SL*B: drop kmem cache argument from constructor
[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
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 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 int radix_tree_preload(gfp_t gfp_mask)
205 {
206         struct radix_tree_preload *rtp;
207         struct radix_tree_node *node;
208         int ret = -ENOMEM;
209
210         preempt_disable();
211         rtp = &__get_cpu_var(radix_tree_preloads);
212         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
213                 preempt_enable();
214                 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
215                 if (node == NULL)
216                         goto out;
217                 preempt_disable();
218                 rtp = &__get_cpu_var(radix_tree_preloads);
219                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
220                         rtp->nodes[rtp->nr++] = node;
221                 else
222                         kmem_cache_free(radix_tree_node_cachep, node);
223         }
224         ret = 0;
225 out:
226         return ret;
227 }
228 EXPORT_SYMBOL(radix_tree_preload);
229
230 /*
231  *      Return the maximum key which can be store into a
232  *      radix tree with height HEIGHT.
233  */
234 static inline unsigned long radix_tree_maxindex(unsigned int height)
235 {
236         return height_to_maxindex[height];
237 }
238
239 /*
240  *      Extend a radix tree so it can store key @index.
241  */
242 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
243 {
244         struct radix_tree_node *node;
245         unsigned int height;
246         int tag;
247
248         /* Figure out what the height should be.  */
249         height = root->height + 1;
250         while (index > radix_tree_maxindex(height))
251                 height++;
252
253         if (root->rnode == NULL) {
254                 root->height = height;
255                 goto out;
256         }
257
258         do {
259                 unsigned int newheight;
260                 if (!(node = radix_tree_node_alloc(root)))
261                         return -ENOMEM;
262
263                 /* Increase the height.  */
264                 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
265
266                 /* Propagate the aggregated tag info into the new root */
267                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
268                         if (root_tag_get(root, tag))
269                                 tag_set(node, tag, 0);
270                 }
271
272                 newheight = root->height+1;
273                 node->height = newheight;
274                 node->count = 1;
275                 node = radix_tree_ptr_to_indirect(node);
276                 rcu_assign_pointer(root->rnode, node);
277                 root->height = newheight;
278         } while (height > root->height);
279 out:
280         return 0;
281 }
282
283 /**
284  *      radix_tree_insert    -    insert into a radix tree
285  *      @root:          radix tree root
286  *      @index:         index key
287  *      @item:          item to insert
288  *
289  *      Insert an item into the radix tree at position @index.
290  */
291 int radix_tree_insert(struct radix_tree_root *root,
292                         unsigned long index, void *item)
293 {
294         struct radix_tree_node *node = NULL, *slot;
295         unsigned int height, shift;
296         int offset;
297         int error;
298
299         BUG_ON(radix_tree_is_indirect_ptr(item));
300
301         /* Make sure the tree is high enough.  */
302         if (index > radix_tree_maxindex(root->height)) {
303                 error = radix_tree_extend(root, index);
304                 if (error)
305                         return error;
306         }
307
308         slot = radix_tree_indirect_to_ptr(root->rnode);
309
310         height = root->height;
311         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
312
313         offset = 0;                     /* uninitialised var warning */
314         while (height > 0) {
315                 if (slot == NULL) {
316                         /* Have to add a child node.  */
317                         if (!(slot = radix_tree_node_alloc(root)))
318                                 return -ENOMEM;
319                         slot->height = height;
320                         if (node) {
321                                 rcu_assign_pointer(node->slots[offset], slot);
322                                 node->count++;
323                         } else
324                                 rcu_assign_pointer(root->rnode,
325                                         radix_tree_ptr_to_indirect(slot));
326                 }
327
328                 /* Go a level down */
329                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
330                 node = slot;
331                 slot = node->slots[offset];
332                 shift -= RADIX_TREE_MAP_SHIFT;
333                 height--;
334         }
335
336         if (slot != NULL)
337                 return -EEXIST;
338
339         if (node) {
340                 node->count++;
341                 rcu_assign_pointer(node->slots[offset], item);
342                 BUG_ON(tag_get(node, 0, offset));
343                 BUG_ON(tag_get(node, 1, offset));
344         } else {
345                 rcu_assign_pointer(root->rnode, item);
346                 BUG_ON(root_tag_get(root, 0));
347                 BUG_ON(root_tag_get(root, 1));
348         }
349
350         return 0;
351 }
352 EXPORT_SYMBOL(radix_tree_insert);
353
354 /**
355  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
356  *      @root:          radix tree root
357  *      @index:         index key
358  *
359  *      Returns:  the slot corresponding to the position @index in the
360  *      radix tree @root. This is useful for update-if-exists operations.
361  *
362  *      This function can be called under rcu_read_lock iff the slot is not
363  *      modified by radix_tree_replace_slot, otherwise it must be called
364  *      exclusive from other writers. Any dereference of the slot must be done
365  *      using radix_tree_deref_slot.
366  */
367 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
368 {
369         unsigned int height, shift;
370         struct radix_tree_node *node, **slot;
371
372         node = rcu_dereference(root->rnode);
373         if (node == NULL)
374                 return NULL;
375
376         if (!radix_tree_is_indirect_ptr(node)) {
377                 if (index > 0)
378                         return NULL;
379                 return (void **)&root->rnode;
380         }
381         node = radix_tree_indirect_to_ptr(node);
382
383         height = node->height;
384         if (index > radix_tree_maxindex(height))
385                 return NULL;
386
387         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
388
389         do {
390                 slot = (struct radix_tree_node **)
391                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
392                 node = rcu_dereference(*slot);
393                 if (node == NULL)
394                         return NULL;
395
396                 shift -= RADIX_TREE_MAP_SHIFT;
397                 height--;
398         } while (height > 0);
399
400         return (void **)slot;
401 }
402 EXPORT_SYMBOL(radix_tree_lookup_slot);
403
404 /**
405  *      radix_tree_lookup    -    perform lookup operation on a radix tree
406  *      @root:          radix tree root
407  *      @index:         index key
408  *
409  *      Lookup the item at the position @index in the radix tree @root.
410  *
411  *      This function can be called under rcu_read_lock, however the caller
412  *      must manage lifetimes of leaf nodes (eg. RCU may also be used to free
413  *      them safely). No RCU barriers are required to access or modify the
414  *      returned item, however.
415  */
416 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
417 {
418         unsigned int height, shift;
419         struct radix_tree_node *node, **slot;
420
421         node = rcu_dereference(root->rnode);
422         if (node == NULL)
423                 return NULL;
424
425         if (!radix_tree_is_indirect_ptr(node)) {
426                 if (index > 0)
427                         return NULL;
428                 return node;
429         }
430         node = radix_tree_indirect_to_ptr(node);
431
432         height = node->height;
433         if (index > radix_tree_maxindex(height))
434                 return NULL;
435
436         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
437
438         do {
439                 slot = (struct radix_tree_node **)
440                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
441                 node = rcu_dereference(*slot);
442                 if (node == NULL)
443                         return NULL;
444
445                 shift -= RADIX_TREE_MAP_SHIFT;
446                 height--;
447         } while (height > 0);
448
449         return node;
450 }
451 EXPORT_SYMBOL(radix_tree_lookup);
452
453 /**
454  *      radix_tree_tag_set - set a tag on a radix tree node
455  *      @root:          radix tree root
456  *      @index:         index key
457  *      @tag:           tag index
458  *
459  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
460  *      corresponding to @index in the radix tree.  From
461  *      the root all the way down to the leaf node.
462  *
463  *      Returns the address of the tagged item.   Setting a tag on a not-present
464  *      item is a bug.
465  */
466 void *radix_tree_tag_set(struct radix_tree_root *root,
467                         unsigned long index, unsigned int tag)
468 {
469         unsigned int height, shift;
470         struct radix_tree_node *slot;
471
472         height = root->height;
473         BUG_ON(index > radix_tree_maxindex(height));
474
475         slot = radix_tree_indirect_to_ptr(root->rnode);
476         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
477
478         while (height > 0) {
479                 int offset;
480
481                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
482                 if (!tag_get(slot, tag, offset))
483                         tag_set(slot, tag, offset);
484                 slot = slot->slots[offset];
485                 BUG_ON(slot == NULL);
486                 shift -= RADIX_TREE_MAP_SHIFT;
487                 height--;
488         }
489
490         /* set the root's tag bit */
491         if (slot && !root_tag_get(root, tag))
492                 root_tag_set(root, tag);
493
494         return slot;
495 }
496 EXPORT_SYMBOL(radix_tree_tag_set);
497
498 /**
499  *      radix_tree_tag_clear - clear a tag on a radix tree node
500  *      @root:          radix tree root
501  *      @index:         index key
502  *      @tag:           tag index
503  *
504  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
505  *      corresponding to @index in the radix tree.  If
506  *      this causes the leaf node to have no tags set then clear the tag in the
507  *      next-to-leaf node, etc.
508  *
509  *      Returns the address of the tagged item on success, else NULL.  ie:
510  *      has the same return value and semantics as radix_tree_lookup().
511  */
512 void *radix_tree_tag_clear(struct radix_tree_root *root,
513                         unsigned long index, unsigned int tag)
514 {
515         /*
516          * The radix tree path needs to be one longer than the maximum path
517          * since the "list" is null terminated.
518          */
519         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
520         struct radix_tree_node *slot = NULL;
521         unsigned int height, shift;
522
523         height = root->height;
524         if (index > radix_tree_maxindex(height))
525                 goto out;
526
527         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
528         pathp->node = NULL;
529         slot = radix_tree_indirect_to_ptr(root->rnode);
530
531         while (height > 0) {
532                 int offset;
533
534                 if (slot == NULL)
535                         goto out;
536
537                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
538                 pathp[1].offset = offset;
539                 pathp[1].node = slot;
540                 slot = slot->slots[offset];
541                 pathp++;
542                 shift -= RADIX_TREE_MAP_SHIFT;
543                 height--;
544         }
545
546         if (slot == NULL)
547                 goto out;
548
549         while (pathp->node) {
550                 if (!tag_get(pathp->node, tag, pathp->offset))
551                         goto out;
552                 tag_clear(pathp->node, tag, pathp->offset);
553                 if (any_tag_set(pathp->node, tag))
554                         goto out;
555                 pathp--;
556         }
557
558         /* clear the root's tag bit */
559         if (root_tag_get(root, tag))
560                 root_tag_clear(root, tag);
561
562 out:
563         return slot;
564 }
565 EXPORT_SYMBOL(radix_tree_tag_clear);
566
567 #ifndef __KERNEL__      /* Only the test harness uses this at present */
568 /**
569  * radix_tree_tag_get - get a tag on a radix tree node
570  * @root:               radix tree root
571  * @index:              index key
572  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
573  *
574  * Return values:
575  *
576  *  0: tag not present or not set
577  *  1: tag set
578  */
579 int radix_tree_tag_get(struct radix_tree_root *root,
580                         unsigned long index, unsigned int tag)
581 {
582         unsigned int height, shift;
583         struct radix_tree_node *node;
584         int saw_unset_tag = 0;
585
586         /* check the root's tag bit */
587         if (!root_tag_get(root, tag))
588                 return 0;
589
590         node = rcu_dereference(root->rnode);
591         if (node == NULL)
592                 return 0;
593
594         if (!radix_tree_is_indirect_ptr(node))
595                 return (index == 0);
596         node = radix_tree_indirect_to_ptr(node);
597
598         height = node->height;
599         if (index > radix_tree_maxindex(height))
600                 return 0;
601
602         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
603
604         for ( ; ; ) {
605                 int offset;
606
607                 if (node == NULL)
608                         return 0;
609
610                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
611
612                 /*
613                  * This is just a debug check.  Later, we can bale as soon as
614                  * we see an unset tag.
615                  */
616                 if (!tag_get(node, tag, offset))
617                         saw_unset_tag = 1;
618                 if (height == 1) {
619                         int ret = tag_get(node, tag, offset);
620
621                         BUG_ON(ret && saw_unset_tag);
622                         return !!ret;
623                 }
624                 node = rcu_dereference(node->slots[offset]);
625                 shift -= RADIX_TREE_MAP_SHIFT;
626                 height--;
627         }
628 }
629 EXPORT_SYMBOL(radix_tree_tag_get);
630 #endif
631
632 /**
633  *      radix_tree_next_hole    -    find the next hole (not-present entry)
634  *      @root:          tree root
635  *      @index:         index key
636  *      @max_scan:      maximum range to search
637  *
638  *      Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
639  *      indexed hole.
640  *
641  *      Returns: the index of the hole if found, otherwise returns an index
642  *      outside of the set specified (in which case 'return - index >= max_scan'
643  *      will be true).
644  *
645  *      radix_tree_next_hole may be called under rcu_read_lock. However, like
646  *      radix_tree_gang_lookup, this will not atomically search a snapshot of the
647  *      tree at a single point in time. For example, if a hole is created at index
648  *      5, then subsequently a hole is created at index 10, radix_tree_next_hole
649  *      covering both indexes may return 10 if called under rcu_read_lock.
650  */
651 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
652                                 unsigned long index, unsigned long max_scan)
653 {
654         unsigned long i;
655
656         for (i = 0; i < max_scan; i++) {
657                 if (!radix_tree_lookup(root, index))
658                         break;
659                 index++;
660                 if (index == 0)
661                         break;
662         }
663
664         return index;
665 }
666 EXPORT_SYMBOL(radix_tree_next_hole);
667
668 static unsigned int
669 __lookup(struct radix_tree_node *slot, void ***results, unsigned long index,
670         unsigned int max_items, unsigned long *next_index)
671 {
672         unsigned int nr_found = 0;
673         unsigned int shift, height;
674         unsigned long i;
675
676         height = slot->height;
677         if (height == 0)
678                 goto out;
679         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
680
681         for ( ; height > 1; height--) {
682                 i = (index >> shift) & RADIX_TREE_MAP_MASK;
683                 for (;;) {
684                         if (slot->slots[i] != NULL)
685                                 break;
686                         index &= ~((1UL << shift) - 1);
687                         index += 1UL << shift;
688                         if (index == 0)
689                                 goto out;       /* 32-bit wraparound */
690                         i++;
691                         if (i == RADIX_TREE_MAP_SIZE)
692                                 goto out;
693                 }
694
695                 shift -= RADIX_TREE_MAP_SHIFT;
696                 slot = rcu_dereference(slot->slots[i]);
697                 if (slot == NULL)
698                         goto out;
699         }
700
701         /* Bottom level: grab some items */
702         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
703                 index++;
704                 if (slot->slots[i]) {
705                         results[nr_found++] = &(slot->slots[i]);
706                         if (nr_found == max_items)
707                                 goto out;
708                 }
709         }
710 out:
711         *next_index = index;
712         return nr_found;
713 }
714
715 /**
716  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
717  *      @root:          radix tree root
718  *      @results:       where the results of the lookup are placed
719  *      @first_index:   start the lookup from this key
720  *      @max_items:     place up to this many items at *results
721  *
722  *      Performs an index-ascending scan of the tree for present items.  Places
723  *      them at *@results and returns the number of items which were placed at
724  *      *@results.
725  *
726  *      The implementation is naive.
727  *
728  *      Like radix_tree_lookup, radix_tree_gang_lookup may be called under
729  *      rcu_read_lock. In this case, rather than the returned results being
730  *      an atomic snapshot of the tree at a single point in time, the semantics
731  *      of an RCU protected gang lookup are as though multiple radix_tree_lookups
732  *      have been issued in individual locks, and results stored in 'results'.
733  */
734 unsigned int
735 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
736                         unsigned long first_index, unsigned int max_items)
737 {
738         unsigned long max_index;
739         struct radix_tree_node *node;
740         unsigned long cur_index = first_index;
741         unsigned int ret;
742
743         node = rcu_dereference(root->rnode);
744         if (!node)
745                 return 0;
746
747         if (!radix_tree_is_indirect_ptr(node)) {
748                 if (first_index > 0)
749                         return 0;
750                 results[0] = node;
751                 return 1;
752         }
753         node = radix_tree_indirect_to_ptr(node);
754
755         max_index = radix_tree_maxindex(node->height);
756
757         ret = 0;
758         while (ret < max_items) {
759                 unsigned int nr_found, slots_found, i;
760                 unsigned long next_index;       /* Index of next search */
761
762                 if (cur_index > max_index)
763                         break;
764                 slots_found = __lookup(node, (void ***)results + ret, cur_index,
765                                         max_items - ret, &next_index);
766                 nr_found = 0;
767                 for (i = 0; i < slots_found; i++) {
768                         struct radix_tree_node *slot;
769                         slot = *(((void ***)results)[ret + i]);
770                         if (!slot)
771                                 continue;
772                         results[ret + nr_found] = rcu_dereference(slot);
773                         nr_found++;
774                 }
775                 ret += nr_found;
776                 if (next_index == 0)
777                         break;
778                 cur_index = next_index;
779         }
780
781         return ret;
782 }
783 EXPORT_SYMBOL(radix_tree_gang_lookup);
784
785 /**
786  *      radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
787  *      @root:          radix tree root
788  *      @results:       where the results of the lookup are placed
789  *      @first_index:   start the lookup from this key
790  *      @max_items:     place up to this many items at *results
791  *
792  *      Performs an index-ascending scan of the tree for present items.  Places
793  *      their slots at *@results and returns the number of items which were
794  *      placed at *@results.
795  *
796  *      The implementation is naive.
797  *
798  *      Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
799  *      be dereferenced with radix_tree_deref_slot, and if using only RCU
800  *      protection, radix_tree_deref_slot may fail requiring a retry.
801  */
802 unsigned int
803 radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
804                         unsigned long first_index, unsigned int max_items)
805 {
806         unsigned long max_index;
807         struct radix_tree_node *node;
808         unsigned long cur_index = first_index;
809         unsigned int ret;
810
811         node = rcu_dereference(root->rnode);
812         if (!node)
813                 return 0;
814
815         if (!radix_tree_is_indirect_ptr(node)) {
816                 if (first_index > 0)
817                         return 0;
818                 results[0] = (void **)&root->rnode;
819                 return 1;
820         }
821         node = radix_tree_indirect_to_ptr(node);
822
823         max_index = radix_tree_maxindex(node->height);
824
825         ret = 0;
826         while (ret < max_items) {
827                 unsigned int slots_found;
828                 unsigned long next_index;       /* Index of next search */
829
830                 if (cur_index > max_index)
831                         break;
832                 slots_found = __lookup(node, results + ret, cur_index,
833                                         max_items - ret, &next_index);
834                 ret += slots_found;
835                 if (next_index == 0)
836                         break;
837                 cur_index = next_index;
838         }
839
840         return ret;
841 }
842 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
843
844 /*
845  * FIXME: the two tag_get()s here should use find_next_bit() instead of
846  * open-coding the search.
847  */
848 static unsigned int
849 __lookup_tag(struct radix_tree_node *slot, void ***results, unsigned long index,
850         unsigned int max_items, unsigned long *next_index, unsigned int tag)
851 {
852         unsigned int nr_found = 0;
853         unsigned int shift, height;
854
855         height = slot->height;
856         if (height == 0)
857                 goto out;
858         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
859
860         while (height > 0) {
861                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
862
863                 for (;;) {
864                         if (tag_get(slot, tag, i))
865                                 break;
866                         index &= ~((1UL << shift) - 1);
867                         index += 1UL << shift;
868                         if (index == 0)
869                                 goto out;       /* 32-bit wraparound */
870                         i++;
871                         if (i == RADIX_TREE_MAP_SIZE)
872                                 goto out;
873                 }
874                 height--;
875                 if (height == 0) {      /* Bottom level: grab some items */
876                         unsigned long j = index & RADIX_TREE_MAP_MASK;
877
878                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
879                                 index++;
880                                 if (!tag_get(slot, tag, j))
881                                         continue;
882                                 /*
883                                  * Even though the tag was found set, we need to
884                                  * recheck that we have a non-NULL node, because
885                                  * if this lookup is lockless, it may have been
886                                  * subsequently deleted.
887                                  *
888                                  * Similar care must be taken in any place that
889                                  * lookup ->slots[x] without a lock (ie. can't
890                                  * rely on its value remaining the same).
891                                  */
892                                 if (slot->slots[j]) {
893                                         results[nr_found++] = &(slot->slots[j]);
894                                         if (nr_found == max_items)
895                                                 goto out;
896                                 }
897                         }
898                 }
899                 shift -= RADIX_TREE_MAP_SHIFT;
900                 slot = rcu_dereference(slot->slots[i]);
901                 if (slot == NULL)
902                         break;
903         }
904 out:
905         *next_index = index;
906         return nr_found;
907 }
908
909 /**
910  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
911  *                                   based on a tag
912  *      @root:          radix tree root
913  *      @results:       where the results of the lookup are placed
914  *      @first_index:   start the lookup from this key
915  *      @max_items:     place up to this many items at *results
916  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
917  *
918  *      Performs an index-ascending scan of the tree for present items which
919  *      have the tag indexed by @tag set.  Places the items at *@results and
920  *      returns the number of items which were placed at *@results.
921  */
922 unsigned int
923 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
924                 unsigned long first_index, unsigned int max_items,
925                 unsigned int tag)
926 {
927         struct radix_tree_node *node;
928         unsigned long max_index;
929         unsigned long cur_index = first_index;
930         unsigned int ret;
931
932         /* check the root's tag bit */
933         if (!root_tag_get(root, tag))
934                 return 0;
935
936         node = rcu_dereference(root->rnode);
937         if (!node)
938                 return 0;
939
940         if (!radix_tree_is_indirect_ptr(node)) {
941                 if (first_index > 0)
942                         return 0;
943                 results[0] = node;
944                 return 1;
945         }
946         node = radix_tree_indirect_to_ptr(node);
947
948         max_index = radix_tree_maxindex(node->height);
949
950         ret = 0;
951         while (ret < max_items) {
952                 unsigned int nr_found, slots_found, i;
953                 unsigned long next_index;       /* Index of next search */
954
955                 if (cur_index > max_index)
956                         break;
957                 slots_found = __lookup_tag(node, (void ***)results + ret,
958                                 cur_index, max_items - ret, &next_index, tag);
959                 nr_found = 0;
960                 for (i = 0; i < slots_found; i++) {
961                         struct radix_tree_node *slot;
962                         slot = *(((void ***)results)[ret + i]);
963                         if (!slot)
964                                 continue;
965                         results[ret + nr_found] = rcu_dereference(slot);
966                         nr_found++;
967                 }
968                 ret += nr_found;
969                 if (next_index == 0)
970                         break;
971                 cur_index = next_index;
972         }
973
974         return ret;
975 }
976 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
977
978 /**
979  *      radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
980  *                                        radix tree based on a tag
981  *      @root:          radix tree root
982  *      @results:       where the results of the lookup are placed
983  *      @first_index:   start the lookup from this key
984  *      @max_items:     place up to this many items at *results
985  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
986  *
987  *      Performs an index-ascending scan of the tree for present items which
988  *      have the tag indexed by @tag set.  Places the slots at *@results and
989  *      returns the number of slots which were placed at *@results.
990  */
991 unsigned int
992 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
993                 unsigned long first_index, unsigned int max_items,
994                 unsigned int tag)
995 {
996         struct radix_tree_node *node;
997         unsigned long max_index;
998         unsigned long cur_index = first_index;
999         unsigned int ret;
1000
1001         /* check the root's tag bit */
1002         if (!root_tag_get(root, tag))
1003                 return 0;
1004
1005         node = rcu_dereference(root->rnode);
1006         if (!node)
1007                 return 0;
1008
1009         if (!radix_tree_is_indirect_ptr(node)) {
1010                 if (first_index > 0)
1011                         return 0;
1012                 results[0] = (void **)&root->rnode;
1013                 return 1;
1014         }
1015         node = radix_tree_indirect_to_ptr(node);
1016
1017         max_index = radix_tree_maxindex(node->height);
1018
1019         ret = 0;
1020         while (ret < max_items) {
1021                 unsigned int slots_found;
1022                 unsigned long next_index;       /* Index of next search */
1023
1024                 if (cur_index > max_index)
1025                         break;
1026                 slots_found = __lookup_tag(node, results + ret,
1027                                 cur_index, max_items - ret, &next_index, tag);
1028                 ret += slots_found;
1029                 if (next_index == 0)
1030                         break;
1031                 cur_index = next_index;
1032         }
1033
1034         return ret;
1035 }
1036 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1037
1038
1039 /**
1040  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
1041  *      @root           radix tree root
1042  */
1043 static inline void radix_tree_shrink(struct radix_tree_root *root)
1044 {
1045         /* try to shrink tree height */
1046         while (root->height > 0) {
1047                 struct radix_tree_node *to_free = root->rnode;
1048                 void *newptr;
1049
1050                 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1051                 to_free = radix_tree_indirect_to_ptr(to_free);
1052
1053                 /*
1054                  * The candidate node has more than one child, or its child
1055                  * is not at the leftmost slot, we cannot shrink.
1056                  */
1057                 if (to_free->count != 1)
1058                         break;
1059                 if (!to_free->slots[0])
1060                         break;
1061
1062                 /*
1063                  * We don't need rcu_assign_pointer(), since we are simply
1064                  * moving the node from one part of the tree to another. If
1065                  * it was safe to dereference the old pointer to it
1066                  * (to_free->slots[0]), it will be safe to dereference the new
1067                  * one (root->rnode).
1068                  */
1069                 newptr = to_free->slots[0];
1070                 if (root->height > 1)
1071                         newptr = radix_tree_ptr_to_indirect(newptr);
1072                 root->rnode = newptr;
1073                 root->height--;
1074                 radix_tree_node_free(to_free);
1075         }
1076 }
1077
1078 /**
1079  *      radix_tree_delete    -    delete an item from a radix tree
1080  *      @root:          radix tree root
1081  *      @index:         index key
1082  *
1083  *      Remove the item at @index from the radix tree rooted at @root.
1084  *
1085  *      Returns the address of the deleted item, or NULL if it was not present.
1086  */
1087 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1088 {
1089         /*
1090          * The radix tree path needs to be one longer than the maximum path
1091          * since the "list" is null terminated.
1092          */
1093         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
1094         struct radix_tree_node *slot = NULL;
1095         struct radix_tree_node *to_free;
1096         unsigned int height, shift;
1097         int tag;
1098         int offset;
1099
1100         height = root->height;
1101         if (index > radix_tree_maxindex(height))
1102                 goto out;
1103
1104         slot = root->rnode;
1105         if (height == 0) {
1106                 root_tag_clear_all(root);
1107                 root->rnode = NULL;
1108                 goto out;
1109         }
1110         slot = radix_tree_indirect_to_ptr(slot);
1111
1112         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
1113         pathp->node = NULL;
1114
1115         do {
1116                 if (slot == NULL)
1117                         goto out;
1118
1119                 pathp++;
1120                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
1121                 pathp->offset = offset;
1122                 pathp->node = slot;
1123                 slot = slot->slots[offset];
1124                 shift -= RADIX_TREE_MAP_SHIFT;
1125                 height--;
1126         } while (height > 0);
1127
1128         if (slot == NULL)
1129                 goto out;
1130
1131         /*
1132          * Clear all tags associated with the just-deleted item
1133          */
1134         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1135                 if (tag_get(pathp->node, tag, pathp->offset))
1136                         radix_tree_tag_clear(root, index, tag);
1137         }
1138
1139         to_free = NULL;
1140         /* Now free the nodes we do not need anymore */
1141         while (pathp->node) {
1142                 pathp->node->slots[pathp->offset] = NULL;
1143                 pathp->node->count--;
1144                 /*
1145                  * Queue the node for deferred freeing after the
1146                  * last reference to it disappears (set NULL, above).
1147                  */
1148                 if (to_free)
1149                         radix_tree_node_free(to_free);
1150
1151                 if (pathp->node->count) {
1152                         if (pathp->node ==
1153                                         radix_tree_indirect_to_ptr(root->rnode))
1154                                 radix_tree_shrink(root);
1155                         goto out;
1156                 }
1157
1158                 /* Node with zero slots in use so free it */
1159                 to_free = pathp->node;
1160                 pathp--;
1161
1162         }
1163         root_tag_clear_all(root);
1164         root->height = 0;
1165         root->rnode = NULL;
1166         if (to_free)
1167                 radix_tree_node_free(to_free);
1168
1169 out:
1170         return slot;
1171 }
1172 EXPORT_SYMBOL(radix_tree_delete);
1173
1174 /**
1175  *      radix_tree_tagged - test whether any items in the tree are tagged
1176  *      @root:          radix tree root
1177  *      @tag:           tag to test
1178  */
1179 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1180 {
1181         return root_tag_get(root, tag);
1182 }
1183 EXPORT_SYMBOL(radix_tree_tagged);
1184
1185 static void
1186 radix_tree_node_ctor(void *node)
1187 {
1188         memset(node, 0, sizeof(struct radix_tree_node));
1189 }
1190
1191 static __init unsigned long __maxindex(unsigned int height)
1192 {
1193         unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1194         int shift = RADIX_TREE_INDEX_BITS - width;
1195
1196         if (shift < 0)
1197                 return ~0UL;
1198         if (shift >= BITS_PER_LONG)
1199                 return 0UL;
1200         return ~0UL >> shift;
1201 }
1202
1203 static __init void radix_tree_init_maxindex(void)
1204 {
1205         unsigned int i;
1206
1207         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1208                 height_to_maxindex[i] = __maxindex(i);
1209 }
1210
1211 static int radix_tree_callback(struct notifier_block *nfb,
1212                             unsigned long action,
1213                             void *hcpu)
1214 {
1215        int cpu = (long)hcpu;
1216        struct radix_tree_preload *rtp;
1217
1218        /* Free per-cpu pool of perloaded nodes */
1219        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1220                rtp = &per_cpu(radix_tree_preloads, cpu);
1221                while (rtp->nr) {
1222                        kmem_cache_free(radix_tree_node_cachep,
1223                                        rtp->nodes[rtp->nr-1]);
1224                        rtp->nodes[rtp->nr-1] = NULL;
1225                        rtp->nr--;
1226                }
1227        }
1228        return NOTIFY_OK;
1229 }
1230
1231 void __init radix_tree_init(void)
1232 {
1233         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1234                         sizeof(struct radix_tree_node), 0,
1235                         SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1236                         radix_tree_node_ctor);
1237         radix_tree_init_maxindex();
1238         hotcpu_notifier(radix_tree_callback, 0);
1239 }