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 * Per-cpu pool of preloaded nodes
61 struct radix_tree_preload
{
63 /* nodes->parent points to next preallocated node */
64 struct radix_tree_node
*nodes
;
66 static DEFINE_PER_CPU(struct radix_tree_preload
, radix_tree_preloads
) = { 0, };
68 static inline struct radix_tree_node
*entry_to_node(void *ptr
)
70 return (void *)((unsigned long)ptr
& ~RADIX_TREE_INTERNAL_NODE
);
73 static inline void *node_to_entry(void *ptr
)
75 return (void *)((unsigned long)ptr
| RADIX_TREE_INTERNAL_NODE
);
78 #define RADIX_TREE_RETRY XA_RETRY_ENTRY
80 static inline unsigned long
81 get_slot_offset(const struct radix_tree_node
*parent
, void __rcu
**slot
)
83 return parent
? slot
- parent
->slots
: 0;
86 static unsigned int radix_tree_descend(const struct radix_tree_node
*parent
,
87 struct radix_tree_node
**nodep
, unsigned long index
)
89 unsigned int offset
= (index
>> parent
->shift
) & RADIX_TREE_MAP_MASK
;
90 void __rcu
**entry
= rcu_dereference_raw(parent
->slots
[offset
]);
92 *nodep
= (void *)entry
;
96 static inline gfp_t
root_gfp_mask(const struct radix_tree_root
*root
)
98 return root
->xa_flags
& (__GFP_BITS_MASK
& ~GFP_ZONEMASK
);
101 static inline void tag_set(struct radix_tree_node
*node
, unsigned int tag
,
104 __set_bit(offset
, node
->tags
[tag
]);
107 static inline void tag_clear(struct radix_tree_node
*node
, unsigned int tag
,
110 __clear_bit(offset
, node
->tags
[tag
]);
113 static inline int tag_get(const struct radix_tree_node
*node
, unsigned int tag
,
116 return test_bit(offset
, node
->tags
[tag
]);
119 static inline void root_tag_set(struct radix_tree_root
*root
, unsigned tag
)
121 root
->xa_flags
|= (__force gfp_t
)(1 << (tag
+ ROOT_TAG_SHIFT
));
124 static inline void root_tag_clear(struct radix_tree_root
*root
, unsigned tag
)
126 root
->xa_flags
&= (__force gfp_t
)~(1 << (tag
+ ROOT_TAG_SHIFT
));
129 static inline void root_tag_clear_all(struct radix_tree_root
*root
)
131 root
->xa_flags
&= (__force gfp_t
)((1 << ROOT_TAG_SHIFT
) - 1);
134 static inline int root_tag_get(const struct radix_tree_root
*root
, unsigned tag
)
136 return (__force
int)root
->xa_flags
& (1 << (tag
+ ROOT_TAG_SHIFT
));
139 static inline unsigned root_tags_get(const struct radix_tree_root
*root
)
141 return (__force
unsigned)root
->xa_flags
>> ROOT_TAG_SHIFT
;
144 static inline bool is_idr(const struct radix_tree_root
*root
)
146 return !!(root
->xa_flags
& ROOT_IS_IDR
);
150 * Returns 1 if any slot in the node has this tag set.
151 * Otherwise returns 0.
153 static inline int any_tag_set(const struct radix_tree_node
*node
,
157 for (idx
= 0; idx
< RADIX_TREE_TAG_LONGS
; idx
++) {
158 if (node
->tags
[tag
][idx
])
164 static inline void all_tag_set(struct radix_tree_node
*node
, unsigned int tag
)
166 bitmap_fill(node
->tags
[tag
], RADIX_TREE_MAP_SIZE
);
170 * radix_tree_find_next_bit - find the next set bit in a memory region
172 * @addr: The address to base the search on
173 * @size: The bitmap size in bits
174 * @offset: The bitnumber to start searching at
176 * Unrollable variant of find_next_bit() for constant size arrays.
177 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
178 * Returns next bit offset, or size if nothing found.
180 static __always_inline
unsigned long
181 radix_tree_find_next_bit(struct radix_tree_node
*node
, unsigned int tag
,
182 unsigned long offset
)
184 const unsigned long *addr
= node
->tags
[tag
];
186 if (offset
< RADIX_TREE_MAP_SIZE
) {
189 addr
+= offset
/ BITS_PER_LONG
;
190 tmp
= *addr
>> (offset
% BITS_PER_LONG
);
192 return __ffs(tmp
) + offset
;
193 offset
= (offset
+ BITS_PER_LONG
) & ~(BITS_PER_LONG
- 1);
194 while (offset
< RADIX_TREE_MAP_SIZE
) {
197 return __ffs(tmp
) + offset
;
198 offset
+= BITS_PER_LONG
;
201 return RADIX_TREE_MAP_SIZE
;
204 static unsigned int iter_offset(const struct radix_tree_iter
*iter
)
206 return iter
->index
& RADIX_TREE_MAP_MASK
;
210 * The maximum index which can be stored in a radix tree
212 static inline unsigned long shift_maxindex(unsigned int shift
)
214 return (RADIX_TREE_MAP_SIZE
<< shift
) - 1;
217 static inline unsigned long node_maxindex(const struct radix_tree_node
*node
)
219 return shift_maxindex(node
->shift
);
222 static unsigned long next_index(unsigned long index
,
223 const struct radix_tree_node
*node
,
224 unsigned long offset
)
226 return (index
& ~node_maxindex(node
)) + (offset
<< node
->shift
);
230 * This assumes that the caller has performed appropriate preallocation, and
231 * that the caller has pinned this thread of control to the current CPU.
233 static struct radix_tree_node
*
234 radix_tree_node_alloc(gfp_t gfp_mask
, struct radix_tree_node
*parent
,
235 struct radix_tree_root
*root
,
236 unsigned int shift
, unsigned int offset
,
237 unsigned int count
, unsigned int nr_values
)
239 struct radix_tree_node
*ret
= NULL
;
242 * Preload code isn't irq safe and it doesn't make sense to use
243 * preloading during an interrupt anyway as all the allocations have
244 * to be atomic. So just do normal allocation when in interrupt.
246 if (!gfpflags_allow_blocking(gfp_mask
) && !in_interrupt()) {
247 struct radix_tree_preload
*rtp
;
250 * Even if the caller has preloaded, try to allocate from the
251 * cache first for the new node to get accounted to the memory
254 ret
= kmem_cache_alloc(radix_tree_node_cachep
,
255 gfp_mask
| __GFP_NOWARN
);
260 * Provided the caller has preloaded here, we will always
261 * succeed in getting a node here (and never reach
264 rtp
= this_cpu_ptr(&radix_tree_preloads
);
267 rtp
->nodes
= ret
->parent
;
271 * Update the allocation stack trace as this is more useful
274 kmemleak_update_trace(ret
);
277 ret
= kmem_cache_alloc(radix_tree_node_cachep
, gfp_mask
);
279 BUG_ON(radix_tree_is_internal_node(ret
));
282 ret
->offset
= offset
;
284 ret
->nr_values
= nr_values
;
285 ret
->parent
= parent
;
291 void radix_tree_node_rcu_free(struct rcu_head
*head
)
293 struct radix_tree_node
*node
=
294 container_of(head
, struct radix_tree_node
, rcu_head
);
297 * Must only free zeroed nodes into the slab. We can be left with
298 * non-NULL entries by radix_tree_free_nodes, so clear the entries
301 memset(node
->slots
, 0, sizeof(node
->slots
));
302 memset(node
->tags
, 0, sizeof(node
->tags
));
303 INIT_LIST_HEAD(&node
->private_list
);
305 kmem_cache_free(radix_tree_node_cachep
, node
);
309 radix_tree_node_free(struct radix_tree_node
*node
)
311 call_rcu(&node
->rcu_head
, radix_tree_node_rcu_free
);
315 * Load up this CPU's radix_tree_node buffer with sufficient objects to
316 * ensure that the addition of a single element in the tree cannot fail. On
317 * success, return zero, with preemption disabled. On error, return -ENOMEM
318 * with preemption not disabled.
320 * To make use of this facility, the radix tree must be initialised without
321 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
323 static __must_check
int __radix_tree_preload(gfp_t gfp_mask
, unsigned nr
)
325 struct radix_tree_preload
*rtp
;
326 struct radix_tree_node
*node
;
330 * Nodes preloaded by one cgroup can be be used by another cgroup, so
331 * they should never be accounted to any particular memory cgroup.
333 gfp_mask
&= ~__GFP_ACCOUNT
;
336 rtp
= this_cpu_ptr(&radix_tree_preloads
);
337 while (rtp
->nr
< nr
) {
339 node
= kmem_cache_alloc(radix_tree_node_cachep
, gfp_mask
);
343 rtp
= this_cpu_ptr(&radix_tree_preloads
);
345 node
->parent
= rtp
->nodes
;
349 kmem_cache_free(radix_tree_node_cachep
, node
);
358 * Load up this CPU's radix_tree_node buffer with sufficient objects to
359 * ensure that the addition of a single element in the tree cannot fail. On
360 * success, return zero, with preemption disabled. On error, return -ENOMEM
361 * with preemption not disabled.
363 * To make use of this facility, the radix tree must be initialised without
364 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
366 int radix_tree_preload(gfp_t gfp_mask
)
368 /* Warn on non-sensical use... */
369 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask
));
370 return __radix_tree_preload(gfp_mask
, RADIX_TREE_PRELOAD_SIZE
);
372 EXPORT_SYMBOL(radix_tree_preload
);
375 * The same as above function, except we don't guarantee preloading happens.
376 * We do it, if we decide it helps. On success, return zero with preemption
377 * disabled. On error, return -ENOMEM with preemption not disabled.
379 int radix_tree_maybe_preload(gfp_t gfp_mask
)
381 if (gfpflags_allow_blocking(gfp_mask
))
382 return __radix_tree_preload(gfp_mask
, RADIX_TREE_PRELOAD_SIZE
);
383 /* Preloading doesn't help anything with this gfp mask, skip it */
387 EXPORT_SYMBOL(radix_tree_maybe_preload
);
389 static unsigned radix_tree_load_root(const struct radix_tree_root
*root
,
390 struct radix_tree_node
**nodep
, unsigned long *maxindex
)
392 struct radix_tree_node
*node
= rcu_dereference_raw(root
->xa_head
);
396 if (likely(radix_tree_is_internal_node(node
))) {
397 node
= entry_to_node(node
);
398 *maxindex
= node_maxindex(node
);
399 return node
->shift
+ RADIX_TREE_MAP_SHIFT
;
407 * Extend a radix tree so it can store key @index.
409 static int radix_tree_extend(struct radix_tree_root
*root
, gfp_t gfp
,
410 unsigned long index
, unsigned int shift
)
413 unsigned int maxshift
;
416 /* Figure out what the shift should be. */
418 while (index
> shift_maxindex(maxshift
))
419 maxshift
+= RADIX_TREE_MAP_SHIFT
;
421 entry
= rcu_dereference_raw(root
->xa_head
);
422 if (!entry
&& (!is_idr(root
) || root_tag_get(root
, IDR_FREE
)))
426 struct radix_tree_node
*node
= radix_tree_node_alloc(gfp
, NULL
,
427 root
, shift
, 0, 1, 0);
432 all_tag_set(node
, IDR_FREE
);
433 if (!root_tag_get(root
, IDR_FREE
)) {
434 tag_clear(node
, IDR_FREE
, 0);
435 root_tag_set(root
, IDR_FREE
);
438 /* Propagate the aggregated tag info to the new child */
439 for (tag
= 0; tag
< RADIX_TREE_MAX_TAGS
; tag
++) {
440 if (root_tag_get(root
, tag
))
441 tag_set(node
, tag
, 0);
445 BUG_ON(shift
> BITS_PER_LONG
);
446 if (radix_tree_is_internal_node(entry
)) {
447 entry_to_node(entry
)->parent
= node
;
448 } else if (xa_is_value(entry
)) {
449 /* Moving a value entry root->xa_head to a node */
453 * entry was already in the radix tree, so we do not need
454 * rcu_assign_pointer here
456 node
->slots
[0] = (void __rcu
*)entry
;
457 entry
= node_to_entry(node
);
458 rcu_assign_pointer(root
->xa_head
, entry
);
459 shift
+= RADIX_TREE_MAP_SHIFT
;
460 } while (shift
<= maxshift
);
462 return maxshift
+ RADIX_TREE_MAP_SHIFT
;
466 * radix_tree_shrink - shrink radix tree to minimum height
467 * @root radix tree root
469 static inline bool radix_tree_shrink(struct radix_tree_root
*root
)
474 struct radix_tree_node
*node
= rcu_dereference_raw(root
->xa_head
);
475 struct radix_tree_node
*child
;
477 if (!radix_tree_is_internal_node(node
))
479 node
= entry_to_node(node
);
482 * The candidate node has more than one child, or its child
483 * is not at the leftmost slot, we cannot shrink.
485 if (node
->count
!= 1)
487 child
= rcu_dereference_raw(node
->slots
[0]);
492 * For an IDR, we must not shrink entry 0 into the root in
493 * case somebody calls idr_replace() with a pointer that
494 * appears to be an internal entry
496 if (!node
->shift
&& is_idr(root
))
499 if (radix_tree_is_internal_node(child
))
500 entry_to_node(child
)->parent
= NULL
;
503 * We don't need rcu_assign_pointer(), since we are simply
504 * moving the node from one part of the tree to another: if it
505 * was safe to dereference the old pointer to it
506 * (node->slots[0]), it will be safe to dereference the new
507 * one (root->xa_head) as far as dependent read barriers go.
509 root
->xa_head
= (void __rcu
*)child
;
510 if (is_idr(root
) && !tag_get(node
, IDR_FREE
, 0))
511 root_tag_clear(root
, IDR_FREE
);
514 * We have a dilemma here. The node's slot[0] must not be
515 * NULLed in case there are concurrent lookups expecting to
516 * find the item. However if this was a bottom-level node,
517 * then it may be subject to the slot pointer being visible
518 * to callers dereferencing it. If item corresponding to
519 * slot[0] is subsequently deleted, these callers would expect
520 * their slot to become empty sooner or later.
522 * For example, lockless pagecache will look up a slot, deref
523 * the page pointer, and if the page has 0 refcount it means it
524 * was concurrently deleted from pagecache so try the deref
525 * again. Fortunately there is already a requirement for logic
526 * to retry the entire slot lookup -- the indirect pointer
527 * problem (replacing direct root node with an indirect pointer
528 * also results in a stale slot). So tag the slot as indirect
529 * to force callers to retry.
532 if (!radix_tree_is_internal_node(child
)) {
533 node
->slots
[0] = (void __rcu
*)RADIX_TREE_RETRY
;
536 WARN_ON_ONCE(!list_empty(&node
->private_list
));
537 radix_tree_node_free(node
);
544 static bool delete_node(struct radix_tree_root
*root
,
545 struct radix_tree_node
*node
)
547 bool deleted
= false;
550 struct radix_tree_node
*parent
;
553 if (node_to_entry(node
) ==
554 rcu_dereference_raw(root
->xa_head
))
555 deleted
|= radix_tree_shrink(root
);
559 parent
= node
->parent
;
561 parent
->slots
[node
->offset
] = NULL
;
565 * Shouldn't the tags already have all been cleared
569 root_tag_clear_all(root
);
570 root
->xa_head
= NULL
;
573 WARN_ON_ONCE(!list_empty(&node
->private_list
));
574 radix_tree_node_free(node
);
584 * __radix_tree_create - create a slot in a radix tree
585 * @root: radix tree root
587 * @nodep: returns node
588 * @slotp: returns slot
590 * Create, if necessary, and return the node and slot for an item
591 * at position @index in the radix tree @root.
593 * Until there is more than one item in the tree, no nodes are
594 * allocated and @root->xa_head is used as a direct slot instead of
595 * pointing to a node, in which case *@nodep will be NULL.
597 * Returns -ENOMEM, or 0 for success.
599 static int __radix_tree_create(struct radix_tree_root
*root
,
600 unsigned long index
, struct radix_tree_node
**nodep
,
603 struct radix_tree_node
*node
= NULL
, *child
;
604 void __rcu
**slot
= (void __rcu
**)&root
->xa_head
;
605 unsigned long maxindex
;
606 unsigned int shift
, offset
= 0;
607 unsigned long max
= index
;
608 gfp_t gfp
= root_gfp_mask(root
);
610 shift
= radix_tree_load_root(root
, &child
, &maxindex
);
612 /* Make sure the tree is high enough. */
613 if (max
> maxindex
) {
614 int error
= radix_tree_extend(root
, gfp
, max
, shift
);
618 child
= rcu_dereference_raw(root
->xa_head
);
622 shift
-= RADIX_TREE_MAP_SHIFT
;
624 /* Have to add a child node. */
625 child
= radix_tree_node_alloc(gfp
, node
, root
, shift
,
629 rcu_assign_pointer(*slot
, node_to_entry(child
));
632 } else if (!radix_tree_is_internal_node(child
))
635 /* Go a level down */
636 node
= entry_to_node(child
);
637 offset
= radix_tree_descend(node
, &child
, index
);
638 slot
= &node
->slots
[offset
];
649 * Free any nodes below this node. The tree is presumed to not need
650 * shrinking, and any user data in the tree is presumed to not need a
651 * destructor called on it. If we need to add a destructor, we can
652 * add that functionality later. Note that we may not clear tags or
653 * slots from the tree as an RCU walker may still have a pointer into
654 * this subtree. We could replace the entries with RADIX_TREE_RETRY,
655 * but we'll still have to clear those in rcu_free.
657 static void radix_tree_free_nodes(struct radix_tree_node
*node
)
660 struct radix_tree_node
*child
= entry_to_node(node
);
663 void *entry
= rcu_dereference_raw(child
->slots
[offset
]);
664 if (xa_is_node(entry
) && child
->shift
) {
665 child
= entry_to_node(entry
);
670 while (offset
== RADIX_TREE_MAP_SIZE
) {
671 struct radix_tree_node
*old
= child
;
672 offset
= child
->offset
+ 1;
673 child
= child
->parent
;
674 WARN_ON_ONCE(!list_empty(&old
->private_list
));
675 radix_tree_node_free(old
);
676 if (old
== entry_to_node(node
))
682 static inline int insert_entries(struct radix_tree_node
*node
,
683 void __rcu
**slot
, void *item
, bool replace
)
687 rcu_assign_pointer(*slot
, item
);
690 if (xa_is_value(item
))
697 * __radix_tree_insert - insert into a radix tree
698 * @root: radix tree root
700 * @item: item to insert
702 * Insert an item into the radix tree at position @index.
704 int radix_tree_insert(struct radix_tree_root
*root
, unsigned long index
,
707 struct radix_tree_node
*node
;
711 BUG_ON(radix_tree_is_internal_node(item
));
713 error
= __radix_tree_create(root
, index
, &node
, &slot
);
717 error
= insert_entries(node
, slot
, item
, false);
722 unsigned offset
= get_slot_offset(node
, slot
);
723 BUG_ON(tag_get(node
, 0, offset
));
724 BUG_ON(tag_get(node
, 1, offset
));
725 BUG_ON(tag_get(node
, 2, offset
));
727 BUG_ON(root_tags_get(root
));
732 EXPORT_SYMBOL(radix_tree_insert
);
735 * __radix_tree_lookup - lookup an item in a radix tree
736 * @root: radix tree root
738 * @nodep: returns node
739 * @slotp: returns slot
741 * Lookup and return the item at position @index in the radix
744 * Until there is more than one item in the tree, no nodes are
745 * allocated and @root->xa_head is used as a direct slot instead of
746 * pointing to a node, in which case *@nodep will be NULL.
748 void *__radix_tree_lookup(const struct radix_tree_root
*root
,
749 unsigned long index
, struct radix_tree_node
**nodep
,
752 struct radix_tree_node
*node
, *parent
;
753 unsigned long maxindex
;
758 slot
= (void __rcu
**)&root
->xa_head
;
759 radix_tree_load_root(root
, &node
, &maxindex
);
760 if (index
> maxindex
)
763 while (radix_tree_is_internal_node(node
)) {
766 parent
= entry_to_node(node
);
767 offset
= radix_tree_descend(parent
, &node
, index
);
768 slot
= parent
->slots
+ offset
;
769 if (node
== RADIX_TREE_RETRY
)
771 if (parent
->shift
== 0)
783 * radix_tree_lookup_slot - lookup a slot in a radix tree
784 * @root: radix tree root
787 * Returns: the slot corresponding to the position @index in the
788 * radix tree @root. This is useful for update-if-exists operations.
790 * This function can be called under rcu_read_lock iff the slot is not
791 * modified by radix_tree_replace_slot, otherwise it must be called
792 * exclusive from other writers. Any dereference of the slot must be done
793 * using radix_tree_deref_slot.
795 void __rcu
**radix_tree_lookup_slot(const struct radix_tree_root
*root
,
800 if (!__radix_tree_lookup(root
, index
, NULL
, &slot
))
804 EXPORT_SYMBOL(radix_tree_lookup_slot
);
807 * radix_tree_lookup - perform lookup operation on a radix tree
808 * @root: radix tree root
811 * Lookup the item at the position @index in the radix tree @root.
813 * This function can be called under rcu_read_lock, however the caller
814 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
815 * them safely). No RCU barriers are required to access or modify the
816 * returned item, however.
818 void *radix_tree_lookup(const struct radix_tree_root
*root
, unsigned long index
)
820 return __radix_tree_lookup(root
, index
, NULL
, NULL
);
822 EXPORT_SYMBOL(radix_tree_lookup
);
824 static void replace_slot(void __rcu
**slot
, void *item
,
825 struct radix_tree_node
*node
, int count
, int values
)
827 if (node
&& (count
|| values
)) {
828 node
->count
+= count
;
829 node
->nr_values
+= values
;
832 rcu_assign_pointer(*slot
, item
);
835 static bool node_tag_get(const struct radix_tree_root
*root
,
836 const struct radix_tree_node
*node
,
837 unsigned int tag
, unsigned int offset
)
840 return tag_get(node
, tag
, offset
);
841 return root_tag_get(root
, tag
);
845 * IDR users want to be able to store NULL in the tree, so if the slot isn't
846 * free, don't adjust the count, even if it's transitioning between NULL and
847 * non-NULL. For the IDA, we mark slots as being IDR_FREE while they still
848 * have empty bits, but it only stores NULL in slots when they're being
851 static int calculate_count(struct radix_tree_root
*root
,
852 struct radix_tree_node
*node
, void __rcu
**slot
,
853 void *item
, void *old
)
856 unsigned offset
= get_slot_offset(node
, slot
);
857 bool free
= node_tag_get(root
, node
, IDR_FREE
, offset
);
863 return !!item
- !!old
;
867 * __radix_tree_replace - replace item in a slot
868 * @root: radix tree root
869 * @node: pointer to tree node
870 * @slot: pointer to slot in @node
871 * @item: new item to store in the slot.
873 * For use with __radix_tree_lookup(). Caller must hold tree write locked
874 * across slot lookup and replacement.
876 void __radix_tree_replace(struct radix_tree_root
*root
,
877 struct radix_tree_node
*node
,
878 void __rcu
**slot
, void *item
)
880 void *old
= rcu_dereference_raw(*slot
);
881 int values
= !!xa_is_value(item
) - !!xa_is_value(old
);
882 int count
= calculate_count(root
, node
, slot
, item
, old
);
885 * This function supports replacing value entries and
886 * deleting entries, but that needs accounting against the
887 * node unless the slot is root->xa_head.
889 WARN_ON_ONCE(!node
&& (slot
!= (void __rcu
**)&root
->xa_head
) &&
891 replace_slot(slot
, item
, node
, count
, values
);
896 delete_node(root
, node
);
900 * radix_tree_replace_slot - replace item in a slot
901 * @root: radix tree root
902 * @slot: pointer to slot
903 * @item: new item to store in the slot.
905 * For use with radix_tree_lookup_slot() and
906 * radix_tree_gang_lookup_tag_slot(). Caller must hold tree write locked
907 * across slot lookup and replacement.
909 * NOTE: This cannot be used to switch between non-entries (empty slots),
910 * regular entries, and value entries, as that requires accounting
911 * inside the radix tree node. When switching from one type of entry or
912 * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
913 * radix_tree_iter_replace().
915 void radix_tree_replace_slot(struct radix_tree_root
*root
,
916 void __rcu
**slot
, void *item
)
918 __radix_tree_replace(root
, NULL
, slot
, item
);
920 EXPORT_SYMBOL(radix_tree_replace_slot
);
923 * radix_tree_iter_replace - replace item in a slot
924 * @root: radix tree root
925 * @slot: pointer to slot
926 * @item: new item to store in the slot.
928 * For use with radix_tree_for_each_slot().
929 * Caller must hold tree write locked.
931 void radix_tree_iter_replace(struct radix_tree_root
*root
,
932 const struct radix_tree_iter
*iter
,
933 void __rcu
**slot
, void *item
)
935 __radix_tree_replace(root
, iter
->node
, slot
, item
);
938 static void node_tag_set(struct radix_tree_root
*root
,
939 struct radix_tree_node
*node
,
940 unsigned int tag
, unsigned int offset
)
943 if (tag_get(node
, tag
, offset
))
945 tag_set(node
, tag
, offset
);
946 offset
= node
->offset
;
950 if (!root_tag_get(root
, tag
))
951 root_tag_set(root
, tag
);
955 * radix_tree_tag_set - set a tag on a radix tree node
956 * @root: radix tree root
960 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
961 * corresponding to @index in the radix tree. From
962 * the root all the way down to the leaf node.
964 * Returns the address of the tagged item. Setting a tag on a not-present
967 void *radix_tree_tag_set(struct radix_tree_root
*root
,
968 unsigned long index
, unsigned int tag
)
970 struct radix_tree_node
*node
, *parent
;
971 unsigned long maxindex
;
973 radix_tree_load_root(root
, &node
, &maxindex
);
974 BUG_ON(index
> maxindex
);
976 while (radix_tree_is_internal_node(node
)) {
979 parent
= entry_to_node(node
);
980 offset
= radix_tree_descend(parent
, &node
, index
);
983 if (!tag_get(parent
, tag
, offset
))
984 tag_set(parent
, tag
, offset
);
987 /* set the root's tag bit */
988 if (!root_tag_get(root
, tag
))
989 root_tag_set(root
, tag
);
993 EXPORT_SYMBOL(radix_tree_tag_set
);
995 static void node_tag_clear(struct radix_tree_root
*root
,
996 struct radix_tree_node
*node
,
997 unsigned int tag
, unsigned int offset
)
1000 if (!tag_get(node
, tag
, offset
))
1002 tag_clear(node
, tag
, offset
);
1003 if (any_tag_set(node
, tag
))
1006 offset
= node
->offset
;
1007 node
= node
->parent
;
1010 /* clear the root's tag bit */
1011 if (root_tag_get(root
, tag
))
1012 root_tag_clear(root
, tag
);
1016 * radix_tree_tag_clear - clear a tag on a radix tree node
1017 * @root: radix tree root
1021 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1022 * corresponding to @index in the radix tree. If this causes
1023 * the leaf node to have no tags set then clear the tag in the
1024 * next-to-leaf node, etc.
1026 * Returns the address of the tagged item on success, else NULL. ie:
1027 * has the same return value and semantics as radix_tree_lookup().
1029 void *radix_tree_tag_clear(struct radix_tree_root
*root
,
1030 unsigned long index
, unsigned int tag
)
1032 struct radix_tree_node
*node
, *parent
;
1033 unsigned long maxindex
;
1034 int uninitialized_var(offset
);
1036 radix_tree_load_root(root
, &node
, &maxindex
);
1037 if (index
> maxindex
)
1042 while (radix_tree_is_internal_node(node
)) {
1043 parent
= entry_to_node(node
);
1044 offset
= radix_tree_descend(parent
, &node
, index
);
1048 node_tag_clear(root
, parent
, tag
, offset
);
1052 EXPORT_SYMBOL(radix_tree_tag_clear
);
1055 * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1056 * @root: radix tree root
1057 * @iter: iterator state
1058 * @tag: tag to clear
1060 void radix_tree_iter_tag_clear(struct radix_tree_root
*root
,
1061 const struct radix_tree_iter
*iter
, unsigned int tag
)
1063 node_tag_clear(root
, iter
->node
, tag
, iter_offset(iter
));
1067 * radix_tree_tag_get - get a tag on a radix tree node
1068 * @root: radix tree root
1070 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
1074 * 0: tag not present or not set
1077 * Note that the return value of this function may not be relied on, even if
1078 * the RCU lock is held, unless tag modification and node deletion are excluded
1081 int radix_tree_tag_get(const struct radix_tree_root
*root
,
1082 unsigned long index
, unsigned int tag
)
1084 struct radix_tree_node
*node
, *parent
;
1085 unsigned long maxindex
;
1087 if (!root_tag_get(root
, tag
))
1090 radix_tree_load_root(root
, &node
, &maxindex
);
1091 if (index
> maxindex
)
1094 while (radix_tree_is_internal_node(node
)) {
1097 parent
= entry_to_node(node
);
1098 offset
= radix_tree_descend(parent
, &node
, index
);
1100 if (!tag_get(parent
, tag
, offset
))
1102 if (node
== RADIX_TREE_RETRY
)
1108 EXPORT_SYMBOL(radix_tree_tag_get
);
1110 /* Construct iter->tags bit-mask from node->tags[tag] array */
1111 static void set_iter_tags(struct radix_tree_iter
*iter
,
1112 struct radix_tree_node
*node
, unsigned offset
,
1115 unsigned tag_long
= offset
/ BITS_PER_LONG
;
1116 unsigned tag_bit
= offset
% BITS_PER_LONG
;
1123 iter
->tags
= node
->tags
[tag
][tag_long
] >> tag_bit
;
1125 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1126 if (tag_long
< RADIX_TREE_TAG_LONGS
- 1) {
1127 /* Pick tags from next element */
1129 iter
->tags
|= node
->tags
[tag
][tag_long
+ 1] <<
1130 (BITS_PER_LONG
- tag_bit
);
1131 /* Clip chunk size, here only BITS_PER_LONG tags */
1132 iter
->next_index
= __radix_tree_iter_add(iter
, BITS_PER_LONG
);
1136 void __rcu
**radix_tree_iter_resume(void __rcu
**slot
,
1137 struct radix_tree_iter
*iter
)
1140 iter
->index
= __radix_tree_iter_add(iter
, 1);
1141 iter
->next_index
= iter
->index
;
1145 EXPORT_SYMBOL(radix_tree_iter_resume
);
1148 * radix_tree_next_chunk - find next chunk of slots for iteration
1150 * @root: radix tree root
1151 * @iter: iterator state
1152 * @flags: RADIX_TREE_ITER_* flags and tag index
1153 * Returns: pointer to chunk first slot, or NULL if iteration is over
1155 void __rcu
**radix_tree_next_chunk(const struct radix_tree_root
*root
,
1156 struct radix_tree_iter
*iter
, unsigned flags
)
1158 unsigned tag
= flags
& RADIX_TREE_ITER_TAG_MASK
;
1159 struct radix_tree_node
*node
, *child
;
1160 unsigned long index
, offset
, maxindex
;
1162 if ((flags
& RADIX_TREE_ITER_TAGGED
) && !root_tag_get(root
, tag
))
1166 * Catch next_index overflow after ~0UL. iter->index never overflows
1167 * during iterating; it can be zero only at the beginning.
1168 * And we cannot overflow iter->next_index in a single step,
1169 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1171 * This condition also used by radix_tree_next_slot() to stop
1172 * contiguous iterating, and forbid switching to the next chunk.
1174 index
= iter
->next_index
;
1175 if (!index
&& iter
->index
)
1179 radix_tree_load_root(root
, &child
, &maxindex
);
1180 if (index
> maxindex
)
1185 if (!radix_tree_is_internal_node(child
)) {
1186 /* Single-slot tree */
1187 iter
->index
= index
;
1188 iter
->next_index
= maxindex
+ 1;
1191 return (void __rcu
**)&root
->xa_head
;
1195 node
= entry_to_node(child
);
1196 offset
= radix_tree_descend(node
, &child
, index
);
1198 if ((flags
& RADIX_TREE_ITER_TAGGED
) ?
1199 !tag_get(node
, tag
, offset
) : !child
) {
1201 if (flags
& RADIX_TREE_ITER_CONTIG
)
1204 if (flags
& RADIX_TREE_ITER_TAGGED
)
1205 offset
= radix_tree_find_next_bit(node
, tag
,
1208 while (++offset
< RADIX_TREE_MAP_SIZE
) {
1209 void *slot
= rcu_dereference_raw(
1210 node
->slots
[offset
]);
1214 index
&= ~node_maxindex(node
);
1215 index
+= offset
<< node
->shift
;
1216 /* Overflow after ~0UL */
1219 if (offset
== RADIX_TREE_MAP_SIZE
)
1221 child
= rcu_dereference_raw(node
->slots
[offset
]);
1226 if (child
== RADIX_TREE_RETRY
)
1228 } while (node
->shift
&& radix_tree_is_internal_node(child
));
1230 /* Update the iterator state */
1231 iter
->index
= (index
&~ node_maxindex(node
)) | offset
;
1232 iter
->next_index
= (index
| node_maxindex(node
)) + 1;
1235 if (flags
& RADIX_TREE_ITER_TAGGED
)
1236 set_iter_tags(iter
, node
, offset
, tag
);
1238 return node
->slots
+ offset
;
1240 EXPORT_SYMBOL(radix_tree_next_chunk
);
1243 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1244 * @root: radix tree root
1245 * @results: where the results of the lookup are placed
1246 * @first_index: start the lookup from this key
1247 * @max_items: place up to this many items at *results
1249 * Performs an index-ascending scan of the tree for present items. Places
1250 * them at *@results and returns the number of items which were placed at
1253 * The implementation is naive.
1255 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1256 * rcu_read_lock. In this case, rather than the returned results being
1257 * an atomic snapshot of the tree at a single point in time, the
1258 * semantics of an RCU protected gang lookup are as though multiple
1259 * radix_tree_lookups have been issued in individual locks, and results
1260 * stored in 'results'.
1263 radix_tree_gang_lookup(const struct radix_tree_root
*root
, void **results
,
1264 unsigned long first_index
, unsigned int max_items
)
1266 struct radix_tree_iter iter
;
1268 unsigned int ret
= 0;
1270 if (unlikely(!max_items
))
1273 radix_tree_for_each_slot(slot
, root
, &iter
, first_index
) {
1274 results
[ret
] = rcu_dereference_raw(*slot
);
1277 if (radix_tree_is_internal_node(results
[ret
])) {
1278 slot
= radix_tree_iter_retry(&iter
);
1281 if (++ret
== max_items
)
1287 EXPORT_SYMBOL(radix_tree_gang_lookup
);
1290 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1292 * @root: radix tree root
1293 * @results: where the results of the lookup are placed
1294 * @first_index: start the lookup from this key
1295 * @max_items: place up to this many items at *results
1296 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1298 * Performs an index-ascending scan of the tree for present items which
1299 * have the tag indexed by @tag set. Places the items at *@results and
1300 * returns the number of items which were placed at *@results.
1303 radix_tree_gang_lookup_tag(const struct radix_tree_root
*root
, void **results
,
1304 unsigned long first_index
, unsigned int max_items
,
1307 struct radix_tree_iter iter
;
1309 unsigned int ret
= 0;
1311 if (unlikely(!max_items
))
1314 radix_tree_for_each_tagged(slot
, root
, &iter
, first_index
, tag
) {
1315 results
[ret
] = rcu_dereference_raw(*slot
);
1318 if (radix_tree_is_internal_node(results
[ret
])) {
1319 slot
= radix_tree_iter_retry(&iter
);
1322 if (++ret
== max_items
)
1328 EXPORT_SYMBOL(radix_tree_gang_lookup_tag
);
1331 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1332 * radix tree based on a tag
1333 * @root: radix tree root
1334 * @results: where the results of the lookup are placed
1335 * @first_index: start the lookup from this key
1336 * @max_items: place up to this many items at *results
1337 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1339 * Performs an index-ascending scan of the tree for present items which
1340 * have the tag indexed by @tag set. Places the slots at *@results and
1341 * returns the number of slots which were placed at *@results.
1344 radix_tree_gang_lookup_tag_slot(const struct radix_tree_root
*root
,
1345 void __rcu
***results
, unsigned long first_index
,
1346 unsigned int max_items
, unsigned int tag
)
1348 struct radix_tree_iter iter
;
1350 unsigned int ret
= 0;
1352 if (unlikely(!max_items
))
1355 radix_tree_for_each_tagged(slot
, root
, &iter
, first_index
, tag
) {
1356 results
[ret
] = slot
;
1357 if (++ret
== max_items
)
1363 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot
);
1365 static bool __radix_tree_delete(struct radix_tree_root
*root
,
1366 struct radix_tree_node
*node
, void __rcu
**slot
)
1368 void *old
= rcu_dereference_raw(*slot
);
1369 int values
= xa_is_value(old
) ? -1 : 0;
1370 unsigned offset
= get_slot_offset(node
, slot
);
1374 node_tag_set(root
, node
, IDR_FREE
, offset
);
1376 for (tag
= 0; tag
< RADIX_TREE_MAX_TAGS
; tag
++)
1377 node_tag_clear(root
, node
, tag
, offset
);
1379 replace_slot(slot
, NULL
, node
, -1, values
);
1380 return node
&& delete_node(root
, node
);
1384 * radix_tree_iter_delete - delete the entry at this iterator position
1385 * @root: radix tree root
1386 * @iter: iterator state
1387 * @slot: pointer to slot
1389 * Delete the entry at the position currently pointed to by the iterator.
1390 * This may result in the current node being freed; if it is, the iterator
1391 * is advanced so that it will not reference the freed memory. This
1392 * function may be called without any locking if there are no other threads
1393 * which can access this tree.
1395 void radix_tree_iter_delete(struct radix_tree_root
*root
,
1396 struct radix_tree_iter
*iter
, void __rcu
**slot
)
1398 if (__radix_tree_delete(root
, iter
->node
, slot
))
1399 iter
->index
= iter
->next_index
;
1401 EXPORT_SYMBOL(radix_tree_iter_delete
);
1404 * radix_tree_delete_item - delete an item from a radix tree
1405 * @root: radix tree root
1407 * @item: expected item
1409 * Remove @item at @index from the radix tree rooted at @root.
1411 * Return: the deleted entry, or %NULL if it was not present
1412 * or the entry at the given @index was not @item.
1414 void *radix_tree_delete_item(struct radix_tree_root
*root
,
1415 unsigned long index
, void *item
)
1417 struct radix_tree_node
*node
= NULL
;
1418 void __rcu
**slot
= NULL
;
1421 entry
= __radix_tree_lookup(root
, index
, &node
, &slot
);
1424 if (!entry
&& (!is_idr(root
) || node_tag_get(root
, node
, IDR_FREE
,
1425 get_slot_offset(node
, slot
))))
1428 if (item
&& entry
!= item
)
1431 __radix_tree_delete(root
, node
, slot
);
1435 EXPORT_SYMBOL(radix_tree_delete_item
);
1438 * radix_tree_delete - delete an entry from a radix tree
1439 * @root: radix tree root
1442 * Remove the entry at @index from the radix tree rooted at @root.
1444 * Return: The deleted entry, or %NULL if it was not present.
1446 void *radix_tree_delete(struct radix_tree_root
*root
, unsigned long index
)
1448 return radix_tree_delete_item(root
, index
, NULL
);
1450 EXPORT_SYMBOL(radix_tree_delete
);
1453 * radix_tree_tagged - test whether any items in the tree are tagged
1454 * @root: radix tree root
1457 int radix_tree_tagged(const struct radix_tree_root
*root
, unsigned int tag
)
1459 return root_tag_get(root
, tag
);
1461 EXPORT_SYMBOL(radix_tree_tagged
);
1464 * idr_preload - preload for idr_alloc()
1465 * @gfp_mask: allocation mask to use for preloading
1467 * Preallocate memory to use for the next call to idr_alloc(). This function
1468 * returns with preemption disabled. It will be enabled by idr_preload_end().
1470 void idr_preload(gfp_t gfp_mask
)
1472 if (__radix_tree_preload(gfp_mask
, IDR_PRELOAD_SIZE
))
1475 EXPORT_SYMBOL(idr_preload
);
1477 void __rcu
**idr_get_free(struct radix_tree_root
*root
,
1478 struct radix_tree_iter
*iter
, gfp_t gfp
,
1481 struct radix_tree_node
*node
= NULL
, *child
;
1482 void __rcu
**slot
= (void __rcu
**)&root
->xa_head
;
1483 unsigned long maxindex
, start
= iter
->next_index
;
1484 unsigned int shift
, offset
= 0;
1487 shift
= radix_tree_load_root(root
, &child
, &maxindex
);
1488 if (!radix_tree_tagged(root
, IDR_FREE
))
1489 start
= max(start
, maxindex
+ 1);
1491 return ERR_PTR(-ENOSPC
);
1493 if (start
> maxindex
) {
1494 int error
= radix_tree_extend(root
, gfp
, start
, shift
);
1496 return ERR_PTR(error
);
1498 child
= rcu_dereference_raw(root
->xa_head
);
1500 if (start
== 0 && shift
== 0)
1501 shift
= RADIX_TREE_MAP_SHIFT
;
1504 shift
-= RADIX_TREE_MAP_SHIFT
;
1505 if (child
== NULL
) {
1506 /* Have to add a child node. */
1507 child
= radix_tree_node_alloc(gfp
, node
, root
, shift
,
1510 return ERR_PTR(-ENOMEM
);
1511 all_tag_set(child
, IDR_FREE
);
1512 rcu_assign_pointer(*slot
, node_to_entry(child
));
1515 } else if (!radix_tree_is_internal_node(child
))
1518 node
= entry_to_node(child
);
1519 offset
= radix_tree_descend(node
, &child
, start
);
1520 if (!tag_get(node
, IDR_FREE
, offset
)) {
1521 offset
= radix_tree_find_next_bit(node
, IDR_FREE
,
1523 start
= next_index(start
, node
, offset
);
1524 if (start
> max
|| start
== 0)
1525 return ERR_PTR(-ENOSPC
);
1526 while (offset
== RADIX_TREE_MAP_SIZE
) {
1527 offset
= node
->offset
+ 1;
1528 node
= node
->parent
;
1531 shift
= node
->shift
;
1533 child
= rcu_dereference_raw(node
->slots
[offset
]);
1535 slot
= &node
->slots
[offset
];
1538 iter
->index
= start
;
1540 iter
->next_index
= 1 + min(max
, (start
| node_maxindex(node
)));
1542 iter
->next_index
= 1;
1544 set_iter_tags(iter
, node
, offset
, IDR_FREE
);
1550 * idr_destroy - release all internal memory from an IDR
1553 * After this function is called, the IDR is empty, and may be reused or
1554 * the data structure containing it may be freed.
1556 * A typical clean-up sequence for objects stored in an idr tree will use
1557 * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1558 * free the memory used to keep track of those objects.
1560 void idr_destroy(struct idr
*idr
)
1562 struct radix_tree_node
*node
= rcu_dereference_raw(idr
->idr_rt
.xa_head
);
1563 if (radix_tree_is_internal_node(node
))
1564 radix_tree_free_nodes(node
);
1565 idr
->idr_rt
.xa_head
= NULL
;
1566 root_tag_set(&idr
->idr_rt
, IDR_FREE
);
1568 EXPORT_SYMBOL(idr_destroy
);
1571 radix_tree_node_ctor(void *arg
)
1573 struct radix_tree_node
*node
= arg
;
1575 memset(node
, 0, sizeof(*node
));
1576 INIT_LIST_HEAD(&node
->private_list
);
1579 static int radix_tree_cpu_dead(unsigned int cpu
)
1581 struct radix_tree_preload
*rtp
;
1582 struct radix_tree_node
*node
;
1584 /* Free per-cpu pool of preloaded nodes */
1585 rtp
= &per_cpu(radix_tree_preloads
, cpu
);
1588 rtp
->nodes
= node
->parent
;
1589 kmem_cache_free(radix_tree_node_cachep
, node
);
1595 void __init
radix_tree_init(void)
1599 BUILD_BUG_ON(RADIX_TREE_MAX_TAGS
+ __GFP_BITS_SHIFT
> 32);
1600 BUILD_BUG_ON(ROOT_IS_IDR
& ~GFP_ZONEMASK
);
1601 BUILD_BUG_ON(XA_CHUNK_SIZE
> 255);
1602 radix_tree_node_cachep
= kmem_cache_create("radix_tree_node",
1603 sizeof(struct radix_tree_node
), 0,
1604 SLAB_PANIC
| SLAB_RECLAIM_ACCOUNT
,
1605 radix_tree_node_ctor
);
1606 ret
= cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD
, "lib/radix:dead",
1607 NULL
, radix_tree_cpu_dead
);