1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2001 Momchil Velikov
4 * Portions Copyright (C) 2001 Christoph Hellwig
5 * Copyright (C) 2005 SGI, Christoph Lameter
6 * Copyright (C) 2006 Nick Piggin
7 * Copyright (C) 2012 Konstantin Khlebnikov
8 * Copyright (C) 2016 Intel, Matthew Wilcox
9 * Copyright (C) 2016 Intel, Ross Zwisler
12 #include <linux/bitmap.h>
13 #include <linux/bitops.h>
14 #include <linux/bug.h>
15 #include <linux/cpu.h>
16 #include <linux/errno.h>
17 #include <linux/export.h>
18 #include <linux/idr.h>
19 #include <linux/init.h>
20 #include <linux/kernel.h>
21 #include <linux/kmemleak.h>
22 #include <linux/percpu.h>
23 #include <linux/preempt.h> /* in_interrupt() */
24 #include <linux/radix-tree.h>
25 #include <linux/rcupdate.h>
26 #include <linux/slab.h>
27 #include <linux/string.h>
28 #include <linux/xarray.h>
32 * Radix tree node cache.
34 struct kmem_cache *radix_tree_node_cachep;
37 * The radix tree is variable-height, so an insert operation not only has
38 * to build the branch to its corresponding item, it also has to build the
39 * branch to existing items if the size has to be increased (by
42 * The worst case is a zero height tree with just a single item at index 0,
43 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
44 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
47 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
50 * The IDR does not have to be as high as the radix tree since it uses
51 * signed integers, not unsigned longs.
53 #define IDR_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(int) - 1)
54 #define IDR_MAX_PATH (DIV_ROUND_UP(IDR_INDEX_BITS, \
55 RADIX_TREE_MAP_SHIFT))
56 #define IDR_PRELOAD_SIZE (IDR_MAX_PATH * 2 - 1)
59 * The IDA is even shorter since it uses a bitmap at the last level.
61 #define IDA_INDEX_BITS (8 * sizeof(int) - 1 - ilog2(IDA_BITMAP_BITS))
62 #define IDA_MAX_PATH (DIV_ROUND_UP(IDA_INDEX_BITS, \
63 RADIX_TREE_MAP_SHIFT))
64 #define IDA_PRELOAD_SIZE (IDA_MAX_PATH * 2 - 1)
67 * Per-cpu pool of preloaded nodes
69 struct radix_tree_preload {
71 /* nodes->parent points to next preallocated node */
72 struct radix_tree_node *nodes;
74 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
76 static inline struct radix_tree_node *entry_to_node(void *ptr)
78 return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
81 static inline void *node_to_entry(void *ptr)
83 return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
86 #define RADIX_TREE_RETRY XA_RETRY_ENTRY
88 static inline unsigned long
89 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
91 return parent ? slot - parent->slots : 0;
94 static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
95 struct radix_tree_node **nodep, unsigned long index)
97 unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
98 void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
100 *nodep = (void *)entry;
104 static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
106 return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
109 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
112 __set_bit(offset, node->tags[tag]);
115 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
118 __clear_bit(offset, node->tags[tag]);
121 static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
124 return test_bit(offset, node->tags[tag]);
127 static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
129 root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
132 static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
134 root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
137 static inline void root_tag_clear_all(struct radix_tree_root *root)
139 root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
142 static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
144 return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
147 static inline unsigned root_tags_get(const struct radix_tree_root *root)
149 return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
152 static inline bool is_idr(const struct radix_tree_root *root)
154 return !!(root->xa_flags & ROOT_IS_IDR);
158 * Returns 1 if any slot in the node has this tag set.
159 * Otherwise returns 0.
161 static inline int any_tag_set(const struct radix_tree_node *node,
165 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
166 if (node->tags[tag][idx])
172 static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
174 bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
178 * radix_tree_find_next_bit - find the next set bit in a memory region
180 * @addr: The address to base the search on
181 * @size: The bitmap size in bits
182 * @offset: The bitnumber to start searching at
184 * Unrollable variant of find_next_bit() for constant size arrays.
185 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
186 * Returns next bit offset, or size if nothing found.
188 static __always_inline unsigned long
189 radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
190 unsigned long offset)
192 const unsigned long *addr = node->tags[tag];
194 if (offset < RADIX_TREE_MAP_SIZE) {
197 addr += offset / BITS_PER_LONG;
198 tmp = *addr >> (offset % BITS_PER_LONG);
200 return __ffs(tmp) + offset;
201 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
202 while (offset < RADIX_TREE_MAP_SIZE) {
205 return __ffs(tmp) + offset;
206 offset += BITS_PER_LONG;
209 return RADIX_TREE_MAP_SIZE;
212 static unsigned int iter_offset(const struct radix_tree_iter *iter)
214 return iter->index & RADIX_TREE_MAP_MASK;
218 * The maximum index which can be stored in a radix tree
220 static inline unsigned long shift_maxindex(unsigned int shift)
222 return (RADIX_TREE_MAP_SIZE << shift) - 1;
225 static inline unsigned long node_maxindex(const struct radix_tree_node *node)
227 return shift_maxindex(node->shift);
230 static unsigned long next_index(unsigned long index,
231 const struct radix_tree_node *node,
232 unsigned long offset)
234 return (index & ~node_maxindex(node)) + (offset << node->shift);
238 * This assumes that the caller has performed appropriate preallocation, and
239 * that the caller has pinned this thread of control to the current CPU.
241 static struct radix_tree_node *
242 radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
243 struct radix_tree_root *root,
244 unsigned int shift, unsigned int offset,
245 unsigned int count, unsigned int nr_values)
247 struct radix_tree_node *ret = NULL;
250 * Preload code isn't irq safe and it doesn't make sense to use
251 * preloading during an interrupt anyway as all the allocations have
252 * to be atomic. So just do normal allocation when in interrupt.
254 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
255 struct radix_tree_preload *rtp;
258 * Even if the caller has preloaded, try to allocate from the
259 * cache first for the new node to get accounted to the memory
262 ret = kmem_cache_alloc(radix_tree_node_cachep,
263 gfp_mask | __GFP_NOWARN);
268 * Provided the caller has preloaded here, we will always
269 * succeed in getting a node here (and never reach
272 rtp = this_cpu_ptr(&radix_tree_preloads);
275 rtp->nodes = ret->parent;
279 * Update the allocation stack trace as this is more useful
282 kmemleak_update_trace(ret);
285 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
287 BUG_ON(radix_tree_is_internal_node(ret));
290 ret->offset = offset;
292 ret->nr_values = nr_values;
293 ret->parent = parent;
299 void radix_tree_node_rcu_free(struct rcu_head *head)
301 struct radix_tree_node *node =
302 container_of(head, struct radix_tree_node, rcu_head);
305 * Must only free zeroed nodes into the slab. We can be left with
306 * non-NULL entries by radix_tree_free_nodes, so clear the entries
309 memset(node->slots, 0, sizeof(node->slots));
310 memset(node->tags, 0, sizeof(node->tags));
311 INIT_LIST_HEAD(&node->private_list);
313 kmem_cache_free(radix_tree_node_cachep, node);
317 radix_tree_node_free(struct radix_tree_node *node)
319 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
323 * Load up this CPU's radix_tree_node buffer with sufficient objects to
324 * ensure that the addition of a single element in the tree cannot fail. On
325 * success, return zero, with preemption disabled. On error, return -ENOMEM
326 * with preemption not disabled.
328 * To make use of this facility, the radix tree must be initialised without
329 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
331 static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
333 struct radix_tree_preload *rtp;
334 struct radix_tree_node *node;
338 * Nodes preloaded by one cgroup can be be used by another cgroup, so
339 * they should never be accounted to any particular memory cgroup.
341 gfp_mask &= ~__GFP_ACCOUNT;
344 rtp = this_cpu_ptr(&radix_tree_preloads);
345 while (rtp->nr < nr) {
347 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
351 rtp = this_cpu_ptr(&radix_tree_preloads);
353 node->parent = rtp->nodes;
357 kmem_cache_free(radix_tree_node_cachep, node);
366 * Load up this CPU's radix_tree_node buffer with sufficient objects to
367 * ensure that the addition of a single element in the tree cannot fail. On
368 * success, return zero, with preemption disabled. On error, return -ENOMEM
369 * with preemption not disabled.
371 * To make use of this facility, the radix tree must be initialised without
372 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
374 int radix_tree_preload(gfp_t gfp_mask)
376 /* Warn on non-sensical use... */
377 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
378 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
380 EXPORT_SYMBOL(radix_tree_preload);
383 * The same as above function, except we don't guarantee preloading happens.
384 * We do it, if we decide it helps. On success, return zero with preemption
385 * disabled. On error, return -ENOMEM with preemption not disabled.
387 int radix_tree_maybe_preload(gfp_t gfp_mask)
389 if (gfpflags_allow_blocking(gfp_mask))
390 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
391 /* Preloading doesn't help anything with this gfp mask, skip it */
395 EXPORT_SYMBOL(radix_tree_maybe_preload);
397 static unsigned radix_tree_load_root(const struct radix_tree_root *root,
398 struct radix_tree_node **nodep, unsigned long *maxindex)
400 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
404 if (likely(radix_tree_is_internal_node(node))) {
405 node = entry_to_node(node);
406 *maxindex = node_maxindex(node);
407 return node->shift + RADIX_TREE_MAP_SHIFT;
415 * Extend a radix tree so it can store key @index.
417 static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
418 unsigned long index, unsigned int shift)
421 unsigned int maxshift;
424 /* Figure out what the shift should be. */
426 while (index > shift_maxindex(maxshift))
427 maxshift += RADIX_TREE_MAP_SHIFT;
429 entry = rcu_dereference_raw(root->xa_head);
430 if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
434 struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
435 root, shift, 0, 1, 0);
440 all_tag_set(node, IDR_FREE);
441 if (!root_tag_get(root, IDR_FREE)) {
442 tag_clear(node, IDR_FREE, 0);
443 root_tag_set(root, IDR_FREE);
446 /* Propagate the aggregated tag info to the new child */
447 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
448 if (root_tag_get(root, tag))
449 tag_set(node, tag, 0);
453 BUG_ON(shift > BITS_PER_LONG);
454 if (radix_tree_is_internal_node(entry)) {
455 entry_to_node(entry)->parent = node;
456 } else if (xa_is_value(entry)) {
457 /* Moving a value entry root->xa_head to a node */
461 * entry was already in the radix tree, so we do not need
462 * rcu_assign_pointer here
464 node->slots[0] = (void __rcu *)entry;
465 entry = node_to_entry(node);
466 rcu_assign_pointer(root->xa_head, entry);
467 shift += RADIX_TREE_MAP_SHIFT;
468 } while (shift <= maxshift);
470 return maxshift + RADIX_TREE_MAP_SHIFT;
474 * radix_tree_shrink - shrink radix tree to minimum height
475 * @root radix tree root
477 static inline bool radix_tree_shrink(struct radix_tree_root *root)
482 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
483 struct radix_tree_node *child;
485 if (!radix_tree_is_internal_node(node))
487 node = entry_to_node(node);
490 * The candidate node has more than one child, or its child
491 * is not at the leftmost slot, we cannot shrink.
493 if (node->count != 1)
495 child = rcu_dereference_raw(node->slots[0]);
500 * For an IDR, we must not shrink entry 0 into the root in
501 * case somebody calls idr_replace() with a pointer that
502 * appears to be an internal entry
504 if (!node->shift && is_idr(root))
507 if (radix_tree_is_internal_node(child))
508 entry_to_node(child)->parent = NULL;
511 * We don't need rcu_assign_pointer(), since we are simply
512 * moving the node from one part of the tree to another: if it
513 * was safe to dereference the old pointer to it
514 * (node->slots[0]), it will be safe to dereference the new
515 * one (root->xa_head) as far as dependent read barriers go.
517 root->xa_head = (void __rcu *)child;
518 if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
519 root_tag_clear(root, IDR_FREE);
522 * We have a dilemma here. The node's slot[0] must not be
523 * NULLed in case there are concurrent lookups expecting to
524 * find the item. However if this was a bottom-level node,
525 * then it may be subject to the slot pointer being visible
526 * to callers dereferencing it. If item corresponding to
527 * slot[0] is subsequently deleted, these callers would expect
528 * their slot to become empty sooner or later.
530 * For example, lockless pagecache will look up a slot, deref
531 * the page pointer, and if the page has 0 refcount it means it
532 * was concurrently deleted from pagecache so try the deref
533 * again. Fortunately there is already a requirement for logic
534 * to retry the entire slot lookup -- the indirect pointer
535 * problem (replacing direct root node with an indirect pointer
536 * also results in a stale slot). So tag the slot as indirect
537 * to force callers to retry.
540 if (!radix_tree_is_internal_node(child)) {
541 node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
544 WARN_ON_ONCE(!list_empty(&node->private_list));
545 radix_tree_node_free(node);
552 static bool delete_node(struct radix_tree_root *root,
553 struct radix_tree_node *node)
555 bool deleted = false;
558 struct radix_tree_node *parent;
561 if (node_to_entry(node) ==
562 rcu_dereference_raw(root->xa_head))
563 deleted |= radix_tree_shrink(root);
567 parent = node->parent;
569 parent->slots[node->offset] = NULL;
573 * Shouldn't the tags already have all been cleared
577 root_tag_clear_all(root);
578 root->xa_head = NULL;
581 WARN_ON_ONCE(!list_empty(&node->private_list));
582 radix_tree_node_free(node);
592 * __radix_tree_create - create a slot in a radix tree
593 * @root: radix tree root
595 * @nodep: returns node
596 * @slotp: returns slot
598 * Create, if necessary, and return the node and slot for an item
599 * at position @index in the radix tree @root.
601 * Until there is more than one item in the tree, no nodes are
602 * allocated and @root->xa_head is used as a direct slot instead of
603 * pointing to a node, in which case *@nodep will be NULL.
605 * Returns -ENOMEM, or 0 for success.
607 static int __radix_tree_create(struct radix_tree_root *root,
608 unsigned long index, struct radix_tree_node **nodep,
611 struct radix_tree_node *node = NULL, *child;
612 void __rcu **slot = (void __rcu **)&root->xa_head;
613 unsigned long maxindex;
614 unsigned int shift, offset = 0;
615 unsigned long max = index;
616 gfp_t gfp = root_gfp_mask(root);
618 shift = radix_tree_load_root(root, &child, &maxindex);
620 /* Make sure the tree is high enough. */
621 if (max > maxindex) {
622 int error = radix_tree_extend(root, gfp, max, shift);
626 child = rcu_dereference_raw(root->xa_head);
630 shift -= RADIX_TREE_MAP_SHIFT;
632 /* Have to add a child node. */
633 child = radix_tree_node_alloc(gfp, node, root, shift,
637 rcu_assign_pointer(*slot, node_to_entry(child));
640 } else if (!radix_tree_is_internal_node(child))
643 /* Go a level down */
644 node = entry_to_node(child);
645 offset = radix_tree_descend(node, &child, index);
646 slot = &node->slots[offset];
657 * Free any nodes below this node. The tree is presumed to not need
658 * shrinking, and any user data in the tree is presumed to not need a
659 * destructor called on it. If we need to add a destructor, we can
660 * add that functionality later. Note that we may not clear tags or
661 * slots from the tree as an RCU walker may still have a pointer into
662 * this subtree. We could replace the entries with RADIX_TREE_RETRY,
663 * but we'll still have to clear those in rcu_free.
665 static void radix_tree_free_nodes(struct radix_tree_node *node)
668 struct radix_tree_node *child = entry_to_node(node);
671 void *entry = rcu_dereference_raw(child->slots[offset]);
672 if (xa_is_node(entry) && child->shift) {
673 child = entry_to_node(entry);
678 while (offset == RADIX_TREE_MAP_SIZE) {
679 struct radix_tree_node *old = child;
680 offset = child->offset + 1;
681 child = child->parent;
682 WARN_ON_ONCE(!list_empty(&old->private_list));
683 radix_tree_node_free(old);
684 if (old == entry_to_node(node))
690 static inline int insert_entries(struct radix_tree_node *node,
691 void __rcu **slot, void *item, bool replace)
695 rcu_assign_pointer(*slot, item);
698 if (xa_is_value(item))
705 * __radix_tree_insert - insert into a radix tree
706 * @root: radix tree root
708 * @item: item to insert
710 * Insert an item into the radix tree at position @index.
712 int radix_tree_insert(struct radix_tree_root *root, unsigned long index,
715 struct radix_tree_node *node;
719 BUG_ON(radix_tree_is_internal_node(item));
721 error = __radix_tree_create(root, index, &node, &slot);
725 error = insert_entries(node, slot, item, false);
730 unsigned offset = get_slot_offset(node, slot);
731 BUG_ON(tag_get(node, 0, offset));
732 BUG_ON(tag_get(node, 1, offset));
733 BUG_ON(tag_get(node, 2, offset));
735 BUG_ON(root_tags_get(root));
740 EXPORT_SYMBOL(radix_tree_insert);
743 * __radix_tree_lookup - lookup an item in a radix tree
744 * @root: radix tree root
746 * @nodep: returns node
747 * @slotp: returns slot
749 * Lookup and return the item at position @index in the radix
752 * Until there is more than one item in the tree, no nodes are
753 * allocated and @root->xa_head is used as a direct slot instead of
754 * pointing to a node, in which case *@nodep will be NULL.
756 void *__radix_tree_lookup(const struct radix_tree_root *root,
757 unsigned long index, struct radix_tree_node **nodep,
760 struct radix_tree_node *node, *parent;
761 unsigned long maxindex;
766 slot = (void __rcu **)&root->xa_head;
767 radix_tree_load_root(root, &node, &maxindex);
768 if (index > maxindex)
771 while (radix_tree_is_internal_node(node)) {
774 parent = entry_to_node(node);
775 offset = radix_tree_descend(parent, &node, index);
776 slot = parent->slots + offset;
777 if (node == RADIX_TREE_RETRY)
779 if (parent->shift == 0)
791 * radix_tree_lookup_slot - lookup a slot in a radix tree
792 * @root: radix tree root
795 * Returns: the slot corresponding to the position @index in the
796 * radix tree @root. This is useful for update-if-exists operations.
798 * This function can be called under rcu_read_lock iff the slot is not
799 * modified by radix_tree_replace_slot, otherwise it must be called
800 * exclusive from other writers. Any dereference of the slot must be done
801 * using radix_tree_deref_slot.
803 void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
808 if (!__radix_tree_lookup(root, index, NULL, &slot))
812 EXPORT_SYMBOL(radix_tree_lookup_slot);
815 * radix_tree_lookup - perform lookup operation on a radix tree
816 * @root: radix tree root
819 * Lookup the item at the position @index in the radix tree @root.
821 * This function can be called under rcu_read_lock, however the caller
822 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
823 * them safely). No RCU barriers are required to access or modify the
824 * returned item, however.
826 void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
828 return __radix_tree_lookup(root, index, NULL, NULL);
830 EXPORT_SYMBOL(radix_tree_lookup);
832 static void replace_slot(void __rcu **slot, void *item,
833 struct radix_tree_node *node, int count, int values)
835 if (node && (count || values)) {
836 node->count += count;
837 node->nr_values += values;
840 rcu_assign_pointer(*slot, item);
843 static bool node_tag_get(const struct radix_tree_root *root,
844 const struct radix_tree_node *node,
845 unsigned int tag, unsigned int offset)
848 return tag_get(node, tag, offset);
849 return root_tag_get(root, tag);
853 * IDR users want to be able to store NULL in the tree, so if the slot isn't
854 * free, don't adjust the count, even if it's transitioning between NULL and
855 * non-NULL. For the IDA, we mark slots as being IDR_FREE while they still
856 * have empty bits, but it only stores NULL in slots when they're being
859 static int calculate_count(struct radix_tree_root *root,
860 struct radix_tree_node *node, void __rcu **slot,
861 void *item, void *old)
864 unsigned offset = get_slot_offset(node, slot);
865 bool free = node_tag_get(root, node, IDR_FREE, offset);
871 return !!item - !!old;
875 * __radix_tree_replace - replace item in a slot
876 * @root: radix tree root
877 * @node: pointer to tree node
878 * @slot: pointer to slot in @node
879 * @item: new item to store in the slot.
881 * For use with __radix_tree_lookup(). Caller must hold tree write locked
882 * across slot lookup and replacement.
884 void __radix_tree_replace(struct radix_tree_root *root,
885 struct radix_tree_node *node,
886 void __rcu **slot, void *item)
888 void *old = rcu_dereference_raw(*slot);
889 int values = !!xa_is_value(item) - !!xa_is_value(old);
890 int count = calculate_count(root, node, slot, item, old);
893 * This function supports replacing value entries and
894 * deleting entries, but that needs accounting against the
895 * node unless the slot is root->xa_head.
897 WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
899 replace_slot(slot, item, node, count, values);
904 delete_node(root, node);
908 * radix_tree_replace_slot - replace item in a slot
909 * @root: radix tree root
910 * @slot: pointer to slot
911 * @item: new item to store in the slot.
913 * For use with radix_tree_lookup_slot() and
914 * radix_tree_gang_lookup_tag_slot(). Caller must hold tree write locked
915 * across slot lookup and replacement.
917 * NOTE: This cannot be used to switch between non-entries (empty slots),
918 * regular entries, and value entries, as that requires accounting
919 * inside the radix tree node. When switching from one type of entry or
920 * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
921 * radix_tree_iter_replace().
923 void radix_tree_replace_slot(struct radix_tree_root *root,
924 void __rcu **slot, void *item)
926 __radix_tree_replace(root, NULL, slot, item);
928 EXPORT_SYMBOL(radix_tree_replace_slot);
931 * radix_tree_iter_replace - replace item in a slot
932 * @root: radix tree root
933 * @slot: pointer to slot
934 * @item: new item to store in the slot.
936 * For use with radix_tree_for_each_slot().
937 * Caller must hold tree write locked.
939 void radix_tree_iter_replace(struct radix_tree_root *root,
940 const struct radix_tree_iter *iter,
941 void __rcu **slot, void *item)
943 __radix_tree_replace(root, iter->node, slot, item);
946 static void node_tag_set(struct radix_tree_root *root,
947 struct radix_tree_node *node,
948 unsigned int tag, unsigned int offset)
951 if (tag_get(node, tag, offset))
953 tag_set(node, tag, offset);
954 offset = node->offset;
958 if (!root_tag_get(root, tag))
959 root_tag_set(root, tag);
963 * radix_tree_tag_set - set a tag on a radix tree node
964 * @root: radix tree root
968 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
969 * corresponding to @index in the radix tree. From
970 * the root all the way down to the leaf node.
972 * Returns the address of the tagged item. Setting a tag on a not-present
975 void *radix_tree_tag_set(struct radix_tree_root *root,
976 unsigned long index, unsigned int tag)
978 struct radix_tree_node *node, *parent;
979 unsigned long maxindex;
981 radix_tree_load_root(root, &node, &maxindex);
982 BUG_ON(index > maxindex);
984 while (radix_tree_is_internal_node(node)) {
987 parent = entry_to_node(node);
988 offset = radix_tree_descend(parent, &node, index);
991 if (!tag_get(parent, tag, offset))
992 tag_set(parent, tag, offset);
995 /* set the root's tag bit */
996 if (!root_tag_get(root, tag))
997 root_tag_set(root, tag);
1001 EXPORT_SYMBOL(radix_tree_tag_set);
1003 static void node_tag_clear(struct radix_tree_root *root,
1004 struct radix_tree_node *node,
1005 unsigned int tag, unsigned int offset)
1008 if (!tag_get(node, tag, offset))
1010 tag_clear(node, tag, offset);
1011 if (any_tag_set(node, tag))
1014 offset = node->offset;
1015 node = node->parent;
1018 /* clear the root's tag bit */
1019 if (root_tag_get(root, tag))
1020 root_tag_clear(root, tag);
1024 * radix_tree_tag_clear - clear a tag on a radix tree node
1025 * @root: radix tree root
1029 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1030 * corresponding to @index in the radix tree. If this causes
1031 * the leaf node to have no tags set then clear the tag in the
1032 * next-to-leaf node, etc.
1034 * Returns the address of the tagged item on success, else NULL. ie:
1035 * has the same return value and semantics as radix_tree_lookup().
1037 void *radix_tree_tag_clear(struct radix_tree_root *root,
1038 unsigned long index, unsigned int tag)
1040 struct radix_tree_node *node, *parent;
1041 unsigned long maxindex;
1042 int uninitialized_var(offset);
1044 radix_tree_load_root(root, &node, &maxindex);
1045 if (index > maxindex)
1050 while (radix_tree_is_internal_node(node)) {
1051 parent = entry_to_node(node);
1052 offset = radix_tree_descend(parent, &node, index);
1056 node_tag_clear(root, parent, tag, offset);
1060 EXPORT_SYMBOL(radix_tree_tag_clear);
1063 * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1064 * @root: radix tree root
1065 * @iter: iterator state
1066 * @tag: tag to clear
1068 void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1069 const struct radix_tree_iter *iter, unsigned int tag)
1071 node_tag_clear(root, iter->node, tag, iter_offset(iter));
1075 * radix_tree_tag_get - get a tag on a radix tree node
1076 * @root: radix tree root
1078 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
1082 * 0: tag not present or not set
1085 * Note that the return value of this function may not be relied on, even if
1086 * the RCU lock is held, unless tag modification and node deletion are excluded
1089 int radix_tree_tag_get(const struct radix_tree_root *root,
1090 unsigned long index, unsigned int tag)
1092 struct radix_tree_node *node, *parent;
1093 unsigned long maxindex;
1095 if (!root_tag_get(root, tag))
1098 radix_tree_load_root(root, &node, &maxindex);
1099 if (index > maxindex)
1102 while (radix_tree_is_internal_node(node)) {
1105 parent = entry_to_node(node);
1106 offset = radix_tree_descend(parent, &node, index);
1108 if (!tag_get(parent, tag, offset))
1110 if (node == RADIX_TREE_RETRY)
1116 EXPORT_SYMBOL(radix_tree_tag_get);
1118 /* Construct iter->tags bit-mask from node->tags[tag] array */
1119 static void set_iter_tags(struct radix_tree_iter *iter,
1120 struct radix_tree_node *node, unsigned offset,
1123 unsigned tag_long = offset / BITS_PER_LONG;
1124 unsigned tag_bit = offset % BITS_PER_LONG;
1131 iter->tags = node->tags[tag][tag_long] >> tag_bit;
1133 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1134 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1135 /* Pick tags from next element */
1137 iter->tags |= node->tags[tag][tag_long + 1] <<
1138 (BITS_PER_LONG - tag_bit);
1139 /* Clip chunk size, here only BITS_PER_LONG tags */
1140 iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1144 void __rcu **radix_tree_iter_resume(void __rcu **slot,
1145 struct radix_tree_iter *iter)
1148 iter->index = __radix_tree_iter_add(iter, 1);
1149 iter->next_index = iter->index;
1153 EXPORT_SYMBOL(radix_tree_iter_resume);
1156 * radix_tree_next_chunk - find next chunk of slots for iteration
1158 * @root: radix tree root
1159 * @iter: iterator state
1160 * @flags: RADIX_TREE_ITER_* flags and tag index
1161 * Returns: pointer to chunk first slot, or NULL if iteration is over
1163 void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1164 struct radix_tree_iter *iter, unsigned flags)
1166 unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1167 struct radix_tree_node *node, *child;
1168 unsigned long index, offset, maxindex;
1170 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1174 * Catch next_index overflow after ~0UL. iter->index never overflows
1175 * during iterating; it can be zero only at the beginning.
1176 * And we cannot overflow iter->next_index in a single step,
1177 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1179 * This condition also used by radix_tree_next_slot() to stop
1180 * contiguous iterating, and forbid switching to the next chunk.
1182 index = iter->next_index;
1183 if (!index && iter->index)
1187 radix_tree_load_root(root, &child, &maxindex);
1188 if (index > maxindex)
1193 if (!radix_tree_is_internal_node(child)) {
1194 /* Single-slot tree */
1195 iter->index = index;
1196 iter->next_index = maxindex + 1;
1199 return (void __rcu **)&root->xa_head;
1203 node = entry_to_node(child);
1204 offset = radix_tree_descend(node, &child, index);
1206 if ((flags & RADIX_TREE_ITER_TAGGED) ?
1207 !tag_get(node, tag, offset) : !child) {
1209 if (flags & RADIX_TREE_ITER_CONTIG)
1212 if (flags & RADIX_TREE_ITER_TAGGED)
1213 offset = radix_tree_find_next_bit(node, tag,
1216 while (++offset < RADIX_TREE_MAP_SIZE) {
1217 void *slot = rcu_dereference_raw(
1218 node->slots[offset]);
1222 index &= ~node_maxindex(node);
1223 index += offset << node->shift;
1224 /* Overflow after ~0UL */
1227 if (offset == RADIX_TREE_MAP_SIZE)
1229 child = rcu_dereference_raw(node->slots[offset]);
1234 if (child == RADIX_TREE_RETRY)
1236 } while (node->shift && radix_tree_is_internal_node(child));
1238 /* Update the iterator state */
1239 iter->index = (index &~ node_maxindex(node)) | offset;
1240 iter->next_index = (index | node_maxindex(node)) + 1;
1243 if (flags & RADIX_TREE_ITER_TAGGED)
1244 set_iter_tags(iter, node, offset, tag);
1246 return node->slots + offset;
1248 EXPORT_SYMBOL(radix_tree_next_chunk);
1251 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1252 * @root: radix tree root
1253 * @results: where the results of the lookup are placed
1254 * @first_index: start the lookup from this key
1255 * @max_items: place up to this many items at *results
1257 * Performs an index-ascending scan of the tree for present items. Places
1258 * them at *@results and returns the number of items which were placed at
1261 * The implementation is naive.
1263 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1264 * rcu_read_lock. In this case, rather than the returned results being
1265 * an atomic snapshot of the tree at a single point in time, the
1266 * semantics of an RCU protected gang lookup are as though multiple
1267 * radix_tree_lookups have been issued in individual locks, and results
1268 * stored in 'results'.
1271 radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1272 unsigned long first_index, unsigned int max_items)
1274 struct radix_tree_iter iter;
1276 unsigned int ret = 0;
1278 if (unlikely(!max_items))
1281 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1282 results[ret] = rcu_dereference_raw(*slot);
1285 if (radix_tree_is_internal_node(results[ret])) {
1286 slot = radix_tree_iter_retry(&iter);
1289 if (++ret == max_items)
1295 EXPORT_SYMBOL(radix_tree_gang_lookup);
1298 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1300 * @root: radix tree root
1301 * @results: where the results of the lookup are placed
1302 * @first_index: start the lookup from this key
1303 * @max_items: place up to this many items at *results
1304 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1306 * Performs an index-ascending scan of the tree for present items which
1307 * have the tag indexed by @tag set. Places the items at *@results and
1308 * returns the number of items which were placed at *@results.
1311 radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1312 unsigned long first_index, unsigned int max_items,
1315 struct radix_tree_iter iter;
1317 unsigned int ret = 0;
1319 if (unlikely(!max_items))
1322 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1323 results[ret] = rcu_dereference_raw(*slot);
1326 if (radix_tree_is_internal_node(results[ret])) {
1327 slot = radix_tree_iter_retry(&iter);
1330 if (++ret == max_items)
1336 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1339 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1340 * radix tree based on a tag
1341 * @root: radix tree root
1342 * @results: where the results of the lookup are placed
1343 * @first_index: start the lookup from this key
1344 * @max_items: place up to this many items at *results
1345 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1347 * Performs an index-ascending scan of the tree for present items which
1348 * have the tag indexed by @tag set. Places the slots at *@results and
1349 * returns the number of slots which were placed at *@results.
1352 radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1353 void __rcu ***results, unsigned long first_index,
1354 unsigned int max_items, unsigned int tag)
1356 struct radix_tree_iter iter;
1358 unsigned int ret = 0;
1360 if (unlikely(!max_items))
1363 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1364 results[ret] = slot;
1365 if (++ret == max_items)
1371 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1373 static bool __radix_tree_delete(struct radix_tree_root *root,
1374 struct radix_tree_node *node, void __rcu **slot)
1376 void *old = rcu_dereference_raw(*slot);
1377 int values = xa_is_value(old) ? -1 : 0;
1378 unsigned offset = get_slot_offset(node, slot);
1382 node_tag_set(root, node, IDR_FREE, offset);
1384 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1385 node_tag_clear(root, node, tag, offset);
1387 replace_slot(slot, NULL, node, -1, values);
1388 return node && delete_node(root, node);
1392 * radix_tree_iter_delete - delete the entry at this iterator position
1393 * @root: radix tree root
1394 * @iter: iterator state
1395 * @slot: pointer to slot
1397 * Delete the entry at the position currently pointed to by the iterator.
1398 * This may result in the current node being freed; if it is, the iterator
1399 * is advanced so that it will not reference the freed memory. This
1400 * function may be called without any locking if there are no other threads
1401 * which can access this tree.
1403 void radix_tree_iter_delete(struct radix_tree_root *root,
1404 struct radix_tree_iter *iter, void __rcu **slot)
1406 if (__radix_tree_delete(root, iter->node, slot))
1407 iter->index = iter->next_index;
1409 EXPORT_SYMBOL(radix_tree_iter_delete);
1412 * radix_tree_delete_item - delete an item from a radix tree
1413 * @root: radix tree root
1415 * @item: expected item
1417 * Remove @item at @index from the radix tree rooted at @root.
1419 * Return: the deleted entry, or %NULL if it was not present
1420 * or the entry at the given @index was not @item.
1422 void *radix_tree_delete_item(struct radix_tree_root *root,
1423 unsigned long index, void *item)
1425 struct radix_tree_node *node = NULL;
1426 void __rcu **slot = NULL;
1429 entry = __radix_tree_lookup(root, index, &node, &slot);
1432 if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
1433 get_slot_offset(node, slot))))
1436 if (item && entry != item)
1439 __radix_tree_delete(root, node, slot);
1443 EXPORT_SYMBOL(radix_tree_delete_item);
1446 * radix_tree_delete - delete an entry from a radix tree
1447 * @root: radix tree root
1450 * Remove the entry at @index from the radix tree rooted at @root.
1452 * Return: The deleted entry, or %NULL if it was not present.
1454 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1456 return radix_tree_delete_item(root, index, NULL);
1458 EXPORT_SYMBOL(radix_tree_delete);
1461 * radix_tree_tagged - test whether any items in the tree are tagged
1462 * @root: radix tree root
1465 int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
1467 return root_tag_get(root, tag);
1469 EXPORT_SYMBOL(radix_tree_tagged);
1472 * idr_preload - preload for idr_alloc()
1473 * @gfp_mask: allocation mask to use for preloading
1475 * Preallocate memory to use for the next call to idr_alloc(). This function
1476 * returns with preemption disabled. It will be enabled by idr_preload_end().
1478 void idr_preload(gfp_t gfp_mask)
1480 if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
1483 EXPORT_SYMBOL(idr_preload);
1485 void __rcu **idr_get_free(struct radix_tree_root *root,
1486 struct radix_tree_iter *iter, gfp_t gfp,
1489 struct radix_tree_node *node = NULL, *child;
1490 void __rcu **slot = (void __rcu **)&root->xa_head;
1491 unsigned long maxindex, start = iter->next_index;
1492 unsigned int shift, offset = 0;
1495 shift = radix_tree_load_root(root, &child, &maxindex);
1496 if (!radix_tree_tagged(root, IDR_FREE))
1497 start = max(start, maxindex + 1);
1499 return ERR_PTR(-ENOSPC);
1501 if (start > maxindex) {
1502 int error = radix_tree_extend(root, gfp, start, shift);
1504 return ERR_PTR(error);
1506 child = rcu_dereference_raw(root->xa_head);
1508 if (start == 0 && shift == 0)
1509 shift = RADIX_TREE_MAP_SHIFT;
1512 shift -= RADIX_TREE_MAP_SHIFT;
1513 if (child == NULL) {
1514 /* Have to add a child node. */
1515 child = radix_tree_node_alloc(gfp, node, root, shift,
1518 return ERR_PTR(-ENOMEM);
1519 all_tag_set(child, IDR_FREE);
1520 rcu_assign_pointer(*slot, node_to_entry(child));
1523 } else if (!radix_tree_is_internal_node(child))
1526 node = entry_to_node(child);
1527 offset = radix_tree_descend(node, &child, start);
1528 if (!tag_get(node, IDR_FREE, offset)) {
1529 offset = radix_tree_find_next_bit(node, IDR_FREE,
1531 start = next_index(start, node, offset);
1532 if (start > max || start == 0)
1533 return ERR_PTR(-ENOSPC);
1534 while (offset == RADIX_TREE_MAP_SIZE) {
1535 offset = node->offset + 1;
1536 node = node->parent;
1539 shift = node->shift;
1541 child = rcu_dereference_raw(node->slots[offset]);
1543 slot = &node->slots[offset];
1546 iter->index = start;
1548 iter->next_index = 1 + min(max, (start | node_maxindex(node)));
1550 iter->next_index = 1;
1552 set_iter_tags(iter, node, offset, IDR_FREE);
1558 * idr_destroy - release all internal memory from an IDR
1561 * After this function is called, the IDR is empty, and may be reused or
1562 * the data structure containing it may be freed.
1564 * A typical clean-up sequence for objects stored in an idr tree will use
1565 * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1566 * free the memory used to keep track of those objects.
1568 void idr_destroy(struct idr *idr)
1570 struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
1571 if (radix_tree_is_internal_node(node))
1572 radix_tree_free_nodes(node);
1573 idr->idr_rt.xa_head = NULL;
1574 root_tag_set(&idr->idr_rt, IDR_FREE);
1576 EXPORT_SYMBOL(idr_destroy);
1579 radix_tree_node_ctor(void *arg)
1581 struct radix_tree_node *node = arg;
1583 memset(node, 0, sizeof(*node));
1584 INIT_LIST_HEAD(&node->private_list);
1587 static int radix_tree_cpu_dead(unsigned int cpu)
1589 struct radix_tree_preload *rtp;
1590 struct radix_tree_node *node;
1592 /* Free per-cpu pool of preloaded nodes */
1593 rtp = &per_cpu(radix_tree_preloads, cpu);
1596 rtp->nodes = node->parent;
1597 kmem_cache_free(radix_tree_node_cachep, node);
1603 void __init radix_tree_init(void)
1607 BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
1608 BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
1609 BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
1610 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1611 sizeof(struct radix_tree_node), 0,
1612 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1613 radix_tree_node_ctor);
1614 ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
1615 NULL, radix_tree_cpu_dead);