aboutsummaryrefslogtreecommitdiff
path: root/lib/btree.c
blob: f9a484676cb6a8e4782333ce164bf0662b583b78 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
/*
 * lib/btree.c	- Simple In-memory B+Tree
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2007-2008 Joern Engel <joern@logfs.org>
 * Bits and pieces stolen from Peter Zijlstra's code, which is
 * Copyright 2007, Red Hat Inc. Peter Zijlstra <pzijlstr@redhat.com>
 * GPLv2
 *
 * see http://programming.kicks-ass.net/kernel-patches/vma_lookup/btree.patch
 *
 * A relatively simple B+Tree implementation.  I have written it as a learning
 * exercise to understand how B+Trees work.  Turned out to be useful as well.
 *
 * B+Trees can be used similar to Linux radix trees (which don't have anything
 * in common with textbook radix trees, beware).  Prerequisite for them working
 * well is that access to a random tree node is much faster than a large number
 * of operations within each node.
 *
 * Disks have fulfilled the prerequisite for a long time.  More recently DRAM
 * has gained similar properties, as memory access times, when measured in cpu
 * cycles, have increased.  Cacheline sizes have increased as well, which also
 * helps B+Trees.
 *
 * Compared to radix trees, B+Trees are more efficient when dealing with a
 * sparsely populated address space.  Between 25% and 50% of the memory is
 * occupied with valid pointers.  When densely populated, radix trees contain
 * ~98% pointers - hard to beat.  Very sparse radix trees contain only ~2%
 * pointers.
 *
 * This particular implementation stores pointers identified by a long value.
 * Storing NULL pointers is illegal, lookup will return NULL when no entry
 * was found.
 *
 * A tricks was used that is not commonly found in textbooks.  The lowest
 * values are to the right, not to the left.  All used slots within a node
 * are on the left, all unused slots contain NUL values.  Most operations
 * simply loop once over all slots and terminate on the first NUL.
 */

#include <linux/btree.h>
#include <linux/cache.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define NODESIZE MAX(L1_CACHE_BYTES, 128)

struct btree_geo {
	int keylen;
	int no_pairs;
	int no_longs;
};

struct btree_geo btree_geo32 = {
	.keylen = 1,
	.no_pairs = NODESIZE / sizeof(long) / 2,
	.no_longs = NODESIZE / sizeof(long) / 2,
};
EXPORT_SYMBOL_GPL(btree_geo32);

#define LONG_PER_U64 (64 / BITS_PER_LONG)
struct btree_geo btree_geo64 = {
	.keylen = LONG_PER_U64,
	.no_pairs = NODESIZE / sizeof(long) / (1 + LONG_PER_U64),
	.no_longs = LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + LONG_PER_U64)),
};
EXPORT_SYMBOL_GPL(btree_geo64);

struct btree_geo btree_geo128 = {
	.keylen = 2 * LONG_PER_U64,
	.no_pairs = NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64),
	.no_longs = 2 * LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64)),
};
EXPORT_SYMBOL_GPL(btree_geo128);

static struct kmem_cache *btree_cachep;

void *btree_alloc(gfp_t gfp_mask, void *pool_data)
{
	return kmem_cache_alloc(btree_cachep, gfp_mask);
}
EXPORT_SYMBOL_GPL(btree_alloc);

void btree_free(void *element, void *pool_data)
{
	kmem_cache_free(btree_cachep, element);
}
EXPORT_SYMBOL_GPL(btree_free);

static unsigned long *btree_node_alloc(struct btree_head *head, gfp_t gfp)
{
	unsigned long *node;

	node = mempool_alloc(head->mempool, gfp);
	if (likely(node))
		memset(node, 0, NODESIZE);
	return node;
}

static int longcmp(const unsigned long *l1, const unsigned long *l2, size_t n)
{
	size_t i;

	for (i = 0; i < n; i++) {
		if (l1[i] < l2[i])
			return -1;
		if (l1[i] > l2[i])
			return 1;
	}
	return 0;
}

static unsigned long *longcpy(unsigned long *dest, const unsigned long *src,
		size_t n)
{
	size_t i;

	for (i = 0; i < n; i++)
		dest[i] = src[i];
	return dest;
}

static unsigned long *longset(unsigned long *s, unsigned long c, size_t n)
{
	size_t i;

	for (i = 0; i < n; i++)
		s[i] = c;
	return s;
}

static void dec_key(struct btree_geo *geo, unsigned long *key)
{
	unsigned long val;
	int i;

	for (i = geo->keylen - 1; i >= 0; i--) {
		val = key[i];
		key[i] = val - 1;
		if (val)
			break;
	}
}

static unsigned long *bkey(struct btree_geo *geo, unsigned long *node, int n)
{
	return &node[n * geo->keylen];
}

static void *bval(struct btree_geo *geo, unsigned long *node, int n)
{
	return (void *)node[geo->no_longs + n];
}

static void setkey(struct btree_geo *geo, unsigned long *node, int n,
		   unsigned long *key)
{
	longcpy(bkey(geo, node, n), key, geo->keylen);
}

static void setval(struct btree_geo *geo, unsigned long *node, int n,
		   void *val)
{
	node[geo->no_longs + n] = (unsigned long) val;
}

static void clearpair(struct btree_geo *geo, unsigned long *node, int n)
{
	longset(bkey(geo, node, n), 0, geo->keylen);
	node[geo->no_longs + n] = 0;
}

static inline void __btree_init(struct btree_head *head)
{
	head->node = NULL;
	head->height = 0;
}

void btree_init_mempool(struct btree_head *head, mempool_t *mempool)
{
	__btree_init(head);
	head->mempool = mempool;
}
EXPORT_SYMBOL_GPL(btree_init_mempool);

int btree_init(struct btree_head *head)
{
	__btree_init(head);
	head->mempool = mempool_create(0, btree_alloc, btree_free, NULL);
	if (!head->mempool)
		return -ENOMEM;
	return 0;
}
EXPORT_SYMBOL_GPL(btree_init);

void btree_destroy(struct btree_head *head)
{
	mempool_destroy(head->mempool);
	head->mempool = NULL;
}
EXPORT_SYMBOL_GPL(btree_destroy);

void *btree_last(struct btree_head *head, struct btree_geo *geo,
		 unsigned long *key)
{
	int height = head->height;
	unsigned long *node = head->node;

	if (height == 0)
		return NULL;

	for ( ; height > 1; height--)
		node = bval(geo, node, 0);

	longcpy(key, bkey(geo, node, 0), geo->keylen);
	return bval(geo, node, 0);
}
EXPORT_SYMBOL_GPL(btree_last);

static int keycmp(struct btree_geo *geo, unsigned long *node, int pos,
		  unsigned long *key)
{
	return longcmp(bkey(geo, node, pos), key, geo->keylen);
}

static int keyzero(struct btree_geo *geo, unsigned long *key)
{
	int i;

	for (i = 0; i < geo->keylen; i++)
		if (key[i])
			return 0;

	return 1;
}

void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key)
{
	int i, height = head->height;
	unsigned long *node = head->node;

	if (height == 0)
		return NULL;

	for ( ; height > 1; height--) {
		for (i = 0; i < geo->no_pairs; i++)
			if (keycmp(geo, node, i, key) <= 0)
				break;
		if (i == geo->no_pairs)
			return NULL;
		node = bval(geo, node, i);
		if (!node)
			return NULL;
	}

	if (!node)
		return NULL;

	for (i = 0; i < geo->no_pairs; i++)
		if (keycmp(geo, node, i, key) == 0)
			return bval(geo, node, i);
	return NULL;
}
EXPORT_SYMBOL_GPL(btree_lookup);

int btree_update(struct btree_head *head, struct btree_geo *geo,
		 unsigned long *key, void *val)
{
	int i, height = head->height;
	unsigned long *node = head->node;

	if (height == 0)
		return -ENOENT;

	for ( ; height > 1; height--) {
		for (i = 0; i < geo->no_pairs; i++)
			if (keycmp(geo, node, i, key) <= 0)
				break;
		if (i == geo->no_pairs)
			return -ENOENT;
		node = bval(geo, node, i);
		if (!node)
			return -ENOENT;
	}

	if (!node)
		return -ENOENT;

	for (i = 0; i < geo->no_pairs; i++)
		if (keycmp(geo, node, i, key) == 0) {
			setval(geo, node, i, val);
			return 0;
		}
	return -ENOENT;
}
EXPORT_SYMBOL_GPL(btree_update);

/*
 * Usually this function is quite similar to normal lookup.  But the key of
 * a parent node may be smaller than the smallest key of all its siblings.
 * In such a case we cannot just return NULL, as we have only proven that no
 * key smaller than __key, but larger than this parent key exists.
 * So we set __key to the parent key and retry.  We have to use the smallest
 * such parent key, which is the last parent key we encountered.
 */
void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
		     unsigned long *__key)
{
	int i, height;
	unsigned long *node, *oldnode;
	unsigned long *retry_key = NULL, key[geo->keylen];

	if (keyzero(geo, __key))
		return NULL;

	if (head->height == 0)
		return NULL;
	longcpy(key, __key, geo->keylen);
retry:
	dec_key(geo, key);

	node = head->node;
	for (height = head->height ; height > 1; height--) {
		for (i = 0; i < geo->no_pairs; i++)
			if (keycmp(geo, node, i, key) <= 0)
				break;
		if (i == geo->no_pairs)
			goto miss;
		oldnode = node;
		node = bval(geo, node, i);
		if (!node)
			goto miss;
		retry_key = bkey(geo, oldnode, i);
	}

	if (!node)
		goto miss;

	for (i = 0; i < geo->no_pairs; i++) {
		if (keycmp(geo, node, i, key) <= 0) {
			if (bval(geo, node, i)) {
				longcpy(__key, bkey(geo, node, i), geo->keylen);
				return bval(geo, node, i);
			} else
				goto miss;
		}
	}
miss:
	if (retry_key) {
		longcpy(key, retry_key, geo->keylen);
		retry_key = NULL;
		goto retry;
	}
	return NULL;
}
EXPORT_SYMBOL_GPL(btree_get_prev);

static int getpos(struct btree_geo *geo, unsigned long *node,
		unsigned long *key)
{
	int i;

	for (i = 0; i < geo->no_pairs; i++) {
		if (keycmp(geo, node, i, key) <= 0)
			break;
	}
	return i;
}

static int getfill(struct btree_geo *geo, unsigned long *node, int start)
{
	int i;

	for (i = start; i < geo->no_pairs; i++)
		if (!bval(geo, node, i))
			break;
	return i;
}

/*
 * locate the correct leaf node in the btree
 */
static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key, int level)
{
	unsigned long *node = head->node;
	int i, height;

	for (height = head->height; height > level; height--) {
		for (i = 0; i < geo->no_pairs; i++)
			if (keycmp(geo, node, i, key) <= 0)
				break;

		if ((i == geo->no_pairs) || !bval(geo, node, i)) {
			/* right-most key is too large, update it */
			/* FIXME: If the right-most key on higher levels is
			 * always zero, this wouldn't be necessary. */
			i--;
			setkey(geo, node, i, key);
		}
		BUG_ON(i < 0);
		node = bval(geo, node, i);
	}
	BUG_ON(!node);
	return node;
}

static int btree_grow(struct btree_head *head, struct btree_geo *geo,
		      gfp_t gfp)
{
	unsigned long *node;
	int fill;

	node = btree_node_alloc(head, gfp);
	if (!node)
		return -ENOMEM;
	if (head->node) {
		fill = getfill(geo, head->node, 0);
		setkey(geo, node, 0, bkey(geo, head->node, fill - 1));
		setval(geo, node, 0, head->node);
	}
	head->node = node;
	head->height++;
	return 0;
}

static void btree_shrink(struct btree_head *head, struct btree_geo *geo)
{
	unsigned long *node;
	int fill;

	if (head->height <= 1)
		return;

	node = head->node;
	fill = getfill(geo, node, 0);
	BUG_ON(fill > 1);
	head->node = bval(geo, node, 0);
	head->height--;
	mempool_free(node, head->mempool);
}

static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
			      unsigned long *key, void *val, int level,
			      gfp_t gfp)
{
	unsigned long *node;
	int i, pos, fill, err;

	BUG_ON(!val);
	if (head->height < level) {
		err = btree_grow(head, geo, gfp);
		if (err)
			return err;
	}

retry:
	node = find_level(head, geo, key, level);
	pos = getpos(geo, node, key);
	fill = getfill(geo, node, pos);
	/* two identical keys are not allowed */
	BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);

	if (fill == geo->no_pairs) {
		/* need to split node */
		unsigned long *new;

		new = btree_node_alloc(head, gfp);
		if (!new)
			return -ENOMEM;
		err = btree_insert_level(head, geo,
				bkey(geo, node, fill / 2 - 1),
				new, level + 1, gfp);
		if (err) {
			mempool_free(new, head->mempool);
			return err;
		}
		for (i = 0; i < fill / 2; i++) {
			setkey(geo, new, i, bkey(geo, node, i));
			setval(geo, new, i, bval(geo, node, i));
			setkey(geo, node, i, bkey(geo, node, i + fill / 2));
			setval(geo, node, i, bval(geo, node, i + fill / 2));
			clearpair(geo, node, i + fill / 2);
		}
		if (fill & 1) {
			setkey(geo, node, i, bkey(geo, node, fill - 1));
			setval(geo, node, i, bval(geo, node, fill - 1));
			clearpair(geo, node, fill - 1);
		}
		goto retry;
	}
	BUG_ON(fill >= geo->no_pairs);

	/* shift and insert */
	for (i = fill; i > pos; i--) {
		setkey(geo, node, i, bkey(geo, node, i - 1));
		setval(geo, node, i, bval(geo, node, i - 1));
	}
	setkey(geo, node, pos, key);
	setval(geo, node, pos, val);

	return 0;
}

int btree_insert(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key, void *val, gfp_t gfp)
{
	BUG_ON(!val);
	return btree_insert_level(head, geo, key, val, 1, gfp);
}
EXPORT_SYMBOL_GPL(btree_insert);

static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key, int level);
static void merge(struct btree_head *head, struct btree_geo *geo, int level,
		unsigned long *left, int lfill,
		unsigned long *right, int rfill,
		unsigned long *parent, int lpos)
{
	int i;

	for (i = 0; i < rfill; i++) {
		/* Move all keys to the left */
		setkey(geo, left, lfill + i, bkey(geo, right, i));
		setval(geo, left, lfill + i, bval(geo, right, i));
	}
	/* Exchange left and right child in parent */
	setval(geo, parent, lpos, right);
	setval(geo, parent, lpos + 1, left);
	/* Remove left (formerly right) child from parent */
	btree_remove_level(head, geo, bkey(geo, parent, lpos), level + 1);
	mempool_free(right, head->mempool);
}

static void rebalance(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key, int level, unsigned long *child, int fill)
{
	unsigned long *parent, *left = NULL, *right = NULL;
	int i, no_left, no_right;

	if (fill == 0) {
		/* Because we don't steal entries from a neighbour, this case
		 * can happen.  Parent node contains a single child, this
		 * node, so merging with a sibling never happens.
		 */
		btree_remove_level(head, geo, key, level + 1);
		mempool_free(child, head->mempool);
		return;
	}

	parent = find_level(head, geo, key, level + 1);
	i = getpos(geo, parent, key);
	BUG_ON(bval(geo, parent, i) != child);

	if (i > 0) {
		left = bval(geo, parent, i - 1);
		no_left = getfill(geo, left, 0);
		if (fill + no_left <= geo->no_pairs) {
			merge(head, geo, level,
					left, no_left,
					child, fill,
					parent, i - 1);
			return;
		}
	}
	if (i + 1 < getfill(geo, parent, i)) {
		right = bval(geo, parent, i + 1);
		no_right = getfill(geo, right, 0);
		if (fill + no_right <= geo->no_pairs) {
			merge(head, geo, level,
					child, fill,
					right, no_right,
					parent, i);
			return;
		}
	}
	/*
	 * We could also try to steal one entry from the left or right
	 * neighbor.  By not doing so we changed the invariant from
	 * "all nodes are at least half full" to "no two neighboring
	 * nodes can be merged".  Which means that the average fill of
	 * all nodes is still half or better.
	 */
}

static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key, int level)
{
	unsigned long *node;
	int i, pos, fill;
	void *ret;

	if (level > head->height) {
		/* we recursed all the way up */
		head->height = 0;
		head->node = NULL;
		return NULL;
	}

	node = find_level(head, geo, key, level);
	pos = getpos(geo, node, key);
	fill = getfill(geo, node, pos);
	if ((level == 1) && (keycmp(geo, node, pos, key) != 0))
		return NULL;
	ret = bval(geo, node, pos);

	/* remove and shift */
	for (i = pos; i < fill - 1; i++) {
		setkey(geo, node, i, bkey(geo, node, i + 1));
		setval(geo, node, i, bval(geo, node, i + 1));
	}
	clearpair(geo, node, fill - 1);

	if (fill - 1 < geo->no_pairs / 2) {
		if (level < head->height)
			rebalance(head, geo, key, level, node, fill - 1);
		else if (fill - 1 == 1)
			btree_shrink(head, geo);
	}

	return ret;
}

void *btree_remove(struct btree_head *head, struct btree_geo *geo,
		unsigned long *key)
{
	if (head->height == 0)
		return NULL;

	return btree_remove_level(head, geo, key, 1);
}
EXPORT_SYMBOL_GPL(btree_remove);

int btree_merge(struct btree_head *target, struct btree_head *victim,
		struct btree_geo *geo, gfp_t gfp)
{
	unsigned long key[geo->keylen];
	unsigned long dup[geo->keylen];
	void *val;
	int err;

	BUG_ON(target == victim);

	if (!(target->node)) {
		/* target is empty, just copy fields over */
		target->node = victim->node;
		target->height = victim->height;
		__btree_init(victim);
		return 0;
	}

	/* TODO: This needs some optimizations.  Currently we do three tree
	 * walks to remove a single object from the victim.
	 */
	for (;;) {
		if (!btree_last(victim, geo, key))
			break;
		val = btree_lookup(victim, geo, key);
		err = btree_insert(target, geo, key, val, gfp);
		if (err)
			return err;
		/* We must make a copy of the key, as the original will get
		 * mangled inside btree_remove. */
		longcpy(dup, key, geo->keylen);
		btree_remove(victim, geo, dup);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(btree_merge);

static size_t __btree_for_each(struct btree_head *head, struct btree_geo *geo,
			       unsigned long *node, unsigned long opaque,
			       void (*func)(void *elem, unsigned long opaque,
					    unsigned long *key, size_t index,
					    void *func2),
			       void *func2, int reap, int height, size_t count)
{
	int i;
	unsigned long *child;

	for (i = 0; i < geo->no_pairs; i++) {
		child = bval(geo, node, i);
		if (!child)
			break;
		if (height > 1)
			count = __btree_for_each(head, geo, child, opaque,
					func, func2, reap, height - 1, count);
		else
			func(child, opaque, bkey(geo, node, i), count++,
					func2);
	}
	if (reap)
		mempool_free(node, head->mempool);
	return count;
}

static void empty(void *elem, unsigned long opaque, unsigned long *key,
		  size_t index, void *func2)
{
}

void visitorl(void *elem, unsigned long opaque, unsigned long *key,
	      size_t index, void *__func)
{
	visitorl_t func = __func;

	func(elem, opaque, *key, index);
}
EXPORT_SYMBOL_GPL(visitorl);

void visitor32(void *elem, unsigned long opaque, unsigned long *__key,
	       size_t index, void *__func)
{
	visitor32_t func = __func;
	u32 *key = (void *)__key;

	func(elem, opaque, *key, index);
}
EXPORT_SYMBOL_GPL(visitor32);

void visitor64(void *elem, unsigned long opaque, unsigned long *__key,
	       size_t index, void *__func)
{
	visitor64_t func = __func;
	u64 *key = (void *)__key;

	func(elem, opaque, *key, index);
}
EXPORT_SYMBOL_GPL(visitor64);

void visitor128(void *elem, unsigned long opaque, unsigned long *__key,
		size_t index, void *__func)
{
	visitor128_t func = __func;
	u64 *key = (void *)__key;

	func(elem, opaque, key[0], key[1], index);
}
EXPORT_SYMBOL_GPL(visitor128);

size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
		     unsigned long opaque,
		     void (*func)(void *elem, unsigned long opaque,
		     		  unsigned long *key,
		     		  size_t index, void *func2),
		     void *func2)
{
	size_t count = 0;

	if (!func2)
		func = empty;
	if (head->node)
		count = __btree_for_each(head, geo, head->node, opaque, func,
				func2, 0, head->height, 0);
	return count;
}
EXPORT_SYMBOL_GPL(btree_visitor);

size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
			  unsigned long opaque,
			  void (*func)(void *elem, unsigned long opaque,
				       unsigned long *key,
				       size_t index, void *func2),
			  void *func2)
{
	size_t count = 0;

	if (!func2)
		func = empty;
	if (head->node)
		count = __btree_for_each(head, geo, head->node, opaque, func,
				func2, 1, head->height, 0);
	__btree_init(head);
	return count;
}
EXPORT_SYMBOL_GPL(btree_grim_visitor);

static int __init btree_module_init(void)
{
	btree_cachep = kmem_cache_create("btree_node", NODESIZE, 0,
			SLAB_HWCACHE_ALIGN, NULL);
	return 0;
}

static void __exit btree_module_exit(void)
{
	kmem_cache_destroy(btree_cachep);
}

/* If core code starts using btree, initialization should happen even earlier */
module_init(btree_module_init);
module_exit(btree_module_exit);

MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
MODULE_LICENSE("GPL");