lib/btree.c

   1 /*
   2  * lib/btree.c  - Simple In-memory B+Tree
   3  *
   4  * As should be obvious for Linux kernel code, license is GPLv2
   5  *
   6  * Copyright (c) 2007-2008 Joern Engel <joern@logfs.org>
   7  * Bits and pieces stolen from Peter Zijlstra's code, which is
   8  * Copyright 2007, Red Hat Inc. Peter Zijlstra <pzijlstr@redhat.com>
   9  * GPLv2
  10  *
  11  * see http://programming.kicks-ass.net/kernel-patches/vma_lookup/btree.patch
  12  *
  13  * A relatively simple B+Tree implementation.  I have written it as a learning
  14  * exercise to understand how B+Trees work.  Turned out to be useful as well.
  15  *
  16  * B+Trees can be used similar to Linux radix trees (which don't have anything
  17  * in common with textbook radix trees, beware).  Prerequisite for them working
  18  * well is that access to a random tree node is much faster than a large number
  19  * of operations within each node.
  20  *
  21  * Disks have fulfilled the prerequisite for a long time.  More recently DRAM
  22  * has gained similar properties, as memory access times, when measured in cpu
  23  * cycles, have increased.  Cacheline sizes have increased as well, which also
  24  * helps B+Trees.
  25  *
  26  * Compared to radix trees, B+Trees are more efficient when dealing with a
  27  * sparsely populated address space.  Between 25% and 50% of the memory is
  28  * occupied with valid pointers.  When densely populated, radix trees contain
  29  * ~98% pointers - hard to beat.  Very sparse radix trees contain only ~2%
  30  * pointers.
  31  *
  32  * This particular implementation stores pointers identified by a long value.
  33  * Storing NULL pointers is illegal, lookup will return NULL when no entry
  34  * was found.
  35  *
  36  * A tricks was used that is not commonly found in textbooks.  The lowest
  37  * values are to the right, not to the left.  All used slots within a node
  38  * are on the left, all unused slots contain NUL values.  Most operations
  39  * simply loop once over all slots and terminate on the first NUL.
  40  */
  41
  42 #include <linux/btree.h>
  43 #include <linux/cache.h>
  44 #include <linux/kernel.h>
  45 #include <linux/slab.h>
  46 #include <linux/module.h>
  47
  48 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  49 #define NODESIZE MAX(L1_CACHE_BYTES, 128)
  50
  51 struct btree_geo {
  52         int keylen;
  53         int no_pairs;
  54         int no_longs;
  55 };
  56
  57 struct btree_geo btree_geo32 = {
  58         .keylen = 1,
  59         .no_pairs = NODESIZE / sizeof(long) / 2,
  60         .no_longs = NODESIZE / sizeof(long) / 2,
  61 };
  62 EXPORT_SYMBOL_GPL(btree_geo32);
  63
  64 #define LONG_PER_U64 (64 / BITS_PER_LONG)
  65 struct btree_geo btree_geo64 = {
  66         .keylen = LONG_PER_U64,
  67         .no_pairs = NODESIZE / sizeof(long) / (1 + LONG_PER_U64),
  68         .no_longs = LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + LONG_PER_U64)),
  69 };
  70 EXPORT_SYMBOL_GPL(btree_geo64);
  71
  72 struct btree_geo btree_geo128 = {
  73         .keylen = 2 * LONG_PER_U64,
  74         .no_pairs = NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64),
  75         .no_longs = 2 * LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64)),
  76 };
  77 EXPORT_SYMBOL_GPL(btree_geo128);
  78
  79 static struct kmem_cache *btree_cachep;
  80
  81 void *btree_alloc(gfp_t gfp_mask, void *pool_data)
  82 {
  83         return kmem_cache_alloc(btree_cachep, gfp_mask);
  84 }
  85 EXPORT_SYMBOL_GPL(btree_alloc);
  86
  87 void btree_free(void *element, void *pool_data)
  88 {
  89         kmem_cache_free(btree_cachep, element);
  90 }
  91 EXPORT_SYMBOL_GPL(btree_free);
  92
  93 static unsigned long *btree_node_alloc(struct btree_head *head, gfp_t gfp)
  94 {
  95         unsigned long *node;
  96
  97         node = mempool_alloc(head->mempool, gfp);
  98         if (likely(node))
  99                 memset(node, 0, NODESIZE);
 100         return node;
 101 }
 102
 103 static int longcmp(const unsigned long *l1, const unsigned long *l2, size_t n)
 104 {
 105         size_t i;
 106
 107         for (i = 0; i < n; i++) {
 108                 if (l1[i] < l2[i])
 109                         return -1;
 110                 if (l1[i] > l2[i])
 111                         return 1;
 112         }
 113         return 0;
 114 }
 115
 116 static unsigned long *longcpy(unsigned long *dest, const unsigned long *src,
 117                 size_t n)
 118 {
 119         size_t i;
 120
 121         for (i = 0; i < n; i++)
 122                 dest[i] = src[i];
 123         return dest;
 124 }
 125
 126 static unsigned long *longset(unsigned long *s, unsigned long c, size_t n)
 127 {
 128         size_t i;
 129
 130         for (i = 0; i < n; i++)
 131                 s[i] = c;
 132         return s;
 133 }
 134
 135 static void dec_key(struct btree_geo *geo, unsigned long *key)
 136 {
 137         unsigned long val;
 138         int i;
 139
 140         for (i = geo->keylen - 1; i >= 0; i--) {
 141                 val = key[i];
 142                 key[i] = val - 1;
 143                 if (val)
 144                         break;
 145         }
 146 }
 147
 148 static unsigned long *bkey(struct btree_geo *geo, unsigned long *node, int n)
 149 {
 150         return &node[n * geo->keylen];
 151 }
 152
 153 static void *bval(struct btree_geo *geo, unsigned long *node, int n)
 154 {
 155         return (void *)node[geo->no_longs + n];
 156 }
 157
 158 static void setkey(struct btree_geo *geo, unsigned long *node, int n,
 159                    unsigned long *key)
 160 {
 161         longcpy(bkey(geo, node, n), key, geo->keylen);
 162 }
 163
 164 static void setval(struct btree_geo *geo, unsigned long *node, int n,
 165                    void *val)
 166 {
 167         node[geo->no_longs + n] = (unsigned long) val;
 168 }
 169
 170 static void clearpair(struct btree_geo *geo, unsigned long *node, int n)
 171 {
 172         longset(bkey(geo, node, n), 0, geo->keylen);
 173         node[geo->no_longs + n] = 0;
 174 }
 175
 176 static inline void __btree_init(struct btree_head *head)
 177 {
 178         head->node = NULL;
 179         head->height = 0;
 180 }
 181
 182 void btree_init_mempool(struct btree_head *head, mempool_t *mempool)
 183 {
 184         __btree_init(head);
 185         head->mempool = mempool;
 186 }
 187 EXPORT_SYMBOL_GPL(btree_init_mempool);
 188
 189 int btree_init(struct btree_head *head)
 190 {
 191         __btree_init(head);
 192         head->mempool = mempool_create(0, btree_alloc, btree_free, NULL);
 193         if (!head->mempool)
 194                 return -ENOMEM;
 195         return 0;
 196 }
 197 EXPORT_SYMBOL_GPL(btree_init);
 198
 199 void btree_destroy(struct btree_head *head)
 200 {
 201         mempool_destroy(head->mempool);
 202         head->mempool = NULL;
 203 }
 204 EXPORT_SYMBOL_GPL(btree_destroy);
 205
 206 void *btree_last(struct btree_head *head, struct btree_geo *geo,
 207                  unsigned long *key)
 208 {
 209         int height = head->height;
 210         unsigned long *node = head->node;
 211
 212         if (height == 0)
 213                 return NULL;
 214
 215         for ( ; height > 1; height--)
 216                 node = bval(geo, node, 0);
 217
 218         longcpy(key, bkey(geo, node, 0), geo->keylen);
 219         return bval(geo, node, 0);
 220 }
 221 EXPORT_SYMBOL_GPL(btree_last);
 222
 223 static int keycmp(struct btree_geo *geo, unsigned long *node, int pos,
 224                   unsigned long *key)
 225 {
 226         return longcmp(bkey(geo, node, pos), key, geo->keylen);
 227 }
 228
 229 static int keyzero(struct btree_geo *geo, unsigned long *key)
 230 {
 231         int i;
 232
 233         for (i = 0; i < geo->keylen; i++)
 234                 if (key[i])
 235                         return 0;
 236
 237         return 1;
 238 }
 239
 240 void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
 241                 unsigned long *key)
 242 {
 243         int i, height = head->height;
 244         unsigned long *node = head->node;
 245
 246         if (height == 0)
 247                 return NULL;
 248
 249         for ( ; height > 1; height--) {
 250                 for (i = 0; i < geo->no_pairs; i++)
 251                         if (keycmp(geo, node, i, key) <= 0)
 252                                 break;
 253                 if (i == geo->no_pairs)
 254                         return NULL;
 255                 node = bval(geo, node, i);
 256                 if (!node)
 257                         return NULL;
 258         }
 259
 260         if (!node)
 261                 return NULL;
 262
 263         for (i = 0; i < geo->no_pairs; i++)
 264                 if (keycmp(geo, node, i, key) == 0)
 265                         return bval(geo, node, i);
 266         return NULL;
 267 }
 268 EXPORT_SYMBOL_GPL(btree_lookup);
 269
 270 int btree_update(struct btree_head *head, struct btree_geo *geo,
 271                  unsigned long *key, void *val)
 272 {
 273         int i, height = head->height;
 274         unsigned long *node = head->node;
 275
 276         if (height == 0)
 277                 return -ENOENT;
 278
 279         for ( ; height > 1; height--) {
 280                 for (i = 0; i < geo->no_pairs; i++)
 281                         if (keycmp(geo, node, i, key) <= 0)
 282                                 break;
 283                 if (i == geo->no_pairs)
 284                         return -ENOENT;
 285                 node = bval(geo, node, i);
 286                 if (!node)
 287                         return -ENOENT;
 288         }
 289
 290         if (!node)
 291                 return -ENOENT;
 292
 293         for (i = 0; i < geo->no_pairs; i++)
 294                 if (keycmp(geo, node, i, key) == 0) {
 295                         setval(geo, node, i, val);
 296                         return 0;
 297                 }
 298         return -ENOENT;
 299 }
 300 EXPORT_SYMBOL_GPL(btree_update);
 301
 302 /*
 303  * Usually this function is quite similar to normal lookup.  But the key of
 304  * a parent node may be smaller than the smallest key of all its siblings.
 305  * In such a case we cannot just return NULL, as we have only proven that no
 306  * key smaller than __key, but larger than this parent key exists.
 307  * So we set __key to the parent key and retry.  We have to use the smallest
 308  * such parent key, which is the last parent key we encountered.
 309  */
 310 void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
 311                      unsigned long *__key)
 312 {
 313         int i, height;
 314         unsigned long *node, *oldnode;
 315         unsigned long *retry_key = NULL, key[geo->keylen];
 316
 317         if (keyzero(geo, __key))
 318                 return NULL;
 319
 320         if (head->height == 0)
 321                 return NULL;
 322 retry:
 323         longcpy(key, __key, geo->keylen);
 324         dec_key(geo, key);
 325
 326         node = head->node;
 327         for (height = head->height ; height > 1; height--) {
 328                 for (i = 0; i < geo->no_pairs; i++)
 329                         if (keycmp(geo, node, i, key) <= 0)
 330                                 break;
 331                 if (i == geo->no_pairs)
 332                         goto miss;
 333                 oldnode = node;
 334                 node = bval(geo, node, i);
 335                 if (!node)
 336                         goto miss;
 337                 retry_key = bkey(geo, oldnode, i);
 338         }
 339
 340         if (!node)
 341                 goto miss;
 342
 343         for (i = 0; i < geo->no_pairs; i++) {
 344                 if (keycmp(geo, node, i, key) <= 0) {
 345                         if (bval(geo, node, i)) {
 346                                 longcpy(__key, bkey(geo, node, i), geo->keylen);
 347                                 return bval(geo, node, i);
 348                         } else
 349                                 goto miss;
 350                 }
 351         }
 352 miss:
 353         if (retry_key) {
 354                 __key = retry_key;
 355                 retry_key = NULL;
 356                 goto retry;
 357         }
 358         return NULL;
 359 }
 360 EXPORT_SYMBOL_GPL(btree_get_prev);
 361
 362 static int getpos(struct btree_geo *geo, unsigned long *node,
 363                 unsigned long *key)
 364 {
 365         int i;
 366
 367         for (i = 0; i < geo->no_pairs; i++) {
 368                 if (keycmp(geo, node, i, key) <= 0)
 369                         break;
 370         }
 371         return i;
 372 }
 373
 374 static int getfill(struct btree_geo *geo, unsigned long *node, int start)
 375 {
 376         int i;
 377
 378         for (i = start; i < geo->no_pairs; i++)
 379                 if (!bval(geo, node, i))
 380                         break;
 381         return i;
 382 }
 383
 384 /*
 385  * locate the correct leaf node in the btree
 386  */
 387 static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
 388                 unsigned long *key, int level)
 389 {
 390         unsigned long *node = head->node;
 391         int i, height;
 392
 393         for (height = head->height; height > level; height--) {
 394                 for (i = 0; i < geo->no_pairs; i++)
 395                         if (keycmp(geo, node, i, key) <= 0)
 396                                 break;
 397
 398                 if ((i == geo->no_pairs) || !bval(geo, node, i)) {
 399                         /* right-most key is too large, update it */
 400                         /* FIXME: If the right-most key on higher levels is
 401                          * always zero, this wouldn't be necessary. */
 402                         i--;
 403                         setkey(geo, node, i, key);
 404                 }
 405                 BUG_ON(i < 0);
 406                 node = bval(geo, node, i);
 407         }
 408         BUG_ON(!node);
 409         return node;
 410 }
 411
 412 static int btree_grow(struct btree_head *head, struct btree_geo *geo,
 413                       gfp_t gfp)
 414 {
 415         unsigned long *node;
 416         int fill;
 417
 418         node = btree_node_alloc(head, gfp);
 419         if (!node)
 420                 return -ENOMEM;
 421         if (head->node) {
 422                 fill = getfill(geo, head->node, 0);
 423                 setkey(geo, node, 0, bkey(geo, head->node, fill - 1));
 424                 setval(geo, node, 0, head->node);
 425         }
 426         head->node = node;
 427         head->height++;
 428         return 0;
 429 }
 430
 431 static void btree_shrink(struct btree_head *head, struct btree_geo *geo)
 432 {
 433         unsigned long *node;
 434         int fill;
 435
 436         if (head->height <= 1)
 437                 return;
 438
 439         node = head->node;
 440         fill = getfill(geo, node, 0);
 441         BUG_ON(fill > 1);
 442         head->node = bval(geo, node, 0);
 443         head->height--;
 444         mempool_free(node, head->mempool);
 445 }
 446
 447 static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
 448                               unsigned long *key, void *val, int level,
 449                               gfp_t gfp)
 450 {
 451         unsigned long *node;
 452         int i, pos, fill, err;
 453
 454         BUG_ON(!val);
 455         if (head->height < level) {
 456                 err = btree_grow(head, geo, gfp);
 457                 if (err)
 458                         return err;
 459         }
 460
 461 retry:
 462         node = find_level(head, geo, key, level);
 463         pos = getpos(geo, node, key);
 464         fill = getfill(geo, node, pos);
 465         /* two identical keys are not allowed */
 466         BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);
 467
 468         if (fill == geo->no_pairs) {
 469                 /* need to split node */
 470                 unsigned long *new;
 471
 472                 new = btree_node_alloc(head, gfp);
 473                 if (!new)
 474                         return -ENOMEM;
 475                 err = btree_insert_level(head, geo,
 476                                 bkey(geo, node, fill / 2 - 1),
 477                                 new, level + 1, gfp);
 478                 if (err) {
 479                         mempool_free(new, head->mempool);
 480                         return err;
 481                 }
 482                 for (i = 0; i < fill / 2; i++) {
 483                         setkey(geo, new, i, bkey(geo, node, i));
 484                         setval(geo, new, i, bval(geo, node, i));
 485                         setkey(geo, node, i, bkey(geo, node, i + fill / 2));
 486                         setval(geo, node, i, bval(geo, node, i + fill / 2));
 487                         clearpair(geo, node, i + fill / 2);
 488                 }
 489                 if (fill & 1) {
 490                         setkey(geo, node, i, bkey(geo, node, fill - 1));
 491                         setval(geo, node, i, bval(geo, node, fill - 1));
 492                         clearpair(geo, node, fill - 1);
 493                 }
 494                 goto retry;
 495         }
 496         BUG_ON(fill >= geo->no_pairs);
 497
 498         /* shift and insert */
 499         for (i = fill; i > pos; i--) {
 500                 setkey(geo, node, i, bkey(geo, node, i - 1));
 501                 setval(geo, node, i, bval(geo, node, i - 1));
 502         }
 503         setkey(geo, node, pos, key);
 504         setval(geo, node, pos, val);
 505
 506         return 0;
 507 }
 508
 509 int btree_insert(struct btree_head *head, struct btree_geo *geo,
 510                 unsigned long *key, void *val, gfp_t gfp)
 511 {
 512         return btree_insert_level(head, geo, key, val, 1, gfp);
 513 }
 514 EXPORT_SYMBOL_GPL(btree_insert);
 515
 516 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 517                 unsigned long *key, int level);
 518 static void merge(struct btree_head *head, struct btree_geo *geo, int level,
 519                 unsigned long *left, int lfill,
 520                 unsigned long *right, int rfill,
 521                 unsigned long *parent, int lpos)
 522 {
 523         int i;
 524
 525         for (i = 0; i < rfill; i++) {
 526                 /* Move all keys to the left */
 527                 setkey(geo, left, lfill + i, bkey(geo, right, i));
 528                 setval(geo, left, lfill + i, bval(geo, right, i));
 529         }
 530         /* Exchange left and right child in parent */
 531         setval(geo, parent, lpos, right);
 532         setval(geo, parent, lpos + 1, left);
 533         /* Remove left (formerly right) child from parent */
 534         btree_remove_level(head, geo, bkey(geo, parent, lpos), level + 1);
 535         mempool_free(right, head->mempool);
 536 }
 537
 538 static void rebalance(struct btree_head *head, struct btree_geo *geo,
 539                 unsigned long *key, int level, unsigned long *child, int fill)
 540 {
 541         unsigned long *parent, *left = NULL, *right = NULL;
 542         int i, no_left, no_right;
 543
 544         if (fill == 0) {
 545                 /* Because we don't steal entries from a neighbour, this case
 546                  * can happen.  Parent node contains a single child, this
 547                  * node, so merging with a sibling never happens.
 548                  */
 549                 btree_remove_level(head, geo, key, level + 1);
 550                 mempool_free(child, head->mempool);
 551                 return;
 552         }
 553
 554         parent = find_level(head, geo, key, level + 1);
 555         i = getpos(geo, parent, key);
 556         BUG_ON(bval(geo, parent, i) != child);
 557
 558         if (i > 0) {
 559                 left = bval(geo, parent, i - 1);
 560                 no_left = getfill(geo, left, 0);
 561                 if (fill + no_left <= geo->no_pairs) {
 562                         merge(head, geo, level,
 563                                         left, no_left,
 564                                         child, fill,
 565                                         parent, i - 1);
 566                         return;
 567                 }
 568         }
 569         if (i + 1 < getfill(geo, parent, i)) {
 570                 right = bval(geo, parent, i + 1);
 571                 no_right = getfill(geo, right, 0);
 572                 if (fill + no_right <= geo->no_pairs) {
 573                         merge(head, geo, level,
 574                                         child, fill,
 575                                         right, no_right,
 576                                         parent, i);
 577                         return;
 578                 }
 579         }
 580         /*
 581          * We could also try to steal one entry from the left or right
 582          * neighbor.  By not doing so we changed the invariant from
 583          * "all nodes are at least half full" to "no two neighboring
 584          * nodes can be merged".  Which means that the average fill of
 585          * all nodes is still half or better.
 586          */
 587 }
 588
 589 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 590                 unsigned long *key, int level)
 591 {
 592         unsigned long *node;
 593         int i, pos, fill;
 594         void *ret;
 595
 596         if (level > head->height) {
 597                 /* we recursed all the way up */
 598                 head->height = 0;
 599                 head->node = NULL;
 600                 return NULL;
 601         }
 602
 603         node = find_level(head, geo, key, level);
 604         pos = getpos(geo, node, key);
 605         fill = getfill(geo, node, pos);
 606         if ((level == 1) && (keycmp(geo, node, pos, key) != 0))
 607                 return NULL;
 608         ret = bval(geo, node, pos);
 609
 610         /* remove and shift */
 611         for (i = pos; i < fill - 1; i++) {
 612                 setkey(geo, node, i, bkey(geo, node, i + 1));
 613                 setval(geo, node, i, bval(geo, node, i + 1));
 614         }
 615         clearpair(geo, node, fill - 1);
 616
 617         if (fill - 1 < geo->no_pairs / 2) {
 618                 if (level < head->height)
 619                         rebalance(head, geo, key, level, node, fill - 1);
 620                 else if (fill - 1 == 1)
 621                         btree_shrink(head, geo);
 622         }
 623
 624         return ret;
 625 }
 626
 627 void *btree_remove(struct btree_head *head, struct btree_geo *geo,
 628                 unsigned long *key)
 629 {
 630         if (head->height == 0)
 631                 return NULL;
 632
 633         return btree_remove_level(head, geo, key, 1);
 634 }
 635 EXPORT_SYMBOL_GPL(btree_remove);
 636
 637 int btree_merge(struct btree_head *target, struct btree_head *victim,
 638                 struct btree_geo *geo, gfp_t gfp)
 639 {
 640         unsigned long key[geo->keylen];
 641         unsigned long dup[geo->keylen];
 642         void *val;
 643         int err;
 644
 645         BUG_ON(target == victim);
 646
 647         if (!(target->node)) {
 648                 /* target is empty, just copy fields over */
 649                 target->node = victim->node;
 650                 target->height = victim->height;
 651                 __btree_init(victim);
 652                 return 0;
 653         }
 654
 655         /* TODO: This needs some optimizations.  Currently we do three tree
 656          * walks to remove a single object from the victim.
 657          */
 658         for (;;) {
 659                 if (!btree_last(victim, geo, key))
 660                         break;
 661                 val = btree_lookup(victim, geo, key);
 662                 err = btree_insert(target, geo, key, val, gfp);
 663                 if (err)
 664                         return err;
 665                 /* We must make a copy of the key, as the original will get
 666                  * mangled inside btree_remove. */
 667                 longcpy(dup, key, geo->keylen);
 668                 btree_remove(victim, geo, dup);
 669         }
 670         return 0;
 671 }
 672 EXPORT_SYMBOL_GPL(btree_merge);
 673
 674 static size_t __btree_for_each(struct btree_head *head, struct btree_geo *geo,
 675                                unsigned long *node, unsigned long opaque,
 676                                void (*func)(void *elem, unsigned long opaque,
 677                                             unsigned long *key, size_t index,
 678                                             void *func2),
 679                                void *func2, int reap, int height, size_t count)
 680 {
 681         int i;
 682         unsigned long *child;
 683
 684         for (i = 0; i < geo->no_pairs; i++) {
 685                 child = bval(geo, node, i);
 686                 if (!child)
 687                         break;
 688                 if (height > 1)
 689                         count = __btree_for_each(head, geo, child, opaque,
 690                                         func, func2, reap, height - 1, count);
 691                 else
 692                         func(child, opaque, bkey(geo, node, i), count++,
 693                                         func2);
 694         }
 695         if (reap)
 696                 mempool_free(node, head->mempool);
 697         return count;
 698 }
 699
 700 static void empty(void *elem, unsigned long opaque, unsigned long *key,
 701                   size_t index, void *func2)
 702 {
 703 }
 704
 705 void visitorl(void *elem, unsigned long opaque, unsigned long *key,
 706               size_t index, void *__func)
 707 {
 708         visitorl_t func = __func;
 709
 710         func(elem, opaque, *key, index);
 711 }
 712 EXPORT_SYMBOL_GPL(visitorl);
 713
 714 void visitor32(void *elem, unsigned long opaque, unsigned long *__key,
 715                size_t index, void *__func)
 716 {
 717         visitor32_t func = __func;
 718         u32 *key = (void *)__key;
 719
 720         func(elem, opaque, *key, index);
 721 }
 722 EXPORT_SYMBOL_GPL(visitor32);
 723
 724 void visitor64(void *elem, unsigned long opaque, unsigned long *__key,
 725                size_t index, void *__func)
 726 {
 727         visitor64_t func = __func;
 728         u64 *key = (void *)__key;
 729
 730         func(elem, opaque, *key, index);
 731 }
 732 EXPORT_SYMBOL_GPL(visitor64);
 733
 734 void visitor128(void *elem, unsigned long opaque, unsigned long *__key,
 735                 size_t index, void *__func)
 736 {
 737         visitor128_t func = __func;
 738         u64 *key = (void *)__key;
 739
 740         func(elem, opaque, key[0], key[1], index);
 741 }
 742 EXPORT_SYMBOL_GPL(visitor128);
 743
 744 size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
 745                      unsigned long opaque,
 746                      void (*func)(void *elem, unsigned long opaque,
 747                                   unsigned long *key,
 748                                   size_t index, void *func2),
 749                      void *func2)
 750 {
 751         size_t count = 0;
 752
 753         if (!func2)
 754                 func = empty;
 755         if (head->node)
 756                 count = __btree_for_each(head, geo, head->node, opaque, func,
 757                                 func2, 0, head->height, 0);
 758         return count;
 759 }
 760 EXPORT_SYMBOL_GPL(btree_visitor);
 761
 762 size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
 763                           unsigned long opaque,
 764                           void (*func)(void *elem, unsigned long opaque,
 765                                        unsigned long *key,
 766                                        size_t index, void *func2),
 767                           void *func2)
 768 {
 769         size_t count = 0;
 770
 771         if (!func2)
 772                 func = empty;
 773         if (head->node)
 774                 count = __btree_for_each(head, geo, head->node, opaque, func,
 775                                 func2, 1, head->height, 0);
 776         __btree_init(head);
 777         return count;
 778 }
 779 EXPORT_SYMBOL_GPL(btree_grim_visitor);
 780
 781 static int __init btree_module_init(void)
 782 {
 783         btree_cachep = kmem_cache_create("btree_node", NODESIZE, 0,
 784                         SLAB_HWCACHE_ALIGN, NULL);
 785         return 0;
 786 }
 787
 788 static void __exit btree_module_exit(void)
 789 {
 790         kmem_cache_destroy(btree_cachep);
 791 }
 792
 793 /* If core code starts using btree, initialization should happen even earlier */
 794 module_init(btree_module_init);
 795 module_exit(btree_module_exit);
 796
 797 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 798 MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
 799 MODULE_LICENSE("GPL");