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 * The height_to_maxindex array needs to be one deeper than the maximum
40 * path as height 0 holds only 1 entry.
42 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
45 * Radix tree node cache.
47 static struct kmem_cache *radix_tree_node_cachep;
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
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.
60 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
63 * Per-cpu pool of preloaded nodes
65 struct radix_tree_preload {
67 struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE];
69 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
71 static inline void *ptr_to_indirect(void *ptr)
73 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
76 static inline void *indirect_to_ptr(void *ptr)
78 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
81 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
83 return root->gfp_mask & __GFP_BITS_MASK;
86 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
89 __set_bit(offset, node->tags[tag]);
92 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
95 __clear_bit(offset, node->tags[tag]);
98 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
101 return test_bit(offset, node->tags[tag]);
104 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
106 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
109 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
111 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
114 static inline void root_tag_clear_all(struct radix_tree_root *root)
116 root->gfp_mask &= __GFP_BITS_MASK;
119 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
121 return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
125 * Returns 1 if any slot in the node has this tag set.
126 * Otherwise returns 0.
128 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
131 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
132 if (node->tags[tag][idx])
139 * radix_tree_find_next_bit - find the next set bit in a memory region
141 * @addr: The address to base the search on
142 * @size: The bitmap size in bits
143 * @offset: The bitnumber to start searching at
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.
149 static __always_inline unsigned long
150 radix_tree_find_next_bit(const unsigned long *addr,
151 unsigned long size, unsigned long offset)
153 if (!__builtin_constant_p(size))
154 return find_next_bit(addr, size, offset);
159 addr += offset / BITS_PER_LONG;
160 tmp = *addr >> (offset % BITS_PER_LONG);
162 return __ffs(tmp) + offset;
163 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
164 while (offset < size) {
167 return __ffs(tmp) + offset;
168 offset += BITS_PER_LONG;
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.
178 static struct radix_tree_node *
179 radix_tree_node_alloc(struct radix_tree_root *root)
181 struct radix_tree_node *ret = NULL;
182 gfp_t gfp_mask = root_gfp_mask(root);
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.
189 if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) {
190 struct radix_tree_preload *rtp;
193 * Provided the caller has preloaded here, we will always
194 * succeed in getting a node here (and never reach
197 rtp = &__get_cpu_var(radix_tree_preloads);
199 ret = rtp->nodes[rtp->nr - 1];
200 rtp->nodes[rtp->nr - 1] = NULL;
205 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
207 BUG_ON(radix_tree_is_indirect_ptr(ret));
211 static void radix_tree_node_rcu_free(struct rcu_head *head)
213 struct radix_tree_node *node =
214 container_of(head, struct radix_tree_node, rcu_head);
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.
222 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
223 tag_clear(node, i, 0);
225 node->slots[0] = NULL;
228 kmem_cache_free(radix_tree_node_cachep, node);
232 radix_tree_node_free(struct radix_tree_node *node)
234 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
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.
243 * To make use of this facility, the radix tree must be initialised without
244 * __GFP_WAIT being passed to INIT_RADIX_TREE().
246 static int __radix_tree_preload(gfp_t gfp_mask)
248 struct radix_tree_preload *rtp;
249 struct radix_tree_node *node;
253 rtp = &__get_cpu_var(radix_tree_preloads);
254 while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
256 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
260 rtp = &__get_cpu_var(radix_tree_preloads);
261 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
262 rtp->nodes[rtp->nr++] = node;
264 kmem_cache_free(radix_tree_node_cachep, node);
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.
277 * To make use of this facility, the radix tree must be initialised without
278 * __GFP_WAIT being passed to INIT_RADIX_TREE().
280 int radix_tree_preload(gfp_t gfp_mask)
282 /* Warn on non-sensical use... */
283 WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT));
284 return __radix_tree_preload(gfp_mask);
286 EXPORT_SYMBOL(radix_tree_preload);
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.
293 int radix_tree_maybe_preload(gfp_t gfp_mask)
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 */
301 EXPORT_SYMBOL(radix_tree_maybe_preload);
304 * Return the maximum key which can be store into a
305 * radix tree with height HEIGHT.
307 static inline unsigned long radix_tree_maxindex(unsigned int height)
309 return height_to_maxindex[height];
313 * Extend a radix tree so it can store key @index.
315 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
317 struct radix_tree_node *node;
318 struct radix_tree_node *slot;
322 /* Figure out what the height should be. */
323 height = root->height + 1;
324 while (index > radix_tree_maxindex(height))
327 if (root->rnode == NULL) {
328 root->height = height;
333 unsigned int newheight;
334 if (!(node = radix_tree_node_alloc(root)))
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);
343 /* Increase the height. */
344 newheight = root->height+1;
345 node->height = newheight;
350 slot = indirect_to_ptr(slot);
353 node->slots[0] = slot;
354 node = ptr_to_indirect(node);
355 rcu_assign_pointer(root->rnode, node);
356 root->height = newheight;
357 } while (height > root->height);
363 * __radix_tree_create - create a slot in a radix tree
364 * @root: radix tree root
366 * @nodep: returns node
367 * @slotp: returns slot
369 * Create, if necessary, and return the node and slot for an item
370 * at position @index in the radix tree @root.
372 * Until there is more than one item in the tree, no nodes are
373 * allocated and @root->rnode is used as a direct slot instead of
374 * pointing to a node, in which case *@nodep will be NULL.
376 * Returns -ENOMEM, or 0 for success.
378 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
379 struct radix_tree_node **nodep, void ***slotp)
381 struct radix_tree_node *node = NULL, *slot;
382 unsigned int height, shift, offset;
385 /* Make sure the tree is high enough. */
386 if (index > radix_tree_maxindex(root->height)) {
387 error = radix_tree_extend(root, index);
392 slot = indirect_to_ptr(root->rnode);
394 height = root->height;
395 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
397 offset = 0; /* uninitialised var warning */
400 /* Have to add a child node. */
401 if (!(slot = radix_tree_node_alloc(root)))
403 slot->height = height;
406 rcu_assign_pointer(node->slots[offset], slot);
409 rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
412 /* Go a level down */
413 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
415 slot = node->slots[offset];
416 shift -= RADIX_TREE_MAP_SHIFT;
423 *slotp = node ? node->slots + offset : (void **)&root->rnode;
428 * radix_tree_insert - insert into a radix tree
429 * @root: radix tree root
431 * @item: item to insert
433 * Insert an item into the radix tree at position @index.
435 int radix_tree_insert(struct radix_tree_root *root,
436 unsigned long index, void *item)
438 struct radix_tree_node *node;
442 BUG_ON(radix_tree_is_indirect_ptr(item));
444 error = __radix_tree_create(root, index, &node, &slot);
449 rcu_assign_pointer(*slot, item);
453 BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK));
454 BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK));
456 BUG_ON(root_tag_get(root, 0));
457 BUG_ON(root_tag_get(root, 1));
462 EXPORT_SYMBOL(radix_tree_insert);
465 * __radix_tree_lookup - lookup an item in a radix tree
466 * @root: radix tree root
468 * @nodep: returns node
469 * @slotp: returns slot
471 * Lookup and return the item at position @index in the radix
474 * Until there is more than one item in the tree, no nodes are
475 * allocated and @root->rnode is used as a direct slot instead of
476 * pointing to a node, in which case *@nodep will be NULL.
478 void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
479 struct radix_tree_node **nodep, void ***slotp)
481 struct radix_tree_node *node, *parent;
482 unsigned int height, shift;
485 node = rcu_dereference_raw(root->rnode);
489 if (!radix_tree_is_indirect_ptr(node)) {
496 *slotp = (void **)&root->rnode;
499 node = indirect_to_ptr(node);
501 height = node->height;
502 if (index > radix_tree_maxindex(height))
505 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
509 slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK);
510 node = rcu_dereference_raw(*slot);
514 shift -= RADIX_TREE_MAP_SHIFT;
516 } while (height > 0);
526 * radix_tree_lookup_slot - lookup a slot in a radix tree
527 * @root: radix tree root
530 * Returns: the slot corresponding to the position @index in the
531 * radix tree @root. This is useful for update-if-exists operations.
533 * This function can be called under rcu_read_lock iff the slot is not
534 * modified by radix_tree_replace_slot, otherwise it must be called
535 * exclusive from other writers. Any dereference of the slot must be done
536 * using radix_tree_deref_slot.
538 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
542 if (!__radix_tree_lookup(root, index, NULL, &slot))
546 EXPORT_SYMBOL(radix_tree_lookup_slot);
549 * radix_tree_lookup - perform lookup operation on a radix tree
550 * @root: radix tree root
553 * Lookup the item at the position @index in the radix tree @root.
555 * This function can be called under rcu_read_lock, however the caller
556 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
557 * them safely). No RCU barriers are required to access or modify the
558 * returned item, however.
560 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
562 return __radix_tree_lookup(root, index, NULL, NULL);
564 EXPORT_SYMBOL(radix_tree_lookup);
567 * radix_tree_tag_set - set a tag on a radix tree node
568 * @root: radix tree root
572 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
573 * corresponding to @index in the radix tree. From
574 * the root all the way down to the leaf node.
576 * Returns the address of the tagged item. Setting a tag on a not-present
579 void *radix_tree_tag_set(struct radix_tree_root *root,
580 unsigned long index, unsigned int tag)
582 unsigned int height, shift;
583 struct radix_tree_node *slot;
585 height = root->height;
586 BUG_ON(index > radix_tree_maxindex(height));
588 slot = indirect_to_ptr(root->rnode);
589 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
594 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
595 if (!tag_get(slot, tag, offset))
596 tag_set(slot, tag, offset);
597 slot = slot->slots[offset];
598 BUG_ON(slot == NULL);
599 shift -= RADIX_TREE_MAP_SHIFT;
603 /* set the root's tag bit */
604 if (slot && !root_tag_get(root, tag))
605 root_tag_set(root, tag);
609 EXPORT_SYMBOL(radix_tree_tag_set);
612 * radix_tree_tag_clear - clear a tag on a radix tree node
613 * @root: radix tree root
617 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
618 * corresponding to @index in the radix tree. If
619 * this causes the leaf node to have no tags set then clear the tag in the
620 * next-to-leaf node, etc.
622 * Returns the address of the tagged item on success, else NULL. ie:
623 * has the same return value and semantics as radix_tree_lookup().
625 void *radix_tree_tag_clear(struct radix_tree_root *root,
626 unsigned long index, unsigned int tag)
628 struct radix_tree_node *node = NULL;
629 struct radix_tree_node *slot = NULL;
630 unsigned int height, shift;
631 int uninitialized_var(offset);
633 height = root->height;
634 if (index > radix_tree_maxindex(height))
637 shift = height * RADIX_TREE_MAP_SHIFT;
638 slot = indirect_to_ptr(root->rnode);
644 shift -= RADIX_TREE_MAP_SHIFT;
645 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
647 slot = slot->slots[offset];
654 if (!tag_get(node, tag, offset))
656 tag_clear(node, tag, offset);
657 if (any_tag_set(node, tag))
660 index >>= RADIX_TREE_MAP_SHIFT;
661 offset = index & RADIX_TREE_MAP_MASK;
665 /* clear the root's tag bit */
666 if (root_tag_get(root, tag))
667 root_tag_clear(root, tag);
672 EXPORT_SYMBOL(radix_tree_tag_clear);
675 * radix_tree_tag_get - get a tag on a radix tree node
676 * @root: radix tree root
678 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
682 * 0: tag not present or not set
685 * Note that the return value of this function may not be relied on, even if
686 * the RCU lock is held, unless tag modification and node deletion are excluded
689 int radix_tree_tag_get(struct radix_tree_root *root,
690 unsigned long index, unsigned int tag)
692 unsigned int height, shift;
693 struct radix_tree_node *node;
695 /* check the root's tag bit */
696 if (!root_tag_get(root, tag))
699 node = rcu_dereference_raw(root->rnode);
703 if (!radix_tree_is_indirect_ptr(node))
705 node = indirect_to_ptr(node);
707 height = node->height;
708 if (index > radix_tree_maxindex(height))
711 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
719 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
720 if (!tag_get(node, tag, offset))
724 node = rcu_dereference_raw(node->slots[offset]);
725 shift -= RADIX_TREE_MAP_SHIFT;
729 EXPORT_SYMBOL(radix_tree_tag_get);
732 * radix_tree_next_chunk - find next chunk of slots for iteration
734 * @root: radix tree root
735 * @iter: iterator state
736 * @flags: RADIX_TREE_ITER_* flags and tag index
737 * Returns: pointer to chunk first slot, or NULL if iteration is over
739 void **radix_tree_next_chunk(struct radix_tree_root *root,
740 struct radix_tree_iter *iter, unsigned flags)
742 unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
743 struct radix_tree_node *rnode, *node;
744 unsigned long index, offset;
746 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
750 * Catch next_index overflow after ~0UL. iter->index never overflows
751 * during iterating; it can be zero only at the beginning.
752 * And we cannot overflow iter->next_index in a single step,
753 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
755 * This condition also used by radix_tree_next_slot() to stop
756 * contiguous iterating, and forbid swithing to the next chunk.
758 index = iter->next_index;
759 if (!index && iter->index)
762 rnode = rcu_dereference_raw(root->rnode);
763 if (radix_tree_is_indirect_ptr(rnode)) {
764 rnode = indirect_to_ptr(rnode);
765 } else if (rnode && !index) {
766 /* Single-slot tree */
768 iter->next_index = 1;
770 return (void **)&root->rnode;
775 shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
776 offset = index >> shift;
778 /* Index outside of the tree */
779 if (offset >= RADIX_TREE_MAP_SIZE)
784 if ((flags & RADIX_TREE_ITER_TAGGED) ?
785 !test_bit(offset, node->tags[tag]) :
786 !node->slots[offset]) {
788 if (flags & RADIX_TREE_ITER_CONTIG)
791 if (flags & RADIX_TREE_ITER_TAGGED)
792 offset = radix_tree_find_next_bit(
797 while (++offset < RADIX_TREE_MAP_SIZE) {
798 if (node->slots[offset])
801 index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
802 index += offset << shift;
803 /* Overflow after ~0UL */
806 if (offset == RADIX_TREE_MAP_SIZE)
810 /* This is leaf-node */
814 node = rcu_dereference_raw(node->slots[offset]);
817 shift -= RADIX_TREE_MAP_SHIFT;
818 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
821 /* Update the iterator state */
823 iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
825 /* Construct iter->tags bit-mask from node->tags[tag] array */
826 if (flags & RADIX_TREE_ITER_TAGGED) {
827 unsigned tag_long, tag_bit;
829 tag_long = offset / BITS_PER_LONG;
830 tag_bit = offset % BITS_PER_LONG;
831 iter->tags = node->tags[tag][tag_long] >> tag_bit;
832 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
833 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
834 /* Pick tags from next element */
836 iter->tags |= node->tags[tag][tag_long + 1] <<
837 (BITS_PER_LONG - tag_bit);
838 /* Clip chunk size, here only BITS_PER_LONG tags */
839 iter->next_index = index + BITS_PER_LONG;
843 return node->slots + offset;
845 EXPORT_SYMBOL(radix_tree_next_chunk);
848 * radix_tree_range_tag_if_tagged - for each item in given range set given
849 * tag if item has another tag set
850 * @root: radix tree root
851 * @first_indexp: pointer to a starting index of a range to scan
852 * @last_index: last index of a range to scan
853 * @nr_to_tag: maximum number items to tag
854 * @iftag: tag index to test
855 * @settag: tag index to set if tested tag is set
857 * This function scans range of radix tree from first_index to last_index
858 * (inclusive). For each item in the range if iftag is set, the function sets
859 * also settag. The function stops either after tagging nr_to_tag items or
860 * after reaching last_index.
862 * The tags must be set from the leaf level only and propagated back up the
863 * path to the root. We must do this so that we resolve the full path before
864 * setting any tags on intermediate nodes. If we set tags as we descend, then
865 * we can get to the leaf node and find that the index that has the iftag
866 * set is outside the range we are scanning. This reults in dangling tags and
867 * can lead to problems with later tag operations (e.g. livelocks on lookups).
869 * The function returns number of leaves where the tag was set and sets
870 * *first_indexp to the first unscanned index.
871 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
872 * be prepared to handle that.
874 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
875 unsigned long *first_indexp, unsigned long last_index,
876 unsigned long nr_to_tag,
877 unsigned int iftag, unsigned int settag)
879 unsigned int height = root->height;
880 struct radix_tree_node *node = NULL;
881 struct radix_tree_node *slot;
883 unsigned long tagged = 0;
884 unsigned long index = *first_indexp;
886 last_index = min(last_index, radix_tree_maxindex(height));
887 if (index > last_index)
891 if (!root_tag_get(root, iftag)) {
892 *first_indexp = last_index + 1;
896 *first_indexp = last_index + 1;
897 root_tag_set(root, settag);
901 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
902 slot = indirect_to_ptr(root->rnode);
905 unsigned long upindex;
908 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
909 if (!slot->slots[offset])
911 if (!tag_get(slot, iftag, offset))
914 /* Go down one level */
915 shift -= RADIX_TREE_MAP_SHIFT;
917 slot = slot->slots[offset];
923 tag_set(slot, settag, offset);
925 /* walk back up the path tagging interior nodes */
928 upindex >>= RADIX_TREE_MAP_SHIFT;
929 offset = upindex & RADIX_TREE_MAP_MASK;
931 /* stop if we find a node with the tag already set */
932 if (tag_get(node, settag, offset))
934 tag_set(node, settag, offset);
939 * Small optimization: now clear that node pointer.
940 * Since all of this slot's ancestors now have the tag set
941 * from setting it above, we have no further need to walk
942 * back up the tree setting tags, until we update slot to
943 * point to another radix_tree_node.
948 /* Go to next item at level determined by 'shift' */
949 index = ((index >> shift) + 1) << shift;
950 /* Overflow can happen when last_index is ~0UL... */
951 if (index > last_index || !index)
953 if (tagged >= nr_to_tag)
955 while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
957 * We've fully scanned this node. Go up. Because
958 * last_index is guaranteed to be in the tree, what
959 * we do below cannot wander astray.
962 shift += RADIX_TREE_MAP_SHIFT;
966 * We need not to tag the root tag if there is no tag which is set with
967 * settag within the range from *first_indexp to last_index.
970 root_tag_set(root, settag);
971 *first_indexp = index;
975 EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
978 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
979 * @root: radix tree root
980 * @results: where the results of the lookup are placed
981 * @first_index: start the lookup from this key
982 * @max_items: place up to this many items at *results
984 * Performs an index-ascending scan of the tree for present items. Places
985 * them at *@results and returns the number of items which were placed at
988 * The implementation is naive.
990 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
991 * rcu_read_lock. In this case, rather than the returned results being
992 * an atomic snapshot of the tree at a single point in time, the semantics
993 * of an RCU protected gang lookup are as though multiple radix_tree_lookups
994 * have been issued in individual locks, and results stored in 'results'.
997 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
998 unsigned long first_index, unsigned int max_items)
1000 struct radix_tree_iter iter;
1002 unsigned int ret = 0;
1004 if (unlikely(!max_items))
1007 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1008 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1011 if (++ret == max_items)
1017 EXPORT_SYMBOL(radix_tree_gang_lookup);
1020 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1021 * @root: radix tree root
1022 * @results: where the results of the lookup are placed
1023 * @indices: where their indices should be placed (but usually NULL)
1024 * @first_index: start the lookup from this key
1025 * @max_items: place up to this many items at *results
1027 * Performs an index-ascending scan of the tree for present items. Places
1028 * their slots at *@results and returns the number of items which were
1029 * placed at *@results.
1031 * The implementation is naive.
1033 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1034 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1035 * protection, radix_tree_deref_slot may fail requiring a retry.
1038 radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1039 void ***results, unsigned long *indices,
1040 unsigned long first_index, unsigned int max_items)
1042 struct radix_tree_iter iter;
1044 unsigned int ret = 0;
1046 if (unlikely(!max_items))
1049 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1050 results[ret] = slot;
1052 indices[ret] = iter.index;
1053 if (++ret == max_items)
1059 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1062 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1064 * @root: radix tree root
1065 * @results: where the results of the lookup are placed
1066 * @first_index: start the lookup from this key
1067 * @max_items: place up to this many items at *results
1068 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1070 * Performs an index-ascending scan of the tree for present items which
1071 * have the tag indexed by @tag set. Places the items at *@results and
1072 * returns the number of items which were placed at *@results.
1075 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1076 unsigned long first_index, unsigned int max_items,
1079 struct radix_tree_iter iter;
1081 unsigned int ret = 0;
1083 if (unlikely(!max_items))
1086 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1087 results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
1090 if (++ret == max_items)
1096 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1099 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1100 * radix tree based on a tag
1101 * @root: radix tree root
1102 * @results: where the results of the lookup are placed
1103 * @first_index: start the lookup from this key
1104 * @max_items: place up to this many items at *results
1105 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1107 * Performs an index-ascending scan of the tree for present items which
1108 * have the tag indexed by @tag set. Places the slots at *@results and
1109 * returns the number of slots which were placed at *@results.
1112 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1113 unsigned long first_index, unsigned int max_items,
1116 struct radix_tree_iter iter;
1118 unsigned int ret = 0;
1120 if (unlikely(!max_items))
1123 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1124 results[ret] = slot;
1125 if (++ret == max_items)
1131 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1133 #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1134 #include <linux/sched.h> /* for cond_resched() */
1137 * This linear search is at present only useful to shmem_unuse_inode().
1139 static unsigned long __locate(struct radix_tree_node *slot, void *item,
1140 unsigned long index, unsigned long *found_index)
1142 unsigned int shift, height;
1145 height = slot->height;
1146 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1148 for ( ; height > 1; height--) {
1149 i = (index >> shift) & RADIX_TREE_MAP_MASK;
1151 if (slot->slots[i] != NULL)
1153 index &= ~((1UL << shift) - 1);
1154 index += 1UL << shift;
1156 goto out; /* 32-bit wraparound */
1158 if (i == RADIX_TREE_MAP_SIZE)
1162 shift -= RADIX_TREE_MAP_SHIFT;
1163 slot = rcu_dereference_raw(slot->slots[i]);
1168 /* Bottom level: check items */
1169 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
1170 if (slot->slots[i] == item) {
1171 *found_index = index + i;
1176 index += RADIX_TREE_MAP_SIZE;
1182 * radix_tree_locate_item - search through radix tree for item
1183 * @root: radix tree root
1184 * @item: item to be found
1186 * Returns index where item was found, or -1 if not found.
1187 * Caller must hold no lock (since this time-consuming function needs
1188 * to be preemptible), and must check afterwards if item is still there.
1190 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1192 struct radix_tree_node *node;
1193 unsigned long max_index;
1194 unsigned long cur_index = 0;
1195 unsigned long found_index = -1;
1199 node = rcu_dereference_raw(root->rnode);
1200 if (!radix_tree_is_indirect_ptr(node)) {
1207 node = indirect_to_ptr(node);
1208 max_index = radix_tree_maxindex(node->height);
1209 if (cur_index > max_index) {
1214 cur_index = __locate(node, item, cur_index, &found_index);
1217 } while (cur_index != 0 && cur_index <= max_index);
1222 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1226 #endif /* CONFIG_SHMEM && CONFIG_SWAP */
1229 * radix_tree_shrink - shrink height of a radix tree to minimal
1230 * @root radix tree root
1232 static inline void radix_tree_shrink(struct radix_tree_root *root)
1234 /* try to shrink tree height */
1235 while (root->height > 0) {
1236 struct radix_tree_node *to_free = root->rnode;
1237 struct radix_tree_node *slot;
1239 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1240 to_free = indirect_to_ptr(to_free);
1243 * The candidate node has more than one child, or its child
1244 * is not at the leftmost slot, we cannot shrink.
1246 if (to_free->count != 1)
1248 if (!to_free->slots[0])
1252 * We don't need rcu_assign_pointer(), since we are simply
1253 * moving the node from one part of the tree to another: if it
1254 * was safe to dereference the old pointer to it
1255 * (to_free->slots[0]), it will be safe to dereference the new
1256 * one (root->rnode) as far as dependent read barriers go.
1258 slot = to_free->slots[0];
1259 if (root->height > 1) {
1260 slot->parent = NULL;
1261 slot = ptr_to_indirect(slot);
1267 * We have a dilemma here. The node's slot[0] must not be
1268 * NULLed in case there are concurrent lookups expecting to
1269 * find the item. However if this was a bottom-level node,
1270 * then it may be subject to the slot pointer being visible
1271 * to callers dereferencing it. If item corresponding to
1272 * slot[0] is subsequently deleted, these callers would expect
1273 * their slot to become empty sooner or later.
1275 * For example, lockless pagecache will look up a slot, deref
1276 * the page pointer, and if the page is 0 refcount it means it
1277 * was concurrently deleted from pagecache so try the deref
1278 * again. Fortunately there is already a requirement for logic
1279 * to retry the entire slot lookup -- the indirect pointer
1280 * problem (replacing direct root node with an indirect pointer
1281 * also results in a stale slot). So tag the slot as indirect
1282 * to force callers to retry.
1284 if (root->height == 0)
1285 *((unsigned long *)&to_free->slots[0]) |=
1286 RADIX_TREE_INDIRECT_PTR;
1288 radix_tree_node_free(to_free);
1293 * __radix_tree_delete_node - try to free node after clearing a slot
1294 * @root: radix tree root
1296 * @node: node containing @index
1298 * After clearing the slot at @index in @node from radix tree
1299 * rooted at @root, call this function to attempt freeing the
1300 * node and shrinking the tree.
1302 * Returns %true if @node was freed, %false otherwise.
1304 bool __radix_tree_delete_node(struct radix_tree_root *root, unsigned long index,
1305 struct radix_tree_node *node)
1307 bool deleted = false;
1310 struct radix_tree_node *parent;
1313 if (node == indirect_to_ptr(root->rnode)) {
1314 radix_tree_shrink(root);
1315 if (root->height == 0)
1321 parent = node->parent;
1323 index >>= RADIX_TREE_MAP_SHIFT;
1325 parent->slots[index & RADIX_TREE_MAP_MASK] = NULL;
1328 root_tag_clear_all(root);
1333 radix_tree_node_free(node);
1343 * radix_tree_delete_item - delete an item from a radix tree
1344 * @root: radix tree root
1346 * @item: expected item
1348 * Remove @item at @index from the radix tree rooted at @root.
1350 * Returns the address of the deleted item, or NULL if it was not present
1351 * or the entry at the given @index was not @item.
1353 void *radix_tree_delete_item(struct radix_tree_root *root,
1354 unsigned long index, void *item)
1356 struct radix_tree_node *node;
1357 unsigned int offset;
1362 entry = __radix_tree_lookup(root, index, &node, &slot);
1366 if (item && entry != item)
1370 root_tag_clear_all(root);
1375 offset = index & RADIX_TREE_MAP_MASK;
1378 * Clear all tags associated with the item to be deleted.
1379 * This way of doing it would be inefficient, but seldom is any set.
1381 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1382 if (tag_get(node, tag, offset))
1383 radix_tree_tag_clear(root, index, tag);
1386 node->slots[offset] = NULL;
1389 __radix_tree_delete_node(root, index, node);
1393 EXPORT_SYMBOL(radix_tree_delete_item);
1396 * radix_tree_delete - delete an item from a radix tree
1397 * @root: radix tree root
1400 * Remove the item at @index from the radix tree rooted at @root.
1402 * Returns the address of the deleted item, or NULL if it was not present.
1404 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1406 return radix_tree_delete_item(root, index, NULL);
1408 EXPORT_SYMBOL(radix_tree_delete);
1411 * radix_tree_tagged - test whether any items in the tree are tagged
1412 * @root: radix tree root
1415 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1417 return root_tag_get(root, tag);
1419 EXPORT_SYMBOL(radix_tree_tagged);
1422 radix_tree_node_ctor(void *node)
1424 memset(node, 0, sizeof(struct radix_tree_node));
1427 static __init unsigned long __maxindex(unsigned int height)
1429 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1430 int shift = RADIX_TREE_INDEX_BITS - width;
1434 if (shift >= BITS_PER_LONG)
1436 return ~0UL >> shift;
1439 static __init void radix_tree_init_maxindex(void)
1443 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1444 height_to_maxindex[i] = __maxindex(i);
1447 static int radix_tree_callback(struct notifier_block *nfb,
1448 unsigned long action,
1451 int cpu = (long)hcpu;
1452 struct radix_tree_preload *rtp;
1454 /* Free per-cpu pool of perloaded nodes */
1455 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1456 rtp = &per_cpu(radix_tree_preloads, cpu);
1458 kmem_cache_free(radix_tree_node_cachep,
1459 rtp->nodes[rtp->nr-1]);
1460 rtp->nodes[rtp->nr-1] = NULL;
1467 void __init radix_tree_init(void)
1469 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1470 sizeof(struct radix_tree_node), 0,
1471 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1472 radix_tree_node_ctor);
1473 radix_tree_init_maxindex();
1474 hotcpu_notifier(radix_tree_callback, 0);