[userspace-rcu.git] / rcuja / rcuja.c

/*
 * rcuja/rcuja.c
 *
 * Userspace RCU library - RCU Judy Array
 *
 * Copyright 2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _LGPL_SOURCE
#include <stdint.h>
#include <errno.h>
#include <limits.h>
#include <string.h>
#include <urcu/rcuja.h>
#include <urcu/compiler.h>
#include <urcu/arch.h>
#include <assert.h>
#include <urcu-pointer.h>
#include <urcu/uatomic.h>
#include <stdint.h>

#include "rcuja-internal.h"
#include "bitfield.h"

#ifndef abs
#define abs_int(a)	((int) (a) > 0 ? (int) (a) : -((int) (a)))
#endif

enum cds_ja_type_class {
	RCU_JA_LINEAR = 0,	/* Type A */
			/* 32-bit: 1 to 25 children, 8 to 128 bytes */
			/* 64-bit: 1 to 28 children, 16 to 256 bytes */
	RCU_JA_POOL = 1,	/* Type B */
			/* 32-bit: 26 to 100 children, 256 to 512 bytes */
			/* 64-bit: 29 to 112 children, 512 to 1024 bytes */
	RCU_JA_PIGEON = 2,	/* Type C */
			/* 32-bit: 101 to 256 children, 1024 bytes */
			/* 64-bit: 113 to 256 children, 2048 bytes */
	/* Leaf nodes are implicit from their height in the tree */
	RCU_JA_NR_TYPES,

	RCU_JA_NULL,	/* not an encoded type, but keeps code regular */
};

struct cds_ja_type {
	enum cds_ja_type_class type_class;
	uint16_t min_child;		/* minimum number of children: 1 to 256 */
	uint16_t max_child;		/* maximum number of children: 1 to 256 */
	uint16_t max_linear_child;	/* per-pool max nr. children: 1 to 256 */
	uint16_t order;			/* node size is (1 << order), in bytes */
	uint16_t nr_pool_order;		/* number of pools */
	uint16_t pool_size_order;	/* pool size */
};

/*
 * Iteration on the array to find the right node size for the number of
 * children stops when it reaches .max_child == 256 (this is the largest
 * possible node size, which contains 256 children).
 * The min_child overlaps with the previous max_child to provide an
 * hysteresis loop to reallocation for patterns of cyclic add/removal
 * within the same node.
 * The node the index within the following arrays is represented on 3
 * bits. It identifies the node type, min/max number of children, and
 * the size order.
 * The max_child values for the RCU_JA_POOL below result from
 * statistical approximation: over million populations, the max_child
 * covers between 97% and 99% of the populations generated. Therefore, a
 * fallback should exist to cover the rare extreme population unbalance
 * cases, but it will not have a major impact on speed nor space
 * consumption, since those are rare cases.
 */

#if (CAA_BITS_PER_LONG < 64)
/* 32-bit pointers */
enum {
	ja_type_0_max_child = 1,
	ja_type_1_max_child = 3,
	ja_type_2_max_child = 6,
	ja_type_3_max_child = 12,
	ja_type_4_max_child = 25,
	ja_type_5_max_child = 48,
	ja_type_6_max_child = 92,
	ja_type_7_max_child = 256,
	ja_type_8_max_child = 0,	/* NULL */
};

enum {
	ja_type_0_max_linear_child = 1,
	ja_type_1_max_linear_child = 3,
	ja_type_2_max_linear_child = 6,
	ja_type_3_max_linear_child = 12,
	ja_type_4_max_linear_child = 25,
	ja_type_5_max_linear_child = 24,
	ja_type_6_max_linear_child = 23,
};

enum {
	ja_type_5_nr_pool_order = 1,
	ja_type_6_nr_pool_order = 2,
};

const struct cds_ja_type ja_types[] = {
	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 3, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 4, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 5, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 4, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 6, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 7, },

	/* Pools may fill sooner than max_child */
	{ .type_class = RCU_JA_POOL, .min_child = 20, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 8, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 7, },
	{ .type_class = RCU_JA_POOL, .min_child = 45, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 9, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 7, },

	/*
	 * Upon node removal below min_child, if child pool is filled
	 * beyond capacity, we roll back to pigeon.
	 */
	{ .type_class = RCU_JA_PIGEON, .min_child = 89, .max_child = ja_type_7_max_child, .order = 10, },

	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
};
#else /* !(CAA_BITS_PER_LONG < 64) */
/* 64-bit pointers */
enum {
	ja_type_0_max_child = 1,
	ja_type_1_max_child = 3,
	ja_type_2_max_child = 7,
	ja_type_3_max_child = 14,
	ja_type_4_max_child = 28,
	ja_type_5_max_child = 54,
	ja_type_6_max_child = 104,
	ja_type_7_max_child = 256,
	ja_type_8_max_child = 256,
};

enum {
	ja_type_0_max_linear_child = 1,
	ja_type_1_max_linear_child = 3,
	ja_type_2_max_linear_child = 7,
	ja_type_3_max_linear_child = 14,
	ja_type_4_max_linear_child = 28,
	ja_type_5_max_linear_child = 27,
	ja_type_6_max_linear_child = 26,
};

enum {
	ja_type_5_nr_pool_order = 1,
	ja_type_6_nr_pool_order = 2,
};

const struct cds_ja_type ja_types[] = {
	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 4, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 5, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 6, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 5, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 7, },
	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 8, },

	/* Pools may fill sooner than max_child. */
	{ .type_class = RCU_JA_POOL, .min_child = 22, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 9, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 8, },
	{ .type_class = RCU_JA_POOL, .min_child = 51, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 10, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 8, },

	/*
	 * Upon node removal below min_child, if child pool is filled
	 * beyond capacity, we roll back to pigeon.
	 */
	{ .type_class = RCU_JA_PIGEON, .min_child = 101, .max_child = ja_type_7_max_child, .order = 11, },

	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
};
#endif /* !(BITS_PER_LONG < 64) */

static inline __attribute__((unused))
void static_array_size_check(void)
{
	CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) < JA_TYPE_MAX_NR);
}

/*
 * The cds_ja_node contains the compressed node data needed for
 * read-side. For linear and pool node configurations, it starts with a
 * byte counting the number of children in the node.  Then, the
 * node-specific data is placed.
 * The node mutex, if any is needed, protecting concurrent updated of
 * each node is placed in a separate hash table indexed by node address.
 * For the pigeon configuration, the number of children is also kept in
 * a separate hash table, indexed by node address, because it is only
 * required for updates.
 */

#define DECLARE_LINEAR_NODE(index)								\
	struct {										\
		uint8_t nr_child;								\
		uint8_t child_value[ja_type_## index ##_max_linear_child];			\
		struct cds_ja_inode_flag *child_ptr[ja_type_## index ##_max_linear_child];	\
	}

#define DECLARE_POOL_NODE(index)								\
	struct {										\
		struct {									\
			uint8_t nr_child;							\
			uint8_t child_value[ja_type_## index ##_max_linear_child];		\
			struct cds_ja_inode_flag *child_ptr[ja_type_## index ##_max_linear_child]; \
		} linear[1U << ja_type_## index ##_nr_pool_order];				\
	}

struct cds_ja_inode {
	union {
		/* Linear configuration */
		DECLARE_LINEAR_NODE(0) conf_0;
		DECLARE_LINEAR_NODE(1) conf_1;
		DECLARE_LINEAR_NODE(2) conf_2;
		DECLARE_LINEAR_NODE(3) conf_3;
		DECLARE_LINEAR_NODE(4) conf_4;

		/* Pool configuration */
		DECLARE_POOL_NODE(5) conf_5;
		DECLARE_POOL_NODE(6) conf_6;

		/* Pigeon configuration */
		struct {
			struct cds_ja_inode_flag *child[ja_type_7_max_child];
		} conf_7;
		/* data aliasing nodes for computed accesses */
		uint8_t data[sizeof(struct cds_ja_inode_flag *) * ja_type_7_max_child];
	} u;
};

enum ja_recompact {
	JA_RECOMPACT_ADD_SAME,
	JA_RECOMPACT_ADD_NEXT,
	JA_RECOMPACT_DEL,
};

static
unsigned long node_fallback_count_distribution[JA_ENTRY_PER_NODE];
static
unsigned long nr_nodes_allocated, nr_nodes_freed;

static
struct cds_ja_inode *_ja_node_mask_ptr(struct cds_ja_inode_flag *node)
{
	return (struct cds_ja_inode *) (((unsigned long) node) & JA_PTR_MASK);
}

unsigned long ja_node_type(struct cds_ja_inode_flag *node)
{
	unsigned long type;

	if (_ja_node_mask_ptr(node) == NULL) {
		return NODE_INDEX_NULL;
	}
	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
	assert(type < (1UL << JA_TYPE_BITS));
	return type;
}

struct cds_ja_inode *ja_node_ptr(struct cds_ja_inode_flag *node)
{
	unsigned long type_index = ja_node_type(node);
	const struct cds_ja_type *type;

	type = &ja_types[type_index];
	switch (type->type_class) {
	case RCU_JA_LINEAR:
	case RCU_JA_PIGEON:	/* fall-through */
	case RCU_JA_NULL:	/* fall-through */
	default:		/* fall-through */
		return _ja_node_mask_ptr(node);
	case RCU_JA_POOL:
		switch (type->nr_pool_order) {
		case 1:
			return (struct cds_ja_inode *) (((unsigned long) node) & ~(JA_POOL_1D_MASK | JA_TYPE_MASK));
		case 2:
			return (struct cds_ja_inode *) (((unsigned long) node) & ~(JA_POOL_2D_MASK | JA_POOL_1D_MASK | JA_TYPE_MASK));
		default:
			assert(0);
		}
	}
}

struct cds_ja_inode *alloc_cds_ja_node(const struct cds_ja_type *ja_type)
{
	size_t len = 1U << ja_type->order;
	void *p;
	int ret;

	ret = posix_memalign(&p, len, len);
	if (ret || !p) {
		return NULL;
	}
	memset(p, 0, len);
	uatomic_inc(&nr_nodes_allocated);
	return p;
}

void free_cds_ja_node(struct cds_ja_inode *node)
{
	free(node);
	if (node)
		uatomic_inc(&nr_nodes_freed);
}

#define __JA_ALIGN_MASK(v, mask)	(((v) + (mask)) & ~(mask))
#define JA_ALIGN(v, align)		__JA_ALIGN_MASK(v, (typeof(v)) (align) - 1)
#define __JA_FLOOR_MASK(v, mask)	((v) & ~(mask))
#define JA_FLOOR(v, align)		__JA_FLOOR_MASK(v, (typeof(v)) (align) - 1)

static
uint8_t *align_ptr_size(uint8_t *ptr)
{
	return (uint8_t *) JA_ALIGN((unsigned long) ptr, sizeof(void *));
}

static
uint8_t ja_linear_node_get_nr_child(const struct cds_ja_type *type,
		struct cds_ja_inode *node)
{
	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
	return rcu_dereference(node->u.data[0]);
}

/*
 * The order in which values and pointers are does does not matter: if
 * a value is missing, we return NULL. If a value is there, but its
 * associated pointers is still NULL, we return NULL too.
 */
static
struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag ***node_flag_ptr,
		uint8_t n)
{
	uint8_t nr_child;
	uint8_t *values;
	struct cds_ja_inode_flag **pointers;
	struct cds_ja_inode_flag *ptr;
	unsigned int i;

	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);

	nr_child = ja_linear_node_get_nr_child(type, node);
	cmm_smp_rmb();	/* read nr_child before values and pointers */
	assert(nr_child <= type->max_linear_child);
	assert(type->type_class != RCU_JA_LINEAR || nr_child >= type->min_child);

	values = &node->u.data[1];
	for (i = 0; i < nr_child; i++) {
		if (CMM_LOAD_SHARED(values[i]) == n)
			break;
	}
	if (i >= nr_child) {
		if (caa_unlikely(node_flag_ptr))
			*node_flag_ptr = NULL;
		return NULL;
	}
	pointers = (struct cds_ja_inode_flag **) align_ptr_size(&values[type->max_linear_child]);
	ptr = rcu_dereference(pointers[i]);
	if (caa_unlikely(node_flag_ptr))
		*node_flag_ptr = &pointers[i];
	return ptr;
}

static
void ja_linear_node_get_ith_pos(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		uint8_t i,
		uint8_t *v,
		struct cds_ja_inode_flag **iter)
{
	uint8_t *values;
	struct cds_ja_inode_flag **pointers;

	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
	assert(i < ja_linear_node_get_nr_child(type, node));

	values = &node->u.data[1];
	*v = values[i];
	pointers = (struct cds_ja_inode_flag **) align_ptr_size(&values[type->max_linear_child]);
	*iter = pointers[i];
}

static
struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_inode_flag ***node_flag_ptr,
		uint8_t n)
{
	struct cds_ja_inode *linear;

	assert(type->type_class == RCU_JA_POOL);

	switch (type->nr_pool_order) {
	case 1:
	{
		unsigned long bitsel, index;

		bitsel = ja_node_pool_1d_bitsel(node_flag);
		assert(bitsel < CHAR_BIT);
		index = ((unsigned long) n >> bitsel) & 0x1;
		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
		break;
	}
	case 2:
	{
		unsigned long bitsel[2], index[2], rindex;

		ja_node_pool_2d_bitsel(node_flag, bitsel);
		assert(bitsel[0] < CHAR_BIT);
		assert(bitsel[1] < CHAR_BIT);
		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
		index[0] <<= 1;
		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
		rindex = index[0] | index[1];
		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
		break;
	}
	default:
		linear = NULL;
		assert(0);
	}
	return ja_linear_node_get_nth(type, linear, node_flag_ptr, n);
}

static
struct cds_ja_inode *ja_pool_node_get_ith_pool(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		uint8_t i)
{
	assert(type->type_class == RCU_JA_POOL);
	return (struct cds_ja_inode *)
		&node->u.data[(unsigned int) i << type->pool_size_order];
}

static
struct cds_ja_inode_flag *ja_pigeon_node_get_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag ***node_flag_ptr,
		uint8_t n)
{
	struct cds_ja_inode_flag **child_node_flag_ptr;
	struct cds_ja_inode_flag *child_node_flag;

	assert(type->type_class == RCU_JA_PIGEON);
	child_node_flag_ptr = &((struct cds_ja_inode_flag **) node->u.data)[n];
	child_node_flag = rcu_dereference(*child_node_flag_ptr);
	dbg_printf("ja_pigeon_node_get_nth child_node_flag_ptr %p\n",
		child_node_flag_ptr);
	if (caa_unlikely(node_flag_ptr))
		*node_flag_ptr = child_node_flag_ptr;
	return child_node_flag;
}

static
struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		uint8_t i)
{
	return ja_pigeon_node_get_nth(type, node, NULL, i);
}

/*
 * ja_node_get_nth: get nth item from a node.
 * node_flag is already rcu_dereference'd.
 */
static
struct cds_ja_inode_flag *ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
		struct cds_ja_inode_flag ***node_flag_ptr,
		uint8_t n)
{
	unsigned int type_index;
	struct cds_ja_inode *node;
	const struct cds_ja_type *type;

	node = ja_node_ptr(node_flag);
	assert(node != NULL);
	type_index = ja_node_type(node_flag);
	type = &ja_types[type_index];

	switch (type->type_class) {
	case RCU_JA_LINEAR:
		return ja_linear_node_get_nth(type, node,
				node_flag_ptr, n);
	case RCU_JA_POOL:
		return ja_pool_node_get_nth(type, node, node_flag,
				node_flag_ptr, n);
	case RCU_JA_PIGEON:
		return ja_pigeon_node_get_nth(type, node,
				node_flag_ptr, n);
	default:
		assert(0);
		return (void *) -1UL;
	}
}

static
int ja_linear_node_set_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag)
{
	uint8_t nr_child;
	uint8_t *values, *nr_child_ptr;
	struct cds_ja_inode_flag **pointers;
	unsigned int i, unused = 0;

	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);

	nr_child_ptr = &node->u.data[0];
	dbg_printf("linear set nth: n %u, nr_child_ptr %p\n",
		(unsigned int) n, nr_child_ptr);
	nr_child = *nr_child_ptr;
	assert(nr_child <= type->max_linear_child);

	values = &node->u.data[1];
	pointers = (struct cds_ja_inode_flag **) align_ptr_size(&values[type->max_linear_child]);
	/* Check if node value is already populated */
	for (i = 0; i < nr_child; i++) {
		if (values[i] == n) {
			if (pointers[i])
				return -EEXIST;
			else
				break;
		} else {
			if (!pointers[i])
				unused++;
		}
	}
	if (i == nr_child && nr_child >= type->max_linear_child) {
		if (unused)
			return -ERANGE;	/* recompact node */
		else
			return -ENOSPC;	/* No space left in this node type */
	}

	assert(pointers[i] == NULL);
	rcu_assign_pointer(pointers[i], child_node_flag);
	/* If we expanded the nr_child, increment it */
	if (i == nr_child) {
		CMM_STORE_SHARED(values[nr_child], n);
		/* write pointer and value before nr_child */
		cmm_smp_wmb();
		CMM_STORE_SHARED(*nr_child_ptr, nr_child + 1);
	}
	shadow_node->nr_child++;
	dbg_printf("linear set nth: %u child, shadow: %u child, for node %p shadow %p\n",
		(unsigned int) CMM_LOAD_SHARED(*nr_child_ptr),
		(unsigned int) shadow_node->nr_child,
		node, shadow_node);

	return 0;
}

static
int ja_pool_node_set_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag)
{
	struct cds_ja_inode *linear;

	assert(type->type_class == RCU_JA_POOL);

	switch (type->nr_pool_order) {
	case 1:
	{
		unsigned long bitsel, index;

		bitsel = ja_node_pool_1d_bitsel(node_flag);
		assert(bitsel < CHAR_BIT);
		index = ((unsigned long) n >> bitsel) & 0x1;
		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
		break;
	}
	case 2:
	{
		unsigned long bitsel[2], index[2], rindex;

		ja_node_pool_2d_bitsel(node_flag, bitsel);
		assert(bitsel[0] < CHAR_BIT);
		assert(bitsel[1] < CHAR_BIT);
		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
		index[0] <<= 1;
		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
		rindex = index[0] | index[1];
		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
		break;
	}
	default:
		linear = NULL;
		assert(0);
	}

	return ja_linear_node_set_nth(type, linear, shadow_node,
			n, child_node_flag);
}

static
int ja_pigeon_node_set_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag)
{
	struct cds_ja_inode_flag **ptr;

	assert(type->type_class == RCU_JA_PIGEON);
	ptr = &((struct cds_ja_inode_flag **) node->u.data)[n];
	if (*ptr)
		return -EEXIST;
	rcu_assign_pointer(*ptr, child_node_flag);
	shadow_node->nr_child++;
	return 0;
}

/*
 * _ja_node_set_nth: set nth item within a node. Return an error
 * (negative error value) if it is already there.
 */
static
int _ja_node_set_nth(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag)
{
	switch (type->type_class) {
	case RCU_JA_LINEAR:
		return ja_linear_node_set_nth(type, node, shadow_node, n,
				child_node_flag);
	case RCU_JA_POOL:
		return ja_pool_node_set_nth(type, node, node_flag, shadow_node, n,
				child_node_flag);
	case RCU_JA_PIGEON:
		return ja_pigeon_node_set_nth(type, node, shadow_node, n,
				child_node_flag);
	case RCU_JA_NULL:
		return -ENOSPC;
	default:
		assert(0);
		return -EINVAL;
	}

	return 0;
}

static
int ja_linear_node_clear_ptr(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag **node_flag_ptr)
{
	uint8_t nr_child;
	uint8_t *nr_child_ptr;

	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);

	nr_child_ptr = &node->u.data[0];
	nr_child = *nr_child_ptr;
	assert(nr_child <= type->max_linear_child);

	if (type->type_class == RCU_JA_LINEAR) {
		assert(!shadow_node->fallback_removal_count);
		if (shadow_node->nr_child <= type->min_child) {
			/* We need to try recompacting the node */
			return -EFBIG;
		}
	}
	dbg_printf("linear clear ptr: nr_child_ptr %p\n", nr_child_ptr);
	assert(*node_flag_ptr != NULL);
	rcu_assign_pointer(*node_flag_ptr, NULL);
	/*
	 * Value and nr_child are never changed (would cause ABA issue).
	 * Instead, we leave the pointer to NULL and recompact the node
	 * once in a while. It is allowed to set a NULL pointer to a new
	 * value without recompaction though.
	 * Only update the shadow node accounting.
	 */
	shadow_node->nr_child--;
	dbg_printf("linear clear ptr: %u child, shadow: %u child, for node %p shadow %p\n",
		(unsigned int) CMM_LOAD_SHARED(*nr_child_ptr),
		(unsigned int) shadow_node->nr_child,
		node, shadow_node);
	return 0;
}

static
int ja_pool_node_clear_ptr(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag **node_flag_ptr,
		uint8_t n)
{
	struct cds_ja_inode *linear;

	assert(type->type_class == RCU_JA_POOL);

	if (shadow_node->fallback_removal_count) {
		shadow_node->fallback_removal_count--;
	} else {
		/* We should try recompacting the node */
		if (shadow_node->nr_child <= type->min_child)
			return -EFBIG;
	}

	switch (type->nr_pool_order) {
	case 1:
	{
		unsigned long bitsel, index;

		bitsel = ja_node_pool_1d_bitsel(node_flag);
		assert(bitsel < CHAR_BIT);
		index = ((unsigned long) n >> bitsel) & type->nr_pool_order;
		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
		break;
	}
	case 2:
	{
		unsigned long bitsel[2], index[2], rindex;

		ja_node_pool_2d_bitsel(node_flag, bitsel);
		assert(bitsel[0] < CHAR_BIT);
		assert(bitsel[1] < CHAR_BIT);
		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
		index[0] <<= 1;
		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
		rindex = index[0] | index[1];
		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
		break;
	}
	default:
		linear = NULL;
		assert(0);
	}

	return ja_linear_node_clear_ptr(type, linear, shadow_node, node_flag_ptr);
}

static
int ja_pigeon_node_clear_ptr(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag **node_flag_ptr)
{
	assert(type->type_class == RCU_JA_PIGEON);

	if (shadow_node->fallback_removal_count) {
		shadow_node->fallback_removal_count--;
	} else {
		/* We should try recompacting the node */
		if (shadow_node->nr_child <= type->min_child)
			return -EFBIG;
	}
	dbg_printf("ja_pigeon_node_clear_ptr: clearing ptr: %p\n", *node_flag_ptr);
	rcu_assign_pointer(*node_flag_ptr, NULL);
	shadow_node->nr_child--;
	return 0;
}

/*
 * _ja_node_clear_ptr: clear ptr item within a node. Return an error
 * (negative error value) if it is not found (-ENOENT).
 */
static
int _ja_node_clear_ptr(const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag **node_flag_ptr,
		uint8_t n)
{
	switch (type->type_class) {
	case RCU_JA_LINEAR:
		return ja_linear_node_clear_ptr(type, node, shadow_node, node_flag_ptr);
	case RCU_JA_POOL:
		return ja_pool_node_clear_ptr(type, node, node_flag, shadow_node, node_flag_ptr, n);
	case RCU_JA_PIGEON:
		return ja_pigeon_node_clear_ptr(type, node, shadow_node, node_flag_ptr);
	case RCU_JA_NULL:
		return -ENOENT;
	default:
		assert(0);
		return -EINVAL;
	}

	return 0;
}

/*
 * Calculate bit distribution. Returns the bit (0 to 7) that splits the
 * distribution in two sub-distributions containing as much elements one
 * compared to the other.
 */
static
unsigned int ja_node_sum_distribution_1d(enum ja_recompact mode,
		struct cds_ja *ja,
		unsigned int type_index,
		const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag,
		struct cds_ja_inode_flag **nullify_node_flag_ptr)
{
	uint8_t nr_one[JA_BITS_PER_BYTE];
	unsigned int bitsel = 0, bit_i, overall_best_distance = UINT_MAX;
	unsigned int distrib_nr_child = 0;

	memset(nr_one, 0, sizeof(nr_one));

	switch (type->type_class) {
	case RCU_JA_LINEAR:
	{
		uint8_t nr_child =
			ja_linear_node_get_nr_child(type, node);
		unsigned int i;

		for (i = 0; i < nr_child; i++) {
			struct cds_ja_inode_flag *iter;
			uint8_t v;

			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
				if (v & (1U << bit_i))
					nr_one[bit_i]++;
			}
			distrib_nr_child++;
		}
		break;
	}
	case RCU_JA_POOL:
	{
		unsigned int pool_nr;

		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
			struct cds_ja_inode *pool =
				ja_pool_node_get_ith_pool(type,
					node, pool_nr);
			uint8_t nr_child =
				ja_linear_node_get_nr_child(type, pool);
			unsigned int j;

			for (j = 0; j < nr_child; j++) {
				struct cds_ja_inode_flag *iter;
				uint8_t v;

				ja_linear_node_get_ith_pos(type, pool,
						j, &v, &iter);
				if (!iter)
					continue;
				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
					continue;
				for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
					if (v & (1U << bit_i))
						nr_one[bit_i]++;
				}
				distrib_nr_child++;
			}
		}
		break;
	}
	case RCU_JA_PIGEON:
	{
		unsigned int i;

		assert(mode == JA_RECOMPACT_DEL);
		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
			struct cds_ja_inode_flag *iter;

			iter = ja_pigeon_node_get_ith_pos(type, node, i);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
				if (i & (1U << bit_i))
					nr_one[bit_i]++;
			}
			distrib_nr_child++;
		}
		break;
	}
	case RCU_JA_NULL:
		assert(mode == JA_RECOMPACT_ADD_NEXT);
		break;
	default:
		assert(0);
		break;
	}

	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
		for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
			if (n & (1U << bit_i))
				nr_one[bit_i]++;
		}
		distrib_nr_child++;
	}

	/*
	 * The best bit selector is that for which the number of ones is
	 * closest to half of the number of children in the
	 * distribution. We calculate the distance using the double of
	 * the sub-distribution sizes to eliminate truncation error.
	 */
	for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
		unsigned int distance_to_best;

		distance_to_best = abs_int((nr_one[bit_i] << 1U) - distrib_nr_child);
		if (distance_to_best < overall_best_distance) {
			overall_best_distance = distance_to_best;
			bitsel = bit_i;
		}
	}
	dbg_printf("1 dimension pool bit selection: (%u)\n", bitsel);
	return bitsel;
}

/*
 * Calculate bit distribution in two dimensions. Returns the two bits
 * (each 0 to 7) that splits the distribution in four sub-distributions
 * containing as much elements one compared to the other.
 */
static
void ja_node_sum_distribution_2d(enum ja_recompact mode,
		struct cds_ja *ja,
		unsigned int type_index,
		const struct cds_ja_type *type,
		struct cds_ja_inode *node,
		struct cds_ja_shadow_node *shadow_node,
		uint8_t n,
		struct cds_ja_inode_flag *child_node_flag,
		struct cds_ja_inode_flag **nullify_node_flag_ptr,
		unsigned int *_bitsel)
{
	uint8_t nr_2d_11[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
		nr_2d_10[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
		nr_2d_01[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
		nr_2d_00[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE];
	unsigned int bitsel[2] = { 0, 1 };
	unsigned int bit_i, bit_j;
	int overall_best_distance = INT_MAX;
	unsigned int distrib_nr_child = 0;

	memset(nr_2d_11, 0, sizeof(nr_2d_11));
	memset(nr_2d_10, 0, sizeof(nr_2d_10));
	memset(nr_2d_01, 0, sizeof(nr_2d_01));
	memset(nr_2d_00, 0, sizeof(nr_2d_00));

	switch (type->type_class) {
	case RCU_JA_LINEAR:
	{
		uint8_t nr_child =
			ja_linear_node_get_nr_child(type, node);
		unsigned int i;

		for (i = 0; i < nr_child; i++) {
			struct cds_ja_inode_flag *iter;
			uint8_t v;

			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
				for (bit_j = 0; bit_j < bit_i; bit_j++) {
					if ((v & (1U << bit_i)) && (v & (1U << bit_j))) {
						nr_2d_11[bit_i][bit_j]++;
					}
					if ((v & (1U << bit_i)) && !(v & (1U << bit_j))) {
						nr_2d_10[bit_i][bit_j]++;
					}
					if (!(v & (1U << bit_i)) && (v & (1U << bit_j))) {
						nr_2d_01[bit_i][bit_j]++;
					}
					if (!(v & (1U << bit_i)) && !(v & (1U << bit_j))) {
						nr_2d_00[bit_i][bit_j]++;
					}
				}
			}
			distrib_nr_child++;
		}
		break;
	}
	case RCU_JA_POOL:
	{
		unsigned int pool_nr;

		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
			struct cds_ja_inode *pool =
				ja_pool_node_get_ith_pool(type,
					node, pool_nr);
			uint8_t nr_child =
				ja_linear_node_get_nr_child(type, pool);
			unsigned int j;

			for (j = 0; j < nr_child; j++) {
				struct cds_ja_inode_flag *iter;
				uint8_t v;

				ja_linear_node_get_ith_pos(type, pool,
						j, &v, &iter);
				if (!iter)
					continue;
				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
					continue;
				for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
					for (bit_j = 0; bit_j < bit_i; bit_j++) {
						if ((v & (1U << bit_i)) && (v & (1U << bit_j))) {
							nr_2d_11[bit_i][bit_j]++;
						}
						if ((v & (1U << bit_i)) && !(v & (1U << bit_j))) {
							nr_2d_10[bit_i][bit_j]++;
						}
						if (!(v & (1U << bit_i)) && (v & (1U << bit_j))) {
							nr_2d_01[bit_i][bit_j]++;
						}
						if (!(v & (1U << bit_i)) && !(v & (1U << bit_j))) {
							nr_2d_00[bit_i][bit_j]++;
						}
					}
				}
				distrib_nr_child++;
			}
		}
		break;
	}
	case RCU_JA_PIGEON:
	{
		unsigned int i;

		assert(mode == JA_RECOMPACT_DEL);
		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
			struct cds_ja_inode_flag *iter;

			iter = ja_pigeon_node_get_ith_pos(type, node, i);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
				for (bit_j = 0; bit_j < bit_i; bit_j++) {
					if ((i & (1U << bit_i)) && (i & (1U << bit_j))) {
						nr_2d_11[bit_i][bit_j]++;
					}
					if ((i & (1U << bit_i)) && !(i & (1U << bit_j))) {
						nr_2d_10[bit_i][bit_j]++;
					}
					if (!(i & (1U << bit_i)) && (i & (1U << bit_j))) {
						nr_2d_01[bit_i][bit_j]++;
					}
					if (!(i & (1U << bit_i)) && !(i & (1U << bit_j))) {
						nr_2d_00[bit_i][bit_j]++;
					}
				}
			}
			distrib_nr_child++;
		}
		break;
	}
	case RCU_JA_NULL:
		assert(mode == JA_RECOMPACT_ADD_NEXT);
		break;
	default:
		assert(0);
		break;
	}

	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
		for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
			for (bit_j = 0; bit_j < bit_i; bit_j++) {
				if ((n & (1U << bit_i)) && (n & (1U << bit_j))) {
					nr_2d_11[bit_i][bit_j]++;
				}
				if ((n & (1U << bit_i)) && !(n & (1U << bit_j))) {
					nr_2d_10[bit_i][bit_j]++;
				}
				if (!(n & (1U << bit_i)) && (n & (1U << bit_j))) {
					nr_2d_01[bit_i][bit_j]++;
				}
				if (!(n & (1U << bit_i)) && !(n & (1U << bit_j))) {
					nr_2d_00[bit_i][bit_j]++;
				}
			}
		}
		distrib_nr_child++;
	}

	/*
	 * The best bit selector is that for which the number of nodes
	 * in each sub-class is closest to one-fourth of the number of
	 * children in the distribution. We calculate the distance using
	 * 4 times the size of the sub-distribution to eliminate
	 * truncation error.
	 */
	for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
		for (bit_j = 0; bit_j < bit_i; bit_j++) {
			int distance_to_best[4];

			distance_to_best[0] = (nr_2d_11[bit_i][bit_j] << 2U) - distrib_nr_child;
			distance_to_best[1] = (nr_2d_10[bit_i][bit_j] << 2U) - distrib_nr_child;
			distance_to_best[2] = (nr_2d_01[bit_i][bit_j] << 2U) - distrib_nr_child;
			distance_to_best[3] = (nr_2d_00[bit_i][bit_j] << 2U) - distrib_nr_child;

			/* Consider worse distance above best */
			if (distance_to_best[1] > 0 && distance_to_best[1] > distance_to_best[0])
				distance_to_best[0] = distance_to_best[1];
			if (distance_to_best[2] > 0 && distance_to_best[2] > distance_to_best[0])
				distance_to_best[0] = distance_to_best[2];
			if (distance_to_best[3] > 0 && distance_to_best[3] > distance_to_best[0])
				distance_to_best[0] = distance_to_best[3];

			/*
			 * If our worse distance is better than overall,
			 * we become new best candidate.
			 */
			if (distance_to_best[0] < overall_best_distance) {
				overall_best_distance = distance_to_best[0];
				bitsel[0] = bit_i;
				bitsel[1] = bit_j;
			}
		}
	}

	dbg_printf("2 dimensions pool bit selection: (%u,%u)\n", bitsel[0], bitsel[1]);

	/* Return our bit selection */
	_bitsel[0] = bitsel[0];
	_bitsel[1] = bitsel[1];
}

static
unsigned int find_nearest_type_index(unsigned int type_index,
		unsigned int nr_nodes)
{
	const struct cds_ja_type *type;

	assert(type_index != NODE_INDEX_NULL);
	if (nr_nodes == 0)
		return NODE_INDEX_NULL;
	for (;;) {
		type = &ja_types[type_index];
		if (nr_nodes < type->min_child)
			type_index--;
		else if (nr_nodes > type->max_child)
			type_index++;
		else
			break;
	}
	return type_index;
}

/*
 * ja_node_recompact_add: recompact a node, adding a new child.
 * Return 0 on success, -EAGAIN if need to retry, or other negative
 * error value otherwise.
 */
static
int ja_node_recompact(enum ja_recompact mode,
		struct cds_ja *ja,
		unsigned int old_type_index,
		const struct cds_ja_type *old_type,
		struct cds_ja_inode *old_node,
		struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag **old_node_flag_ptr, uint8_t n,
		struct cds_ja_inode_flag *child_node_flag,
		struct cds_ja_inode_flag **nullify_node_flag_ptr,
		int level)
{
	unsigned int new_type_index;
	struct cds_ja_inode *new_node;
	struct cds_ja_shadow_node *new_shadow_node = NULL;
	const struct cds_ja_type *new_type;
	struct cds_ja_inode_flag *new_node_flag, *old_node_flag;
	int ret;
	int fallback = 0;

	old_node_flag = *old_node_flag_ptr;

	/*
	 * Need to find nearest type index even for ADD_SAME, because
	 * this recompaction, when applied to linear nodes, will garbage
	 * collect dummy (NULL) entries, and can therefore cause a few
	 * linear representations to be skipped.
	 */
	switch (mode) {
	case JA_RECOMPACT_ADD_SAME:
		new_type_index = find_nearest_type_index(old_type_index,
			shadow_node->nr_child + 1);
		dbg_printf("Recompact for node with %u children\n",
			shadow_node->nr_child + 1);
		break;
	case JA_RECOMPACT_ADD_NEXT:
		if (!shadow_node || old_type_index == NODE_INDEX_NULL) {
			new_type_index = 0;
			dbg_printf("Recompact for NULL\n");
		} else {
			new_type_index = find_nearest_type_index(old_type_index,
				shadow_node->nr_child + 1);
			dbg_printf("Recompact for node with %u children\n",
				shadow_node->nr_child + 1);
		}
		break;
	case JA_RECOMPACT_DEL:
		new_type_index = find_nearest_type_index(old_type_index,
			shadow_node->nr_child - 1);
		dbg_printf("Recompact for node with %u children\n",
			shadow_node->nr_child - 1);
		break;
	default:
		assert(0);
	}

retry:		/* for fallback */
	dbg_printf("Recompact from type %d to type %d\n",
			old_type_index, new_type_index);
	new_type = &ja_types[new_type_index];
	if (new_type_index != NODE_INDEX_NULL) {
		new_node = alloc_cds_ja_node(new_type);
		if (!new_node)
			return -ENOMEM;

		if (new_type->type_class == RCU_JA_POOL) {
			switch (new_type->nr_pool_order) {
			case 1:
			{
				unsigned int node_distrib_bitsel;

				node_distrib_bitsel =
					ja_node_sum_distribution_1d(mode, ja,
						old_type_index, old_type,
						old_node, shadow_node,
						n, child_node_flag,
						nullify_node_flag_ptr);
				assert(!((unsigned long) new_node & JA_POOL_1D_MASK));
				new_node_flag = ja_node_flag_pool_1d(new_node,
					new_type_index, node_distrib_bitsel);
				break;
			}
			case 2:
			{
				unsigned int node_distrib_bitsel[2];

				ja_node_sum_distribution_2d(mode, ja,
					old_type_index, old_type,
					old_node, shadow_node,
					n, child_node_flag,
					nullify_node_flag_ptr,
					node_distrib_bitsel);
				assert(!((unsigned long) new_node & JA_POOL_1D_MASK));
				assert(!((unsigned long) new_node & JA_POOL_2D_MASK));
				new_node_flag = ja_node_flag_pool_2d(new_node,
					new_type_index, node_distrib_bitsel);
				break;
			}
			default:
				assert(0);
			}
		} else {
			new_node_flag = ja_node_flag(new_node, new_type_index);
		}

		dbg_printf("Recompact inherit lock from %p\n", shadow_node);
		new_shadow_node = rcuja_shadow_set(ja->ht, new_node_flag, shadow_node, ja, level);
		if (!new_shadow_node) {
			free_cds_ja_node(new_node);
			return -ENOMEM;
		}
		if (fallback)
			new_shadow_node->fallback_removal_count =
						JA_FALLBACK_REMOVAL_COUNT;
	} else {
		new_node = NULL;
		new_node_flag = NULL;
	}

	assert(mode != JA_RECOMPACT_ADD_NEXT || old_type->type_class != RCU_JA_PIGEON);

	if (new_type_index == NODE_INDEX_NULL)
		goto skip_copy;

	switch (old_type->type_class) {
	case RCU_JA_LINEAR:
	{
		uint8_t nr_child =
			ja_linear_node_get_nr_child(old_type, old_node);
		unsigned int i;

		for (i = 0; i < nr_child; i++) {
			struct cds_ja_inode_flag *iter;
			uint8_t v;

			ja_linear_node_get_ith_pos(old_type, old_node, i, &v, &iter);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
					new_shadow_node,
					v, iter);
			if (new_type->type_class == RCU_JA_POOL && ret) {
				goto fallback_toosmall;
			}
			assert(!ret);
		}
		break;
	}
	case RCU_JA_POOL:
	{
		unsigned int pool_nr;

		for (pool_nr = 0; pool_nr < (1U << old_type->nr_pool_order); pool_nr++) {
			struct cds_ja_inode *pool =
				ja_pool_node_get_ith_pool(old_type,
					old_node, pool_nr);
			uint8_t nr_child =
				ja_linear_node_get_nr_child(old_type, pool);
			unsigned int j;

			for (j = 0; j < nr_child; j++) {
				struct cds_ja_inode_flag *iter;
				uint8_t v;

				ja_linear_node_get_ith_pos(old_type, pool,
						j, &v, &iter);
				if (!iter)
					continue;
				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
					continue;
				ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
						new_shadow_node,
						v, iter);
				if (new_type->type_class == RCU_JA_POOL
						&& ret) {
					goto fallback_toosmall;
				}
				assert(!ret);
			}
		}
		break;
	}
	case RCU_JA_NULL:
		assert(mode == JA_RECOMPACT_ADD_NEXT);
		break;
	case RCU_JA_PIGEON:
	{
		unsigned int i;

		assert(mode == JA_RECOMPACT_DEL);
		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
			struct cds_ja_inode_flag *iter;

			iter = ja_pigeon_node_get_ith_pos(old_type, old_node, i);
			if (!iter)
				continue;
			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
				continue;
			ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
					new_shadow_node,
					i, iter);
			if (new_type->type_class == RCU_JA_POOL && ret) {
				goto fallback_toosmall;
			}
			assert(!ret);
		}
		break;
	}
	default:
		assert(0);
		ret = -EINVAL;
		goto end;
	}
skip_copy:

	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
		/* add node */
		ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
				new_shadow_node,
				n, child_node_flag);
		if (new_type->type_class == RCU_JA_POOL && ret) {
			goto fallback_toosmall;
		}
		assert(!ret);
	}

	if (fallback) {
		dbg_printf("Using fallback for %u children, node type index: %u, mode %s\n",
			new_shadow_node->nr_child, old_type_index, mode == JA_RECOMPACT_ADD_NEXT ? "add_next" :
				(mode == JA_RECOMPACT_DEL ? "del" : "add_same"));
		uatomic_inc(&node_fallback_count_distribution[new_shadow_node->nr_child]);
	}

	/* Return pointer to new recompacted node through old_node_flag_ptr */
	*old_node_flag_ptr = new_node_flag;
	if (old_node) {
		int flags;

		flags = RCUJA_SHADOW_CLEAR_FREE_NODE;
		/*
		 * It is OK to free the lock associated with a node
		 * going to NULL, since we are holding the parent lock.
		 * This synchronizes removal with re-add of that node.
		 */
		if (new_type_index == NODE_INDEX_NULL)
			flags |= RCUJA_SHADOW_CLEAR_FREE_LOCK;
		ret = rcuja_shadow_clear(ja->ht, old_node_flag, shadow_node,
				flags);
		assert(!ret);
	}

	ret = 0;
end:
	return ret;

fallback_toosmall:
	/* fallback if next pool is too small */
	assert(new_shadow_node);
	ret = rcuja_shadow_clear(ja->ht, new_node_flag, new_shadow_node,
			RCUJA_SHADOW_CLEAR_FREE_NODE);
	assert(!ret);

	switch (mode) {
	case JA_RECOMPACT_ADD_SAME:
		/*
		 * JA_RECOMPACT_ADD_SAME is only triggered if a linear
		 * node within a pool has unused entries. It should
		 * therefore _never_ be too small.
		 */
		assert(0);

		/* Fall-through */
	case JA_RECOMPACT_ADD_NEXT:
	{
		const struct cds_ja_type *next_type;

		/*
		 * Recompaction attempt on add failed. Should only
		 * happen if target node type is pool. Caused by
		 * hard-to-split distribution. Recompact using the next
		 * distribution size.
		 */
		assert(new_type->type_class == RCU_JA_POOL);
		next_type = &ja_types[new_type_index + 1];
		/*
		 * Try going to the next pool size if our population
		 * fits within its range. This is not flagged as a
		 * fallback.
		 */
		if (shadow_node->nr_child + 1 >= next_type->min_child
				&& shadow_node->nr_child + 1 <= next_type->max_child) {
			new_type_index++;
			goto retry;
		} else {
			new_type_index++;
			dbg_printf("Add fallback to type %d\n", new_type_index);
			uatomic_inc(&ja->nr_fallback);
			fallback = 1;
			goto retry;
		}
		break;
	}
	case JA_RECOMPACT_DEL:
		/*
		 * Recompaction attempt on delete failed. Should only
		 * happen if target node type is pool. This is caused by
		 * a hard-to-split distribution. Recompact on same node
		 * size, but flag current node as "fallback" to ensure
		 * we don't attempt recompaction before some activity
		 * has reshuffled our node.
		 */
		assert(new_type->type_class == RCU_JA_POOL);
		new_type_index = old_type_index;
		dbg_printf("Delete fallback keeping type %d\n", new_type_index);
		uatomic_inc(&ja->nr_fallback);
		fallback = 1;
		goto retry;
	default:
		assert(0);
		return -EINVAL;
	}

	/*
	 * Last resort fallback: pigeon.
	 */
	new_type_index = (1UL << JA_TYPE_BITS) - 1;
	dbg_printf("Fallback to type %d\n", new_type_index);
	uatomic_inc(&ja->nr_fallback);
	fallback = 1;
	goto retry;
}

/*
 * Return 0 on success, -EAGAIN if need to retry, or other negative
 * error value otherwise.
 */
static
int ja_node_set_nth(struct cds_ja *ja,
		struct cds_ja_inode_flag **node_flag, uint8_t n,
		struct cds_ja_inode_flag *child_node_flag,
		struct cds_ja_shadow_node *shadow_node,
		int level)
{
	int ret;
	unsigned int type_index;
	const struct cds_ja_type *type;
	struct cds_ja_inode *node;

	dbg_printf("ja_node_set_nth for n=%u, node %p, shadow %p\n",
		(unsigned int) n, ja_node_ptr(*node_flag), shadow_node);

	node = ja_node_ptr(*node_flag);
	type_index = ja_node_type(*node_flag);
	type = &ja_types[type_index];
	ret = _ja_node_set_nth(type, node, *node_flag, shadow_node,
			n, child_node_flag);
	switch (ret) {
	case -ENOSPC:
		/* Not enough space in node, need to recompact to next type. */
		ret = ja_node_recompact(JA_RECOMPACT_ADD_NEXT, ja, type_index, type, node,
				shadow_node, node_flag, n, child_node_flag, NULL, level);
		break;
	case -ERANGE:
		/* Node needs to be recompacted. */
		ret = ja_node_recompact(JA_RECOMPACT_ADD_SAME, ja, type_index, type, node,
				shadow_node, node_flag, n, child_node_flag, NULL, level);
		break;
	}
	return ret;
}

/*
 * Return 0 on success, -EAGAIN if need to retry, or other negative
 * error value otherwise.
 */
static
int ja_node_clear_ptr(struct cds_ja *ja,
		struct cds_ja_inode_flag **node_flag_ptr,	/* Pointer to location to nullify */
		struct cds_ja_inode_flag **parent_node_flag_ptr,	/* Address of parent ptr in its parent */
		struct cds_ja_shadow_node *shadow_node,		/* of parent */
		uint8_t n, int level)
{
	int ret;
	unsigned int type_index;
	const struct cds_ja_type *type;
	struct cds_ja_inode *node;

	dbg_printf("ja_node_clear_ptr for node %p, shadow %p, target ptr %p\n",
		ja_node_ptr(*parent_node_flag_ptr), shadow_node, node_flag_ptr);

	node = ja_node_ptr(*parent_node_flag_ptr);
	type_index = ja_node_type(*parent_node_flag_ptr);
	type = &ja_types[type_index];
	ret = _ja_node_clear_ptr(type, node, *parent_node_flag_ptr, shadow_node, node_flag_ptr, n);
	if (ret == -EFBIG) {
		/* Should try recompaction. */
		ret = ja_node_recompact(JA_RECOMPACT_DEL, ja, type_index, type, node,
				shadow_node, parent_node_flag_ptr, n, NULL,
				node_flag_ptr, level);
	}
	return ret;
}

struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key)
{
	unsigned int tree_depth, i;
	struct cds_ja_inode_flag *node_flag;
	struct cds_hlist_head head = { NULL };

	if (caa_unlikely(key > ja->key_max))
		return head;
	tree_depth = ja->tree_depth;
	node_flag = rcu_dereference(ja->root);

	/* level 0: root node */
	if (!ja_node_ptr(node_flag))
		return head;

	for (i = 1; i < tree_depth; i++) {
		uint8_t iter_key;

		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
		node_flag = ja_node_get_nth(node_flag, NULL, iter_key);
		dbg_printf("cds_ja_lookup iter key lookup %u finds node_flag %p\n",
				(unsigned int) iter_key, node_flag);
		if (!ja_node_ptr(node_flag))
			return head;
	}

	/* Last level lookup succeded. We got an actual match. */
	head.next = (struct cds_hlist_node *) node_flag;
	return head;
}

/*
 * We reached an unpopulated node. Create it and the children we need,
 * and then attach the entire branch to the current node. This may
 * trigger recompaction of the current node.  Locks needed: node lock
 * (for add), and, possibly, parent node lock (to update pointer due to
 * node recompaction).
 *
 * First take node lock, check if recompaction is needed, then take
 * parent lock (if needed).  Then we can proceed to create the new
 * branch. Publish the new branch, and release locks.
 * TODO: we currently always take the parent lock even when not needed.
 */
static
int ja_attach_node(struct cds_ja *ja,
		struct cds_ja_inode_flag **attach_node_flag_ptr,
		struct cds_ja_inode_flag *attach_node_flag,
		struct cds_ja_inode_flag *parent_attach_node_flag,
		struct cds_ja_inode_flag **old_node_flag_ptr,
		struct cds_ja_inode_flag *old_node_flag,
		uint64_t key,
		unsigned int level,
		struct cds_ja_node *child_node)
{
	struct cds_ja_shadow_node *shadow_node = NULL,
			*parent_shadow_node = NULL;
	struct cds_hlist_head head;
	struct cds_ja_inode_flag *iter_node_flag, *iter_dest_node_flag;
	int ret, i;
	struct cds_ja_inode_flag *created_nodes[JA_MAX_DEPTH];
	int nr_created_nodes = 0;

	dbg_printf("Attach node at level %u (old_node_flag %p, attach_node_flag_ptr %p attach_node_flag %p, parent_attach_node_flag %p)\n",
		level, old_node_flag, attach_node_flag_ptr, attach_node_flag, parent_attach_node_flag);

	assert(!old_node_flag);
	if (attach_node_flag) {
		shadow_node = rcuja_shadow_lookup_lock(ja->ht, attach_node_flag);
		if (!shadow_node) {
			ret = -EAGAIN;
			goto end;
		}
	}
	if (parent_attach_node_flag) {
		parent_shadow_node = rcuja_shadow_lookup_lock(ja->ht,
						parent_attach_node_flag);
		if (!parent_shadow_node) {
			ret = -EAGAIN;
			goto unlock_shadow;
		}
	}

	if (old_node_flag_ptr && ja_node_ptr(*old_node_flag_ptr)) {
		/*
		 * Target node has been updated between RCU lookup and
		 * lock acquisition. We need to re-try lookup and
		 * attach.
		 */
		ret = -EAGAIN;
		goto unlock_parent;
	}

	if (attach_node_flag_ptr && ja_node_ptr(*attach_node_flag_ptr) !=
			ja_node_ptr(attach_node_flag)) {
		/*
		 * Target node has been updated between RCU lookup and
		 * lock acquisition. We need to re-try lookup and
		 * attach.
		 */
		ret = -EAGAIN;
		goto unlock_parent;
	}

	/* Create new branch, starting from bottom */
	CDS_INIT_HLIST_HEAD(&head);
	cds_hlist_add_head_rcu(&child_node->list, &head);
	iter_node_flag = (struct cds_ja_inode_flag *) head.next;

	for (i = ja->tree_depth - 1; i >= (int) level; i--) {
		uint8_t iter_key;

		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - i - 1)));
		dbg_printf("branch creation level %d, key %u\n",
				i, (unsigned int) iter_key);
		iter_dest_node_flag = NULL;
		ret = ja_node_set_nth(ja, &iter_dest_node_flag,
			iter_key,
			iter_node_flag,
			NULL, i);
		if (ret)
			goto check_error;
		created_nodes[nr_created_nodes++] = iter_dest_node_flag;
		iter_node_flag = iter_dest_node_flag;
	}
	assert(level > 0);

	/* Publish branch */
	if (level == 1) {
		/*
		 * Attaching to root node.
		 */
		rcu_assign_pointer(ja->root, iter_node_flag);
	} else {
		uint8_t iter_key;

		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - level)));
		dbg_printf("publish branch at level %d, key %u\n",
				level - 1, (unsigned int) iter_key);
		/* We need to use set_nth on the previous level. */
		iter_dest_node_flag = attach_node_flag;
		ret = ja_node_set_nth(ja, &iter_dest_node_flag,
			iter_key,
			iter_node_flag,
			shadow_node, level - 1);
		if (ret)
			goto check_error;
		/*
		 * Attach branch
		 */
		rcu_assign_pointer(*attach_node_flag_ptr, iter_dest_node_flag);
	}

	/* Success */
	ret = 0;

check_error:
	if (ret) {
		for (i = 0; i < nr_created_nodes; i++) {
			int tmpret;
			int flags;

			flags = RCUJA_SHADOW_CLEAR_FREE_LOCK;
			if (i)
				flags |= RCUJA_SHADOW_CLEAR_FREE_NODE;
			tmpret = rcuja_shadow_clear(ja->ht,
					created_nodes[i],
					NULL,
					flags);
			assert(!tmpret);
		}
	}
unlock_parent:
	if (parent_shadow_node)
		rcuja_shadow_unlock(parent_shadow_node);
unlock_shadow:
	if (shadow_node)
		rcuja_shadow_unlock(shadow_node);
end:
	return ret;
}

/*
 * Lock the parent containing the hlist head pointer, and add node to list of
 * duplicates. Failure can happen if concurrent update changes the
 * parent before we get the lock. We return -EAGAIN in that case.
 * Return 0 on success, negative error value on failure.
 */
static
int ja_chain_node(struct cds_ja *ja,
		struct cds_ja_inode_flag *parent_node_flag,
		struct cds_ja_inode_flag **node_flag_ptr,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_node *node)
{
	struct cds_ja_shadow_node *shadow_node;
	int ret = 0;

	shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
	if (!shadow_node) {
		return -EAGAIN;
	}
	if (ja_node_ptr(*node_flag_ptr) != ja_node_ptr(node_flag)) {
		ret = -EAGAIN;
		goto end;
	}
	cds_hlist_add_head_rcu(&node->list, (struct cds_hlist_head *) node_flag_ptr);
end:
	rcuja_shadow_unlock(shadow_node);
	return ret;
}

static
int _cds_ja_add(struct cds_ja *ja, uint64_t key,
		struct cds_ja_node *new_node,
		struct cds_ja_node **unique_node_ret)
{
	unsigned int tree_depth, i;
	struct cds_ja_inode_flag *attach_node_flag,
		*parent_node_flag,
		*parent2_node_flag,
		*node_flag,
		*parent_attach_node_flag;
	struct cds_ja_inode_flag **attach_node_flag_ptr,
		**parent_node_flag_ptr,
		**node_flag_ptr;
	int ret;

	if (caa_unlikely(key > ja->key_max)) {
		return -EINVAL;
	}
	tree_depth = ja->tree_depth;

retry:
	dbg_printf("cds_ja_add attempt: key %" PRIu64 ", node %p\n",
		key, new_node);
	parent2_node_flag = NULL;
	parent_node_flag =
		(struct cds_ja_inode_flag *) &ja->root;	/* Use root ptr address as key for mutex */
	parent_node_flag_ptr = NULL;
	node_flag = rcu_dereference(ja->root);
	node_flag_ptr = &ja->root;

	/* Iterate on all internal levels */
	for (i = 1; i < tree_depth; i++) {
		uint8_t iter_key;

		if (!ja_node_ptr(node_flag))
			break;
		dbg_printf("cds_ja_add iter parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);
		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
		parent2_node_flag = parent_node_flag;
		parent_node_flag = node_flag;
		parent_node_flag_ptr = node_flag_ptr;
		node_flag = ja_node_get_nth(node_flag,
			&node_flag_ptr,
			iter_key);
	}

	/*
	 * We reached either bottom of tree or internal NULL node,
	 * simply add node to last internal level, or chain it if key is
	 * already present.
	 */
	if (!ja_node_ptr(node_flag)) {
		dbg_printf("cds_ja_add NULL parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);

		attach_node_flag = parent_node_flag;
		attach_node_flag_ptr = parent_node_flag_ptr;
		parent_attach_node_flag = parent2_node_flag;

		ret = ja_attach_node(ja, attach_node_flag_ptr,
				attach_node_flag,
				parent_attach_node_flag,
				node_flag_ptr,
				node_flag,
				key, i, new_node);
	} else {
		if (unique_node_ret) {
			*unique_node_ret = (struct cds_ja_node *) ja_node_ptr(node_flag);
			return -EEXIST;
		}

		dbg_printf("cds_ja_add duplicate parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);

		attach_node_flag = node_flag;
		attach_node_flag_ptr = node_flag_ptr;
		parent_attach_node_flag = parent_node_flag;

		ret = ja_chain_node(ja,
			parent_attach_node_flag,
			attach_node_flag_ptr,
			attach_node_flag,
			new_node);
	}
	if (ret == -EAGAIN || ret == -EEXIST)
		goto retry;

	return ret;
}

int cds_ja_add(struct cds_ja *ja, uint64_t key,
		struct cds_ja_node *new_node)
{
	return _cds_ja_add(ja, key, new_node, NULL);
}

struct cds_ja_node *cds_ja_add_unique(struct cds_ja *ja, uint64_t key,
		struct cds_ja_node *new_node)
{
	int ret;
	struct cds_ja_node *ret_node;

	ret = _cds_ja_add(ja, key, new_node, &ret_node);
	if (ret == -EEXIST)
		return ret_node;
	else
		return new_node;
}

/*
 * Note: there is no need to lookup the pointer address associated with
 * each node's nth item after taking the lock: it's already been done by
 * cds_ja_del while holding the rcu read-side lock, and our node rules
 * ensure that when a match value -> pointer is found in a node, it is
 * _NEVER_ changed for that node without recompaction, and recompaction
 * reallocates the node.
 * However, when a child is removed from "linear" nodes, its pointer
 * is set to NULL. We therefore check, while holding the locks, if this
 * pointer is NULL, and return -ENOENT to the caller if it is the case.
 */
static
int ja_detach_node(struct cds_ja *ja,
		struct cds_ja_inode_flag **snapshot,
		struct cds_ja_inode_flag ***snapshot_ptr,
		uint8_t *snapshot_n,
		int nr_snapshot,
		uint64_t key,
		struct cds_ja_node *node)
{
	struct cds_ja_shadow_node *shadow_nodes[JA_MAX_DEPTH];
	struct cds_ja_inode_flag **node_flag_ptr = NULL,
			*parent_node_flag = NULL,
			**parent_node_flag_ptr = NULL;
	struct cds_ja_inode_flag *iter_node_flag;
	int ret, i, nr_shadow = 0, nr_clear = 0, nr_branch = 0;
	uint8_t n = 0;

	assert(nr_snapshot == ja->tree_depth + 1);

	/*
	 * From the last internal level node going up, get the node
	 * lock, check if the node has only one child left. If it is the
	 * case, we continue iterating upward. When we reach a node
	 * which has more that one child left, we lock the parent, and
	 * proceed to the node deletion (removing its children too).
	 */
	for (i = nr_snapshot - 2; i >= 1; i--) {
		struct cds_ja_shadow_node *shadow_node;

		shadow_node = rcuja_shadow_lookup_lock(ja->ht,
					snapshot[i]);
		if (!shadow_node) {
			ret = -EAGAIN;
			goto end;
		}
		shadow_nodes[nr_shadow++] = shadow_node;

		/*
		 * Check if node has been removed between RCU
		 * lookup and lock acquisition.
		 */
		assert(snapshot_ptr[i + 1]);
		if (ja_node_ptr(*snapshot_ptr[i + 1])
				!= ja_node_ptr(snapshot[i + 1])) {
			ret = -ENOENT;
			goto end;
		}

		assert(shadow_node->nr_child > 0);
		if (shadow_node->nr_child == 1 && i > 1)
			nr_clear++;
		nr_branch++;
		if (shadow_node->nr_child > 1 || i == 1) {
			/* Lock parent and break */
			shadow_node = rcuja_shadow_lookup_lock(ja->ht,
					snapshot[i - 1]);
			if (!shadow_node) {
				ret = -EAGAIN;
				goto end;
			}
			shadow_nodes[nr_shadow++] = shadow_node;

			/*
			 * Check if node has been removed between RCU
			 * lookup and lock acquisition.
			 */
			assert(snapshot_ptr[i]);
			if (ja_node_ptr(*snapshot_ptr[i])
					!= ja_node_ptr(snapshot[i])) {
				ret = -ENOENT;
				goto end;
			}

			node_flag_ptr = snapshot_ptr[i + 1];
			n = snapshot_n[i + 1];
			parent_node_flag_ptr = snapshot_ptr[i];
			parent_node_flag = snapshot[i];

			if (i > 1) {
				/*
				 * Lock parent's parent, in case we need
				 * to recompact parent.
				 */
				shadow_node = rcuja_shadow_lookup_lock(ja->ht,
						snapshot[i - 2]);
				if (!shadow_node) {
					ret = -EAGAIN;
					goto end;
				}
				shadow_nodes[nr_shadow++] = shadow_node;

				/*
				 * Check if node has been removed between RCU
				 * lookup and lock acquisition.
				 */
				assert(snapshot_ptr[i - 1]);
				if (ja_node_ptr(*snapshot_ptr[i - 1])
						!= ja_node_ptr(snapshot[i - 1])) {
					ret = -ENOENT;
					goto end;
				}
			}

			break;
		}
	}

	/*
	 * At this point, we want to delete all nodes that are about to
	 * be removed from shadow_nodes (except the last one, which is
	 * either the root or the parent of the upmost node with 1
	 * child). OK to free lock here, because RCU read lock is held,
	 * and free only performed in call_rcu.
	 */

	for (i = 0; i < nr_clear; i++) {
		ret = rcuja_shadow_clear(ja->ht,
				shadow_nodes[i]->node_flag,
				shadow_nodes[i],
				RCUJA_SHADOW_CLEAR_FREE_NODE
				| RCUJA_SHADOW_CLEAR_FREE_LOCK);
		assert(!ret);
	}

	iter_node_flag = parent_node_flag;
	/* Remove from parent */
	ret = ja_node_clear_ptr(ja,
		node_flag_ptr, 		/* Pointer to location to nullify */
		&iter_node_flag,	/* Old new parent ptr in its parent */
		shadow_nodes[nr_branch - 1],	/* of parent */
		n, nr_branch - 1);
	if (ret)
		goto end;

	dbg_printf("ja_detach_node: publish %p instead of %p\n",
		iter_node_flag, *parent_node_flag_ptr);
	/* Update address of parent ptr in its parent */
	rcu_assign_pointer(*parent_node_flag_ptr, iter_node_flag);

end:
	for (i = 0; i < nr_shadow; i++)
		rcuja_shadow_unlock(shadow_nodes[i]);
	return ret;
}

static
int ja_unchain_node(struct cds_ja *ja,
		struct cds_ja_inode_flag *parent_node_flag,
		struct cds_ja_inode_flag **node_flag_ptr,
		struct cds_ja_inode_flag *node_flag,
		struct cds_ja_node *node)
{
	struct cds_ja_shadow_node *shadow_node;
	struct cds_hlist_node *hlist_node;
	struct cds_hlist_head hlist_head;
	int ret = 0, count = 0, found = 0;

	shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
	if (!shadow_node)
		return -EAGAIN;
	if (ja_node_ptr(*node_flag_ptr) != ja_node_ptr(node_flag)) {
		ret = -EAGAIN;
		goto end;
	}
	hlist_head.next = (struct cds_hlist_node *) ja_node_ptr(node_flag);
	/*
	 * Retry if another thread removed all but one of duplicates
	 * since check (this check was performed without lock).
	 * Ensure that the node we are about to remove is still in the
	 * list (while holding lock).
	 */
	cds_hlist_for_each_rcu(hlist_node, &hlist_head) {
		if (count == 0) {
			/* FIXME: currently a work-around */
			hlist_node->prev = (struct cds_hlist_node *) node_flag_ptr;
		}
		count++;
		if (hlist_node == &node->list)
			found++;
	}
	assert(found <= 1);
	if (!found || count == 1) {
		ret = -EAGAIN;
		goto end;
	}
	cds_hlist_del_rcu(&node->list);
	/*
	 * Validate that we indeed removed the node from linked list.
	 */
	assert(ja_node_ptr(*node_flag_ptr) != (struct cds_ja_inode *) node);
end:
	rcuja_shadow_unlock(shadow_node);
	return ret;
}

/*
 * Called with RCU read lock held.
 */
int cds_ja_del(struct cds_ja *ja, uint64_t key,
		struct cds_ja_node *node)
{
	unsigned int tree_depth, i;
	struct cds_ja_inode_flag *snapshot[JA_MAX_DEPTH];
	struct cds_ja_inode_flag **snapshot_ptr[JA_MAX_DEPTH];
	uint8_t snapshot_n[JA_MAX_DEPTH];
	struct cds_ja_inode_flag *node_flag;
	struct cds_ja_inode_flag **prev_node_flag_ptr,
		**node_flag_ptr;
	int nr_snapshot;
	int ret;

	if (caa_unlikely(key > ja->key_max))
		return -EINVAL;
	tree_depth = ja->tree_depth;

retry:
	nr_snapshot = 0;
	dbg_printf("cds_ja_del attempt: key %" PRIu64 ", node %p\n",
		key, node);

	/* snapshot for level 0 is only for shadow node lookup */
	snapshot_n[0] = 0;
	snapshot_n[1] = 0;
	snapshot_ptr[nr_snapshot] = NULL;
	snapshot[nr_snapshot++] = (struct cds_ja_inode_flag *) &ja->root;
	node_flag = rcu_dereference(ja->root);
	prev_node_flag_ptr = &ja->root;
	node_flag_ptr = &ja->root;

	/* Iterate on all internal levels */
	for (i = 1; i < tree_depth; i++) {
		uint8_t iter_key;

		dbg_printf("cds_ja_del iter node_flag %p\n",
				node_flag);
		if (!ja_node_ptr(node_flag)) {
			return -ENOENT;
		}
		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
		snapshot_n[nr_snapshot + 1] = iter_key;
		snapshot_ptr[nr_snapshot] = prev_node_flag_ptr;
		snapshot[nr_snapshot++] = node_flag;
		node_flag = ja_node_get_nth(node_flag,
			&node_flag_ptr,
			iter_key);
		if (node_flag)
			prev_node_flag_ptr = node_flag_ptr;
		dbg_printf("cds_ja_del iter key lookup %u finds node_flag %p, prev_node_flag_ptr %p\n",
				(unsigned int) iter_key, node_flag,
				prev_node_flag_ptr);
	}
	/*
	 * We reached bottom of tree, try to find the node we are trying
	 * to remove. Fail if we cannot find it.
	 */
	if (!ja_node_ptr(node_flag)) {
		dbg_printf("cds_ja_del: no node found for key %" PRIu64 "\n",
				key);
		return -ENOENT;
	} else {
		struct cds_hlist_head hlist_head;
		struct cds_hlist_node *hlist_node;
		struct cds_ja_node *entry, *match = NULL;
		int count = 0;

		hlist_head.next =
			(struct cds_hlist_node *) ja_node_ptr(node_flag);
		cds_hlist_for_each_entry_rcu(entry,
				hlist_node,
				&hlist_head,
				list) {
			dbg_printf("cds_ja_del: compare %p with entry %p\n", node, entry);
			if (entry == node)
				match = entry;
			count++;
		}
		if (!match) {
			dbg_printf("cds_ja_del: no node match for node %p key %" PRIu64 "\n", node, key);
			return -ENOENT;
		}
		assert(count > 0);
		if (count == 1) {
			/*
			 * Removing last of duplicates. Last snapshot
			 * does not have a shadow node (external leafs).
			 */
			snapshot_ptr[nr_snapshot] = prev_node_flag_ptr;
			snapshot[nr_snapshot++] = node_flag;
			ret = ja_detach_node(ja, snapshot, snapshot_ptr,
					snapshot_n, nr_snapshot, key, node);
		} else {
			ret = ja_unchain_node(ja, snapshot[nr_snapshot - 1],
				node_flag_ptr, node_flag, match);
		}
	}
	/*
	 * Explanation of -ENOENT handling: caused by concurrent delete
	 * between RCU lookup and actual removal. Need to re-do the
	 * lookup and removal attempt.
	 */
	if (ret == -EAGAIN || ret == -ENOENT)
		goto retry;
	return ret;
}

struct cds_ja *_cds_ja_new(unsigned int key_bits,
		const struct rcu_flavor_struct *flavor)
{
	struct cds_ja *ja;
	int ret;
	struct cds_ja_shadow_node *root_shadow_node;

	ja = calloc(sizeof(*ja), 1);
	if (!ja)
		goto ja_error;

	switch (key_bits) {
	case 8:
	case 16:
	case 24:
	case 32:
	case 40:
	case 48:
	case 56:
		ja->key_max = (1ULL << key_bits) - 1;
		break;
	case 64:
		ja->key_max = UINT64_MAX;
		break;
	default:
		goto check_error;
	}

	/* ja->root is NULL */
	/* tree_depth 0 is for pointer to root node */
	ja->tree_depth = (key_bits >> JA_LOG2_BITS_PER_BYTE) + 1;
	assert(ja->tree_depth <= JA_MAX_DEPTH);
	ja->ht = rcuja_create_ht(flavor);
	if (!ja->ht)
		goto ht_error;

	/*
	 * Note: we should not free this node until judy array destroy.
	 */
	root_shadow_node = rcuja_shadow_set(ja->ht,
			(struct cds_ja_inode_flag *) &ja->root,
			NULL, ja, 0);
	if (!root_shadow_node) {
		ret = -ENOMEM;
		goto ht_node_error;
	}

	return ja;

ht_node_error:
	ret = rcuja_delete_ht(ja->ht);
	assert(!ret);
ht_error:
check_error:
	free(ja);
ja_error:
	return NULL;
}

/*
 * Called from RCU read-side CS.
 */
__attribute__((visibility("protected")))
void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
		struct cds_ja_inode_flag *node_flag,
		void (*free_node_cb)(struct rcu_head *head))
{
	const struct rcu_flavor_struct *flavor;
	unsigned int type_index;
	struct cds_ja_inode *node;
	const struct cds_ja_type *type;

	flavor = cds_lfht_rcu_flavor(shadow_node->ja->ht);
	node = ja_node_ptr(node_flag);
	assert(node != NULL);
	type_index = ja_node_type(node_flag);
	type = &ja_types[type_index];

	switch (type->type_class) {
	case RCU_JA_LINEAR:
	{
		uint8_t nr_child =
			ja_linear_node_get_nr_child(type, node);
		unsigned int i;

		for (i = 0; i < nr_child; i++) {
			struct cds_ja_inode_flag *iter;
			struct cds_hlist_head head;
			struct cds_ja_node *entry;
			struct cds_hlist_node *pos, *tmp;
			uint8_t v;

			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
			if (!iter)
				continue;
			head.next = (struct cds_hlist_node *) iter;
			cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
				flavor->update_call_rcu(&entry->head, free_node_cb);
			}
		}
		break;
	}
	case RCU_JA_POOL:
	{
		unsigned int pool_nr;

		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
			struct cds_ja_inode *pool =
				ja_pool_node_get_ith_pool(type, node, pool_nr);
			uint8_t nr_child =
				ja_linear_node_get_nr_child(type, pool);
			unsigned int j;

			for (j = 0; j < nr_child; j++) {
				struct cds_ja_inode_flag *iter;
				struct cds_hlist_head head;
				struct cds_ja_node *entry;
				struct cds_hlist_node *pos, *tmp;
				uint8_t v;

				ja_linear_node_get_ith_pos(type, pool, j, &v, &iter);
				if (!iter)
					continue;
				head.next = (struct cds_hlist_node *) iter;
				cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
					flavor->update_call_rcu(&entry->head, free_node_cb);
				}
			}
		}
		break;
	}
	case RCU_JA_NULL:
		break;
	case RCU_JA_PIGEON:
	{
		unsigned int i;

		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
			struct cds_ja_inode_flag *iter;
			struct cds_hlist_head head;
			struct cds_ja_node *entry;
			struct cds_hlist_node *pos, *tmp;

			iter = ja_pigeon_node_get_ith_pos(type, node, i);
			if (!iter)
				continue;
			head.next = (struct cds_hlist_node *) iter;
			cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
				flavor->update_call_rcu(&entry->head, free_node_cb);
			}
		}
		break;
	}
	default:
		assert(0);
	}
}

static
void print_debug_fallback_distribution(void)
{
	int i;

	fprintf(stderr, "Fallback node distribution:\n");
	for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
		if (!node_fallback_count_distribution[i])
			continue;
		fprintf(stderr, "	%3u: %4lu\n",
			i, node_fallback_count_distribution[i]);
	}
}

/*
 * There should be no more concurrent add to the judy array while it is
 * being destroyed (ensured by the caller).
 */
int cds_ja_destroy(struct cds_ja *ja,
		void (*free_node_cb)(struct rcu_head *head))
{
	const struct rcu_flavor_struct *flavor;
	int ret;

	flavor = cds_lfht_rcu_flavor(ja->ht);
	rcuja_shadow_prune(ja->ht,
		RCUJA_SHADOW_CLEAR_FREE_NODE | RCUJA_SHADOW_CLEAR_FREE_LOCK,
		free_node_cb);
	flavor->thread_offline();
	ret = rcuja_delete_ht(ja->ht);
	if (ret)
		return ret;
	flavor->thread_online();
	if (uatomic_read(&ja->nr_fallback))
		fprintf(stderr,
			"[warning] RCU Judy Array used %lu fallback node(s)\n",
			uatomic_read(&ja->nr_fallback));
	fprintf(stderr, "Nodes allocated: %lu, Nodes freed: %lu. Fallback ratio: %g\n",
		uatomic_read(&nr_nodes_allocated),
		uatomic_read(&nr_nodes_freed),
		(double) uatomic_read(&ja->nr_fallback) / (double) uatomic_read(&nr_nodes_allocated));
	print_debug_fallback_distribution();
	free(ja);
	return 0;
}