[PATCH] reiser4: add radix_tree_lookup_slot()
[linux-2.6.git] / lib / radix-tree.c
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 static inline void **__lookup_slot(struct radix_tree_root *root,
285                                    unsigned long index)
286 {
287         unsigned int height, shift;
288         struct radix_tree_node **slot;
289
290         height = root->height;
291         if (index > radix_tree_maxindex(height))
292                 return NULL;
293
294         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
295         slot = &root->rnode;
296
297         while (height > 0) {
298                 if (*slot == NULL)
299                         return NULL;
300
301                 slot = (struct radix_tree_node **)
302                         ((*slot)->slots +
303                                 ((index >> shift) & RADIX_TREE_MAP_MASK));
304                 shift -= RADIX_TREE_MAP_SHIFT;
305                 height--;
306         }
307
308         return (void **)slot;
309 }
310
311 /**
312  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
313  *      @root:          radix tree root
314  *      @index:         index key
315  *
316  *      Lookup the slot corresponding to the position @index in the radix tree
317  *      @root. This is useful for update-if-exists operations.
318  */
319 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
320 {
321         return __lookup_slot(root, index);
322 }
323 EXPORT_SYMBOL(radix_tree_lookup_slot);
324
325 /**
326  *      radix_tree_lookup    -    perform lookup operation on a radix tree
327  *      @root:          radix tree root
328  *      @index:         index key
329  *
330  *      Lookup the item at the position @index in the radix tree @root.
331  */
332 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
333 {
334         void **slot;
335
336         slot = __lookup_slot(root, index);
337         return slot != NULL ? *slot : NULL;
338 }
339 EXPORT_SYMBOL(radix_tree_lookup);
340
341 /**
342  *      radix_tree_tag_set - set a tag on a radix tree node
343  *      @root:          radix tree root
344  *      @index:         index key
345  *      @tag:           tag index
346  *
347  *      Set the search tag corresponging to @index in the radix tree.  From
348  *      the root all the way down to the leaf node.
349  *
350  *      Returns the address of the tagged item.   Setting a tag on a not-present
351  *      item is a bug.
352  */
353 void *radix_tree_tag_set(struct radix_tree_root *root,
354                         unsigned long index, int tag)
355 {
356         unsigned int height, shift;
357         struct radix_tree_node *slot;
358
359         height = root->height;
360         if (index > radix_tree_maxindex(height))
361                 return NULL;
362
363         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
364         slot = root->rnode;
365
366         while (height > 0) {
367                 int offset;
368
369                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
370                 tag_set(slot, tag, offset);
371                 slot = slot->slots[offset];
372                 BUG_ON(slot == NULL);
373                 shift -= RADIX_TREE_MAP_SHIFT;
374                 height--;
375         }
376
377         return slot;
378 }
379 EXPORT_SYMBOL(radix_tree_tag_set);
380
381 /**
382  *      radix_tree_tag_clear - clear a tag on a radix tree node
383  *      @root:          radix tree root
384  *      @index:         index key
385  *      @tag:           tag index
386  *
387  *      Clear the search tag corresponging to @index in the radix tree.  If
388  *      this causes the leaf node to have no tags set then clear the tag in the
389  *      next-to-leaf node, etc.
390  *
391  *      Returns the address of the tagged item on success, else NULL.  ie:
392  *      has the same return value and semantics as radix_tree_lookup().
393  */
394 void *radix_tree_tag_clear(struct radix_tree_root *root,
395                         unsigned long index, int tag)
396 {
397         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
398         struct radix_tree_node *slot;
399         unsigned int height, shift;
400         void *ret = NULL;
401
402         height = root->height;
403         if (index > radix_tree_maxindex(height))
404                 goto out;
405
406         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
407         pathp->node = NULL;
408         slot = root->rnode;
409
410         while (height > 0) {
411                 int offset;
412
413                 if (slot == NULL)
414                         goto out;
415
416                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
417                 pathp[1].offset = offset;
418                 pathp[1].node = slot;
419                 slot = slot->slots[offset];
420                 pathp++;
421                 shift -= RADIX_TREE_MAP_SHIFT;
422                 height--;
423         }
424
425         ret = slot;
426         if (ret == NULL)
427                 goto out;
428
429         do {
430                 int idx;
431
432                 tag_clear(pathp->node, tag, pathp->offset);
433                 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
434                         if (pathp->node->tags[tag][idx])
435                                 goto out;
436                 }
437                 pathp--;
438         } while (pathp->node);
439 out:
440         return ret;
441 }
442 EXPORT_SYMBOL(radix_tree_tag_clear);
443
444 #ifndef __KERNEL__      /* Only the test harness uses this at present */
445 /**
446  * radix_tree_tag_get - get a tag on a radix tree node
447  * @root:               radix tree root
448  * @index:              index key
449  * @tag:                tag index
450  *
451  * Return values:
452  *
453  *  0: tag not present
454  *  1: tag present, set
455  * -1: tag present, unset
456  */
457 int radix_tree_tag_get(struct radix_tree_root *root,
458                         unsigned long index, int tag)
459 {
460         unsigned int height, shift;
461         struct radix_tree_node *slot;
462         int saw_unset_tag = 0;
463
464         height = root->height;
465         if (index > radix_tree_maxindex(height))
466                 return 0;
467
468         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
469         slot = root->rnode;
470
471         for ( ; ; ) {
472                 int offset;
473
474                 if (slot == NULL)
475                         return 0;
476
477                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
478
479                 /*
480                  * This is just a debug check.  Later, we can bale as soon as
481                  * we see an unset tag.
482                  */
483                 if (!tag_get(slot, tag, offset))
484                         saw_unset_tag = 1;
485                 if (height == 1) {
486                         int ret = tag_get(slot, tag, offset);
487
488                         BUG_ON(ret && saw_unset_tag);
489                         return ret ? 1 : -1;
490                 }
491                 slot = slot->slots[offset];
492                 shift -= RADIX_TREE_MAP_SHIFT;
493                 height--;
494         }
495 }
496 EXPORT_SYMBOL(radix_tree_tag_get);
497 #endif
498
499 static unsigned int
500 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
501         unsigned int max_items, unsigned long *next_index)
502 {
503         unsigned int nr_found = 0;
504         unsigned int shift, height;
505         struct radix_tree_node *slot;
506         unsigned long i;
507
508         height = root->height;
509         if (height == 0)
510                 goto out;
511
512         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
513         slot = root->rnode;
514
515         for ( ; height > 1; height--) {
516
517                 for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
518                                 i < RADIX_TREE_MAP_SIZE; i++) {
519                         if (slot->slots[i] != NULL)
520                                 break;
521                         index &= ~((1UL << shift) - 1);
522                         index += 1UL << shift;
523                         if (index == 0)
524                                 goto out;       /* 32-bit wraparound */
525                 }
526                 if (i == RADIX_TREE_MAP_SIZE)
527                         goto out;
528
529                 shift -= RADIX_TREE_MAP_SHIFT;
530                 slot = slot->slots[i];
531         }
532
533         /* Bottom level: grab some items */
534         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
535                 index++;
536                 if (slot->slots[i]) {
537                         results[nr_found++] = slot->slots[i];
538                         if (nr_found == max_items)
539                                 goto out;
540                 }
541         }
542 out:
543         *next_index = index;
544         return nr_found;
545 }
546
547 /**
548  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
549  *      @root:          radix tree root
550  *      @results:       where the results of the lookup are placed
551  *      @first_index:   start the lookup from this key
552  *      @max_items:     place up to this many items at *results
553  *
554  *      Performs an index-ascending scan of the tree for present items.  Places
555  *      them at *@results and returns the number of items which were placed at
556  *      *@results.
557  *
558  *      The implementation is naive.
559  */
560 unsigned int
561 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
562                         unsigned long first_index, unsigned int max_items)
563 {
564         const unsigned long max_index = radix_tree_maxindex(root->height);
565         unsigned long cur_index = first_index;
566         unsigned int ret = 0;
567
568         while (ret < max_items) {
569                 unsigned int nr_found;
570                 unsigned long next_index;       /* Index of next search */
571
572                 if (cur_index > max_index)
573                         break;
574                 nr_found = __lookup(root, results + ret, cur_index,
575                                         max_items - ret, &next_index);
576                 ret += nr_found;
577                 if (next_index == 0)
578                         break;
579                 cur_index = next_index;
580         }
581         return ret;
582 }
583 EXPORT_SYMBOL(radix_tree_gang_lookup);
584
585 /*
586  * FIXME: the two tag_get()s here should use find_next_bit() instead of
587  * open-coding the search.
588  */
589 static unsigned int
590 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
591         unsigned int max_items, unsigned long *next_index, int tag)
592 {
593         unsigned int nr_found = 0;
594         unsigned int shift;
595         unsigned int height = root->height;
596         struct radix_tree_node *slot;
597
598         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
599         slot = root->rnode;
600
601         while (height > 0) {
602                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
603
604                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
605                         if (tag_get(slot, tag, i)) {
606                                 BUG_ON(slot->slots[i] == NULL);
607                                 break;
608                         }
609                         index &= ~((1UL << shift) - 1);
610                         index += 1UL << shift;
611                         if (index == 0)
612                                 goto out;       /* 32-bit wraparound */
613                 }
614                 if (i == RADIX_TREE_MAP_SIZE)
615                         goto out;
616                 height--;
617                 if (height == 0) {      /* Bottom level: grab some items */
618                         unsigned long j = index & RADIX_TREE_MAP_MASK;
619
620                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
621                                 index++;
622                                 if (tag_get(slot, tag, j)) {
623                                         BUG_ON(slot->slots[j] == NULL);
624                                         results[nr_found++] = slot->slots[j];
625                                         if (nr_found == max_items)
626                                                 goto out;
627                                 }
628                         }
629                 }
630                 shift -= RADIX_TREE_MAP_SHIFT;
631                 slot = slot->slots[i];
632         }
633 out:
634         *next_index = index;
635         return nr_found;
636 }
637
638 /**
639  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
640  *                                   based on a tag
641  *      @root:          radix tree root
642  *      @results:       where the results of the lookup are placed
643  *      @first_index:   start the lookup from this key
644  *      @max_items:     place up to this many items at *results
645  *      @tag:           the tag index
646  *
647  *      Performs an index-ascending scan of the tree for present items which
648  *      have the tag indexed by @tag set.  Places the items at *@results and
649  *      returns the number of items which were placed at *@results.
650  */
651 unsigned int
652 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
653                 unsigned long first_index, unsigned int max_items, int tag)
654 {
655         const unsigned long max_index = radix_tree_maxindex(root->height);
656         unsigned long cur_index = first_index;
657         unsigned int ret = 0;
658
659         while (ret < max_items) {
660                 unsigned int nr_found;
661                 unsigned long next_index;       /* Index of next search */
662
663                 if (cur_index > max_index)
664                         break;
665                 nr_found = __lookup_tag(root, results + ret, cur_index,
666                                         max_items - ret, &next_index, tag);
667                 ret += nr_found;
668                 if (next_index == 0)
669                         break;
670                 cur_index = next_index;
671         }
672         return ret;
673 }
674 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
675
676 /**
677  *      radix_tree_delete    -    delete an item from a radix tree
678  *      @root:          radix tree root
679  *      @index:         index key
680  *
681  *      Remove the item at @index from the radix tree rooted at @root.
682  *
683  *      Returns the address of the deleted item, or NULL if it was not present.
684  */
685 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
686 {
687         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
688         struct radix_tree_path *orig_pathp;
689         struct radix_tree_node *slot;
690         unsigned int height, shift;
691         void *ret = NULL;
692         char tags[RADIX_TREE_TAGS];
693         int nr_cleared_tags;
694
695         height = root->height;
696         if (index > radix_tree_maxindex(height))
697                 goto out;
698
699         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
700         pathp->node = NULL;
701         slot = root->rnode;
702
703         for ( ; height > 0; height--) {
704                 int offset;
705
706                 if (slot == NULL)
707                         goto out;
708
709                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
710                 pathp[1].offset = offset;
711                 pathp[1].node = slot;
712                 slot = slot->slots[offset];
713                 pathp++;
714                 shift -= RADIX_TREE_MAP_SHIFT;
715         }
716
717         ret = slot;
718         if (ret == NULL)
719                 goto out;
720
721         orig_pathp = pathp;
722
723         /*
724          * Clear all tags associated with the just-deleted item
725          */
726         memset(tags, 0, sizeof(tags));
727         do {
728                 int tag;
729
730                 nr_cleared_tags = RADIX_TREE_TAGS;
731                 for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
732                         int idx;
733
734                         if (tags[tag])
735                                 continue;
736
737                         tag_clear(pathp->node, tag, pathp->offset);
738
739                         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
740                                 if (pathp->node->tags[tag][idx]) {
741                                         tags[tag] = 1;
742                                         nr_cleared_tags--;
743                                         break;
744                                 }
745                         }
746                 }
747                 pathp--;
748         } while (pathp->node && nr_cleared_tags);
749
750         /* Now free the nodes we do not need anymore */
751         for (pathp = orig_pathp; pathp->node; pathp--) {
752                 pathp->node->slots[pathp->offset] = NULL;
753                 if (--pathp->node->count)
754                         goto out;
755
756                 /* Node with zero slots in use so free it */
757                 radix_tree_node_free(pathp->node);
758         }
759         root->rnode = NULL;
760         root->height = 0;
761 out:
762         return ret;
763 }
764 EXPORT_SYMBOL(radix_tree_delete);
765
766 /**
767  *      radix_tree_tagged - test whether any items in the tree are tagged
768  *      @root:          radix tree root
769  *      @tag:           tag to test
770  */
771 int radix_tree_tagged(struct radix_tree_root *root, int tag)
772 {
773         int idx;
774
775         if (!root->rnode)
776                 return 0;
777         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
778                 if (root->rnode->tags[tag][idx])
779                         return 1;
780         }
781         return 0;
782 }
783 EXPORT_SYMBOL(radix_tree_tagged);
784
785 static void
786 radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
787 {
788         memset(node, 0, sizeof(struct radix_tree_node));
789 }
790
791 static __init unsigned long __maxindex(unsigned int height)
792 {
793         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
794         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
795
796         if (tmp >= RADIX_TREE_INDEX_BITS)
797                 index = ~0UL;
798         return index;
799 }
800
801 static __init void radix_tree_init_maxindex(void)
802 {
803         unsigned int i;
804
805         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
806                 height_to_maxindex[i] = __maxindex(i);
807 }
808
809 #ifdef CONFIG_HOTPLUG_CPU
810 static int radix_tree_callback(struct notifier_block *nfb,
811                             unsigned long action,
812                             void *hcpu)
813 {
814        int cpu = (long)hcpu;
815        struct radix_tree_preload *rtp;
816
817        /* Free per-cpu pool of perloaded nodes */
818        if (action == CPU_DEAD) {
819                rtp = &per_cpu(radix_tree_preloads, cpu);
820                while (rtp->nr) {
821                        kmem_cache_free(radix_tree_node_cachep,
822                                        rtp->nodes[rtp->nr-1]);
823                        rtp->nodes[rtp->nr-1] = NULL;
824                        rtp->nr--;
825                }
826        }
827        return NOTIFY_OK;
828 }
829 #endif /* CONFIG_HOTPLUG_CPU */
830
831 void __init radix_tree_init(void)
832 {
833         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
834                         sizeof(struct radix_tree_node), 0,
835                         SLAB_PANIC, radix_tree_node_ctor, NULL);
836         radix_tree_init_maxindex();
837         hotcpu_notifier(radix_tree_callback, 0);
838 }