[PATCH] radix-tree: Remove unnecessary indirections and clean up code
[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(int 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 the search tag corresponging to @index in the radix tree.
427  *
428  *      Returns zero if the tag is unset, or if there is no corresponding item
429  *      in the tree.
430  */
431 int radix_tree_tag_get(struct radix_tree_root *root,
432                         unsigned long index, int tag)
433 {
434         unsigned int height, shift;
435         struct radix_tree_node *slot;
436         int saw_unset_tag = 0;
437
438         height = root->height;
439         if (index > radix_tree_maxindex(height))
440                 return 0;
441
442         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
443         slot = root->rnode;
444
445         for ( ; ; ) {
446                 int offset;
447
448                 if (slot == NULL)
449                         return 0;
450
451                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
452
453                 /*
454                  * This is just a debug check.  Later, we can bale as soon as
455                  * we see an unset tag.
456                  */
457                 if (!tag_get(slot, tag, offset))
458                         saw_unset_tag = 1;
459                 if (height == 1) {
460                         int ret = tag_get(slot, tag, offset);
461
462                         BUG_ON(ret && saw_unset_tag);
463                         return ret;
464                 }
465                 slot = slot->slots[offset];
466                 shift -= RADIX_TREE_MAP_SHIFT;
467                 height--;
468         }
469 }
470 EXPORT_SYMBOL(radix_tree_tag_get);
471 #endif
472
473 static unsigned int
474 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
475         unsigned int max_items, unsigned long *next_index)
476 {
477         unsigned int nr_found = 0;
478         unsigned int shift, height;
479         struct radix_tree_node *slot;
480         unsigned long i;
481
482         height = root->height;
483         if (height == 0)
484                 goto out;
485
486         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
487         slot = root->rnode;
488
489         for ( ; height > 1; height--) {
490
491                 for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
492                                 i < RADIX_TREE_MAP_SIZE; i++) {
493                         if (slot->slots[i] != NULL)
494                                 break;
495                         index &= ~((1UL << shift) - 1);
496                         index += 1UL << shift;
497                         if (index == 0)
498                                 goto out;       /* 32-bit wraparound */
499                 }
500                 if (i == RADIX_TREE_MAP_SIZE)
501                         goto out;
502
503                 shift -= RADIX_TREE_MAP_SHIFT;
504                 slot = slot->slots[i];
505         }
506
507         /* Bottom level: grab some items */
508         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
509                 index++;
510                 if (slot->slots[i]) {
511                         results[nr_found++] = slot->slots[i];
512                         if (nr_found == max_items)
513                                 goto out;
514                 }
515         }
516 out:
517         *next_index = index;
518         return nr_found;
519 }
520
521 /**
522  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
523  *      @root:          radix tree root
524  *      @results:       where the results of the lookup are placed
525  *      @first_index:   start the lookup from this key
526  *      @max_items:     place up to this many items at *results
527  *
528  *      Performs an index-ascending scan of the tree for present items.  Places
529  *      them at *@results and returns the number of items which were placed at
530  *      *@results.
531  *
532  *      The implementation is naive.
533  */
534 unsigned int
535 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
536                         unsigned long first_index, unsigned int max_items)
537 {
538         const unsigned long max_index = radix_tree_maxindex(root->height);
539         unsigned long cur_index = first_index;
540         unsigned int ret = 0;
541
542         while (ret < max_items) {
543                 unsigned int nr_found;
544                 unsigned long next_index;       /* Index of next search */
545
546                 if (cur_index > max_index)
547                         break;
548                 nr_found = __lookup(root, results + ret, cur_index,
549                                         max_items - ret, &next_index);
550                 ret += nr_found;
551                 if (next_index == 0)
552                         break;
553                 cur_index = next_index;
554         }
555         return ret;
556 }
557 EXPORT_SYMBOL(radix_tree_gang_lookup);
558
559 /*
560  * FIXME: the two tag_get()s here should use find_next_bit() instead of
561  * open-coding the search.
562  */
563 static unsigned int
564 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
565         unsigned int max_items, unsigned long *next_index, int tag)
566 {
567         unsigned int nr_found = 0;
568         unsigned int shift;
569         unsigned int height = root->height;
570         struct radix_tree_node *slot;
571
572         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
573         slot = root->rnode;
574
575         while (height > 0) {
576                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
577
578                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
579                         if (tag_get(slot, tag, i)) {
580                                 BUG_ON(slot->slots[i] == NULL);
581                                 break;
582                         }
583                         index &= ~((1UL << shift) - 1);
584                         index += 1UL << shift;
585                         if (index == 0)
586                                 goto out;       /* 32-bit wraparound */
587                 }
588                 if (i == RADIX_TREE_MAP_SIZE)
589                         goto out;
590                 height--;
591                 if (height == 0) {      /* Bottom level: grab some items */
592                         unsigned long j = index & RADIX_TREE_MAP_MASK;
593
594                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
595                                 index++;
596                                 if (tag_get(slot, tag, j)) {
597                                         BUG_ON(slot->slots[j] == NULL);
598                                         results[nr_found++] = slot->slots[j];
599                                         if (nr_found == max_items)
600                                                 goto out;
601                                 }
602                         }
603                 }
604                 shift -= RADIX_TREE_MAP_SHIFT;
605                 slot = slot->slots[i];
606         }
607 out:
608         *next_index = index;
609         return nr_found;
610 }
611
612 /**
613  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
614  *                                   based on a tag
615  *      @root:          radix tree root
616  *      @results:       where the results of the lookup are placed
617  *      @first_index:   start the lookup from this key
618  *      @max_items:     place up to this many items at *results
619  *      @tag:           the tag index
620  *
621  *      Performs an index-ascending scan of the tree for present items which
622  *      have the tag indexed by @tag set.  Places the items at *@results and
623  *      returns the number of items which were placed at *@results.
624  */
625 unsigned int
626 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
627                 unsigned long first_index, unsigned int max_items, int tag)
628 {
629         const unsigned long max_index = radix_tree_maxindex(root->height);
630         unsigned long cur_index = first_index;
631         unsigned int ret = 0;
632
633         while (ret < max_items) {
634                 unsigned int nr_found;
635                 unsigned long next_index;       /* Index of next search */
636
637                 if (cur_index > max_index)
638                         break;
639                 nr_found = __lookup_tag(root, results + ret, cur_index,
640                                         max_items - ret, &next_index, tag);
641                 ret += nr_found;
642                 if (next_index == 0)
643                         break;
644                 cur_index = next_index;
645         }
646         return ret;
647 }
648 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
649
650 /**
651  *      radix_tree_delete    -    delete an item from a radix tree
652  *      @root:          radix tree root
653  *      @index:         index key
654  *
655  *      Remove the item at @index from the radix tree rooted at @root.
656  *
657  *      Returns the address of the deleted item, or NULL if it was not present.
658  */
659 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
660 {
661         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
662         struct radix_tree_path *orig_pathp;
663         struct radix_tree_node *slot;
664         unsigned int height, shift;
665         void *ret = NULL;
666         char tags[RADIX_TREE_TAGS];
667         int nr_cleared_tags;
668
669         height = root->height;
670         if (index > radix_tree_maxindex(height))
671                 goto out;
672
673         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
674         pathp->node = NULL;
675         slot = root->rnode;
676
677         for ( ; height > 0; height--) {
678                 int offset;
679
680                 if (slot == NULL)
681                         goto out;
682
683                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
684                 pathp[1].offset = offset;
685                 pathp[1].node = slot;
686                 slot = slot->slots[offset];
687                 pathp++;
688                 shift -= RADIX_TREE_MAP_SHIFT;
689         }
690
691         ret = slot;
692         if (ret == NULL)
693                 goto out;
694
695         orig_pathp = pathp;
696
697         /*
698          * Clear all tags associated with the just-deleted item
699          */
700         memset(tags, 0, sizeof(tags));
701         do {
702                 int tag;
703
704                 nr_cleared_tags = RADIX_TREE_TAGS;
705                 for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
706                         int idx;
707
708                         if (tags[tag])
709                                 continue;
710
711                         tag_clear(pathp->node, tag, pathp->offset);
712
713                         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
714                                 if (pathp->node->tags[tag][idx]) {
715                                         tags[tag] = 1;
716                                         nr_cleared_tags--;
717                                         break;
718                                 }
719                         }
720                 }
721                 pathp--;
722         } while (pathp->node && nr_cleared_tags);
723
724         /* Now free the nodes we do not need anymore */
725         for (pathp = orig_pathp; pathp->node; pathp--) {
726                 pathp->node->slots[pathp->offset] = NULL;
727                 if (--pathp->node->count)
728                         goto out;
729
730                 /* Node with zero slots in use so free it */
731                 radix_tree_node_free(pathp->node);
732         }
733         root->rnode = NULL;
734         root->height = 0;
735 out:
736         return ret;
737 }
738 EXPORT_SYMBOL(radix_tree_delete);
739
740 /**
741  *      radix_tree_tagged - test whether any items in the tree are tagged
742  *      @root:          radix tree root
743  *      @tag:           tag to test
744  */
745 int radix_tree_tagged(struct radix_tree_root *root, int tag)
746 {
747         int idx;
748
749         if (!root->rnode)
750                 return 0;
751         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
752                 if (root->rnode->tags[tag][idx])
753                         return 1;
754         }
755         return 0;
756 }
757 EXPORT_SYMBOL(radix_tree_tagged);
758
759 static void
760 radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
761 {
762         memset(node, 0, sizeof(struct radix_tree_node));
763 }
764
765 static __init unsigned long __maxindex(unsigned int height)
766 {
767         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
768         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
769
770         if (tmp >= RADIX_TREE_INDEX_BITS)
771                 index = ~0UL;
772         return index;
773 }
774
775 static __init void radix_tree_init_maxindex(void)
776 {
777         unsigned int i;
778
779         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
780                 height_to_maxindex[i] = __maxindex(i);
781 }
782
783 #ifdef CONFIG_HOTPLUG_CPU
784 static int radix_tree_callback(struct notifier_block *nfb,
785                             unsigned long action,
786                             void *hcpu)
787 {
788        int cpu = (long)hcpu;
789        struct radix_tree_preload *rtp;
790
791        /* Free per-cpu pool of perloaded nodes */
792        if (action == CPU_DEAD) {
793                rtp = &per_cpu(radix_tree_preloads, cpu);
794                while (rtp->nr) {
795                        kmem_cache_free(radix_tree_node_cachep,
796                                        rtp->nodes[rtp->nr-1]);
797                        rtp->nodes[rtp->nr-1] = NULL;
798                        rtp->nr--;
799                }
800        }
801        return NOTIFY_OK;
802 }
803 #endif /* CONFIG_HOTPLUG_CPU */
804
805 void __init radix_tree_init(void)
806 {
807         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
808                         sizeof(struct radix_tree_node), 0,
809                         SLAB_PANIC, radix_tree_node_ctor, NULL);
810         radix_tree_init_maxindex();
811         hotcpu_notifier(radix_tree_callback, 0);
812 }