xref: /openbmc/linux/lib/radix-tree.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * Copyright (C) 2001 Momchil Velikov
3  * Portions Copyright (C) 2001 Christoph Hellwig
4  * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as
8  * published by the Free Software Foundation; either version 2, or (at
9  * your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful, but
12  * WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14  * General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19  */
20 
21 #include <linux/errno.h>
22 #include <linux/init.h>
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/radix-tree.h>
26 #include <linux/percpu.h>
27 #include <linux/slab.h>
28 #include <linux/notifier.h>
29 #include <linux/cpu.h>
30 #include <linux/gfp.h>
31 #include <linux/string.h>
32 #include <linux/bitops.h>
33 
34 
35 #ifdef __KERNEL__
36 #define RADIX_TREE_MAP_SHIFT	6
37 #else
38 #define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */
39 #endif
40 #define RADIX_TREE_TAGS		2
41 
42 #define RADIX_TREE_MAP_SIZE	(1UL << RADIX_TREE_MAP_SHIFT)
43 #define RADIX_TREE_MAP_MASK	(RADIX_TREE_MAP_SIZE-1)
44 
45 #define RADIX_TREE_TAG_LONGS	\
46 	((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
47 
48 struct radix_tree_node {
49 	unsigned int	count;
50 	void		*slots[RADIX_TREE_MAP_SIZE];
51 	unsigned long	tags[RADIX_TREE_TAGS][RADIX_TREE_TAG_LONGS];
52 };
53 
54 struct radix_tree_path {
55 	struct radix_tree_node *node;
56 	int offset;
57 };
58 
59 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
60 #define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
61 
62 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
63 
64 /*
65  * Radix tree node cache.
66  */
67 static kmem_cache_t *radix_tree_node_cachep;
68 
69 /*
70  * Per-cpu pool of preloaded nodes
71  */
72 struct radix_tree_preload {
73 	int nr;
74 	struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
75 };
76 DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
77 
78 /*
79  * This assumes that the caller has performed appropriate preallocation, and
80  * that the caller has pinned this thread of control to the current CPU.
81  */
82 static struct radix_tree_node *
83 radix_tree_node_alloc(struct radix_tree_root *root)
84 {
85 	struct radix_tree_node *ret;
86 
87 	ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
88 	if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
89 		struct radix_tree_preload *rtp;
90 
91 		rtp = &__get_cpu_var(radix_tree_preloads);
92 		if (rtp->nr) {
93 			ret = rtp->nodes[rtp->nr - 1];
94 			rtp->nodes[rtp->nr - 1] = NULL;
95 			rtp->nr--;
96 		}
97 	}
98 	return ret;
99 }
100 
101 static inline void
102 radix_tree_node_free(struct radix_tree_node *node)
103 {
104 	kmem_cache_free(radix_tree_node_cachep, node);
105 }
106 
107 /*
108  * Load up this CPU's radix_tree_node buffer with sufficient objects to
109  * ensure that the addition of a single element in the tree cannot fail.  On
110  * success, return zero, with preemption disabled.  On error, return -ENOMEM
111  * with preemption not disabled.
112  */
113 int radix_tree_preload(gfp_t gfp_mask)
114 {
115 	struct radix_tree_preload *rtp;
116 	struct radix_tree_node *node;
117 	int ret = -ENOMEM;
118 
119 	preempt_disable();
120 	rtp = &__get_cpu_var(radix_tree_preloads);
121 	while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
122 		preempt_enable();
123 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
124 		if (node == NULL)
125 			goto out;
126 		preempt_disable();
127 		rtp = &__get_cpu_var(radix_tree_preloads);
128 		if (rtp->nr < ARRAY_SIZE(rtp->nodes))
129 			rtp->nodes[rtp->nr++] = node;
130 		else
131 			kmem_cache_free(radix_tree_node_cachep, node);
132 	}
133 	ret = 0;
134 out:
135 	return ret;
136 }
137 
138 static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
139 {
140 	if (!test_bit(offset, &node->tags[tag][0]))
141 		__set_bit(offset, &node->tags[tag][0]);
142 }
143 
144 static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
145 {
146 	__clear_bit(offset, &node->tags[tag][0]);
147 }
148 
149 static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
150 {
151 	return test_bit(offset, &node->tags[tag][0]);
152 }
153 
154 /*
155  *	Return the maximum key which can be store into a
156  *	radix tree with height HEIGHT.
157  */
158 static inline unsigned long radix_tree_maxindex(unsigned int height)
159 {
160 	return height_to_maxindex[height];
161 }
162 
163 /*
164  *	Extend a radix tree so it can store key @index.
165  */
166 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
167 {
168 	struct radix_tree_node *node;
169 	unsigned int height;
170 	char tags[RADIX_TREE_TAGS];
171 	int tag;
172 
173 	/* Figure out what the height should be.  */
174 	height = root->height + 1;
175 	while (index > radix_tree_maxindex(height))
176 		height++;
177 
178 	if (root->rnode == NULL) {
179 		root->height = height;
180 		goto out;
181 	}
182 
183 	/*
184 	 * Prepare the tag status of the top-level node for propagation
185 	 * into the newly-pushed top-level node(s)
186 	 */
187 	for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
188 		int idx;
189 
190 		tags[tag] = 0;
191 		for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
192 			if (root->rnode->tags[tag][idx]) {
193 				tags[tag] = 1;
194 				break;
195 			}
196 		}
197 	}
198 
199 	do {
200 		if (!(node = radix_tree_node_alloc(root)))
201 			return -ENOMEM;
202 
203 		/* Increase the height.  */
204 		node->slots[0] = root->rnode;
205 
206 		/* Propagate the aggregated tag info into the new root */
207 		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
208 			if (tags[tag])
209 				tag_set(node, tag, 0);
210 		}
211 
212 		node->count = 1;
213 		root->rnode = node;
214 		root->height++;
215 	} while (height > root->height);
216 out:
217 	return 0;
218 }
219 
220 /**
221  *	radix_tree_insert    -    insert into a radix tree
222  *	@root:		radix tree root
223  *	@index:		index key
224  *	@item:		item to insert
225  *
226  *	Insert an item into the radix tree at position @index.
227  */
228 int radix_tree_insert(struct radix_tree_root *root,
229 			unsigned long index, void *item)
230 {
231 	struct radix_tree_node *node = NULL, *slot;
232 	unsigned int height, shift;
233 	int offset;
234 	int error;
235 
236 	/* Make sure the tree is high enough.  */
237 	if ((!index && !root->rnode) ||
238 			index > radix_tree_maxindex(root->height)) {
239 		error = radix_tree_extend(root, index);
240 		if (error)
241 			return error;
242 	}
243 
244 	slot = root->rnode;
245 	height = root->height;
246 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
247 
248 	offset = 0;			/* uninitialised var warning */
249 	while (height > 0) {
250 		if (slot == NULL) {
251 			/* Have to add a child node.  */
252 			if (!(slot = radix_tree_node_alloc(root)))
253 				return -ENOMEM;
254 			if (node) {
255 				node->slots[offset] = slot;
256 				node->count++;
257 			} else
258 				root->rnode = slot;
259 		}
260 
261 		/* Go a level down */
262 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
263 		node = slot;
264 		slot = node->slots[offset];
265 		shift -= RADIX_TREE_MAP_SHIFT;
266 		height--;
267 	}
268 
269 	if (slot != NULL)
270 		return -EEXIST;
271 
272 	if (node) {
273 		node->count++;
274 		node->slots[offset] = item;
275 		BUG_ON(tag_get(node, 0, offset));
276 		BUG_ON(tag_get(node, 1, offset));
277 	} else
278 		root->rnode = item;
279 
280 	return 0;
281 }
282 EXPORT_SYMBOL(radix_tree_insert);
283 
284 /**
285  *	radix_tree_lookup    -    perform lookup operation on a radix tree
286  *	@root:		radix tree root
287  *	@index:		index key
288  *
289  *	Lookup the item at the position @index in the radix tree @root.
290  */
291 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
292 {
293 	unsigned int height, shift;
294 	struct radix_tree_node *slot;
295 
296 	height = root->height;
297 	if (index > radix_tree_maxindex(height))
298 		return NULL;
299 
300 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
301 	slot = root->rnode;
302 
303 	while (height > 0) {
304 		if (slot == NULL)
305 			return NULL;
306 
307 		slot = slot->slots[(index >> shift) & RADIX_TREE_MAP_MASK];
308 		shift -= RADIX_TREE_MAP_SHIFT;
309 		height--;
310 	}
311 
312 	return slot;
313 }
314 EXPORT_SYMBOL(radix_tree_lookup);
315 
316 /**
317  *	radix_tree_tag_set - set a tag on a radix tree node
318  *	@root:		radix tree root
319  *	@index:		index key
320  *	@tag: 		tag index
321  *
322  *	Set the search tag corresponging to @index in the radix tree.  From
323  *	the root all the way down to the leaf node.
324  *
325  *	Returns the address of the tagged item.   Setting a tag on a not-present
326  *	item is a bug.
327  */
328 void *radix_tree_tag_set(struct radix_tree_root *root,
329 			unsigned long index, int tag)
330 {
331 	unsigned int height, shift;
332 	struct radix_tree_node *slot;
333 
334 	height = root->height;
335 	if (index > radix_tree_maxindex(height))
336 		return NULL;
337 
338 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
339 	slot = root->rnode;
340 
341 	while (height > 0) {
342 		int offset;
343 
344 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
345 		tag_set(slot, tag, offset);
346 		slot = slot->slots[offset];
347 		BUG_ON(slot == NULL);
348 		shift -= RADIX_TREE_MAP_SHIFT;
349 		height--;
350 	}
351 
352 	return slot;
353 }
354 EXPORT_SYMBOL(radix_tree_tag_set);
355 
356 /**
357  *	radix_tree_tag_clear - clear a tag on a radix tree node
358  *	@root:		radix tree root
359  *	@index:		index key
360  *	@tag: 		tag index
361  *
362  *	Clear the search tag corresponging to @index in the radix tree.  If
363  *	this causes the leaf node to have no tags set then clear the tag in the
364  *	next-to-leaf node, etc.
365  *
366  *	Returns the address of the tagged item on success, else NULL.  ie:
367  *	has the same return value and semantics as radix_tree_lookup().
368  */
369 void *radix_tree_tag_clear(struct radix_tree_root *root,
370 			unsigned long index, int tag)
371 {
372 	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
373 	struct radix_tree_node *slot;
374 	unsigned int height, shift;
375 	void *ret = NULL;
376 
377 	height = root->height;
378 	if (index > radix_tree_maxindex(height))
379 		goto out;
380 
381 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
382 	pathp->node = NULL;
383 	slot = root->rnode;
384 
385 	while (height > 0) {
386 		int offset;
387 
388 		if (slot == NULL)
389 			goto out;
390 
391 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
392 		pathp[1].offset = offset;
393 		pathp[1].node = slot;
394 		slot = slot->slots[offset];
395 		pathp++;
396 		shift -= RADIX_TREE_MAP_SHIFT;
397 		height--;
398 	}
399 
400 	ret = slot;
401 	if (ret == NULL)
402 		goto out;
403 
404 	do {
405 		int idx;
406 
407 		tag_clear(pathp->node, tag, pathp->offset);
408 		for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
409 			if (pathp->node->tags[tag][idx])
410 				goto out;
411 		}
412 		pathp--;
413 	} while (pathp->node);
414 out:
415 	return ret;
416 }
417 EXPORT_SYMBOL(radix_tree_tag_clear);
418 
419 #ifndef __KERNEL__	/* Only the test harness uses this at present */
420 /**
421  * radix_tree_tag_get - get a tag on a radix tree node
422  * @root:		radix tree root
423  * @index:		index key
424  * @tag: 		tag index
425  *
426  * Return values:
427  *
428  *  0: tag not present
429  *  1: tag present, set
430  * -1: tag present, unset
431  */
432 int radix_tree_tag_get(struct radix_tree_root *root,
433 			unsigned long index, int tag)
434 {
435 	unsigned int height, shift;
436 	struct radix_tree_node *slot;
437 	int saw_unset_tag = 0;
438 
439 	height = root->height;
440 	if (index > radix_tree_maxindex(height))
441 		return 0;
442 
443 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
444 	slot = root->rnode;
445 
446 	for ( ; ; ) {
447 		int offset;
448 
449 		if (slot == NULL)
450 			return 0;
451 
452 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
453 
454 		/*
455 		 * This is just a debug check.  Later, we can bale as soon as
456 		 * we see an unset tag.
457 		 */
458 		if (!tag_get(slot, tag, offset))
459 			saw_unset_tag = 1;
460 		if (height == 1) {
461 			int ret = tag_get(slot, tag, offset);
462 
463 			BUG_ON(ret && saw_unset_tag);
464 			return ret ? 1 : -1;
465 		}
466 		slot = slot->slots[offset];
467 		shift -= RADIX_TREE_MAP_SHIFT;
468 		height--;
469 	}
470 }
471 EXPORT_SYMBOL(radix_tree_tag_get);
472 #endif
473 
474 static unsigned int
475 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
476 	unsigned int max_items, unsigned long *next_index)
477 {
478 	unsigned int nr_found = 0;
479 	unsigned int shift, height;
480 	struct radix_tree_node *slot;
481 	unsigned long i;
482 
483 	height = root->height;
484 	if (height == 0)
485 		goto out;
486 
487 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
488 	slot = root->rnode;
489 
490 	for ( ; height > 1; height--) {
491 
492 		for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
493 				i < RADIX_TREE_MAP_SIZE; i++) {
494 			if (slot->slots[i] != NULL)
495 				break;
496 			index &= ~((1UL << shift) - 1);
497 			index += 1UL << shift;
498 			if (index == 0)
499 				goto out;	/* 32-bit wraparound */
500 		}
501 		if (i == RADIX_TREE_MAP_SIZE)
502 			goto out;
503 
504 		shift -= RADIX_TREE_MAP_SHIFT;
505 		slot = slot->slots[i];
506 	}
507 
508 	/* Bottom level: grab some items */
509 	for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
510 		index++;
511 		if (slot->slots[i]) {
512 			results[nr_found++] = slot->slots[i];
513 			if (nr_found == max_items)
514 				goto out;
515 		}
516 	}
517 out:
518 	*next_index = index;
519 	return nr_found;
520 }
521 
522 /**
523  *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
524  *	@root:		radix tree root
525  *	@results:	where the results of the lookup are placed
526  *	@first_index:	start the lookup from this key
527  *	@max_items:	place up to this many items at *results
528  *
529  *	Performs an index-ascending scan of the tree for present items.  Places
530  *	them at *@results and returns the number of items which were placed at
531  *	*@results.
532  *
533  *	The implementation is naive.
534  */
535 unsigned int
536 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
537 			unsigned long first_index, unsigned int max_items)
538 {
539 	const unsigned long max_index = radix_tree_maxindex(root->height);
540 	unsigned long cur_index = first_index;
541 	unsigned int ret = 0;
542 
543 	while (ret < max_items) {
544 		unsigned int nr_found;
545 		unsigned long next_index;	/* Index of next search */
546 
547 		if (cur_index > max_index)
548 			break;
549 		nr_found = __lookup(root, results + ret, cur_index,
550 					max_items - ret, &next_index);
551 		ret += nr_found;
552 		if (next_index == 0)
553 			break;
554 		cur_index = next_index;
555 	}
556 	return ret;
557 }
558 EXPORT_SYMBOL(radix_tree_gang_lookup);
559 
560 /*
561  * FIXME: the two tag_get()s here should use find_next_bit() instead of
562  * open-coding the search.
563  */
564 static unsigned int
565 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
566 	unsigned int max_items, unsigned long *next_index, int tag)
567 {
568 	unsigned int nr_found = 0;
569 	unsigned int shift;
570 	unsigned int height = root->height;
571 	struct radix_tree_node *slot;
572 
573 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
574 	slot = root->rnode;
575 
576 	while (height > 0) {
577 		unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
578 
579 		for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
580 			if (tag_get(slot, tag, i)) {
581 				BUG_ON(slot->slots[i] == NULL);
582 				break;
583 			}
584 			index &= ~((1UL << shift) - 1);
585 			index += 1UL << shift;
586 			if (index == 0)
587 				goto out;	/* 32-bit wraparound */
588 		}
589 		if (i == RADIX_TREE_MAP_SIZE)
590 			goto out;
591 		height--;
592 		if (height == 0) {	/* Bottom level: grab some items */
593 			unsigned long j = index & RADIX_TREE_MAP_MASK;
594 
595 			for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
596 				index++;
597 				if (tag_get(slot, tag, j)) {
598 					BUG_ON(slot->slots[j] == NULL);
599 					results[nr_found++] = slot->slots[j];
600 					if (nr_found == max_items)
601 						goto out;
602 				}
603 			}
604 		}
605 		shift -= RADIX_TREE_MAP_SHIFT;
606 		slot = slot->slots[i];
607 	}
608 out:
609 	*next_index = index;
610 	return nr_found;
611 }
612 
613 /**
614  *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
615  *	                             based on a tag
616  *	@root:		radix tree root
617  *	@results:	where the results of the lookup are placed
618  *	@first_index:	start the lookup from this key
619  *	@max_items:	place up to this many items at *results
620  *	@tag:		the tag index
621  *
622  *	Performs an index-ascending scan of the tree for present items which
623  *	have the tag indexed by @tag set.  Places the items at *@results and
624  *	returns the number of items which were placed at *@results.
625  */
626 unsigned int
627 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
628 		unsigned long first_index, unsigned int max_items, int tag)
629 {
630 	const unsigned long max_index = radix_tree_maxindex(root->height);
631 	unsigned long cur_index = first_index;
632 	unsigned int ret = 0;
633 
634 	while (ret < max_items) {
635 		unsigned int nr_found;
636 		unsigned long next_index;	/* Index of next search */
637 
638 		if (cur_index > max_index)
639 			break;
640 		nr_found = __lookup_tag(root, results + ret, cur_index,
641 					max_items - ret, &next_index, tag);
642 		ret += nr_found;
643 		if (next_index == 0)
644 			break;
645 		cur_index = next_index;
646 	}
647 	return ret;
648 }
649 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
650 
651 /**
652  *	radix_tree_delete    -    delete an item from a radix tree
653  *	@root:		radix tree root
654  *	@index:		index key
655  *
656  *	Remove the item at @index from the radix tree rooted at @root.
657  *
658  *	Returns the address of the deleted item, or NULL if it was not present.
659  */
660 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
661 {
662 	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
663 	struct radix_tree_path *orig_pathp;
664 	struct radix_tree_node *slot;
665 	unsigned int height, shift;
666 	void *ret = NULL;
667 	char tags[RADIX_TREE_TAGS];
668 	int nr_cleared_tags;
669 
670 	height = root->height;
671 	if (index > radix_tree_maxindex(height))
672 		goto out;
673 
674 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
675 	pathp->node = NULL;
676 	slot = root->rnode;
677 
678 	for ( ; height > 0; height--) {
679 		int offset;
680 
681 		if (slot == NULL)
682 			goto out;
683 
684 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
685 		pathp[1].offset = offset;
686 		pathp[1].node = slot;
687 		slot = slot->slots[offset];
688 		pathp++;
689 		shift -= RADIX_TREE_MAP_SHIFT;
690 	}
691 
692 	ret = slot;
693 	if (ret == NULL)
694 		goto out;
695 
696 	orig_pathp = pathp;
697 
698 	/*
699 	 * Clear all tags associated with the just-deleted item
700 	 */
701 	memset(tags, 0, sizeof(tags));
702 	do {
703 		int tag;
704 
705 		nr_cleared_tags = RADIX_TREE_TAGS;
706 		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
707 			int idx;
708 
709 			if (tags[tag])
710 				continue;
711 
712 			tag_clear(pathp->node, tag, pathp->offset);
713 
714 			for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
715 				if (pathp->node->tags[tag][idx]) {
716 					tags[tag] = 1;
717 					nr_cleared_tags--;
718 					break;
719 				}
720 			}
721 		}
722 		pathp--;
723 	} while (pathp->node && nr_cleared_tags);
724 
725 	/* Now free the nodes we do not need anymore */
726 	for (pathp = orig_pathp; pathp->node; pathp--) {
727 		pathp->node->slots[pathp->offset] = NULL;
728 		if (--pathp->node->count)
729 			goto out;
730 
731 		/* Node with zero slots in use so free it */
732 		radix_tree_node_free(pathp->node);
733 	}
734 	root->rnode = NULL;
735 	root->height = 0;
736 out:
737 	return ret;
738 }
739 EXPORT_SYMBOL(radix_tree_delete);
740 
741 /**
742  *	radix_tree_tagged - test whether any items in the tree are tagged
743  *	@root:		radix tree root
744  *	@tag:		tag to test
745  */
746 int radix_tree_tagged(struct radix_tree_root *root, int tag)
747 {
748 	int idx;
749 
750 	if (!root->rnode)
751 		return 0;
752 	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
753 		if (root->rnode->tags[tag][idx])
754 			return 1;
755 	}
756 	return 0;
757 }
758 EXPORT_SYMBOL(radix_tree_tagged);
759 
760 static void
761 radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
762 {
763 	memset(node, 0, sizeof(struct radix_tree_node));
764 }
765 
766 static __init unsigned long __maxindex(unsigned int height)
767 {
768 	unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
769 	unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
770 
771 	if (tmp >= RADIX_TREE_INDEX_BITS)
772 		index = ~0UL;
773 	return index;
774 }
775 
776 static __init void radix_tree_init_maxindex(void)
777 {
778 	unsigned int i;
779 
780 	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
781 		height_to_maxindex[i] = __maxindex(i);
782 }
783 
784 #ifdef CONFIG_HOTPLUG_CPU
785 static int radix_tree_callback(struct notifier_block *nfb,
786                             unsigned long action,
787                             void *hcpu)
788 {
789        int cpu = (long)hcpu;
790        struct radix_tree_preload *rtp;
791 
792        /* Free per-cpu pool of perloaded nodes */
793        if (action == CPU_DEAD) {
794                rtp = &per_cpu(radix_tree_preloads, cpu);
795                while (rtp->nr) {
796                        kmem_cache_free(radix_tree_node_cachep,
797                                        rtp->nodes[rtp->nr-1]);
798                        rtp->nodes[rtp->nr-1] = NULL;
799                        rtp->nr--;
800                }
801        }
802        return NOTIFY_OK;
803 }
804 #endif /* CONFIG_HOTPLUG_CPU */
805 
806 void __init radix_tree_init(void)
807 {
808 	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
809 			sizeof(struct radix_tree_node), 0,
810 			SLAB_PANIC, radix_tree_node_ctor, NULL);
811 	radix_tree_init_maxindex();
812 	hotcpu_notifier(radix_tree_callback, 0);
813 }
814