Loading...
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
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
10 */
11
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>
29
30/*
31 * Radix tree node cache.
32 */
33struct kmem_cache *radix_tree_node_cachep;
34
35/*
36 * The radix tree is variable-height, so an insert operation not only has
37 * to build the branch to its corresponding item, it also has to build the
38 * branch to existing items if the size has to be increased (by
39 * radix_tree_extend).
40 *
41 * The worst case is a zero height tree with just a single item at index 0,
42 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
43 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
44 * Hence:
45 */
46#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
47
48/*
49 * The IDR does not have to be as high as the radix tree since it uses
50 * signed integers, not unsigned longs.
51 */
52#define IDR_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(int) - 1)
53#define IDR_MAX_PATH (DIV_ROUND_UP(IDR_INDEX_BITS, \
54 RADIX_TREE_MAP_SHIFT))
55#define IDR_PRELOAD_SIZE (IDR_MAX_PATH * 2 - 1)
56
57/*
58 * Per-cpu pool of preloaded nodes
59 */
60DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = {
61 .lock = INIT_LOCAL_LOCK(lock),
62};
63EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads);
64
65static inline struct radix_tree_node *entry_to_node(void *ptr)
66{
67 return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
68}
69
70static inline void *node_to_entry(void *ptr)
71{
72 return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
73}
74
75#define RADIX_TREE_RETRY XA_RETRY_ENTRY
76
77static inline unsigned long
78get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
79{
80 return parent ? slot - parent->slots : 0;
81}
82
83static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
84 struct radix_tree_node **nodep, unsigned long index)
85{
86 unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
87 void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
88
89 *nodep = (void *)entry;
90 return offset;
91}
92
93static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
94{
95 return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
96}
97
98static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
99 int offset)
100{
101 __set_bit(offset, node->tags[tag]);
102}
103
104static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
105 int offset)
106{
107 __clear_bit(offset, node->tags[tag]);
108}
109
110static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
111 int offset)
112{
113 return test_bit(offset, node->tags[tag]);
114}
115
116static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
117{
118 root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
119}
120
121static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
122{
123 root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
124}
125
126static inline void root_tag_clear_all(struct radix_tree_root *root)
127{
128 root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
129}
130
131static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
132{
133 return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
134}
135
136static inline unsigned root_tags_get(const struct radix_tree_root *root)
137{
138 return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
139}
140
141static inline bool is_idr(const struct radix_tree_root *root)
142{
143 return !!(root->xa_flags & ROOT_IS_IDR);
144}
145
146/*
147 * Returns 1 if any slot in the node has this tag set.
148 * Otherwise returns 0.
149 */
150static inline int any_tag_set(const struct radix_tree_node *node,
151 unsigned int tag)
152{
153 unsigned idx;
154 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
155 if (node->tags[tag][idx])
156 return 1;
157 }
158 return 0;
159}
160
161static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
162{
163 bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
164}
165
166/**
167 * radix_tree_find_next_bit - find the next set bit in a memory region
168 *
169 * @node: where to begin the search
170 * @tag: the tag index
171 * @offset: the bitnumber to start searching at
172 *
173 * Unrollable variant of find_next_bit() for constant size arrays.
174 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
175 * Returns next bit offset, or size if nothing found.
176 */
177static __always_inline unsigned long
178radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
179 unsigned long offset)
180{
181 const unsigned long *addr = node->tags[tag];
182
183 if (offset < RADIX_TREE_MAP_SIZE) {
184 unsigned long tmp;
185
186 addr += offset / BITS_PER_LONG;
187 tmp = *addr >> (offset % BITS_PER_LONG);
188 if (tmp)
189 return __ffs(tmp) + offset;
190 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
191 while (offset < RADIX_TREE_MAP_SIZE) {
192 tmp = *++addr;
193 if (tmp)
194 return __ffs(tmp) + offset;
195 offset += BITS_PER_LONG;
196 }
197 }
198 return RADIX_TREE_MAP_SIZE;
199}
200
201static unsigned int iter_offset(const struct radix_tree_iter *iter)
202{
203 return iter->index & RADIX_TREE_MAP_MASK;
204}
205
206/*
207 * The maximum index which can be stored in a radix tree
208 */
209static inline unsigned long shift_maxindex(unsigned int shift)
210{
211 return (RADIX_TREE_MAP_SIZE << shift) - 1;
212}
213
214static inline unsigned long node_maxindex(const struct radix_tree_node *node)
215{
216 return shift_maxindex(node->shift);
217}
218
219static unsigned long next_index(unsigned long index,
220 const struct radix_tree_node *node,
221 unsigned long offset)
222{
223 return (index & ~node_maxindex(node)) + (offset << node->shift);
224}
225
226/*
227 * This assumes that the caller has performed appropriate preallocation, and
228 * that the caller has pinned this thread of control to the current CPU.
229 */
230static struct radix_tree_node *
231radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
232 struct radix_tree_root *root,
233 unsigned int shift, unsigned int offset,
234 unsigned int count, unsigned int nr_values)
235{
236 struct radix_tree_node *ret = NULL;
237
238 /*
239 * Preload code isn't irq safe and it doesn't make sense to use
240 * preloading during an interrupt anyway as all the allocations have
241 * to be atomic. So just do normal allocation when in interrupt.
242 */
243 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
244 struct radix_tree_preload *rtp;
245
246 /*
247 * Even if the caller has preloaded, try to allocate from the
248 * cache first for the new node to get accounted to the memory
249 * cgroup.
250 */
251 ret = kmem_cache_alloc(radix_tree_node_cachep,
252 gfp_mask | __GFP_NOWARN);
253 if (ret)
254 goto out;
255
256 /*
257 * Provided the caller has preloaded here, we will always
258 * succeed in getting a node here (and never reach
259 * kmem_cache_alloc)
260 */
261 rtp = this_cpu_ptr(&radix_tree_preloads);
262 if (rtp->nr) {
263 ret = rtp->nodes;
264 rtp->nodes = ret->parent;
265 rtp->nr--;
266 }
267 /*
268 * Update the allocation stack trace as this is more useful
269 * for debugging.
270 */
271 kmemleak_update_trace(ret);
272 goto out;
273 }
274 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
275out:
276 BUG_ON(radix_tree_is_internal_node(ret));
277 if (ret) {
278 ret->shift = shift;
279 ret->offset = offset;
280 ret->count = count;
281 ret->nr_values = nr_values;
282 ret->parent = parent;
283 ret->array = root;
284 }
285 return ret;
286}
287
288void radix_tree_node_rcu_free(struct rcu_head *head)
289{
290 struct radix_tree_node *node =
291 container_of(head, struct radix_tree_node, rcu_head);
292
293 /*
294 * Must only free zeroed nodes into the slab. We can be left with
295 * non-NULL entries by radix_tree_free_nodes, so clear the entries
296 * and tags here.
297 */
298 memset(node->slots, 0, sizeof(node->slots));
299 memset(node->tags, 0, sizeof(node->tags));
300 INIT_LIST_HEAD(&node->private_list);
301
302 kmem_cache_free(radix_tree_node_cachep, node);
303}
304
305static inline void
306radix_tree_node_free(struct radix_tree_node *node)
307{
308 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
309}
310
311/*
312 * Load up this CPU's radix_tree_node buffer with sufficient objects to
313 * ensure that the addition of a single element in the tree cannot fail. On
314 * success, return zero, with preemption disabled. On error, return -ENOMEM
315 * with preemption not disabled.
316 *
317 * To make use of this facility, the radix tree must be initialised without
318 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
319 */
320static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
321{
322 struct radix_tree_preload *rtp;
323 struct radix_tree_node *node;
324 int ret = -ENOMEM;
325
326 /*
327 * Nodes preloaded by one cgroup can be used by another cgroup, so
328 * they should never be accounted to any particular memory cgroup.
329 */
330 gfp_mask &= ~__GFP_ACCOUNT;
331
332 local_lock(&radix_tree_preloads.lock);
333 rtp = this_cpu_ptr(&radix_tree_preloads);
334 while (rtp->nr < nr) {
335 local_unlock(&radix_tree_preloads.lock);
336 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
337 if (node == NULL)
338 goto out;
339 local_lock(&radix_tree_preloads.lock);
340 rtp = this_cpu_ptr(&radix_tree_preloads);
341 if (rtp->nr < nr) {
342 node->parent = rtp->nodes;
343 rtp->nodes = node;
344 rtp->nr++;
345 } else {
346 kmem_cache_free(radix_tree_node_cachep, node);
347 }
348 }
349 ret = 0;
350out:
351 return ret;
352}
353
354/*
355 * Load up this CPU's radix_tree_node buffer with sufficient objects to
356 * ensure that the addition of a single element in the tree cannot fail. On
357 * success, return zero, with preemption disabled. On error, return -ENOMEM
358 * with preemption not disabled.
359 *
360 * To make use of this facility, the radix tree must be initialised without
361 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
362 */
363int radix_tree_preload(gfp_t gfp_mask)
364{
365 /* Warn on non-sensical use... */
366 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
367 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
368}
369EXPORT_SYMBOL(radix_tree_preload);
370
371/*
372 * The same as above function, except we don't guarantee preloading happens.
373 * We do it, if we decide it helps. On success, return zero with preemption
374 * disabled. On error, return -ENOMEM with preemption not disabled.
375 */
376int radix_tree_maybe_preload(gfp_t gfp_mask)
377{
378 if (gfpflags_allow_blocking(gfp_mask))
379 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
380 /* Preloading doesn't help anything with this gfp mask, skip it */
381 local_lock(&radix_tree_preloads.lock);
382 return 0;
383}
384EXPORT_SYMBOL(radix_tree_maybe_preload);
385
386static unsigned radix_tree_load_root(const struct radix_tree_root *root,
387 struct radix_tree_node **nodep, unsigned long *maxindex)
388{
389 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
390
391 *nodep = node;
392
393 if (likely(radix_tree_is_internal_node(node))) {
394 node = entry_to_node(node);
395 *maxindex = node_maxindex(node);
396 return node->shift + RADIX_TREE_MAP_SHIFT;
397 }
398
399 *maxindex = 0;
400 return 0;
401}
402
403/*
404 * Extend a radix tree so it can store key @index.
405 */
406static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
407 unsigned long index, unsigned int shift)
408{
409 void *entry;
410 unsigned int maxshift;
411 int tag;
412
413 /* Figure out what the shift should be. */
414 maxshift = shift;
415 while (index > shift_maxindex(maxshift))
416 maxshift += RADIX_TREE_MAP_SHIFT;
417
418 entry = rcu_dereference_raw(root->xa_head);
419 if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
420 goto out;
421
422 do {
423 struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
424 root, shift, 0, 1, 0);
425 if (!node)
426 return -ENOMEM;
427
428 if (is_idr(root)) {
429 all_tag_set(node, IDR_FREE);
430 if (!root_tag_get(root, IDR_FREE)) {
431 tag_clear(node, IDR_FREE, 0);
432 root_tag_set(root, IDR_FREE);
433 }
434 } else {
435 /* Propagate the aggregated tag info to the new child */
436 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
437 if (root_tag_get(root, tag))
438 tag_set(node, tag, 0);
439 }
440 }
441
442 BUG_ON(shift > BITS_PER_LONG);
443 if (radix_tree_is_internal_node(entry)) {
444 entry_to_node(entry)->parent = node;
445 } else if (xa_is_value(entry)) {
446 /* Moving a value entry root->xa_head to a node */
447 node->nr_values = 1;
448 }
449 /*
450 * entry was already in the radix tree, so we do not need
451 * rcu_assign_pointer here
452 */
453 node->slots[0] = (void __rcu *)entry;
454 entry = node_to_entry(node);
455 rcu_assign_pointer(root->xa_head, entry);
456 shift += RADIX_TREE_MAP_SHIFT;
457 } while (shift <= maxshift);
458out:
459 return maxshift + RADIX_TREE_MAP_SHIFT;
460}
461
462/**
463 * radix_tree_shrink - shrink radix tree to minimum height
464 * @root: radix tree root
465 */
466static inline bool radix_tree_shrink(struct radix_tree_root *root)
467{
468 bool shrunk = false;
469
470 for (;;) {
471 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
472 struct radix_tree_node *child;
473
474 if (!radix_tree_is_internal_node(node))
475 break;
476 node = entry_to_node(node);
477
478 /*
479 * The candidate node has more than one child, or its child
480 * is not at the leftmost slot, we cannot shrink.
481 */
482 if (node->count != 1)
483 break;
484 child = rcu_dereference_raw(node->slots[0]);
485 if (!child)
486 break;
487
488 /*
489 * For an IDR, we must not shrink entry 0 into the root in
490 * case somebody calls idr_replace() with a pointer that
491 * appears to be an internal entry
492 */
493 if (!node->shift && is_idr(root))
494 break;
495
496 if (radix_tree_is_internal_node(child))
497 entry_to_node(child)->parent = NULL;
498
499 /*
500 * We don't need rcu_assign_pointer(), since we are simply
501 * moving the node from one part of the tree to another: if it
502 * was safe to dereference the old pointer to it
503 * (node->slots[0]), it will be safe to dereference the new
504 * one (root->xa_head) as far as dependent read barriers go.
505 */
506 root->xa_head = (void __rcu *)child;
507 if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
508 root_tag_clear(root, IDR_FREE);
509
510 /*
511 * We have a dilemma here. The node's slot[0] must not be
512 * NULLed in case there are concurrent lookups expecting to
513 * find the item. However if this was a bottom-level node,
514 * then it may be subject to the slot pointer being visible
515 * to callers dereferencing it. If item corresponding to
516 * slot[0] is subsequently deleted, these callers would expect
517 * their slot to become empty sooner or later.
518 *
519 * For example, lockless pagecache will look up a slot, deref
520 * the page pointer, and if the page has 0 refcount it means it
521 * was concurrently deleted from pagecache so try the deref
522 * again. Fortunately there is already a requirement for logic
523 * to retry the entire slot lookup -- the indirect pointer
524 * problem (replacing direct root node with an indirect pointer
525 * also results in a stale slot). So tag the slot as indirect
526 * to force callers to retry.
527 */
528 node->count = 0;
529 if (!radix_tree_is_internal_node(child)) {
530 node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
531 }
532
533 WARN_ON_ONCE(!list_empty(&node->private_list));
534 radix_tree_node_free(node);
535 shrunk = true;
536 }
537
538 return shrunk;
539}
540
541static bool delete_node(struct radix_tree_root *root,
542 struct radix_tree_node *node)
543{
544 bool deleted = false;
545
546 do {
547 struct radix_tree_node *parent;
548
549 if (node->count) {
550 if (node_to_entry(node) ==
551 rcu_dereference_raw(root->xa_head))
552 deleted |= radix_tree_shrink(root);
553 return deleted;
554 }
555
556 parent = node->parent;
557 if (parent) {
558 parent->slots[node->offset] = NULL;
559 parent->count--;
560 } else {
561 /*
562 * Shouldn't the tags already have all been cleared
563 * by the caller?
564 */
565 if (!is_idr(root))
566 root_tag_clear_all(root);
567 root->xa_head = NULL;
568 }
569
570 WARN_ON_ONCE(!list_empty(&node->private_list));
571 radix_tree_node_free(node);
572 deleted = true;
573
574 node = parent;
575 } while (node);
576
577 return deleted;
578}
579
580/**
581 * __radix_tree_create - create a slot in a radix tree
582 * @root: radix tree root
583 * @index: index key
584 * @nodep: returns node
585 * @slotp: returns slot
586 *
587 * Create, if necessary, and return the node and slot for an item
588 * at position @index in the radix tree @root.
589 *
590 * Until there is more than one item in the tree, no nodes are
591 * allocated and @root->xa_head is used as a direct slot instead of
592 * pointing to a node, in which case *@nodep will be NULL.
593 *
594 * Returns -ENOMEM, or 0 for success.
595 */
596static int __radix_tree_create(struct radix_tree_root *root,
597 unsigned long index, struct radix_tree_node **nodep,
598 void __rcu ***slotp)
599{
600 struct radix_tree_node *node = NULL, *child;
601 void __rcu **slot = (void __rcu **)&root->xa_head;
602 unsigned long maxindex;
603 unsigned int shift, offset = 0;
604 unsigned long max = index;
605 gfp_t gfp = root_gfp_mask(root);
606
607 shift = radix_tree_load_root(root, &child, &maxindex);
608
609 /* Make sure the tree is high enough. */
610 if (max > maxindex) {
611 int error = radix_tree_extend(root, gfp, max, shift);
612 if (error < 0)
613 return error;
614 shift = error;
615 child = rcu_dereference_raw(root->xa_head);
616 }
617
618 while (shift > 0) {
619 shift -= RADIX_TREE_MAP_SHIFT;
620 if (child == NULL) {
621 /* Have to add a child node. */
622 child = radix_tree_node_alloc(gfp, node, root, shift,
623 offset, 0, 0);
624 if (!child)
625 return -ENOMEM;
626 rcu_assign_pointer(*slot, node_to_entry(child));
627 if (node)
628 node->count++;
629 } else if (!radix_tree_is_internal_node(child))
630 break;
631
632 /* Go a level down */
633 node = entry_to_node(child);
634 offset = radix_tree_descend(node, &child, index);
635 slot = &node->slots[offset];
636 }
637
638 if (nodep)
639 *nodep = node;
640 if (slotp)
641 *slotp = slot;
642 return 0;
643}
644
645/*
646 * Free any nodes below this node. The tree is presumed to not need
647 * shrinking, and any user data in the tree is presumed to not need a
648 * destructor called on it. If we need to add a destructor, we can
649 * add that functionality later. Note that we may not clear tags or
650 * slots from the tree as an RCU walker may still have a pointer into
651 * this subtree. We could replace the entries with RADIX_TREE_RETRY,
652 * but we'll still have to clear those in rcu_free.
653 */
654static void radix_tree_free_nodes(struct radix_tree_node *node)
655{
656 unsigned offset = 0;
657 struct radix_tree_node *child = entry_to_node(node);
658
659 for (;;) {
660 void *entry = rcu_dereference_raw(child->slots[offset]);
661 if (xa_is_node(entry) && child->shift) {
662 child = entry_to_node(entry);
663 offset = 0;
664 continue;
665 }
666 offset++;
667 while (offset == RADIX_TREE_MAP_SIZE) {
668 struct radix_tree_node *old = child;
669 offset = child->offset + 1;
670 child = child->parent;
671 WARN_ON_ONCE(!list_empty(&old->private_list));
672 radix_tree_node_free(old);
673 if (old == entry_to_node(node))
674 return;
675 }
676 }
677}
678
679static inline int insert_entries(struct radix_tree_node *node,
680 void __rcu **slot, void *item, bool replace)
681{
682 if (*slot)
683 return -EEXIST;
684 rcu_assign_pointer(*slot, item);
685 if (node) {
686 node->count++;
687 if (xa_is_value(item))
688 node->nr_values++;
689 }
690 return 1;
691}
692
693/**
694 * radix_tree_insert - insert into a radix tree
695 * @root: radix tree root
696 * @index: index key
697 * @item: item to insert
698 *
699 * Insert an item into the radix tree at position @index.
700 */
701int radix_tree_insert(struct radix_tree_root *root, unsigned long index,
702 void *item)
703{
704 struct radix_tree_node *node;
705 void __rcu **slot;
706 int error;
707
708 BUG_ON(radix_tree_is_internal_node(item));
709
710 error = __radix_tree_create(root, index, &node, &slot);
711 if (error)
712 return error;
713
714 error = insert_entries(node, slot, item, false);
715 if (error < 0)
716 return error;
717
718 if (node) {
719 unsigned offset = get_slot_offset(node, slot);
720 BUG_ON(tag_get(node, 0, offset));
721 BUG_ON(tag_get(node, 1, offset));
722 BUG_ON(tag_get(node, 2, offset));
723 } else {
724 BUG_ON(root_tags_get(root));
725 }
726
727 return 0;
728}
729EXPORT_SYMBOL(radix_tree_insert);
730
731/**
732 * __radix_tree_lookup - lookup an item in a radix tree
733 * @root: radix tree root
734 * @index: index key
735 * @nodep: returns node
736 * @slotp: returns slot
737 *
738 * Lookup and return the item at position @index in the radix
739 * tree @root.
740 *
741 * Until there is more than one item in the tree, no nodes are
742 * allocated and @root->xa_head is used as a direct slot instead of
743 * pointing to a node, in which case *@nodep will be NULL.
744 */
745void *__radix_tree_lookup(const struct radix_tree_root *root,
746 unsigned long index, struct radix_tree_node **nodep,
747 void __rcu ***slotp)
748{
749 struct radix_tree_node *node, *parent;
750 unsigned long maxindex;
751 void __rcu **slot;
752
753 restart:
754 parent = NULL;
755 slot = (void __rcu **)&root->xa_head;
756 radix_tree_load_root(root, &node, &maxindex);
757 if (index > maxindex)
758 return NULL;
759
760 while (radix_tree_is_internal_node(node)) {
761 unsigned offset;
762
763 parent = entry_to_node(node);
764 offset = radix_tree_descend(parent, &node, index);
765 slot = parent->slots + offset;
766 if (node == RADIX_TREE_RETRY)
767 goto restart;
768 if (parent->shift == 0)
769 break;
770 }
771
772 if (nodep)
773 *nodep = parent;
774 if (slotp)
775 *slotp = slot;
776 return node;
777}
778
779/**
780 * radix_tree_lookup_slot - lookup a slot in a radix tree
781 * @root: radix tree root
782 * @index: index key
783 *
784 * Returns: the slot corresponding to the position @index in the
785 * radix tree @root. This is useful for update-if-exists operations.
786 *
787 * This function can be called under rcu_read_lock iff the slot is not
788 * modified by radix_tree_replace_slot, otherwise it must be called
789 * exclusive from other writers. Any dereference of the slot must be done
790 * using radix_tree_deref_slot.
791 */
792void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
793 unsigned long index)
794{
795 void __rcu **slot;
796
797 if (!__radix_tree_lookup(root, index, NULL, &slot))
798 return NULL;
799 return slot;
800}
801EXPORT_SYMBOL(radix_tree_lookup_slot);
802
803/**
804 * radix_tree_lookup - perform lookup operation on a radix tree
805 * @root: radix tree root
806 * @index: index key
807 *
808 * Lookup the item at the position @index in the radix tree @root.
809 *
810 * This function can be called under rcu_read_lock, however the caller
811 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
812 * them safely). No RCU barriers are required to access or modify the
813 * returned item, however.
814 */
815void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
816{
817 return __radix_tree_lookup(root, index, NULL, NULL);
818}
819EXPORT_SYMBOL(radix_tree_lookup);
820
821static void replace_slot(void __rcu **slot, void *item,
822 struct radix_tree_node *node, int count, int values)
823{
824 if (node && (count || values)) {
825 node->count += count;
826 node->nr_values += values;
827 }
828
829 rcu_assign_pointer(*slot, item);
830}
831
832static bool node_tag_get(const struct radix_tree_root *root,
833 const struct radix_tree_node *node,
834 unsigned int tag, unsigned int offset)
835{
836 if (node)
837 return tag_get(node, tag, offset);
838 return root_tag_get(root, tag);
839}
840
841/*
842 * IDR users want to be able to store NULL in the tree, so if the slot isn't
843 * free, don't adjust the count, even if it's transitioning between NULL and
844 * non-NULL. For the IDA, we mark slots as being IDR_FREE while they still
845 * have empty bits, but it only stores NULL in slots when they're being
846 * deleted.
847 */
848static int calculate_count(struct radix_tree_root *root,
849 struct radix_tree_node *node, void __rcu **slot,
850 void *item, void *old)
851{
852 if (is_idr(root)) {
853 unsigned offset = get_slot_offset(node, slot);
854 bool free = node_tag_get(root, node, IDR_FREE, offset);
855 if (!free)
856 return 0;
857 if (!old)
858 return 1;
859 }
860 return !!item - !!old;
861}
862
863/**
864 * __radix_tree_replace - replace item in a slot
865 * @root: radix tree root
866 * @node: pointer to tree node
867 * @slot: pointer to slot in @node
868 * @item: new item to store in the slot.
869 *
870 * For use with __radix_tree_lookup(). Caller must hold tree write locked
871 * across slot lookup and replacement.
872 */
873void __radix_tree_replace(struct radix_tree_root *root,
874 struct radix_tree_node *node,
875 void __rcu **slot, void *item)
876{
877 void *old = rcu_dereference_raw(*slot);
878 int values = !!xa_is_value(item) - !!xa_is_value(old);
879 int count = calculate_count(root, node, slot, item, old);
880
881 /*
882 * This function supports replacing value entries and
883 * deleting entries, but that needs accounting against the
884 * node unless the slot is root->xa_head.
885 */
886 WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
887 (count || values));
888 replace_slot(slot, item, node, count, values);
889
890 if (!node)
891 return;
892
893 delete_node(root, node);
894}
895
896/**
897 * radix_tree_replace_slot - replace item in a slot
898 * @root: radix tree root
899 * @slot: pointer to slot
900 * @item: new item to store in the slot.
901 *
902 * For use with radix_tree_lookup_slot() and
903 * radix_tree_gang_lookup_tag_slot(). Caller must hold tree write locked
904 * across slot lookup and replacement.
905 *
906 * NOTE: This cannot be used to switch between non-entries (empty slots),
907 * regular entries, and value entries, as that requires accounting
908 * inside the radix tree node. When switching from one type of entry or
909 * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
910 * radix_tree_iter_replace().
911 */
912void radix_tree_replace_slot(struct radix_tree_root *root,
913 void __rcu **slot, void *item)
914{
915 __radix_tree_replace(root, NULL, slot, item);
916}
917EXPORT_SYMBOL(radix_tree_replace_slot);
918
919/**
920 * radix_tree_iter_replace - replace item in a slot
921 * @root: radix tree root
922 * @iter: iterator state
923 * @slot: pointer to slot
924 * @item: new item to store in the slot.
925 *
926 * For use with radix_tree_for_each_slot().
927 * Caller must hold tree write locked.
928 */
929void radix_tree_iter_replace(struct radix_tree_root *root,
930 const struct radix_tree_iter *iter,
931 void __rcu **slot, void *item)
932{
933 __radix_tree_replace(root, iter->node, slot, item);
934}
935
936static void node_tag_set(struct radix_tree_root *root,
937 struct radix_tree_node *node,
938 unsigned int tag, unsigned int offset)
939{
940 while (node) {
941 if (tag_get(node, tag, offset))
942 return;
943 tag_set(node, tag, offset);
944 offset = node->offset;
945 node = node->parent;
946 }
947
948 if (!root_tag_get(root, tag))
949 root_tag_set(root, tag);
950}
951
952/**
953 * radix_tree_tag_set - set a tag on a radix tree node
954 * @root: radix tree root
955 * @index: index key
956 * @tag: tag index
957 *
958 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
959 * corresponding to @index in the radix tree. From
960 * the root all the way down to the leaf node.
961 *
962 * Returns the address of the tagged item. Setting a tag on a not-present
963 * item is a bug.
964 */
965void *radix_tree_tag_set(struct radix_tree_root *root,
966 unsigned long index, unsigned int tag)
967{
968 struct radix_tree_node *node, *parent;
969 unsigned long maxindex;
970
971 radix_tree_load_root(root, &node, &maxindex);
972 BUG_ON(index > maxindex);
973
974 while (radix_tree_is_internal_node(node)) {
975 unsigned offset;
976
977 parent = entry_to_node(node);
978 offset = radix_tree_descend(parent, &node, index);
979 BUG_ON(!node);
980
981 if (!tag_get(parent, tag, offset))
982 tag_set(parent, tag, offset);
983 }
984
985 /* set the root's tag bit */
986 if (!root_tag_get(root, tag))
987 root_tag_set(root, tag);
988
989 return node;
990}
991EXPORT_SYMBOL(radix_tree_tag_set);
992
993static void node_tag_clear(struct radix_tree_root *root,
994 struct radix_tree_node *node,
995 unsigned int tag, unsigned int offset)
996{
997 while (node) {
998 if (!tag_get(node, tag, offset))
999 return;
1000 tag_clear(node, tag, offset);
1001 if (any_tag_set(node, tag))
1002 return;
1003
1004 offset = node->offset;
1005 node = node->parent;
1006 }
1007
1008 /* clear the root's tag bit */
1009 if (root_tag_get(root, tag))
1010 root_tag_clear(root, tag);
1011}
1012
1013/**
1014 * radix_tree_tag_clear - clear a tag on a radix tree node
1015 * @root: radix tree root
1016 * @index: index key
1017 * @tag: tag index
1018 *
1019 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1020 * corresponding to @index in the radix tree. If this causes
1021 * the leaf node to have no tags set then clear the tag in the
1022 * next-to-leaf node, etc.
1023 *
1024 * Returns the address of the tagged item on success, else NULL. ie:
1025 * has the same return value and semantics as radix_tree_lookup().
1026 */
1027void *radix_tree_tag_clear(struct radix_tree_root *root,
1028 unsigned long index, unsigned int tag)
1029{
1030 struct radix_tree_node *node, *parent;
1031 unsigned long maxindex;
1032 int offset;
1033
1034 radix_tree_load_root(root, &node, &maxindex);
1035 if (index > maxindex)
1036 return NULL;
1037
1038 parent = NULL;
1039
1040 while (radix_tree_is_internal_node(node)) {
1041 parent = entry_to_node(node);
1042 offset = radix_tree_descend(parent, &node, index);
1043 }
1044
1045 if (node)
1046 node_tag_clear(root, parent, tag, offset);
1047
1048 return node;
1049}
1050EXPORT_SYMBOL(radix_tree_tag_clear);
1051
1052/**
1053 * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1054 * @root: radix tree root
1055 * @iter: iterator state
1056 * @tag: tag to clear
1057 */
1058void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1059 const struct radix_tree_iter *iter, unsigned int tag)
1060{
1061 node_tag_clear(root, iter->node, tag, iter_offset(iter));
1062}
1063
1064/**
1065 * radix_tree_tag_get - get a tag on a radix tree node
1066 * @root: radix tree root
1067 * @index: index key
1068 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
1069 *
1070 * Return values:
1071 *
1072 * 0: tag not present or not set
1073 * 1: tag set
1074 *
1075 * Note that the return value of this function may not be relied on, even if
1076 * the RCU lock is held, unless tag modification and node deletion are excluded
1077 * from concurrency.
1078 */
1079int radix_tree_tag_get(const struct radix_tree_root *root,
1080 unsigned long index, unsigned int tag)
1081{
1082 struct radix_tree_node *node, *parent;
1083 unsigned long maxindex;
1084
1085 if (!root_tag_get(root, tag))
1086 return 0;
1087
1088 radix_tree_load_root(root, &node, &maxindex);
1089 if (index > maxindex)
1090 return 0;
1091
1092 while (radix_tree_is_internal_node(node)) {
1093 unsigned offset;
1094
1095 parent = entry_to_node(node);
1096 offset = radix_tree_descend(parent, &node, index);
1097
1098 if (!tag_get(parent, tag, offset))
1099 return 0;
1100 if (node == RADIX_TREE_RETRY)
1101 break;
1102 }
1103
1104 return 1;
1105}
1106EXPORT_SYMBOL(radix_tree_tag_get);
1107
1108/* Construct iter->tags bit-mask from node->tags[tag] array */
1109static void set_iter_tags(struct radix_tree_iter *iter,
1110 struct radix_tree_node *node, unsigned offset,
1111 unsigned tag)
1112{
1113 unsigned tag_long = offset / BITS_PER_LONG;
1114 unsigned tag_bit = offset % BITS_PER_LONG;
1115
1116 if (!node) {
1117 iter->tags = 1;
1118 return;
1119 }
1120
1121 iter->tags = node->tags[tag][tag_long] >> tag_bit;
1122
1123 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1124 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1125 /* Pick tags from next element */
1126 if (tag_bit)
1127 iter->tags |= node->tags[tag][tag_long + 1] <<
1128 (BITS_PER_LONG - tag_bit);
1129 /* Clip chunk size, here only BITS_PER_LONG tags */
1130 iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1131 }
1132}
1133
1134void __rcu **radix_tree_iter_resume(void __rcu **slot,
1135 struct radix_tree_iter *iter)
1136{
1137 slot++;
1138 iter->index = __radix_tree_iter_add(iter, 1);
1139 iter->next_index = iter->index;
1140 iter->tags = 0;
1141 return NULL;
1142}
1143EXPORT_SYMBOL(radix_tree_iter_resume);
1144
1145/**
1146 * radix_tree_next_chunk - find next chunk of slots for iteration
1147 *
1148 * @root: radix tree root
1149 * @iter: iterator state
1150 * @flags: RADIX_TREE_ITER_* flags and tag index
1151 * Returns: pointer to chunk first slot, or NULL if iteration is over
1152 */
1153void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1154 struct radix_tree_iter *iter, unsigned flags)
1155{
1156 unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1157 struct radix_tree_node *node, *child;
1158 unsigned long index, offset, maxindex;
1159
1160 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1161 return NULL;
1162
1163 /*
1164 * Catch next_index overflow after ~0UL. iter->index never overflows
1165 * during iterating; it can be zero only at the beginning.
1166 * And we cannot overflow iter->next_index in a single step,
1167 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1168 *
1169 * This condition also used by radix_tree_next_slot() to stop
1170 * contiguous iterating, and forbid switching to the next chunk.
1171 */
1172 index = iter->next_index;
1173 if (!index && iter->index)
1174 return NULL;
1175
1176 restart:
1177 radix_tree_load_root(root, &child, &maxindex);
1178 if (index > maxindex)
1179 return NULL;
1180 if (!child)
1181 return NULL;
1182
1183 if (!radix_tree_is_internal_node(child)) {
1184 /* Single-slot tree */
1185 iter->index = index;
1186 iter->next_index = maxindex + 1;
1187 iter->tags = 1;
1188 iter->node = NULL;
1189 return (void __rcu **)&root->xa_head;
1190 }
1191
1192 do {
1193 node = entry_to_node(child);
1194 offset = radix_tree_descend(node, &child, index);
1195
1196 if ((flags & RADIX_TREE_ITER_TAGGED) ?
1197 !tag_get(node, tag, offset) : !child) {
1198 /* Hole detected */
1199 if (flags & RADIX_TREE_ITER_CONTIG)
1200 return NULL;
1201
1202 if (flags & RADIX_TREE_ITER_TAGGED)
1203 offset = radix_tree_find_next_bit(node, tag,
1204 offset + 1);
1205 else
1206 while (++offset < RADIX_TREE_MAP_SIZE) {
1207 void *slot = rcu_dereference_raw(
1208 node->slots[offset]);
1209 if (slot)
1210 break;
1211 }
1212 index &= ~node_maxindex(node);
1213 index += offset << node->shift;
1214 /* Overflow after ~0UL */
1215 if (!index)
1216 return NULL;
1217 if (offset == RADIX_TREE_MAP_SIZE)
1218 goto restart;
1219 child = rcu_dereference_raw(node->slots[offset]);
1220 }
1221
1222 if (!child)
1223 goto restart;
1224 if (child == RADIX_TREE_RETRY)
1225 break;
1226 } while (node->shift && radix_tree_is_internal_node(child));
1227
1228 /* Update the iterator state */
1229 iter->index = (index &~ node_maxindex(node)) | offset;
1230 iter->next_index = (index | node_maxindex(node)) + 1;
1231 iter->node = node;
1232
1233 if (flags & RADIX_TREE_ITER_TAGGED)
1234 set_iter_tags(iter, node, offset, tag);
1235
1236 return node->slots + offset;
1237}
1238EXPORT_SYMBOL(radix_tree_next_chunk);
1239
1240/**
1241 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1242 * @root: radix tree root
1243 * @results: where the results of the lookup are placed
1244 * @first_index: start the lookup from this key
1245 * @max_items: place up to this many items at *results
1246 *
1247 * Performs an index-ascending scan of the tree for present items. Places
1248 * them at *@results and returns the number of items which were placed at
1249 * *@results.
1250 *
1251 * The implementation is naive.
1252 *
1253 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1254 * rcu_read_lock. In this case, rather than the returned results being
1255 * an atomic snapshot of the tree at a single point in time, the
1256 * semantics of an RCU protected gang lookup are as though multiple
1257 * radix_tree_lookups have been issued in individual locks, and results
1258 * stored in 'results'.
1259 */
1260unsigned int
1261radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1262 unsigned long first_index, unsigned int max_items)
1263{
1264 struct radix_tree_iter iter;
1265 void __rcu **slot;
1266 unsigned int ret = 0;
1267
1268 if (unlikely(!max_items))
1269 return 0;
1270
1271 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1272 results[ret] = rcu_dereference_raw(*slot);
1273 if (!results[ret])
1274 continue;
1275 if (radix_tree_is_internal_node(results[ret])) {
1276 slot = radix_tree_iter_retry(&iter);
1277 continue;
1278 }
1279 if (++ret == max_items)
1280 break;
1281 }
1282
1283 return ret;
1284}
1285EXPORT_SYMBOL(radix_tree_gang_lookup);
1286
1287/**
1288 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1289 * based on a tag
1290 * @root: radix tree root
1291 * @results: where the results of the lookup are placed
1292 * @first_index: start the lookup from this key
1293 * @max_items: place up to this many items at *results
1294 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1295 *
1296 * Performs an index-ascending scan of the tree for present items which
1297 * have the tag indexed by @tag set. Places the items at *@results and
1298 * returns the number of items which were placed at *@results.
1299 */
1300unsigned int
1301radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1302 unsigned long first_index, unsigned int max_items,
1303 unsigned int tag)
1304{
1305 struct radix_tree_iter iter;
1306 void __rcu **slot;
1307 unsigned int ret = 0;
1308
1309 if (unlikely(!max_items))
1310 return 0;
1311
1312 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1313 results[ret] = rcu_dereference_raw(*slot);
1314 if (!results[ret])
1315 continue;
1316 if (radix_tree_is_internal_node(results[ret])) {
1317 slot = radix_tree_iter_retry(&iter);
1318 continue;
1319 }
1320 if (++ret == max_items)
1321 break;
1322 }
1323
1324 return ret;
1325}
1326EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1327
1328/**
1329 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1330 * radix tree based on a tag
1331 * @root: radix tree root
1332 * @results: where the results of the lookup are placed
1333 * @first_index: start the lookup from this key
1334 * @max_items: place up to this many items at *results
1335 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1336 *
1337 * Performs an index-ascending scan of the tree for present items which
1338 * have the tag indexed by @tag set. Places the slots at *@results and
1339 * returns the number of slots which were placed at *@results.
1340 */
1341unsigned int
1342radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1343 void __rcu ***results, unsigned long first_index,
1344 unsigned int max_items, unsigned int tag)
1345{
1346 struct radix_tree_iter iter;
1347 void __rcu **slot;
1348 unsigned int ret = 0;
1349
1350 if (unlikely(!max_items))
1351 return 0;
1352
1353 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1354 results[ret] = slot;
1355 if (++ret == max_items)
1356 break;
1357 }
1358
1359 return ret;
1360}
1361EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1362
1363static bool __radix_tree_delete(struct radix_tree_root *root,
1364 struct radix_tree_node *node, void __rcu **slot)
1365{
1366 void *old = rcu_dereference_raw(*slot);
1367 int values = xa_is_value(old) ? -1 : 0;
1368 unsigned offset = get_slot_offset(node, slot);
1369 int tag;
1370
1371 if (is_idr(root))
1372 node_tag_set(root, node, IDR_FREE, offset);
1373 else
1374 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1375 node_tag_clear(root, node, tag, offset);
1376
1377 replace_slot(slot, NULL, node, -1, values);
1378 return node && delete_node(root, node);
1379}
1380
1381/**
1382 * radix_tree_iter_delete - delete the entry at this iterator position
1383 * @root: radix tree root
1384 * @iter: iterator state
1385 * @slot: pointer to slot
1386 *
1387 * Delete the entry at the position currently pointed to by the iterator.
1388 * This may result in the current node being freed; if it is, the iterator
1389 * is advanced so that it will not reference the freed memory. This
1390 * function may be called without any locking if there are no other threads
1391 * which can access this tree.
1392 */
1393void radix_tree_iter_delete(struct radix_tree_root *root,
1394 struct radix_tree_iter *iter, void __rcu **slot)
1395{
1396 if (__radix_tree_delete(root, iter->node, slot))
1397 iter->index = iter->next_index;
1398}
1399EXPORT_SYMBOL(radix_tree_iter_delete);
1400
1401/**
1402 * radix_tree_delete_item - delete an item from a radix tree
1403 * @root: radix tree root
1404 * @index: index key
1405 * @item: expected item
1406 *
1407 * Remove @item at @index from the radix tree rooted at @root.
1408 *
1409 * Return: the deleted entry, or %NULL if it was not present
1410 * or the entry at the given @index was not @item.
1411 */
1412void *radix_tree_delete_item(struct radix_tree_root *root,
1413 unsigned long index, void *item)
1414{
1415 struct radix_tree_node *node = NULL;
1416 void __rcu **slot = NULL;
1417 void *entry;
1418
1419 entry = __radix_tree_lookup(root, index, &node, &slot);
1420 if (!slot)
1421 return NULL;
1422 if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
1423 get_slot_offset(node, slot))))
1424 return NULL;
1425
1426 if (item && entry != item)
1427 return NULL;
1428
1429 __radix_tree_delete(root, node, slot);
1430
1431 return entry;
1432}
1433EXPORT_SYMBOL(radix_tree_delete_item);
1434
1435/**
1436 * radix_tree_delete - delete an entry from a radix tree
1437 * @root: radix tree root
1438 * @index: index key
1439 *
1440 * Remove the entry at @index from the radix tree rooted at @root.
1441 *
1442 * Return: The deleted entry, or %NULL if it was not present.
1443 */
1444void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1445{
1446 return radix_tree_delete_item(root, index, NULL);
1447}
1448EXPORT_SYMBOL(radix_tree_delete);
1449
1450/**
1451 * radix_tree_tagged - test whether any items in the tree are tagged
1452 * @root: radix tree root
1453 * @tag: tag to test
1454 */
1455int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
1456{
1457 return root_tag_get(root, tag);
1458}
1459EXPORT_SYMBOL(radix_tree_tagged);
1460
1461/**
1462 * idr_preload - preload for idr_alloc()
1463 * @gfp_mask: allocation mask to use for preloading
1464 *
1465 * Preallocate memory to use for the next call to idr_alloc(). This function
1466 * returns with preemption disabled. It will be enabled by idr_preload_end().
1467 */
1468void idr_preload(gfp_t gfp_mask)
1469{
1470 if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
1471 local_lock(&radix_tree_preloads.lock);
1472}
1473EXPORT_SYMBOL(idr_preload);
1474
1475void __rcu **idr_get_free(struct radix_tree_root *root,
1476 struct radix_tree_iter *iter, gfp_t gfp,
1477 unsigned long max)
1478{
1479 struct radix_tree_node *node = NULL, *child;
1480 void __rcu **slot = (void __rcu **)&root->xa_head;
1481 unsigned long maxindex, start = iter->next_index;
1482 unsigned int shift, offset = 0;
1483
1484 grow:
1485 shift = radix_tree_load_root(root, &child, &maxindex);
1486 if (!radix_tree_tagged(root, IDR_FREE))
1487 start = max(start, maxindex + 1);
1488 if (start > max)
1489 return ERR_PTR(-ENOSPC);
1490
1491 if (start > maxindex) {
1492 int error = radix_tree_extend(root, gfp, start, shift);
1493 if (error < 0)
1494 return ERR_PTR(error);
1495 shift = error;
1496 child = rcu_dereference_raw(root->xa_head);
1497 }
1498 if (start == 0 && shift == 0)
1499 shift = RADIX_TREE_MAP_SHIFT;
1500
1501 while (shift) {
1502 shift -= RADIX_TREE_MAP_SHIFT;
1503 if (child == NULL) {
1504 /* Have to add a child node. */
1505 child = radix_tree_node_alloc(gfp, node, root, shift,
1506 offset, 0, 0);
1507 if (!child)
1508 return ERR_PTR(-ENOMEM);
1509 all_tag_set(child, IDR_FREE);
1510 rcu_assign_pointer(*slot, node_to_entry(child));
1511 if (node)
1512 node->count++;
1513 } else if (!radix_tree_is_internal_node(child))
1514 break;
1515
1516 node = entry_to_node(child);
1517 offset = radix_tree_descend(node, &child, start);
1518 if (!tag_get(node, IDR_FREE, offset)) {
1519 offset = radix_tree_find_next_bit(node, IDR_FREE,
1520 offset + 1);
1521 start = next_index(start, node, offset);
1522 if (start > max || start == 0)
1523 return ERR_PTR(-ENOSPC);
1524 while (offset == RADIX_TREE_MAP_SIZE) {
1525 offset = node->offset + 1;
1526 node = node->parent;
1527 if (!node)
1528 goto grow;
1529 shift = node->shift;
1530 }
1531 child = rcu_dereference_raw(node->slots[offset]);
1532 }
1533 slot = &node->slots[offset];
1534 }
1535
1536 iter->index = start;
1537 if (node)
1538 iter->next_index = 1 + min(max, (start | node_maxindex(node)));
1539 else
1540 iter->next_index = 1;
1541 iter->node = node;
1542 set_iter_tags(iter, node, offset, IDR_FREE);
1543
1544 return slot;
1545}
1546
1547/**
1548 * idr_destroy - release all internal memory from an IDR
1549 * @idr: idr handle
1550 *
1551 * After this function is called, the IDR is empty, and may be reused or
1552 * the data structure containing it may be freed.
1553 *
1554 * A typical clean-up sequence for objects stored in an idr tree will use
1555 * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1556 * free the memory used to keep track of those objects.
1557 */
1558void idr_destroy(struct idr *idr)
1559{
1560 struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
1561 if (radix_tree_is_internal_node(node))
1562 radix_tree_free_nodes(node);
1563 idr->idr_rt.xa_head = NULL;
1564 root_tag_set(&idr->idr_rt, IDR_FREE);
1565}
1566EXPORT_SYMBOL(idr_destroy);
1567
1568static void
1569radix_tree_node_ctor(void *arg)
1570{
1571 struct radix_tree_node *node = arg;
1572
1573 memset(node, 0, sizeof(*node));
1574 INIT_LIST_HEAD(&node->private_list);
1575}
1576
1577static int radix_tree_cpu_dead(unsigned int cpu)
1578{
1579 struct radix_tree_preload *rtp;
1580 struct radix_tree_node *node;
1581
1582 /* Free per-cpu pool of preloaded nodes */
1583 rtp = &per_cpu(radix_tree_preloads, cpu);
1584 while (rtp->nr) {
1585 node = rtp->nodes;
1586 rtp->nodes = node->parent;
1587 kmem_cache_free(radix_tree_node_cachep, node);
1588 rtp->nr--;
1589 }
1590 return 0;
1591}
1592
1593void __init radix_tree_init(void)
1594{
1595 int ret;
1596
1597 BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
1598 BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
1599 BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
1600 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1601 sizeof(struct radix_tree_node), 0,
1602 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1603 radix_tree_node_ctor);
1604 ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
1605 NULL, radix_tree_cpu_dead);
1606 WARN_ON(ret < 0);
1607}
1/*
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
7 *
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.
12 *
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.
17 *
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.
21 */
22
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() */
37
38
39/*
40 * The height_to_maxindex array needs to be one deeper than the maximum
41 * path as height 0 holds only 1 entry.
42 */
43static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
44
45/*
46 * Radix tree node cache.
47 */
48static struct kmem_cache *radix_tree_node_cachep;
49
50/*
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
54 * radix_tree_extend).
55 *
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.
59 * Hence:
60 */
61#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
62
63/*
64 * Per-cpu pool of preloaded nodes
65 */
66struct radix_tree_preload {
67 int nr;
68 /* nodes->private_data points to next preallocated node */
69 struct radix_tree_node *nodes;
70};
71static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
72
73static inline void *ptr_to_indirect(void *ptr)
74{
75 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
76}
77
78static inline void *indirect_to_ptr(void *ptr)
79{
80 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
81}
82
83static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
84{
85 return root->gfp_mask & __GFP_BITS_MASK;
86}
87
88static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
89 int offset)
90{
91 __set_bit(offset, node->tags[tag]);
92}
93
94static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
95 int offset)
96{
97 __clear_bit(offset, node->tags[tag]);
98}
99
100static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
101 int offset)
102{
103 return test_bit(offset, node->tags[tag]);
104}
105
106static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
107{
108 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
109}
110
111static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
112{
113 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
114}
115
116static inline void root_tag_clear_all(struct radix_tree_root *root)
117{
118 root->gfp_mask &= __GFP_BITS_MASK;
119}
120
121static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
122{
123 return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
124}
125
126/*
127 * Returns 1 if any slot in the node has this tag set.
128 * Otherwise returns 0.
129 */
130static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
131{
132 int idx;
133 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
134 if (node->tags[tag][idx])
135 return 1;
136 }
137 return 0;
138}
139
140/**
141 * radix_tree_find_next_bit - find the next set bit in a memory region
142 *
143 * @addr: The address to base the search on
144 * @size: The bitmap size in bits
145 * @offset: The bitnumber to start searching at
146 *
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.
150 */
151static __always_inline unsigned long
152radix_tree_find_next_bit(const unsigned long *addr,
153 unsigned long size, unsigned long offset)
154{
155 if (!__builtin_constant_p(size))
156 return find_next_bit(addr, size, offset);
157
158 if (offset < size) {
159 unsigned long tmp;
160
161 addr += offset / BITS_PER_LONG;
162 tmp = *addr >> (offset % BITS_PER_LONG);
163 if (tmp)
164 return __ffs(tmp) + offset;
165 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
166 while (offset < size) {
167 tmp = *++addr;
168 if (tmp)
169 return __ffs(tmp) + offset;
170 offset += BITS_PER_LONG;
171 }
172 }
173 return size;
174}
175
176#if 0
177static void dump_node(void *slot, int height, int offset)
178{
179 struct radix_tree_node *node;
180 int i;
181
182 if (!slot)
183 return;
184
185 if (height == 0) {
186 pr_debug("radix entry %p offset %d\n", slot, offset);
187 return;
188 }
189
190 node = indirect_to_ptr(slot);
191 pr_debug("radix node: %p offset %d tags %lx %lx %lx path %x count %d parent %p\n",
192 slot, offset, node->tags[0][0], node->tags[1][0],
193 node->tags[2][0], node->path, node->count, node->parent);
194
195 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
196 dump_node(node->slots[i], height - 1, i);
197}
198
199/* For debug */
200static void radix_tree_dump(struct radix_tree_root *root)
201{
202 pr_debug("radix root: %p height %d rnode %p tags %x\n",
203 root, root->height, root->rnode,
204 root->gfp_mask >> __GFP_BITS_SHIFT);
205 if (!radix_tree_is_indirect_ptr(root->rnode))
206 return;
207 dump_node(root->rnode, root->height, 0);
208}
209#endif
210
211/*
212 * This assumes that the caller has performed appropriate preallocation, and
213 * that the caller has pinned this thread of control to the current CPU.
214 */
215static struct radix_tree_node *
216radix_tree_node_alloc(struct radix_tree_root *root)
217{
218 struct radix_tree_node *ret = NULL;
219 gfp_t gfp_mask = root_gfp_mask(root);
220
221 /*
222 * Preload code isn't irq safe and it doesn't make sence to use
223 * preloading in the interrupt anyway as all the allocations have to
224 * be atomic. So just do normal allocation when in interrupt.
225 */
226 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
227 struct radix_tree_preload *rtp;
228
229 /*
230 * Even if the caller has preloaded, try to allocate from the
231 * cache first for the new node to get accounted.
232 */
233 ret = kmem_cache_alloc(radix_tree_node_cachep,
234 gfp_mask | __GFP_ACCOUNT | __GFP_NOWARN);
235 if (ret)
236 goto out;
237
238 /*
239 * Provided the caller has preloaded here, we will always
240 * succeed in getting a node here (and never reach
241 * kmem_cache_alloc)
242 */
243 rtp = this_cpu_ptr(&radix_tree_preloads);
244 if (rtp->nr) {
245 ret = rtp->nodes;
246 rtp->nodes = ret->private_data;
247 ret->private_data = NULL;
248 rtp->nr--;
249 }
250 /*
251 * Update the allocation stack trace as this is more useful
252 * for debugging.
253 */
254 kmemleak_update_trace(ret);
255 goto out;
256 }
257 ret = kmem_cache_alloc(radix_tree_node_cachep,
258 gfp_mask | __GFP_ACCOUNT);
259out:
260 BUG_ON(radix_tree_is_indirect_ptr(ret));
261 return ret;
262}
263
264static void radix_tree_node_rcu_free(struct rcu_head *head)
265{
266 struct radix_tree_node *node =
267 container_of(head, struct radix_tree_node, rcu_head);
268 int i;
269
270 /*
271 * must only free zeroed nodes into the slab. radix_tree_shrink
272 * can leave us with a non-NULL entry in the first slot, so clear
273 * that here to make sure.
274 */
275 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
276 tag_clear(node, i, 0);
277
278 node->slots[0] = NULL;
279 node->count = 0;
280
281 kmem_cache_free(radix_tree_node_cachep, node);
282}
283
284static inline void
285radix_tree_node_free(struct radix_tree_node *node)
286{
287 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
288}
289
290/*
291 * Load up this CPU's radix_tree_node buffer with sufficient objects to
292 * ensure that the addition of a single element in the tree cannot fail. On
293 * success, return zero, with preemption disabled. On error, return -ENOMEM
294 * with preemption not disabled.
295 *
296 * To make use of this facility, the radix tree must be initialised without
297 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
298 */
299static int __radix_tree_preload(gfp_t gfp_mask)
300{
301 struct radix_tree_preload *rtp;
302 struct radix_tree_node *node;
303 int ret = -ENOMEM;
304
305 preempt_disable();
306 rtp = this_cpu_ptr(&radix_tree_preloads);
307 while (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
308 preempt_enable();
309 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
310 if (node == NULL)
311 goto out;
312 preempt_disable();
313 rtp = this_cpu_ptr(&radix_tree_preloads);
314 if (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
315 node->private_data = rtp->nodes;
316 rtp->nodes = node;
317 rtp->nr++;
318 } else {
319 kmem_cache_free(radix_tree_node_cachep, node);
320 }
321 }
322 ret = 0;
323out:
324 return ret;
325}
326
327/*
328 * Load up this CPU's radix_tree_node buffer with sufficient objects to
329 * ensure that the addition of a single element in the tree cannot fail. On
330 * success, return zero, with preemption disabled. On error, return -ENOMEM
331 * with preemption not disabled.
332 *
333 * To make use of this facility, the radix tree must be initialised without
334 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
335 */
336int radix_tree_preload(gfp_t gfp_mask)
337{
338 /* Warn on non-sensical use... */
339 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
340 return __radix_tree_preload(gfp_mask);
341}
342EXPORT_SYMBOL(radix_tree_preload);
343
344/*
345 * The same as above function, except we don't guarantee preloading happens.
346 * We do it, if we decide it helps. On success, return zero with preemption
347 * disabled. On error, return -ENOMEM with preemption not disabled.
348 */
349int radix_tree_maybe_preload(gfp_t gfp_mask)
350{
351 if (gfpflags_allow_blocking(gfp_mask))
352 return __radix_tree_preload(gfp_mask);
353 /* Preloading doesn't help anything with this gfp mask, skip it */
354 preempt_disable();
355 return 0;
356}
357EXPORT_SYMBOL(radix_tree_maybe_preload);
358
359/*
360 * Return the maximum key which can be store into a
361 * radix tree with height HEIGHT.
362 */
363static inline unsigned long radix_tree_maxindex(unsigned int height)
364{
365 return height_to_maxindex[height];
366}
367
368/*
369 * Extend a radix tree so it can store key @index.
370 */
371static int radix_tree_extend(struct radix_tree_root *root,
372 unsigned long index, unsigned order)
373{
374 struct radix_tree_node *node;
375 struct radix_tree_node *slot;
376 unsigned int height;
377 int tag;
378
379 /* Figure out what the height should be. */
380 height = root->height + 1;
381 while (index > radix_tree_maxindex(height))
382 height++;
383
384 if ((root->rnode == NULL) && (order == 0)) {
385 root->height = height;
386 goto out;
387 }
388
389 do {
390 unsigned int newheight;
391 if (!(node = radix_tree_node_alloc(root)))
392 return -ENOMEM;
393
394 /* Propagate the aggregated tag info into the new root */
395 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
396 if (root_tag_get(root, tag))
397 tag_set(node, tag, 0);
398 }
399
400 /* Increase the height. */
401 newheight = root->height+1;
402 BUG_ON(newheight & ~RADIX_TREE_HEIGHT_MASK);
403 node->path = newheight;
404 node->count = 1;
405 node->parent = NULL;
406 slot = root->rnode;
407 if (radix_tree_is_indirect_ptr(slot) && newheight > 1) {
408 slot = indirect_to_ptr(slot);
409 slot->parent = node;
410 slot = ptr_to_indirect(slot);
411 }
412 node->slots[0] = slot;
413 node = ptr_to_indirect(node);
414 rcu_assign_pointer(root->rnode, node);
415 root->height = newheight;
416 } while (height > root->height);
417out:
418 return 0;
419}
420
421/**
422 * __radix_tree_create - create a slot in a radix tree
423 * @root: radix tree root
424 * @index: index key
425 * @order: index occupies 2^order aligned slots
426 * @nodep: returns node
427 * @slotp: returns slot
428 *
429 * Create, if necessary, and return the node and slot for an item
430 * at position @index in the radix tree @root.
431 *
432 * Until there is more than one item in the tree, no nodes are
433 * allocated and @root->rnode is used as a direct slot instead of
434 * pointing to a node, in which case *@nodep will be NULL.
435 *
436 * Returns -ENOMEM, or 0 for success.
437 */
438int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
439 unsigned order, struct radix_tree_node **nodep,
440 void ***slotp)
441{
442 struct radix_tree_node *node = NULL, *slot;
443 unsigned int height, shift, offset;
444 int error;
445
446 BUG_ON((0 < order) && (order < RADIX_TREE_MAP_SHIFT));
447
448 /* Make sure the tree is high enough. */
449 if (index > radix_tree_maxindex(root->height)) {
450 error = radix_tree_extend(root, index, order);
451 if (error)
452 return error;
453 }
454
455 slot = root->rnode;
456
457 height = root->height;
458 shift = height * RADIX_TREE_MAP_SHIFT;
459
460 offset = 0; /* uninitialised var warning */
461 while (shift > order) {
462 if (slot == NULL) {
463 /* Have to add a child node. */
464 if (!(slot = radix_tree_node_alloc(root)))
465 return -ENOMEM;
466 slot->path = height;
467 slot->parent = node;
468 if (node) {
469 rcu_assign_pointer(node->slots[offset],
470 ptr_to_indirect(slot));
471 node->count++;
472 slot->path |= offset << RADIX_TREE_HEIGHT_SHIFT;
473 } else
474 rcu_assign_pointer(root->rnode,
475 ptr_to_indirect(slot));
476 } else if (!radix_tree_is_indirect_ptr(slot))
477 break;
478
479 /* Go a level down */
480 height--;
481 shift -= RADIX_TREE_MAP_SHIFT;
482 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
483 node = indirect_to_ptr(slot);
484 slot = node->slots[offset];
485 }
486
487 /* Insert pointers to the canonical entry */
488 if ((shift - order) > 0) {
489 int i, n = 1 << (shift - order);
490 offset = offset & ~(n - 1);
491 slot = ptr_to_indirect(&node->slots[offset]);
492 for (i = 0; i < n; i++) {
493 if (node->slots[offset + i])
494 return -EEXIST;
495 }
496
497 for (i = 1; i < n; i++) {
498 rcu_assign_pointer(node->slots[offset + i], slot);
499 node->count++;
500 }
501 }
502
503 if (nodep)
504 *nodep = node;
505 if (slotp)
506 *slotp = node ? node->slots + offset : (void **)&root->rnode;
507 return 0;
508}
509
510/**
511 * __radix_tree_insert - insert into a radix tree
512 * @root: radix tree root
513 * @index: index key
514 * @order: key covers the 2^order indices around index
515 * @item: item to insert
516 *
517 * Insert an item into the radix tree at position @index.
518 */
519int __radix_tree_insert(struct radix_tree_root *root, unsigned long index,
520 unsigned order, void *item)
521{
522 struct radix_tree_node *node;
523 void **slot;
524 int error;
525
526 BUG_ON(radix_tree_is_indirect_ptr(item));
527
528 error = __radix_tree_create(root, index, order, &node, &slot);
529 if (error)
530 return error;
531 if (*slot != NULL)
532 return -EEXIST;
533 rcu_assign_pointer(*slot, item);
534
535 if (node) {
536 node->count++;
537 BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK));
538 BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK));
539 } else {
540 BUG_ON(root_tag_get(root, 0));
541 BUG_ON(root_tag_get(root, 1));
542 }
543
544 return 0;
545}
546EXPORT_SYMBOL(__radix_tree_insert);
547
548/**
549 * __radix_tree_lookup - lookup an item in a radix tree
550 * @root: radix tree root
551 * @index: index key
552 * @nodep: returns node
553 * @slotp: returns slot
554 *
555 * Lookup and return the item at position @index in the radix
556 * tree @root.
557 *
558 * Until there is more than one item in the tree, no nodes are
559 * allocated and @root->rnode is used as a direct slot instead of
560 * pointing to a node, in which case *@nodep will be NULL.
561 */
562void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
563 struct radix_tree_node **nodep, void ***slotp)
564{
565 struct radix_tree_node *node, *parent;
566 unsigned int height, shift;
567 void **slot;
568
569 node = rcu_dereference_raw(root->rnode);
570 if (node == NULL)
571 return NULL;
572
573 if (!radix_tree_is_indirect_ptr(node)) {
574 if (index > 0)
575 return NULL;
576
577 if (nodep)
578 *nodep = NULL;
579 if (slotp)
580 *slotp = (void **)&root->rnode;
581 return node;
582 }
583 node = indirect_to_ptr(node);
584
585 height = node->path & RADIX_TREE_HEIGHT_MASK;
586 if (index > radix_tree_maxindex(height))
587 return NULL;
588
589 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
590
591 do {
592 parent = node;
593 slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK);
594 node = rcu_dereference_raw(*slot);
595 if (node == NULL)
596 return NULL;
597 if (!radix_tree_is_indirect_ptr(node))
598 break;
599 node = indirect_to_ptr(node);
600
601 shift -= RADIX_TREE_MAP_SHIFT;
602 height--;
603 } while (height > 0);
604
605 if (nodep)
606 *nodep = parent;
607 if (slotp)
608 *slotp = slot;
609 return node;
610}
611
612/**
613 * radix_tree_lookup_slot - lookup a slot in a radix tree
614 * @root: radix tree root
615 * @index: index key
616 *
617 * Returns: the slot corresponding to the position @index in the
618 * radix tree @root. This is useful for update-if-exists operations.
619 *
620 * This function can be called under rcu_read_lock iff the slot is not
621 * modified by radix_tree_replace_slot, otherwise it must be called
622 * exclusive from other writers. Any dereference of the slot must be done
623 * using radix_tree_deref_slot.
624 */
625void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
626{
627 void **slot;
628
629 if (!__radix_tree_lookup(root, index, NULL, &slot))
630 return NULL;
631 return slot;
632}
633EXPORT_SYMBOL(radix_tree_lookup_slot);
634
635/**
636 * radix_tree_lookup - perform lookup operation on a radix tree
637 * @root: radix tree root
638 * @index: index key
639 *
640 * Lookup the item at the position @index in the radix tree @root.
641 *
642 * This function can be called under rcu_read_lock, however the caller
643 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
644 * them safely). No RCU barriers are required to access or modify the
645 * returned item, however.
646 */
647void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
648{
649 return __radix_tree_lookup(root, index, NULL, NULL);
650}
651EXPORT_SYMBOL(radix_tree_lookup);
652
653/**
654 * radix_tree_tag_set - set a tag on a radix tree node
655 * @root: radix tree root
656 * @index: index key
657 * @tag: tag index
658 *
659 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
660 * corresponding to @index in the radix tree. From
661 * the root all the way down to the leaf node.
662 *
663 * Returns the address of the tagged item. Setting a tag on a not-present
664 * item is a bug.
665 */
666void *radix_tree_tag_set(struct radix_tree_root *root,
667 unsigned long index, unsigned int tag)
668{
669 unsigned int height, shift;
670 struct radix_tree_node *slot;
671
672 height = root->height;
673 BUG_ON(index > radix_tree_maxindex(height));
674
675 slot = indirect_to_ptr(root->rnode);
676 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
677
678 while (height > 0) {
679 int offset;
680
681 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
682 if (!tag_get(slot, tag, offset))
683 tag_set(slot, tag, offset);
684 slot = slot->slots[offset];
685 BUG_ON(slot == NULL);
686 if (!radix_tree_is_indirect_ptr(slot))
687 break;
688 slot = indirect_to_ptr(slot);
689 shift -= RADIX_TREE_MAP_SHIFT;
690 height--;
691 }
692
693 /* set the root's tag bit */
694 if (slot && !root_tag_get(root, tag))
695 root_tag_set(root, tag);
696
697 return slot;
698}
699EXPORT_SYMBOL(radix_tree_tag_set);
700
701/**
702 * radix_tree_tag_clear - clear a tag on a radix tree node
703 * @root: radix tree root
704 * @index: index key
705 * @tag: tag index
706 *
707 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
708 * corresponding to @index in the radix tree. If
709 * this causes the leaf node to have no tags set then clear the tag in the
710 * next-to-leaf node, etc.
711 *
712 * Returns the address of the tagged item on success, else NULL. ie:
713 * has the same return value and semantics as radix_tree_lookup().
714 */
715void *radix_tree_tag_clear(struct radix_tree_root *root,
716 unsigned long index, unsigned int tag)
717{
718 struct radix_tree_node *node = NULL;
719 struct radix_tree_node *slot = NULL;
720 unsigned int height, shift;
721 int uninitialized_var(offset);
722
723 height = root->height;
724 if (index > radix_tree_maxindex(height))
725 goto out;
726
727 shift = height * RADIX_TREE_MAP_SHIFT;
728 slot = root->rnode;
729
730 while (shift) {
731 if (slot == NULL)
732 goto out;
733 if (!radix_tree_is_indirect_ptr(slot))
734 break;
735 slot = indirect_to_ptr(slot);
736
737 shift -= RADIX_TREE_MAP_SHIFT;
738 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
739 node = slot;
740 slot = slot->slots[offset];
741 }
742
743 if (slot == NULL)
744 goto out;
745
746 while (node) {
747 if (!tag_get(node, tag, offset))
748 goto out;
749 tag_clear(node, tag, offset);
750 if (any_tag_set(node, tag))
751 goto out;
752
753 index >>= RADIX_TREE_MAP_SHIFT;
754 offset = index & RADIX_TREE_MAP_MASK;
755 node = node->parent;
756 }
757
758 /* clear the root's tag bit */
759 if (root_tag_get(root, tag))
760 root_tag_clear(root, tag);
761
762out:
763 return slot;
764}
765EXPORT_SYMBOL(radix_tree_tag_clear);
766
767/**
768 * radix_tree_tag_get - get a tag on a radix tree node
769 * @root: radix tree root
770 * @index: index key
771 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
772 *
773 * Return values:
774 *
775 * 0: tag not present or not set
776 * 1: tag set
777 *
778 * Note that the return value of this function may not be relied on, even if
779 * the RCU lock is held, unless tag modification and node deletion are excluded
780 * from concurrency.
781 */
782int radix_tree_tag_get(struct radix_tree_root *root,
783 unsigned long index, unsigned int tag)
784{
785 unsigned int height, shift;
786 struct radix_tree_node *node;
787
788 /* check the root's tag bit */
789 if (!root_tag_get(root, tag))
790 return 0;
791
792 node = rcu_dereference_raw(root->rnode);
793 if (node == NULL)
794 return 0;
795
796 if (!radix_tree_is_indirect_ptr(node))
797 return (index == 0);
798 node = indirect_to_ptr(node);
799
800 height = node->path & RADIX_TREE_HEIGHT_MASK;
801 if (index > radix_tree_maxindex(height))
802 return 0;
803
804 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
805
806 for ( ; ; ) {
807 int offset;
808
809 if (node == NULL)
810 return 0;
811 node = indirect_to_ptr(node);
812
813 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
814 if (!tag_get(node, tag, offset))
815 return 0;
816 if (height == 1)
817 return 1;
818 node = rcu_dereference_raw(node->slots[offset]);
819 if (!radix_tree_is_indirect_ptr(node))
820 return 1;
821 shift -= RADIX_TREE_MAP_SHIFT;
822 height--;
823 }
824}
825EXPORT_SYMBOL(radix_tree_tag_get);
826
827/**
828 * radix_tree_next_chunk - find next chunk of slots for iteration
829 *
830 * @root: radix tree root
831 * @iter: iterator state
832 * @flags: RADIX_TREE_ITER_* flags and tag index
833 * Returns: pointer to chunk first slot, or NULL if iteration is over
834 */
835void **radix_tree_next_chunk(struct radix_tree_root *root,
836 struct radix_tree_iter *iter, unsigned flags)
837{
838 unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
839 struct radix_tree_node *rnode, *node;
840 unsigned long index, offset, height;
841
842 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
843 return NULL;
844
845 /*
846 * Catch next_index overflow after ~0UL. iter->index never overflows
847 * during iterating; it can be zero only at the beginning.
848 * And we cannot overflow iter->next_index in a single step,
849 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
850 *
851 * This condition also used by radix_tree_next_slot() to stop
852 * contiguous iterating, and forbid swithing to the next chunk.
853 */
854 index = iter->next_index;
855 if (!index && iter->index)
856 return NULL;
857
858 rnode = rcu_dereference_raw(root->rnode);
859 if (radix_tree_is_indirect_ptr(rnode)) {
860 rnode = indirect_to_ptr(rnode);
861 } else if (rnode && !index) {
862 /* Single-slot tree */
863 iter->index = 0;
864 iter->next_index = 1;
865 iter->tags = 1;
866 return (void **)&root->rnode;
867 } else
868 return NULL;
869
870restart:
871 height = rnode->path & RADIX_TREE_HEIGHT_MASK;
872 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
873 offset = index >> shift;
874
875 /* Index outside of the tree */
876 if (offset >= RADIX_TREE_MAP_SIZE)
877 return NULL;
878
879 node = rnode;
880 while (1) {
881 struct radix_tree_node *slot;
882 if ((flags & RADIX_TREE_ITER_TAGGED) ?
883 !test_bit(offset, node->tags[tag]) :
884 !node->slots[offset]) {
885 /* Hole detected */
886 if (flags & RADIX_TREE_ITER_CONTIG)
887 return NULL;
888
889 if (flags & RADIX_TREE_ITER_TAGGED)
890 offset = radix_tree_find_next_bit(
891 node->tags[tag],
892 RADIX_TREE_MAP_SIZE,
893 offset + 1);
894 else
895 while (++offset < RADIX_TREE_MAP_SIZE) {
896 if (node->slots[offset])
897 break;
898 }
899 index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
900 index += offset << shift;
901 /* Overflow after ~0UL */
902 if (!index)
903 return NULL;
904 if (offset == RADIX_TREE_MAP_SIZE)
905 goto restart;
906 }
907
908 /* This is leaf-node */
909 if (!shift)
910 break;
911
912 slot = rcu_dereference_raw(node->slots[offset]);
913 if (slot == NULL)
914 goto restart;
915 if (!radix_tree_is_indirect_ptr(slot))
916 break;
917 node = indirect_to_ptr(slot);
918 shift -= RADIX_TREE_MAP_SHIFT;
919 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
920 }
921
922 /* Update the iterator state */
923 iter->index = index;
924 iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
925
926 /* Construct iter->tags bit-mask from node->tags[tag] array */
927 if (flags & RADIX_TREE_ITER_TAGGED) {
928 unsigned tag_long, tag_bit;
929
930 tag_long = offset / BITS_PER_LONG;
931 tag_bit = offset % BITS_PER_LONG;
932 iter->tags = node->tags[tag][tag_long] >> tag_bit;
933 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
934 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
935 /* Pick tags from next element */
936 if (tag_bit)
937 iter->tags |= node->tags[tag][tag_long + 1] <<
938 (BITS_PER_LONG - tag_bit);
939 /* Clip chunk size, here only BITS_PER_LONG tags */
940 iter->next_index = index + BITS_PER_LONG;
941 }
942 }
943
944 return node->slots + offset;
945}
946EXPORT_SYMBOL(radix_tree_next_chunk);
947
948/**
949 * radix_tree_range_tag_if_tagged - for each item in given range set given
950 * tag if item has another tag set
951 * @root: radix tree root
952 * @first_indexp: pointer to a starting index of a range to scan
953 * @last_index: last index of a range to scan
954 * @nr_to_tag: maximum number items to tag
955 * @iftag: tag index to test
956 * @settag: tag index to set if tested tag is set
957 *
958 * This function scans range of radix tree from first_index to last_index
959 * (inclusive). For each item in the range if iftag is set, the function sets
960 * also settag. The function stops either after tagging nr_to_tag items or
961 * after reaching last_index.
962 *
963 * The tags must be set from the leaf level only and propagated back up the
964 * path to the root. We must do this so that we resolve the full path before
965 * setting any tags on intermediate nodes. If we set tags as we descend, then
966 * we can get to the leaf node and find that the index that has the iftag
967 * set is outside the range we are scanning. This reults in dangling tags and
968 * can lead to problems with later tag operations (e.g. livelocks on lookups).
969 *
970 * The function returns number of leaves where the tag was set and sets
971 * *first_indexp to the first unscanned index.
972 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
973 * be prepared to handle that.
974 */
975unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
976 unsigned long *first_indexp, unsigned long last_index,
977 unsigned long nr_to_tag,
978 unsigned int iftag, unsigned int settag)
979{
980 unsigned int height = root->height;
981 struct radix_tree_node *node = NULL;
982 struct radix_tree_node *slot;
983 unsigned int shift;
984 unsigned long tagged = 0;
985 unsigned long index = *first_indexp;
986
987 last_index = min(last_index, radix_tree_maxindex(height));
988 if (index > last_index)
989 return 0;
990 if (!nr_to_tag)
991 return 0;
992 if (!root_tag_get(root, iftag)) {
993 *first_indexp = last_index + 1;
994 return 0;
995 }
996 if (height == 0) {
997 *first_indexp = last_index + 1;
998 root_tag_set(root, settag);
999 return 1;
1000 }
1001
1002 shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
1003 slot = indirect_to_ptr(root->rnode);
1004
1005 for (;;) {
1006 unsigned long upindex;
1007 int offset;
1008
1009 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
1010 if (!slot->slots[offset])
1011 goto next;
1012 if (!tag_get(slot, iftag, offset))
1013 goto next;
1014 if (shift) {
1015 node = slot;
1016 slot = slot->slots[offset];
1017 if (radix_tree_is_indirect_ptr(slot)) {
1018 slot = indirect_to_ptr(slot);
1019 shift -= RADIX_TREE_MAP_SHIFT;
1020 continue;
1021 } else {
1022 slot = node;
1023 node = node->parent;
1024 }
1025 }
1026
1027 /* tag the leaf */
1028 tagged += 1 << shift;
1029 tag_set(slot, settag, offset);
1030
1031 /* walk back up the path tagging interior nodes */
1032 upindex = index;
1033 while (node) {
1034 upindex >>= RADIX_TREE_MAP_SHIFT;
1035 offset = upindex & RADIX_TREE_MAP_MASK;
1036
1037 /* stop if we find a node with the tag already set */
1038 if (tag_get(node, settag, offset))
1039 break;
1040 tag_set(node, settag, offset);
1041 node = node->parent;
1042 }
1043
1044 /*
1045 * Small optimization: now clear that node pointer.
1046 * Since all of this slot's ancestors now have the tag set
1047 * from setting it above, we have no further need to walk
1048 * back up the tree setting tags, until we update slot to
1049 * point to another radix_tree_node.
1050 */
1051 node = NULL;
1052
1053next:
1054 /* Go to next item at level determined by 'shift' */
1055 index = ((index >> shift) + 1) << shift;
1056 /* Overflow can happen when last_index is ~0UL... */
1057 if (index > last_index || !index)
1058 break;
1059 if (tagged >= nr_to_tag)
1060 break;
1061 while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
1062 /*
1063 * We've fully scanned this node. Go up. Because
1064 * last_index is guaranteed to be in the tree, what
1065 * we do below cannot wander astray.
1066 */
1067 slot = slot->parent;
1068 shift += RADIX_TREE_MAP_SHIFT;
1069 }
1070 }
1071 /*
1072 * We need not to tag the root tag if there is no tag which is set with
1073 * settag within the range from *first_indexp to last_index.
1074 */
1075 if (tagged > 0)
1076 root_tag_set(root, settag);
1077 *first_indexp = index;
1078
1079 return tagged;
1080}
1081EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
1082
1083/**
1084 * radix_tree_gang_lookup - 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 *
1090 * Performs an index-ascending scan of the tree for present items. Places
1091 * them at *@results and returns the number of items which were placed at
1092 * *@results.
1093 *
1094 * The implementation is naive.
1095 *
1096 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1097 * rcu_read_lock. In this case, rather than the returned results being
1098 * an atomic snapshot of the tree at a single point in time, the semantics
1099 * of an RCU protected gang lookup are as though multiple radix_tree_lookups
1100 * have been issued in individual locks, and results stored in 'results'.
1101 */
1102unsigned int
1103radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
1104 unsigned long first_index, unsigned int max_items)
1105{
1106 struct radix_tree_iter iter;
1107 void **slot;
1108 unsigned int ret = 0;
1109
1110 if (unlikely(!max_items))
1111 return 0;
1112
1113 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1114 results[ret] = rcu_dereference_raw(*slot);
1115 if (!results[ret])
1116 continue;
1117 if (radix_tree_is_indirect_ptr(results[ret])) {
1118 slot = radix_tree_iter_retry(&iter);
1119 continue;
1120 }
1121 if (++ret == max_items)
1122 break;
1123 }
1124
1125 return ret;
1126}
1127EXPORT_SYMBOL(radix_tree_gang_lookup);
1128
1129/**
1130 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1131 * @root: radix tree root
1132 * @results: where the results of the lookup are placed
1133 * @indices: where their indices should be placed (but usually NULL)
1134 * @first_index: start the lookup from this key
1135 * @max_items: place up to this many items at *results
1136 *
1137 * Performs an index-ascending scan of the tree for present items. Places
1138 * their slots at *@results and returns the number of items which were
1139 * placed at *@results.
1140 *
1141 * The implementation is naive.
1142 *
1143 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1144 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1145 * protection, radix_tree_deref_slot may fail requiring a retry.
1146 */
1147unsigned int
1148radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1149 void ***results, unsigned long *indices,
1150 unsigned long first_index, unsigned int max_items)
1151{
1152 struct radix_tree_iter iter;
1153 void **slot;
1154 unsigned int ret = 0;
1155
1156 if (unlikely(!max_items))
1157 return 0;
1158
1159 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1160 results[ret] = slot;
1161 if (indices)
1162 indices[ret] = iter.index;
1163 if (++ret == max_items)
1164 break;
1165 }
1166
1167 return ret;
1168}
1169EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1170
1171/**
1172 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1173 * based on a tag
1174 * @root: radix tree root
1175 * @results: where the results of the lookup are placed
1176 * @first_index: start the lookup from this key
1177 * @max_items: place up to this many items at *results
1178 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1179 *
1180 * Performs an index-ascending scan of the tree for present items which
1181 * have the tag indexed by @tag set. Places the items at *@results and
1182 * returns the number of items which were placed at *@results.
1183 */
1184unsigned int
1185radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1186 unsigned long first_index, unsigned int max_items,
1187 unsigned int tag)
1188{
1189 struct radix_tree_iter iter;
1190 void **slot;
1191 unsigned int ret = 0;
1192
1193 if (unlikely(!max_items))
1194 return 0;
1195
1196 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1197 results[ret] = rcu_dereference_raw(*slot);
1198 if (!results[ret])
1199 continue;
1200 if (radix_tree_is_indirect_ptr(results[ret])) {
1201 slot = radix_tree_iter_retry(&iter);
1202 continue;
1203 }
1204 if (++ret == max_items)
1205 break;
1206 }
1207
1208 return ret;
1209}
1210EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1211
1212/**
1213 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1214 * radix tree based on a tag
1215 * @root: radix tree root
1216 * @results: where the results of the lookup are placed
1217 * @first_index: start the lookup from this key
1218 * @max_items: place up to this many items at *results
1219 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1220 *
1221 * Performs an index-ascending scan of the tree for present items which
1222 * have the tag indexed by @tag set. Places the slots at *@results and
1223 * returns the number of slots which were placed at *@results.
1224 */
1225unsigned int
1226radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1227 unsigned long first_index, unsigned int max_items,
1228 unsigned int tag)
1229{
1230 struct radix_tree_iter iter;
1231 void **slot;
1232 unsigned int ret = 0;
1233
1234 if (unlikely(!max_items))
1235 return 0;
1236
1237 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1238 results[ret] = slot;
1239 if (++ret == max_items)
1240 break;
1241 }
1242
1243 return ret;
1244}
1245EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1246
1247#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1248#include <linux/sched.h> /* for cond_resched() */
1249
1250/*
1251 * This linear search is at present only useful to shmem_unuse_inode().
1252 */
1253static unsigned long __locate(struct radix_tree_node *slot, void *item,
1254 unsigned long index, unsigned long *found_index)
1255{
1256 unsigned int shift, height;
1257 unsigned long i;
1258
1259 height = slot->path & RADIX_TREE_HEIGHT_MASK;
1260 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1261
1262 for ( ; height > 1; height--) {
1263 i = (index >> shift) & RADIX_TREE_MAP_MASK;
1264 for (;;) {
1265 if (slot->slots[i] != NULL)
1266 break;
1267 index &= ~((1UL << shift) - 1);
1268 index += 1UL << shift;
1269 if (index == 0)
1270 goto out; /* 32-bit wraparound */
1271 i++;
1272 if (i == RADIX_TREE_MAP_SIZE)
1273 goto out;
1274 }
1275
1276 slot = rcu_dereference_raw(slot->slots[i]);
1277 if (slot == NULL)
1278 goto out;
1279 if (!radix_tree_is_indirect_ptr(slot)) {
1280 if (slot == item) {
1281 *found_index = index + i;
1282 index = 0;
1283 } else {
1284 index += shift;
1285 }
1286 goto out;
1287 }
1288 slot = indirect_to_ptr(slot);
1289 shift -= RADIX_TREE_MAP_SHIFT;
1290 }
1291
1292 /* Bottom level: check items */
1293 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
1294 if (slot->slots[i] == item) {
1295 *found_index = index + i;
1296 index = 0;
1297 goto out;
1298 }
1299 }
1300 index += RADIX_TREE_MAP_SIZE;
1301out:
1302 return index;
1303}
1304
1305/**
1306 * radix_tree_locate_item - search through radix tree for item
1307 * @root: radix tree root
1308 * @item: item to be found
1309 *
1310 * Returns index where item was found, or -1 if not found.
1311 * Caller must hold no lock (since this time-consuming function needs
1312 * to be preemptible), and must check afterwards if item is still there.
1313 */
1314unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1315{
1316 struct radix_tree_node *node;
1317 unsigned long max_index;
1318 unsigned long cur_index = 0;
1319 unsigned long found_index = -1;
1320
1321 do {
1322 rcu_read_lock();
1323 node = rcu_dereference_raw(root->rnode);
1324 if (!radix_tree_is_indirect_ptr(node)) {
1325 rcu_read_unlock();
1326 if (node == item)
1327 found_index = 0;
1328 break;
1329 }
1330
1331 node = indirect_to_ptr(node);
1332 max_index = radix_tree_maxindex(node->path &
1333 RADIX_TREE_HEIGHT_MASK);
1334 if (cur_index > max_index) {
1335 rcu_read_unlock();
1336 break;
1337 }
1338
1339 cur_index = __locate(node, item, cur_index, &found_index);
1340 rcu_read_unlock();
1341 cond_resched();
1342 } while (cur_index != 0 && cur_index <= max_index);
1343
1344 return found_index;
1345}
1346#else
1347unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1348{
1349 return -1;
1350}
1351#endif /* CONFIG_SHMEM && CONFIG_SWAP */
1352
1353/**
1354 * radix_tree_shrink - shrink height of a radix tree to minimal
1355 * @root radix tree root
1356 */
1357static inline void radix_tree_shrink(struct radix_tree_root *root)
1358{
1359 /* try to shrink tree height */
1360 while (root->height > 0) {
1361 struct radix_tree_node *to_free = root->rnode;
1362 struct radix_tree_node *slot;
1363
1364 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
1365 to_free = indirect_to_ptr(to_free);
1366
1367 /*
1368 * The candidate node has more than one child, or its child
1369 * is not at the leftmost slot, or it is a multiorder entry,
1370 * we cannot shrink.
1371 */
1372 if (to_free->count != 1)
1373 break;
1374 slot = to_free->slots[0];
1375 if (!slot)
1376 break;
1377
1378 /*
1379 * We don't need rcu_assign_pointer(), since we are simply
1380 * moving the node from one part of the tree to another: if it
1381 * was safe to dereference the old pointer to it
1382 * (to_free->slots[0]), it will be safe to dereference the new
1383 * one (root->rnode) as far as dependent read barriers go.
1384 */
1385 if (root->height > 1) {
1386 if (!radix_tree_is_indirect_ptr(slot))
1387 break;
1388
1389 slot = indirect_to_ptr(slot);
1390 slot->parent = NULL;
1391 slot = ptr_to_indirect(slot);
1392 }
1393 root->rnode = slot;
1394 root->height--;
1395
1396 /*
1397 * We have a dilemma here. The node's slot[0] must not be
1398 * NULLed in case there are concurrent lookups expecting to
1399 * find the item. However if this was a bottom-level node,
1400 * then it may be subject to the slot pointer being visible
1401 * to callers dereferencing it. If item corresponding to
1402 * slot[0] is subsequently deleted, these callers would expect
1403 * their slot to become empty sooner or later.
1404 *
1405 * For example, lockless pagecache will look up a slot, deref
1406 * the page pointer, and if the page is 0 refcount it means it
1407 * was concurrently deleted from pagecache so try the deref
1408 * again. Fortunately there is already a requirement for logic
1409 * to retry the entire slot lookup -- the indirect pointer
1410 * problem (replacing direct root node with an indirect pointer
1411 * also results in a stale slot). So tag the slot as indirect
1412 * to force callers to retry.
1413 */
1414 if (root->height == 0)
1415 *((unsigned long *)&to_free->slots[0]) |=
1416 RADIX_TREE_INDIRECT_PTR;
1417
1418 radix_tree_node_free(to_free);
1419 }
1420}
1421
1422/**
1423 * __radix_tree_delete_node - try to free node after clearing a slot
1424 * @root: radix tree root
1425 * @node: node containing @index
1426 *
1427 * After clearing the slot at @index in @node from radix tree
1428 * rooted at @root, call this function to attempt freeing the
1429 * node and shrinking the tree.
1430 *
1431 * Returns %true if @node was freed, %false otherwise.
1432 */
1433bool __radix_tree_delete_node(struct radix_tree_root *root,
1434 struct radix_tree_node *node)
1435{
1436 bool deleted = false;
1437
1438 do {
1439 struct radix_tree_node *parent;
1440
1441 if (node->count) {
1442 if (node == indirect_to_ptr(root->rnode)) {
1443 radix_tree_shrink(root);
1444 if (root->height == 0)
1445 deleted = true;
1446 }
1447 return deleted;
1448 }
1449
1450 parent = node->parent;
1451 if (parent) {
1452 unsigned int offset;
1453
1454 offset = node->path >> RADIX_TREE_HEIGHT_SHIFT;
1455 parent->slots[offset] = NULL;
1456 parent->count--;
1457 } else {
1458 root_tag_clear_all(root);
1459 root->height = 0;
1460 root->rnode = NULL;
1461 }
1462
1463 radix_tree_node_free(node);
1464 deleted = true;
1465
1466 node = parent;
1467 } while (node);
1468
1469 return deleted;
1470}
1471
1472/**
1473 * radix_tree_delete_item - delete an item from a radix tree
1474 * @root: radix tree root
1475 * @index: index key
1476 * @item: expected item
1477 *
1478 * Remove @item at @index from the radix tree rooted at @root.
1479 *
1480 * Returns the address of the deleted item, or NULL if it was not present
1481 * or the entry at the given @index was not @item.
1482 */
1483void *radix_tree_delete_item(struct radix_tree_root *root,
1484 unsigned long index, void *item)
1485{
1486 struct radix_tree_node *node;
1487 unsigned int offset, i;
1488 void **slot;
1489 void *entry;
1490 int tag;
1491
1492 entry = __radix_tree_lookup(root, index, &node, &slot);
1493 if (!entry)
1494 return NULL;
1495
1496 if (item && entry != item)
1497 return NULL;
1498
1499 if (!node) {
1500 root_tag_clear_all(root);
1501 root->rnode = NULL;
1502 return entry;
1503 }
1504
1505 offset = index & RADIX_TREE_MAP_MASK;
1506
1507 /*
1508 * Clear all tags associated with the item to be deleted.
1509 * This way of doing it would be inefficient, but seldom is any set.
1510 */
1511 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1512 if (tag_get(node, tag, offset))
1513 radix_tree_tag_clear(root, index, tag);
1514 }
1515
1516 /* Delete any sibling slots pointing to this slot */
1517 for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
1518 if (node->slots[offset + i] != ptr_to_indirect(slot))
1519 break;
1520 node->slots[offset + i] = NULL;
1521 node->count--;
1522 }
1523 node->slots[offset] = NULL;
1524 node->count--;
1525
1526 __radix_tree_delete_node(root, node);
1527
1528 return entry;
1529}
1530EXPORT_SYMBOL(radix_tree_delete_item);
1531
1532/**
1533 * radix_tree_delete - delete an item from a radix tree
1534 * @root: radix tree root
1535 * @index: index key
1536 *
1537 * Remove the item at @index from the radix tree rooted at @root.
1538 *
1539 * Returns the address of the deleted item, or NULL if it was not present.
1540 */
1541void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1542{
1543 return radix_tree_delete_item(root, index, NULL);
1544}
1545EXPORT_SYMBOL(radix_tree_delete);
1546
1547/**
1548 * radix_tree_tagged - test whether any items in the tree are tagged
1549 * @root: radix tree root
1550 * @tag: tag to test
1551 */
1552int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1553{
1554 return root_tag_get(root, tag);
1555}
1556EXPORT_SYMBOL(radix_tree_tagged);
1557
1558static void
1559radix_tree_node_ctor(void *arg)
1560{
1561 struct radix_tree_node *node = arg;
1562
1563 memset(node, 0, sizeof(*node));
1564 INIT_LIST_HEAD(&node->private_list);
1565}
1566
1567static __init unsigned long __maxindex(unsigned int height)
1568{
1569 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1570 int shift = RADIX_TREE_INDEX_BITS - width;
1571
1572 if (shift < 0)
1573 return ~0UL;
1574 if (shift >= BITS_PER_LONG)
1575 return 0UL;
1576 return ~0UL >> shift;
1577}
1578
1579static __init void radix_tree_init_maxindex(void)
1580{
1581 unsigned int i;
1582
1583 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1584 height_to_maxindex[i] = __maxindex(i);
1585}
1586
1587static int radix_tree_callback(struct notifier_block *nfb,
1588 unsigned long action,
1589 void *hcpu)
1590{
1591 int cpu = (long)hcpu;
1592 struct radix_tree_preload *rtp;
1593 struct radix_tree_node *node;
1594
1595 /* Free per-cpu pool of perloaded nodes */
1596 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1597 rtp = &per_cpu(radix_tree_preloads, cpu);
1598 while (rtp->nr) {
1599 node = rtp->nodes;
1600 rtp->nodes = node->private_data;
1601 kmem_cache_free(radix_tree_node_cachep, node);
1602 rtp->nr--;
1603 }
1604 }
1605 return NOTIFY_OK;
1606}
1607
1608void __init radix_tree_init(void)
1609{
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 radix_tree_init_maxindex();
1615 hotcpu_notifier(radix_tree_callback, 0);
1616}