Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  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
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
/*
 * Copyright (C) 2001 Momchil Velikov
 * Portions Copyright (C) 2001 Christoph Hellwig
 * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/radix-tree.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/bitops.h>


#ifdef __KERNEL__
#define RADIX_TREE_MAP_SHIFT	6
#else
#define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */
#endif
#define RADIX_TREE_TAGS		2

#define RADIX_TREE_MAP_SIZE	(1UL << RADIX_TREE_MAP_SHIFT)
#define RADIX_TREE_MAP_MASK	(RADIX_TREE_MAP_SIZE-1)

#define RADIX_TREE_TAG_LONGS	\
	((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)

struct radix_tree_node {
	unsigned int	count;
	void		*slots[RADIX_TREE_MAP_SIZE];
	unsigned long	tags[RADIX_TREE_TAGS][RADIX_TREE_TAG_LONGS];
};

struct radix_tree_path {
	struct radix_tree_node *node;
	int offset;
};

#define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)

static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;

/*
 * Radix tree node cache.
 */
static kmem_cache_t *radix_tree_node_cachep;

/*
 * Per-cpu pool of preloaded nodes
 */
struct radix_tree_preload {
	int nr;
	struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
};
DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };

/*
 * This assumes that the caller has performed appropriate preallocation, and
 * that the caller has pinned this thread of control to the current CPU.
 */
static struct radix_tree_node *
radix_tree_node_alloc(struct radix_tree_root *root)
{
	struct radix_tree_node *ret;

	ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
	if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
		struct radix_tree_preload *rtp;

		rtp = &__get_cpu_var(radix_tree_preloads);
		if (rtp->nr) {
			ret = rtp->nodes[rtp->nr - 1];
			rtp->nodes[rtp->nr - 1] = NULL;
			rtp->nr--;
		}
	}
	return ret;
}

static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
	kmem_cache_free(radix_tree_node_cachep, node);
}

/*
 * Load up this CPU's radix_tree_node buffer with sufficient objects to
 * ensure that the addition of a single element in the tree cannot fail.  On
 * success, return zero, with preemption disabled.  On error, return -ENOMEM
 * with preemption not disabled.
 */
int radix_tree_preload(gfp_t gfp_mask)
{
	struct radix_tree_preload *rtp;
	struct radix_tree_node *node;
	int ret = -ENOMEM;

	preempt_disable();
	rtp = &__get_cpu_var(radix_tree_preloads);
	while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
		preempt_enable();
		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
		if (node == NULL)
			goto out;
		preempt_disable();
		rtp = &__get_cpu_var(radix_tree_preloads);
		if (rtp->nr < ARRAY_SIZE(rtp->nodes))
			rtp->nodes[rtp->nr++] = node;
		else
			kmem_cache_free(radix_tree_node_cachep, node);
	}
	ret = 0;
out:
	return ret;
}

static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
{
	__set_bit(offset, node->tags[tag]);
}

static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
{
	__clear_bit(offset, node->tags[tag]);
}

static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
{
	return test_bit(offset, node->tags[tag]);
}

/*
 * Returns 1 if any slot in the node has this tag set.
 * Otherwise returns 0.
 */
static inline int any_tag_set(struct radix_tree_node *node, int tag)
{
	int idx;
	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
		if (node->tags[tag][idx])
			return 1;
	}
	return 0;
}

/*
 *	Return the maximum key which can be store into a
 *	radix tree with height HEIGHT.
 */
static inline unsigned long radix_tree_maxindex(unsigned int height)
{
	return height_to_maxindex[height];
}

/*
 *	Extend a radix tree so it can store key @index.
 */
static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
{
	struct radix_tree_node *node;
	unsigned int height;
	char tags[RADIX_TREE_TAGS];
	int tag;

	/* Figure out what the height should be.  */
	height = root->height + 1;
	while (index > radix_tree_maxindex(height))
		height++;

	if (root->rnode == NULL) {
		root->height = height;
		goto out;
	}

	/*
	 * Prepare the tag status of the top-level node for propagation
	 * into the newly-pushed top-level node(s)
	 */
	for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
		tags[tag] = 0;
		if (any_tag_set(root->rnode, tag))
			tags[tag] = 1;
	}

	do {
		if (!(node = radix_tree_node_alloc(root)))
			return -ENOMEM;

		/* Increase the height.  */
		node->slots[0] = root->rnode;

		/* Propagate the aggregated tag info into the new root */
		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
			if (tags[tag])
				tag_set(node, tag, 0);
		}

		node->count = 1;
		root->rnode = node;
		root->height++;
	} while (height > root->height);
out:
	return 0;
}

/**
 *	radix_tree_insert    -    insert into a radix tree
 *	@root:		radix tree root
 *	@index:		index key
 *	@item:		item to insert
 *
 *	Insert an item into the radix tree at position @index.
 */
int radix_tree_insert(struct radix_tree_root *root,
			unsigned long index, void *item)
{
	struct radix_tree_node *node = NULL, *slot;
	unsigned int height, shift;
	int offset;
	int error;

	/* Make sure the tree is high enough.  */
	if ((!index && !root->rnode) ||
			index > radix_tree_maxindex(root->height)) {
		error = radix_tree_extend(root, index);
		if (error)
			return error;
	}

	slot = root->rnode;
	height = root->height;
	shift = (height-1) * RADIX_TREE_MAP_SHIFT;

	offset = 0;			/* uninitialised var warning */
	do {
		if (slot == NULL) {
			/* Have to add a child node.  */
			if (!(slot = radix_tree_node_alloc(root)))
				return -ENOMEM;
			if (node) {
				node->slots[offset] = slot;
				node->count++;
			} else
				root->rnode = slot;
		}

		/* Go a level down */
		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
		node = slot;
		slot = node->slots[offset];
		shift -= RADIX_TREE_MAP_SHIFT;
		height--;
	} while (height > 0);

	if (slot != NULL)
		return -EEXIST;

	BUG_ON(!node);
	node->count++;
	node->slots[offset] = item;
	BUG_ON(tag_get(node, 0, offset));
	BUG_ON(tag_get(node, 1, offset));

	return 0;
}
EXPORT_SYMBOL(radix_tree_insert);

static inline void **__lookup_slot(struct radix_tree_root *root,
				   unsigned long index)
{
	unsigned int height, shift;
	struct radix_tree_node **slot;

	height = root->height;
	if (index > radix_tree_maxindex(height))
		return NULL;

	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
	slot = &root->rnode;

	while (height > 0) {
		if (*slot == NULL)
			return NULL;

		slot = (struct radix_tree_node **)
			((*slot)->slots +
				((index >> shift) & RADIX_TREE_MAP_MASK));
		shift -= RADIX_TREE_MAP_SHIFT;
		height--;
	}

	return (void **)slot;
}

/**
 *	radix_tree_lookup_slot    -    lookup a slot in a radix tree
 *	@root:		radix tree root
 *	@index:		index key
 *
 *	Lookup the slot corresponding to the position @index in the radix tree
 *	@root. This is useful for update-if-exists operations.
 */
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
	return __lookup_slot(root, index);
}
EXPORT_SYMBOL(radix_tree_lookup_slot);

/**
 *	radix_tree_lookup    -    perform lookup operation on a radix tree
 *	@root:		radix tree root
 *	@index:		index key
 *
 *	Lookup the item at the position @index in the radix tree @root.
 */
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
	void **slot;

	slot = __lookup_slot(root, index);
	return slot != NULL ? *slot : NULL;
}
EXPORT_SYMBOL(radix_tree_lookup);

/**
 *	radix_tree_tag_set - set a tag on a radix tree node
 *	@root:		radix tree root
 *	@index:		index key
 *	@tag: 		tag index
 *
 *	Set the search tag corresponging to @index in the radix tree.  From
 *	the root all the way down to the leaf node.
 *
 *	Returns the address of the tagged item.   Setting a tag on a not-present
 *	item is a bug.
 */
void *radix_tree_tag_set(struct radix_tree_root *root,
			unsigned long index, int tag)
{
	unsigned int height, shift;
	struct radix_tree_node *slot;

	height = root->height;
	if (index > radix_tree_maxindex(height))
		return NULL;

	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
	slot = root->rnode;

	while (height > 0) {
		int offset;

		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
		if (!tag_get(slot, tag, offset))
			tag_set(slot, tag, offset);
		slot = slot->slots[offset];
		BUG_ON(slot == NULL);
		shift -= RADIX_TREE_MAP_SHIFT;
		height--;
	}

	return slot;
}
EXPORT_SYMBOL(radix_tree_tag_set);

/**
 *	radix_tree_tag_clear - clear a tag on a radix tree node
 *	@root:		radix tree root
 *	@index:		index key
 *	@tag: 		tag index
 *
 *	Clear the search tag corresponging to @index in the radix tree.  If
 *	this causes the leaf node to have no tags set then clear the tag in the
 *	next-to-leaf node, etc.
 *
 *	Returns the address of the tagged item on success, else NULL.  ie:
 *	has the same return value and semantics as radix_tree_lookup().
 */
void *radix_tree_tag_clear(struct radix_tree_root *root,
			unsigned long index, int tag)
{
	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
	struct radix_tree_node *slot;
	unsigned int height, shift;
	void *ret = NULL;

	height = root->height;
	if (index > radix_tree_maxindex(height))
		goto out;

	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
	pathp->node = NULL;
	slot = root->rnode;

	while (height > 0) {
		int offset;

		if (slot == NULL)
			goto out;

		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
		pathp[1].offset = offset;
		pathp[1].node = slot;
		slot = slot->slots[offset];
		pathp++;
		shift -= RADIX_TREE_MAP_SHIFT;
		height--;
	}

	ret = slot;
	if (ret == NULL)
		goto out;

	do {
		if (!tag_get(pathp->node, tag, pathp->offset))
			goto out;
		tag_clear(pathp->node, tag, pathp->offset);
		if (any_tag_set(pathp->node, tag))
			goto out;
		pathp--;
	} while (pathp->node);
out:
	return ret;
}
EXPORT_SYMBOL(radix_tree_tag_clear);

#ifndef __KERNEL__	/* Only the test harness uses this at present */
/**
 * radix_tree_tag_get - get a tag on a radix tree node
 * @root:		radix tree root
 * @index:		index key
 * @tag: 		tag index
 *
 * Return values:
 *
 *  0: tag not present
 *  1: tag present, set
 * -1: tag present, unset
 */
int radix_tree_tag_get(struct radix_tree_root *root,
			unsigned long index, int tag)
{
	unsigned int height, shift;
	struct radix_tree_node *slot;
	int saw_unset_tag = 0;

	height = root->height;
	if (index > radix_tree_maxindex(height))
		return 0;

	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
	slot = root->rnode;

	for ( ; ; ) {
		int offset;

		if (slot == NULL)
			return 0;

		offset = (index >> shift) & RADIX_TREE_MAP_MASK;

		/*
		 * This is just a debug check.  Later, we can bale as soon as
		 * we see an unset tag.
		 */
		if (!tag_get(slot, tag, offset))
			saw_unset_tag = 1;
		if (height == 1) {
			int ret = tag_get(slot, tag, offset);

			BUG_ON(ret && saw_unset_tag);
			return ret ? 1 : -1;
		}
		slot = slot->slots[offset];
		shift -= RADIX_TREE_MAP_SHIFT;
		height--;
	}
}
EXPORT_SYMBOL(radix_tree_tag_get);
#endif

static unsigned int
__lookup(struct radix_tree_root *root, void **results, unsigned long index,
	unsigned int max_items, unsigned long *next_index)
{
	unsigned int nr_found = 0;
	unsigned int shift, height;
	struct radix_tree_node *slot;
	unsigned long i;

	height = root->height;
	if (height == 0)
		goto out;

	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
	slot = root->rnode;

	for ( ; height > 1; height--) {

		for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
				i < RADIX_TREE_MAP_SIZE; i++) {
			if (slot->slots[i] != NULL)
				break;
			index &= ~((1UL << shift) - 1);
			index += 1UL << shift;
			if (index == 0)
				goto out;	/* 32-bit wraparound */
		}
		if (i == RADIX_TREE_MAP_SIZE)
			goto out;

		shift -= RADIX_TREE_MAP_SHIFT;
		slot = slot->slots[i];
	}

	/* Bottom level: grab some items */
	for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
		index++;
		if (slot->slots[i]) {
			results[nr_found++] = slot->slots[i];
			if (nr_found == max_items)
				goto out;
		}
	}
out:
	*next_index = index;
	return nr_found;
}

/**
 *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
 *	@root:		radix tree root
 *	@results:	where the results of the lookup are placed
 *	@first_index:	start the lookup from this key
 *	@max_items:	place up to this many items at *results
 *
 *	Performs an index-ascending scan of the tree for present items.  Places
 *	them at *@results and returns the number of items which were placed at
 *	*@results.
 *
 *	The implementation is naive.
 */
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
			unsigned long first_index, unsigned int max_items)
{
	const unsigned long max_index = radix_tree_maxindex(root->height);
	unsigned long cur_index = first_index;
	unsigned int ret = 0;

	while (ret < max_items) {
		unsigned int nr_found;
		unsigned long next_index;	/* Index of next search */

		if (cur_index > max_index)
			break;
		nr_found = __lookup(root, results + ret, cur_index,
					max_items - ret, &next_index);
		ret += nr_found;
		if (next_index == 0)
			break;
		cur_index = next_index;
	}
	return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup);

/*
 * FIXME: the two tag_get()s here should use find_next_bit() instead of
 * open-coding the search.
 */
static unsigned int
__lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
	unsigned int max_items, unsigned long *next_index, int tag)
{
	unsigned int nr_found = 0;
	unsigned int shift;
	unsigned int height = root->height;
	struct radix_tree_node *slot;

	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
	slot = root->rnode;

	while (height > 0) {
		unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;

		for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
			if (tag_get(slot, tag, i)) {
				BUG_ON(slot->slots[i] == NULL);
				break;
			}
			index &= ~((1UL << shift) - 1);
			index += 1UL << shift;
			if (index == 0)
				goto out;	/* 32-bit wraparound */
		}
		if (i == RADIX_TREE_MAP_SIZE)
			goto out;
		height--;
		if (height == 0) {	/* Bottom level: grab some items */
			unsigned long j = index & RADIX_TREE_MAP_MASK;

			for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
				index++;
				if (tag_get(slot, tag, j)) {
					BUG_ON(slot->slots[j] == NULL);
					results[nr_found++] = slot->slots[j];
					if (nr_found == max_items)
						goto out;
				}
			}
		}
		shift -= RADIX_TREE_MAP_SHIFT;
		slot = slot->slots[i];
	}
out:
	*next_index = index;
	return nr_found;
}

/**
 *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 *	                             based on a tag
 *	@root:		radix tree root
 *	@results:	where the results of the lookup are placed
 *	@first_index:	start the lookup from this key
 *	@max_items:	place up to this many items at *results
 *	@tag:		the tag index
 *
 *	Performs an index-ascending scan of the tree for present items which
 *	have the tag indexed by @tag set.  Places the items at *@results and
 *	returns the number of items which were placed at *@results.
 */
unsigned int
radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
		unsigned long first_index, unsigned int max_items, int tag)
{
	const unsigned long max_index = radix_tree_maxindex(root->height);
	unsigned long cur_index = first_index;
	unsigned int ret = 0;

	while (ret < max_items) {
		unsigned int nr_found;
		unsigned long next_index;	/* Index of next search */

		if (cur_index > max_index)
			break;
		nr_found = __lookup_tag(root, results + ret, cur_index,
					max_items - ret, &next_index, tag);
		ret += nr_found;
		if (next_index == 0)
			break;
		cur_index = next_index;
	}
	return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);

/**
 *	radix_tree_shrink    -    shrink height of a radix tree to minimal
 *	@root		radix tree root
 */
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
	/* try to shrink tree height */
	while (root->height > 1 &&
			root->rnode->count == 1 &&
			root->rnode->slots[0]) {
		struct radix_tree_node *to_free = root->rnode;

		root->rnode = to_free->slots[0];
		root->height--;
		/* must only free zeroed nodes into the slab */
		tag_clear(to_free, 0, 0);
		tag_clear(to_free, 1, 0);
		to_free->slots[0] = NULL;
		to_free->count = 0;
		radix_tree_node_free(to_free);
	}
}

/**
 *	radix_tree_delete    -    delete an item from a radix tree
 *	@root:		radix tree root
 *	@index:		index key
 *
 *	Remove the item at @index from the radix tree rooted at @root.
 *
 *	Returns the address of the deleted item, or NULL if it was not present.
 */
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
	struct radix_tree_path *orig_pathp;
	struct radix_tree_node *slot;
	unsigned int height, shift;
	void *ret = NULL;
	char tags[RADIX_TREE_TAGS];
	int nr_cleared_tags;
	int tag;
	int offset;

	height = root->height;
	if (index > radix_tree_maxindex(height))
		goto out;

	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
	pathp->node = NULL;
	slot = root->rnode;

	for ( ; height > 0; height--) {
		if (slot == NULL)
			goto out;

		pathp++;
		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
		pathp->offset = offset;
		pathp->node = slot;
		slot = slot->slots[offset];
		shift -= RADIX_TREE_MAP_SHIFT;
	}

	ret = slot;
	if (ret == NULL)
		goto out;

	orig_pathp = pathp;

	/*
	 * Clear all tags associated with the just-deleted item
	 */
	nr_cleared_tags = 0;
	for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
		tags[tag] = 1;
		if (tag_get(pathp->node, tag, pathp->offset)) {
			tag_clear(pathp->node, tag, pathp->offset);
			if (!any_tag_set(pathp->node, tag)) {
				tags[tag] = 0;
				nr_cleared_tags++;
			}
		}
	}

	for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
			if (tags[tag])
				continue;

			tag_clear(pathp->node, tag, pathp->offset);
			if (any_tag_set(pathp->node, tag)) {
				tags[tag] = 1;
				nr_cleared_tags--;
			}
		}
	}

	/* Now free the nodes we do not need anymore */
	for (pathp = orig_pathp; pathp->node; pathp--) {
		pathp->node->slots[pathp->offset] = NULL;
		pathp->node->count--;

		if (pathp->node->count) {
			if (pathp->node == root->rnode)
				radix_tree_shrink(root);
			goto out;
		}

		/* Node with zero slots in use so free it */
		radix_tree_node_free(pathp->node);
	}
	root->rnode = NULL;
	root->height = 0;
out:
	return ret;
}
EXPORT_SYMBOL(radix_tree_delete);

/**
 *	radix_tree_tagged - test whether any items in the tree are tagged
 *	@root:		radix tree root
 *	@tag:		tag to test
 */
int radix_tree_tagged(struct radix_tree_root *root, int tag)
{
  	struct radix_tree_node *rnode;
  	rnode = root->rnode;
  	if (!rnode)
  		return 0;
	return any_tag_set(rnode, tag);
}
EXPORT_SYMBOL(radix_tree_tagged);

static void
radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
{
	memset(node, 0, sizeof(struct radix_tree_node));
}

static __init unsigned long __maxindex(unsigned int height)
{
	unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
	unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;

	if (tmp >= RADIX_TREE_INDEX_BITS)
		index = ~0UL;
	return index;
}

static __init void radix_tree_init_maxindex(void)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
		height_to_maxindex[i] = __maxindex(i);
}

#ifdef CONFIG_HOTPLUG_CPU
static int radix_tree_callback(struct notifier_block *nfb,
                            unsigned long action,
                            void *hcpu)
{
       int cpu = (long)hcpu;
       struct radix_tree_preload *rtp;

       /* Free per-cpu pool of perloaded nodes */
       if (action == CPU_DEAD) {
               rtp = &per_cpu(radix_tree_preloads, cpu);
               while (rtp->nr) {
                       kmem_cache_free(radix_tree_node_cachep,
                                       rtp->nodes[rtp->nr-1]);
                       rtp->nodes[rtp->nr-1] = NULL;
                       rtp->nr--;
               }
       }
       return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */

void __init radix_tree_init(void)
{
	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
			sizeof(struct radix_tree_node), 0,
			SLAB_PANIC, radix_tree_node_ctor, NULL);
	radix_tree_init_maxindex();
	hotcpu_notifier(radix_tree_callback, 0);
}