release/src-rt-6.x.4708/linux/linux-2.6.36/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  * excercise 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
 361 static int getpos(struct btree_geo *geo, unsigned long *node,
 362                 unsigned long *key)
 363 {
 364         int i;
 365
 366         for (i = 0; i < geo->no_pairs; i++) {
 367                 if (keycmp(geo, node, i, key) <= 0)
 368                         break;
 369         }
 370         return i;
 371 }
 372
 373 static int getfill(struct btree_geo *geo, unsigned long *node, int start)
 374 {
 375         int i;
 376
 377         for (i = start; i < geo->no_pairs; i++)
 378                 if (!bval(geo, node, i))
 379                         break;
 380         return i;
 381 }
 382
 383 /*
 384  * locate the correct leaf node in the btree
 385  */
 386 static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
 387                 unsigned long *key, int level)
 388 {
 389         unsigned long *node = head->node;
 390         int i, height;
 391
 392         for (height = head->height; height > level; height--) {
 393                 for (i = 0; i < geo->no_pairs; i++)
 394                         if (keycmp(geo, node, i, key) <= 0)
 395                                 break;
 396
 397                 if ((i == geo->no_pairs) || !bval(geo, node, i)) {
 398                         /* right-most key is too large, update it */
 399                         i--;
 400                         setkey(geo, node, i, key);
 401                 }
 402                 BUG_ON(i < 0);
 403                 node = bval(geo, node, i);
 404         }
 405         BUG_ON(!node);
 406         return node;
 407 }
 408
 409 static int btree_grow(struct btree_head *head, struct btree_geo *geo,
 410                       gfp_t gfp)
 411 {
 412         unsigned long *node;
 413         int fill;
 414
 415         node = btree_node_alloc(head, gfp);
 416         if (!node)
 417                 return -ENOMEM;
 418         if (head->node) {
 419                 fill = getfill(geo, head->node, 0);
 420                 setkey(geo, node, 0, bkey(geo, head->node, fill - 1));
 421                 setval(geo, node, 0, head->node);
 422         }
 423         head->node = node;
 424         head->height++;
 425         return 0;
 426 }
 427
 428 static void btree_shrink(struct btree_head *head, struct btree_geo *geo)
 429 {
 430         unsigned long *node;
 431         int fill;
 432
 433         if (head->height <= 1)
 434                 return;
 435
 436         node = head->node;
 437         fill = getfill(geo, node, 0);
 438         BUG_ON(fill > 1);
 439         head->node = bval(geo, node, 0);
 440         head->height--;
 441         mempool_free(node, head->mempool);
 442 }
 443
 444 static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
 445                               unsigned long *key, void *val, int level,
 446                               gfp_t gfp)
 447 {
 448         unsigned long *node;
 449         int i, pos, fill, err;
 450
 451         BUG_ON(!val);
 452         if (head->height < level) {
 453                 err = btree_grow(head, geo, gfp);
 454                 if (err)
 455                         return err;
 456         }
 457
 458 retry:
 459         node = find_level(head, geo, key, level);
 460         pos = getpos(geo, node, key);
 461         fill = getfill(geo, node, pos);
 462         /* two identical keys are not allowed */
 463         BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);
 464
 465         if (fill == geo->no_pairs) {
 466                 /* need to split node */
 467                 unsigned long *new;
 468
 469                 new = btree_node_alloc(head, gfp);
 470                 if (!new)
 471                         return -ENOMEM;
 472                 err = btree_insert_level(head, geo,
 473                                 bkey(geo, node, fill / 2 - 1),
 474                                 new, level + 1, gfp);
 475                 if (err) {
 476                         mempool_free(new, head->mempool);
 477                         return err;
 478                 }
 479                 for (i = 0; i < fill / 2; i++) {
 480                         setkey(geo, new, i, bkey(geo, node, i));
 481                         setval(geo, new, i, bval(geo, node, i));
 482                         setkey(geo, node, i, bkey(geo, node, i + fill / 2));
 483                         setval(geo, node, i, bval(geo, node, i + fill / 2));
 484                         clearpair(geo, node, i + fill / 2);
 485                 }
 486                 if (fill & 1) {
 487                         setkey(geo, node, i, bkey(geo, node, fill - 1));
 488                         setval(geo, node, i, bval(geo, node, fill - 1));
 489                         clearpair(geo, node, fill - 1);
 490                 }
 491                 goto retry;
 492         }
 493         BUG_ON(fill >= geo->no_pairs);
 494
 495         /* shift and insert */
 496         for (i = fill; i > pos; i--) {
 497                 setkey(geo, node, i, bkey(geo, node, i - 1));
 498                 setval(geo, node, i, bval(geo, node, i - 1));
 499         }
 500         setkey(geo, node, pos, key);
 501         setval(geo, node, pos, val);
 502
 503         return 0;
 504 }
 505
 506 int btree_insert(struct btree_head *head, struct btree_geo *geo,
 507                 unsigned long *key, void *val, gfp_t gfp)
 508 {
 509         return btree_insert_level(head, geo, key, val, 1, gfp);
 510 }
 511 EXPORT_SYMBOL_GPL(btree_insert);
 512
 513 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 514                 unsigned long *key, int level);
 515 static void merge(struct btree_head *head, struct btree_geo *geo, int level,
 516                 unsigned long *left, int lfill,
 517                 unsigned long *right, int rfill,
 518                 unsigned long *parent, int lpos)
 519 {
 520         int i;
 521
 522         for (i = 0; i < rfill; i++) {
 523                 /* Move all keys to the left */
 524                 setkey(geo, left, lfill + i, bkey(geo, right, i));
 525                 setval(geo, left, lfill + i, bval(geo, right, i));
 526         }
 527         /* Exchange left and right child in parent */
 528         setval(geo, parent, lpos, right);
 529         setval(geo, parent, lpos + 1, left);
 530         /* Remove left (formerly right) child from parent */
 531         btree_remove_level(head, geo, bkey(geo, parent, lpos), level + 1);
 532         mempool_free(right, head->mempool);
 533 }
 534
 535 static void rebalance(struct btree_head *head, struct btree_geo *geo,
 536                 unsigned long *key, int level, unsigned long *child, int fill)
 537 {
 538         unsigned long *parent, *left = NULL, *right = NULL;
 539         int i, no_left, no_right;
 540
 541         if (fill == 0) {
 542                 /* Because we don't steal entries from a neigbour, this case
 543                  * can happen.  Parent node contains a single child, this
 544                  * node, so merging with a sibling never happens.
 545                  */
 546                 btree_remove_level(head, geo, key, level + 1);
 547                 mempool_free(child, head->mempool);
 548                 return;
 549         }
 550
 551         parent = find_level(head, geo, key, level + 1);
 552         i = getpos(geo, parent, key);
 553         BUG_ON(bval(geo, parent, i) != child);
 554
 555         if (i > 0) {
 556                 left = bval(geo, parent, i - 1);
 557                 no_left = getfill(geo, left, 0);
 558                 if (fill + no_left <= geo->no_pairs) {
 559                         merge(head, geo, level,
 560                                         left, no_left,
 561                                         child, fill,
 562                                         parent, i - 1);
 563                         return;
 564                 }
 565         }
 566         if (i + 1 < getfill(geo, parent, i)) {
 567                 right = bval(geo, parent, i + 1);
 568                 no_right = getfill(geo, right, 0);
 569                 if (fill + no_right <= geo->no_pairs) {
 570                         merge(head, geo, level,
 571                                         child, fill,
 572                                         right, no_right,
 573                                         parent, i);
 574                         return;
 575                 }
 576         }
 577         /*
 578          * We could also try to steal one entry from the left or right
 579          * neighbor.  By not doing so we changed the invariant from
 580          * "all nodes are at least half full" to "no two neighboring
 581          * nodes can be merged".  Which means that the average fill of
 582          * all nodes is still half or better.
 583          */
 584 }
 585
 586 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 587                 unsigned long *key, int level)
 588 {
 589         unsigned long *node;
 590         int i, pos, fill;
 591         void *ret;
 592
 593         if (level > head->height) {
 594                 /* we recursed all the way up */
 595                 head->height = 0;
 596                 head->node = NULL;
 597                 return NULL;
 598         }
 599
 600         node = find_level(head, geo, key, level);
 601         pos = getpos(geo, node, key);
 602         fill = getfill(geo, node, pos);
 603         if ((level == 1) && (keycmp(geo, node, pos, key) != 0))
 604                 return NULL;
 605         ret = bval(geo, node, pos);
 606
 607         /* remove and shift */
 608         for (i = pos; i < fill - 1; i++) {
 609                 setkey(geo, node, i, bkey(geo, node, i + 1));
 610                 setval(geo, node, i, bval(geo, node, i + 1));
 611         }
 612         clearpair(geo, node, fill - 1);
 613
 614         if (fill - 1 < geo->no_pairs / 2) {
 615                 if (level < head->height)
 616                         rebalance(head, geo, key, level, node, fill - 1);
 617                 else if (fill - 1 == 1)
 618                         btree_shrink(head, geo);
 619         }
 620
 621         return ret;
 622 }
 623
 624 void *btree_remove(struct btree_head *head, struct btree_geo *geo,
 625                 unsigned long *key)
 626 {
 627         if (head->height == 0)
 628                 return NULL;
 629
 630         return btree_remove_level(head, geo, key, 1);
 631 }
 632 EXPORT_SYMBOL_GPL(btree_remove);
 633
 634 int btree_merge(struct btree_head *target, struct btree_head *victim,
 635                 struct btree_geo *geo, gfp_t gfp)
 636 {
 637         unsigned long key[geo->keylen];
 638         unsigned long dup[geo->keylen];
 639         void *val;
 640         int err;
 641
 642         BUG_ON(target == victim);
 643
 644         if (!(target->node)) {
 645                 /* target is empty, just copy fields over */
 646                 target->node = victim->node;
 647                 target->height = victim->height;
 648                 __btree_init(victim);
 649                 return 0;
 650         }
 651
 652         /* TODO: This needs some optimizations.  Currently we do three tree
 653          * walks to remove a single object from the victim.
 654          */
 655         for (;;) {
 656                 if (!btree_last(victim, geo, key))
 657                         break;
 658                 val = btree_lookup(victim, geo, key);
 659                 err = btree_insert(target, geo, key, val, gfp);
 660                 if (err)
 661                         return err;
 662                 /* We must make a copy of the key, as the original will get
 663                  * mangled inside btree_remove. */
 664                 longcpy(dup, key, geo->keylen);
 665                 btree_remove(victim, geo, dup);
 666         }
 667         return 0;
 668 }
 669 EXPORT_SYMBOL_GPL(btree_merge);
 670
 671 static size_t __btree_for_each(struct btree_head *head, struct btree_geo *geo,
 672                                unsigned long *node, unsigned long opaque,
 673                                void (*func)(void *elem, unsigned long opaque,
 674                                             unsigned long *key, size_t index,
 675                                             void *func2),
 676                                void *func2, int reap, int height, size_t count)
 677 {
 678         int i;
 679         unsigned long *child;
 680
 681         for (i = 0; i < geo->no_pairs; i++) {
 682                 child = bval(geo, node, i);
 683                 if (!child)
 684                         break;
 685                 if (height > 1)
 686                         count = __btree_for_each(head, geo, child, opaque,
 687                                         func, func2, reap, height - 1, count);
 688                 else
 689                         func(child, opaque, bkey(geo, node, i), count++,
 690                                         func2);
 691         }
 692         if (reap)
 693                 mempool_free(node, head->mempool);
 694         return count;
 695 }
 696
 697 static void empty(void *elem, unsigned long opaque, unsigned long *key,
 698                   size_t index, void *func2)
 699 {
 700 }
 701
 702 void visitorl(void *elem, unsigned long opaque, unsigned long *key,
 703               size_t index, void *__func)
 704 {
 705         visitorl_t func = __func;
 706
 707         func(elem, opaque, *key, index);
 708 }
 709 EXPORT_SYMBOL_GPL(visitorl);
 710
 711 void visitor32(void *elem, unsigned long opaque, unsigned long *__key,
 712                size_t index, void *__func)
 713 {
 714         visitor32_t func = __func;
 715         u32 *key = (void *)__key;
 716
 717         func(elem, opaque, *key, index);
 718 }
 719 EXPORT_SYMBOL_GPL(visitor32);
 720
 721 void visitor64(void *elem, unsigned long opaque, unsigned long *__key,
 722                size_t index, void *__func)
 723 {
 724         visitor64_t func = __func;
 725         u64 *key = (void *)__key;
 726
 727         func(elem, opaque, *key, index);
 728 }
 729 EXPORT_SYMBOL_GPL(visitor64);
 730
 731 void visitor128(void *elem, unsigned long opaque, unsigned long *__key,
 732                 size_t index, void *__func)
 733 {
 734         visitor128_t func = __func;
 735         u64 *key = (void *)__key;
 736
 737         func(elem, opaque, key[0], key[1], index);
 738 }
 739 EXPORT_SYMBOL_GPL(visitor128);
 740
 741 size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
 742                      unsigned long opaque,
 743                      void (*func)(void *elem, unsigned long opaque,
 744                                   unsigned long *key,
 745                                   size_t index, void *func2),
 746                      void *func2)
 747 {
 748         size_t count = 0;
 749
 750         if (!func2)
 751                 func = empty;
 752         if (head->node)
 753                 count = __btree_for_each(head, geo, head->node, opaque, func,
 754                                 func2, 0, head->height, 0);
 755         return count;
 756 }
 757 EXPORT_SYMBOL_GPL(btree_visitor);
 758
 759 size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
 760                           unsigned long opaque,
 761                           void (*func)(void *elem, unsigned long opaque,
 762                                        unsigned long *key,
 763                                        size_t index, void *func2),
 764                           void *func2)
 765 {
 766         size_t count = 0;
 767
 768         if (!func2)
 769                 func = empty;
 770         if (head->node)
 771                 count = __btree_for_each(head, geo, head->node, opaque, func,
 772                                 func2, 1, head->height, 0);
 773         __btree_init(head);
 774         return count;
 775 }
 776 EXPORT_SYMBOL_GPL(btree_grim_visitor);
 777
 778 static int __init btree_module_init(void)
 779 {
 780         btree_cachep = kmem_cache_create("btree_node", NODESIZE, 0,
 781                         SLAB_HWCACHE_ALIGN, NULL);
 782         return 0;
 783 }
 784
 785 static void __exit btree_module_exit(void)
 786 {
 787         kmem_cache_destroy(btree_cachep);
 788 }
 789
 790 /* If core code starts using btree, initialization should happen even earlier */
 791 module_init(btree_module_init);
 792 module_exit(btree_module_exit);
 793
 794 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 795 MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
 796 MODULE_LICENSE("GPL");