xref: /openbmc/linux/lib/radix-tree.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
1 /*
2  * Copyright (C) 2001 Momchil Velikov
3  * Portions Copyright (C) 2001 Christoph Hellwig
4  * Copyright (C) 2005 SGI, Christoph Lameter
5  * Copyright (C) 2006 Nick Piggin
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License as
9  * published by the Free Software Foundation; either version 2, or (at
10  * your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful, but
13  * WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15  * General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20  */
21 
22 #include <linux/errno.h>
23 #include <linux/init.h>
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/radix-tree.h>
27 #include <linux/percpu.h>
28 #include <linux/slab.h>
29 #include <linux/notifier.h>
30 #include <linux/cpu.h>
31 #include <linux/gfp.h>
32 #include <linux/string.h>
33 #include <linux/bitops.h>
34 #include <linux/rcupdate.h>
35 
36 
37 #ifdef __KERNEL__
38 #define RADIX_TREE_MAP_SHIFT	(CONFIG_BASE_SMALL ? 4 : 6)
39 #else
40 #define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */
41 #endif
42 
43 #define RADIX_TREE_MAP_SIZE	(1UL << RADIX_TREE_MAP_SHIFT)
44 #define RADIX_TREE_MAP_MASK	(RADIX_TREE_MAP_SIZE-1)
45 
46 #define RADIX_TREE_TAG_LONGS	\
47 	((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
48 
49 struct radix_tree_node {
50 	unsigned int	height;		/* Height from the bottom */
51 	unsigned int	count;
52 	struct rcu_head	rcu_head;
53 	void		*slots[RADIX_TREE_MAP_SIZE];
54 	unsigned long	tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
55 };
56 
57 struct radix_tree_path {
58 	struct radix_tree_node *node;
59 	int offset;
60 };
61 
62 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
63 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
64 					  RADIX_TREE_MAP_SHIFT))
65 
66 /*
67  * The height_to_maxindex array needs to be one deeper than the maximum
68  * path as height 0 holds only 1 entry.
69  */
70 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
71 
72 /*
73  * Radix tree node cache.
74  */
75 static struct kmem_cache *radix_tree_node_cachep;
76 
77 /*
78  * Per-cpu pool of preloaded nodes
79  */
80 struct radix_tree_preload {
81 	int nr;
82 	struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
83 };
84 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
85 
86 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
87 {
88 	return root->gfp_mask & __GFP_BITS_MASK;
89 }
90 
91 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
92 		int offset)
93 {
94 	__set_bit(offset, node->tags[tag]);
95 }
96 
97 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
98 		int offset)
99 {
100 	__clear_bit(offset, node->tags[tag]);
101 }
102 
103 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
104 		int offset)
105 {
106 	return test_bit(offset, node->tags[tag]);
107 }
108 
109 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
110 {
111 	root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
112 }
113 
114 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
115 {
116 	root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
117 }
118 
119 static inline void root_tag_clear_all(struct radix_tree_root *root)
120 {
121 	root->gfp_mask &= __GFP_BITS_MASK;
122 }
123 
124 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
125 {
126 	return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
127 }
128 
129 /*
130  * Returns 1 if any slot in the node has this tag set.
131  * Otherwise returns 0.
132  */
133 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
134 {
135 	int idx;
136 	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
137 		if (node->tags[tag][idx])
138 			return 1;
139 	}
140 	return 0;
141 }
142 /*
143  * This assumes that the caller has performed appropriate preallocation, and
144  * that the caller has pinned this thread of control to the current CPU.
145  */
146 static struct radix_tree_node *
147 radix_tree_node_alloc(struct radix_tree_root *root)
148 {
149 	struct radix_tree_node *ret = NULL;
150 	gfp_t gfp_mask = root_gfp_mask(root);
151 
152 	if (!(gfp_mask & __GFP_WAIT)) {
153 		struct radix_tree_preload *rtp;
154 
155 		/*
156 		 * Provided the caller has preloaded here, we will always
157 		 * succeed in getting a node here (and never reach
158 		 * kmem_cache_alloc)
159 		 */
160 		rtp = &__get_cpu_var(radix_tree_preloads);
161 		if (rtp->nr) {
162 			ret = rtp->nodes[rtp->nr - 1];
163 			rtp->nodes[rtp->nr - 1] = NULL;
164 			rtp->nr--;
165 		}
166 	}
167 	if (ret == NULL)
168 		ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
169 
170 	BUG_ON(radix_tree_is_indirect_ptr(ret));
171 	return ret;
172 }
173 
174 static void radix_tree_node_rcu_free(struct rcu_head *head)
175 {
176 	struct radix_tree_node *node =
177 			container_of(head, struct radix_tree_node, rcu_head);
178 
179 	/*
180 	 * must only free zeroed nodes into the slab. radix_tree_shrink
181 	 * can leave us with a non-NULL entry in the first slot, so clear
182 	 * that here to make sure.
183 	 */
184 	tag_clear(node, 0, 0);
185 	tag_clear(node, 1, 0);
186 	node->slots[0] = NULL;
187 	node->count = 0;
188 
189 	kmem_cache_free(radix_tree_node_cachep, node);
190 }
191 
192 static inline void
193 radix_tree_node_free(struct radix_tree_node *node)
194 {
195 	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
196 }
197 
198 /*
199  * Load up this CPU's radix_tree_node buffer with sufficient objects to
200  * ensure that the addition of a single element in the tree cannot fail.  On
201  * success, return zero, with preemption disabled.  On error, return -ENOMEM
202  * with preemption not disabled.
203  *
204  * To make use of this facility, the radix tree must be initialised without
205  * __GFP_WAIT being passed to INIT_RADIX_TREE().
206  */
207 int radix_tree_preload(gfp_t gfp_mask)
208 {
209 	struct radix_tree_preload *rtp;
210 	struct radix_tree_node *node;
211 	int ret = -ENOMEM;
212 
213 	preempt_disable();
214 	rtp = &__get_cpu_var(radix_tree_preloads);
215 	while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
216 		preempt_enable();
217 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
218 		if (node == NULL)
219 			goto out;
220 		preempt_disable();
221 		rtp = &__get_cpu_var(radix_tree_preloads);
222 		if (rtp->nr < ARRAY_SIZE(rtp->nodes))
223 			rtp->nodes[rtp->nr++] = node;
224 		else
225 			kmem_cache_free(radix_tree_node_cachep, node);
226 	}
227 	ret = 0;
228 out:
229 	return ret;
230 }
231 EXPORT_SYMBOL(radix_tree_preload);
232 
233 /*
234  *	Return the maximum key which can be store into a
235  *	radix tree with height HEIGHT.
236  */
237 static inline unsigned long radix_tree_maxindex(unsigned int height)
238 {
239 	return height_to_maxindex[height];
240 }
241 
242 /*
243  *	Extend a radix tree so it can store key @index.
244  */
245 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
246 {
247 	struct radix_tree_node *node;
248 	unsigned int height;
249 	int tag;
250 
251 	/* Figure out what the height should be.  */
252 	height = root->height + 1;
253 	while (index > radix_tree_maxindex(height))
254 		height++;
255 
256 	if (root->rnode == NULL) {
257 		root->height = height;
258 		goto out;
259 	}
260 
261 	do {
262 		unsigned int newheight;
263 		if (!(node = radix_tree_node_alloc(root)))
264 			return -ENOMEM;
265 
266 		/* Increase the height.  */
267 		node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
268 
269 		/* Propagate the aggregated tag info into the new root */
270 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
271 			if (root_tag_get(root, tag))
272 				tag_set(node, tag, 0);
273 		}
274 
275 		newheight = root->height+1;
276 		node->height = newheight;
277 		node->count = 1;
278 		node = radix_tree_ptr_to_indirect(node);
279 		rcu_assign_pointer(root->rnode, node);
280 		root->height = newheight;
281 	} while (height > root->height);
282 out:
283 	return 0;
284 }
285 
286 /**
287  *	radix_tree_insert    -    insert into a radix tree
288  *	@root:		radix tree root
289  *	@index:		index key
290  *	@item:		item to insert
291  *
292  *	Insert an item into the radix tree at position @index.
293  */
294 int radix_tree_insert(struct radix_tree_root *root,
295 			unsigned long index, void *item)
296 {
297 	struct radix_tree_node *node = NULL, *slot;
298 	unsigned int height, shift;
299 	int offset;
300 	int error;
301 
302 	BUG_ON(radix_tree_is_indirect_ptr(item));
303 
304 	/* Make sure the tree is high enough.  */
305 	if (index > radix_tree_maxindex(root->height)) {
306 		error = radix_tree_extend(root, index);
307 		if (error)
308 			return error;
309 	}
310 
311 	slot = radix_tree_indirect_to_ptr(root->rnode);
312 
313 	height = root->height;
314 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
315 
316 	offset = 0;			/* uninitialised var warning */
317 	while (height > 0) {
318 		if (slot == NULL) {
319 			/* Have to add a child node.  */
320 			if (!(slot = radix_tree_node_alloc(root)))
321 				return -ENOMEM;
322 			slot->height = height;
323 			if (node) {
324 				rcu_assign_pointer(node->slots[offset], slot);
325 				node->count++;
326 			} else
327 				rcu_assign_pointer(root->rnode,
328 					radix_tree_ptr_to_indirect(slot));
329 		}
330 
331 		/* Go a level down */
332 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
333 		node = slot;
334 		slot = node->slots[offset];
335 		shift -= RADIX_TREE_MAP_SHIFT;
336 		height--;
337 	}
338 
339 	if (slot != NULL)
340 		return -EEXIST;
341 
342 	if (node) {
343 		node->count++;
344 		rcu_assign_pointer(node->slots[offset], item);
345 		BUG_ON(tag_get(node, 0, offset));
346 		BUG_ON(tag_get(node, 1, offset));
347 	} else {
348 		rcu_assign_pointer(root->rnode, item);
349 		BUG_ON(root_tag_get(root, 0));
350 		BUG_ON(root_tag_get(root, 1));
351 	}
352 
353 	return 0;
354 }
355 EXPORT_SYMBOL(radix_tree_insert);
356 
357 /*
358  * is_slot == 1 : search for the slot.
359  * is_slot == 0 : search for the node.
360  */
361 static void *radix_tree_lookup_element(struct radix_tree_root *root,
362 				unsigned long index, int is_slot)
363 {
364 	unsigned int height, shift;
365 	struct radix_tree_node *node, **slot;
366 
367 	node = rcu_dereference(root->rnode);
368 	if (node == NULL)
369 		return NULL;
370 
371 	if (!radix_tree_is_indirect_ptr(node)) {
372 		if (index > 0)
373 			return NULL;
374 		return is_slot ? (void *)&root->rnode : node;
375 	}
376 	node = radix_tree_indirect_to_ptr(node);
377 
378 	height = node->height;
379 	if (index > radix_tree_maxindex(height))
380 		return NULL;
381 
382 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
383 
384 	do {
385 		slot = (struct radix_tree_node **)
386 			(node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
387 		node = rcu_dereference(*slot);
388 		if (node == NULL)
389 			return NULL;
390 
391 		shift -= RADIX_TREE_MAP_SHIFT;
392 		height--;
393 	} while (height > 0);
394 
395 	return is_slot ? (void *)slot:node;
396 }
397 
398 /**
399  *	radix_tree_lookup_slot    -    lookup a slot in a radix tree
400  *	@root:		radix tree root
401  *	@index:		index key
402  *
403  *	Returns:  the slot corresponding to the position @index in the
404  *	radix tree @root. This is useful for update-if-exists operations.
405  *
406  *	This function can be called under rcu_read_lock iff the slot is not
407  *	modified by radix_tree_replace_slot, otherwise it must be called
408  *	exclusive from other writers. Any dereference of the slot must be done
409  *	using radix_tree_deref_slot.
410  */
411 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
412 {
413 	return (void **)radix_tree_lookup_element(root, index, 1);
414 }
415 EXPORT_SYMBOL(radix_tree_lookup_slot);
416 
417 /**
418  *	radix_tree_lookup    -    perform lookup operation on a radix tree
419  *	@root:		radix tree root
420  *	@index:		index key
421  *
422  *	Lookup the item at the position @index in the radix tree @root.
423  *
424  *	This function can be called under rcu_read_lock, however the caller
425  *	must manage lifetimes of leaf nodes (eg. RCU may also be used to free
426  *	them safely). No RCU barriers are required to access or modify the
427  *	returned item, however.
428  */
429 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
430 {
431 	return radix_tree_lookup_element(root, index, 0);
432 }
433 EXPORT_SYMBOL(radix_tree_lookup);
434 
435 /**
436  *	radix_tree_tag_set - set a tag on a radix tree node
437  *	@root:		radix tree root
438  *	@index:		index key
439  *	@tag: 		tag index
440  *
441  *	Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
442  *	corresponding to @index in the radix tree.  From
443  *	the root all the way down to the leaf node.
444  *
445  *	Returns the address of the tagged item.   Setting a tag on a not-present
446  *	item is a bug.
447  */
448 void *radix_tree_tag_set(struct radix_tree_root *root,
449 			unsigned long index, unsigned int tag)
450 {
451 	unsigned int height, shift;
452 	struct radix_tree_node *slot;
453 
454 	height = root->height;
455 	BUG_ON(index > radix_tree_maxindex(height));
456 
457 	slot = radix_tree_indirect_to_ptr(root->rnode);
458 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
459 
460 	while (height > 0) {
461 		int offset;
462 
463 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
464 		if (!tag_get(slot, tag, offset))
465 			tag_set(slot, tag, offset);
466 		slot = slot->slots[offset];
467 		BUG_ON(slot == NULL);
468 		shift -= RADIX_TREE_MAP_SHIFT;
469 		height--;
470 	}
471 
472 	/* set the root's tag bit */
473 	if (slot && !root_tag_get(root, tag))
474 		root_tag_set(root, tag);
475 
476 	return slot;
477 }
478 EXPORT_SYMBOL(radix_tree_tag_set);
479 
480 /**
481  *	radix_tree_tag_clear - clear a tag on a radix tree node
482  *	@root:		radix tree root
483  *	@index:		index key
484  *	@tag: 		tag index
485  *
486  *	Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
487  *	corresponding to @index in the radix tree.  If
488  *	this causes the leaf node to have no tags set then clear the tag in the
489  *	next-to-leaf node, etc.
490  *
491  *	Returns the address of the tagged item on success, else NULL.  ie:
492  *	has the same return value and semantics as radix_tree_lookup().
493  */
494 void *radix_tree_tag_clear(struct radix_tree_root *root,
495 			unsigned long index, unsigned int tag)
496 {
497 	/*
498 	 * The radix tree path needs to be one longer than the maximum path
499 	 * since the "list" is null terminated.
500 	 */
501 	struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
502 	struct radix_tree_node *slot = NULL;
503 	unsigned int height, shift;
504 
505 	height = root->height;
506 	if (index > radix_tree_maxindex(height))
507 		goto out;
508 
509 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
510 	pathp->node = NULL;
511 	slot = radix_tree_indirect_to_ptr(root->rnode);
512 
513 	while (height > 0) {
514 		int offset;
515 
516 		if (slot == NULL)
517 			goto out;
518 
519 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
520 		pathp[1].offset = offset;
521 		pathp[1].node = slot;
522 		slot = slot->slots[offset];
523 		pathp++;
524 		shift -= RADIX_TREE_MAP_SHIFT;
525 		height--;
526 	}
527 
528 	if (slot == NULL)
529 		goto out;
530 
531 	while (pathp->node) {
532 		if (!tag_get(pathp->node, tag, pathp->offset))
533 			goto out;
534 		tag_clear(pathp->node, tag, pathp->offset);
535 		if (any_tag_set(pathp->node, tag))
536 			goto out;
537 		pathp--;
538 	}
539 
540 	/* clear the root's tag bit */
541 	if (root_tag_get(root, tag))
542 		root_tag_clear(root, tag);
543 
544 out:
545 	return slot;
546 }
547 EXPORT_SYMBOL(radix_tree_tag_clear);
548 
549 /**
550  * radix_tree_tag_get - get a tag on a radix tree node
551  * @root:		radix tree root
552  * @index:		index key
553  * @tag: 		tag index (< RADIX_TREE_MAX_TAGS)
554  *
555  * Return values:
556  *
557  *  0: tag not present or not set
558  *  1: tag set
559  */
560 int radix_tree_tag_get(struct radix_tree_root *root,
561 			unsigned long index, unsigned int tag)
562 {
563 	unsigned int height, shift;
564 	struct radix_tree_node *node;
565 	int saw_unset_tag = 0;
566 
567 	/* check the root's tag bit */
568 	if (!root_tag_get(root, tag))
569 		return 0;
570 
571 	node = rcu_dereference(root->rnode);
572 	if (node == NULL)
573 		return 0;
574 
575 	if (!radix_tree_is_indirect_ptr(node))
576 		return (index == 0);
577 	node = radix_tree_indirect_to_ptr(node);
578 
579 	height = node->height;
580 	if (index > radix_tree_maxindex(height))
581 		return 0;
582 
583 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
584 
585 	for ( ; ; ) {
586 		int offset;
587 
588 		if (node == NULL)
589 			return 0;
590 
591 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
592 
593 		/*
594 		 * This is just a debug check.  Later, we can bale as soon as
595 		 * we see an unset tag.
596 		 */
597 		if (!tag_get(node, tag, offset))
598 			saw_unset_tag = 1;
599 		if (height == 1) {
600 			int ret = tag_get(node, tag, offset);
601 
602 			BUG_ON(ret && saw_unset_tag);
603 			return !!ret;
604 		}
605 		node = rcu_dereference(node->slots[offset]);
606 		shift -= RADIX_TREE_MAP_SHIFT;
607 		height--;
608 	}
609 }
610 EXPORT_SYMBOL(radix_tree_tag_get);
611 
612 /**
613  *	radix_tree_next_hole    -    find the next hole (not-present entry)
614  *	@root:		tree root
615  *	@index:		index key
616  *	@max_scan:	maximum range to search
617  *
618  *	Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
619  *	indexed hole.
620  *
621  *	Returns: the index of the hole if found, otherwise returns an index
622  *	outside of the set specified (in which case 'return - index >= max_scan'
623  *	will be true). In rare cases of index wrap-around, 0 will be returned.
624  *
625  *	radix_tree_next_hole may be called under rcu_read_lock. However, like
626  *	radix_tree_gang_lookup, this will not atomically search a snapshot of
627  *	the tree at a single point in time. For example, if a hole is created
628  *	at index 5, then subsequently a hole is created at index 10,
629  *	radix_tree_next_hole covering both indexes may return 10 if called
630  *	under rcu_read_lock.
631  */
632 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
633 				unsigned long index, unsigned long max_scan)
634 {
635 	unsigned long i;
636 
637 	for (i = 0; i < max_scan; i++) {
638 		if (!radix_tree_lookup(root, index))
639 			break;
640 		index++;
641 		if (index == 0)
642 			break;
643 	}
644 
645 	return index;
646 }
647 EXPORT_SYMBOL(radix_tree_next_hole);
648 
649 /**
650  *	radix_tree_prev_hole    -    find the prev hole (not-present entry)
651  *	@root:		tree root
652  *	@index:		index key
653  *	@max_scan:	maximum range to search
654  *
655  *	Search backwards in the range [max(index-max_scan+1, 0), index]
656  *	for the first hole.
657  *
658  *	Returns: the index of the hole if found, otherwise returns an index
659  *	outside of the set specified (in which case 'index - return >= max_scan'
660  *	will be true). In rare cases of wrap-around, LONG_MAX will be returned.
661  *
662  *	radix_tree_next_hole may be called under rcu_read_lock. However, like
663  *	radix_tree_gang_lookup, this will not atomically search a snapshot of
664  *	the tree at a single point in time. For example, if a hole is created
665  *	at index 10, then subsequently a hole is created at index 5,
666  *	radix_tree_prev_hole covering both indexes may return 5 if called under
667  *	rcu_read_lock.
668  */
669 unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
670 				   unsigned long index, unsigned long max_scan)
671 {
672 	unsigned long i;
673 
674 	for (i = 0; i < max_scan; i++) {
675 		if (!radix_tree_lookup(root, index))
676 			break;
677 		index--;
678 		if (index == LONG_MAX)
679 			break;
680 	}
681 
682 	return index;
683 }
684 EXPORT_SYMBOL(radix_tree_prev_hole);
685 
686 static unsigned int
687 __lookup(struct radix_tree_node *slot, void ***results, unsigned long index,
688 	unsigned int max_items, unsigned long *next_index)
689 {
690 	unsigned int nr_found = 0;
691 	unsigned int shift, height;
692 	unsigned long i;
693 
694 	height = slot->height;
695 	if (height == 0)
696 		goto out;
697 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
698 
699 	for ( ; height > 1; height--) {
700 		i = (index >> shift) & RADIX_TREE_MAP_MASK;
701 		for (;;) {
702 			if (slot->slots[i] != NULL)
703 				break;
704 			index &= ~((1UL << shift) - 1);
705 			index += 1UL << shift;
706 			if (index == 0)
707 				goto out;	/* 32-bit wraparound */
708 			i++;
709 			if (i == RADIX_TREE_MAP_SIZE)
710 				goto out;
711 		}
712 
713 		shift -= RADIX_TREE_MAP_SHIFT;
714 		slot = rcu_dereference(slot->slots[i]);
715 		if (slot == NULL)
716 			goto out;
717 	}
718 
719 	/* Bottom level: grab some items */
720 	for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
721 		index++;
722 		if (slot->slots[i]) {
723 			results[nr_found++] = &(slot->slots[i]);
724 			if (nr_found == max_items)
725 				goto out;
726 		}
727 	}
728 out:
729 	*next_index = index;
730 	return nr_found;
731 }
732 
733 /**
734  *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
735  *	@root:		radix tree root
736  *	@results:	where the results of the lookup are placed
737  *	@first_index:	start the lookup from this key
738  *	@max_items:	place up to this many items at *results
739  *
740  *	Performs an index-ascending scan of the tree for present items.  Places
741  *	them at *@results and returns the number of items which were placed at
742  *	*@results.
743  *
744  *	The implementation is naive.
745  *
746  *	Like radix_tree_lookup, radix_tree_gang_lookup may be called under
747  *	rcu_read_lock. In this case, rather than the returned results being
748  *	an atomic snapshot of the tree at a single point in time, the semantics
749  *	of an RCU protected gang lookup are as though multiple radix_tree_lookups
750  *	have been issued in individual locks, and results stored in 'results'.
751  */
752 unsigned int
753 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
754 			unsigned long first_index, unsigned int max_items)
755 {
756 	unsigned long max_index;
757 	struct radix_tree_node *node;
758 	unsigned long cur_index = first_index;
759 	unsigned int ret;
760 
761 	node = rcu_dereference(root->rnode);
762 	if (!node)
763 		return 0;
764 
765 	if (!radix_tree_is_indirect_ptr(node)) {
766 		if (first_index > 0)
767 			return 0;
768 		results[0] = node;
769 		return 1;
770 	}
771 	node = radix_tree_indirect_to_ptr(node);
772 
773 	max_index = radix_tree_maxindex(node->height);
774 
775 	ret = 0;
776 	while (ret < max_items) {
777 		unsigned int nr_found, slots_found, i;
778 		unsigned long next_index;	/* Index of next search */
779 
780 		if (cur_index > max_index)
781 			break;
782 		slots_found = __lookup(node, (void ***)results + ret, cur_index,
783 					max_items - ret, &next_index);
784 		nr_found = 0;
785 		for (i = 0; i < slots_found; i++) {
786 			struct radix_tree_node *slot;
787 			slot = *(((void ***)results)[ret + i]);
788 			if (!slot)
789 				continue;
790 			results[ret + nr_found] = rcu_dereference(slot);
791 			nr_found++;
792 		}
793 		ret += nr_found;
794 		if (next_index == 0)
795 			break;
796 		cur_index = next_index;
797 	}
798 
799 	return ret;
800 }
801 EXPORT_SYMBOL(radix_tree_gang_lookup);
802 
803 /**
804  *	radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
805  *	@root:		radix tree root
806  *	@results:	where the results of the lookup are placed
807  *	@first_index:	start the lookup from this key
808  *	@max_items:	place up to this many items at *results
809  *
810  *	Performs an index-ascending scan of the tree for present items.  Places
811  *	their slots at *@results and returns the number of items which were
812  *	placed at *@results.
813  *
814  *	The implementation is naive.
815  *
816  *	Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
817  *	be dereferenced with radix_tree_deref_slot, and if using only RCU
818  *	protection, radix_tree_deref_slot may fail requiring a retry.
819  */
820 unsigned int
821 radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
822 			unsigned long first_index, unsigned int max_items)
823 {
824 	unsigned long max_index;
825 	struct radix_tree_node *node;
826 	unsigned long cur_index = first_index;
827 	unsigned int ret;
828 
829 	node = rcu_dereference(root->rnode);
830 	if (!node)
831 		return 0;
832 
833 	if (!radix_tree_is_indirect_ptr(node)) {
834 		if (first_index > 0)
835 			return 0;
836 		results[0] = (void **)&root->rnode;
837 		return 1;
838 	}
839 	node = radix_tree_indirect_to_ptr(node);
840 
841 	max_index = radix_tree_maxindex(node->height);
842 
843 	ret = 0;
844 	while (ret < max_items) {
845 		unsigned int slots_found;
846 		unsigned long next_index;	/* Index of next search */
847 
848 		if (cur_index > max_index)
849 			break;
850 		slots_found = __lookup(node, results + ret, cur_index,
851 					max_items - ret, &next_index);
852 		ret += slots_found;
853 		if (next_index == 0)
854 			break;
855 		cur_index = next_index;
856 	}
857 
858 	return ret;
859 }
860 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
861 
862 /*
863  * FIXME: the two tag_get()s here should use find_next_bit() instead of
864  * open-coding the search.
865  */
866 static unsigned int
867 __lookup_tag(struct radix_tree_node *slot, void ***results, unsigned long index,
868 	unsigned int max_items, unsigned long *next_index, unsigned int tag)
869 {
870 	unsigned int nr_found = 0;
871 	unsigned int shift, height;
872 
873 	height = slot->height;
874 	if (height == 0)
875 		goto out;
876 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
877 
878 	while (height > 0) {
879 		unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
880 
881 		for (;;) {
882 			if (tag_get(slot, tag, i))
883 				break;
884 			index &= ~((1UL << shift) - 1);
885 			index += 1UL << shift;
886 			if (index == 0)
887 				goto out;	/* 32-bit wraparound */
888 			i++;
889 			if (i == RADIX_TREE_MAP_SIZE)
890 				goto out;
891 		}
892 		height--;
893 		if (height == 0) {	/* Bottom level: grab some items */
894 			unsigned long j = index & RADIX_TREE_MAP_MASK;
895 
896 			for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
897 				index++;
898 				if (!tag_get(slot, tag, j))
899 					continue;
900 				/*
901 				 * Even though the tag was found set, we need to
902 				 * recheck that we have a non-NULL node, because
903 				 * if this lookup is lockless, it may have been
904 				 * subsequently deleted.
905 				 *
906 				 * Similar care must be taken in any place that
907 				 * lookup ->slots[x] without a lock (ie. can't
908 				 * rely on its value remaining the same).
909 				 */
910 				if (slot->slots[j]) {
911 					results[nr_found++] = &(slot->slots[j]);
912 					if (nr_found == max_items)
913 						goto out;
914 				}
915 			}
916 		}
917 		shift -= RADIX_TREE_MAP_SHIFT;
918 		slot = rcu_dereference(slot->slots[i]);
919 		if (slot == NULL)
920 			break;
921 	}
922 out:
923 	*next_index = index;
924 	return nr_found;
925 }
926 
927 /**
928  *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
929  *	                             based on a tag
930  *	@root:		radix tree root
931  *	@results:	where the results of the lookup are placed
932  *	@first_index:	start the lookup from this key
933  *	@max_items:	place up to this many items at *results
934  *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
935  *
936  *	Performs an index-ascending scan of the tree for present items which
937  *	have the tag indexed by @tag set.  Places the items at *@results and
938  *	returns the number of items which were placed at *@results.
939  */
940 unsigned int
941 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
942 		unsigned long first_index, unsigned int max_items,
943 		unsigned int tag)
944 {
945 	struct radix_tree_node *node;
946 	unsigned long max_index;
947 	unsigned long cur_index = first_index;
948 	unsigned int ret;
949 
950 	/* check the root's tag bit */
951 	if (!root_tag_get(root, tag))
952 		return 0;
953 
954 	node = rcu_dereference(root->rnode);
955 	if (!node)
956 		return 0;
957 
958 	if (!radix_tree_is_indirect_ptr(node)) {
959 		if (first_index > 0)
960 			return 0;
961 		results[0] = node;
962 		return 1;
963 	}
964 	node = radix_tree_indirect_to_ptr(node);
965 
966 	max_index = radix_tree_maxindex(node->height);
967 
968 	ret = 0;
969 	while (ret < max_items) {
970 		unsigned int nr_found, slots_found, i;
971 		unsigned long next_index;	/* Index of next search */
972 
973 		if (cur_index > max_index)
974 			break;
975 		slots_found = __lookup_tag(node, (void ***)results + ret,
976 				cur_index, max_items - ret, &next_index, tag);
977 		nr_found = 0;
978 		for (i = 0; i < slots_found; i++) {
979 			struct radix_tree_node *slot;
980 			slot = *(((void ***)results)[ret + i]);
981 			if (!slot)
982 				continue;
983 			results[ret + nr_found] = rcu_dereference(slot);
984 			nr_found++;
985 		}
986 		ret += nr_found;
987 		if (next_index == 0)
988 			break;
989 		cur_index = next_index;
990 	}
991 
992 	return ret;
993 }
994 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
995 
996 /**
997  *	radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
998  *					  radix tree based on a tag
999  *	@root:		radix tree root
1000  *	@results:	where the results of the lookup are placed
1001  *	@first_index:	start the lookup from this key
1002  *	@max_items:	place up to this many items at *results
1003  *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
1004  *
1005  *	Performs an index-ascending scan of the tree for present items which
1006  *	have the tag indexed by @tag set.  Places the slots at *@results and
1007  *	returns the number of slots which were placed at *@results.
1008  */
1009 unsigned int
1010 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1011 		unsigned long first_index, unsigned int max_items,
1012 		unsigned int tag)
1013 {
1014 	struct radix_tree_node *node;
1015 	unsigned long max_index;
1016 	unsigned long cur_index = first_index;
1017 	unsigned int ret;
1018 
1019 	/* check the root's tag bit */
1020 	if (!root_tag_get(root, tag))
1021 		return 0;
1022 
1023 	node = rcu_dereference(root->rnode);
1024 	if (!node)
1025 		return 0;
1026 
1027 	if (!radix_tree_is_indirect_ptr(node)) {
1028 		if (first_index > 0)
1029 			return 0;
1030 		results[0] = (void **)&root->rnode;
1031 		return 1;
1032 	}
1033 	node = radix_tree_indirect_to_ptr(node);
1034 
1035 	max_index = radix_tree_maxindex(node->height);
1036 
1037 	ret = 0;
1038 	while (ret < max_items) {
1039 		unsigned int slots_found;
1040 		unsigned long next_index;	/* Index of next search */
1041 
1042 		if (cur_index > max_index)
1043 			break;
1044 		slots_found = __lookup_tag(node, results + ret,
1045 				cur_index, max_items - ret, &next_index, tag);
1046 		ret += slots_found;
1047 		if (next_index == 0)
1048 			break;
1049 		cur_index = next_index;
1050 	}
1051 
1052 	return ret;
1053 }
1054 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1055 
1056 
1057 /**
1058  *	radix_tree_shrink    -    shrink height of a radix tree to minimal
1059  *	@root		radix tree root
1060  */
1061 static inline void radix_tree_shrink(struct radix_tree_root *root)
1062 {
1063 	/* try to shrink tree height */
1064 	while (root->height > 0) {
1065 		struct radix_tree_node *to_free = root->rnode;
1066 		void *newptr;
1067 
1068 		BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1069 		to_free = radix_tree_indirect_to_ptr(to_free);
1070 
1071 		/*
1072 		 * The candidate node has more than one child, or its child
1073 		 * is not at the leftmost slot, we cannot shrink.
1074 		 */
1075 		if (to_free->count != 1)
1076 			break;
1077 		if (!to_free->slots[0])
1078 			break;
1079 
1080 		/*
1081 		 * We don't need rcu_assign_pointer(), since we are simply
1082 		 * moving the node from one part of the tree to another. If
1083 		 * it was safe to dereference the old pointer to it
1084 		 * (to_free->slots[0]), it will be safe to dereference the new
1085 		 * one (root->rnode).
1086 		 */
1087 		newptr = to_free->slots[0];
1088 		if (root->height > 1)
1089 			newptr = radix_tree_ptr_to_indirect(newptr);
1090 		root->rnode = newptr;
1091 		root->height--;
1092 		radix_tree_node_free(to_free);
1093 	}
1094 }
1095 
1096 /**
1097  *	radix_tree_delete    -    delete an item from a radix tree
1098  *	@root:		radix tree root
1099  *	@index:		index key
1100  *
1101  *	Remove the item at @index from the radix tree rooted at @root.
1102  *
1103  *	Returns the address of the deleted item, or NULL if it was not present.
1104  */
1105 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1106 {
1107 	/*
1108 	 * The radix tree path needs to be one longer than the maximum path
1109 	 * since the "list" is null terminated.
1110 	 */
1111 	struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
1112 	struct radix_tree_node *slot = NULL;
1113 	struct radix_tree_node *to_free;
1114 	unsigned int height, shift;
1115 	int tag;
1116 	int offset;
1117 
1118 	height = root->height;
1119 	if (index > radix_tree_maxindex(height))
1120 		goto out;
1121 
1122 	slot = root->rnode;
1123 	if (height == 0) {
1124 		root_tag_clear_all(root);
1125 		root->rnode = NULL;
1126 		goto out;
1127 	}
1128 	slot = radix_tree_indirect_to_ptr(slot);
1129 
1130 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
1131 	pathp->node = NULL;
1132 
1133 	do {
1134 		if (slot == NULL)
1135 			goto out;
1136 
1137 		pathp++;
1138 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
1139 		pathp->offset = offset;
1140 		pathp->node = slot;
1141 		slot = slot->slots[offset];
1142 		shift -= RADIX_TREE_MAP_SHIFT;
1143 		height--;
1144 	} while (height > 0);
1145 
1146 	if (slot == NULL)
1147 		goto out;
1148 
1149 	/*
1150 	 * Clear all tags associated with the just-deleted item
1151 	 */
1152 	for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1153 		if (tag_get(pathp->node, tag, pathp->offset))
1154 			radix_tree_tag_clear(root, index, tag);
1155 	}
1156 
1157 	to_free = NULL;
1158 	/* Now free the nodes we do not need anymore */
1159 	while (pathp->node) {
1160 		pathp->node->slots[pathp->offset] = NULL;
1161 		pathp->node->count--;
1162 		/*
1163 		 * Queue the node for deferred freeing after the
1164 		 * last reference to it disappears (set NULL, above).
1165 		 */
1166 		if (to_free)
1167 			radix_tree_node_free(to_free);
1168 
1169 		if (pathp->node->count) {
1170 			if (pathp->node ==
1171 					radix_tree_indirect_to_ptr(root->rnode))
1172 				radix_tree_shrink(root);
1173 			goto out;
1174 		}
1175 
1176 		/* Node with zero slots in use so free it */
1177 		to_free = pathp->node;
1178 		pathp--;
1179 
1180 	}
1181 	root_tag_clear_all(root);
1182 	root->height = 0;
1183 	root->rnode = NULL;
1184 	if (to_free)
1185 		radix_tree_node_free(to_free);
1186 
1187 out:
1188 	return slot;
1189 }
1190 EXPORT_SYMBOL(radix_tree_delete);
1191 
1192 /**
1193  *	radix_tree_tagged - test whether any items in the tree are tagged
1194  *	@root:		radix tree root
1195  *	@tag:		tag to test
1196  */
1197 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1198 {
1199 	return root_tag_get(root, tag);
1200 }
1201 EXPORT_SYMBOL(radix_tree_tagged);
1202 
1203 static void
1204 radix_tree_node_ctor(void *node)
1205 {
1206 	memset(node, 0, sizeof(struct radix_tree_node));
1207 }
1208 
1209 static __init unsigned long __maxindex(unsigned int height)
1210 {
1211 	unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1212 	int shift = RADIX_TREE_INDEX_BITS - width;
1213 
1214 	if (shift < 0)
1215 		return ~0UL;
1216 	if (shift >= BITS_PER_LONG)
1217 		return 0UL;
1218 	return ~0UL >> shift;
1219 }
1220 
1221 static __init void radix_tree_init_maxindex(void)
1222 {
1223 	unsigned int i;
1224 
1225 	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1226 		height_to_maxindex[i] = __maxindex(i);
1227 }
1228 
1229 static int radix_tree_callback(struct notifier_block *nfb,
1230                             unsigned long action,
1231                             void *hcpu)
1232 {
1233        int cpu = (long)hcpu;
1234        struct radix_tree_preload *rtp;
1235 
1236        /* Free per-cpu pool of perloaded nodes */
1237        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1238                rtp = &per_cpu(radix_tree_preloads, cpu);
1239                while (rtp->nr) {
1240                        kmem_cache_free(radix_tree_node_cachep,
1241                                        rtp->nodes[rtp->nr-1]);
1242                        rtp->nodes[rtp->nr-1] = NULL;
1243                        rtp->nr--;
1244                }
1245        }
1246        return NOTIFY_OK;
1247 }
1248 
1249 void __init radix_tree_init(void)
1250 {
1251 	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1252 			sizeof(struct radix_tree_node), 0,
1253 			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1254 			radix_tree_node_ctor);
1255 	radix_tree_init_maxindex();
1256 	hotcpu_notifier(radix_tree_callback, 0);
1257 }
1258