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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 * Copyright (C) 2016 Intel, Matthew Wilcox
8 * Copyright (C) 2016 Intel, Ross Zwisler
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License as
12 * published by the Free Software Foundation; either version 2, or (at
13 * your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful, but
16 * WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 */
24
25 #include <linux/errno.h>
26 #include <linux/init.h>
27 #include <linux/kernel.h>
28 #include <linux/export.h>
29 #include <linux/radix-tree.h>
30 #include <linux/percpu.h>
31 #include <linux/slab.h>
32 #include <linux/kmemleak.h>
33 #include <linux/notifier.h>
34 #include <linux/cpu.h>
35 #include <linux/string.h>
36 #include <linux/bitops.h>
37 #include <linux/rcupdate.h>
38 #include <linux/preempt.h> /* in_interrupt() */
39
40
41 /* Number of nodes in fully populated tree of given height */
42 static unsigned long height_to_maxnodes[RADIX_TREE_MAX_PATH + 1] __read_mostly;
43
44 /*
45 * Radix tree node cache.
46 */
47 static struct kmem_cache *radix_tree_node_cachep;
48
49 /*
50 * The radix tree is variable-height, so an insert operation not only has
51 * to build the branch to its corresponding item, it also has to build the
52 * branch to existing items if the size has to be increased (by
53 * radix_tree_extend).
54 *
55 * The worst case is a zero height tree with just a single item at index 0,
56 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
57 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
58 * Hence:
59 */
60 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
61
62 /*
63 * Per-cpu pool of preloaded nodes
64 */
65 struct radix_tree_preload {
66 unsigned nr;
67 /* nodes->private_data points to next preallocated node */
68 struct radix_tree_node *nodes;
69 };
70 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
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 node_to_entry(NULL)
78
79 #ifdef CONFIG_RADIX_TREE_MULTIORDER
80 /* Sibling slots point directly to another slot in the same node */
81 static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
82 {
83 void **ptr = node;
84 return (parent->slots <= ptr) &&
85 (ptr < parent->slots + RADIX_TREE_MAP_SIZE);
86 }
87 #else
88 static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
89 {
90 return false;
91 }
92 #endif
93
94 static inline unsigned long get_slot_offset(struct radix_tree_node *parent,
95 void **slot)
96 {
97 return slot - parent->slots;
98 }
99
100 static unsigned int radix_tree_descend(struct radix_tree_node *parent,
101 struct radix_tree_node **nodep, unsigned long index)
102 {
103 unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
104 void **entry = rcu_dereference_raw(parent->slots[offset]);
105
106 #ifdef CONFIG_RADIX_TREE_MULTIORDER
107 if (radix_tree_is_internal_node(entry)) {
108 if (is_sibling_entry(parent, entry)) {
109 void **sibentry = (void **) entry_to_node(entry);
110 offset = get_slot_offset(parent, sibentry);
111 entry = rcu_dereference_raw(*sibentry);
112 }
113 }
114 #endif
115
116 *nodep = (void *)entry;
117 return offset;
118 }
119
120 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
121 {
122 return root->gfp_mask & __GFP_BITS_MASK;
123 }
124
125 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
126 int offset)
127 {
128 __set_bit(offset, node->tags[tag]);
129 }
130
131 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
132 int offset)
133 {
134 __clear_bit(offset, node->tags[tag]);
135 }
136
137 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
138 int offset)
139 {
140 return test_bit(offset, node->tags[tag]);
141 }
142
143 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
144 {
145 root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
146 }
147
148 static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
149 {
150 root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
151 }
152
153 static inline void root_tag_clear_all(struct radix_tree_root *root)
154 {
155 root->gfp_mask &= __GFP_BITS_MASK;
156 }
157
158 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
159 {
160 return (__force int)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
161 }
162
163 static inline unsigned root_tags_get(struct radix_tree_root *root)
164 {
165 return (__force unsigned)root->gfp_mask >> __GFP_BITS_SHIFT;
166 }
167
168 /*
169 * Returns 1 if any slot in the node has this tag set.
170 * Otherwise returns 0.
171 */
172 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
173 {
174 unsigned idx;
175 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
176 if (node->tags[tag][idx])
177 return 1;
178 }
179 return 0;
180 }
181
182 /**
183 * radix_tree_find_next_bit - find the next set bit in a memory region
184 *
185 * @addr: The address to base the search on
186 * @size: The bitmap size in bits
187 * @offset: The bitnumber to start searching at
188 *
189 * Unrollable variant of find_next_bit() for constant size arrays.
190 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
191 * Returns next bit offset, or size if nothing found.
192 */
193 static __always_inline unsigned long
194 radix_tree_find_next_bit(const unsigned long *addr,
195 unsigned long size, unsigned long offset)
196 {
197 if (!__builtin_constant_p(size))
198 return find_next_bit(addr, size, offset);
199
200 if (offset < size) {
201 unsigned long tmp;
202
203 addr += offset / BITS_PER_LONG;
204 tmp = *addr >> (offset % BITS_PER_LONG);
205 if (tmp)
206 return __ffs(tmp) + offset;
207 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
208 while (offset < size) {
209 tmp = *++addr;
210 if (tmp)
211 return __ffs(tmp) + offset;
212 offset += BITS_PER_LONG;
213 }
214 }
215 return size;
216 }
217
218 #ifndef __KERNEL__
219 static void dump_node(struct radix_tree_node *node, unsigned long index)
220 {
221 unsigned long i;
222
223 pr_debug("radix node: %p offset %d tags %lx %lx %lx shift %d count %d parent %p\n",
224 node, node->offset,
225 node->tags[0][0], node->tags[1][0], node->tags[2][0],
226 node->shift, node->count, node->parent);
227
228 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
229 unsigned long first = index | (i << node->shift);
230 unsigned long last = first | ((1UL << node->shift) - 1);
231 void *entry = node->slots[i];
232 if (!entry)
233 continue;
234 if (is_sibling_entry(node, entry)) {
235 pr_debug("radix sblng %p offset %ld val %p indices %ld-%ld\n",
236 entry, i,
237 *(void **)entry_to_node(entry),
238 first, last);
239 } else if (!radix_tree_is_internal_node(entry)) {
240 pr_debug("radix entry %p offset %ld indices %ld-%ld\n",
241 entry, i, first, last);
242 } else {
243 dump_node(entry_to_node(entry), first);
244 }
245 }
246 }
247
248 /* For debug */
249 static void radix_tree_dump(struct radix_tree_root *root)
250 {
251 pr_debug("radix root: %p rnode %p tags %x\n",
252 root, root->rnode,
253 root->gfp_mask >> __GFP_BITS_SHIFT);
254 if (!radix_tree_is_internal_node(root->rnode))
255 return;
256 dump_node(entry_to_node(root->rnode), 0);
257 }
258 #endif
259
260 /*
261 * This assumes that the caller has performed appropriate preallocation, and
262 * that the caller has pinned this thread of control to the current CPU.
263 */
264 static struct radix_tree_node *
265 radix_tree_node_alloc(struct radix_tree_root *root)
266 {
267 struct radix_tree_node *ret = NULL;
268 gfp_t gfp_mask = root_gfp_mask(root);
269
270 /*
271 * Preload code isn't irq safe and it doesn't make sense to use
272 * preloading during an interrupt anyway as all the allocations have
273 * to be atomic. So just do normal allocation when in interrupt.
274 */
275 if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
276 struct radix_tree_preload *rtp;
277
278 /*
279 * Even if the caller has preloaded, try to allocate from the
280 * cache first for the new node to get accounted to the memory
281 * cgroup.
282 */
283 ret = kmem_cache_alloc(radix_tree_node_cachep,
284 gfp_mask | __GFP_NOWARN);
285 if (ret)
286 goto out;
287
288 /*
289 * Provided the caller has preloaded here, we will always
290 * succeed in getting a node here (and never reach
291 * kmem_cache_alloc)
292 */
293 rtp = this_cpu_ptr(&radix_tree_preloads);
294 if (rtp->nr) {
295 ret = rtp->nodes;
296 rtp->nodes = ret->private_data;
297 ret->private_data = NULL;
298 rtp->nr--;
299 }
300 /*
301 * Update the allocation stack trace as this is more useful
302 * for debugging.
303 */
304 kmemleak_update_trace(ret);
305 goto out;
306 }
307 ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
308 out:
309 BUG_ON(radix_tree_is_internal_node(ret));
310 return ret;
311 }
312
313 static void radix_tree_node_rcu_free(struct rcu_head *head)
314 {
315 struct radix_tree_node *node =
316 container_of(head, struct radix_tree_node, rcu_head);
317 int i;
318
319 /*
320 * must only free zeroed nodes into the slab. radix_tree_shrink
321 * can leave us with a non-NULL entry in the first slot, so clear
322 * that here to make sure.
323 */
324 for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
325 tag_clear(node, i, 0);
326
327 node->slots[0] = NULL;
328 node->count = 0;
329
330 kmem_cache_free(radix_tree_node_cachep, node);
331 }
332
333 static inline void
334 radix_tree_node_free(struct radix_tree_node *node)
335 {
336 call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
337 }
338
339 /*
340 * Load up this CPU's radix_tree_node buffer with sufficient objects to
341 * ensure that the addition of a single element in the tree cannot fail. On
342 * success, return zero, with preemption disabled. On error, return -ENOMEM
343 * with preemption not disabled.
344 *
345 * To make use of this facility, the radix tree must be initialised without
346 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
347 */
348 static int __radix_tree_preload(gfp_t gfp_mask, int nr)
349 {
350 struct radix_tree_preload *rtp;
351 struct radix_tree_node *node;
352 int ret = -ENOMEM;
353
354 /*
355 * Nodes preloaded by one cgroup can be be used by another cgroup, so
356 * they should never be accounted to any particular memory cgroup.
357 */
358 gfp_mask &= ~__GFP_ACCOUNT;
359
360 preempt_disable();
361 rtp = this_cpu_ptr(&radix_tree_preloads);
362 while (rtp->nr < nr) {
363 preempt_enable();
364 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
365 if (node == NULL)
366 goto out;
367 preempt_disable();
368 rtp = this_cpu_ptr(&radix_tree_preloads);
369 if (rtp->nr < nr) {
370 node->private_data = rtp->nodes;
371 rtp->nodes = node;
372 rtp->nr++;
373 } else {
374 kmem_cache_free(radix_tree_node_cachep, node);
375 }
376 }
377 ret = 0;
378 out:
379 return ret;
380 }
381
382 /*
383 * Load up this CPU's radix_tree_node buffer with sufficient objects to
384 * ensure that the addition of a single element in the tree cannot fail. On
385 * success, return zero, with preemption disabled. On error, return -ENOMEM
386 * with preemption not disabled.
387 *
388 * To make use of this facility, the radix tree must be initialised without
389 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
390 */
391 int radix_tree_preload(gfp_t gfp_mask)
392 {
393 /* Warn on non-sensical use... */
394 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
395 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
396 }
397 EXPORT_SYMBOL(radix_tree_preload);
398
399 /*
400 * The same as above function, except we don't guarantee preloading happens.
401 * We do it, if we decide it helps. On success, return zero with preemption
402 * disabled. On error, return -ENOMEM with preemption not disabled.
403 */
404 int radix_tree_maybe_preload(gfp_t gfp_mask)
405 {
406 if (gfpflags_allow_blocking(gfp_mask))
407 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
408 /* Preloading doesn't help anything with this gfp mask, skip it */
409 preempt_disable();
410 return 0;
411 }
412 EXPORT_SYMBOL(radix_tree_maybe_preload);
413
414 /*
415 * The same as function above, but preload number of nodes required to insert
416 * (1 << order) continuous naturally-aligned elements.
417 */
418 int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order)
419 {
420 unsigned long nr_subtrees;
421 int nr_nodes, subtree_height;
422
423 /* Preloading doesn't help anything with this gfp mask, skip it */
424 if (!gfpflags_allow_blocking(gfp_mask)) {
425 preempt_disable();
426 return 0;
427 }
428
429 /*
430 * Calculate number and height of fully populated subtrees it takes to
431 * store (1 << order) elements.
432 */
433 nr_subtrees = 1 << order;
434 for (subtree_height = 0; nr_subtrees > RADIX_TREE_MAP_SIZE;
435 subtree_height++)
436 nr_subtrees >>= RADIX_TREE_MAP_SHIFT;
437
438 /*
439 * The worst case is zero height tree with a single item at index 0 and
440 * then inserting items starting at ULONG_MAX - (1 << order).
441 *
442 * This requires RADIX_TREE_MAX_PATH nodes to build branch from root to
443 * 0-index item.
444 */
445 nr_nodes = RADIX_TREE_MAX_PATH;
446
447 /* Plus branch to fully populated subtrees. */
448 nr_nodes += RADIX_TREE_MAX_PATH - subtree_height;
449
450 /* Root node is shared. */
451 nr_nodes--;
452
453 /* Plus nodes required to build subtrees. */
454 nr_nodes += nr_subtrees * height_to_maxnodes[subtree_height];
455
456 return __radix_tree_preload(gfp_mask, nr_nodes);
457 }
458
459 /*
460 * The maximum index which can be stored in a radix tree
461 */
462 static inline unsigned long shift_maxindex(unsigned int shift)
463 {
464 return (RADIX_TREE_MAP_SIZE << shift) - 1;
465 }
466
467 static inline unsigned long node_maxindex(struct radix_tree_node *node)
468 {
469 return shift_maxindex(node->shift);
470 }
471
472 static unsigned radix_tree_load_root(struct radix_tree_root *root,
473 struct radix_tree_node **nodep, unsigned long *maxindex)
474 {
475 struct radix_tree_node *node = rcu_dereference_raw(root->rnode);
476
477 *nodep = node;
478
479 if (likely(radix_tree_is_internal_node(node))) {
480 node = entry_to_node(node);
481 *maxindex = node_maxindex(node);
482 return node->shift + RADIX_TREE_MAP_SHIFT;
483 }
484
485 *maxindex = 0;
486 return 0;
487 }
488
489 /*
490 * Extend a radix tree so it can store key @index.
491 */
492 static int radix_tree_extend(struct radix_tree_root *root,
493 unsigned long index, unsigned int shift)
494 {
495 struct radix_tree_node *slot;
496 unsigned int maxshift;
497 int tag;
498
499 /* Figure out what the shift should be. */
500 maxshift = shift;
501 while (index > shift_maxindex(maxshift))
502 maxshift += RADIX_TREE_MAP_SHIFT;
503
504 slot = root->rnode;
505 if (!slot)
506 goto out;
507
508 do {
509 struct radix_tree_node *node = radix_tree_node_alloc(root);
510
511 if (!node)
512 return -ENOMEM;
513
514 /* Propagate the aggregated tag info into the new root */
515 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
516 if (root_tag_get(root, tag))
517 tag_set(node, tag, 0);
518 }
519
520 BUG_ON(shift > BITS_PER_LONG);
521 node->shift = shift;
522 node->offset = 0;
523 node->count = 1;
524 node->parent = NULL;
525 if (radix_tree_is_internal_node(slot))
526 entry_to_node(slot)->parent = node;
527 node->slots[0] = slot;
528 slot = node_to_entry(node);
529 rcu_assign_pointer(root->rnode, slot);
530 shift += RADIX_TREE_MAP_SHIFT;
531 } while (shift <= maxshift);
532 out:
533 return maxshift + RADIX_TREE_MAP_SHIFT;
534 }
535
536 /**
537 * __radix_tree_create - create a slot in a radix tree
538 * @root: radix tree root
539 * @index: index key
540 * @order: index occupies 2^order aligned slots
541 * @nodep: returns node
542 * @slotp: returns slot
543 *
544 * Create, if necessary, and return the node and slot for an item
545 * at position @index in the radix tree @root.
546 *
547 * Until there is more than one item in the tree, no nodes are
548 * allocated and @root->rnode is used as a direct slot instead of
549 * pointing to a node, in which case *@nodep will be NULL.
550 *
551 * Returns -ENOMEM, or 0 for success.
552 */
553 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
554 unsigned order, struct radix_tree_node **nodep,
555 void ***slotp)
556 {
557 struct radix_tree_node *node = NULL, *child;
558 void **slot = (void **)&root->rnode;
559 unsigned long maxindex;
560 unsigned int shift, offset = 0;
561 unsigned long max = index | ((1UL << order) - 1);
562
563 shift = radix_tree_load_root(root, &child, &maxindex);
564
565 /* Make sure the tree is high enough. */
566 if (max > maxindex) {
567 int error = radix_tree_extend(root, max, shift);
568 if (error < 0)
569 return error;
570 shift = error;
571 child = root->rnode;
572 if (order == shift)
573 shift += RADIX_TREE_MAP_SHIFT;
574 }
575
576 while (shift > order) {
577 shift -= RADIX_TREE_MAP_SHIFT;
578 if (child == NULL) {
579 /* Have to add a child node. */
580 child = radix_tree_node_alloc(root);
581 if (!child)
582 return -ENOMEM;
583 child->shift = shift;
584 child->offset = offset;
585 child->parent = node;
586 rcu_assign_pointer(*slot, node_to_entry(child));
587 if (node)
588 node->count++;
589 } else if (!radix_tree_is_internal_node(child))
590 break;
591
592 /* Go a level down */
593 node = entry_to_node(child);
594 offset = radix_tree_descend(node, &child, index);
595 slot = &node->slots[offset];
596 }
597
598 #ifdef CONFIG_RADIX_TREE_MULTIORDER
599 /* Insert pointers to the canonical entry */
600 if (order > shift) {
601 unsigned i, n = 1 << (order - shift);
602 offset = offset & ~(n - 1);
603 slot = &node->slots[offset];
604 child = node_to_entry(slot);
605 for (i = 0; i < n; i++) {
606 if (slot[i])
607 return -EEXIST;
608 }
609
610 for (i = 1; i < n; i++) {
611 rcu_assign_pointer(slot[i], child);
612 node->count++;
613 }
614 }
615 #endif
616
617 if (nodep)
618 *nodep = node;
619 if (slotp)
620 *slotp = slot;
621 return 0;
622 }
623
624 /**
625 * __radix_tree_insert - insert into a radix tree
626 * @root: radix tree root
627 * @index: index key
628 * @order: key covers the 2^order indices around index
629 * @item: item to insert
630 *
631 * Insert an item into the radix tree at position @index.
632 */
633 int __radix_tree_insert(struct radix_tree_root *root, unsigned long index,
634 unsigned order, void *item)
635 {
636 struct radix_tree_node *node;
637 void **slot;
638 int error;
639
640 BUG_ON(radix_tree_is_internal_node(item));
641
642 error = __radix_tree_create(root, index, order, &node, &slot);
643 if (error)
644 return error;
645 if (*slot != NULL)
646 return -EEXIST;
647 rcu_assign_pointer(*slot, item);
648
649 if (node) {
650 unsigned offset = get_slot_offset(node, slot);
651 node->count++;
652 BUG_ON(tag_get(node, 0, offset));
653 BUG_ON(tag_get(node, 1, offset));
654 BUG_ON(tag_get(node, 2, offset));
655 } else {
656 BUG_ON(root_tags_get(root));
657 }
658
659 return 0;
660 }
661 EXPORT_SYMBOL(__radix_tree_insert);
662
663 /**
664 * __radix_tree_lookup - lookup an item in a radix tree
665 * @root: radix tree root
666 * @index: index key
667 * @nodep: returns node
668 * @slotp: returns slot
669 *
670 * Lookup and return the item at position @index in the radix
671 * tree @root.
672 *
673 * Until there is more than one item in the tree, no nodes are
674 * allocated and @root->rnode is used as a direct slot instead of
675 * pointing to a node, in which case *@nodep will be NULL.
676 */
677 void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
678 struct radix_tree_node **nodep, void ***slotp)
679 {
680 struct radix_tree_node *node, *parent;
681 unsigned long maxindex;
682 void **slot;
683
684 restart:
685 parent = NULL;
686 slot = (void **)&root->rnode;
687 radix_tree_load_root(root, &node, &maxindex);
688 if (index > maxindex)
689 return NULL;
690
691 while (radix_tree_is_internal_node(node)) {
692 unsigned offset;
693
694 if (node == RADIX_TREE_RETRY)
695 goto restart;
696 parent = entry_to_node(node);
697 offset = radix_tree_descend(parent, &node, index);
698 slot = parent->slots + offset;
699 }
700
701 if (nodep)
702 *nodep = parent;
703 if (slotp)
704 *slotp = slot;
705 return node;
706 }
707
708 /**
709 * radix_tree_lookup_slot - lookup a slot in a radix tree
710 * @root: radix tree root
711 * @index: index key
712 *
713 * Returns: the slot corresponding to the position @index in the
714 * radix tree @root. This is useful for update-if-exists operations.
715 *
716 * This function can be called under rcu_read_lock iff the slot is not
717 * modified by radix_tree_replace_slot, otherwise it must be called
718 * exclusive from other writers. Any dereference of the slot must be done
719 * using radix_tree_deref_slot.
720 */
721 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
722 {
723 void **slot;
724
725 if (!__radix_tree_lookup(root, index, NULL, &slot))
726 return NULL;
727 return slot;
728 }
729 EXPORT_SYMBOL(radix_tree_lookup_slot);
730
731 /**
732 * radix_tree_lookup - perform lookup operation on a radix tree
733 * @root: radix tree root
734 * @index: index key
735 *
736 * Lookup the item at the position @index in the radix tree @root.
737 *
738 * This function can be called under rcu_read_lock, however the caller
739 * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
740 * them safely). No RCU barriers are required to access or modify the
741 * returned item, however.
742 */
743 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
744 {
745 return __radix_tree_lookup(root, index, NULL, NULL);
746 }
747 EXPORT_SYMBOL(radix_tree_lookup);
748
749 /**
750 * radix_tree_tag_set - set a tag on a radix tree node
751 * @root: radix tree root
752 * @index: index key
753 * @tag: tag index
754 *
755 * Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
756 * corresponding to @index in the radix tree. From
757 * the root all the way down to the leaf node.
758 *
759 * Returns the address of the tagged item. Setting a tag on a not-present
760 * item is a bug.
761 */
762 void *radix_tree_tag_set(struct radix_tree_root *root,
763 unsigned long index, unsigned int tag)
764 {
765 struct radix_tree_node *node, *parent;
766 unsigned long maxindex;
767
768 radix_tree_load_root(root, &node, &maxindex);
769 BUG_ON(index > maxindex);
770
771 while (radix_tree_is_internal_node(node)) {
772 unsigned offset;
773
774 parent = entry_to_node(node);
775 offset = radix_tree_descend(parent, &node, index);
776 BUG_ON(!node);
777
778 if (!tag_get(parent, tag, offset))
779 tag_set(parent, tag, offset);
780 }
781
782 /* set the root's tag bit */
783 if (!root_tag_get(root, tag))
784 root_tag_set(root, tag);
785
786 return node;
787 }
788 EXPORT_SYMBOL(radix_tree_tag_set);
789
790 static void node_tag_clear(struct radix_tree_root *root,
791 struct radix_tree_node *node,
792 unsigned int tag, unsigned int offset)
793 {
794 while (node) {
795 if (!tag_get(node, tag, offset))
796 return;
797 tag_clear(node, tag, offset);
798 if (any_tag_set(node, tag))
799 return;
800
801 offset = node->offset;
802 node = node->parent;
803 }
804
805 /* clear the root's tag bit */
806 if (root_tag_get(root, tag))
807 root_tag_clear(root, tag);
808 }
809
810 /**
811 * radix_tree_tag_clear - clear a tag on a radix tree node
812 * @root: radix tree root
813 * @index: index key
814 * @tag: tag index
815 *
816 * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
817 * corresponding to @index in the radix tree. If this causes
818 * the leaf node to have no tags set then clear the tag in the
819 * next-to-leaf node, etc.
820 *
821 * Returns the address of the tagged item on success, else NULL. ie:
822 * has the same return value and semantics as radix_tree_lookup().
823 */
824 void *radix_tree_tag_clear(struct radix_tree_root *root,
825 unsigned long index, unsigned int tag)
826 {
827 struct radix_tree_node *node, *parent;
828 unsigned long maxindex;
829 int uninitialized_var(offset);
830
831 radix_tree_load_root(root, &node, &maxindex);
832 if (index > maxindex)
833 return NULL;
834
835 parent = NULL;
836
837 while (radix_tree_is_internal_node(node)) {
838 parent = entry_to_node(node);
839 offset = radix_tree_descend(parent, &node, index);
840 }
841
842 if (node)
843 node_tag_clear(root, parent, tag, offset);
844
845 return node;
846 }
847 EXPORT_SYMBOL(radix_tree_tag_clear);
848
849 /**
850 * radix_tree_tag_get - get a tag on a radix tree node
851 * @root: radix tree root
852 * @index: index key
853 * @tag: tag index (< RADIX_TREE_MAX_TAGS)
854 *
855 * Return values:
856 *
857 * 0: tag not present or not set
858 * 1: tag set
859 *
860 * Note that the return value of this function may not be relied on, even if
861 * the RCU lock is held, unless tag modification and node deletion are excluded
862 * from concurrency.
863 */
864 int radix_tree_tag_get(struct radix_tree_root *root,
865 unsigned long index, unsigned int tag)
866 {
867 struct radix_tree_node *node, *parent;
868 unsigned long maxindex;
869
870 if (!root_tag_get(root, tag))
871 return 0;
872
873 radix_tree_load_root(root, &node, &maxindex);
874 if (index > maxindex)
875 return 0;
876 if (node == NULL)
877 return 0;
878
879 while (radix_tree_is_internal_node(node)) {
880 unsigned offset;
881
882 parent = entry_to_node(node);
883 offset = radix_tree_descend(parent, &node, index);
884
885 if (!node)
886 return 0;
887 if (!tag_get(parent, tag, offset))
888 return 0;
889 if (node == RADIX_TREE_RETRY)
890 break;
891 }
892
893 return 1;
894 }
895 EXPORT_SYMBOL(radix_tree_tag_get);
896
897 static inline void __set_iter_shift(struct radix_tree_iter *iter,
898 unsigned int shift)
899 {
900 #ifdef CONFIG_RADIX_TREE_MULTIORDER
901 iter->shift = shift;
902 #endif
903 }
904
905 /**
906 * radix_tree_next_chunk - find next chunk of slots for iteration
907 *
908 * @root: radix tree root
909 * @iter: iterator state
910 * @flags: RADIX_TREE_ITER_* flags and tag index
911 * Returns: pointer to chunk first slot, or NULL if iteration is over
912 */
913 void **radix_tree_next_chunk(struct radix_tree_root *root,
914 struct radix_tree_iter *iter, unsigned flags)
915 {
916 unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
917 struct radix_tree_node *node, *child;
918 unsigned long index, offset, maxindex;
919
920 if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
921 return NULL;
922
923 /*
924 * Catch next_index overflow after ~0UL. iter->index never overflows
925 * during iterating; it can be zero only at the beginning.
926 * And we cannot overflow iter->next_index in a single step,
927 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
928 *
929 * This condition also used by radix_tree_next_slot() to stop
930 * contiguous iterating, and forbid swithing to the next chunk.
931 */
932 index = iter->next_index;
933 if (!index && iter->index)
934 return NULL;
935
936 restart:
937 radix_tree_load_root(root, &child, &maxindex);
938 if (index > maxindex)
939 return NULL;
940 if (!child)
941 return NULL;
942
943 if (!radix_tree_is_internal_node(child)) {
944 /* Single-slot tree */
945 iter->index = index;
946 iter->next_index = maxindex + 1;
947 iter->tags = 1;
948 __set_iter_shift(iter, 0);
949 return (void **)&root->rnode;
950 }
951
952 do {
953 node = entry_to_node(child);
954 offset = radix_tree_descend(node, &child, index);
955
956 if ((flags & RADIX_TREE_ITER_TAGGED) ?
957 !tag_get(node, tag, offset) : !child) {
958 /* Hole detected */
959 if (flags & RADIX_TREE_ITER_CONTIG)
960 return NULL;
961
962 if (flags & RADIX_TREE_ITER_TAGGED)
963 offset = radix_tree_find_next_bit(
964 node->tags[tag],
965 RADIX_TREE_MAP_SIZE,
966 offset + 1);
967 else
968 while (++offset < RADIX_TREE_MAP_SIZE) {
969 void *slot = node->slots[offset];
970 if (is_sibling_entry(node, slot))
971 continue;
972 if (slot)
973 break;
974 }
975 index &= ~node_maxindex(node);
976 index += offset << node->shift;
977 /* Overflow after ~0UL */
978 if (!index)
979 return NULL;
980 if (offset == RADIX_TREE_MAP_SIZE)
981 goto restart;
982 child = rcu_dereference_raw(node->slots[offset]);
983 }
984
985 if ((child == NULL) || (child == RADIX_TREE_RETRY))
986 goto restart;
987 } while (radix_tree_is_internal_node(child));
988
989 /* Update the iterator state */
990 iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
991 iter->next_index = (index | node_maxindex(node)) + 1;
992 __set_iter_shift(iter, node->shift);
993
994 /* Construct iter->tags bit-mask from node->tags[tag] array */
995 if (flags & RADIX_TREE_ITER_TAGGED) {
996 unsigned tag_long, tag_bit;
997
998 tag_long = offset / BITS_PER_LONG;
999 tag_bit = offset % BITS_PER_LONG;
1000 iter->tags = node->tags[tag][tag_long] >> tag_bit;
1001 /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1002 if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1003 /* Pick tags from next element */
1004 if (tag_bit)
1005 iter->tags |= node->tags[tag][tag_long + 1] <<
1006 (BITS_PER_LONG - tag_bit);
1007 /* Clip chunk size, here only BITS_PER_LONG tags */
1008 iter->next_index = index + BITS_PER_LONG;
1009 }
1010 }
1011
1012 return node->slots + offset;
1013 }
1014 EXPORT_SYMBOL(radix_tree_next_chunk);
1015
1016 /**
1017 * radix_tree_range_tag_if_tagged - for each item in given range set given
1018 * tag if item has another tag set
1019 * @root: radix tree root
1020 * @first_indexp: pointer to a starting index of a range to scan
1021 * @last_index: last index of a range to scan
1022 * @nr_to_tag: maximum number items to tag
1023 * @iftag: tag index to test
1024 * @settag: tag index to set if tested tag is set
1025 *
1026 * This function scans range of radix tree from first_index to last_index
1027 * (inclusive). For each item in the range if iftag is set, the function sets
1028 * also settag. The function stops either after tagging nr_to_tag items or
1029 * after reaching last_index.
1030 *
1031 * The tags must be set from the leaf level only and propagated back up the
1032 * path to the root. We must do this so that we resolve the full path before
1033 * setting any tags on intermediate nodes. If we set tags as we descend, then
1034 * we can get to the leaf node and find that the index that has the iftag
1035 * set is outside the range we are scanning. This reults in dangling tags and
1036 * can lead to problems with later tag operations (e.g. livelocks on lookups).
1037 *
1038 * The function returns the number of leaves where the tag was set and sets
1039 * *first_indexp to the first unscanned index.
1040 * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
1041 * be prepared to handle that.
1042 */
1043 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
1044 unsigned long *first_indexp, unsigned long last_index,
1045 unsigned long nr_to_tag,
1046 unsigned int iftag, unsigned int settag)
1047 {
1048 struct radix_tree_node *parent, *node, *child;
1049 unsigned long maxindex;
1050 unsigned long tagged = 0;
1051 unsigned long index = *first_indexp;
1052
1053 radix_tree_load_root(root, &child, &maxindex);
1054 last_index = min(last_index, maxindex);
1055 if (index > last_index)
1056 return 0;
1057 if (!nr_to_tag)
1058 return 0;
1059 if (!root_tag_get(root, iftag)) {
1060 *first_indexp = last_index + 1;
1061 return 0;
1062 }
1063 if (!radix_tree_is_internal_node(child)) {
1064 *first_indexp = last_index + 1;
1065 root_tag_set(root, settag);
1066 return 1;
1067 }
1068
1069 node = entry_to_node(child);
1070
1071 for (;;) {
1072 unsigned offset = radix_tree_descend(node, &child, index);
1073 if (!child)
1074 goto next;
1075 if (!tag_get(node, iftag, offset))
1076 goto next;
1077 /* Sibling slots never have tags set on them */
1078 if (radix_tree_is_internal_node(child)) {
1079 node = entry_to_node(child);
1080 continue;
1081 }
1082
1083 /* tag the leaf */
1084 tagged++;
1085 tag_set(node, settag, offset);
1086
1087 /* walk back up the path tagging interior nodes */
1088 parent = node;
1089 for (;;) {
1090 offset = parent->offset;
1091 parent = parent->parent;
1092 if (!parent)
1093 break;
1094 /* stop if we find a node with the tag already set */
1095 if (tag_get(parent, settag, offset))
1096 break;
1097 tag_set(parent, settag, offset);
1098 }
1099 next:
1100 /* Go to next entry in node */
1101 index = ((index >> node->shift) + 1) << node->shift;
1102 /* Overflow can happen when last_index is ~0UL... */
1103 if (index > last_index || !index)
1104 break;
1105 offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
1106 while (offset == 0) {
1107 /*
1108 * We've fully scanned this node. Go up. Because
1109 * last_index is guaranteed to be in the tree, what
1110 * we do below cannot wander astray.
1111 */
1112 node = node->parent;
1113 offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
1114 }
1115 if (is_sibling_entry(node, node->slots[offset]))
1116 goto next;
1117 if (tagged >= nr_to_tag)
1118 break;
1119 }
1120 /*
1121 * We need not to tag the root tag if there is no tag which is set with
1122 * settag within the range from *first_indexp to last_index.
1123 */
1124 if (tagged > 0)
1125 root_tag_set(root, settag);
1126 *first_indexp = index;
1127
1128 return tagged;
1129 }
1130 EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
1131
1132 /**
1133 * radix_tree_gang_lookup - perform multiple lookup on a radix tree
1134 * @root: radix tree root
1135 * @results: where the results of the lookup are placed
1136 * @first_index: start the lookup from this key
1137 * @max_items: place up to this many items at *results
1138 *
1139 * Performs an index-ascending scan of the tree for present items. Places
1140 * them at *@results and returns the number of items which were placed at
1141 * *@results.
1142 *
1143 * The implementation is naive.
1144 *
1145 * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1146 * rcu_read_lock. In this case, rather than the returned results being
1147 * an atomic snapshot of the tree at a single point in time, the
1148 * semantics of an RCU protected gang lookup are as though multiple
1149 * radix_tree_lookups have been issued in individual locks, and results
1150 * stored in 'results'.
1151 */
1152 unsigned int
1153 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
1154 unsigned long first_index, unsigned int max_items)
1155 {
1156 struct radix_tree_iter iter;
1157 void **slot;
1158 unsigned int ret = 0;
1159
1160 if (unlikely(!max_items))
1161 return 0;
1162
1163 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1164 results[ret] = rcu_dereference_raw(*slot);
1165 if (!results[ret])
1166 continue;
1167 if (radix_tree_is_internal_node(results[ret])) {
1168 slot = radix_tree_iter_retry(&iter);
1169 continue;
1170 }
1171 if (++ret == max_items)
1172 break;
1173 }
1174
1175 return ret;
1176 }
1177 EXPORT_SYMBOL(radix_tree_gang_lookup);
1178
1179 /**
1180 * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1181 * @root: radix tree root
1182 * @results: where the results of the lookup are placed
1183 * @indices: where their indices should be placed (but usually NULL)
1184 * @first_index: start the lookup from this key
1185 * @max_items: place up to this many items at *results
1186 *
1187 * Performs an index-ascending scan of the tree for present items. Places
1188 * their slots at *@results and returns the number of items which were
1189 * placed at *@results.
1190 *
1191 * The implementation is naive.
1192 *
1193 * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1194 * be dereferenced with radix_tree_deref_slot, and if using only RCU
1195 * protection, radix_tree_deref_slot may fail requiring a retry.
1196 */
1197 unsigned int
1198 radix_tree_gang_lookup_slot(struct radix_tree_root *root,
1199 void ***results, unsigned long *indices,
1200 unsigned long first_index, unsigned int max_items)
1201 {
1202 struct radix_tree_iter iter;
1203 void **slot;
1204 unsigned int ret = 0;
1205
1206 if (unlikely(!max_items))
1207 return 0;
1208
1209 radix_tree_for_each_slot(slot, root, &iter, first_index) {
1210 results[ret] = slot;
1211 if (indices)
1212 indices[ret] = iter.index;
1213 if (++ret == max_items)
1214 break;
1215 }
1216
1217 return ret;
1218 }
1219 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1220
1221 /**
1222 * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1223 * based on a tag
1224 * @root: radix tree root
1225 * @results: where the results of the lookup are placed
1226 * @first_index: start the lookup from this key
1227 * @max_items: place up to this many items at *results
1228 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1229 *
1230 * Performs an index-ascending scan of the tree for present items which
1231 * have the tag indexed by @tag set. Places the items at *@results and
1232 * returns the number of items which were placed at *@results.
1233 */
1234 unsigned int
1235 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
1236 unsigned long first_index, unsigned int max_items,
1237 unsigned int tag)
1238 {
1239 struct radix_tree_iter iter;
1240 void **slot;
1241 unsigned int ret = 0;
1242
1243 if (unlikely(!max_items))
1244 return 0;
1245
1246 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1247 results[ret] = rcu_dereference_raw(*slot);
1248 if (!results[ret])
1249 continue;
1250 if (radix_tree_is_internal_node(results[ret])) {
1251 slot = radix_tree_iter_retry(&iter);
1252 continue;
1253 }
1254 if (++ret == max_items)
1255 break;
1256 }
1257
1258 return ret;
1259 }
1260 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1261
1262 /**
1263 * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1264 * radix tree based on a tag
1265 * @root: radix tree root
1266 * @results: where the results of the lookup are placed
1267 * @first_index: start the lookup from this key
1268 * @max_items: place up to this many items at *results
1269 * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
1270 *
1271 * Performs an index-ascending scan of the tree for present items which
1272 * have the tag indexed by @tag set. Places the slots at *@results and
1273 * returns the number of slots which were placed at *@results.
1274 */
1275 unsigned int
1276 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
1277 unsigned long first_index, unsigned int max_items,
1278 unsigned int tag)
1279 {
1280 struct radix_tree_iter iter;
1281 void **slot;
1282 unsigned int ret = 0;
1283
1284 if (unlikely(!max_items))
1285 return 0;
1286
1287 radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1288 results[ret] = slot;
1289 if (++ret == max_items)
1290 break;
1291 }
1292
1293 return ret;
1294 }
1295 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1296
1297 #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
1298 #include <linux/sched.h> /* for cond_resched() */
1299
1300 struct locate_info {
1301 unsigned long found_index;
1302 bool stop;
1303 };
1304
1305 /*
1306 * This linear search is at present only useful to shmem_unuse_inode().
1307 */
1308 static unsigned long __locate(struct radix_tree_node *slot, void *item,
1309 unsigned long index, struct locate_info *info)
1310 {
1311 unsigned long i;
1312
1313 do {
1314 unsigned int shift = slot->shift;
1315
1316 for (i = (index >> shift) & RADIX_TREE_MAP_MASK;
1317 i < RADIX_TREE_MAP_SIZE;
1318 i++, index += (1UL << shift)) {
1319 struct radix_tree_node *node =
1320 rcu_dereference_raw(slot->slots[i]);
1321 if (node == RADIX_TREE_RETRY)
1322 goto out;
1323 if (!radix_tree_is_internal_node(node)) {
1324 if (node == item) {
1325 info->found_index = index;
1326 info->stop = true;
1327 goto out;
1328 }
1329 continue;
1330 }
1331 node = entry_to_node(node);
1332 if (is_sibling_entry(slot, node))
1333 continue;
1334 slot = node;
1335 break;
1336 }
1337 } while (i < RADIX_TREE_MAP_SIZE);
1338
1339 out:
1340 if ((index == 0) && (i == RADIX_TREE_MAP_SIZE))
1341 info->stop = true;
1342 return index;
1343 }
1344
1345 /**
1346 * radix_tree_locate_item - search through radix tree for item
1347 * @root: radix tree root
1348 * @item: item to be found
1349 *
1350 * Returns index where item was found, or -1 if not found.
1351 * Caller must hold no lock (since this time-consuming function needs
1352 * to be preemptible), and must check afterwards if item is still there.
1353 */
1354 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1355 {
1356 struct radix_tree_node *node;
1357 unsigned long max_index;
1358 unsigned long cur_index = 0;
1359 struct locate_info info = {
1360 .found_index = -1,
1361 .stop = false,
1362 };
1363
1364 do {
1365 rcu_read_lock();
1366 node = rcu_dereference_raw(root->rnode);
1367 if (!radix_tree_is_internal_node(node)) {
1368 rcu_read_unlock();
1369 if (node == item)
1370 info.found_index = 0;
1371 break;
1372 }
1373
1374 node = entry_to_node(node);
1375
1376 max_index = node_maxindex(node);
1377 if (cur_index > max_index) {
1378 rcu_read_unlock();
1379 break;
1380 }
1381
1382 cur_index = __locate(node, item, cur_index, &info);
1383 rcu_read_unlock();
1384 cond_resched();
1385 } while (!info.stop && cur_index <= max_index);
1386
1387 return info.found_index;
1388 }
1389 #else
1390 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
1391 {
1392 return -1;
1393 }
1394 #endif /* CONFIG_SHMEM && CONFIG_SWAP */
1395
1396 /**
1397 * radix_tree_shrink - shrink radix tree to minimum height
1398 * @root radix tree root
1399 */
1400 static inline bool radix_tree_shrink(struct radix_tree_root *root)
1401 {
1402 bool shrunk = false;
1403
1404 for (;;) {
1405 struct radix_tree_node *node = root->rnode;
1406 struct radix_tree_node *child;
1407
1408 if (!radix_tree_is_internal_node(node))
1409 break;
1410 node = entry_to_node(node);
1411
1412 /*
1413 * The candidate node has more than one child, or its child
1414 * is not at the leftmost slot, or the child is a multiorder
1415 * entry, we cannot shrink.
1416 */
1417 if (node->count != 1)
1418 break;
1419 child = node->slots[0];
1420 if (!child)
1421 break;
1422 if (!radix_tree_is_internal_node(child) && node->shift)
1423 break;
1424
1425 if (radix_tree_is_internal_node(child))
1426 entry_to_node(child)->parent = NULL;
1427
1428 /*
1429 * We don't need rcu_assign_pointer(), since we are simply
1430 * moving the node from one part of the tree to another: if it
1431 * was safe to dereference the old pointer to it
1432 * (node->slots[0]), it will be safe to dereference the new
1433 * one (root->rnode) as far as dependent read barriers go.
1434 */
1435 root->rnode = child;
1436
1437 /*
1438 * We have a dilemma here. The node's slot[0] must not be
1439 * NULLed in case there are concurrent lookups expecting to
1440 * find the item. However if this was a bottom-level node,
1441 * then it may be subject to the slot pointer being visible
1442 * to callers dereferencing it. If item corresponding to
1443 * slot[0] is subsequently deleted, these callers would expect
1444 * their slot to become empty sooner or later.
1445 *
1446 * For example, lockless pagecache will look up a slot, deref
1447 * the page pointer, and if the page has 0 refcount it means it
1448 * was concurrently deleted from pagecache so try the deref
1449 * again. Fortunately there is already a requirement for logic
1450 * to retry the entire slot lookup -- the indirect pointer
1451 * problem (replacing direct root node with an indirect pointer
1452 * also results in a stale slot). So tag the slot as indirect
1453 * to force callers to retry.
1454 */
1455 if (!radix_tree_is_internal_node(child))
1456 node->slots[0] = RADIX_TREE_RETRY;
1457
1458 radix_tree_node_free(node);
1459 shrunk = true;
1460 }
1461
1462 return shrunk;
1463 }
1464
1465 /**
1466 * __radix_tree_delete_node - try to free node after clearing a slot
1467 * @root: radix tree root
1468 * @node: node containing @index
1469 *
1470 * After clearing the slot at @index in @node from radix tree
1471 * rooted at @root, call this function to attempt freeing the
1472 * node and shrinking the tree.
1473 *
1474 * Returns %true if @node was freed, %false otherwise.
1475 */
1476 bool __radix_tree_delete_node(struct radix_tree_root *root,
1477 struct radix_tree_node *node)
1478 {
1479 bool deleted = false;
1480
1481 do {
1482 struct radix_tree_node *parent;
1483
1484 if (node->count) {
1485 if (node == entry_to_node(root->rnode))
1486 deleted |= radix_tree_shrink(root);
1487 return deleted;
1488 }
1489
1490 parent = node->parent;
1491 if (parent) {
1492 parent->slots[node->offset] = NULL;
1493 parent->count--;
1494 } else {
1495 root_tag_clear_all(root);
1496 root->rnode = NULL;
1497 }
1498
1499 radix_tree_node_free(node);
1500 deleted = true;
1501
1502 node = parent;
1503 } while (node);
1504
1505 return deleted;
1506 }
1507
1508 static inline void delete_sibling_entries(struct radix_tree_node *node,
1509 void *ptr, unsigned offset)
1510 {
1511 #ifdef CONFIG_RADIX_TREE_MULTIORDER
1512 int i;
1513 for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
1514 if (node->slots[offset + i] != ptr)
1515 break;
1516 node->slots[offset + i] = NULL;
1517 node->count--;
1518 }
1519 #endif
1520 }
1521
1522 /**
1523 * radix_tree_delete_item - delete an item from a radix tree
1524 * @root: radix tree root
1525 * @index: index key
1526 * @item: expected item
1527 *
1528 * Remove @item at @index from the radix tree rooted at @root.
1529 *
1530 * Returns the address of the deleted item, or NULL if it was not present
1531 * or the entry at the given @index was not @item.
1532 */
1533 void *radix_tree_delete_item(struct radix_tree_root *root,
1534 unsigned long index, void *item)
1535 {
1536 struct radix_tree_node *node;
1537 unsigned int offset;
1538 void **slot;
1539 void *entry;
1540 int tag;
1541
1542 entry = __radix_tree_lookup(root, index, &node, &slot);
1543 if (!entry)
1544 return NULL;
1545
1546 if (item && entry != item)
1547 return NULL;
1548
1549 if (!node) {
1550 root_tag_clear_all(root);
1551 root->rnode = NULL;
1552 return entry;
1553 }
1554
1555 offset = get_slot_offset(node, slot);
1556
1557 /* Clear all tags associated with the item to be deleted. */
1558 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1559 node_tag_clear(root, node, tag, offset);
1560
1561 delete_sibling_entries(node, node_to_entry(slot), offset);
1562 node->slots[offset] = NULL;
1563 node->count--;
1564
1565 __radix_tree_delete_node(root, node);
1566
1567 return entry;
1568 }
1569 EXPORT_SYMBOL(radix_tree_delete_item);
1570
1571 /**
1572 * radix_tree_delete - delete an item from a radix tree
1573 * @root: radix tree root
1574 * @index: index key
1575 *
1576 * Remove the item at @index from the radix tree rooted at @root.
1577 *
1578 * Returns the address of the deleted item, or NULL if it was not present.
1579 */
1580 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1581 {
1582 return radix_tree_delete_item(root, index, NULL);
1583 }
1584 EXPORT_SYMBOL(radix_tree_delete);
1585
1586 struct radix_tree_node *radix_tree_replace_clear_tags(
1587 struct radix_tree_root *root,
1588 unsigned long index, void *entry)
1589 {
1590 struct radix_tree_node *node;
1591 void **slot;
1592
1593 __radix_tree_lookup(root, index, &node, &slot);
1594
1595 if (node) {
1596 unsigned int tag, offset = get_slot_offset(node, slot);
1597 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1598 node_tag_clear(root, node, tag, offset);
1599 } else {
1600 /* Clear root node tags */
1601 root->gfp_mask &= __GFP_BITS_MASK;
1602 }
1603
1604 radix_tree_replace_slot(slot, entry);
1605 return node;
1606 }
1607
1608 /**
1609 * radix_tree_tagged - test whether any items in the tree are tagged
1610 * @root: radix tree root
1611 * @tag: tag to test
1612 */
1613 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1614 {
1615 return root_tag_get(root, tag);
1616 }
1617 EXPORT_SYMBOL(radix_tree_tagged);
1618
1619 static void
1620 radix_tree_node_ctor(void *arg)
1621 {
1622 struct radix_tree_node *node = arg;
1623
1624 memset(node, 0, sizeof(*node));
1625 INIT_LIST_HEAD(&node->private_list);
1626 }
1627
1628 static __init unsigned long __maxindex(unsigned int height)
1629 {
1630 unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1631 int shift = RADIX_TREE_INDEX_BITS - width;
1632
1633 if (shift < 0)
1634 return ~0UL;
1635 if (shift >= BITS_PER_LONG)
1636 return 0UL;
1637 return ~0UL >> shift;
1638 }
1639
1640 static __init void radix_tree_init_maxnodes(void)
1641 {
1642 unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1];
1643 unsigned int i, j;
1644
1645 for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1646 height_to_maxindex[i] = __maxindex(i);
1647 for (i = 0; i < ARRAY_SIZE(height_to_maxnodes); i++) {
1648 for (j = i; j > 0; j--)
1649 height_to_maxnodes[i] += height_to_maxindex[j - 1] + 1;
1650 }
1651 }
1652
1653 static int radix_tree_callback(struct notifier_block *nfb,
1654 unsigned long action, void *hcpu)
1655 {
1656 int cpu = (long)hcpu;
1657 struct radix_tree_preload *rtp;
1658 struct radix_tree_node *node;
1659
1660 /* Free per-cpu pool of preloaded nodes */
1661 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1662 rtp = &per_cpu(radix_tree_preloads, cpu);
1663 while (rtp->nr) {
1664 node = rtp->nodes;
1665 rtp->nodes = node->private_data;
1666 kmem_cache_free(radix_tree_node_cachep, node);
1667 rtp->nr--;
1668 }
1669 }
1670 return NOTIFY_OK;
1671 }
1672
1673 void __init radix_tree_init(void)
1674 {
1675 radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1676 sizeof(struct radix_tree_node), 0,
1677 SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1678 radix_tree_node_ctor);
1679 radix_tree_init_maxnodes();
1680 hotcpu_notifier(radix_tree_callback, 0);
1681 }