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