1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright (C) 2001 Momchil Velikov
   4 * Portions Copyright (C) 2001 Christoph Hellwig
   5 * Copyright (C) 2005 SGI, Christoph Lameter
   6 * Copyright (C) 2006 Nick Piggin
   7 * Copyright (C) 2012 Konstantin Khlebnikov
   8 * Copyright (C) 2016 Intel, Matthew Wilcox
   9 * Copyright (C) 2016 Intel, Ross Zwisler
  10 */
  11
  12#include <linux/bitmap.h>
  13#include <linux/bitops.h>
  14#include <linux/bug.h>
  15#include <linux/cpu.h>
  16#include <linux/errno.h>
  17#include <linux/export.h>
  18#include <linux/idr.h>
  19#include <linux/init.h>
  20#include <linux/kernel.h>
  21#include <linux/kmemleak.h>
  22#include <linux/percpu.h>
  23#include <linux/preempt.h>		/* in_interrupt() */
  24#include <linux/radix-tree.h>
  25#include <linux/rcupdate.h>
  26#include <linux/slab.h>
  27#include <linux/string.h>
  28#include <linux/xarray.h>
  29
  30/*
  31 * Radix tree node cache.
  32 */
  33struct kmem_cache *radix_tree_node_cachep;
  34
  35/*
  36 * The radix tree is variable-height, so an insert operation not only has
  37 * to build the branch to its corresponding item, it also has to build the
  38 * branch to existing items if the size has to be increased (by
  39 * radix_tree_extend).
  40 *
  41 * The worst case is a zero height tree with just a single item at index 0,
  42 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
  43 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
  44 * Hence:
  45 */
  46#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
  47
  48/*
  49 * The IDR does not have to be as high as the radix tree since it uses
  50 * signed integers, not unsigned longs.
  51 */
  52#define IDR_INDEX_BITS		(8 /* CHAR_BIT */ * sizeof(int) - 1)
  53#define IDR_MAX_PATH		(DIV_ROUND_UP(IDR_INDEX_BITS, \
  54						RADIX_TREE_MAP_SHIFT))
  55#define IDR_PRELOAD_SIZE	(IDR_MAX_PATH * 2 - 1)
  56
  57/*
  58 * Per-cpu pool of preloaded nodes
  59 */
  60DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = {
  61	.lock = INIT_LOCAL_LOCK(lock),
  62};
  63EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads);
  64
  65static inline struct radix_tree_node *entry_to_node(void *ptr)
  66{
  67	return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
  68}
  69
  70static inline void *node_to_entry(void *ptr)
  71{
  72	return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
  73}
  74
  75#define RADIX_TREE_RETRY	XA_RETRY_ENTRY
  76
  77static inline unsigned long
  78get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
  79{
  80	return parent ? slot - parent->slots : 0;
  81}
  82
  83static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
  84			struct radix_tree_node **nodep, unsigned long index)
  85{
  86	unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
  87	void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
  88
  89	*nodep = (void *)entry;
  90	return offset;
  91}
  92
  93static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
  94{
  95	return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
  96}
  97
  98static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
  99		int offset)
 100{
 101	__set_bit(offset, node->tags[tag]);
 102}
 103
 104static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 105		int offset)
 106{
 107	__clear_bit(offset, node->tags[tag]);
 108}
 109
 110static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
 111		int offset)
 112{
 113	return test_bit(offset, node->tags[tag]);
 114}
 115
 116static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
 117{
 118	root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
 119}
 120
 121static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
 122{
 123	root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
 124}
 125
 126static inline void root_tag_clear_all(struct radix_tree_root *root)
 127{
 128	root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
 129}
 130
 131static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
 132{
 133	return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
 134}
 135
 136static inline unsigned root_tags_get(const struct radix_tree_root *root)
 137{
 138	return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
 139}
 140
 141static inline bool is_idr(const struct radix_tree_root *root)
 142{
 143	return !!(root->xa_flags & ROOT_IS_IDR);
 144}
 145
 146/*
 147 * Returns 1 if any slot in the node has this tag set.
 148 * Otherwise returns 0.
 149 */
 150static inline int any_tag_set(const struct radix_tree_node *node,
 151							unsigned int tag)
 152{
 153	unsigned idx;
 154	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 155		if (node->tags[tag][idx])
 156			return 1;
 157	}
 158	return 0;
 159}
 160
 161static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
 162{
 163	bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
 164}
 165
 166/**
 167 * radix_tree_find_next_bit - find the next set bit in a memory region
 168 *
 169 * @node: where to begin the search
 170 * @tag: the tag index
 171 * @offset: the bitnumber to start searching at
 172 *
 173 * Unrollable variant of find_next_bit() for constant size arrays.
 174 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
 175 * Returns next bit offset, or size if nothing found.
 176 */
 177static __always_inline unsigned long
 178radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
 179			 unsigned long offset)
 180{
 181	const unsigned long *addr = node->tags[tag];
 182
 183	if (offset < RADIX_TREE_MAP_SIZE) {
 184		unsigned long tmp;
 185
 186		addr += offset / BITS_PER_LONG;
 187		tmp = *addr >> (offset % BITS_PER_LONG);
 188		if (tmp)
 189			return __ffs(tmp) + offset;
 190		offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
 191		while (offset < RADIX_TREE_MAP_SIZE) {
 192			tmp = *++addr;
 193			if (tmp)
 194				return __ffs(tmp) + offset;
 195			offset += BITS_PER_LONG;
 196		}
 197	}
 198	return RADIX_TREE_MAP_SIZE;
 199}
 200
 201static unsigned int iter_offset(const struct radix_tree_iter *iter)
 202{
 203	return iter->index & RADIX_TREE_MAP_MASK;
 204}
 205
 206/*
 207 * The maximum index which can be stored in a radix tree
 208 */
 209static inline unsigned long shift_maxindex(unsigned int shift)
 210{
 211	return (RADIX_TREE_MAP_SIZE << shift) - 1;
 212}
 213
 214static inline unsigned long node_maxindex(const struct radix_tree_node *node)
 215{
 216	return shift_maxindex(node->shift);
 217}
 218
 219static unsigned long next_index(unsigned long index,
 220				const struct radix_tree_node *node,
 221				unsigned long offset)
 222{
 223	return (index & ~node_maxindex(node)) + (offset << node->shift);
 224}
 225
 226/*
 227 * This assumes that the caller has performed appropriate preallocation, and
 228 * that the caller has pinned this thread of control to the current CPU.
 229 */
 230static struct radix_tree_node *
 231radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
 232			struct radix_tree_root *root,
 233			unsigned int shift, unsigned int offset,
 234			unsigned int count, unsigned int nr_values)
 235{
 236	struct radix_tree_node *ret = NULL;
 237
 238	/*
 239	 * Preload code isn't irq safe and it doesn't make sense to use
 240	 * preloading during an interrupt anyway as all the allocations have
 241	 * to be atomic. So just do normal allocation when in interrupt.
 242	 */
 243	if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
 244		struct radix_tree_preload *rtp;
 245
 246		/*
 247		 * Even if the caller has preloaded, try to allocate from the
 248		 * cache first for the new node to get accounted to the memory
 249		 * cgroup.
 250		 */
 251		ret = kmem_cache_alloc(radix_tree_node_cachep,
 252				       gfp_mask | __GFP_NOWARN);
 253		if (ret)
 254			goto out;
 255
 256		/*
 257		 * Provided the caller has preloaded here, we will always
 258		 * succeed in getting a node here (and never reach
 259		 * kmem_cache_alloc)
 260		 */
 261		rtp = this_cpu_ptr(&radix_tree_preloads);
 262		if (rtp->nr) {
 263			ret = rtp->nodes;
 264			rtp->nodes = ret->parent;
 265			rtp->nr--;
 266		}
 267		/*
 268		 * Update the allocation stack trace as this is more useful
 269		 * for debugging.
 270		 */
 271		kmemleak_update_trace(ret);
 272		goto out;
 273	}
 274	ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 275out:
 276	BUG_ON(radix_tree_is_internal_node(ret));
 277	if (ret) {
 278		ret->shift = shift;
 279		ret->offset = offset;
 280		ret->count = count;
 281		ret->nr_values = nr_values;
 282		ret->parent = parent;
 283		ret->array = root;
 284	}
 285	return ret;
 286}
 287
 288void radix_tree_node_rcu_free(struct rcu_head *head)
 289{
 290	struct radix_tree_node *node =
 291			container_of(head, struct radix_tree_node, rcu_head);
 292
 293	/*
 294	 * Must only free zeroed nodes into the slab.  We can be left with
 295	 * non-NULL entries by radix_tree_free_nodes, so clear the entries
 296	 * and tags here.
 297	 */
 298	memset(node->slots, 0, sizeof(node->slots));
 299	memset(node->tags, 0, sizeof(node->tags));
 300	INIT_LIST_HEAD(&node->private_list);
 301
 302	kmem_cache_free(radix_tree_node_cachep, node);
 303}
 304
 305static inline void
 306radix_tree_node_free(struct radix_tree_node *node)
 307{
 308	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 309}
 310
 311/*
 312 * Load up this CPU's radix_tree_node buffer with sufficient objects to
 313 * ensure that the addition of a single element in the tree cannot fail.  On
 314 * success, return zero, with preemption disabled.  On error, return -ENOMEM
 315 * with preemption not disabled.
 316 *
 317 * To make use of this facility, the radix tree must be initialised without
 318 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 319 */
 320static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
 321{
 322	struct radix_tree_preload *rtp;
 323	struct radix_tree_node *node;
 324	int ret = -ENOMEM;
 325
 326	/*
 327	 * Nodes preloaded by one cgroup can be used by another cgroup, so
 328	 * they should never be accounted to any particular memory cgroup.
 329	 */
 330	gfp_mask &= ~__GFP_ACCOUNT;
 331
 332	local_lock(&radix_tree_preloads.lock);
 333	rtp = this_cpu_ptr(&radix_tree_preloads);
 334	while (rtp->nr < nr) {
 335		local_unlock(&radix_tree_preloads.lock);
 336		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 337		if (node == NULL)
 338			goto out;
 339		local_lock(&radix_tree_preloads.lock);
 340		rtp = this_cpu_ptr(&radix_tree_preloads);
 341		if (rtp->nr < nr) {
 342			node->parent = rtp->nodes;
 343			rtp->nodes = node;
 344			rtp->nr++;
 345		} else {
 346			kmem_cache_free(radix_tree_node_cachep, node);
 347		}
 348	}
 349	ret = 0;
 350out:
 351	return ret;
 352}
 353
 354/*
 355 * Load up this CPU's radix_tree_node buffer with sufficient objects to
 356 * ensure that the addition of a single element in the tree cannot fail.  On
 357 * success, return zero, with preemption disabled.  On error, return -ENOMEM
 358 * with preemption not disabled.
 359 *
 360 * To make use of this facility, the radix tree must be initialised without
 361 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 362 */
 363int radix_tree_preload(gfp_t gfp_mask)
 364{
 365	/* Warn on non-sensical use... */
 366	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
 367	return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
 368}
 369EXPORT_SYMBOL(radix_tree_preload);
 370
 371/*
 372 * The same as above function, except we don't guarantee preloading happens.
 373 * We do it, if we decide it helps. On success, return zero with preemption
 374 * disabled. On error, return -ENOMEM with preemption not disabled.
 375 */
 376int radix_tree_maybe_preload(gfp_t gfp_mask)
 377{
 378	if (gfpflags_allow_blocking(gfp_mask))
 379		return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
 380	/* Preloading doesn't help anything with this gfp mask, skip it */
 381	local_lock(&radix_tree_preloads.lock);
 382	return 0;
 383}
 384EXPORT_SYMBOL(radix_tree_maybe_preload);
 385
 386static unsigned radix_tree_load_root(const struct radix_tree_root *root,
 387		struct radix_tree_node **nodep, unsigned long *maxindex)
 388{
 389	struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
 390
 391	*nodep = node;
 392
 393	if (likely(radix_tree_is_internal_node(node))) {
 394		node = entry_to_node(node);
 395		*maxindex = node_maxindex(node);
 396		return node->shift + RADIX_TREE_MAP_SHIFT;
 397	}
 398
 399	*maxindex = 0;
 400	return 0;
 401}
 402
 403/*
 404 *	Extend a radix tree so it can store key @index.
 405 */
 406static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
 407				unsigned long index, unsigned int shift)
 408{
 409	void *entry;
 410	unsigned int maxshift;
 411	int tag;
 412
 413	/* Figure out what the shift should be.  */
 414	maxshift = shift;
 415	while (index > shift_maxindex(maxshift))
 416		maxshift += RADIX_TREE_MAP_SHIFT;
 417
 418	entry = rcu_dereference_raw(root->xa_head);
 419	if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
 420		goto out;
 421
 422	do {
 423		struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
 424							root, shift, 0, 1, 0);
 425		if (!node)
 426			return -ENOMEM;
 427
 428		if (is_idr(root)) {
 429			all_tag_set(node, IDR_FREE);
 430			if (!root_tag_get(root, IDR_FREE)) {
 431				tag_clear(node, IDR_FREE, 0);
 432				root_tag_set(root, IDR_FREE);
 433			}
 434		} else {
 435			/* Propagate the aggregated tag info to the new child */
 436			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 437				if (root_tag_get(root, tag))
 438					tag_set(node, tag, 0);
 439			}
 440		}
 441
 442		BUG_ON(shift > BITS_PER_LONG);
 443		if (radix_tree_is_internal_node(entry)) {
 444			entry_to_node(entry)->parent = node;
 445		} else if (xa_is_value(entry)) {
 446			/* Moving a value entry root->xa_head to a node */
 447			node->nr_values = 1;
 448		}
 449		/*
 450		 * entry was already in the radix tree, so we do not need
 451		 * rcu_assign_pointer here
 452		 */
 453		node->slots[0] = (void __rcu *)entry;
 454		entry = node_to_entry(node);
 455		rcu_assign_pointer(root->xa_head, entry);
 456		shift += RADIX_TREE_MAP_SHIFT;
 457	} while (shift <= maxshift);
 458out:
 459	return maxshift + RADIX_TREE_MAP_SHIFT;
 460}
 461
 462/**
 463 *	radix_tree_shrink    -    shrink radix tree to minimum height
 464 *	@root:		radix tree root
 465 */
 466static inline bool radix_tree_shrink(struct radix_tree_root *root)
 467{
 468	bool shrunk = false;
 469
 470	for (;;) {
 471		struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
 472		struct radix_tree_node *child;
 473
 474		if (!radix_tree_is_internal_node(node))
 475			break;
 476		node = entry_to_node(node);
 477
 478		/*
 479		 * The candidate node has more than one child, or its child
 480		 * is not at the leftmost slot, we cannot shrink.
 481		 */
 482		if (node->count != 1)
 483			break;
 484		child = rcu_dereference_raw(node->slots[0]);
 485		if (!child)
 486			break;
 487
 488		/*
 489		 * For an IDR, we must not shrink entry 0 into the root in
 490		 * case somebody calls idr_replace() with a pointer that
 491		 * appears to be an internal entry
 492		 */
 493		if (!node->shift && is_idr(root))
 494			break;
 495
 496		if (radix_tree_is_internal_node(child))
 497			entry_to_node(child)->parent = NULL;
 498
 499		/*
 500		 * We don't need rcu_assign_pointer(), since we are simply
 501		 * moving the node from one part of the tree to another: if it
 502		 * was safe to dereference the old pointer to it
 503		 * (node->slots[0]), it will be safe to dereference the new
 504		 * one (root->xa_head) as far as dependent read barriers go.
 505		 */
 506		root->xa_head = (void __rcu *)child;
 507		if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
 508			root_tag_clear(root, IDR_FREE);
 509
 510		/*
 511		 * We have a dilemma here. The node's slot[0] must not be
 512		 * NULLed in case there are concurrent lookups expecting to
 513		 * find the item. However if this was a bottom-level node,
 514		 * then it may be subject to the slot pointer being visible
 515		 * to callers dereferencing it. If item corresponding to
 516		 * slot[0] is subsequently deleted, these callers would expect
 517		 * their slot to become empty sooner or later.
 518		 *
 519		 * For example, lockless pagecache will look up a slot, deref
 520		 * the page pointer, and if the page has 0 refcount it means it
 521		 * was concurrently deleted from pagecache so try the deref
 522		 * again. Fortunately there is already a requirement for logic
 523		 * to retry the entire slot lookup -- the indirect pointer
 524		 * problem (replacing direct root node with an indirect pointer
 525		 * also results in a stale slot). So tag the slot as indirect
 526		 * to force callers to retry.
 527		 */
 528		node->count = 0;
 529		if (!radix_tree_is_internal_node(child)) {
 530			node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
 531		}
 532
 533		WARN_ON_ONCE(!list_empty(&node->private_list));
 534		radix_tree_node_free(node);
 535		shrunk = true;
 536	}
 537
 538	return shrunk;
 539}
 540
 541static bool delete_node(struct radix_tree_root *root,
 542			struct radix_tree_node *node)
 543{
 544	bool deleted = false;
 545
 546	do {
 547		struct radix_tree_node *parent;
 548
 549		if (node->count) {
 550			if (node_to_entry(node) ==
 551					rcu_dereference_raw(root->xa_head))
 552				deleted |= radix_tree_shrink(root);
 553			return deleted;
 554		}
 555
 556		parent = node->parent;
 557		if (parent) {
 558			parent->slots[node->offset] = NULL;
 559			parent->count--;
 560		} else {
 561			/*
 562			 * Shouldn't the tags already have all been cleared
 563			 * by the caller?
 564			 */
 565			if (!is_idr(root))
 566				root_tag_clear_all(root);
 567			root->xa_head = NULL;
 568		}
 569
 570		WARN_ON_ONCE(!list_empty(&node->private_list));
 571		radix_tree_node_free(node);
 572		deleted = true;
 573
 574		node = parent;
 575	} while (node);
 576
 577	return deleted;
 578}
 579
 580/**
 581 *	__radix_tree_create	-	create a slot in a radix tree
 582 *	@root:		radix tree root
 583 *	@index:		index key
 584 *	@nodep:		returns node
 585 *	@slotp:		returns slot
 586 *
 587 *	Create, if necessary, and return the node and slot for an item
 588 *	at position @index in the radix tree @root.
 589 *
 590 *	Until there is more than one item in the tree, no nodes are
 591 *	allocated and @root->xa_head is used as a direct slot instead of
 592 *	pointing to a node, in which case *@nodep will be NULL.
 593 *
 594 *	Returns -ENOMEM, or 0 for success.
 595 */
 596static int __radix_tree_create(struct radix_tree_root *root,
 597		unsigned long index, struct radix_tree_node **nodep,
 598		void __rcu ***slotp)
 599{
 600	struct radix_tree_node *node = NULL, *child;
 601	void __rcu **slot = (void __rcu **)&root->xa_head;
 602	unsigned long maxindex;
 603	unsigned int shift, offset = 0;
 604	unsigned long max = index;
 605	gfp_t gfp = root_gfp_mask(root);
 606
 607	shift = radix_tree_load_root(root, &child, &maxindex);
 608
 609	/* Make sure the tree is high enough.  */
 610	if (max > maxindex) {
 611		int error = radix_tree_extend(root, gfp, max, shift);
 612		if (error < 0)
 613			return error;
 614		shift = error;
 615		child = rcu_dereference_raw(root->xa_head);
 616	}
 617
 618	while (shift > 0) {
 619		shift -= RADIX_TREE_MAP_SHIFT;
 620		if (child == NULL) {
 621			/* Have to add a child node.  */
 622			child = radix_tree_node_alloc(gfp, node, root, shift,
 623							offset, 0, 0);
 624			if (!child)
 625				return -ENOMEM;
 626			rcu_assign_pointer(*slot, node_to_entry(child));
 627			if (node)
 628				node->count++;
 629		} else if (!radix_tree_is_internal_node(child))
 630			break;
 631
 632		/* Go a level down */
 633		node = entry_to_node(child);
 634		offset = radix_tree_descend(node, &child, index);
 635		slot = &node->slots[offset];
 636	}
 637
 638	if (nodep)
 639		*nodep = node;
 640	if (slotp)
 641		*slotp = slot;
 642	return 0;
 643}
 644
 645/*
 646 * Free any nodes below this node.  The tree is presumed to not need
 647 * shrinking, and any user data in the tree is presumed to not need a
 648 * destructor called on it.  If we need to add a destructor, we can
 649 * add that functionality later.  Note that we may not clear tags or
 650 * slots from the tree as an RCU walker may still have a pointer into
 651 * this subtree.  We could replace the entries with RADIX_TREE_RETRY,
 652 * but we'll still have to clear those in rcu_free.
 653 */
 654static void radix_tree_free_nodes(struct radix_tree_node *node)
 655{
 656	unsigned offset = 0;
 657	struct radix_tree_node *child = entry_to_node(node);
 658
 659	for (;;) {
 660		void *entry = rcu_dereference_raw(child->slots[offset]);
 661		if (xa_is_node(entry) && child->shift) {
 662			child = entry_to_node(entry);
 663			offset = 0;
 664			continue;
 665		}
 666		offset++;
 667		while (offset == RADIX_TREE_MAP_SIZE) {
 668			struct radix_tree_node *old = child;
 669			offset = child->offset + 1;
 670			child = child->parent;
 671			WARN_ON_ONCE(!list_empty(&old->private_list));
 672			radix_tree_node_free(old);
 673			if (old == entry_to_node(node))
 674				return;
 675		}
 676	}
 677}
 678
 679static inline int insert_entries(struct radix_tree_node *node,
 680		void __rcu **slot, void *item, bool replace)
 681{
 682	if (*slot)
 683		return -EEXIST;
 684	rcu_assign_pointer(*slot, item);
 685	if (node) {
 686		node->count++;
 687		if (xa_is_value(item))
 688			node->nr_values++;
 689	}
 690	return 1;
 691}
 692
 693/**
 694 *	radix_tree_insert    -    insert into a radix tree
 695 *	@root:		radix tree root
 696 *	@index:		index key
 697 *	@item:		item to insert
 698 *
 699 *	Insert an item into the radix tree at position @index.
 700 */
 701int radix_tree_insert(struct radix_tree_root *root, unsigned long index,
 702			void *item)
 703{
 704	struct radix_tree_node *node;
 705	void __rcu **slot;
 706	int error;
 707
 708	BUG_ON(radix_tree_is_internal_node(item));
 709
 710	error = __radix_tree_create(root, index, &node, &slot);
 711	if (error)
 712		return error;
 713
 714	error = insert_entries(node, slot, item, false);
 715	if (error < 0)
 716		return error;
 717
 718	if (node) {
 719		unsigned offset = get_slot_offset(node, slot);
 720		BUG_ON(tag_get(node, 0, offset));
 721		BUG_ON(tag_get(node, 1, offset));
 722		BUG_ON(tag_get(node, 2, offset));
 723	} else {
 724		BUG_ON(root_tags_get(root));
 725	}
 726
 727	return 0;
 728}
 729EXPORT_SYMBOL(radix_tree_insert);
 730
 731/**
 732 *	__radix_tree_lookup	-	lookup an item in a radix tree
 733 *	@root:		radix tree root
 734 *	@index:		index key
 735 *	@nodep:		returns node
 736 *	@slotp:		returns slot
 737 *
 738 *	Lookup and return the item at position @index in the radix
 739 *	tree @root.
 740 *
 741 *	Until there is more than one item in the tree, no nodes are
 742 *	allocated and @root->xa_head is used as a direct slot instead of
 743 *	pointing to a node, in which case *@nodep will be NULL.
 744 */
 745void *__radix_tree_lookup(const struct radix_tree_root *root,
 746			  unsigned long index, struct radix_tree_node **nodep,
 747			  void __rcu ***slotp)
 748{
 749	struct radix_tree_node *node, *parent;
 750	unsigned long maxindex;
 751	void __rcu **slot;
 752
 753 restart:
 754	parent = NULL;
 755	slot = (void __rcu **)&root->xa_head;
 756	radix_tree_load_root(root, &node, &maxindex);
 757	if (index > maxindex)
 758		return NULL;
 759
 760	while (radix_tree_is_internal_node(node)) {
 761		unsigned offset;
 762
 763		parent = entry_to_node(node);
 764		offset = radix_tree_descend(parent, &node, index);
 765		slot = parent->slots + offset;
 766		if (node == RADIX_TREE_RETRY)
 767			goto restart;
 768		if (parent->shift == 0)
 769			break;
 770	}
 771
 772	if (nodep)
 773		*nodep = parent;
 774	if (slotp)
 775		*slotp = slot;
 776	return node;
 777}
 778
 779/**
 780 *	radix_tree_lookup_slot    -    lookup a slot in a radix tree
 781 *	@root:		radix tree root
 782 *	@index:		index key
 783 *
 784 *	Returns:  the slot corresponding to the position @index in the
 785 *	radix tree @root. This is useful for update-if-exists operations.
 786 *
 787 *	This function can be called under rcu_read_lock iff the slot is not
 788 *	modified by radix_tree_replace_slot, otherwise it must be called
 789 *	exclusive from other writers. Any dereference of the slot must be done
 790 *	using radix_tree_deref_slot.
 791 */
 792void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
 793				unsigned long index)
 794{
 795	void __rcu **slot;
 796
 797	if (!__radix_tree_lookup(root, index, NULL, &slot))
 798		return NULL;
 799	return slot;
 800}
 801EXPORT_SYMBOL(radix_tree_lookup_slot);
 802
 803/**
 804 *	radix_tree_lookup    -    perform lookup operation on a radix tree
 805 *	@root:		radix tree root
 806 *	@index:		index key
 807 *
 808 *	Lookup the item at the position @index in the radix tree @root.
 809 *
 810 *	This function can be called under rcu_read_lock, however the caller
 811 *	must manage lifetimes of leaf nodes (eg. RCU may also be used to free
 812 *	them safely). No RCU barriers are required to access or modify the
 813 *	returned item, however.
 814 */
 815void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
 816{
 817	return __radix_tree_lookup(root, index, NULL, NULL);
 818}
 819EXPORT_SYMBOL(radix_tree_lookup);
 820
 821static void replace_slot(void __rcu **slot, void *item,
 822		struct radix_tree_node *node, int count, int values)
 823{
 824	if (node && (count || values)) {
 825		node->count += count;
 826		node->nr_values += values;
 827	}
 828
 829	rcu_assign_pointer(*slot, item);
 830}
 831
 832static bool node_tag_get(const struct radix_tree_root *root,
 833				const struct radix_tree_node *node,
 834				unsigned int tag, unsigned int offset)
 835{
 836	if (node)
 837		return tag_get(node, tag, offset);
 838	return root_tag_get(root, tag);
 839}
 840
 841/*
 842 * IDR users want to be able to store NULL in the tree, so if the slot isn't
 843 * free, don't adjust the count, even if it's transitioning between NULL and
 844 * non-NULL.  For the IDA, we mark slots as being IDR_FREE while they still
 845 * have empty bits, but it only stores NULL in slots when they're being
 846 * deleted.
 847 */
 848static int calculate_count(struct radix_tree_root *root,
 849				struct radix_tree_node *node, void __rcu **slot,
 850				void *item, void *old)
 851{
 852	if (is_idr(root)) {
 853		unsigned offset = get_slot_offset(node, slot);
 854		bool free = node_tag_get(root, node, IDR_FREE, offset);
 855		if (!free)
 856			return 0;
 857		if (!old)
 858			return 1;
 859	}
 860	return !!item - !!old;
 861}
 862
 863/**
 864 * __radix_tree_replace		- replace item in a slot
 865 * @root:		radix tree root
 866 * @node:		pointer to tree node
 867 * @slot:		pointer to slot in @node
 868 * @item:		new item to store in the slot.
 869 *
 870 * For use with __radix_tree_lookup().  Caller must hold tree write locked
 871 * across slot lookup and replacement.
 872 */
 873void __radix_tree_replace(struct radix_tree_root *root,
 874			  struct radix_tree_node *node,
 875			  void __rcu **slot, void *item)
 876{
 877	void *old = rcu_dereference_raw(*slot);
 878	int values = !!xa_is_value(item) - !!xa_is_value(old);
 879	int count = calculate_count(root, node, slot, item, old);
 880
 881	/*
 882	 * This function supports replacing value entries and
 883	 * deleting entries, but that needs accounting against the
 884	 * node unless the slot is root->xa_head.
 885	 */
 886	WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
 887			(count || values));
 888	replace_slot(slot, item, node, count, values);
 889
 890	if (!node)
 891		return;
 892
 893	delete_node(root, node);
 894}
 895
 896/**
 897 * radix_tree_replace_slot	- replace item in a slot
 898 * @root:	radix tree root
 899 * @slot:	pointer to slot
 900 * @item:	new item to store in the slot.
 901 *
 902 * For use with radix_tree_lookup_slot() and
 903 * radix_tree_gang_lookup_tag_slot().  Caller must hold tree write locked
 904 * across slot lookup and replacement.
 905 *
 906 * NOTE: This cannot be used to switch between non-entries (empty slots),
 907 * regular entries, and value entries, as that requires accounting
 908 * inside the radix tree node. When switching from one type of entry or
 909 * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
 910 * radix_tree_iter_replace().
 911 */
 912void radix_tree_replace_slot(struct radix_tree_root *root,
 913			     void __rcu **slot, void *item)
 914{
 915	__radix_tree_replace(root, NULL, slot, item);
 916}
 917EXPORT_SYMBOL(radix_tree_replace_slot);
 918
 919/**
 920 * radix_tree_iter_replace - replace item in a slot
 921 * @root:	radix tree root
 922 * @iter:	iterator state
 923 * @slot:	pointer to slot
 924 * @item:	new item to store in the slot.
 925 *
 926 * For use with radix_tree_for_each_slot().
 927 * Caller must hold tree write locked.
 928 */
 929void radix_tree_iter_replace(struct radix_tree_root *root,
 930				const struct radix_tree_iter *iter,
 931				void __rcu **slot, void *item)
 932{
 933	__radix_tree_replace(root, iter->node, slot, item);
 934}
 935
 936static void node_tag_set(struct radix_tree_root *root,
 937				struct radix_tree_node *node,
 938				unsigned int tag, unsigned int offset)
 939{
 940	while (node) {
 941		if (tag_get(node, tag, offset))
 942			return;
 943		tag_set(node, tag, offset);
 944		offset = node->offset;
 945		node = node->parent;
 946	}
 947
 948	if (!root_tag_get(root, tag))
 949		root_tag_set(root, tag);
 950}
 951
 952/**
 953 *	radix_tree_tag_set - set a tag on a radix tree node
 954 *	@root:		radix tree root
 955 *	@index:		index key
 956 *	@tag:		tag index
 957 *
 958 *	Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 959 *	corresponding to @index in the radix tree.  From
 960 *	the root all the way down to the leaf node.
 961 *
 962 *	Returns the address of the tagged item.  Setting a tag on a not-present
 963 *	item is a bug.
 964 */
 965void *radix_tree_tag_set(struct radix_tree_root *root,
 966			unsigned long index, unsigned int tag)
 967{
 968	struct radix_tree_node *node, *parent;
 969	unsigned long maxindex;
 970
 971	radix_tree_load_root(root, &node, &maxindex);
 972	BUG_ON(index > maxindex);
 973
 974	while (radix_tree_is_internal_node(node)) {
 975		unsigned offset;
 976
 977		parent = entry_to_node(node);
 978		offset = radix_tree_descend(parent, &node, index);
 979		BUG_ON(!node);
 980
 981		if (!tag_get(parent, tag, offset))
 982			tag_set(parent, tag, offset);
 983	}
 984
 985	/* set the root's tag bit */
 986	if (!root_tag_get(root, tag))
 987		root_tag_set(root, tag);
 988
 989	return node;
 990}
 991EXPORT_SYMBOL(radix_tree_tag_set);
 992
 993static void node_tag_clear(struct radix_tree_root *root,
 994				struct radix_tree_node *node,
 995				unsigned int tag, unsigned int offset)
 996{
 997	while (node) {
 998		if (!tag_get(node, tag, offset))
 999			return;
1000		tag_clear(node, tag, offset);
1001		if (any_tag_set(node, tag))
1002			return;
1003
1004		offset = node->offset;
1005		node = node->parent;
1006	}
1007
1008	/* clear the root's tag bit */
1009	if (root_tag_get(root, tag))
1010		root_tag_clear(root, tag);
1011}
1012
1013/**
1014 *	radix_tree_tag_clear - clear a tag on a radix tree node
1015 *	@root:		radix tree root
1016 *	@index:		index key
1017 *	@tag:		tag index
1018 *
1019 *	Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1020 *	corresponding to @index in the radix tree.  If this causes
1021 *	the leaf node to have no tags set then clear the tag in the
1022 *	next-to-leaf node, etc.
1023 *
1024 *	Returns the address of the tagged item on success, else NULL.  ie:
1025 *	has the same return value and semantics as radix_tree_lookup().
1026 */
1027void *radix_tree_tag_clear(struct radix_tree_root *root,
1028			unsigned long index, unsigned int tag)
1029{
1030	struct radix_tree_node *node, *parent;
1031	unsigned long maxindex;
1032	int offset;
1033
1034	radix_tree_load_root(root, &node, &maxindex);
1035	if (index > maxindex)
1036		return NULL;
1037
1038	parent = NULL;
1039
1040	while (radix_tree_is_internal_node(node)) {
1041		parent = entry_to_node(node);
1042		offset = radix_tree_descend(parent, &node, index);
1043	}
1044
1045	if (node)
1046		node_tag_clear(root, parent, tag, offset);
1047
1048	return node;
1049}
1050EXPORT_SYMBOL(radix_tree_tag_clear);
1051
1052/**
1053  * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1054  * @root: radix tree root
1055  * @iter: iterator state
1056  * @tag: tag to clear
1057  */
1058void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1059			const struct radix_tree_iter *iter, unsigned int tag)
1060{
1061	node_tag_clear(root, iter->node, tag, iter_offset(iter));
1062}
1063
1064/**
1065 * radix_tree_tag_get - get a tag on a radix tree node
1066 * @root:		radix tree root
1067 * @index:		index key
1068 * @tag:		tag index (< RADIX_TREE_MAX_TAGS)
1069 *
1070 * Return values:
1071 *
1072 *  0: tag not present or not set
1073 *  1: tag set
1074 *
1075 * Note that the return value of this function may not be relied on, even if
1076 * the RCU lock is held, unless tag modification and node deletion are excluded
1077 * from concurrency.
1078 */
1079int radix_tree_tag_get(const struct radix_tree_root *root,
1080			unsigned long index, unsigned int tag)
1081{
1082	struct radix_tree_node *node, *parent;
1083	unsigned long maxindex;
1084
1085	if (!root_tag_get(root, tag))
1086		return 0;
1087
1088	radix_tree_load_root(root, &node, &maxindex);
1089	if (index > maxindex)
1090		return 0;
1091
1092	while (radix_tree_is_internal_node(node)) {
1093		unsigned offset;
1094
1095		parent = entry_to_node(node);
1096		offset = radix_tree_descend(parent, &node, index);
1097
1098		if (!tag_get(parent, tag, offset))
1099			return 0;
1100		if (node == RADIX_TREE_RETRY)
1101			break;
1102	}
1103
1104	return 1;
1105}
1106EXPORT_SYMBOL(radix_tree_tag_get);
1107
1108/* Construct iter->tags bit-mask from node->tags[tag] array */
1109static void set_iter_tags(struct radix_tree_iter *iter,
1110				struct radix_tree_node *node, unsigned offset,
1111				unsigned tag)
1112{
1113	unsigned tag_long = offset / BITS_PER_LONG;
1114	unsigned tag_bit  = offset % BITS_PER_LONG;
1115
1116	if (!node) {
1117		iter->tags = 1;
1118		return;
1119	}
1120
1121	iter->tags = node->tags[tag][tag_long] >> tag_bit;
1122
1123	/* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1124	if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1125		/* Pick tags from next element */
1126		if (tag_bit)
1127			iter->tags |= node->tags[tag][tag_long + 1] <<
1128						(BITS_PER_LONG - tag_bit);
1129		/* Clip chunk size, here only BITS_PER_LONG tags */
1130		iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1131	}
1132}
1133
1134void __rcu **radix_tree_iter_resume(void __rcu **slot,
1135					struct radix_tree_iter *iter)
1136{
1137	slot++;
1138	iter->index = __radix_tree_iter_add(iter, 1);
1139	iter->next_index = iter->index;
1140	iter->tags = 0;
1141	return NULL;
1142}
1143EXPORT_SYMBOL(radix_tree_iter_resume);
1144
1145/**
1146 * radix_tree_next_chunk - find next chunk of slots for iteration
1147 *
1148 * @root:	radix tree root
1149 * @iter:	iterator state
1150 * @flags:	RADIX_TREE_ITER_* flags and tag index
1151 * Returns:	pointer to chunk first slot, or NULL if iteration is over
1152 */
1153void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1154			     struct radix_tree_iter *iter, unsigned flags)
1155{
1156	unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1157	struct radix_tree_node *node, *child;
1158	unsigned long index, offset, maxindex;
1159
1160	if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1161		return NULL;
1162
1163	/*
1164	 * Catch next_index overflow after ~0UL. iter->index never overflows
1165	 * during iterating; it can be zero only at the beginning.
1166	 * And we cannot overflow iter->next_index in a single step,
1167	 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1168	 *
1169	 * This condition also used by radix_tree_next_slot() to stop
1170	 * contiguous iterating, and forbid switching to the next chunk.
1171	 */
1172	index = iter->next_index;
1173	if (!index && iter->index)
1174		return NULL;
1175
1176 restart:
1177	radix_tree_load_root(root, &child, &maxindex);
1178	if (index > maxindex)
1179		return NULL;
1180	if (!child)
1181		return NULL;
1182
1183	if (!radix_tree_is_internal_node(child)) {
1184		/* Single-slot tree */
1185		iter->index = index;
1186		iter->next_index = maxindex + 1;
1187		iter->tags = 1;
1188		iter->node = NULL;
1189		return (void __rcu **)&root->xa_head;
1190	}
1191
1192	do {
1193		node = entry_to_node(child);
1194		offset = radix_tree_descend(node, &child, index);
1195
1196		if ((flags & RADIX_TREE_ITER_TAGGED) ?
1197				!tag_get(node, tag, offset) : !child) {
1198			/* Hole detected */
1199			if (flags & RADIX_TREE_ITER_CONTIG)
1200				return NULL;
1201
1202			if (flags & RADIX_TREE_ITER_TAGGED)
1203				offset = radix_tree_find_next_bit(node, tag,
1204						offset + 1);
1205			else
1206				while (++offset	< RADIX_TREE_MAP_SIZE) {
1207					void *slot = rcu_dereference_raw(
1208							node->slots[offset]);
1209					if (slot)
1210						break;
1211				}
1212			index &= ~node_maxindex(node);
1213			index += offset << node->shift;
1214			/* Overflow after ~0UL */
1215			if (!index)
1216				return NULL;
1217			if (offset == RADIX_TREE_MAP_SIZE)
1218				goto restart;
1219			child = rcu_dereference_raw(node->slots[offset]);
1220		}
1221
1222		if (!child)
1223			goto restart;
1224		if (child == RADIX_TREE_RETRY)
1225			break;
1226	} while (node->shift && radix_tree_is_internal_node(child));
1227
1228	/* Update the iterator state */
1229	iter->index = (index &~ node_maxindex(node)) | offset;
1230	iter->next_index = (index | node_maxindex(node)) + 1;
1231	iter->node = node;
1232
1233	if (flags & RADIX_TREE_ITER_TAGGED)
1234		set_iter_tags(iter, node, offset, tag);
1235
1236	return node->slots + offset;
1237}
1238EXPORT_SYMBOL(radix_tree_next_chunk);
1239
1240/**
1241 *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
1242 *	@root:		radix tree root
1243 *	@results:	where the results of the lookup are placed
1244 *	@first_index:	start the lookup from this key
1245 *	@max_items:	place up to this many items at *results
1246 *
1247 *	Performs an index-ascending scan of the tree for present items.  Places
1248 *	them at *@results and returns the number of items which were placed at
1249 *	*@results.
1250 *
1251 *	The implementation is naive.
1252 *
1253 *	Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1254 *	rcu_read_lock. In this case, rather than the returned results being
1255 *	an atomic snapshot of the tree at a single point in time, the
1256 *	semantics of an RCU protected gang lookup are as though multiple
1257 *	radix_tree_lookups have been issued in individual locks, and results
1258 *	stored in 'results'.
1259 */
1260unsigned int
1261radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1262			unsigned long first_index, unsigned int max_items)
1263{
1264	struct radix_tree_iter iter;
1265	void __rcu **slot;
1266	unsigned int ret = 0;
1267
1268	if (unlikely(!max_items))
1269		return 0;
1270
1271	radix_tree_for_each_slot(slot, root, &iter, first_index) {
1272		results[ret] = rcu_dereference_raw(*slot);
1273		if (!results[ret])
1274			continue;
1275		if (radix_tree_is_internal_node(results[ret])) {
1276			slot = radix_tree_iter_retry(&iter);
1277			continue;
1278		}
1279		if (++ret == max_items)
1280			break;
1281	}
1282
1283	return ret;
1284}
1285EXPORT_SYMBOL(radix_tree_gang_lookup);
1286
1287/**
1288 *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1289 *	                             based on a tag
1290 *	@root:		radix tree root
1291 *	@results:	where the results of the lookup are placed
1292 *	@first_index:	start the lookup from this key
1293 *	@max_items:	place up to this many items at *results
1294 *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
1295 *
1296 *	Performs an index-ascending scan of the tree for present items which
1297 *	have the tag indexed by @tag set.  Places the items at *@results and
1298 *	returns the number of items which were placed at *@results.
1299 */
1300unsigned int
1301radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1302		unsigned long first_index, unsigned int max_items,
1303		unsigned int tag)
1304{
1305	struct radix_tree_iter iter;
1306	void __rcu **slot;
1307	unsigned int ret = 0;
1308
1309	if (unlikely(!max_items))
1310		return 0;
1311
1312	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1313		results[ret] = rcu_dereference_raw(*slot);
1314		if (!results[ret])
1315			continue;
1316		if (radix_tree_is_internal_node(results[ret])) {
1317			slot = radix_tree_iter_retry(&iter);
1318			continue;
1319		}
1320		if (++ret == max_items)
1321			break;
1322	}
1323
1324	return ret;
1325}
1326EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1327
1328/**
1329 *	radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1330 *					  radix tree based on a tag
1331 *	@root:		radix tree root
1332 *	@results:	where the results of the lookup are placed
1333 *	@first_index:	start the lookup from this key
1334 *	@max_items:	place up to this many items at *results
1335 *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
1336 *
1337 *	Performs an index-ascending scan of the tree for present items which
1338 *	have the tag indexed by @tag set.  Places the slots at *@results and
1339 *	returns the number of slots which were placed at *@results.
1340 */
1341unsigned int
1342radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1343		void __rcu ***results, unsigned long first_index,
1344		unsigned int max_items, unsigned int tag)
1345{
1346	struct radix_tree_iter iter;
1347	void __rcu **slot;
1348	unsigned int ret = 0;
1349
1350	if (unlikely(!max_items))
1351		return 0;
1352
1353	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1354		results[ret] = slot;
1355		if (++ret == max_items)
1356			break;
1357	}
1358
1359	return ret;
1360}
1361EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1362
1363static bool __radix_tree_delete(struct radix_tree_root *root,
1364				struct radix_tree_node *node, void __rcu **slot)
1365{
1366	void *old = rcu_dereference_raw(*slot);
1367	int values = xa_is_value(old) ? -1 : 0;
1368	unsigned offset = get_slot_offset(node, slot);
1369	int tag;
1370
1371	if (is_idr(root))
1372		node_tag_set(root, node, IDR_FREE, offset);
1373	else
1374		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1375			node_tag_clear(root, node, tag, offset);
1376
1377	replace_slot(slot, NULL, node, -1, values);
1378	return node && delete_node(root, node);
1379}
1380
1381/**
1382 * radix_tree_iter_delete - delete the entry at this iterator position
1383 * @root: radix tree root
1384 * @iter: iterator state
1385 * @slot: pointer to slot
1386 *
1387 * Delete the entry at the position currently pointed to by the iterator.
1388 * This may result in the current node being freed; if it is, the iterator
1389 * is advanced so that it will not reference the freed memory.  This
1390 * function may be called without any locking if there are no other threads
1391 * which can access this tree.
1392 */
1393void radix_tree_iter_delete(struct radix_tree_root *root,
1394				struct radix_tree_iter *iter, void __rcu **slot)
1395{
1396	if (__radix_tree_delete(root, iter->node, slot))
1397		iter->index = iter->next_index;
1398}
1399EXPORT_SYMBOL(radix_tree_iter_delete);
1400
1401/**
1402 * radix_tree_delete_item - delete an item from a radix tree
1403 * @root: radix tree root
1404 * @index: index key
1405 * @item: expected item
1406 *
1407 * Remove @item at @index from the radix tree rooted at @root.
1408 *
1409 * Return: the deleted entry, or %NULL if it was not present
1410 * or the entry at the given @index was not @item.
1411 */
1412void *radix_tree_delete_item(struct radix_tree_root *root,
1413			     unsigned long index, void *item)
1414{
1415	struct radix_tree_node *node = NULL;
1416	void __rcu **slot = NULL;
1417	void *entry;
1418
1419	entry = __radix_tree_lookup(root, index, &node, &slot);
1420	if (!slot)
1421		return NULL;
1422	if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
1423						get_slot_offset(node, slot))))
1424		return NULL;
1425
1426	if (item && entry != item)
1427		return NULL;
1428
1429	__radix_tree_delete(root, node, slot);
1430
1431	return entry;
1432}
1433EXPORT_SYMBOL(radix_tree_delete_item);
1434
1435/**
1436 * radix_tree_delete - delete an entry from a radix tree
1437 * @root: radix tree root
1438 * @index: index key
1439 *
1440 * Remove the entry at @index from the radix tree rooted at @root.
1441 *
1442 * Return: The deleted entry, or %NULL if it was not present.
1443 */
1444void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1445{
1446	return radix_tree_delete_item(root, index, NULL);
1447}
1448EXPORT_SYMBOL(radix_tree_delete);
1449
1450/**
1451 *	radix_tree_tagged - test whether any items in the tree are tagged
1452 *	@root:		radix tree root
1453 *	@tag:		tag to test
1454 */
1455int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
1456{
1457	return root_tag_get(root, tag);
1458}
1459EXPORT_SYMBOL(radix_tree_tagged);
1460
1461/**
1462 * idr_preload - preload for idr_alloc()
1463 * @gfp_mask: allocation mask to use for preloading
1464 *
1465 * Preallocate memory to use for the next call to idr_alloc().  This function
1466 * returns with preemption disabled.  It will be enabled by idr_preload_end().
1467 */
1468void idr_preload(gfp_t gfp_mask)
1469{
1470	if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
1471		local_lock(&radix_tree_preloads.lock);
1472}
1473EXPORT_SYMBOL(idr_preload);
1474
1475void __rcu **idr_get_free(struct radix_tree_root *root,
1476			      struct radix_tree_iter *iter, gfp_t gfp,
1477			      unsigned long max)
1478{
1479	struct radix_tree_node *node = NULL, *child;
1480	void __rcu **slot = (void __rcu **)&root->xa_head;
1481	unsigned long maxindex, start = iter->next_index;
1482	unsigned int shift, offset = 0;
1483
1484 grow:
1485	shift = radix_tree_load_root(root, &child, &maxindex);
1486	if (!radix_tree_tagged(root, IDR_FREE))
1487		start = max(start, maxindex + 1);
1488	if (start > max)
1489		return ERR_PTR(-ENOSPC);
1490
1491	if (start > maxindex) {
1492		int error = radix_tree_extend(root, gfp, start, shift);
1493		if (error < 0)
1494			return ERR_PTR(error);
1495		shift = error;
1496		child = rcu_dereference_raw(root->xa_head);
1497	}
1498	if (start == 0 && shift == 0)
1499		shift = RADIX_TREE_MAP_SHIFT;
1500
1501	while (shift) {
1502		shift -= RADIX_TREE_MAP_SHIFT;
1503		if (child == NULL) {
1504			/* Have to add a child node.  */
1505			child = radix_tree_node_alloc(gfp, node, root, shift,
1506							offset, 0, 0);
1507			if (!child)
1508				return ERR_PTR(-ENOMEM);
1509			all_tag_set(child, IDR_FREE);
1510			rcu_assign_pointer(*slot, node_to_entry(child));
1511			if (node)
1512				node->count++;
1513		} else if (!radix_tree_is_internal_node(child))
1514			break;
1515
1516		node = entry_to_node(child);
1517		offset = radix_tree_descend(node, &child, start);
1518		if (!tag_get(node, IDR_FREE, offset)) {
1519			offset = radix_tree_find_next_bit(node, IDR_FREE,
1520							offset + 1);
1521			start = next_index(start, node, offset);
1522			if (start > max || start == 0)
1523				return ERR_PTR(-ENOSPC);
1524			while (offset == RADIX_TREE_MAP_SIZE) {
1525				offset = node->offset + 1;
1526				node = node->parent;
1527				if (!node)
1528					goto grow;
1529				shift = node->shift;
1530			}
1531			child = rcu_dereference_raw(node->slots[offset]);
1532		}
1533		slot = &node->slots[offset];
1534	}
1535
1536	iter->index = start;
1537	if (node)
1538		iter->next_index = 1 + min(max, (start | node_maxindex(node)));
1539	else
1540		iter->next_index = 1;
1541	iter->node = node;
1542	set_iter_tags(iter, node, offset, IDR_FREE);
1543
1544	return slot;
1545}
1546
1547/**
1548 * idr_destroy - release all internal memory from an IDR
1549 * @idr: idr handle
1550 *
1551 * After this function is called, the IDR is empty, and may be reused or
1552 * the data structure containing it may be freed.
1553 *
1554 * A typical clean-up sequence for objects stored in an idr tree will use
1555 * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1556 * free the memory used to keep track of those objects.
1557 */
1558void idr_destroy(struct idr *idr)
1559{
1560	struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
1561	if (radix_tree_is_internal_node(node))
1562		radix_tree_free_nodes(node);
1563	idr->idr_rt.xa_head = NULL;
1564	root_tag_set(&idr->idr_rt, IDR_FREE);
1565}
1566EXPORT_SYMBOL(idr_destroy);
1567
1568static void
1569radix_tree_node_ctor(void *arg)
1570{
1571	struct radix_tree_node *node = arg;
1572
1573	memset(node, 0, sizeof(*node));
1574	INIT_LIST_HEAD(&node->private_list);
1575}
1576
1577static int radix_tree_cpu_dead(unsigned int cpu)
1578{
1579	struct radix_tree_preload *rtp;
1580	struct radix_tree_node *node;
1581
1582	/* Free per-cpu pool of preloaded nodes */
1583	rtp = &per_cpu(radix_tree_preloads, cpu);
1584	while (rtp->nr) {
1585		node = rtp->nodes;
1586		rtp->nodes = node->parent;
1587		kmem_cache_free(radix_tree_node_cachep, node);
1588		rtp->nr--;
1589	}
1590	return 0;
1591}
1592
1593void __init radix_tree_init(void)
1594{
1595	int ret;
1596
1597	BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
1598	BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
1599	BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
1600	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1601			sizeof(struct radix_tree_node), 0,
1602			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1603			radix_tree_node_ctor);
1604	ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
1605					NULL, radix_tree_cpu_dead);
1606	WARN_ON(ret < 0);
1607}