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         memset(node, 0, NODESIZE);
  99         return node;
 100 }
 101
 102 static int longcmp(const unsigned long *l1, const unsigned long *l2, size_t n)
 103 {
 104         size_t i;
 105
 106         for (i = 0; i < n; i++) {
 107                 if (l1[i] < l2[i])
 108                         return -1;
 109                 if (l1[i] > l2[i])
 110                         return 1;
 111         }
 112         return 0;
 113 }
 114
 115 static unsigned long *longcpy(unsigned long *dest, const unsigned long *src,
 116                 size_t n)
 117 {
 118         size_t i;
 119
 120         for (i = 0; i < n; i++)
 121                 dest[i] = src[i];
 122         return dest;
 123 }
 124
 125 static unsigned long *longset(unsigned long *s, unsigned long c, size_t n)
 126 {
 127         size_t i;
 128
 129         for (i = 0; i < n; i++)
 130                 s[i] = c;
 131         return s;
 132 }
 133
 134 static void dec_key(struct btree_geo *geo, unsigned long *key)
 135 {
 136         unsigned long val;
 137         int i;
 138
 139         for (i = geo->keylen - 1; i >= 0; i--) {
 140                 val = key[i];
 141                 key[i] = val - 1;
 142                 if (val)
 143                         break;
 144         }
 145 }
 146
 147 static unsigned long *bkey(struct btree_geo *geo, unsigned long *node, int n)
 148 {
 149         return &node[n * geo->keylen];
 150 }
 151
 152 static void *bval(struct btree_geo *geo, unsigned long *node, int n)
 153 {
 154         return (void *)node[geo->no_longs + n];
 155 }
 156
 157 static void setkey(struct btree_geo *geo, unsigned long *node, int n,
 158                    unsigned long *key)
 159 {
 160         longcpy(bkey(geo, node, n), key, geo->keylen);
 161 }
 162
 163 static void setval(struct btree_geo *geo, unsigned long *node, int n,
 164                    void *val)
 165 {
 166         node[geo->no_longs + n] = (unsigned long) val;
 167 }
 168
 169 static void clearpair(struct btree_geo *geo, unsigned long *node, int n)
 170 {
 171         longset(bkey(geo, node, n), 0, geo->keylen);
 172         node[geo->no_longs + n] = 0;
 173 }
 174
 175 static inline void __btree_init(struct btree_head *head)
 176 {
 177         head->node = NULL;
 178         head->height = 0;
 179 }
 180
 181 void btree_init_mempool(struct btree_head *head, mempool_t *mempool)
 182 {
 183         __btree_init(head);
 184         head->mempool = mempool;
 185 }
 186 EXPORT_SYMBOL_GPL(btree_init_mempool);
 187
 188 int btree_init(struct btree_head *head)
 189 {
 190         __btree_init(head);
 191         head->mempool = mempool_create(0, btree_alloc, btree_free, NULL);
 192         if (!head->mempool)
 193                 return -ENOMEM;
 194         return 0;
 195 }
 196 EXPORT_SYMBOL_GPL(btree_init);
 197
 198 void btree_destroy(struct btree_head *head)
 199 {
 200         mempool_destroy(head->mempool);
 201         head->mempool = NULL;
 202 }
 203 EXPORT_SYMBOL_GPL(btree_destroy);
 204
 205 void *btree_last(struct btree_head *head, struct btree_geo *geo,
 206                  unsigned long *key)
 207 {
 208         int height = head->height;
 209         unsigned long *node = head->node;
 210
 211         if (height == 0)
 212                 return NULL;
 213
 214         for ( ; height > 1; height--)
 215                 node = bval(geo, node, 0);
 216
 217         longcpy(key, bkey(geo, node, 0), geo->keylen);
 218         return bval(geo, node, 0);
 219 }
 220 EXPORT_SYMBOL_GPL(btree_last);
 221
 222 static int keycmp(struct btree_geo *geo, unsigned long *node, int pos,
 223                   unsigned long *key)
 224 {
 225         return longcmp(bkey(geo, node, pos), key, geo->keylen);
 226 }
 227
 228 static int keyzero(struct btree_geo *geo, unsigned long *key)
 229 {
 230         int i;
 231
 232         for (i = 0; i < geo->keylen; i++)
 233                 if (key[i])
 234                         return 0;
 235
 236         return 1;
 237 }
 238
 239 void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
 240                 unsigned long *key)
 241 {
 242         int i, height = head->height;
 243         unsigned long *node = head->node;
 244
 245         if (height == 0)
 246                 return NULL;
 247
 248         for ( ; height > 1; height--) {
 249                 for (i = 0; i < geo->no_pairs; i++)
 250                         if (keycmp(geo, node, i, key) <= 0)
 251                                 break;
 252                 if (i == geo->no_pairs)
 253                         return NULL;
 254                 node = bval(geo, node, i);
 255                 if (!node)
 256                         return NULL;
 257         }
 258
 259         if (!node)
 260                 return NULL;
 261
 262         for (i = 0; i < geo->no_pairs; i++)
 263                 if (keycmp(geo, node, i, key) == 0)
 264                         return bval(geo, node, i);
 265         return NULL;
 266 }
 267 EXPORT_SYMBOL_GPL(btree_lookup);
 268
 269 int btree_update(struct btree_head *head, struct btree_geo *geo,
 270                  unsigned long *key, void *val)
 271 {
 272         int i, height = head->height;
 273         unsigned long *node = head->node;
 274
 275         if (height == 0)
 276                 return -ENOENT;
 277
 278         for ( ; height > 1; height--) {
 279                 for (i = 0; i < geo->no_pairs; i++)
 280                         if (keycmp(geo, node, i, key) <= 0)
 281                                 break;
 282                 if (i == geo->no_pairs)
 283                         return -ENOENT;
 284                 node = bval(geo, node, i);
 285                 if (!node)
 286                         return -ENOENT;
 287         }
 288
 289         if (!node)
 290                 return -ENOENT;
 291
 292         for (i = 0; i < geo->no_pairs; i++)
 293                 if (keycmp(geo, node, i, key) == 0) {
 294                         setval(geo, node, i, val);
 295                         return 0;
 296                 }
 297         return -ENOENT;
 298 }
 299 EXPORT_SYMBOL_GPL(btree_update);
 300
 301 /*
 302  * Usually this function is quite similar to normal lookup.  But the key of
 303  * a parent node may be smaller than the smallest key of all its siblings.
 304  * In such a case we cannot just return NULL, as we have only proven that no
 305  * key smaller than __key, but larger than this parent key exists.
 306  * So we set __key to the parent key and retry.  We have to use the smallest
 307  * such parent key, which is the last parent key we encountered.
 308  */
 309 void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
 310                      unsigned long *__key)
 311 {
 312         int i, height;
 313         unsigned long *node, *oldnode;
 314         unsigned long *retry_key = NULL, key[geo->keylen];
 315
 316         if (keyzero(geo, __key))
 317                 return NULL;
 318
 319         if (head->height == 0)
 320                 return NULL;
 321 retry:
 322         longcpy(key, __key, geo->keylen);
 323         dec_key(geo, key);
 324
 325         node = head->node;
 326         for (height = head->height ; height > 1; height--) {
 327                 for (i = 0; i < geo->no_pairs; i++)
 328                         if (keycmp(geo, node, i, key) <= 0)
 329                                 break;
 330                 if (i == geo->no_pairs)
 331                         goto miss;
 332                 oldnode = node;
 333                 node = bval(geo, node, i);
 334                 if (!node)
 335                         goto miss;
 336                 retry_key = bkey(geo, oldnode, i);
 337         }
 338
 339         if (!node)
 340                 goto miss;
 341
 342         for (i = 0; i < geo->no_pairs; i++) {
 343                 if (keycmp(geo, node, i, key) <= 0) {
 344                         if (bval(geo, node, i)) {
 345                                 longcpy(__key, bkey(geo, node, i), geo->keylen);
 346                                 return bval(geo, node, i);
 347                         } else
 348                                 goto miss;
 349                 }
 350         }
 351 miss:
 352         if (retry_key) {
 353                 __key = retry_key;
 354                 retry_key = NULL;
 355                 goto retry;
 356         }
 357         return NULL;
 358 }
 359
 360 static int getpos(struct btree_geo *geo, unsigned long *node,
 361                 unsigned long *key)
 362 {
 363         int i;
 364
 365         for (i = 0; i < geo->no_pairs; i++) {
 366                 if (keycmp(geo, node, i, key) <= 0)
 367                         break;
 368         }
 369         return i;
 370 }
 371
 372 static int getfill(struct btree_geo *geo, unsigned long *node, int start)
 373 {
 374         int i;
 375
 376         for (i = start; i < geo->no_pairs; i++)
 377                 if (!bval(geo, node, i))
 378                         break;
 379         return i;
 380 }
 381
 382 /*
 383  * locate the correct leaf node in the btree
 384  */
 385 static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
 386                 unsigned long *key, int level)
 387 {
 388         unsigned long *node = head->node;
 389         int i, height;
 390
 391         for (height = head->height; height > level; height--) {
 392                 for (i = 0; i < geo->no_pairs; i++)
 393                         if (keycmp(geo, node, i, key) <= 0)
 394                                 break;
 395
 396                 if ((i == geo->no_pairs) || !bval(geo, node, i)) {
 397                         /* right-most key is too large, update it */
 398                         /* FIXME: If the right-most key on higher levels is
 399                          * always zero, this wouldn't be necessary. */
 400                         i--;
 401                         setkey(geo, node, i, key);
 402                 }
 403                 BUG_ON(i < 0);
 404                 node = bval(geo, node, i);
 405         }
 406         BUG_ON(!node);
 407         return node;
 408 }
 409
 410 static int btree_grow(struct btree_head *head, struct btree_geo *geo,
 411                       gfp_t gfp)
 412 {
 413         unsigned long *node;
 414         int fill;
 415
 416         node = btree_node_alloc(head, gfp);
 417         if (!node)
 418                 return -ENOMEM;
 419         if (head->node) {
 420                 fill = getfill(geo, head->node, 0);
 421                 setkey(geo, node, 0, bkey(geo, head->node, fill - 1));
 422                 setval(geo, node, 0, head->node);
 423         }
 424         head->node = node;
 425         head->height++;
 426         return 0;
 427 }
 428
 429 static void btree_shrink(struct btree_head *head, struct btree_geo *geo)
 430 {
 431         unsigned long *node;
 432         int fill;
 433
 434         if (head->height <= 1)
 435                 return;
 436
 437         node = head->node;
 438         fill = getfill(geo, node, 0);
 439         BUG_ON(fill > 1);
 440         head->node = bval(geo, node, 0);
 441         head->height--;
 442         mempool_free(node, head->mempool);
 443 }
 444
 445 static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
 446                               unsigned long *key, void *val, int level,
 447                               gfp_t gfp)
 448 {
 449         unsigned long *node;
 450         int i, pos, fill, err;
 451
 452         BUG_ON(!val);
 453         if (head->height < level) {
 454                 err = btree_grow(head, geo, gfp);
 455                 if (err)
 456                         return err;
 457         }
 458
 459 retry:
 460         node = find_level(head, geo, key, level);
 461         pos = getpos(geo, node, key);
 462         fill = getfill(geo, node, pos);
 463         /* two identical keys are not allowed */
 464         BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);
 465
 466         if (fill == geo->no_pairs) {
 467                 /* need to split node */
 468                 unsigned long *new;
 469
 470                 new = btree_node_alloc(head, gfp);
 471                 if (!new)
 472                         return -ENOMEM;
 473                 err = btree_insert_level(head, geo,
 474                                 bkey(geo, node, fill / 2 - 1),
 475                                 new, level + 1, gfp);
 476                 if (err) {
 477                         mempool_free(new, head->mempool);
 478                         return err;
 479                 }
 480                 for (i = 0; i < fill / 2; i++) {
 481                         setkey(geo, new, i, bkey(geo, node, i));
 482                         setval(geo, new, i, bval(geo, node, i));
 483                         setkey(geo, node, i, bkey(geo, node, i + fill / 2));
 484                         setval(geo, node, i, bval(geo, node, i + fill / 2));
 485                         clearpair(geo, node, i + fill / 2);
 486                 }
 487                 if (fill & 1) {
 488                         setkey(geo, node, i, bkey(geo, node, fill - 1));
 489                         setval(geo, node, i, bval(geo, node, fill - 1));
 490                         clearpair(geo, node, fill - 1);
 491                 }
 492                 goto retry;
 493         }
 494         BUG_ON(fill >= geo->no_pairs);
 495
 496         /* shift and insert */
 497         for (i = fill; i > pos; i--) {
 498                 setkey(geo, node, i, bkey(geo, node, i - 1));
 499                 setval(geo, node, i, bval(geo, node, i - 1));
 500         }
 501         setkey(geo, node, pos, key);
 502         setval(geo, node, pos, val);
 503
 504         return 0;
 505 }
 506
 507 int btree_insert(struct btree_head *head, struct btree_geo *geo,
 508                 unsigned long *key, void *val, gfp_t gfp)
 509 {
 510         return btree_insert_level(head, geo, key, val, 1, gfp);
 511 }
 512 EXPORT_SYMBOL_GPL(btree_insert);
 513
 514 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 515                 unsigned long *key, int level);
 516 static void merge(struct btree_head *head, struct btree_geo *geo, int level,
 517                 unsigned long *left, int lfill,
 518                 unsigned long *right, int rfill,
 519                 unsigned long *parent, int lpos)
 520 {
 521         int i;
 522
 523         for (i = 0; i < rfill; i++) {
 524                 /* Move all keys to the left */
 525                 setkey(geo, left, lfill + i, bkey(geo, right, i));
 526                 setval(geo, left, lfill + i, bval(geo, right, i));
 527         }
 528         /* Exchange left and right child in parent */
 529         setval(geo, parent, lpos, right);
 530         setval(geo, parent, lpos + 1, left);
 531         /* Remove left (formerly right) child from parent */
 532         btree_remove_level(head, geo, bkey(geo, parent, lpos), level + 1);
 533         mempool_free(right, head->mempool);
 534 }
 535
 536 static void rebalance(struct btree_head *head, struct btree_geo *geo,
 537                 unsigned long *key, int level, unsigned long *child, int fill)
 538 {
 539         unsigned long *parent, *left = NULL, *right = NULL;
 540         int i, no_left, no_right;
 541
 542         if (fill == 0) {
 543                 /* Because we don't steal entries from a neigbour, this case
 544                  * can happen.  Parent node contains a single child, this
 545                  * node, so merging with a sibling never happens.
 546                  */
 547                 btree_remove_level(head, geo, key, level + 1);
 548                 mempool_free(child, head->mempool);
 549                 return;
 550         }
 551
 552         parent = find_level(head, geo, key, level + 1);
 553         i = getpos(geo, parent, key);
 554         BUG_ON(bval(geo, parent, i) != child);
 555
 556         if (i > 0) {
 557                 left = bval(geo, parent, i - 1);
 558                 no_left = getfill(geo, left, 0);
 559                 if (fill + no_left <= geo->no_pairs) {
 560                         merge(head, geo, level,
 561                                         left, no_left,
 562                                         child, fill,
 563                                         parent, i - 1);
 564                         return;
 565                 }
 566         }
 567         if (i + 1 < getfill(geo, parent, i)) {
 568                 right = bval(geo, parent, i + 1);
 569                 no_right = getfill(geo, right, 0);
 570                 if (fill + no_right <= geo->no_pairs) {
 571                         merge(head, geo, level,
 572                                         child, fill,
 573                                         right, no_right,
 574                                         parent, i);
 575                         return;
 576                 }
 577         }
 578         /*
 579          * We could also try to steal one entry from the left or right
 580          * neighbor.  By not doing so we changed the invariant from
 581          * "all nodes are at least half full" to "no two neighboring
 582          * nodes can be merged".  Which means that the average fill of
 583          * all nodes is still half or better.
 584          */
 585 }
 586
 587 static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
 588                 unsigned long *key, int level)
 589 {
 590         unsigned long *node;
 591         int i, pos, fill;
 592         void *ret;
 593
 594         if (level > head->height) {
 595                 /* we recursed all the way up */
 596                 head->height = 0;
 597                 head->node = NULL;
 598                 return NULL;
 599         }
 600
 601         node = find_level(head, geo, key, level);
 602         pos = getpos(geo, node, key);
 603         fill = getfill(geo, node, pos);
 604         if ((level == 1) && (keycmp(geo, node, pos, key) != 0))
 605                 return NULL;
 606         ret = bval(geo, node, pos);
 607
 608         /* remove and shift */
 609         for (i = pos; i < fill - 1; i++) {
 610                 setkey(geo, node, i, bkey(geo, node, i + 1));
 611                 setval(geo, node, i, bval(geo, node, i + 1));
 612         }
 613         clearpair(geo, node, fill - 1);
 614
 615         if (fill - 1 < geo->no_pairs / 2) {
 616                 if (level < head->height)
 617                         rebalance(head, geo, key, level, node, fill - 1);
 618                 else if (fill - 1 == 1)
 619                         btree_shrink(head, geo);
 620         }
 621
 622         return ret;
 623 }
 624
 625 void *btree_remove(struct btree_head *head, struct btree_geo *geo,
 626                 unsigned long *key)
 627 {
 628         if (head->height == 0)
 629                 return NULL;
 630
 631         return btree_remove_level(head, geo, key, 1);
 632 }
 633 EXPORT_SYMBOL_GPL(btree_remove);
 634
 635 int btree_merge(struct btree_head *target, struct btree_head *victim,
 636                 struct btree_geo *geo, gfp_t gfp)
 637 {
 638         unsigned long key[geo->keylen];
 639         unsigned long dup[geo->keylen];
 640         void *val;
 641         int err;
 642
 643         BUG_ON(target == victim);
 644
 645         if (!(target->node)) {
 646                 /* target is empty, just copy fields over */
 647                 target->node = victim->node;
 648                 target->height = victim->height;
 649                 __btree_init(victim);
 650                 return 0;
 651         }
 652
 653         /* TODO: This needs some optimizations.  Currently we do three tree
 654          * walks to remove a single object from the victim.
 655          */
 656         for (;;) {
 657                 if (!btree_last(victim, geo, key))
 658                         break;
 659                 val = btree_lookup(victim, geo, key);
 660                 err = btree_insert(target, geo, key, val, gfp);
 661                 if (err)
 662                         return err;
 663                 /* We must make a copy of the key, as the original will get
 664                  * mangled inside btree_remove. */
 665                 longcpy(dup, key, geo->keylen);
 666                 btree_remove(victim, geo, dup);
 667         }
 668         return 0;
 669 }
 670 EXPORT_SYMBOL_GPL(btree_merge);
 671
 672 static size_t __btree_for_each(struct btree_head *head, struct btree_geo *geo,
 673                                unsigned long *node, unsigned long opaque,
 674                                void (*func)(void *elem, unsigned long opaque,
 675                                             unsigned long *key, size_t index,
 676                                             void *func2),
 677                                void *func2, int reap, int height, size_t count)
 678 {
 679         int i;
 680         unsigned long *child;
 681
 682         for (i = 0; i < geo->no_pairs; i++) {
 683                 child = bval(geo, node, i);
 684                 if (!child)
 685                         break;
 686                 if (height > 1)
 687                         count = __btree_for_each(head, geo, child, opaque,
 688                                         func, func2, reap, height - 1, count);
 689                 else
 690                         func(child, opaque, bkey(geo, node, i), count++,
 691                                         func2);
 692         }
 693         if (reap)
 694                 mempool_free(node, head->mempool);
 695         return count;
 696 }
 697
 698 static void empty(void *elem, unsigned long opaque, unsigned long *key,
 699                   size_t index, void *func2)
 700 {
 701 }
 702
 703 void visitorl(void *elem, unsigned long opaque, unsigned long *key,
 704               size_t index, void *__func)
 705 {
 706         visitorl_t func = __func;
 707
 708         func(elem, opaque, *key, index);
 709 }
 710 EXPORT_SYMBOL_GPL(visitorl);
 711
 712 void visitor32(void *elem, unsigned long opaque, unsigned long *__key,
 713                size_t index, void *__func)
 714 {
 715         visitor32_t func = __func;
 716         u32 *key = (void *)__key;
 717
 718         func(elem, opaque, *key, index);
 719 }
 720 EXPORT_SYMBOL_GPL(visitor32);
 721
 722 void visitor64(void *elem, unsigned long opaque, unsigned long *__key,
 723                size_t index, void *__func)
 724 {
 725         visitor64_t func = __func;
 726         u64 *key = (void *)__key;
 727
 728         func(elem, opaque, *key, index);
 729 }
 730 EXPORT_SYMBOL_GPL(visitor64);
 731
 732 void visitor128(void *elem, unsigned long opaque, unsigned long *__key,
 733                 size_t index, void *__func)
 734 {
 735         visitor128_t func = __func;
 736         u64 *key = (void *)__key;
 737
 738         func(elem, opaque, key[0], key[1], index);
 739 }
 740 EXPORT_SYMBOL_GPL(visitor128);
 741
 742 size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
 743                      unsigned long opaque,
 744                      void (*func)(void *elem, unsigned long opaque,
 745                                   unsigned long *key,
 746                                   size_t index, void *func2),
 747                      void *func2)
 748 {
 749         size_t count = 0;
 750
 751         if (!func2)
 752                 func = empty;
 753         if (head->node)
 754                 count = __btree_for_each(head, geo, head->node, opaque, func,
 755                                 func2, 0, head->height, 0);
 756         return count;
 757 }
 758 EXPORT_SYMBOL_GPL(btree_visitor);
 759
 760 size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
 761                           unsigned long opaque,
 762                           void (*func)(void *elem, unsigned long opaque,
 763                                        unsigned long *key,
 764                                        size_t index, void *func2),
 765                           void *func2)
 766 {
 767         size_t count = 0;
 768
 769         if (!func2)
 770                 func = empty;
 771         if (head->node)
 772                 count = __btree_for_each(head, geo, head->node, opaque, func,
 773                                 func2, 1, head->height, 0);
 774         __btree_init(head);
 775         return count;
 776 }
 777 EXPORT_SYMBOL_GPL(btree_grim_visitor);
 778
 779 static int __init btree_module_init(void)
 780 {
 781         btree_cachep = kmem_cache_create("btree_node", NODESIZE, 0,
 782                         SLAB_HWCACHE_ALIGN, NULL);
 783         return 0;
 784 }
 785
 786 static void __exit btree_module_exit(void)
 787 {
 788         kmem_cache_destroy(btree_cachep);
 789 }
 790
 791 /* If core code starts using btree, initialization should happen even earlier */
 792 module_init(btree_module_init);
 793 module_exit(btree_module_exit);
 794
 795 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 796 MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
 797 MODULE_LICENSE("GPL");