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 
entry_to_node(void * ptr)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 
node_to_entry(void * ptr)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
get_slot_offset(const struct radix_tree_node * parent,void __rcu ** slot)80 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
81 {
82 	return parent ? slot - parent->slots : 0;
83 }
84 
radix_tree_descend(const struct radix_tree_node * parent,struct radix_tree_node ** nodep,unsigned long index)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 
root_gfp_mask(const struct radix_tree_root * root)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 
tag_set(struct radix_tree_node * node,unsigned int tag,int offset)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 
tag_clear(struct radix_tree_node * node,unsigned int tag,int offset)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 
tag_get(const struct radix_tree_node * node,unsigned int tag,int offset)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 
root_tag_set(struct radix_tree_root * root,unsigned tag)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 
root_tag_clear(struct radix_tree_root * root,unsigned tag)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 
root_tag_clear_all(struct radix_tree_root * root)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 
root_tag_get(const struct radix_tree_root * root,unsigned tag)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 
root_tags_get(const struct radix_tree_root * root)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 
is_idr(const struct radix_tree_root * root)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  */
any_tag_set(const struct radix_tree_node * node,unsigned int tag)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 
all_tag_set(struct radix_tree_node * node,unsigned int tag)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
radix_tree_find_next_bit(struct radix_tree_node * node,unsigned int tag,unsigned long offset)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 
iter_offset(const struct radix_tree_iter * iter)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  */
shift_maxindex(unsigned int shift)211 static inline unsigned long shift_maxindex(unsigned int shift)
212 {
213 	return (RADIX_TREE_MAP_SIZE << shift) - 1;
214 }
215 
node_maxindex(const struct radix_tree_node * node)216 static inline unsigned long node_maxindex(const struct radix_tree_node *node)
217 {
218 	return shift_maxindex(node->shift);
219 }
220 
next_index(unsigned long index,const struct radix_tree_node * node,unsigned long offset)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 *
radix_tree_node_alloc(gfp_t gfp_mask,struct radix_tree_node * parent,struct radix_tree_root * root,unsigned int shift,unsigned int offset,unsigned int count,unsigned int nr_values)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 
radix_tree_node_rcu_free(struct rcu_head * head)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
radix_tree_node_free(struct radix_tree_node * node)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  */
__radix_tree_preload(gfp_t gfp_mask,unsigned nr)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  */
radix_tree_preload(gfp_t gfp_mask)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  */
radix_tree_maybe_preload(gfp_t gfp_mask)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 
radix_tree_load_root(const struct radix_tree_root * root,struct radix_tree_node ** nodep,unsigned long * maxindex)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  */
radix_tree_extend(struct radix_tree_root * root,gfp_t gfp,unsigned long index,unsigned int shift)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  */
radix_tree_shrink(struct radix_tree_root * root)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 
delete_node(struct radix_tree_root * root,struct radix_tree_node * node)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  */
__radix_tree_create(struct radix_tree_root * root,unsigned long index,struct radix_tree_node ** nodep,void __rcu *** slotp)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  */
radix_tree_free_nodes(struct radix_tree_node * node)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 
insert_entries(struct radix_tree_node * node,void __rcu ** slot,void * item)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  */
radix_tree_insert(struct radix_tree_root * root,unsigned long index,void * item)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  */
__radix_tree_lookup(const struct radix_tree_root * root,unsigned long index,struct radix_tree_node ** nodep,void __rcu *** slotp)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  */
radix_tree_lookup_slot(const struct radix_tree_root * root,unsigned long index)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  */
radix_tree_lookup(const struct radix_tree_root * root,unsigned long index)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 
replace_slot(void __rcu ** slot,void * item,struct radix_tree_node * node,int count,int values)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 
node_tag_get(const struct radix_tree_root * root,const struct radix_tree_node * node,unsigned int tag,unsigned int offset)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  */
calculate_count(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot,void * item,void * old)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  */
__radix_tree_replace(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot,void * item)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  */
radix_tree_replace_slot(struct radix_tree_root * root,void __rcu ** slot,void * item)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  */
radix_tree_iter_replace(struct radix_tree_root * root,const struct radix_tree_iter * iter,void __rcu ** slot,void * item)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 
node_tag_set(struct radix_tree_root * root,struct radix_tree_node * node,unsigned int tag,unsigned int offset)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  */
radix_tree_tag_set(struct radix_tree_root * root,unsigned long index,unsigned int tag)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 
node_tag_clear(struct radix_tree_root * root,struct radix_tree_node * node,unsigned int tag,unsigned int offset)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  */
radix_tree_tag_clear(struct radix_tree_root * root,unsigned long index,unsigned int tag)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   */
radix_tree_iter_tag_clear(struct radix_tree_root * root,const struct radix_tree_iter * iter,unsigned int tag)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  */
radix_tree_tag_get(const struct radix_tree_root * root,unsigned long index,unsigned int tag)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 */
set_iter_tags(struct radix_tree_iter * iter,struct radix_tree_node * node,unsigned offset,unsigned tag)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 
radix_tree_iter_resume(void __rcu ** slot,struct radix_tree_iter * iter)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  */
radix_tree_next_chunk(const struct radix_tree_root * root,struct radix_tree_iter * iter,unsigned flags)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
radix_tree_gang_lookup(const struct radix_tree_root * root,void ** results,unsigned long first_index,unsigned int max_items)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
radix_tree_gang_lookup_tag(const struct radix_tree_root * root,void ** results,unsigned long first_index,unsigned int max_items,unsigned int tag)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
radix_tree_gang_lookup_tag_slot(const struct radix_tree_root * root,void __rcu *** results,unsigned long first_index,unsigned int max_items,unsigned int tag)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 
__radix_tree_delete(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot)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  */
radix_tree_iter_delete(struct radix_tree_root * root,struct radix_tree_iter * iter,void __rcu ** slot)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  */
radix_tree_delete_item(struct radix_tree_root * root,unsigned long index,void * item)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  */
radix_tree_delete(struct radix_tree_root * root,unsigned long index)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  */
radix_tree_tagged(const struct radix_tree_root * root,unsigned int tag)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  */
idr_preload(gfp_t gfp_mask)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 
idr_get_free(struct radix_tree_root * root,struct radix_tree_iter * iter,gfp_t gfp,unsigned long max)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  */
idr_destroy(struct idr * idr)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
radix_tree_node_ctor(void * arg)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 
radix_tree_cpu_dead(unsigned int cpu)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 
radix_tree_init(void)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