Release 4.12 lib/radix-tree.c

/*
 * Copyright (C) 2001 Momchil Velikov
 * Portions Copyright (C) 2001 Christoph Hellwig
 * Copyright (C) 2005 SGI, Christoph Lameter
 * Copyright (C) 2006 Nick Piggin
 * Copyright (C) 2012 Konstantin Khlebnikov
 * Copyright (C) 2016 Intel, Matthew Wilcox
 * Copyright (C) 2016 Intel, Ross Zwisler
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kmemleak.h>
#include <linux/percpu.h>
#include <linux/preempt.h>		/* in_interrupt() */
#include <linux/radix-tree.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/string.h>


/* Number of nodes in fully populated tree of given height */

static unsigned long height_to_maxnodes[RADIX_TREE_MAX_PATH + 1] __read_mostly;

/*
 * Radix tree node cache.
 */

static struct kmem_cache *radix_tree_node_cachep;

/*
 * The radix tree is variable-height, so an insert operation not only has
 * to build the branch to its corresponding item, it also has to build the
 * branch to existing items if the size has to be increased (by
 * radix_tree_extend).
 *
 * The worst case is a zero height tree with just a single item at index 0,
 * and then inserting an item at index ULONG_MAX. This requires 2 new branches
 * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
 * Hence:
 */

#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)

/*
 * The IDR does not have to be as high as the radix tree since it uses
 * signed integers, not unsigned longs.
 */

#define IDR_INDEX_BITS		(8 /* CHAR_BIT */ * sizeof(int) - 1)

#define IDR_MAX_PATH		(DIV_ROUND_UP(IDR_INDEX_BITS, \
                                                RADIX_TREE_MAP_SHIFT))

#define IDR_PRELOAD_SIZE	(IDR_MAX_PATH * 2 - 1)

/*
 * The IDA is even shorter since it uses a bitmap at the last level.
 */

#define IDA_INDEX_BITS		(8 * sizeof(int) - 1 - ilog2(IDA_BITMAP_BITS))

#define IDA_MAX_PATH		(DIV_ROUND_UP(IDA_INDEX_BITS, \
                                                RADIX_TREE_MAP_SHIFT))

#define IDA_PRELOAD_SIZE	(IDA_MAX_PATH * 2 - 1)

/*
 * Per-cpu pool of preloaded nodes
 */

struct radix_tree_preload {
	
unsigned nr;
	/* nodes->parent points to next preallocated node */
	
struct radix_tree_node *nodes;
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };



static inline struct radix_tree_node *entry_to_node(void *ptr)
{
	return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
}

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static inline void *node_to_entry(void *ptr)
{
	return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
}

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#define RADIX_TREE_RETRY	node_to_entry(NULL)

#ifdef CONFIG_RADIX_TREE_MULTIORDER
/* Sibling slots point directly to another slot in the same node */

static inline

bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
{
	void __rcu **ptr = node;
	return (parent->slots <= ptr) &&
			(ptr < parent->slots + RADIX_TREE_MAP_SIZE);
}
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#else

static inline

bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
{
	return false;
}
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#endif


static inline unsigned long

get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
{
	return slot - parent->slots;
}

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static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
			struct radix_tree_node **nodep, unsigned long index)
{
	unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
	void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);

#ifdef CONFIG_RADIX_TREE_MULTIORDER
	if (radix_tree_is_internal_node(entry)) {
		if (is_sibling_entry(parent, entry)) {
			void __rcu **sibentry;
			sibentry = (void __rcu **) entry_to_node(entry);
			offset = get_slot_offset(parent, sibentry);
			entry = rcu_dereference_raw(*sibentry);
		}
	}
#endif

	*nodep = (void *)entry;
	return offset;
}

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static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
{
	return root->gfp_mask & __GFP_BITS_MASK;
}

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static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
		int offset)
{
	__set_bit(offset, node->tags[tag]);
}

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static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
		int offset)
{
	__clear_bit(offset, node->tags[tag]);
}

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static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
		int offset)
{
	return test_bit(offset, node->tags[tag]);
}

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static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
{
	root->gfp_mask |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
}

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static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
{
	root->gfp_mask &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
}

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static inline void root_tag_clear_all(struct radix_tree_root *root)
{
	root->gfp_mask &= (1 << ROOT_TAG_SHIFT) - 1;
}

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static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
{
	return (__force int)root->gfp_mask & (1 << (tag + ROOT_TAG_SHIFT));
}

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static inline unsigned root_tags_get(const struct radix_tree_root *root)
{
	return (__force unsigned)root->gfp_mask >> ROOT_TAG_SHIFT;
}

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static inline bool is_idr(const struct radix_tree_root *root)
{
	return !!(root->gfp_mask & ROOT_IS_IDR);
}

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/*
 * Returns 1 if any slot in the node has this tag set.
 * Otherwise returns 0.
 */


static inline int any_tag_set(const struct radix_tree_node *node,
							unsigned int tag)
{
	unsigned idx;
	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
		if (node->tags[tag][idx])
			return 1;
	}
	return 0;
}

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static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
{
	bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
}

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/**
 * radix_tree_find_next_bit - find the next set bit in a memory region
 *
 * @addr: The address to base the search on
 * @size: The bitmap size in bits
 * @offset: The bitnumber to start searching at
 *
 * Unrollable variant of find_next_bit() for constant size arrays.
 * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
 * Returns next bit offset, or size if nothing found.
 */

static __always_inline unsigned long

radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
			 unsigned long offset)
{
	const unsigned long *addr = node->tags[tag];

	if (offset < RADIX_TREE_MAP_SIZE) {
		unsigned long tmp;

		addr += offset / BITS_PER_LONG;
		tmp = *addr >> (offset % BITS_PER_LONG);
		if (tmp)
			return __ffs(tmp) + offset;
		offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
		while (offset < RADIX_TREE_MAP_SIZE) {
			tmp = *++addr;
			if (tmp)
				return __ffs(tmp) + offset;
			offset += BITS_PER_LONG;
		}
	}
	return RADIX_TREE_MAP_SIZE;
}

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static unsigned int iter_offset(const struct radix_tree_iter *iter)
{
	return (iter->index >> iter_shift(iter)) & RADIX_TREE_MAP_MASK;
}

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/*
 * The maximum index which can be stored in a radix tree
 */


static inline unsigned long shift_maxindex(unsigned int shift)
{
	return (RADIX_TREE_MAP_SIZE << shift) - 1;
}

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static inline unsigned long node_maxindex(const struct radix_tree_node *node)
{
	return shift_maxindex(node->shift);
}

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static unsigned long next_index(unsigned long index,
				const struct radix_tree_node *node,
				unsigned long offset)
{
	return (index & ~node_maxindex(node)) + (offset << node->shift);
}

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#ifndef __KERNEL__


static void dump_node(struct radix_tree_node *node, unsigned long index)
{
	unsigned long i;

	pr_debug("radix node: %p offset %d indices %lu-%lu parent %p tags %lx %lx %lx shift %d count %d exceptional %d\n",
		node, node->offset, index, index | node_maxindex(node),
		node->parent,
		node->tags[0][0], node->tags[1][0], node->tags[2][0],
		node->shift, node->count, node->exceptional);

	for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
		unsigned long first = index | (i << node->shift);
		unsigned long last = first | ((1UL << node->shift) - 1);
		void *entry = node->slots[i];
		if (!entry)
			continue;
		if (entry == RADIX_TREE_RETRY) {
			pr_debug("radix retry offset %ld indices %lu-%lu parent %p\n",
					i, first, last, node);
		} else if (!radix_tree_is_internal_node(entry)) {
			pr_debug("radix entry %p offset %ld indices %lu-%lu parent %p\n",
					entry, i, first, last, node);
		} else if (is_sibling_entry(node, entry)) {
			pr_debug("radix sblng %p offset %ld indices %lu-%lu parent %p val %p\n",
					entry, i, first, last, node,
					*(void **)entry_to_node(entry));
		} else {
			dump_node(entry_to_node(entry), first);
		}
	}
}

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/* For debug */


static void radix_tree_dump(struct radix_tree_root *root)
{
	pr_debug("radix root: %p rnode %p tags %x\n",
			root, root->rnode,
			root->gfp_mask >> ROOT_TAG_SHIFT);
	if (!radix_tree_is_internal_node(root->rnode))
		return;
	dump_node(entry_to_node(root->rnode), 0);
}

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static void dump_ida_node(void *entry, unsigned long index)
{
	unsigned long i;

	if (!entry)
		return;

	if (radix_tree_is_internal_node(entry)) {
		struct radix_tree_node *node = entry_to_node(entry);

		pr_debug("ida node: %p offset %d indices %lu-%lu parent %p free %lx shift %d count %d\n",
			node, node->offset, index * IDA_BITMAP_BITS,
			((index | node_maxindex(node)) + 1) *
				IDA_BITMAP_BITS - 1,
			node->parent, node->tags[0][0], node->shift,
			node->count);
		for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
			dump_ida_node(node->slots[i],
					index | (i << node->shift));
	} else if (radix_tree_exceptional_entry(entry)) {
		pr_debug("ida excp: %p offset %d indices %lu-%lu data %lx\n",
				entry, (int)(index & RADIX_TREE_MAP_MASK),
				index * IDA_BITMAP_BITS,
				index * IDA_BITMAP_BITS + BITS_PER_LONG -
					RADIX_TREE_EXCEPTIONAL_SHIFT,
				(unsigned long)entry >>
					RADIX_TREE_EXCEPTIONAL_SHIFT);
	} else {
		struct ida_bitmap *bitmap = entry;

		pr_debug("ida btmp: %p offset %d indices %lu-%lu data", bitmap,
				(int)(index & RADIX_TREE_MAP_MASK),
				index * IDA_BITMAP_BITS,
				(index + 1) * IDA_BITMAP_BITS - 1);
		for (i = 0; i < IDA_BITMAP_LONGS; i++)
			pr_cont(" %lx", bitmap->bitmap[i]);
		pr_cont("\n");
	}
}

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static void ida_dump(struct ida *ida)
{
	struct radix_tree_root *root = &ida->ida_rt;
	pr_debug("ida: %p node %p free %d\n", ida, root->rnode,
				root->gfp_mask >> ROOT_TAG_SHIFT);
	dump_ida_node(root->rnode, 0);
}
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#endif

/*
 * This assumes that the caller has performed appropriate preallocation, and
 * that the caller has pinned this thread of control to the current CPU.
 */

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 exceptional)
{
	struct radix_tree_node *ret = NULL;

	/*
         * Preload code isn't irq safe and it doesn't make sense to use
         * preloading during an interrupt anyway as all the allocations have
         * to be atomic. So just do normal allocation when in interrupt.
         */
	if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
		struct radix_tree_preload *rtp;

		/*
                 * Even if the caller has preloaded, try to allocate from the
                 * cache first for the new node to get accounted to the memory
                 * cgroup.
                 */
		ret = kmem_cache_alloc(radix_tree_node_cachep,
				       gfp_mask | __GFP_NOWARN);
		if (ret)
			goto out;

		/*
                 * Provided the caller has preloaded here, we will always
                 * succeed in getting a node here (and never reach
                 * kmem_cache_alloc)
                 */
		rtp = this_cpu_ptr(&radix_tree_preloads);
		if (rtp->nr) {
			ret = rtp->nodes;
			rtp->nodes = ret->parent;
			rtp->nr--;
		}
		/*
                 * Update the allocation stack trace as this is more useful
                 * for debugging.
                 */
		kmemleak_update_trace(ret);
		goto out;
	}
	ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
out:
	BUG_ON(radix_tree_is_internal_node(ret));
	if (ret) {
		ret->shift = shift;
		ret->offset = offset;
		ret->count = count;
		ret->exceptional = exceptional;
		ret->parent = parent;
		ret->root = root;
	}
	return ret;
}

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static void radix_tree_node_rcu_free(struct rcu_head *head)
{
	struct radix_tree_node *node =
			container_of(head, struct radix_tree_node, rcu_head);

	/*
         * Must only free zeroed nodes into the slab.  We can be left with
         * non-NULL entries by radix_tree_free_nodes, so clear the entries
         * and tags here.
         */
	memset(node->slots, 0, sizeof(node->slots));
	memset(node->tags, 0, sizeof(node->tags));
	INIT_LIST_HEAD(&node->private_list);

	kmem_cache_free(radix_tree_node_cachep, node);
}

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static inline void

radix_tree_node_free(struct radix_tree_node *node)
{
	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
}

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/*
 * Load up this CPU's radix_tree_node buffer with sufficient objects to
 * ensure that the addition of a single element in the tree cannot fail.  On
 * success, return zero, with preemption disabled.  On error, return -ENOMEM
 * with preemption not disabled.
 *
 * To make use of this facility, the radix tree must be initialised without
 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 */


static int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
{
	struct radix_tree_preload *rtp;
	struct radix_tree_node *node;
	int ret = -ENOMEM;

	/*
         * Nodes preloaded by one cgroup can be be used by another cgroup, so
         * they should never be accounted to any particular memory cgroup.
         */
	gfp_mask &= ~__GFP_ACCOUNT;

	preempt_disable();
	rtp = this_cpu_ptr(&radix_tree_preloads);
	while (rtp->nr < nr) {
		preempt_enable();
		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
		if (node == NULL)
			goto out;
		preempt_disable();
		rtp = this_cpu_ptr(&radix_tree_preloads);
		if (rtp->nr < nr) {
			node->parent = rtp->nodes;
			rtp->nodes = node;
			rtp->nr++;
		} else {
			kmem_cache_free(radix_tree_node_cachep, node);
		}
	}
	ret = 0;
out:
	return ret;
}

Contributors
Person
Tokens
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Commits
CommitProp
Nicholas Piggin
97
71.85%
2
22.22%
Kirill A. Shutemov
16
11.85%
2
22.22%
Matthew Wilcox
10
7.41%
2
22.22%
Vladimir Davydov
6
4.44%
1
11.11%
Christoph Lameter
4
2.96%
1
11.11%
Jan Kara
2
1.48%
1
11.11%
Total
135
100.00%
9
100.00%

/*
 * Load up this CPU's radix_tree_node buffer with sufficient objects to
 * ensure that the addition of a single element in the tree cannot fail.  On
 * success, return zero, with preemption disabled.  On error, return -ENOMEM
 * with preemption not disabled.
 *
 * To make use of this facility, the radix tree must be initialised without
 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 */


int radix_tree_preload(gfp_t gfp_mask)
{
	/* Warn on non-sensical use... */
	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
	return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
}
Contributors
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Jan Kara
21
80.77%
1
33.33%
Mel Gorman
3
11.54%
1
33.33%
Kirill A. Shutemov
2
7.69%
1
33.33%
Total
26
100.00%
3
100.00%


EXPORT_SYMBOL(radix_tree_preload);

/*
 * The same as above function, except we don't guarantee preloading happens.
 * We do it, if we decide it helps. On success, return zero with preemption
 * disabled. On error, return -ENOMEM with preemption not disabled.
 */


int radix_tree_maybe_preload(gfp_t gfp_mask)
{
	if (gfpflags_allow_blocking(gfp_mask))
		return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
	/* Preloading doesn't help anything with this gfp mask, skip it */
	preempt_disable();
	return 0;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Jan Kara
25
83.33%
1
33.33%
Mel Gorman
3
10.00%
1
33.33%
Kirill A. Shutemov
2
6.67%
1
33.33%
Total
30
100.00%
3
100.00%


EXPORT_SYMBOL(radix_tree_maybe_preload);

#ifdef CONFIG_RADIX_TREE_MULTIORDER
/*
 * Preload with enough objects to ensure that we can split a single entry
 * of order @old_order into many entries of size @new_order
 */


int radix_tree_split_preload(unsigned int old_order, unsigned int new_order,
							gfp_t gfp_mask)
{
	unsigned top = 1 << (old_order % RADIX_TREE_MAP_SHIFT);
	unsigned layers = (old_order / RADIX_TREE_MAP_SHIFT) -
				(new_order / RADIX_TREE_MAP_SHIFT);
	unsigned nr = 0;

	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
	BUG_ON(new_order >= old_order);

	while (layers--)
		nr = nr * RADIX_TREE_MAP_SIZE + 1;
	return __radix_tree_preload(gfp_mask, top * nr);
}
Contributors
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Matthew Wilcox
86
100.00%
1
100.00%
Total
86
100.00%
1
100.00%

#endif

/*
 * The same as function above, but preload number of nodes required to insert
 * (1 << order) continuous naturally-aligned elements.
 */


int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order)
{
	unsigned long nr_subtrees;
	int nr_nodes, subtree_height;

	/* Preloading doesn't help anything with this gfp mask, skip it */
	if (!gfpflags_allow_blocking(gfp_mask)) {
		preempt_disable();
		return 0;
	}

	/*
         * Calculate number and height of fully populated subtrees it takes to
         * store (1 << order) elements.
         */
	nr_subtrees = 1 << order;
	for (subtree_height = 0; nr_subtrees > RADIX_TREE_MAP_SIZE;
			subtree_height++)
		nr_subtrees >>= RADIX_TREE_MAP_SHIFT;

	/*
         * The worst case is zero height tree with a single item at index 0 and
         * then inserting items starting at ULONG_MAX - (1 << order).
         *
         * This requires RADIX_TREE_MAX_PATH nodes to build branch from root to
         * 0-index item.
         */
	nr_nodes = RADIX_TREE_MAX_PATH;

	/* Plus branch to fully populated subtrees. */
	nr_nodes += RADIX_TREE_MAX_PATH - subtree_height;

	/* Root node is shared. */
	nr_nodes--;

	/* Plus nodes required to build subtrees. */
	nr_nodes += nr_subtrees * height_to_maxnodes[subtree_height];

	return __radix_tree_preload(gfp_mask, nr_nodes);
}

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Kirill A. Shutemov
95
100.00%
1
100.00%
Total
95
100.00%
1
100.00%



static unsigned radix_tree_load_root(const struct radix_tree_root *root,
		struct radix_tree_node **nodep, unsigned long *maxindex)
{
	struct radix_tree_node *node = rcu_dereference_raw(root->rnode);

	*nodep = node;

	if (likely(radix_tree_is_internal_node(node))) {
		node = entry_to_node(node);
		*maxindex = node_maxindex(node);
		return node->shift + RADIX_TREE_MAP_SHIFT;
	}

	*maxindex = 0;
	return 0;
}

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Matthew Wilcox
82
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5
100.00%
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82
100.00%
5
100.00%

/*
 *      Extend a radix tree so it can store key @index.
 */


static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
				unsigned long index, unsigned int shift)
{
	void *entry;
	unsigned int maxshift;
	int tag;

	/* Figure out what the shift should be.  */
	maxshift = shift;
	while (index > shift_maxindex(maxshift))
		maxshift += RADIX_TREE_MAP_SHIFT;

	entry = rcu_dereference_raw(root->rnode);
	if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
		goto out;

	do {
		struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
							root, shift, 0, 1, 0);
		if (!node)
			return -ENOMEM;

		if (is_idr(root)) {
			all_tag_set(node, IDR_FREE);
			if (!root_tag_get(root, IDR_FREE)) {
				tag_clear(node, IDR_FREE, 0);
				root_tag_set(root, IDR_FREE);
			}
		} else {
			/* Propagate the aggregated tag info to the new child */
			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
				if (root_tag_get(root, tag))
					tag_set(node, tag, 0);
			}
		}

		BUG_ON(shift > BITS_PER_LONG);
		if (radix_tree_is_internal_node(entry)) {
			entry_to_node(entry)->parent = node;
		} else if (radix_tree_exceptional_entry(entry)) {
			/* Moving an exceptional root->rnode to a node */
			node->exceptional = 1;
		}
		/*
                 * entry was already in the radix tree, so we do not need
                 * rcu_assign_pointer here
                 */
		node->slots[0] = (void __rcu *)entry;
		entry = node_to_entry(node);
		rcu_assign_pointer(root->rnode, entry);
		shift += RADIX_TREE_MAP_SHIFT;
	} while (shift <= maxshift);
out:
	return maxshift + RADIX_TREE_MAP_SHIFT;
}

Contributors
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Matthew Wilcox
146
50.52%
13
59.09%
Andrew Morton
90
31.14%
2
9.09%
Johannes Weiner
19
6.57%
2
9.09%
Hugh Dickins
19
6.57%
1
4.55%
Nicholas Piggin
14
4.84%
3
13.64%
Jonathan Corbet
1
0.35%
1
4.55%
Total
289
100.00%
22
100.00%

/**
 *      radix_tree_shrink    -    shrink radix tree to minimum height
 *      @root           radix tree root
 */


static inline bool radix_tree_shrink(struct radix_tree_root *root,
				     radix_tree_update_node_t update_node,
				     void *private)
{
	bool shrunk = false;

	for (;;) {
		struct radix_tree_node *node = rcu_dereference_raw(root->rnode);
		struct radix_tree_node *child;

		if (!radix_tree_is_internal_node(