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/kmemleak.h>
31 #include <linux/notifier.h>
32 #include <linux/cpu.h>
33 #include <linux/string.h>
34 #include <linux/bitops.h>
35 #include <linux/rcupdate.h>
36 #include <linux/preempt.h> /* in_interrupt() */
40 * The height_to_maxindex array needs to be one deeper than the maximum
41 * path as height 0 holds only 1 entry.
43 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
46 * Radix tree node cache.
48 static struct kmem_cache *radix_tree_node_cachep;
51 * The radix tree is variable-height, so an insert operation not only has
52 * to build the branch to its corresponding item, it also has to build the
53 * branch to existing items if the size has to be increased (by
56 * The worst case is a zero height tree with just a single item at index 0,
57 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
58 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
61 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
64 * Per-cpu pool of preloaded nodes
66 struct radix_tree_preload {
68 /* nodes->private_data points to next preallocated node */
69 struct radix_tree_node *nodes;
71 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
73 static inline void *ptr_to_indirect(void *ptr)
75 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
78 static inline void *indirect_to_ptr(void *ptr)
80 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
83 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
85 return root->gfp_mask & __GFP_BITS_MASK;
88 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
91 __set_bit(offset, node->tags[tag]);
94 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
97 __clear_bit(offset, node->tags[tag]);
100 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
103 return test_bit(offset, node->tags[tag]);
106 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
108 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
111 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
113 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
116 static inline void root_tag_clear_all(struct radix_tree_root *root)
118 root->gfp_mask &= __GFP_BITS_MASK;
121 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
123 return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
127 * Returns 1 if any slot in the node has this tag set.
128 * Otherwise returns 0.
130 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
133 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
134 if (node->tags[tag][idx])
141 * radix_tree_find_next_bit - find the next set bit in a memory region
143 * @addr: The address to base the search on
144 * @size: The bitmap size in bits
145 * @offset: The bitnumber to start searching at
147 * Unrollable variant of find_next_bit() for constant size arrays.
148 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
149 * Returns next bit offset, or size if nothing found.
151 static __always_inline unsigned long
152 radix_tree_find_next_bit(const unsigned long *addr,
153 unsigned long size, unsigned long offset)
155 if (!__builtin_constant_p(size))
156 return find_next_bit(addr, size, offset);
161 addr += offset / BITS_PER_LONG;
162 tmp = *addr >> (offset % BITS_PER_LONG);
164 return __ffs(tmp) + offset;
165 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
166 while (offset < size) {
169 return __ffs(tmp) + offset;
170 offset += BITS_PER_LONG;
177 * This assumes that the caller has performed appropriate preallocation, and
178 * that the caller has pinned this thread of control to the current CPU.
180 static struct radix_tree_node *
181 radix_tree_node_alloc(struct radix_tree_root *root)
183 struct radix_tree_node *ret = NULL;
184 gfp_t gfp_mask = root_gfp_mask(root);
187 * Preload code isn't irq safe and it doesn't make sence to use
188 * preloading in the interrupt anyway as all the allocations have to
189 * be atomic. So just do normal allocation when in interrupt.
191 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
192 struct radix_tree_preload *rtp;
195 * Provided the caller has preloaded here, we will always
196 * succeed in getting a node here (and never reach
199 rtp = &get_cpu_var(radix_tree_preloads);
202 rtp->nodes = ret->private_data;
203 ret->private_data = NULL;
206 put_cpu_var(radix_tree_preloads);
208 * Update the allocation stack trace as this is more useful
211 kmemleak_update_trace(ret);
214 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
216 BUG_ON(radix_tree_is_indirect_ptr(ret));
220 static void radix_tree_node_rcu_free(struct rcu_head *head)
222 struct radix_tree_node *node =
223 container_of(head, struct radix_tree_node, rcu_head);
227 * must only free zeroed nodes into the slab. radix_tree_shrink
228 * can leave us with a non-NULL entry in the first slot, so clear
229 * that here to make sure.
231 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
232 tag_clear(node, i, 0);
234 node->slots[0] = NULL;
237 kmem_cache_free(radix_tree_node_cachep, node);
241 radix_tree_node_free(struct radix_tree_node *node)
243 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
246 #ifndef CONFIG_PREEMPT_RT_FULL
248 * Load up this CPU's radix_tree_node buffer with sufficient objects to
249 * ensure that the addition of a single element in the tree cannot fail. On
250 * success, return zero, with preemption disabled. On error, return -ENOMEM
251 * with preemption not disabled.
253 * To make use of this facility, the radix tree must be initialised without
254 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
256 static int __radix_tree_preload(gfp_t gfp_mask)
258 struct radix_tree_preload *rtp;
259 struct radix_tree_node *node;
263 rtp = this_cpu_ptr(&radix_tree_preloads);
264 while (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
266 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
270 rtp = this_cpu_ptr(&radix_tree_preloads);
271 if (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
272 node->private_data = rtp->nodes;
276 kmem_cache_free(radix_tree_node_cachep, node);
285 * Load up this CPU's radix_tree_node buffer with sufficient objects to
286 * ensure that the addition of a single element in the tree cannot fail. On
287 * success, return zero, with preemption disabled. On error, return -ENOMEM
288 * with preemption not disabled.
290 * To make use of this facility, the radix tree must be initialised without
291 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
293 int radix_tree_preload(gfp_t gfp_mask)
295 /* Warn on non-sensical use... */
296 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
297 return __radix_tree_preload(gfp_mask);
299 EXPORT_SYMBOL(radix_tree_preload);
302 * The same as above function, except we don't guarantee preloading happens.
303 * We do it, if we decide it helps. On success, return zero with preemption
304 * disabled. On error, return -ENOMEM with preemption not disabled.
306 int radix_tree_maybe_preload(gfp_t gfp_mask)
308 if (gfpflags_allow_blocking(gfp_mask))
309 return __radix_tree_preload(gfp_mask);
310 /* Preloading doesn't help anything with this gfp mask, skip it */
314 EXPORT_SYMBOL(radix_tree_maybe_preload);
318 * Return the maximum key which can be store into a
319 * radix tree with height HEIGHT.
321 static inline unsigned long radix_tree_maxindex(unsigned int height)
323 return height_to_maxindex[height];
327 * Extend a radix tree so it can store key @index.
329 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
331 struct radix_tree_node *node;
332 struct radix_tree_node *slot;
336 /* Figure out what the height should be. */
337 height = root->height + 1;
338 while (index > radix_tree_maxindex(height))
341 if (root->rnode == NULL) {
342 root->height = height;
347 unsigned int newheight;
348 if (!(node = radix_tree_node_alloc(root)))
351 /* Propagate the aggregated tag info into the new root */
352 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
353 if (root_tag_get(root, tag))
354 tag_set(node, tag, 0);
357 /* Increase the height. */
358 newheight = root->height+1;
359 BUG_ON(newheight & ~RADIX_TREE_HEIGHT_MASK);
360 node->path = newheight;
365 slot = indirect_to_ptr(slot);
368 node->slots[0] = slot;
369 node = ptr_to_indirect(node);
370 rcu_assign_pointer(root->rnode, node);
371 root->height = newheight;
372 } while (height > root->height);
378 * __radix_tree_create - create a slot in a radix tree
379 * @root: radix tree root
381 * @nodep: returns node
382 * @slotp: returns slot
384 * Create, if necessary, and return the node and slot for an item
385 * at position @index in the radix tree @root.
387 * Until there is more than one item in the tree, no nodes are
388 * allocated and @root->rnode is used as a direct slot instead of
389 * pointing to a node, in which case *@nodep will be NULL.
391 * Returns -ENOMEM, or 0 for success.
393 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
394 struct radix_tree_node **nodep, void ***slotp)
396 struct radix_tree_node *node = NULL, *slot;
397 unsigned int height, shift, offset;
400 /* Make sure the tree is high enough. */
401 if (index > radix_tree_maxindex(root->height)) {
402 error = radix_tree_extend(root, index);
407 slot = indirect_to_ptr(root->rnode);
409 height = root->height;
410 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
412 offset = 0; /* uninitialised var warning */
415 /* Have to add a child node. */
416 if (!(slot = radix_tree_node_alloc(root)))
421 rcu_assign_pointer(node->slots[offset], slot);
423 slot->path |= offset << RADIX_TREE_HEIGHT_SHIFT;
425 rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
428 /* Go a level down */
429 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
431 slot = node->slots[offset];
432 shift -= RADIX_TREE_MAP_SHIFT;
439 *slotp = node ? node->slots + offset : (void **)&root->rnode;
444 * radix_tree_insert - insert into a radix tree
445 * @root: radix tree root
447 * @item: item to insert
449 * Insert an item into the radix tree at position @index.
451 int radix_tree_insert(struct radix_tree_root *root,
452 unsigned long index, void *item)
454 struct radix_tree_node *node;
458 BUG_ON(radix_tree_is_indirect_ptr(item));
460 error = __radix_tree_create(root, index, &node, &slot);
465 rcu_assign_pointer(*slot, item);
469 BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK));
470 BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK));
472 BUG_ON(root_tag_get(root, 0));
473 BUG_ON(root_tag_get(root, 1));
478 EXPORT_SYMBOL(radix_tree_insert);
481 * __radix_tree_lookup - lookup an item in a radix tree
482 * @root: radix tree root
484 * @nodep: returns node
485 * @slotp: returns slot
487 * Lookup and return the item at position @index in the radix
490 * Until there is more than one item in the tree, no nodes are
491 * allocated and @root->rnode is used as a direct slot instead of
492 * pointing to a node, in which case *@nodep will be NULL.
494 void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
495 struct radix_tree_node **nodep, void ***slotp)
497 struct radix_tree_node *node, *parent;
498 unsigned int height, shift;
501 node = rcu_dereference_raw(root->rnode);
505 if (!radix_tree_is_indirect_ptr(node)) {
512 *slotp = (void **)&root->rnode;
515 node = indirect_to_ptr(node);
517 height = node->path & RADIX_TREE_HEIGHT_MASK;
518 if (index > radix_tree_maxindex(height))
521 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
525 slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK);
526 node = rcu_dereference_raw(*slot);
530 shift -= RADIX_TREE_MAP_SHIFT;
532 } while (height > 0);
542 * radix_tree_lookup_slot - lookup a slot in a radix tree
543 * @root: radix tree root
546 * Returns: the slot corresponding to the position @index in the
547 * radix tree @root. This is useful for update-if-exists operations.
549 * This function can be called under rcu_read_lock iff the slot is not
550 * modified by radix_tree_replace_slot, otherwise it must be called
551 * exclusive from other writers. Any dereference of the slot must be done
552 * using radix_tree_deref_slot.
554 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
558 if (!__radix_tree_lookup(root, index, NULL, &slot))
562 EXPORT_SYMBOL(radix_tree_lookup_slot);
565 * radix_tree_lookup - perform lookup operation on a radix tree
566 * @root: radix tree root
569 * Lookup the item at the position @index in the radix tree @root.
571 * This function can be called under rcu_read_lock, however the caller
572 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
573 * them safely). No RCU barriers are required to access or modify the
574 * returned item, however.
576 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
578 return __radix_tree_lookup(root, index, NULL, NULL);
580 EXPORT_SYMBOL(radix_tree_lookup);
583 * radix_tree_tag_set - set a tag on a radix tree node
584 * @root: radix tree root
588 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
589 * corresponding to @index in the radix tree. From
590 * the root all the way down to the leaf node.
592 * Returns the address of the tagged item. Setting a tag on a not-present
595 void *radix_tree_tag_set(struct radix_tree_root *root,
596 unsigned long index, unsigned int tag)
598 unsigned int height, shift;
599 struct radix_tree_node *slot;
601 height = root->height;
602 BUG_ON(index > radix_tree_maxindex(height));
604 slot = indirect_to_ptr(root->rnode);
605 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
610 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
611 if (!tag_get(slot, tag, offset))
612 tag_set(slot, tag, offset);
613 slot = slot->slots[offset];
614 BUG_ON(slot == NULL);
615 shift -= RADIX_TREE_MAP_SHIFT;
619 /* set the root's tag bit */
620 if (slot && !root_tag_get(root, tag))
621 root_tag_set(root, tag);
625 EXPORT_SYMBOL(radix_tree_tag_set);
628 * radix_tree_tag_clear - clear a tag on a radix tree node
629 * @root: radix tree root
633 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
634 * corresponding to @index in the radix tree. If
635 * this causes the leaf node to have no tags set then clear the tag in the
636 * next-to-leaf node, etc.
638 * Returns the address of the tagged item on success, else NULL. ie:
639 * has the same return value and semantics as radix_tree_lookup().
641 void *radix_tree_tag_clear(struct radix_tree_root *root,
642 unsigned long index, unsigned int tag)
644 struct radix_tree_node *node = NULL;
645 struct radix_tree_node *slot = NULL;
646 unsigned int height, shift;
647 int uninitialized_var(offset);
649 height = root->height;
650 if (index > radix_tree_maxindex(height))
653 shift = height * RADIX_TREE_MAP_SHIFT;
654 slot = indirect_to_ptr(root->rnode);
660 shift -= RADIX_TREE_MAP_SHIFT;
661 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
663 slot = slot->slots[offset];
670 if (!tag_get(node, tag, offset))
672 tag_clear(node, tag, offset);
673 if (any_tag_set(node, tag))
676 index >>= RADIX_TREE_MAP_SHIFT;
677 offset = index & RADIX_TREE_MAP_MASK;
681 /* clear the root's tag bit */
682 if (root_tag_get(root, tag))
683 root_tag_clear(root, tag);
688 EXPORT_SYMBOL(radix_tree_tag_clear);
691 * radix_tree_tag_get - get a tag on a radix tree node
692 * @root: radix tree root
694 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
698 * 0: tag not present or not set
701 * Note that the return value of this function may not be relied on, even if
702 * the RCU lock is held, unless tag modification and node deletion are excluded
705 int radix_tree_tag_get(struct radix_tree_root *root,
706 unsigned long index, unsigned int tag)
708 unsigned int height, shift;
709 struct radix_tree_node *node;
711 /* check the root's tag bit */
712 if (!root_tag_get(root, tag))
715 node = rcu_dereference_raw(root->rnode);
719 if (!radix_tree_is_indirect_ptr(node))
721 node = indirect_to_ptr(node);
723 height = node->path & RADIX_TREE_HEIGHT_MASK;
724 if (index > radix_tree_maxindex(height))
727 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
735 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
736 if (!tag_get(node, tag, offset))
740 node = rcu_dereference_raw(node->slots[offset]);
741 shift -= RADIX_TREE_MAP_SHIFT;
745 EXPORT_SYMBOL(radix_tree_tag_get);
748 * radix_tree_next_chunk - find next chunk of slots for iteration
750 * @root: radix tree root
751 * @iter: iterator state
752 * @flags: RADIX_TREE_ITER_* flags and tag index
753 * Returns: pointer to chunk first slot, or NULL if iteration is over
755 void **radix_tree_next_chunk(struct radix_tree_root *root,
756 struct radix_tree_iter *iter, unsigned flags)
758 unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
759 struct radix_tree_node *rnode, *node;
760 unsigned long index, offset, height;
762 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
766 * Catch next_index overflow after ~0UL. iter->index never overflows
767 * during iterating; it can be zero only at the beginning.
768 * And we cannot overflow iter->next_index in a single step,
769 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
771 * This condition also used by radix_tree_next_slot() to stop
772 * contiguous iterating, and forbid swithing to the next chunk.
774 index = iter->next_index;
775 if (!index && iter->index)
778 rnode = rcu_dereference_raw(root->rnode);
779 if (radix_tree_is_indirect_ptr(rnode)) {
780 rnode = indirect_to_ptr(rnode);
781 } else if (rnode && !index) {
782 /* Single-slot tree */
784 iter->next_index = 1;
786 return (void **)&root->rnode;
791 height = rnode->path & RADIX_TREE_HEIGHT_MASK;
792 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
793 offset = index >> shift;
795 /* Index outside of the tree */
796 if (offset >= RADIX_TREE_MAP_SIZE)
801 if ((flags & RADIX_TREE_ITER_TAGGED) ?
802 !test_bit(offset, node->tags[tag]) :
803 !node->slots[offset]) {
805 if (flags & RADIX_TREE_ITER_CONTIG)
808 if (flags & RADIX_TREE_ITER_TAGGED)
809 offset = radix_tree_find_next_bit(
814 while (++offset < RADIX_TREE_MAP_SIZE) {
815 if (node->slots[offset])
818 index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
819 index += offset << shift;
820 /* Overflow after ~0UL */
823 if (offset == RADIX_TREE_MAP_SIZE)
827 /* This is leaf-node */
831 node = rcu_dereference_raw(node->slots[offset]);
834 shift -= RADIX_TREE_MAP_SHIFT;
835 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
838 /* Update the iterator state */
840 iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
842 /* Construct iter->tags bit-mask from node->tags[tag] array */
843 if (flags & RADIX_TREE_ITER_TAGGED) {
844 unsigned tag_long, tag_bit;
846 tag_long = offset / BITS_PER_LONG;
847 tag_bit = offset % BITS_PER_LONG;
848 iter->tags = node->tags[tag][tag_long] >> tag_bit;
849 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
850 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
851 /* Pick tags from next element */
853 iter->tags |= node->tags[tag][tag_long + 1] <<
854 (BITS_PER_LONG - tag_bit);
855 /* Clip chunk size, here only BITS_PER_LONG tags */
856 iter->next_index = index + BITS_PER_LONG;
860 return node->slots + offset;
862 EXPORT_SYMBOL(radix_tree_next_chunk);
865 * radix_tree_range_tag_if_tagged - for each item in given range set given
866 * tag if item has another tag set
867 * @root: radix tree root
868 * @first_indexp: pointer to a starting index of a range to scan
869 * @last_index: last index of a range to scan
870 * @nr_to_tag: maximum number items to tag
871 * @iftag: tag index to test
872 * @settag: tag index to set if tested tag is set
874 * This function scans range of radix tree from first_index to last_index
875 * (inclusive). For each item in the range if iftag is set, the function sets
876 * also settag. The function stops either after tagging nr_to_tag items or
877 * after reaching last_index.
879 * The tags must be set from the leaf level only and propagated back up the
880 * path to the root. We must do this so that we resolve the full path before
881 * setting any tags on intermediate nodes. If we set tags as we descend, then
882 * we can get to the leaf node and find that the index that has the iftag
883 * set is outside the range we are scanning. This reults in dangling tags and
884 * can lead to problems with later tag operations (e.g. livelocks on lookups).
886 * The function returns number of leaves where the tag was set and sets
887 * *first_indexp to the first unscanned index.
888 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
889 * be prepared to handle that.
891 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
892 unsigned long *first_indexp, unsigned long last_index,
893 unsigned long nr_to_tag,
894 unsigned int iftag, unsigned int settag)
896 unsigned int height = root->height;
897 struct radix_tree_node *node = NULL;
898 struct radix_tree_node *slot;
900 unsigned long tagged = 0;
901 unsigned long index = *first_indexp;
903 last_index = min(last_index, radix_tree_maxindex(height));
904 if (index > last_index)
908 if (!root_tag_get(root, iftag)) {
909 *first_indexp = last_index + 1;
913 *first_indexp = last_index + 1;
914 root_tag_set(root, settag);
918 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
919 slot = indirect_to_ptr(root->rnode);
922 unsigned long upindex;
925 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
926 if (!slot->slots[offset])
928 if (!tag_get(slot, iftag, offset))
931 /* Go down one level */
932 shift -= RADIX_TREE_MAP_SHIFT;
934 slot = slot->slots[offset];
940 tag_set(slot, settag, offset);
942 /* walk back up the path tagging interior nodes */
945 upindex >>= RADIX_TREE_MAP_SHIFT;
946 offset = upindex & RADIX_TREE_MAP_MASK;
948 /* stop if we find a node with the tag already set */
949 if (tag_get(node, settag, offset))
951 tag_set(node, settag, offset);
956 * Small optimization: now clear that node pointer.
957 * Since all of this slot's ancestors now have the tag set
958 * from setting it above, we have no further need to walk
959 * back up the tree setting tags, until we update slot to
960 * point to another radix_tree_node.
965 /* Go to next item at level determined by 'shift' */
966 index = ((index >> shift) + 1) << shift;
967 /* Overflow can happen when last_index is ~0UL... */
968 if (index > last_index || !index)
970 if (tagged >= nr_to_tag)
972 while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
974 * We've fully scanned this node. Go up. Because
975 * last_index is guaranteed to be in the tree, what
976 * we do below cannot wander astray.
979 shift += RADIX_TREE_MAP_SHIFT;
983 * We need not to tag the root tag if there is no tag which is set with
984 * settag within the range from *first_indexp to last_index.
987 root_tag_set(root, settag);
988 *first_indexp = index;
992 EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
995 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
996 * @root: radix tree root
997 * @results: where the results of the lookup are placed
998 * @first_index: start the lookup from this key
999 * @max_items: place up to this many items at *results
1001 * Performs an index-ascending scan of the tree for present items. Places
1002 * them at *@results and returns the number of items which were placed at
1005 * The implementation is naive.
1007 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1008 * rcu_read_lock. In this case, rather than the returned results being
1009 * an atomic snapshot of the tree at a single point in time, the semantics
1010 * of an RCU protected gang lookup are as though multiple radix_tree_lookups
1011 * have been issued in individual locks, and results stored in 'results'.
1014 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
1015 unsigned long first_index, unsigned int max_items)
1017 struct radix_tree_iter iter;
1019 unsigned int ret = 0;
1021 if (unlikely(!max_items))
1024 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1025 results[ret] = rcu_dereference_raw(*slot);
1028 if (radix_tree_is_indirect_ptr(results[ret])) {
1029 slot = radix_tree_iter_retry(&iter);
1032 if (++ret == max_items)
1038 EXPORT_SYMBOL(radix_tree_gang_lookup);
1041 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1042 * @root: radix tree root
1043 * @results: where the results of the lookup are placed
1044 * @indices: where their indices should be placed (but usually NULL)
1045 * @first_index: start the lookup from this key
1046 * @max_items: place up to this many items at *results
1048 * Performs an index-ascending scan of the tree for present items. Places
1049 * their slots at *@results and returns the number of items which were
1050 * placed at *@results.
1052 * The implementation is naive.
1054 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1055 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1056 * protection, radix_tree_deref_slot may fail requiring a retry.
1059 radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1060 void ***results, unsigned long *indices,
1061 unsigned long first_index, unsigned int max_items)
1063 struct radix_tree_iter iter;
1065 unsigned int ret = 0;
1067 if (unlikely(!max_items))
1070 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1071 results[ret] = slot;
1073 indices[ret] = iter.index;
1074 if (++ret == max_items)
1080 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1083 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1085 * @root: radix tree root
1086 * @results: where the results of the lookup are placed
1087 * @first_index: start the lookup from this key
1088 * @max_items: place up to this many items at *results
1089 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1091 * Performs an index-ascending scan of the tree for present items which
1092 * have the tag indexed by @tag set. Places the items at *@results and
1093 * returns the number of items which were placed at *@results.
1096 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1097 unsigned long first_index, unsigned int max_items,
1100 struct radix_tree_iter iter;
1102 unsigned int ret = 0;
1104 if (unlikely(!max_items))
1107 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1108 results[ret] = rcu_dereference_raw(*slot);
1111 if (radix_tree_is_indirect_ptr(results[ret])) {
1112 slot = radix_tree_iter_retry(&iter);
1115 if (++ret == max_items)
1121 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1124 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1125 * radix tree based on a tag
1126 * @root: radix tree root
1127 * @results: where the results of the lookup are placed
1128 * @first_index: start the lookup from this key
1129 * @max_items: place up to this many items at *results
1130 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1132 * Performs an index-ascending scan of the tree for present items which
1133 * have the tag indexed by @tag set. Places the slots at *@results and
1134 * returns the number of slots which were placed at *@results.
1137 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1138 unsigned long first_index, unsigned int max_items,
1141 struct radix_tree_iter iter;
1143 unsigned int ret = 0;
1145 if (unlikely(!max_items))
1148 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1149 results[ret] = slot;
1150 if (++ret == max_items)
1156 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1158 #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1159 #include <linux/sched.h> /* for cond_resched() */
1162 * This linear search is at present only useful to shmem_unuse_inode().
1164 static unsigned long __locate(struct radix_tree_node *slot, void *item,
1165 unsigned long index, unsigned long *found_index)
1167 unsigned int shift, height;
1170 height = slot->path & RADIX_TREE_HEIGHT_MASK;
1171 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1173 for ( ; height > 1; height--) {
1174 i = (index >> shift) & RADIX_TREE_MAP_MASK;
1176 if (slot->slots[i] != NULL)
1178 index &= ~((1UL << shift) - 1);
1179 index += 1UL << shift;
1181 goto out; /* 32-bit wraparound */
1183 if (i == RADIX_TREE_MAP_SIZE)
1187 shift -= RADIX_TREE_MAP_SHIFT;
1188 slot = rcu_dereference_raw(slot->slots[i]);
1193 /* Bottom level: check items */
1194 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
1195 if (slot->slots[i] == item) {
1196 *found_index = index + i;
1201 index += RADIX_TREE_MAP_SIZE;
1207 * radix_tree_locate_item - search through radix tree for item
1208 * @root: radix tree root
1209 * @item: item to be found
1211 * Returns index where item was found, or -1 if not found.
1212 * Caller must hold no lock (since this time-consuming function needs
1213 * to be preemptible), and must check afterwards if item is still there.
1215 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1217 struct radix_tree_node *node;
1218 unsigned long max_index;
1219 unsigned long cur_index = 0;
1220 unsigned long found_index = -1;
1224 node = rcu_dereference_raw(root->rnode);
1225 if (!radix_tree_is_indirect_ptr(node)) {
1232 node = indirect_to_ptr(node);
1233 max_index = radix_tree_maxindex(node->path &
1234 RADIX_TREE_HEIGHT_MASK);
1235 if (cur_index > max_index) {
1240 cur_index = __locate(node, item, cur_index, &found_index);
1243 } while (cur_index != 0 && cur_index <= max_index);
1248 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1252 #endif /* CONFIG_SHMEM && CONFIG_SWAP */
1255 * radix_tree_shrink - shrink height of a radix tree to minimal
1256 * @root radix tree root
1258 static inline void radix_tree_shrink(struct radix_tree_root *root)
1260 /* try to shrink tree height */
1261 while (root->height > 0) {
1262 struct radix_tree_node *to_free = root->rnode;
1263 struct radix_tree_node *slot;
1265 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1266 to_free = indirect_to_ptr(to_free);
1269 * The candidate node has more than one child, or its child
1270 * is not at the leftmost slot, we cannot shrink.
1272 if (to_free->count != 1)
1274 if (!to_free->slots[0])
1278 * We don't need rcu_assign_pointer(), since we are simply
1279 * moving the node from one part of the tree to another: if it
1280 * was safe to dereference the old pointer to it
1281 * (to_free->slots[0]), it will be safe to dereference the new
1282 * one (root->rnode) as far as dependent read barriers go.
1284 slot = to_free->slots[0];
1285 if (root->height > 1) {
1286 slot->parent = NULL;
1287 slot = ptr_to_indirect(slot);
1293 * We have a dilemma here. The node's slot[0] must not be
1294 * NULLed in case there are concurrent lookups expecting to
1295 * find the item. However if this was a bottom-level node,
1296 * then it may be subject to the slot pointer being visible
1297 * to callers dereferencing it. If item corresponding to
1298 * slot[0] is subsequently deleted, these callers would expect
1299 * their slot to become empty sooner or later.
1301 * For example, lockless pagecache will look up a slot, deref
1302 * the page pointer, and if the page is 0 refcount it means it
1303 * was concurrently deleted from pagecache so try the deref
1304 * again. Fortunately there is already a requirement for logic
1305 * to retry the entire slot lookup -- the indirect pointer
1306 * problem (replacing direct root node with an indirect pointer
1307 * also results in a stale slot). So tag the slot as indirect
1308 * to force callers to retry.
1310 if (root->height == 0)
1311 *((unsigned long *)&to_free->slots[0]) |=
1312 RADIX_TREE_INDIRECT_PTR;
1314 radix_tree_node_free(to_free);
1319 * __radix_tree_delete_node - try to free node after clearing a slot
1320 * @root: radix tree root
1321 * @node: node containing @index
1323 * After clearing the slot at @index in @node from radix tree
1324 * rooted at @root, call this function to attempt freeing the
1325 * node and shrinking the tree.
1327 * Returns %true if @node was freed, %false otherwise.
1329 bool __radix_tree_delete_node(struct radix_tree_root *root,
1330 struct radix_tree_node *node)
1332 bool deleted = false;
1335 struct radix_tree_node *parent;
1338 if (node == indirect_to_ptr(root->rnode)) {
1339 radix_tree_shrink(root);
1340 if (root->height == 0)
1346 parent = node->parent;
1348 unsigned int offset;
1350 offset = node->path >> RADIX_TREE_HEIGHT_SHIFT;
1351 parent->slots[offset] = NULL;
1354 root_tag_clear_all(root);
1359 radix_tree_node_free(node);
1369 * radix_tree_delete_item - delete an item from a radix tree
1370 * @root: radix tree root
1372 * @item: expected item
1374 * Remove @item at @index from the radix tree rooted at @root.
1376 * Returns the address of the deleted item, or NULL if it was not present
1377 * or the entry at the given @index was not @item.
1379 void *radix_tree_delete_item(struct radix_tree_root *root,
1380 unsigned long index, void *item)
1382 struct radix_tree_node *node;
1383 unsigned int offset;
1388 entry = __radix_tree_lookup(root, index, &node, &slot);
1392 if (item && entry != item)
1396 root_tag_clear_all(root);
1401 offset = index & RADIX_TREE_MAP_MASK;
1404 * Clear all tags associated with the item to be deleted.
1405 * This way of doing it would be inefficient, but seldom is any set.
1407 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1408 if (tag_get(node, tag, offset))
1409 radix_tree_tag_clear(root, index, tag);
1412 node->slots[offset] = NULL;
1415 __radix_tree_delete_node(root, node);
1419 EXPORT_SYMBOL(radix_tree_delete_item);
1422 * radix_tree_delete - delete an item from a radix tree
1423 * @root: radix tree root
1426 * Remove the item at @index from the radix tree rooted at @root.
1428 * Returns the address of the deleted item, or NULL if it was not present.
1430 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1432 return radix_tree_delete_item(root, index, NULL);
1434 EXPORT_SYMBOL(radix_tree_delete);
1437 * radix_tree_tagged - test whether any items in the tree are tagged
1438 * @root: radix tree root
1441 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1443 return root_tag_get(root, tag);
1445 EXPORT_SYMBOL(radix_tree_tagged);
1448 radix_tree_node_ctor(void *arg)
1450 struct radix_tree_node *node = arg;
1452 memset(node, 0, sizeof(*node));
1453 INIT_LIST_HEAD(&node->private_list);
1456 static __init unsigned long __maxindex(unsigned int height)
1458 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1459 int shift = RADIX_TREE_INDEX_BITS - width;
1463 if (shift >= BITS_PER_LONG)
1465 return ~0UL >> shift;
1468 static __init void radix_tree_init_maxindex(void)
1472 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1473 height_to_maxindex[i] = __maxindex(i);
1476 static int radix_tree_callback(struct notifier_block *nfb,
1477 unsigned long action,
1480 int cpu = (long)hcpu;
1481 struct radix_tree_preload *rtp;
1482 struct radix_tree_node *node;
1484 /* Free per-cpu pool of perloaded nodes */
1485 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1486 rtp = &per_cpu(radix_tree_preloads, cpu);
1489 rtp->nodes = node->private_data;
1490 kmem_cache_free(radix_tree_node_cachep, node);
1497 void __init radix_tree_init(void)
1499 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1500 sizeof(struct radix_tree_node), 0,
1501 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1502 radix_tree_node_ctor);
1503 radix_tree_init_maxindex();
1504 hotcpu_notifier(radix_tree_callback, 0);