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
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.
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.
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.
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() */
39 #define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
41 #define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */
44 #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
45 #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
47 #define RADIX_TREE_TAG_LONGS \
48 ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
50 struct radix_tree_node {
51 unsigned int height; /* Height from the bottom */
54 struct radix_tree_node *parent; /* Used when ascending tree */
55 struct rcu_head rcu_head; /* Used when freeing node */
57 void __rcu *slots[RADIX_TREE_MAP_SIZE];
58 unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
61 #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
62 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
63 RADIX_TREE_MAP_SHIFT))
66 * The height_to_maxindex array needs to be one deeper than the maximum
67 * path as height 0 holds only 1 entry.
69 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
72 * Radix tree node cache.
74 static struct kmem_cache *radix_tree_node_cachep;
77 * The radix tree is variable-height, so an insert operation not only has
78 * to build the branch to its corresponding item, it also has to build the
79 * branch to existing items if the size has to be increased (by
82 * The worst case is a zero height tree with just a single item at index 0,
83 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
84 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
87 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
90 * Per-cpu pool of preloaded nodes
92 struct radix_tree_preload {
94 struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE];
96 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
98 static inline void *ptr_to_indirect(void *ptr)
100 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
103 static inline void *indirect_to_ptr(void *ptr)
105 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
108 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
110 return root->gfp_mask & __GFP_BITS_MASK;
113 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
116 __set_bit(offset, node->tags[tag]);
119 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
122 __clear_bit(offset, node->tags[tag]);
125 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
128 return test_bit(offset, node->tags[tag]);
131 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
133 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
136 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
138 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
141 static inline void root_tag_clear_all(struct radix_tree_root *root)
143 root->gfp_mask &= __GFP_BITS_MASK;
146 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
148 return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
152 * Returns 1 if any slot in the node has this tag set.
153 * Otherwise returns 0.
155 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
158 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
159 if (node->tags[tag][idx])
166 * radix_tree_find_next_bit - find the next set bit in a memory region
168 * @addr: The address to base the search on
169 * @size: The bitmap size in bits
170 * @offset: The bitnumber to start searching at
172 * Unrollable variant of find_next_bit() for constant size arrays.
173 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
174 * Returns next bit offset, or size if nothing found.
176 static __always_inline unsigned long
177 radix_tree_find_next_bit(const unsigned long *addr,
178 unsigned long size, unsigned long offset)
180 if (!__builtin_constant_p(size))
181 return find_next_bit(addr, size, offset);
186 addr += offset / BITS_PER_LONG;
187 tmp = *addr >> (offset % BITS_PER_LONG);
189 return __ffs(tmp) + offset;
190 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
191 while (offset < size) {
194 return __ffs(tmp) + offset;
195 offset += BITS_PER_LONG;
202 * This assumes that the caller has performed appropriate preallocation, and
203 * that the caller has pinned this thread of control to the current CPU.
205 static struct radix_tree_node *
206 radix_tree_node_alloc(struct radix_tree_root *root)
208 struct radix_tree_node *ret = NULL;
209 gfp_t gfp_mask = root_gfp_mask(root);
212 * Preload code isn't irq safe and it doesn't make sence to use
213 * preloading in the interrupt anyway as all the allocations have to
214 * be atomic. So just do normal allocation when in interrupt.
216 if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) {
217 struct radix_tree_preload *rtp;
220 * Provided the caller has preloaded here, we will always
221 * succeed in getting a node here (and never reach
224 rtp = &__get_cpu_var(radix_tree_preloads);
226 ret = rtp->nodes[rtp->nr - 1];
227 rtp->nodes[rtp->nr - 1] = NULL;
232 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
234 BUG_ON(radix_tree_is_indirect_ptr(ret));
238 static void radix_tree_node_rcu_free(struct rcu_head *head)
240 struct radix_tree_node *node =
241 container_of(head, struct radix_tree_node, rcu_head);
245 * must only free zeroed nodes into the slab. radix_tree_shrink
246 * can leave us with a non-NULL entry in the first slot, so clear
247 * that here to make sure.
249 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
250 tag_clear(node, i, 0);
252 node->slots[0] = NULL;
255 kmem_cache_free(radix_tree_node_cachep, node);
259 radix_tree_node_free(struct radix_tree_node *node)
261 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
265 * Load up this CPU's radix_tree_node buffer with sufficient objects to
266 * ensure that the addition of a single element in the tree cannot fail. On
267 * success, return zero, with preemption disabled. On error, return -ENOMEM
268 * with preemption not disabled.
270 * To make use of this facility, the radix tree must be initialised without
271 * __GFP_WAIT being passed to INIT_RADIX_TREE().
273 static int __radix_tree_preload(gfp_t gfp_mask)
275 struct radix_tree_preload *rtp;
276 struct radix_tree_node *node;
280 rtp = &__get_cpu_var(radix_tree_preloads);
281 while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
283 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
287 rtp = &__get_cpu_var(radix_tree_preloads);
288 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
289 rtp->nodes[rtp->nr++] = node;
291 kmem_cache_free(radix_tree_node_cachep, node);
299 * Load up this CPU's radix_tree_node buffer with sufficient objects to
300 * ensure that the addition of a single element in the tree cannot fail. On
301 * success, return zero, with preemption disabled. On error, return -ENOMEM
302 * with preemption not disabled.
304 * To make use of this facility, the radix tree must be initialised without
305 * __GFP_WAIT being passed to INIT_RADIX_TREE().
307 int radix_tree_preload(gfp_t gfp_mask)
309 /* Warn on non-sensical use... */
310 WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT));
311 return __radix_tree_preload(gfp_mask);
313 EXPORT_SYMBOL(radix_tree_preload);
316 * The same as above function, except we don't guarantee preloading happens.
317 * We do it, if we decide it helps. On success, return zero with preemption
318 * disabled. On error, return -ENOMEM with preemption not disabled.
320 int radix_tree_maybe_preload(gfp_t gfp_mask)
322 if (gfp_mask & __GFP_WAIT)
323 return __radix_tree_preload(gfp_mask);
324 /* Preloading doesn't help anything with this gfp mask, skip it */
328 EXPORT_SYMBOL(radix_tree_maybe_preload);
331 * Return the maximum key which can be store into a
332 * radix tree with height HEIGHT.
334 static inline unsigned long radix_tree_maxindex(unsigned int height)
336 return height_to_maxindex[height];
340 * Extend a radix tree so it can store key @index.
342 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
344 struct radix_tree_node *node;
345 struct radix_tree_node *slot;
349 /* Figure out what the height should be. */
350 height = root->height + 1;
351 while (index > radix_tree_maxindex(height))
354 if (root->rnode == NULL) {
355 root->height = height;
360 unsigned int newheight;
361 if (!(node = radix_tree_node_alloc(root)))
364 /* Propagate the aggregated tag info into the new root */
365 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
366 if (root_tag_get(root, tag))
367 tag_set(node, tag, 0);
370 /* Increase the height. */
371 newheight = root->height+1;
372 node->height = newheight;
377 slot = indirect_to_ptr(slot);
380 node->slots[0] = slot;
381 node = ptr_to_indirect(node);
382 rcu_assign_pointer(root->rnode, node);
383 root->height = newheight;
384 } while (height > root->height);
390 * radix_tree_insert - insert into a radix tree
391 * @root: radix tree root
393 * @item: item to insert
395 * Insert an item into the radix tree at position @index.
397 int radix_tree_insert(struct radix_tree_root *root,
398 unsigned long index, void *item)
400 struct radix_tree_node *node = NULL, *slot;
401 unsigned int height, shift;
405 BUG_ON(radix_tree_is_indirect_ptr(item));
407 /* Make sure the tree is high enough. */
408 if (index > radix_tree_maxindex(root->height)) {
409 error = radix_tree_extend(root, index);
414 slot = indirect_to_ptr(root->rnode);
416 height = root->height;
417 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
419 offset = 0; /* uninitialised var warning */
422 /* Have to add a child node. */
423 if (!(slot = radix_tree_node_alloc(root)))
425 slot->height = height;
428 rcu_assign_pointer(node->slots[offset], slot);
431 rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
434 /* Go a level down */
435 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
437 slot = node->slots[offset];
438 shift -= RADIX_TREE_MAP_SHIFT;
447 rcu_assign_pointer(node->slots[offset], item);
448 BUG_ON(tag_get(node, 0, offset));
449 BUG_ON(tag_get(node, 1, offset));
451 rcu_assign_pointer(root->rnode, item);
452 BUG_ON(root_tag_get(root, 0));
453 BUG_ON(root_tag_get(root, 1));
458 EXPORT_SYMBOL(radix_tree_insert);
461 * is_slot == 1 : search for the slot.
462 * is_slot == 0 : search for the node.
464 static void *radix_tree_lookup_element(struct radix_tree_root *root,
465 unsigned long index, int is_slot)
467 unsigned int height, shift;
468 struct radix_tree_node *node, **slot;
470 node = rcu_dereference_raw(root->rnode);
474 if (!radix_tree_is_indirect_ptr(node)) {
477 return is_slot ? (void *)&root->rnode : node;
479 node = indirect_to_ptr(node);
481 height = node->height;
482 if (index > radix_tree_maxindex(height))
485 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
488 slot = (struct radix_tree_node **)
489 (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
490 node = rcu_dereference_raw(*slot);
494 shift -= RADIX_TREE_MAP_SHIFT;
496 } while (height > 0);
498 return is_slot ? (void *)slot : indirect_to_ptr(node);
502 * radix_tree_lookup_slot - lookup a slot in a radix tree
503 * @root: radix tree root
506 * Returns: the slot corresponding to the position @index in the
507 * radix tree @root. This is useful for update-if-exists operations.
509 * This function can be called under rcu_read_lock iff the slot is not
510 * modified by radix_tree_replace_slot, otherwise it must be called
511 * exclusive from other writers. Any dereference of the slot must be done
512 * using radix_tree_deref_slot.
514 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
516 return (void **)radix_tree_lookup_element(root, index, 1);
518 EXPORT_SYMBOL(radix_tree_lookup_slot);
521 * radix_tree_lookup - perform lookup operation on a radix tree
522 * @root: radix tree root
525 * Lookup the item at the position @index in the radix tree @root.
527 * This function can be called under rcu_read_lock, however the caller
528 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
529 * them safely). No RCU barriers are required to access or modify the
530 * returned item, however.
532 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
534 return radix_tree_lookup_element(root, index, 0);
536 EXPORT_SYMBOL(radix_tree_lookup);
539 * radix_tree_tag_set - set a tag on a radix tree node
540 * @root: radix tree root
544 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
545 * corresponding to @index in the radix tree. From
546 * the root all the way down to the leaf node.
548 * Returns the address of the tagged item. Setting a tag on a not-present
551 void *radix_tree_tag_set(struct radix_tree_root *root,
552 unsigned long index, unsigned int tag)
554 unsigned int height, shift;
555 struct radix_tree_node *slot;
557 height = root->height;
558 BUG_ON(index > radix_tree_maxindex(height));
560 slot = indirect_to_ptr(root->rnode);
561 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
566 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
567 if (!tag_get(slot, tag, offset))
568 tag_set(slot, tag, offset);
569 slot = slot->slots[offset];
570 BUG_ON(slot == NULL);
571 shift -= RADIX_TREE_MAP_SHIFT;
575 /* set the root's tag bit */
576 if (slot && !root_tag_get(root, tag))
577 root_tag_set(root, tag);
581 EXPORT_SYMBOL(radix_tree_tag_set);
584 * radix_tree_tag_clear - clear a tag on a radix tree node
585 * @root: radix tree root
589 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
590 * corresponding to @index in the radix tree. If
591 * this causes the leaf node to have no tags set then clear the tag in the
592 * next-to-leaf node, etc.
594 * Returns the address of the tagged item on success, else NULL. ie:
595 * has the same return value and semantics as radix_tree_lookup().
597 void *radix_tree_tag_clear(struct radix_tree_root *root,
598 unsigned long index, unsigned int tag)
600 struct radix_tree_node *node = NULL;
601 struct radix_tree_node *slot = NULL;
602 unsigned int height, shift;
603 int uninitialized_var(offset);
605 height = root->height;
606 if (index > radix_tree_maxindex(height))
609 shift = height * RADIX_TREE_MAP_SHIFT;
610 slot = indirect_to_ptr(root->rnode);
616 shift -= RADIX_TREE_MAP_SHIFT;
617 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
619 slot = slot->slots[offset];
626 if (!tag_get(node, tag, offset))
628 tag_clear(node, tag, offset);
629 if (any_tag_set(node, tag))
632 index >>= RADIX_TREE_MAP_SHIFT;
633 offset = index & RADIX_TREE_MAP_MASK;
637 /* clear the root's tag bit */
638 if (root_tag_get(root, tag))
639 root_tag_clear(root, tag);
644 EXPORT_SYMBOL(radix_tree_tag_clear);
647 * radix_tree_tag_get - get a tag on a radix tree node
648 * @root: radix tree root
650 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
654 * 0: tag not present or not set
657 * Note that the return value of this function may not be relied on, even if
658 * the RCU lock is held, unless tag modification and node deletion are excluded
661 int radix_tree_tag_get(struct radix_tree_root *root,
662 unsigned long index, unsigned int tag)
664 unsigned int height, shift;
665 struct radix_tree_node *node;
667 /* check the root's tag bit */
668 if (!root_tag_get(root, tag))
671 node = rcu_dereference_raw(root->rnode);
675 if (!radix_tree_is_indirect_ptr(node))
677 node = indirect_to_ptr(node);
679 height = node->height;
680 if (index > radix_tree_maxindex(height))
683 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
691 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
692 if (!tag_get(node, tag, offset))
696 node = rcu_dereference_raw(node->slots[offset]);
697 shift -= RADIX_TREE_MAP_SHIFT;
701 EXPORT_SYMBOL(radix_tree_tag_get);
704 * radix_tree_next_chunk - find next chunk of slots for iteration
706 * @root: radix tree root
707 * @iter: iterator state
708 * @flags: RADIX_TREE_ITER_* flags and tag index
709 * Returns: pointer to chunk first slot, or NULL if iteration is over
711 void **radix_tree_next_chunk(struct radix_tree_root *root,
712 struct radix_tree_iter *iter, unsigned flags)
714 unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
715 struct radix_tree_node *rnode, *node;
716 unsigned long index, offset;
718 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
722 * Catch next_index overflow after ~0UL. iter->index never overflows
723 * during iterating; it can be zero only at the beginning.
724 * And we cannot overflow iter->next_index in a single step,
725 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
727 * This condition also used by radix_tree_next_slot() to stop
728 * contiguous iterating, and forbid swithing to the next chunk.
730 index = iter->next_index;
731 if (!index && iter->index)
734 rnode = rcu_dereference_raw(root->rnode);
735 if (radix_tree_is_indirect_ptr(rnode)) {
736 rnode = indirect_to_ptr(rnode);
737 } else if (rnode && !index) {
738 /* Single-slot tree */
740 iter->next_index = 1;
742 return (void **)&root->rnode;
747 shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
748 offset = index >> shift;
750 /* Index outside of the tree */
751 if (offset >= RADIX_TREE_MAP_SIZE)
756 if ((flags & RADIX_TREE_ITER_TAGGED) ?
757 !test_bit(offset, node->tags[tag]) :
758 !node->slots[offset]) {
760 if (flags & RADIX_TREE_ITER_CONTIG)
763 if (flags & RADIX_TREE_ITER_TAGGED)
764 offset = radix_tree_find_next_bit(
769 while (++offset < RADIX_TREE_MAP_SIZE) {
770 if (node->slots[offset])
773 index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
774 index += offset << shift;
775 /* Overflow after ~0UL */
778 if (offset == RADIX_TREE_MAP_SIZE)
782 /* This is leaf-node */
786 node = rcu_dereference_raw(node->slots[offset]);
789 shift -= RADIX_TREE_MAP_SHIFT;
790 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
793 /* Update the iterator state */
795 iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
797 /* Construct iter->tags bit-mask from node->tags[tag] array */
798 if (flags & RADIX_TREE_ITER_TAGGED) {
799 unsigned tag_long, tag_bit;
801 tag_long = offset / BITS_PER_LONG;
802 tag_bit = offset % BITS_PER_LONG;
803 iter->tags = node->tags[tag][tag_long] >> tag_bit;
804 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
805 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
806 /* Pick tags from next element */
808 iter->tags |= node->tags[tag][tag_long + 1] <<
809 (BITS_PER_LONG - tag_bit);
810 /* Clip chunk size, here only BITS_PER_LONG tags */
811 iter->next_index = index + BITS_PER_LONG;
815 return node->slots + offset;
817 EXPORT_SYMBOL(radix_tree_next_chunk);
820 * radix_tree_range_tag_if_tagged - for each item in given range set given
821 * tag if item has another tag set
822 * @root: radix tree root
823 * @first_indexp: pointer to a starting index of a range to scan
824 * @last_index: last index of a range to scan
825 * @nr_to_tag: maximum number items to tag
826 * @iftag: tag index to test
827 * @settag: tag index to set if tested tag is set
829 * This function scans range of radix tree from first_index to last_index
830 * (inclusive). For each item in the range if iftag is set, the function sets
831 * also settag. The function stops either after tagging nr_to_tag items or
832 * after reaching last_index.
834 * The tags must be set from the leaf level only and propagated back up the
835 * path to the root. We must do this so that we resolve the full path before
836 * setting any tags on intermediate nodes. If we set tags as we descend, then
837 * we can get to the leaf node and find that the index that has the iftag
838 * set is outside the range we are scanning. This reults in dangling tags and
839 * can lead to problems with later tag operations (e.g. livelocks on lookups).
841 * The function returns number of leaves where the tag was set and sets
842 * *first_indexp to the first unscanned index.
843 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
844 * be prepared to handle that.
846 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
847 unsigned long *first_indexp, unsigned long last_index,
848 unsigned long nr_to_tag,
849 unsigned int iftag, unsigned int settag)
851 unsigned int height = root->height;
852 struct radix_tree_node *node = NULL;
853 struct radix_tree_node *slot;
855 unsigned long tagged = 0;
856 unsigned long index = *first_indexp;
858 last_index = min(last_index, radix_tree_maxindex(height));
859 if (index > last_index)
863 if (!root_tag_get(root, iftag)) {
864 *first_indexp = last_index + 1;
868 *first_indexp = last_index + 1;
869 root_tag_set(root, settag);
873 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
874 slot = indirect_to_ptr(root->rnode);
877 unsigned long upindex;
880 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
881 if (!slot->slots[offset])
883 if (!tag_get(slot, iftag, offset))
886 /* Go down one level */
887 shift -= RADIX_TREE_MAP_SHIFT;
889 slot = slot->slots[offset];
895 tag_set(slot, settag, offset);
897 /* walk back up the path tagging interior nodes */
900 upindex >>= RADIX_TREE_MAP_SHIFT;
901 offset = upindex & RADIX_TREE_MAP_MASK;
903 /* stop if we find a node with the tag already set */
904 if (tag_get(node, settag, offset))
906 tag_set(node, settag, offset);
911 * Small optimization: now clear that node pointer.
912 * Since all of this slot's ancestors now have the tag set
913 * from setting it above, we have no further need to walk
914 * back up the tree setting tags, until we update slot to
915 * point to another radix_tree_node.
920 /* Go to next item at level determined by 'shift' */
921 index = ((index >> shift) + 1) << shift;
922 /* Overflow can happen when last_index is ~0UL... */
923 if (index > last_index || !index)
925 if (tagged >= nr_to_tag)
927 while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
929 * We've fully scanned this node. Go up. Because
930 * last_index is guaranteed to be in the tree, what
931 * we do below cannot wander astray.
934 shift += RADIX_TREE_MAP_SHIFT;
938 * We need not to tag the root tag if there is no tag which is set with
939 * settag within the range from *first_indexp to last_index.
942 root_tag_set(root, settag);
943 *first_indexp = index;
947 EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
951 * radix_tree_next_hole - find the next hole (not-present entry)
954 * @max_scan: maximum range to search
956 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
959 * Returns: the index of the hole if found, otherwise returns an index
960 * outside of the set specified (in which case 'return - index >= max_scan'
961 * will be true). In rare cases of index wrap-around, 0 will be returned.
963 * radix_tree_next_hole may be called under rcu_read_lock. However, like
964 * radix_tree_gang_lookup, this will not atomically search a snapshot of
965 * the tree at a single point in time. For example, if a hole is created
966 * at index 5, then subsequently a hole is created at index 10,
967 * radix_tree_next_hole covering both indexes may return 10 if called
968 * under rcu_read_lock.
970 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
971 unsigned long index, unsigned long max_scan)
975 for (i = 0; i < max_scan; i++) {
976 if (!radix_tree_lookup(root, index))
985 EXPORT_SYMBOL(radix_tree_next_hole);
988 * radix_tree_prev_hole - find the prev hole (not-present entry)
991 * @max_scan: maximum range to search
993 * Search backwards in the range [max(index-max_scan+1, 0), index]
994 * for the first hole.
996 * Returns: the index of the hole if found, otherwise returns an index
997 * outside of the set specified (in which case 'index - return >= max_scan'
998 * will be true). In rare cases of wrap-around, ULONG_MAX will be returned.
1000 * radix_tree_next_hole may be called under rcu_read_lock. However, like
1001 * radix_tree_gang_lookup, this will not atomically search a snapshot of
1002 * the tree at a single point in time. For example, if a hole is created
1003 * at index 10, then subsequently a hole is created at index 5,
1004 * radix_tree_prev_hole covering both indexes may return 5 if called under
1007 unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
1008 unsigned long index, unsigned long max_scan)
1012 for (i = 0; i < max_scan; i++) {
1013 if (!radix_tree_lookup(root, index))
1016 if (index == ULONG_MAX)
1022 EXPORT_SYMBOL(radix_tree_prev_hole);
1025 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1026 * @root: radix tree root
1027 * @results: where the results of the lookup are placed
1028 * @first_index: start the lookup from this key
1029 * @max_items: place up to this many items at *results
1031 * Performs an index-ascending scan of the tree for present items. Places
1032 * them at *@results and returns the number of items which were placed at
1035 * The implementation is naive.
1037 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1038 * rcu_read_lock. In this case, rather than the returned results being
1039 * an atomic snapshot of the tree at a single point in time, the semantics
1040 * of an RCU protected gang lookup are as though multiple radix_tree_lookups
1041 * have been issued in individual locks, and results stored in 'results'.
1044 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
1045 unsigned long first_index, unsigned int max_items)
1047 struct radix_tree_iter iter;
1049 unsigned int ret = 0;
1051 if (unlikely(!max_items))
1054 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1055 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1058 if (++ret == max_items)
1064 EXPORT_SYMBOL(radix_tree_gang_lookup);
1067 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1068 * @root: radix tree root
1069 * @results: where the results of the lookup are placed
1070 * @indices: where their indices should be placed (but usually NULL)
1071 * @first_index: start the lookup from this key
1072 * @max_items: place up to this many items at *results
1074 * Performs an index-ascending scan of the tree for present items. Places
1075 * their slots at *@results and returns the number of items which were
1076 * placed at *@results.
1078 * The implementation is naive.
1080 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1081 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1082 * protection, radix_tree_deref_slot may fail requiring a retry.
1085 radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1086 void ***results, unsigned long *indices,
1087 unsigned long first_index, unsigned int max_items)
1089 struct radix_tree_iter iter;
1091 unsigned int ret = 0;
1093 if (unlikely(!max_items))
1096 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1097 results[ret] = slot;
1099 indices[ret] = iter.index;
1100 if (++ret == max_items)
1106 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1109 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1111 * @root: radix tree root
1112 * @results: where the results of the lookup are placed
1113 * @first_index: start the lookup from this key
1114 * @max_items: place up to this many items at *results
1115 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1117 * Performs an index-ascending scan of the tree for present items which
1118 * have the tag indexed by @tag set. Places the items at *@results and
1119 * returns the number of items which were placed at *@results.
1122 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1123 unsigned long first_index, unsigned int max_items,
1126 struct radix_tree_iter iter;
1128 unsigned int ret = 0;
1130 if (unlikely(!max_items))
1133 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1134 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1137 if (++ret == max_items)
1143 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1146 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1147 * radix tree based on a tag
1148 * @root: radix tree root
1149 * @results: where the results of the lookup are placed
1150 * @first_index: start the lookup from this key
1151 * @max_items: place up to this many items at *results
1152 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1154 * Performs an index-ascending scan of the tree for present items which
1155 * have the tag indexed by @tag set. Places the slots at *@results and
1156 * returns the number of slots which were placed at *@results.
1159 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1160 unsigned long first_index, unsigned int max_items,
1163 struct radix_tree_iter iter;
1165 unsigned int ret = 0;
1167 if (unlikely(!max_items))
1170 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1171 results[ret] = slot;
1172 if (++ret == max_items)
1178 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1180 #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1181 #include <linux/sched.h> /* for cond_resched() */
1184 * This linear search is at present only useful to shmem_unuse_inode().
1186 static unsigned long __locate(struct radix_tree_node *slot, void *item,
1187 unsigned long index, unsigned long *found_index)
1189 unsigned int shift, height;
1192 height = slot->height;
1193 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1195 for ( ; height > 1; height--) {
1196 i = (index >> shift) & RADIX_TREE_MAP_MASK;
1198 if (slot->slots[i] != NULL)
1200 index &= ~((1UL << shift) - 1);
1201 index += 1UL << shift;
1203 goto out; /* 32-bit wraparound */
1205 if (i == RADIX_TREE_MAP_SIZE)
1209 shift -= RADIX_TREE_MAP_SHIFT;
1210 slot = rcu_dereference_raw(slot->slots[i]);
1215 /* Bottom level: check items */
1216 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
1217 if (slot->slots[i] == item) {
1218 *found_index = index + i;
1223 index += RADIX_TREE_MAP_SIZE;
1229 * radix_tree_locate_item - search through radix tree for item
1230 * @root: radix tree root
1231 * @item: item to be found
1233 * Returns index where item was found, or -1 if not found.
1234 * Caller must hold no lock (since this time-consuming function needs
1235 * to be preemptible), and must check afterwards if item is still there.
1237 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1239 struct radix_tree_node *node;
1240 unsigned long max_index;
1241 unsigned long cur_index = 0;
1242 unsigned long found_index = -1;
1246 node = rcu_dereference_raw(root->rnode);
1247 if (!radix_tree_is_indirect_ptr(node)) {
1254 node = indirect_to_ptr(node);
1255 max_index = radix_tree_maxindex(node->height);
1256 if (cur_index > max_index)
1259 cur_index = __locate(node, item, cur_index, &found_index);
1262 } while (cur_index != 0 && cur_index <= max_index);
1267 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1271 #endif /* CONFIG_SHMEM && CONFIG_SWAP */
1274 * radix_tree_shrink - shrink height of a radix tree to minimal
1275 * @root radix tree root
1277 static inline void radix_tree_shrink(struct radix_tree_root *root)
1279 /* try to shrink tree height */
1280 while (root->height > 0) {
1281 struct radix_tree_node *to_free = root->rnode;
1282 struct radix_tree_node *slot;
1284 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1285 to_free = indirect_to_ptr(to_free);
1288 * The candidate node has more than one child, or its child
1289 * is not at the leftmost slot, we cannot shrink.
1291 if (to_free->count != 1)
1293 if (!to_free->slots[0])
1297 * We don't need rcu_assign_pointer(), since we are simply
1298 * moving the node from one part of the tree to another: if it
1299 * was safe to dereference the old pointer to it
1300 * (to_free->slots[0]), it will be safe to dereference the new
1301 * one (root->rnode) as far as dependent read barriers go.
1303 slot = to_free->slots[0];
1304 if (root->height > 1) {
1305 slot->parent = NULL;
1306 slot = ptr_to_indirect(slot);
1312 * We have a dilemma here. The node's slot[0] must not be
1313 * NULLed in case there are concurrent lookups expecting to
1314 * find the item. However if this was a bottom-level node,
1315 * then it may be subject to the slot pointer being visible
1316 * to callers dereferencing it. If item corresponding to
1317 * slot[0] is subsequently deleted, these callers would expect
1318 * their slot to become empty sooner or later.
1320 * For example, lockless pagecache will look up a slot, deref
1321 * the page pointer, and if the page is 0 refcount it means it
1322 * was concurrently deleted from pagecache so try the deref
1323 * again. Fortunately there is already a requirement for logic
1324 * to retry the entire slot lookup -- the indirect pointer
1325 * problem (replacing direct root node with an indirect pointer
1326 * also results in a stale slot). So tag the slot as indirect
1327 * to force callers to retry.
1329 if (root->height == 0)
1330 *((unsigned long *)&to_free->slots[0]) |=
1331 RADIX_TREE_INDIRECT_PTR;
1333 radix_tree_node_free(to_free);
1338 * radix_tree_delete - delete an item from a radix tree
1339 * @root: radix tree root
1342 * Remove the item at @index from the radix tree rooted at @root.
1344 * Returns the address of the deleted item, or NULL if it was not present.
1346 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1348 struct radix_tree_node *node = NULL;
1349 struct radix_tree_node *slot = NULL;
1350 struct radix_tree_node *to_free;
1351 unsigned int height, shift;
1353 int uninitialized_var(offset);
1355 height = root->height;
1356 if (index > radix_tree_maxindex(height))
1361 root_tag_clear_all(root);
1365 slot = indirect_to_ptr(slot);
1366 shift = height * RADIX_TREE_MAP_SHIFT;
1372 shift -= RADIX_TREE_MAP_SHIFT;
1373 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
1375 slot = slot->slots[offset];
1382 * Clear all tags associated with the item to be deleted.
1383 * This way of doing it would be inefficient, but seldom is any set.
1385 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1386 if (tag_get(node, tag, offset))
1387 radix_tree_tag_clear(root, index, tag);
1391 /* Now free the nodes we do not need anymore */
1393 node->slots[offset] = NULL;
1396 * Queue the node for deferred freeing after the
1397 * last reference to it disappears (set NULL, above).
1400 radix_tree_node_free(to_free);
1403 if (node == indirect_to_ptr(root->rnode))
1404 radix_tree_shrink(root);
1408 /* Node with zero slots in use so free it */
1411 index >>= RADIX_TREE_MAP_SHIFT;
1412 offset = index & RADIX_TREE_MAP_MASK;
1413 node = node->parent;
1416 root_tag_clear_all(root);
1420 radix_tree_node_free(to_free);
1425 EXPORT_SYMBOL(radix_tree_delete);
1428 * radix_tree_tagged - test whether any items in the tree are tagged
1429 * @root: radix tree root
1432 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1434 return root_tag_get(root, tag);
1436 EXPORT_SYMBOL(radix_tree_tagged);
1439 radix_tree_node_ctor(void *node)
1441 memset(node, 0, sizeof(struct radix_tree_node));
1444 static __init unsigned long __maxindex(unsigned int height)
1446 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1447 int shift = RADIX_TREE_INDEX_BITS - width;
1451 if (shift >= BITS_PER_LONG)
1453 return ~0UL >> shift;
1456 static __init void radix_tree_init_maxindex(void)
1460 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1461 height_to_maxindex[i] = __maxindex(i);
1464 static int radix_tree_callback(struct notifier_block *nfb,
1465 unsigned long action,
1468 int cpu = (long)hcpu;
1469 struct radix_tree_preload *rtp;
1471 /* Free per-cpu pool of perloaded nodes */
1472 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1473 rtp = &per_cpu(radix_tree_preloads, cpu);
1475 kmem_cache_free(radix_tree_node_cachep,
1476 rtp->nodes[rtp->nr-1]);
1477 rtp->nodes[rtp->nr-1] = NULL;
1484 void __init radix_tree_init(void)
1486 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1487 sizeof(struct radix_tree_node), 0,
1488 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1489 radix_tree_node_ctor);
1490 radix_tree_init_maxindex();
1491 hotcpu_notifier(radix_tree_callback, 0);