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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 * Copyright (C) 2012 Konstantin Khlebnikov
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2, or (at
11 * your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23#include <linux/errno.h>
24#include <linux/init.h>
25#include <linux/kernel.h>
26#include <linux/export.h>
27#include <linux/radix-tree.h>
28#include <linux/percpu.h>
29#include <linux/slab.h>
30#include <linux/notifier.h>
31#include <linux/cpu.h>
32#include <linux/string.h>
33#include <linux/bitops.h>
34#include <linux/rcupdate.h>
35#include <linux/hardirq.h> /* in_interrupt() */
36
37
38/*
39 * The height_to_maxindex array needs to be one deeper than the maximum
40 * path as height 0 holds only 1 entry.
41 */
42static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
43
44/*
45 * Radix tree node cache.
46 */
47static struct kmem_cache *radix_tree_node_cachep;
48
49/*
50 * The radix tree is variable-height, so an insert operation not only has
51 * to build the branch to its corresponding item, it also has to build the
52 * branch to existing items if the size has to be increased (by
53 * radix_tree_extend).
54 *
55 * The worst case is a zero height tree with just a single item at index 0,
56 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
57 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
58 * Hence:
59 */
60#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
61
62/*
63 * Per-cpu pool of preloaded nodes
64 */
65struct radix_tree_preload {
66 int nr;
67 struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE];
68};
69static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
70
71static inline void *ptr_to_indirect(void *ptr)
72{
73 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
74}
75
76static inline void *indirect_to_ptr(void *ptr)
77{
78 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
79}
80
81static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
82{
83 return root->gfp_mask & __GFP_BITS_MASK;
84}
85
86static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
87 int offset)
88{
89 __set_bit(offset, node->tags[tag]);
90}
91
92static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
93 int offset)
94{
95 __clear_bit(offset, node->tags[tag]);
96}
97
98static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
99 int offset)
100{
101 return test_bit(offset, node->tags[tag]);
102}
103
104static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
105{
106 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
107}
108
109static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
110{
111 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
112}
113
114static inline void root_tag_clear_all(struct radix_tree_root *root)
115{
116 root->gfp_mask &= __GFP_BITS_MASK;
117}
118
119static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
120{
121 return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
122}
123
124/*
125 * Returns 1 if any slot in the node has this tag set.
126 * Otherwise returns 0.
127 */
128static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
129{
130 int idx;
131 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
132 if (node->tags[tag][idx])
133 return 1;
134 }
135 return 0;
136}
137
138/**
139 * radix_tree_find_next_bit - find the next set bit in a memory region
140 *
141 * @addr: The address to base the search on
142 * @size: The bitmap size in bits
143 * @offset: The bitnumber to start searching at
144 *
145 * Unrollable variant of find_next_bit() for constant size arrays.
146 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
147 * Returns next bit offset, or size if nothing found.
148 */
149static __always_inline unsigned long
150radix_tree_find_next_bit(const unsigned long *addr,
151 unsigned long size, unsigned long offset)
152{
153 if (!__builtin_constant_p(size))
154 return find_next_bit(addr, size, offset);
155
156 if (offset < size) {
157 unsigned long tmp;
158
159 addr += offset / BITS_PER_LONG;
160 tmp = *addr >> (offset % BITS_PER_LONG);
161 if (tmp)
162 return __ffs(tmp) + offset;
163 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
164 while (offset < size) {
165 tmp = *++addr;
166 if (tmp)
167 return __ffs(tmp) + offset;
168 offset += BITS_PER_LONG;
169 }
170 }
171 return size;
172}
173
174/*
175 * This assumes that the caller has performed appropriate preallocation, and
176 * that the caller has pinned this thread of control to the current CPU.
177 */
178static struct radix_tree_node *
179radix_tree_node_alloc(struct radix_tree_root *root)
180{
181 struct radix_tree_node *ret = NULL;
182 gfp_t gfp_mask = root_gfp_mask(root);
183
184 /*
185 * Preload code isn't irq safe and it doesn't make sence to use
186 * preloading in the interrupt anyway as all the allocations have to
187 * be atomic. So just do normal allocation when in interrupt.
188 */
189 if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) {
190 struct radix_tree_preload *rtp;
191
192 /*
193 * Provided the caller has preloaded here, we will always
194 * succeed in getting a node here (and never reach
195 * kmem_cache_alloc)
196 */
197 rtp = &__get_cpu_var(radix_tree_preloads);
198 if (rtp->nr) {
199 ret = rtp->nodes[rtp->nr - 1];
200 rtp->nodes[rtp->nr - 1] = NULL;
201 rtp->nr--;
202 }
203 }
204 if (ret == NULL)
205 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
206
207 BUG_ON(radix_tree_is_indirect_ptr(ret));
208 return ret;
209}
210
211static void radix_tree_node_rcu_free(struct rcu_head *head)
212{
213 struct radix_tree_node *node =
214 container_of(head, struct radix_tree_node, rcu_head);
215 int i;
216
217 /*
218 * must only free zeroed nodes into the slab. radix_tree_shrink
219 * can leave us with a non-NULL entry in the first slot, so clear
220 * that here to make sure.
221 */
222 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
223 tag_clear(node, i, 0);
224
225 node->slots[0] = NULL;
226 node->count = 0;
227
228 kmem_cache_free(radix_tree_node_cachep, node);
229}
230
231static inline void
232radix_tree_node_free(struct radix_tree_node *node)
233{
234 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
235}
236
237/*
238 * Load up this CPU's radix_tree_node buffer with sufficient objects to
239 * ensure that the addition of a single element in the tree cannot fail. On
240 * success, return zero, with preemption disabled. On error, return -ENOMEM
241 * with preemption not disabled.
242 *
243 * To make use of this facility, the radix tree must be initialised without
244 * __GFP_WAIT being passed to INIT_RADIX_TREE().
245 */
246static int __radix_tree_preload(gfp_t gfp_mask)
247{
248 struct radix_tree_preload *rtp;
249 struct radix_tree_node *node;
250 int ret = -ENOMEM;
251
252 preempt_disable();
253 rtp = &__get_cpu_var(radix_tree_preloads);
254 while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
255 preempt_enable();
256 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
257 if (node == NULL)
258 goto out;
259 preempt_disable();
260 rtp = &__get_cpu_var(radix_tree_preloads);
261 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
262 rtp->nodes[rtp->nr++] = node;
263 else
264 kmem_cache_free(radix_tree_node_cachep, node);
265 }
266 ret = 0;
267out:
268 return ret;
269}
270
271/*
272 * Load up this CPU's radix_tree_node buffer with sufficient objects to
273 * ensure that the addition of a single element in the tree cannot fail. On
274 * success, return zero, with preemption disabled. On error, return -ENOMEM
275 * with preemption not disabled.
276 *
277 * To make use of this facility, the radix tree must be initialised without
278 * __GFP_WAIT being passed to INIT_RADIX_TREE().
279 */
280int radix_tree_preload(gfp_t gfp_mask)
281{
282 /* Warn on non-sensical use... */
283 WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT));
284 return __radix_tree_preload(gfp_mask);
285}
286EXPORT_SYMBOL(radix_tree_preload);
287
288/*
289 * The same as above function, except we don't guarantee preloading happens.
290 * We do it, if we decide it helps. On success, return zero with preemption
291 * disabled. On error, return -ENOMEM with preemption not disabled.
292 */
293int radix_tree_maybe_preload(gfp_t gfp_mask)
294{
295 if (gfp_mask & __GFP_WAIT)
296 return __radix_tree_preload(gfp_mask);
297 /* Preloading doesn't help anything with this gfp mask, skip it */
298 preempt_disable();
299 return 0;
300}
301EXPORT_SYMBOL(radix_tree_maybe_preload);
302
303/*
304 * Return the maximum key which can be store into a
305 * radix tree with height HEIGHT.
306 */
307static inline unsigned long radix_tree_maxindex(unsigned int height)
308{
309 return height_to_maxindex[height];
310}
311
312/*
313 * Extend a radix tree so it can store key @index.
314 */
315static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
316{
317 struct radix_tree_node *node;
318 struct radix_tree_node *slot;
319 unsigned int height;
320 int tag;
321
322 /* Figure out what the height should be. */
323 height = root->height + 1;
324 while (index > radix_tree_maxindex(height))
325 height++;
326
327 if (root->rnode == NULL) {
328 root->height = height;
329 goto out;
330 }
331
332 do {
333 unsigned int newheight;
334 if (!(node = radix_tree_node_alloc(root)))
335 return -ENOMEM;
336
337 /* Propagate the aggregated tag info into the new root */
338 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
339 if (root_tag_get(root, tag))
340 tag_set(node, tag, 0);
341 }
342
343 /* Increase the height. */
344 newheight = root->height+1;
345 BUG_ON(newheight & ~RADIX_TREE_HEIGHT_MASK);
346 node->path = newheight;
347 node->count = 1;
348 node->parent = NULL;
349 slot = root->rnode;
350 if (newheight > 1) {
351 slot = indirect_to_ptr(slot);
352 slot->parent = node;
353 }
354 node->slots[0] = slot;
355 node = ptr_to_indirect(node);
356 rcu_assign_pointer(root->rnode, node);
357 root->height = newheight;
358 } while (height > root->height);
359out:
360 return 0;
361}
362
363/**
364 * __radix_tree_create - create a slot in a radix tree
365 * @root: radix tree root
366 * @index: index key
367 * @nodep: returns node
368 * @slotp: returns slot
369 *
370 * Create, if necessary, and return the node and slot for an item
371 * at position @index in the radix tree @root.
372 *
373 * Until there is more than one item in the tree, no nodes are
374 * allocated and @root->rnode is used as a direct slot instead of
375 * pointing to a node, in which case *@nodep will be NULL.
376 *
377 * Returns -ENOMEM, or 0 for success.
378 */
379int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
380 struct radix_tree_node **nodep, void ***slotp)
381{
382 struct radix_tree_node *node = NULL, *slot;
383 unsigned int height, shift, offset;
384 int error;
385
386 /* Make sure the tree is high enough. */
387 if (index > radix_tree_maxindex(root->height)) {
388 error = radix_tree_extend(root, index);
389 if (error)
390 return error;
391 }
392
393 slot = indirect_to_ptr(root->rnode);
394
395 height = root->height;
396 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
397
398 offset = 0; /* uninitialised var warning */
399 while (height > 0) {
400 if (slot == NULL) {
401 /* Have to add a child node. */
402 if (!(slot = radix_tree_node_alloc(root)))
403 return -ENOMEM;
404 slot->path = height;
405 slot->parent = node;
406 if (node) {
407 rcu_assign_pointer(node->slots[offset], slot);
408 node->count++;
409 slot->path |= offset << RADIX_TREE_HEIGHT_SHIFT;
410 } else
411 rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
412 }
413
414 /* Go a level down */
415 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
416 node = slot;
417 slot = node->slots[offset];
418 shift -= RADIX_TREE_MAP_SHIFT;
419 height--;
420 }
421
422 if (nodep)
423 *nodep = node;
424 if (slotp)
425 *slotp = node ? node->slots + offset : (void **)&root->rnode;
426 return 0;
427}
428
429/**
430 * radix_tree_insert - insert into a radix tree
431 * @root: radix tree root
432 * @index: index key
433 * @item: item to insert
434 *
435 * Insert an item into the radix tree at position @index.
436 */
437int radix_tree_insert(struct radix_tree_root *root,
438 unsigned long index, void *item)
439{
440 struct radix_tree_node *node;
441 void **slot;
442 int error;
443
444 BUG_ON(radix_tree_is_indirect_ptr(item));
445
446 error = __radix_tree_create(root, index, &node, &slot);
447 if (error)
448 return error;
449 if (*slot != NULL)
450 return -EEXIST;
451 rcu_assign_pointer(*slot, item);
452
453 if (node) {
454 node->count++;
455 BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK));
456 BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK));
457 } else {
458 BUG_ON(root_tag_get(root, 0));
459 BUG_ON(root_tag_get(root, 1));
460 }
461
462 return 0;
463}
464EXPORT_SYMBOL(radix_tree_insert);
465
466/**
467 * __radix_tree_lookup - lookup an item in a radix tree
468 * @root: radix tree root
469 * @index: index key
470 * @nodep: returns node
471 * @slotp: returns slot
472 *
473 * Lookup and return the item at position @index in the radix
474 * tree @root.
475 *
476 * Until there is more than one item in the tree, no nodes are
477 * allocated and @root->rnode is used as a direct slot instead of
478 * pointing to a node, in which case *@nodep will be NULL.
479 */
480void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
481 struct radix_tree_node **nodep, void ***slotp)
482{
483 struct radix_tree_node *node, *parent;
484 unsigned int height, shift;
485 void **slot;
486
487 node = rcu_dereference_raw(root->rnode);
488 if (node == NULL)
489 return NULL;
490
491 if (!radix_tree_is_indirect_ptr(node)) {
492 if (index > 0)
493 return NULL;
494
495 if (nodep)
496 *nodep = NULL;
497 if (slotp)
498 *slotp = (void **)&root->rnode;
499 return node;
500 }
501 node = indirect_to_ptr(node);
502
503 height = node->path & RADIX_TREE_HEIGHT_MASK;
504 if (index > radix_tree_maxindex(height))
505 return NULL;
506
507 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
508
509 do {
510 parent = node;
511 slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK);
512 node = rcu_dereference_raw(*slot);
513 if (node == NULL)
514 return NULL;
515
516 shift -= RADIX_TREE_MAP_SHIFT;
517 height--;
518 } while (height > 0);
519
520 if (nodep)
521 *nodep = parent;
522 if (slotp)
523 *slotp = slot;
524 return node;
525}
526
527/**
528 * radix_tree_lookup_slot - lookup a slot in a radix tree
529 * @root: radix tree root
530 * @index: index key
531 *
532 * Returns: the slot corresponding to the position @index in the
533 * radix tree @root. This is useful for update-if-exists operations.
534 *
535 * This function can be called under rcu_read_lock iff the slot is not
536 * modified by radix_tree_replace_slot, otherwise it must be called
537 * exclusive from other writers. Any dereference of the slot must be done
538 * using radix_tree_deref_slot.
539 */
540void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
541{
542 void **slot;
543
544 if (!__radix_tree_lookup(root, index, NULL, &slot))
545 return NULL;
546 return slot;
547}
548EXPORT_SYMBOL(radix_tree_lookup_slot);
549
550/**
551 * radix_tree_lookup - perform lookup operation on a radix tree
552 * @root: radix tree root
553 * @index: index key
554 *
555 * Lookup the item at the position @index in the radix tree @root.
556 *
557 * This function can be called under rcu_read_lock, however the caller
558 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
559 * them safely). No RCU barriers are required to access or modify the
560 * returned item, however.
561 */
562void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
563{
564 return __radix_tree_lookup(root, index, NULL, NULL);
565}
566EXPORT_SYMBOL(radix_tree_lookup);
567
568/**
569 * radix_tree_tag_set - set a tag on a radix tree node
570 * @root: radix tree root
571 * @index: index key
572 * @tag: tag index
573 *
574 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
575 * corresponding to @index in the radix tree. From
576 * the root all the way down to the leaf node.
577 *
578 * Returns the address of the tagged item. Setting a tag on a not-present
579 * item is a bug.
580 */
581void *radix_tree_tag_set(struct radix_tree_root *root,
582 unsigned long index, unsigned int tag)
583{
584 unsigned int height, shift;
585 struct radix_tree_node *slot;
586
587 height = root->height;
588 BUG_ON(index > radix_tree_maxindex(height));
589
590 slot = indirect_to_ptr(root->rnode);
591 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
592
593 while (height > 0) {
594 int offset;
595
596 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
597 if (!tag_get(slot, tag, offset))
598 tag_set(slot, tag, offset);
599 slot = slot->slots[offset];
600 BUG_ON(slot == NULL);
601 shift -= RADIX_TREE_MAP_SHIFT;
602 height--;
603 }
604
605 /* set the root's tag bit */
606 if (slot && !root_tag_get(root, tag))
607 root_tag_set(root, tag);
608
609 return slot;
610}
611EXPORT_SYMBOL(radix_tree_tag_set);
612
613/**
614 * radix_tree_tag_clear - clear a tag on a radix tree node
615 * @root: radix tree root
616 * @index: index key
617 * @tag: tag index
618 *
619 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
620 * corresponding to @index in the radix tree. If
621 * this causes the leaf node to have no tags set then clear the tag in the
622 * next-to-leaf node, etc.
623 *
624 * Returns the address of the tagged item on success, else NULL. ie:
625 * has the same return value and semantics as radix_tree_lookup().
626 */
627void *radix_tree_tag_clear(struct radix_tree_root *root,
628 unsigned long index, unsigned int tag)
629{
630 struct radix_tree_node *node = NULL;
631 struct radix_tree_node *slot = NULL;
632 unsigned int height, shift;
633 int uninitialized_var(offset);
634
635 height = root->height;
636 if (index > radix_tree_maxindex(height))
637 goto out;
638
639 shift = height * RADIX_TREE_MAP_SHIFT;
640 slot = indirect_to_ptr(root->rnode);
641
642 while (shift) {
643 if (slot == NULL)
644 goto out;
645
646 shift -= RADIX_TREE_MAP_SHIFT;
647 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
648 node = slot;
649 slot = slot->slots[offset];
650 }
651
652 if (slot == NULL)
653 goto out;
654
655 while (node) {
656 if (!tag_get(node, tag, offset))
657 goto out;
658 tag_clear(node, tag, offset);
659 if (any_tag_set(node, tag))
660 goto out;
661
662 index >>= RADIX_TREE_MAP_SHIFT;
663 offset = index & RADIX_TREE_MAP_MASK;
664 node = node->parent;
665 }
666
667 /* clear the root's tag bit */
668 if (root_tag_get(root, tag))
669 root_tag_clear(root, tag);
670
671out:
672 return slot;
673}
674EXPORT_SYMBOL(radix_tree_tag_clear);
675
676/**
677 * radix_tree_tag_get - get a tag on a radix tree node
678 * @root: radix tree root
679 * @index: index key
680 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
681 *
682 * Return values:
683 *
684 * 0: tag not present or not set
685 * 1: tag set
686 *
687 * Note that the return value of this function may not be relied on, even if
688 * the RCU lock is held, unless tag modification and node deletion are excluded
689 * from concurrency.
690 */
691int radix_tree_tag_get(struct radix_tree_root *root,
692 unsigned long index, unsigned int tag)
693{
694 unsigned int height, shift;
695 struct radix_tree_node *node;
696
697 /* check the root's tag bit */
698 if (!root_tag_get(root, tag))
699 return 0;
700
701 node = rcu_dereference_raw(root->rnode);
702 if (node == NULL)
703 return 0;
704
705 if (!radix_tree_is_indirect_ptr(node))
706 return (index == 0);
707 node = indirect_to_ptr(node);
708
709 height = node->path & RADIX_TREE_HEIGHT_MASK;
710 if (index > radix_tree_maxindex(height))
711 return 0;
712
713 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
714
715 for ( ; ; ) {
716 int offset;
717
718 if (node == NULL)
719 return 0;
720
721 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
722 if (!tag_get(node, tag, offset))
723 return 0;
724 if (height == 1)
725 return 1;
726 node = rcu_dereference_raw(node->slots[offset]);
727 shift -= RADIX_TREE_MAP_SHIFT;
728 height--;
729 }
730}
731EXPORT_SYMBOL(radix_tree_tag_get);
732
733/**
734 * radix_tree_next_chunk - find next chunk of slots for iteration
735 *
736 * @root: radix tree root
737 * @iter: iterator state
738 * @flags: RADIX_TREE_ITER_* flags and tag index
739 * Returns: pointer to chunk first slot, or NULL if iteration is over
740 */
741void **radix_tree_next_chunk(struct radix_tree_root *root,
742 struct radix_tree_iter *iter, unsigned flags)
743{
744 unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
745 struct radix_tree_node *rnode, *node;
746 unsigned long index, offset, height;
747
748 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
749 return NULL;
750
751 /*
752 * Catch next_index overflow after ~0UL. iter->index never overflows
753 * during iterating; it can be zero only at the beginning.
754 * And we cannot overflow iter->next_index in a single step,
755 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
756 *
757 * This condition also used by radix_tree_next_slot() to stop
758 * contiguous iterating, and forbid swithing to the next chunk.
759 */
760 index = iter->next_index;
761 if (!index && iter->index)
762 return NULL;
763
764 rnode = rcu_dereference_raw(root->rnode);
765 if (radix_tree_is_indirect_ptr(rnode)) {
766 rnode = indirect_to_ptr(rnode);
767 } else if (rnode && !index) {
768 /* Single-slot tree */
769 iter->index = 0;
770 iter->next_index = 1;
771 iter->tags = 1;
772 return (void **)&root->rnode;
773 } else
774 return NULL;
775
776restart:
777 height = rnode->path & RADIX_TREE_HEIGHT_MASK;
778 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
779 offset = index >> shift;
780
781 /* Index outside of the tree */
782 if (offset >= RADIX_TREE_MAP_SIZE)
783 return NULL;
784
785 node = rnode;
786 while (1) {
787 if ((flags & RADIX_TREE_ITER_TAGGED) ?
788 !test_bit(offset, node->tags[tag]) :
789 !node->slots[offset]) {
790 /* Hole detected */
791 if (flags & RADIX_TREE_ITER_CONTIG)
792 return NULL;
793
794 if (flags & RADIX_TREE_ITER_TAGGED)
795 offset = radix_tree_find_next_bit(
796 node->tags[tag],
797 RADIX_TREE_MAP_SIZE,
798 offset + 1);
799 else
800 while (++offset < RADIX_TREE_MAP_SIZE) {
801 if (node->slots[offset])
802 break;
803 }
804 index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
805 index += offset << shift;
806 /* Overflow after ~0UL */
807 if (!index)
808 return NULL;
809 if (offset == RADIX_TREE_MAP_SIZE)
810 goto restart;
811 }
812
813 /* This is leaf-node */
814 if (!shift)
815 break;
816
817 node = rcu_dereference_raw(node->slots[offset]);
818 if (node == NULL)
819 goto restart;
820 shift -= RADIX_TREE_MAP_SHIFT;
821 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
822 }
823
824 /* Update the iterator state */
825 iter->index = index;
826 iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
827
828 /* Construct iter->tags bit-mask from node->tags[tag] array */
829 if (flags & RADIX_TREE_ITER_TAGGED) {
830 unsigned tag_long, tag_bit;
831
832 tag_long = offset / BITS_PER_LONG;
833 tag_bit = offset % BITS_PER_LONG;
834 iter->tags = node->tags[tag][tag_long] >> tag_bit;
835 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
836 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
837 /* Pick tags from next element */
838 if (tag_bit)
839 iter->tags |= node->tags[tag][tag_long + 1] <<
840 (BITS_PER_LONG - tag_bit);
841 /* Clip chunk size, here only BITS_PER_LONG tags */
842 iter->next_index = index + BITS_PER_LONG;
843 }
844 }
845
846 return node->slots + offset;
847}
848EXPORT_SYMBOL(radix_tree_next_chunk);
849
850/**
851 * radix_tree_range_tag_if_tagged - for each item in given range set given
852 * tag if item has another tag set
853 * @root: radix tree root
854 * @first_indexp: pointer to a starting index of a range to scan
855 * @last_index: last index of a range to scan
856 * @nr_to_tag: maximum number items to tag
857 * @iftag: tag index to test
858 * @settag: tag index to set if tested tag is set
859 *
860 * This function scans range of radix tree from first_index to last_index
861 * (inclusive). For each item in the range if iftag is set, the function sets
862 * also settag. The function stops either after tagging nr_to_tag items or
863 * after reaching last_index.
864 *
865 * The tags must be set from the leaf level only and propagated back up the
866 * path to the root. We must do this so that we resolve the full path before
867 * setting any tags on intermediate nodes. If we set tags as we descend, then
868 * we can get to the leaf node and find that the index that has the iftag
869 * set is outside the range we are scanning. This reults in dangling tags and
870 * can lead to problems with later tag operations (e.g. livelocks on lookups).
871 *
872 * The function returns number of leaves where the tag was set and sets
873 * *first_indexp to the first unscanned index.
874 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
875 * be prepared to handle that.
876 */
877unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
878 unsigned long *first_indexp, unsigned long last_index,
879 unsigned long nr_to_tag,
880 unsigned int iftag, unsigned int settag)
881{
882 unsigned int height = root->height;
883 struct radix_tree_node *node = NULL;
884 struct radix_tree_node *slot;
885 unsigned int shift;
886 unsigned long tagged = 0;
887 unsigned long index = *first_indexp;
888
889 last_index = min(last_index, radix_tree_maxindex(height));
890 if (index > last_index)
891 return 0;
892 if (!nr_to_tag)
893 return 0;
894 if (!root_tag_get(root, iftag)) {
895 *first_indexp = last_index + 1;
896 return 0;
897 }
898 if (height == 0) {
899 *first_indexp = last_index + 1;
900 root_tag_set(root, settag);
901 return 1;
902 }
903
904 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
905 slot = indirect_to_ptr(root->rnode);
906
907 for (;;) {
908 unsigned long upindex;
909 int offset;
910
911 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
912 if (!slot->slots[offset])
913 goto next;
914 if (!tag_get(slot, iftag, offset))
915 goto next;
916 if (shift) {
917 /* Go down one level */
918 shift -= RADIX_TREE_MAP_SHIFT;
919 node = slot;
920 slot = slot->slots[offset];
921 continue;
922 }
923
924 /* tag the leaf */
925 tagged++;
926 tag_set(slot, settag, offset);
927
928 /* walk back up the path tagging interior nodes */
929 upindex = index;
930 while (node) {
931 upindex >>= RADIX_TREE_MAP_SHIFT;
932 offset = upindex & RADIX_TREE_MAP_MASK;
933
934 /* stop if we find a node with the tag already set */
935 if (tag_get(node, settag, offset))
936 break;
937 tag_set(node, settag, offset);
938 node = node->parent;
939 }
940
941 /*
942 * Small optimization: now clear that node pointer.
943 * Since all of this slot's ancestors now have the tag set
944 * from setting it above, we have no further need to walk
945 * back up the tree setting tags, until we update slot to
946 * point to another radix_tree_node.
947 */
948 node = NULL;
949
950next:
951 /* Go to next item at level determined by 'shift' */
952 index = ((index >> shift) + 1) << shift;
953 /* Overflow can happen when last_index is ~0UL... */
954 if (index > last_index || !index)
955 break;
956 if (tagged >= nr_to_tag)
957 break;
958 while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
959 /*
960 * We've fully scanned this node. Go up. Because
961 * last_index is guaranteed to be in the tree, what
962 * we do below cannot wander astray.
963 */
964 slot = slot->parent;
965 shift += RADIX_TREE_MAP_SHIFT;
966 }
967 }
968 /*
969 * We need not to tag the root tag if there is no tag which is set with
970 * settag within the range from *first_indexp to last_index.
971 */
972 if (tagged > 0)
973 root_tag_set(root, settag);
974 *first_indexp = index;
975
976 return tagged;
977}
978EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
979
980/**
981 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
982 * @root: radix tree root
983 * @results: where the results of the lookup are placed
984 * @first_index: start the lookup from this key
985 * @max_items: place up to this many items at *results
986 *
987 * Performs an index-ascending scan of the tree for present items. Places
988 * them at *@results and returns the number of items which were placed at
989 * *@results.
990 *
991 * The implementation is naive.
992 *
993 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
994 * rcu_read_lock. In this case, rather than the returned results being
995 * an atomic snapshot of the tree at a single point in time, the semantics
996 * of an RCU protected gang lookup are as though multiple radix_tree_lookups
997 * have been issued in individual locks, and results stored in 'results'.
998 */
999unsigned int
1000radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
1001 unsigned long first_index, unsigned int max_items)
1002{
1003 struct radix_tree_iter iter;
1004 void **slot;
1005 unsigned int ret = 0;
1006
1007 if (unlikely(!max_items))
1008 return 0;
1009
1010 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1011 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1012 if (!results[ret])
1013 continue;
1014 if (++ret == max_items)
1015 break;
1016 }
1017
1018 return ret;
1019}
1020EXPORT_SYMBOL(radix_tree_gang_lookup);
1021
1022/**
1023 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1024 * @root: radix tree root
1025 * @results: where the results of the lookup are placed
1026 * @indices: where their indices should be placed (but usually NULL)
1027 * @first_index: start the lookup from this key
1028 * @max_items: place up to this many items at *results
1029 *
1030 * Performs an index-ascending scan of the tree for present items. Places
1031 * their slots at *@results and returns the number of items which were
1032 * placed at *@results.
1033 *
1034 * The implementation is naive.
1035 *
1036 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1037 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1038 * protection, radix_tree_deref_slot may fail requiring a retry.
1039 */
1040unsigned int
1041radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1042 void ***results, unsigned long *indices,
1043 unsigned long first_index, unsigned int max_items)
1044{
1045 struct radix_tree_iter iter;
1046 void **slot;
1047 unsigned int ret = 0;
1048
1049 if (unlikely(!max_items))
1050 return 0;
1051
1052 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1053 results[ret] = slot;
1054 if (indices)
1055 indices[ret] = iter.index;
1056 if (++ret == max_items)
1057 break;
1058 }
1059
1060 return ret;
1061}
1062EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1063
1064/**
1065 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1066 * based on a tag
1067 * @root: radix tree root
1068 * @results: where the results of the lookup are placed
1069 * @first_index: start the lookup from this key
1070 * @max_items: place up to this many items at *results
1071 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1072 *
1073 * Performs an index-ascending scan of the tree for present items which
1074 * have the tag indexed by @tag set. Places the items at *@results and
1075 * returns the number of items which were placed at *@results.
1076 */
1077unsigned int
1078radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1079 unsigned long first_index, unsigned int max_items,
1080 unsigned int tag)
1081{
1082 struct radix_tree_iter iter;
1083 void **slot;
1084 unsigned int ret = 0;
1085
1086 if (unlikely(!max_items))
1087 return 0;
1088
1089 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1090 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1091 if (!results[ret])
1092 continue;
1093 if (++ret == max_items)
1094 break;
1095 }
1096
1097 return ret;
1098}
1099EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1100
1101/**
1102 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1103 * radix tree based on a tag
1104 * @root: radix tree root
1105 * @results: where the results of the lookup are placed
1106 * @first_index: start the lookup from this key
1107 * @max_items: place up to this many items at *results
1108 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1109 *
1110 * Performs an index-ascending scan of the tree for present items which
1111 * have the tag indexed by @tag set. Places the slots at *@results and
1112 * returns the number of slots which were placed at *@results.
1113 */
1114unsigned int
1115radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1116 unsigned long first_index, unsigned int max_items,
1117 unsigned int tag)
1118{
1119 struct radix_tree_iter iter;
1120 void **slot;
1121 unsigned int ret = 0;
1122
1123 if (unlikely(!max_items))
1124 return 0;
1125
1126 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1127 results[ret] = slot;
1128 if (++ret == max_items)
1129 break;
1130 }
1131
1132 return ret;
1133}
1134EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1135
1136#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1137#include <linux/sched.h> /* for cond_resched() */
1138
1139/*
1140 * This linear search is at present only useful to shmem_unuse_inode().
1141 */
1142static unsigned long __locate(struct radix_tree_node *slot, void *item,
1143 unsigned long index, unsigned long *found_index)
1144{
1145 unsigned int shift, height;
1146 unsigned long i;
1147
1148 height = slot->path & RADIX_TREE_HEIGHT_MASK;
1149 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1150
1151 for ( ; height > 1; height--) {
1152 i = (index >> shift) & RADIX_TREE_MAP_MASK;
1153 for (;;) {
1154 if (slot->slots[i] != NULL)
1155 break;
1156 index &= ~((1UL << shift) - 1);
1157 index += 1UL << shift;
1158 if (index == 0)
1159 goto out; /* 32-bit wraparound */
1160 i++;
1161 if (i == RADIX_TREE_MAP_SIZE)
1162 goto out;
1163 }
1164
1165 shift -= RADIX_TREE_MAP_SHIFT;
1166 slot = rcu_dereference_raw(slot->slots[i]);
1167 if (slot == NULL)
1168 goto out;
1169 }
1170
1171 /* Bottom level: check items */
1172 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
1173 if (slot->slots[i] == item) {
1174 *found_index = index + i;
1175 index = 0;
1176 goto out;
1177 }
1178 }
1179 index += RADIX_TREE_MAP_SIZE;
1180out:
1181 return index;
1182}
1183
1184/**
1185 * radix_tree_locate_item - search through radix tree for item
1186 * @root: radix tree root
1187 * @item: item to be found
1188 *
1189 * Returns index where item was found, or -1 if not found.
1190 * Caller must hold no lock (since this time-consuming function needs
1191 * to be preemptible), and must check afterwards if item is still there.
1192 */
1193unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1194{
1195 struct radix_tree_node *node;
1196 unsigned long max_index;
1197 unsigned long cur_index = 0;
1198 unsigned long found_index = -1;
1199
1200 do {
1201 rcu_read_lock();
1202 node = rcu_dereference_raw(root->rnode);
1203 if (!radix_tree_is_indirect_ptr(node)) {
1204 rcu_read_unlock();
1205 if (node == item)
1206 found_index = 0;
1207 break;
1208 }
1209
1210 node = indirect_to_ptr(node);
1211 max_index = radix_tree_maxindex(node->path &
1212 RADIX_TREE_HEIGHT_MASK);
1213 if (cur_index > max_index) {
1214 rcu_read_unlock();
1215 break;
1216 }
1217
1218 cur_index = __locate(node, item, cur_index, &found_index);
1219 rcu_read_unlock();
1220 cond_resched();
1221 } while (cur_index != 0 && cur_index <= max_index);
1222
1223 return found_index;
1224}
1225#else
1226unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1227{
1228 return -1;
1229}
1230#endif /* CONFIG_SHMEM && CONFIG_SWAP */
1231
1232/**
1233 * radix_tree_shrink - shrink height of a radix tree to minimal
1234 * @root radix tree root
1235 */
1236static inline void radix_tree_shrink(struct radix_tree_root *root)
1237{
1238 /* try to shrink tree height */
1239 while (root->height > 0) {
1240 struct radix_tree_node *to_free = root->rnode;
1241 struct radix_tree_node *slot;
1242
1243 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1244 to_free = indirect_to_ptr(to_free);
1245
1246 /*
1247 * The candidate node has more than one child, or its child
1248 * is not at the leftmost slot, we cannot shrink.
1249 */
1250 if (to_free->count != 1)
1251 break;
1252 if (!to_free->slots[0])
1253 break;
1254
1255 /*
1256 * We don't need rcu_assign_pointer(), since we are simply
1257 * moving the node from one part of the tree to another: if it
1258 * was safe to dereference the old pointer to it
1259 * (to_free->slots[0]), it will be safe to dereference the new
1260 * one (root->rnode) as far as dependent read barriers go.
1261 */
1262 slot = to_free->slots[0];
1263 if (root->height > 1) {
1264 slot->parent = NULL;
1265 slot = ptr_to_indirect(slot);
1266 }
1267 root->rnode = slot;
1268 root->height--;
1269
1270 /*
1271 * We have a dilemma here. The node's slot[0] must not be
1272 * NULLed in case there are concurrent lookups expecting to
1273 * find the item. However if this was a bottom-level node,
1274 * then it may be subject to the slot pointer being visible
1275 * to callers dereferencing it. If item corresponding to
1276 * slot[0] is subsequently deleted, these callers would expect
1277 * their slot to become empty sooner or later.
1278 *
1279 * For example, lockless pagecache will look up a slot, deref
1280 * the page pointer, and if the page is 0 refcount it means it
1281 * was concurrently deleted from pagecache so try the deref
1282 * again. Fortunately there is already a requirement for logic
1283 * to retry the entire slot lookup -- the indirect pointer
1284 * problem (replacing direct root node with an indirect pointer
1285 * also results in a stale slot). So tag the slot as indirect
1286 * to force callers to retry.
1287 */
1288 if (root->height == 0)
1289 *((unsigned long *)&to_free->slots[0]) |=
1290 RADIX_TREE_INDIRECT_PTR;
1291
1292 radix_tree_node_free(to_free);
1293 }
1294}
1295
1296/**
1297 * __radix_tree_delete_node - try to free node after clearing a slot
1298 * @root: radix tree root
1299 * @index: index key
1300 * @node: node containing @index
1301 *
1302 * After clearing the slot at @index in @node from radix tree
1303 * rooted at @root, call this function to attempt freeing the
1304 * node and shrinking the tree.
1305 *
1306 * Returns %true if @node was freed, %false otherwise.
1307 */
1308bool __radix_tree_delete_node(struct radix_tree_root *root,
1309 struct radix_tree_node *node)
1310{
1311 bool deleted = false;
1312
1313 do {
1314 struct radix_tree_node *parent;
1315
1316 if (node->count) {
1317 if (node == indirect_to_ptr(root->rnode)) {
1318 radix_tree_shrink(root);
1319 if (root->height == 0)
1320 deleted = true;
1321 }
1322 return deleted;
1323 }
1324
1325 parent = node->parent;
1326 if (parent) {
1327 unsigned int offset;
1328
1329 offset = node->path >> RADIX_TREE_HEIGHT_SHIFT;
1330 parent->slots[offset] = NULL;
1331 parent->count--;
1332 } else {
1333 root_tag_clear_all(root);
1334 root->height = 0;
1335 root->rnode = NULL;
1336 }
1337
1338 radix_tree_node_free(node);
1339 deleted = true;
1340
1341 node = parent;
1342 } while (node);
1343
1344 return deleted;
1345}
1346
1347/**
1348 * radix_tree_delete_item - delete an item from a radix tree
1349 * @root: radix tree root
1350 * @index: index key
1351 * @item: expected item
1352 *
1353 * Remove @item at @index from the radix tree rooted at @root.
1354 *
1355 * Returns the address of the deleted item, or NULL if it was not present
1356 * or the entry at the given @index was not @item.
1357 */
1358void *radix_tree_delete_item(struct radix_tree_root *root,
1359 unsigned long index, void *item)
1360{
1361 struct radix_tree_node *node;
1362 unsigned int offset;
1363 void **slot;
1364 void *entry;
1365 int tag;
1366
1367 entry = __radix_tree_lookup(root, index, &node, &slot);
1368 if (!entry)
1369 return NULL;
1370
1371 if (item && entry != item)
1372 return NULL;
1373
1374 if (!node) {
1375 root_tag_clear_all(root);
1376 root->rnode = NULL;
1377 return entry;
1378 }
1379
1380 offset = index & RADIX_TREE_MAP_MASK;
1381
1382 /*
1383 * Clear all tags associated with the item to be deleted.
1384 * This way of doing it would be inefficient, but seldom is any set.
1385 */
1386 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1387 if (tag_get(node, tag, offset))
1388 radix_tree_tag_clear(root, index, tag);
1389 }
1390
1391 node->slots[offset] = NULL;
1392 node->count--;
1393
1394 __radix_tree_delete_node(root, node);
1395
1396 return entry;
1397}
1398EXPORT_SYMBOL(radix_tree_delete_item);
1399
1400/**
1401 * radix_tree_delete - delete an item from a radix tree
1402 * @root: radix tree root
1403 * @index: index key
1404 *
1405 * Remove the item at @index from the radix tree rooted at @root.
1406 *
1407 * Returns the address of the deleted item, or NULL if it was not present.
1408 */
1409void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1410{
1411 return radix_tree_delete_item(root, index, NULL);
1412}
1413EXPORT_SYMBOL(radix_tree_delete);
1414
1415/**
1416 * radix_tree_tagged - test whether any items in the tree are tagged
1417 * @root: radix tree root
1418 * @tag: tag to test
1419 */
1420int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1421{
1422 return root_tag_get(root, tag);
1423}
1424EXPORT_SYMBOL(radix_tree_tagged);
1425
1426static void
1427radix_tree_node_ctor(void *arg)
1428{
1429 struct radix_tree_node *node = arg;
1430
1431 memset(node, 0, sizeof(*node));
1432 INIT_LIST_HEAD(&node->private_list);
1433}
1434
1435static __init unsigned long __maxindex(unsigned int height)
1436{
1437 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1438 int shift = RADIX_TREE_INDEX_BITS - width;
1439
1440 if (shift < 0)
1441 return ~0UL;
1442 if (shift >= BITS_PER_LONG)
1443 return 0UL;
1444 return ~0UL >> shift;
1445}
1446
1447static __init void radix_tree_init_maxindex(void)
1448{
1449 unsigned int i;
1450
1451 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1452 height_to_maxindex[i] = __maxindex(i);
1453}
1454
1455static int radix_tree_callback(struct notifier_block *nfb,
1456 unsigned long action,
1457 void *hcpu)
1458{
1459 int cpu = (long)hcpu;
1460 struct radix_tree_preload *rtp;
1461
1462 /* Free per-cpu pool of perloaded nodes */
1463 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1464 rtp = &per_cpu(radix_tree_preloads, cpu);
1465 while (rtp->nr) {
1466 kmem_cache_free(radix_tree_node_cachep,
1467 rtp->nodes[rtp->nr-1]);
1468 rtp->nodes[rtp->nr-1] = NULL;
1469 rtp->nr--;
1470 }
1471 }
1472 return NOTIFY_OK;
1473}
1474
1475void __init radix_tree_init(void)
1476{
1477 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1478 sizeof(struct radix_tree_node), 0,
1479 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1480 radix_tree_node_ctor);
1481 radix_tree_init_maxindex();
1482 hotcpu_notifier(radix_tree_callback, 0);
1483}
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2001 Momchil Velikov
4 * Portions Copyright (C) 2001 Christoph Hellwig
5 * Copyright (C) 2005 SGI, Christoph Lameter
6 * Copyright (C) 2006 Nick Piggin
7 * Copyright (C) 2012 Konstantin Khlebnikov
8 * Copyright (C) 2016 Intel, Matthew Wilcox
9 * Copyright (C) 2016 Intel, Ross Zwisler
10 */
11
12#include <linux/bitmap.h>
13#include <linux/bitops.h>
14#include <linux/bug.h>
15#include <linux/cpu.h>
16#include <linux/errno.h>
17#include <linux/export.h>
18#include <linux/idr.h>
19#include <linux/init.h>
20#include <linux/kernel.h>
21#include <linux/kmemleak.h>
22#include <linux/percpu.h>
23#include <linux/preempt.h> /* in_interrupt() */
24#include <linux/radix-tree.h>
25#include <linux/rcupdate.h>
26#include <linux/slab.h>
27#include <linux/string.h>
28#include <linux/xarray.h>
29
30/*
31 * Radix tree node cache.
32 */
33struct kmem_cache *radix_tree_node_cachep;
34
35/*
36 * The radix tree is variable-height, so an insert operation not only has
37 * to build the branch to its corresponding item, it also has to build the
38 * branch to existing items if the size has to be increased (by
39 * radix_tree_extend).
40 *
41 * The worst case is a zero height tree with just a single item at index 0,
42 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
43 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
44 * Hence:
45 */
46#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
47
48/*
49 * The IDR does not have to be as high as the radix tree since it uses
50 * signed integers, not unsigned longs.
51 */
52#define IDR_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(int) - 1)
53#define IDR_MAX_PATH (DIV_ROUND_UP(IDR_INDEX_BITS, \
54 RADIX_TREE_MAP_SHIFT))
55#define IDR_PRELOAD_SIZE (IDR_MAX_PATH * 2 - 1)
56
57/*
58 * Per-cpu pool of preloaded nodes
59 */
60DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = {
61 .lock = INIT_LOCAL_LOCK(lock),
62};
63EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads);
64
65static inline struct radix_tree_node *entry_to_node(void *ptr)
66{
67 return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
68}
69
70static inline void *node_to_entry(void *ptr)
71{
72 return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
73}
74
75#define RADIX_TREE_RETRY XA_RETRY_ENTRY
76
77static inline unsigned long
78get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
79{
80 return parent ? slot - parent->slots : 0;
81}
82
83static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
84 struct radix_tree_node **nodep, unsigned long index)
85{
86 unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
87 void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
88
89 *nodep = (void *)entry;
90 return offset;
91}
92
93static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
94{
95 return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
96}
97
98static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
99 int offset)
100{
101 __set_bit(offset, node->tags[tag]);
102}
103
104static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
105 int offset)
106{
107 __clear_bit(offset, node->tags[tag]);
108}
109
110static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
111 int offset)
112{
113 return test_bit(offset, node->tags[tag]);
114}
115
116static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
117{
118 root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
119}
120
121static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
122{
123 root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
124}
125
126static inline void root_tag_clear_all(struct radix_tree_root *root)
127{
128 root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
129}
130
131static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
132{
133 return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
134}
135
136static inline unsigned root_tags_get(const struct radix_tree_root *root)
137{
138 return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
139}
140
141static inline bool is_idr(const struct radix_tree_root *root)
142{
143 return !!(root->xa_flags & ROOT_IS_IDR);
144}
145
146/*
147 * Returns 1 if any slot in the node has this tag set.
148 * Otherwise returns 0.
149 */
150static inline int any_tag_set(const struct radix_tree_node *node,
151 unsigned int tag)
152{
153 unsigned idx;
154 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
155 if (node->tags[tag][idx])
156 return 1;
157 }
158 return 0;
159}
160
161static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
162{
163 bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
164}
165
166/**
167 * radix_tree_find_next_bit - find the next set bit in a memory region
168 *
169 * @node: where to begin the search
170 * @tag: the tag index
171 * @offset: the bitnumber to start searching at
172 *
173 * Unrollable variant of find_next_bit() for constant size arrays.
174 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
175 * Returns next bit offset, or size if nothing found.
176 */
177static __always_inline unsigned long
178radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
179 unsigned long offset)
180{
181 const unsigned long *addr = node->tags[tag];
182
183 if (offset < RADIX_TREE_MAP_SIZE) {
184 unsigned long tmp;
185
186 addr += offset / BITS_PER_LONG;
187 tmp = *addr >> (offset % BITS_PER_LONG);
188 if (tmp)
189 return __ffs(tmp) + offset;
190 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
191 while (offset < RADIX_TREE_MAP_SIZE) {
192 tmp = *++addr;
193 if (tmp)
194 return __ffs(tmp) + offset;
195 offset += BITS_PER_LONG;
196 }
197 }
198 return RADIX_TREE_MAP_SIZE;
199}
200
201static unsigned int iter_offset(const struct radix_tree_iter *iter)
202{
203 return iter->index & RADIX_TREE_MAP_MASK;
204}
205
206/*
207 * The maximum index which can be stored in a radix tree
208 */
209static inline unsigned long shift_maxindex(unsigned int shift)
210{
211 return (RADIX_TREE_MAP_SIZE << shift) - 1;
212}
213
214static inline unsigned long node_maxindex(const struct radix_tree_node *node)
215{
216 return shift_maxindex(node->shift);
217}
218
219static unsigned long next_index(unsigned long index,
220 const struct radix_tree_node *node,
221 unsigned long offset)
222{
223 return (index & ~node_maxindex(node)) + (offset << node->shift);
224}
225
226/*
227 * This assumes that the caller has performed appropriate preallocation, and
228 * that the caller has pinned this thread of control to the current CPU.
229 */
230static struct radix_tree_node *
231radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
232 struct radix_tree_root *root,
233 unsigned int shift, unsigned int offset,
234 unsigned int count, unsigned int nr_values)
235{
236 struct radix_tree_node *ret = NULL;
237
238 /*
239 * Preload code isn't irq safe and it doesn't make sense to use
240 * preloading during an interrupt anyway as all the allocations have
241 * to be atomic. So just do normal allocation when in interrupt.
242 */
243 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
244 struct radix_tree_preload *rtp;
245
246 /*
247 * Even if the caller has preloaded, try to allocate from the
248 * cache first for the new node to get accounted to the memory
249 * cgroup.
250 */
251 ret = kmem_cache_alloc(radix_tree_node_cachep,
252 gfp_mask | __GFP_NOWARN);
253 if (ret)
254 goto out;
255
256 /*
257 * Provided the caller has preloaded here, we will always
258 * succeed in getting a node here (and never reach
259 * kmem_cache_alloc)
260 */
261 rtp = this_cpu_ptr(&radix_tree_preloads);
262 if (rtp->nr) {
263 ret = rtp->nodes;
264 rtp->nodes = ret->parent;
265 rtp->nr--;
266 }
267 /*
268 * Update the allocation stack trace as this is more useful
269 * for debugging.
270 */
271 kmemleak_update_trace(ret);
272 goto out;
273 }
274 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
275out:
276 BUG_ON(radix_tree_is_internal_node(ret));
277 if (ret) {
278 ret->shift = shift;
279 ret->offset = offset;
280 ret->count = count;
281 ret->nr_values = nr_values;
282 ret->parent = parent;
283 ret->array = root;
284 }
285 return ret;
286}
287
288void radix_tree_node_rcu_free(struct rcu_head *head)
289{
290 struct radix_tree_node *node =
291 container_of(head, struct radix_tree_node, rcu_head);
292
293 /*
294 * Must only free zeroed nodes into the slab. We can be left with
295 * non-NULL entries by radix_tree_free_nodes, so clear the entries
296 * and tags here.
297 */
298 memset(node->slots, 0, sizeof(node->slots));
299 memset(node->tags, 0, sizeof(node->tags));
300 INIT_LIST_HEAD(&node->private_list);
301
302 kmem_cache_free(radix_tree_node_cachep, node);
303}
304
305static inline void
306radix_tree_node_free(struct radix_tree_node *node)
307{
308 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
309}
310
311/*
312 * Load up this CPU's radix_tree_node buffer with sufficient objects to
313 * ensure that the addition of a single element in the tree cannot fail. On
314 * success, return zero, with preemption disabled. On error, return -ENOMEM
315 * with preemption not disabled.
316 *
317 * To make use of this facility, the radix tree must be initialised without
318 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
319 */
320static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
321{
322 struct radix_tree_preload *rtp;
323 struct radix_tree_node *node;
324 int ret = -ENOMEM;
325
326 /*
327 * Nodes preloaded by one cgroup can be used by another cgroup, so
328 * they should never be accounted to any particular memory cgroup.
329 */
330 gfp_mask &= ~__GFP_ACCOUNT;
331
332 local_lock(&radix_tree_preloads.lock);
333 rtp = this_cpu_ptr(&radix_tree_preloads);
334 while (rtp->nr < nr) {
335 local_unlock(&radix_tree_preloads.lock);
336 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
337 if (node == NULL)
338 goto out;
339 local_lock(&radix_tree_preloads.lock);
340 rtp = this_cpu_ptr(&radix_tree_preloads);
341 if (rtp->nr < nr) {
342 node->parent = rtp->nodes;
343 rtp->nodes = node;
344 rtp->nr++;
345 } else {
346 kmem_cache_free(radix_tree_node_cachep, node);
347 }
348 }
349 ret = 0;
350out:
351 return ret;
352}
353
354/*
355 * Load up this CPU's radix_tree_node buffer with sufficient objects to
356 * ensure that the addition of a single element in the tree cannot fail. On
357 * success, return zero, with preemption disabled. On error, return -ENOMEM
358 * with preemption not disabled.
359 *
360 * To make use of this facility, the radix tree must be initialised without
361 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
362 */
363int radix_tree_preload(gfp_t gfp_mask)
364{
365 /* Warn on non-sensical use... */
366 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
367 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
368}
369EXPORT_SYMBOL(radix_tree_preload);
370
371/*
372 * The same as above function, except we don't guarantee preloading happens.
373 * We do it, if we decide it helps. On success, return zero with preemption
374 * disabled. On error, return -ENOMEM with preemption not disabled.
375 */
376int radix_tree_maybe_preload(gfp_t gfp_mask)
377{
378 if (gfpflags_allow_blocking(gfp_mask))
379 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
380 /* Preloading doesn't help anything with this gfp mask, skip it */
381 local_lock(&radix_tree_preloads.lock);
382 return 0;
383}
384EXPORT_SYMBOL(radix_tree_maybe_preload);
385
386static unsigned radix_tree_load_root(const struct radix_tree_root *root,
387 struct radix_tree_node **nodep, unsigned long *maxindex)
388{
389 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
390
391 *nodep = node;
392
393 if (likely(radix_tree_is_internal_node(node))) {
394 node = entry_to_node(node);
395 *maxindex = node_maxindex(node);
396 return node->shift + RADIX_TREE_MAP_SHIFT;
397 }
398
399 *maxindex = 0;
400 return 0;
401}
402
403/*
404 * Extend a radix tree so it can store key @index.
405 */
406static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
407 unsigned long index, unsigned int shift)
408{
409 void *entry;
410 unsigned int maxshift;
411 int tag;
412
413 /* Figure out what the shift should be. */
414 maxshift = shift;
415 while (index > shift_maxindex(maxshift))
416 maxshift += RADIX_TREE_MAP_SHIFT;
417
418 entry = rcu_dereference_raw(root->xa_head);
419 if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
420 goto out;
421
422 do {
423 struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
424 root, shift, 0, 1, 0);
425 if (!node)
426 return -ENOMEM;
427
428 if (is_idr(root)) {
429 all_tag_set(node, IDR_FREE);
430 if (!root_tag_get(root, IDR_FREE)) {
431 tag_clear(node, IDR_FREE, 0);
432 root_tag_set(root, IDR_FREE);
433 }
434 } else {
435 /* Propagate the aggregated tag info to the new child */
436 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
437 if (root_tag_get(root, tag))
438 tag_set(node, tag, 0);
439 }
440 }
441
442 BUG_ON(shift > BITS_PER_LONG);
443 if (radix_tree_is_internal_node(entry)) {
444 entry_to_node(entry)->parent = node;
445 } else if (xa_is_value(entry)) {
446 /* Moving a value entry root->xa_head to a node */
447 node->nr_values = 1;
448 }
449 /*
450 * entry was already in the radix tree, so we do not need
451 * rcu_assign_pointer here
452 */
453 node->slots[0] = (void __rcu *)entry;
454 entry = node_to_entry(node);
455 rcu_assign_pointer(root->xa_head, entry);
456 shift += RADIX_TREE_MAP_SHIFT;
457 } while (shift <= maxshift);
458out:
459 return maxshift + RADIX_TREE_MAP_SHIFT;
460}
461
462/**
463 * radix_tree_shrink - shrink radix tree to minimum height
464 * @root: radix tree root
465 */
466static inline bool radix_tree_shrink(struct radix_tree_root *root)
467{
468 bool shrunk = false;
469
470 for (;;) {
471 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
472 struct radix_tree_node *child;
473
474 if (!radix_tree_is_internal_node(node))
475 break;
476 node = entry_to_node(node);
477
478 /*
479 * The candidate node has more than one child, or its child
480 * is not at the leftmost slot, we cannot shrink.
481 */
482 if (node->count != 1)
483 break;
484 child = rcu_dereference_raw(node->slots[0]);
485 if (!child)
486 break;
487
488 /*
489 * For an IDR, we must not shrink entry 0 into the root in
490 * case somebody calls idr_replace() with a pointer that
491 * appears to be an internal entry
492 */
493 if (!node->shift && is_idr(root))
494 break;
495
496 if (radix_tree_is_internal_node(child))
497 entry_to_node(child)->parent = NULL;
498
499 /*
500 * We don't need rcu_assign_pointer(), since we are simply
501 * moving the node from one part of the tree to another: if it
502 * was safe to dereference the old pointer to it
503 * (node->slots[0]), it will be safe to dereference the new
504 * one (root->xa_head) as far as dependent read barriers go.
505 */
506 root->xa_head = (void __rcu *)child;
507 if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
508 root_tag_clear(root, IDR_FREE);
509
510 /*
511 * We have a dilemma here. The node's slot[0] must not be
512 * NULLed in case there are concurrent lookups expecting to
513 * find the item. However if this was a bottom-level node,
514 * then it may be subject to the slot pointer being visible
515 * to callers dereferencing it. If item corresponding to
516 * slot[0] is subsequently deleted, these callers would expect
517 * their slot to become empty sooner or later.
518 *
519 * For example, lockless pagecache will look up a slot, deref
520 * the page pointer, and if the page has 0 refcount it means it
521 * was concurrently deleted from pagecache so try the deref
522 * again. Fortunately there is already a requirement for logic
523 * to retry the entire slot lookup -- the indirect pointer
524 * problem (replacing direct root node with an indirect pointer
525 * also results in a stale slot). So tag the slot as indirect
526 * to force callers to retry.
527 */
528 node->count = 0;
529 if (!radix_tree_is_internal_node(child)) {
530 node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
531 }
532
533 WARN_ON_ONCE(!list_empty(&node->private_list));
534 radix_tree_node_free(node);
535 shrunk = true;
536 }
537
538 return shrunk;
539}
540
541static bool delete_node(struct radix_tree_root *root,
542 struct radix_tree_node *node)
543{
544 bool deleted = false;
545
546 do {
547 struct radix_tree_node *parent;
548
549 if (node->count) {
550 if (node_to_entry(node) ==
551 rcu_dereference_raw(root->xa_head))
552 deleted |= radix_tree_shrink(root);
553 return deleted;
554 }
555
556 parent = node->parent;
557 if (parent) {
558 parent->slots[node->offset] = NULL;
559 parent->count--;
560 } else {
561 /*
562 * Shouldn't the tags already have all been cleared
563 * by the caller?
564 */
565 if (!is_idr(root))
566 root_tag_clear_all(root);
567 root->xa_head = NULL;
568 }
569
570 WARN_ON_ONCE(!list_empty(&node->private_list));
571 radix_tree_node_free(node);
572 deleted = true;
573
574 node = parent;
575 } while (node);
576
577 return deleted;
578}
579
580/**
581 * __radix_tree_create - create a slot in a radix tree
582 * @root: radix tree root
583 * @index: index key
584 * @nodep: returns node
585 * @slotp: returns slot
586 *
587 * Create, if necessary, and return the node and slot for an item
588 * at position @index in the radix tree @root.
589 *
590 * Until there is more than one item in the tree, no nodes are
591 * allocated and @root->xa_head is used as a direct slot instead of
592 * pointing to a node, in which case *@nodep will be NULL.
593 *
594 * Returns -ENOMEM, or 0 for success.
595 */
596static int __radix_tree_create(struct radix_tree_root *root,
597 unsigned long index, struct radix_tree_node **nodep,
598 void __rcu ***slotp)
599{
600 struct radix_tree_node *node = NULL, *child;
601 void __rcu **slot = (void __rcu **)&root->xa_head;
602 unsigned long maxindex;
603 unsigned int shift, offset = 0;
604 unsigned long max = index;
605 gfp_t gfp = root_gfp_mask(root);
606
607 shift = radix_tree_load_root(root, &child, &maxindex);
608
609 /* Make sure the tree is high enough. */
610 if (max > maxindex) {
611 int error = radix_tree_extend(root, gfp, max, shift);
612 if (error < 0)
613 return error;
614 shift = error;
615 child = rcu_dereference_raw(root->xa_head);
616 }
617
618 while (shift > 0) {
619 shift -= RADIX_TREE_MAP_SHIFT;
620 if (child == NULL) {
621 /* Have to add a child node. */
622 child = radix_tree_node_alloc(gfp, node, root, shift,
623 offset, 0, 0);
624 if (!child)
625 return -ENOMEM;
626 rcu_assign_pointer(*slot, node_to_entry(child));
627 if (node)
628 node->count++;
629 } else if (!radix_tree_is_internal_node(child))
630 break;
631
632 /* Go a level down */
633 node = entry_to_node(child);
634 offset = radix_tree_descend(node, &child, index);
635 slot = &node->slots[offset];
636 }
637
638 if (nodep)
639 *nodep = node;
640 if (slotp)
641 *slotp = slot;
642 return 0;
643}
644
645/*
646 * Free any nodes below this node. The tree is presumed to not need
647 * shrinking, and any user data in the tree is presumed to not need a
648 * destructor called on it. If we need to add a destructor, we can
649 * add that functionality later. Note that we may not clear tags or
650 * slots from the tree as an RCU walker may still have a pointer into
651 * this subtree. We could replace the entries with RADIX_TREE_RETRY,
652 * but we'll still have to clear those in rcu_free.
653 */
654static void radix_tree_free_nodes(struct radix_tree_node *node)
655{
656 unsigned offset = 0;
657 struct radix_tree_node *child = entry_to_node(node);
658
659 for (;;) {
660 void *entry = rcu_dereference_raw(child->slots[offset]);
661 if (xa_is_node(entry) && child->shift) {
662 child = entry_to_node(entry);
663 offset = 0;
664 continue;
665 }
666 offset++;
667 while (offset == RADIX_TREE_MAP_SIZE) {
668 struct radix_tree_node *old = child;
669 offset = child->offset + 1;
670 child = child->parent;
671 WARN_ON_ONCE(!list_empty(&old->private_list));
672 radix_tree_node_free(old);
673 if (old == entry_to_node(node))
674 return;
675 }
676 }
677}
678
679static inline int insert_entries(struct radix_tree_node *node,
680 void __rcu **slot, void *item, bool replace)
681{
682 if (*slot)
683 return -EEXIST;
684 rcu_assign_pointer(*slot, item);
685 if (node) {
686 node->count++;
687 if (xa_is_value(item))
688 node->nr_values++;
689 }
690 return 1;
691}
692
693/**
694 * radix_tree_insert - insert into a radix tree
695 * @root: radix tree root
696 * @index: index key
697 * @item: item to insert
698 *
699 * Insert an item into the radix tree at position @index.
700 */
701int radix_tree_insert(struct radix_tree_root *root, unsigned long index,
702 void *item)
703{
704 struct radix_tree_node *node;
705 void __rcu **slot;
706 int error;
707
708 BUG_ON(radix_tree_is_internal_node(item));
709
710 error = __radix_tree_create(root, index, &node, &slot);
711 if (error)
712 return error;
713
714 error = insert_entries(node, slot, item, false);
715 if (error < 0)
716 return error;
717
718 if (node) {
719 unsigned offset = get_slot_offset(node, slot);
720 BUG_ON(tag_get(node, 0, offset));
721 BUG_ON(tag_get(node, 1, offset));
722 BUG_ON(tag_get(node, 2, offset));
723 } else {
724 BUG_ON(root_tags_get(root));
725 }
726
727 return 0;
728}
729EXPORT_SYMBOL(radix_tree_insert);
730
731/**
732 * __radix_tree_lookup - lookup an item in a radix tree
733 * @root: radix tree root
734 * @index: index key
735 * @nodep: returns node
736 * @slotp: returns slot
737 *
738 * Lookup and return the item at position @index in the radix
739 * tree @root.
740 *
741 * Until there is more than one item in the tree, no nodes are
742 * allocated and @root->xa_head is used as a direct slot instead of
743 * pointing to a node, in which case *@nodep will be NULL.
744 */
745void *__radix_tree_lookup(const struct radix_tree_root *root,
746 unsigned long index, struct radix_tree_node **nodep,
747 void __rcu ***slotp)
748{
749 struct radix_tree_node *node, *parent;
750 unsigned long maxindex;
751 void __rcu **slot;
752
753 restart:
754 parent = NULL;
755 slot = (void __rcu **)&root->xa_head;
756 radix_tree_load_root(root, &node, &maxindex);
757 if (index > maxindex)
758 return NULL;
759
760 while (radix_tree_is_internal_node(node)) {
761 unsigned offset;
762
763 parent = entry_to_node(node);
764 offset = radix_tree_descend(parent, &node, index);
765 slot = parent->slots + offset;
766 if (node == RADIX_TREE_RETRY)
767 goto restart;
768 if (parent->shift == 0)
769 break;
770 }
771
772 if (nodep)
773 *nodep = parent;
774 if (slotp)
775 *slotp = slot;
776 return node;
777}
778
779/**
780 * radix_tree_lookup_slot - lookup a slot in a radix tree
781 * @root: radix tree root
782 * @index: index key
783 *
784 * Returns: the slot corresponding to the position @index in the
785 * radix tree @root. This is useful for update-if-exists operations.
786 *
787 * This function can be called under rcu_read_lock iff the slot is not
788 * modified by radix_tree_replace_slot, otherwise it must be called
789 * exclusive from other writers. Any dereference of the slot must be done
790 * using radix_tree_deref_slot.
791 */
792void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
793 unsigned long index)
794{
795 void __rcu **slot;
796
797 if (!__radix_tree_lookup(root, index, NULL, &slot))
798 return NULL;
799 return slot;
800}
801EXPORT_SYMBOL(radix_tree_lookup_slot);
802
803/**
804 * radix_tree_lookup - perform lookup operation on a radix tree
805 * @root: radix tree root
806 * @index: index key
807 *
808 * Lookup the item at the position @index in the radix tree @root.
809 *
810 * This function can be called under rcu_read_lock, however the caller
811 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
812 * them safely). No RCU barriers are required to access or modify the
813 * returned item, however.
814 */
815void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
816{
817 return __radix_tree_lookup(root, index, NULL, NULL);
818}
819EXPORT_SYMBOL(radix_tree_lookup);
820
821static void replace_slot(void __rcu **slot, void *item,
822 struct radix_tree_node *node, int count, int values)
823{
824 if (node && (count || values)) {
825 node->count += count;
826 node->nr_values += values;
827 }
828
829 rcu_assign_pointer(*slot, item);
830}
831
832static bool node_tag_get(const struct radix_tree_root *root,
833 const struct radix_tree_node *node,
834 unsigned int tag, unsigned int offset)
835{
836 if (node)
837 return tag_get(node, tag, offset);
838 return root_tag_get(root, tag);
839}
840
841/*
842 * IDR users want to be able to store NULL in the tree, so if the slot isn't
843 * free, don't adjust the count, even if it's transitioning between NULL and
844 * non-NULL. For the IDA, we mark slots as being IDR_FREE while they still
845 * have empty bits, but it only stores NULL in slots when they're being
846 * deleted.
847 */
848static int calculate_count(struct radix_tree_root *root,
849 struct radix_tree_node *node, void __rcu **slot,
850 void *item, void *old)
851{
852 if (is_idr(root)) {
853 unsigned offset = get_slot_offset(node, slot);
854 bool free = node_tag_get(root, node, IDR_FREE, offset);
855 if (!free)
856 return 0;
857 if (!old)
858 return 1;
859 }
860 return !!item - !!old;
861}
862
863/**
864 * __radix_tree_replace - replace item in a slot
865 * @root: radix tree root
866 * @node: pointer to tree node
867 * @slot: pointer to slot in @node
868 * @item: new item to store in the slot.
869 *
870 * For use with __radix_tree_lookup(). Caller must hold tree write locked
871 * across slot lookup and replacement.
872 */
873void __radix_tree_replace(struct radix_tree_root *root,
874 struct radix_tree_node *node,
875 void __rcu **slot, void *item)
876{
877 void *old = rcu_dereference_raw(*slot);
878 int values = !!xa_is_value(item) - !!xa_is_value(old);
879 int count = calculate_count(root, node, slot, item, old);
880
881 /*
882 * This function supports replacing value entries and
883 * deleting entries, but that needs accounting against the
884 * node unless the slot is root->xa_head.
885 */
886 WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
887 (count || values));
888 replace_slot(slot, item, node, count, values);
889
890 if (!node)
891 return;
892
893 delete_node(root, node);
894}
895
896/**
897 * radix_tree_replace_slot - replace item in a slot
898 * @root: radix tree root
899 * @slot: pointer to slot
900 * @item: new item to store in the slot.
901 *
902 * For use with radix_tree_lookup_slot() and
903 * radix_tree_gang_lookup_tag_slot(). Caller must hold tree write locked
904 * across slot lookup and replacement.
905 *
906 * NOTE: This cannot be used to switch between non-entries (empty slots),
907 * regular entries, and value entries, as that requires accounting
908 * inside the radix tree node. When switching from one type of entry or
909 * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
910 * radix_tree_iter_replace().
911 */
912void radix_tree_replace_slot(struct radix_tree_root *root,
913 void __rcu **slot, void *item)
914{
915 __radix_tree_replace(root, NULL, slot, item);
916}
917EXPORT_SYMBOL(radix_tree_replace_slot);
918
919/**
920 * radix_tree_iter_replace - replace item in a slot
921 * @root: radix tree root
922 * @iter: iterator state
923 * @slot: pointer to slot
924 * @item: new item to store in the slot.
925 *
926 * For use with radix_tree_for_each_slot().
927 * Caller must hold tree write locked.
928 */
929void radix_tree_iter_replace(struct radix_tree_root *root,
930 const struct radix_tree_iter *iter,
931 void __rcu **slot, void *item)
932{
933 __radix_tree_replace(root, iter->node, slot, item);
934}
935
936static void node_tag_set(struct radix_tree_root *root,
937 struct radix_tree_node *node,
938 unsigned int tag, unsigned int offset)
939{
940 while (node) {
941 if (tag_get(node, tag, offset))
942 return;
943 tag_set(node, tag, offset);
944 offset = node->offset;
945 node = node->parent;
946 }
947
948 if (!root_tag_get(root, tag))
949 root_tag_set(root, tag);
950}
951
952/**
953 * radix_tree_tag_set - set a tag on a radix tree node
954 * @root: radix tree root
955 * @index: index key
956 * @tag: tag index
957 *
958 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
959 * corresponding to @index in the radix tree. From
960 * the root all the way down to the leaf node.
961 *
962 * Returns the address of the tagged item. Setting a tag on a not-present
963 * item is a bug.
964 */
965void *radix_tree_tag_set(struct radix_tree_root *root,
966 unsigned long index, unsigned int tag)
967{
968 struct radix_tree_node *node, *parent;
969 unsigned long maxindex;
970
971 radix_tree_load_root(root, &node, &maxindex);
972 BUG_ON(index > maxindex);
973
974 while (radix_tree_is_internal_node(node)) {
975 unsigned offset;
976
977 parent = entry_to_node(node);
978 offset = radix_tree_descend(parent, &node, index);
979 BUG_ON(!node);
980
981 if (!tag_get(parent, tag, offset))
982 tag_set(parent, tag, offset);
983 }
984
985 /* set the root's tag bit */
986 if (!root_tag_get(root, tag))
987 root_tag_set(root, tag);
988
989 return node;
990}
991EXPORT_SYMBOL(radix_tree_tag_set);
992
993static void node_tag_clear(struct radix_tree_root *root,
994 struct radix_tree_node *node,
995 unsigned int tag, unsigned int offset)
996{
997 while (node) {
998 if (!tag_get(node, tag, offset))
999 return;
1000 tag_clear(node, tag, offset);
1001 if (any_tag_set(node, tag))
1002 return;
1003
1004 offset = node->offset;
1005 node = node->parent;
1006 }
1007
1008 /* clear the root's tag bit */
1009 if (root_tag_get(root, tag))
1010 root_tag_clear(root, tag);
1011}
1012
1013/**
1014 * radix_tree_tag_clear - clear a tag on a radix tree node
1015 * @root: radix tree root
1016 * @index: index key
1017 * @tag: tag index
1018 *
1019 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1020 * corresponding to @index in the radix tree. If this causes
1021 * the leaf node to have no tags set then clear the tag in the
1022 * next-to-leaf node, etc.
1023 *
1024 * Returns the address of the tagged item on success, else NULL. ie:
1025 * has the same return value and semantics as radix_tree_lookup().
1026 */
1027void *radix_tree_tag_clear(struct radix_tree_root *root,
1028 unsigned long index, unsigned int tag)
1029{
1030 struct radix_tree_node *node, *parent;
1031 unsigned long maxindex;
1032 int offset;
1033
1034 radix_tree_load_root(root, &node, &maxindex);
1035 if (index > maxindex)
1036 return NULL;
1037
1038 parent = NULL;
1039
1040 while (radix_tree_is_internal_node(node)) {
1041 parent = entry_to_node(node);
1042 offset = radix_tree_descend(parent, &node, index);
1043 }
1044
1045 if (node)
1046 node_tag_clear(root, parent, tag, offset);
1047
1048 return node;
1049}
1050EXPORT_SYMBOL(radix_tree_tag_clear);
1051
1052/**
1053 * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1054 * @root: radix tree root
1055 * @iter: iterator state
1056 * @tag: tag to clear
1057 */
1058void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1059 const struct radix_tree_iter *iter, unsigned int tag)
1060{
1061 node_tag_clear(root, iter->node, tag, iter_offset(iter));
1062}
1063
1064/**
1065 * radix_tree_tag_get - get a tag on a radix tree node
1066 * @root: radix tree root
1067 * @index: index key
1068 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
1069 *
1070 * Return values:
1071 *
1072 * 0: tag not present or not set
1073 * 1: tag set
1074 *
1075 * Note that the return value of this function may not be relied on, even if
1076 * the RCU lock is held, unless tag modification and node deletion are excluded
1077 * from concurrency.
1078 */
1079int radix_tree_tag_get(const struct radix_tree_root *root,
1080 unsigned long index, unsigned int tag)
1081{
1082 struct radix_tree_node *node, *parent;
1083 unsigned long maxindex;
1084
1085 if (!root_tag_get(root, tag))
1086 return 0;
1087
1088 radix_tree_load_root(root, &node, &maxindex);
1089 if (index > maxindex)
1090 return 0;
1091
1092 while (radix_tree_is_internal_node(node)) {
1093 unsigned offset;
1094
1095 parent = entry_to_node(node);
1096 offset = radix_tree_descend(parent, &node, index);
1097
1098 if (!tag_get(parent, tag, offset))
1099 return 0;
1100 if (node == RADIX_TREE_RETRY)
1101 break;
1102 }
1103
1104 return 1;
1105}
1106EXPORT_SYMBOL(radix_tree_tag_get);
1107
1108/* Construct iter->tags bit-mask from node->tags[tag] array */
1109static void set_iter_tags(struct radix_tree_iter *iter,
1110 struct radix_tree_node *node, unsigned offset,
1111 unsigned tag)
1112{
1113 unsigned tag_long = offset / BITS_PER_LONG;
1114 unsigned tag_bit = offset % BITS_PER_LONG;
1115
1116 if (!node) {
1117 iter->tags = 1;
1118 return;
1119 }
1120
1121 iter->tags = node->tags[tag][tag_long] >> tag_bit;
1122
1123 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1124 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1125 /* Pick tags from next element */
1126 if (tag_bit)
1127 iter->tags |= node->tags[tag][tag_long + 1] <<
1128 (BITS_PER_LONG - tag_bit);
1129 /* Clip chunk size, here only BITS_PER_LONG tags */
1130 iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1131 }
1132}
1133
1134void __rcu **radix_tree_iter_resume(void __rcu **slot,
1135 struct radix_tree_iter *iter)
1136{
1137 slot++;
1138 iter->index = __radix_tree_iter_add(iter, 1);
1139 iter->next_index = iter->index;
1140 iter->tags = 0;
1141 return NULL;
1142}
1143EXPORT_SYMBOL(radix_tree_iter_resume);
1144
1145/**
1146 * radix_tree_next_chunk - find next chunk of slots for iteration
1147 *
1148 * @root: radix tree root
1149 * @iter: iterator state
1150 * @flags: RADIX_TREE_ITER_* flags and tag index
1151 * Returns: pointer to chunk first slot, or NULL if iteration is over
1152 */
1153void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1154 struct radix_tree_iter *iter, unsigned flags)
1155{
1156 unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1157 struct radix_tree_node *node, *child;
1158 unsigned long index, offset, maxindex;
1159
1160 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1161 return NULL;
1162
1163 /*
1164 * Catch next_index overflow after ~0UL. iter->index never overflows
1165 * during iterating; it can be zero only at the beginning.
1166 * And we cannot overflow iter->next_index in a single step,
1167 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1168 *
1169 * This condition also used by radix_tree_next_slot() to stop
1170 * contiguous iterating, and forbid switching to the next chunk.
1171 */
1172 index = iter->next_index;
1173 if (!index && iter->index)
1174 return NULL;
1175
1176 restart:
1177 radix_tree_load_root(root, &child, &maxindex);
1178 if (index > maxindex)
1179 return NULL;
1180 if (!child)
1181 return NULL;
1182
1183 if (!radix_tree_is_internal_node(child)) {
1184 /* Single-slot tree */
1185 iter->index = index;
1186 iter->next_index = maxindex + 1;
1187 iter->tags = 1;
1188 iter->node = NULL;
1189 return (void __rcu **)&root->xa_head;
1190 }
1191
1192 do {
1193 node = entry_to_node(child);
1194 offset = radix_tree_descend(node, &child, index);
1195
1196 if ((flags & RADIX_TREE_ITER_TAGGED) ?
1197 !tag_get(node, tag, offset) : !child) {
1198 /* Hole detected */
1199 if (flags & RADIX_TREE_ITER_CONTIG)
1200 return NULL;
1201
1202 if (flags & RADIX_TREE_ITER_TAGGED)
1203 offset = radix_tree_find_next_bit(node, tag,
1204 offset + 1);
1205 else
1206 while (++offset < RADIX_TREE_MAP_SIZE) {
1207 void *slot = rcu_dereference_raw(
1208 node->slots[offset]);
1209 if (slot)
1210 break;
1211 }
1212 index &= ~node_maxindex(node);
1213 index += offset << node->shift;
1214 /* Overflow after ~0UL */
1215 if (!index)
1216 return NULL;
1217 if (offset == RADIX_TREE_MAP_SIZE)
1218 goto restart;
1219 child = rcu_dereference_raw(node->slots[offset]);
1220 }
1221
1222 if (!child)
1223 goto restart;
1224 if (child == RADIX_TREE_RETRY)
1225 break;
1226 } while (node->shift && radix_tree_is_internal_node(child));
1227
1228 /* Update the iterator state */
1229 iter->index = (index &~ node_maxindex(node)) | offset;
1230 iter->next_index = (index | node_maxindex(node)) + 1;
1231 iter->node = node;
1232
1233 if (flags & RADIX_TREE_ITER_TAGGED)
1234 set_iter_tags(iter, node, offset, tag);
1235
1236 return node->slots + offset;
1237}
1238EXPORT_SYMBOL(radix_tree_next_chunk);
1239
1240/**
1241 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1242 * @root: radix tree root
1243 * @results: where the results of the lookup are placed
1244 * @first_index: start the lookup from this key
1245 * @max_items: place up to this many items at *results
1246 *
1247 * Performs an index-ascending scan of the tree for present items. Places
1248 * them at *@results and returns the number of items which were placed at
1249 * *@results.
1250 *
1251 * The implementation is naive.
1252 *
1253 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1254 * rcu_read_lock. In this case, rather than the returned results being
1255 * an atomic snapshot of the tree at a single point in time, the
1256 * semantics of an RCU protected gang lookup are as though multiple
1257 * radix_tree_lookups have been issued in individual locks, and results
1258 * stored in 'results'.
1259 */
1260unsigned int
1261radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1262 unsigned long first_index, unsigned int max_items)
1263{
1264 struct radix_tree_iter iter;
1265 void __rcu **slot;
1266 unsigned int ret = 0;
1267
1268 if (unlikely(!max_items))
1269 return 0;
1270
1271 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1272 results[ret] = rcu_dereference_raw(*slot);
1273 if (!results[ret])
1274 continue;
1275 if (radix_tree_is_internal_node(results[ret])) {
1276 slot = radix_tree_iter_retry(&iter);
1277 continue;
1278 }
1279 if (++ret == max_items)
1280 break;
1281 }
1282
1283 return ret;
1284}
1285EXPORT_SYMBOL(radix_tree_gang_lookup);
1286
1287/**
1288 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1289 * based on a tag
1290 * @root: radix tree root
1291 * @results: where the results of the lookup are placed
1292 * @first_index: start the lookup from this key
1293 * @max_items: place up to this many items at *results
1294 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1295 *
1296 * Performs an index-ascending scan of the tree for present items which
1297 * have the tag indexed by @tag set. Places the items at *@results and
1298 * returns the number of items which were placed at *@results.
1299 */
1300unsigned int
1301radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1302 unsigned long first_index, unsigned int max_items,
1303 unsigned int tag)
1304{
1305 struct radix_tree_iter iter;
1306 void __rcu **slot;
1307 unsigned int ret = 0;
1308
1309 if (unlikely(!max_items))
1310 return 0;
1311
1312 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1313 results[ret] = rcu_dereference_raw(*slot);
1314 if (!results[ret])
1315 continue;
1316 if (radix_tree_is_internal_node(results[ret])) {
1317 slot = radix_tree_iter_retry(&iter);
1318 continue;
1319 }
1320 if (++ret == max_items)
1321 break;
1322 }
1323
1324 return ret;
1325}
1326EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1327
1328/**
1329 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1330 * radix tree based on a tag
1331 * @root: radix tree root
1332 * @results: where the results of the lookup are placed
1333 * @first_index: start the lookup from this key
1334 * @max_items: place up to this many items at *results
1335 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1336 *
1337 * Performs an index-ascending scan of the tree for present items which
1338 * have the tag indexed by @tag set. Places the slots at *@results and
1339 * returns the number of slots which were placed at *@results.
1340 */
1341unsigned int
1342radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1343 void __rcu ***results, unsigned long first_index,
1344 unsigned int max_items, unsigned int tag)
1345{
1346 struct radix_tree_iter iter;
1347 void __rcu **slot;
1348 unsigned int ret = 0;
1349
1350 if (unlikely(!max_items))
1351 return 0;
1352
1353 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1354 results[ret] = slot;
1355 if (++ret == max_items)
1356 break;
1357 }
1358
1359 return ret;
1360}
1361EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1362
1363static bool __radix_tree_delete(struct radix_tree_root *root,
1364 struct radix_tree_node *node, void __rcu **slot)
1365{
1366 void *old = rcu_dereference_raw(*slot);
1367 int values = xa_is_value(old) ? -1 : 0;
1368 unsigned offset = get_slot_offset(node, slot);
1369 int tag;
1370
1371 if (is_idr(root))
1372 node_tag_set(root, node, IDR_FREE, offset);
1373 else
1374 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1375 node_tag_clear(root, node, tag, offset);
1376
1377 replace_slot(slot, NULL, node, -1, values);
1378 return node && delete_node(root, node);
1379}
1380
1381/**
1382 * radix_tree_iter_delete - delete the entry at this iterator position
1383 * @root: radix tree root
1384 * @iter: iterator state
1385 * @slot: pointer to slot
1386 *
1387 * Delete the entry at the position currently pointed to by the iterator.
1388 * This may result in the current node being freed; if it is, the iterator
1389 * is advanced so that it will not reference the freed memory. This
1390 * function may be called without any locking if there are no other threads
1391 * which can access this tree.
1392 */
1393void radix_tree_iter_delete(struct radix_tree_root *root,
1394 struct radix_tree_iter *iter, void __rcu **slot)
1395{
1396 if (__radix_tree_delete(root, iter->node, slot))
1397 iter->index = iter->next_index;
1398}
1399EXPORT_SYMBOL(radix_tree_iter_delete);
1400
1401/**
1402 * radix_tree_delete_item - delete an item from a radix tree
1403 * @root: radix tree root
1404 * @index: index key
1405 * @item: expected item
1406 *
1407 * Remove @item at @index from the radix tree rooted at @root.
1408 *
1409 * Return: the deleted entry, or %NULL if it was not present
1410 * or the entry at the given @index was not @item.
1411 */
1412void *radix_tree_delete_item(struct radix_tree_root *root,
1413 unsigned long index, void *item)
1414{
1415 struct radix_tree_node *node = NULL;
1416 void __rcu **slot = NULL;
1417 void *entry;
1418
1419 entry = __radix_tree_lookup(root, index, &node, &slot);
1420 if (!slot)
1421 return NULL;
1422 if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
1423 get_slot_offset(node, slot))))
1424 return NULL;
1425
1426 if (item && entry != item)
1427 return NULL;
1428
1429 __radix_tree_delete(root, node, slot);
1430
1431 return entry;
1432}
1433EXPORT_SYMBOL(radix_tree_delete_item);
1434
1435/**
1436 * radix_tree_delete - delete an entry from a radix tree
1437 * @root: radix tree root
1438 * @index: index key
1439 *
1440 * Remove the entry at @index from the radix tree rooted at @root.
1441 *
1442 * Return: The deleted entry, or %NULL if it was not present.
1443 */
1444void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1445{
1446 return radix_tree_delete_item(root, index, NULL);
1447}
1448EXPORT_SYMBOL(radix_tree_delete);
1449
1450/**
1451 * radix_tree_tagged - test whether any items in the tree are tagged
1452 * @root: radix tree root
1453 * @tag: tag to test
1454 */
1455int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
1456{
1457 return root_tag_get(root, tag);
1458}
1459EXPORT_SYMBOL(radix_tree_tagged);
1460
1461/**
1462 * idr_preload - preload for idr_alloc()
1463 * @gfp_mask: allocation mask to use for preloading
1464 *
1465 * Preallocate memory to use for the next call to idr_alloc(). This function
1466 * returns with preemption disabled. It will be enabled by idr_preload_end().
1467 */
1468void idr_preload(gfp_t gfp_mask)
1469{
1470 if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
1471 local_lock(&radix_tree_preloads.lock);
1472}
1473EXPORT_SYMBOL(idr_preload);
1474
1475void __rcu **idr_get_free(struct radix_tree_root *root,
1476 struct radix_tree_iter *iter, gfp_t gfp,
1477 unsigned long max)
1478{
1479 struct radix_tree_node *node = NULL, *child;
1480 void __rcu **slot = (void __rcu **)&root->xa_head;
1481 unsigned long maxindex, start = iter->next_index;
1482 unsigned int shift, offset = 0;
1483
1484 grow:
1485 shift = radix_tree_load_root(root, &child, &maxindex);
1486 if (!radix_tree_tagged(root, IDR_FREE))
1487 start = max(start, maxindex + 1);
1488 if (start > max)
1489 return ERR_PTR(-ENOSPC);
1490
1491 if (start > maxindex) {
1492 int error = radix_tree_extend(root, gfp, start, shift);
1493 if (error < 0)
1494 return ERR_PTR(error);
1495 shift = error;
1496 child = rcu_dereference_raw(root->xa_head);
1497 }
1498 if (start == 0 && shift == 0)
1499 shift = RADIX_TREE_MAP_SHIFT;
1500
1501 while (shift) {
1502 shift -= RADIX_TREE_MAP_SHIFT;
1503 if (child == NULL) {
1504 /* Have to add a child node. */
1505 child = radix_tree_node_alloc(gfp, node, root, shift,
1506 offset, 0, 0);
1507 if (!child)
1508 return ERR_PTR(-ENOMEM);
1509 all_tag_set(child, IDR_FREE);
1510 rcu_assign_pointer(*slot, node_to_entry(child));
1511 if (node)
1512 node->count++;
1513 } else if (!radix_tree_is_internal_node(child))
1514 break;
1515
1516 node = entry_to_node(child);
1517 offset = radix_tree_descend(node, &child, start);
1518 if (!tag_get(node, IDR_FREE, offset)) {
1519 offset = radix_tree_find_next_bit(node, IDR_FREE,
1520 offset + 1);
1521 start = next_index(start, node, offset);
1522 if (start > max || start == 0)
1523 return ERR_PTR(-ENOSPC);
1524 while (offset == RADIX_TREE_MAP_SIZE) {
1525 offset = node->offset + 1;
1526 node = node->parent;
1527 if (!node)
1528 goto grow;
1529 shift = node->shift;
1530 }
1531 child = rcu_dereference_raw(node->slots[offset]);
1532 }
1533 slot = &node->slots[offset];
1534 }
1535
1536 iter->index = start;
1537 if (node)
1538 iter->next_index = 1 + min(max, (start | node_maxindex(node)));
1539 else
1540 iter->next_index = 1;
1541 iter->node = node;
1542 set_iter_tags(iter, node, offset, IDR_FREE);
1543
1544 return slot;
1545}
1546
1547/**
1548 * idr_destroy - release all internal memory from an IDR
1549 * @idr: idr handle
1550 *
1551 * After this function is called, the IDR is empty, and may be reused or
1552 * the data structure containing it may be freed.
1553 *
1554 * A typical clean-up sequence for objects stored in an idr tree will use
1555 * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1556 * free the memory used to keep track of those objects.
1557 */
1558void idr_destroy(struct idr *idr)
1559{
1560 struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
1561 if (radix_tree_is_internal_node(node))
1562 radix_tree_free_nodes(node);
1563 idr->idr_rt.xa_head = NULL;
1564 root_tag_set(&idr->idr_rt, IDR_FREE);
1565}
1566EXPORT_SYMBOL(idr_destroy);
1567
1568static void
1569radix_tree_node_ctor(void *arg)
1570{
1571 struct radix_tree_node *node = arg;
1572
1573 memset(node, 0, sizeof(*node));
1574 INIT_LIST_HEAD(&node->private_list);
1575}
1576
1577static int radix_tree_cpu_dead(unsigned int cpu)
1578{
1579 struct radix_tree_preload *rtp;
1580 struct radix_tree_node *node;
1581
1582 /* Free per-cpu pool of preloaded nodes */
1583 rtp = &per_cpu(radix_tree_preloads, cpu);
1584 while (rtp->nr) {
1585 node = rtp->nodes;
1586 rtp->nodes = node->parent;
1587 kmem_cache_free(radix_tree_node_cachep, node);
1588 rtp->nr--;
1589 }
1590 return 0;
1591}
1592
1593void __init radix_tree_init(void)
1594{
1595 int ret;
1596
1597 BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
1598 BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
1599 BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
1600 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1601 sizeof(struct radix_tree_node), 0,
1602 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1603 radix_tree_node_ctor);
1604 ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
1605 NULL, radix_tree_cpu_dead);
1606 WARN_ON(ret < 0);
1607}