64(interval_high(root) + 1, res);
 774  *        interval_expand_low(root->in_left, low);
 775  *        interval_expand_low(root->in_right, low);
 776  *
 777  *        return res;
 778  * }
 779  *
 780  * It's much easy to eliminate the recursion, see interval_search for
 781  * an example. -jay
 782  */
 783 static inline __u64 interval_expand_low(struct interval_node *root, __u64 low)
 784 {
 785         /* we only concern the empty tree right now. */
 786         if (root == NULL)
 787                 return 0;
 788         return low;
 789 }
 790
 791 static inline __u64 interval_expand_high(struct interval_node *node, __u64 high)
 792 {
 793         __u64 result = ~0;
 794
 795         while (node != NULL) {
 796                 if (node->in_max_high < high)
 797                         break;
 798
 799                 if (interval_low(node) > high) {
 800                         result = interval_low(node) - 1;
 801                         node = node->in_left;
 802                 } else {
 803                         node = node->in_right;
 804                 }
 805         }
 806
 807         return result;
 808 }
 809
 810 /* expanding the extent based on @ext. */
 811 void interval_expand(struct interval_node *root,
 812                      struct interval_node_extent *ext,
 813                      struct interval_node_extent *limiter)
 814 {
 815         /* The assertion of interval_is_overlapped is expensive because we may
 816          * travel many nodes to find the overlapped node. */
 817         LASSERT(interval_is_overlapped(root, ext) == 0);
 818         if (!limiter || limiter->start < ext->start)
 819                 ext->start = interval_expand_low(root, ext->start);
 820         if (!limiter || limiter->end > ext->end)
 821                 ext->end = interval_expand_high(root, ext->end);
 822         LASSERT(interval_is_overlapped(root, ext) == 0);
 823 }
 824 EXPORT_SYMBOL(interval_expand);