Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 7251 insertions, 0 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
new file mode 100644
index 000000000..4976522e3
--- /dev/null
+++ b/lib/maple_tree.c
@@ -0,0 +1,7251 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Maple Tree implementation
+ * Copyright (c) 2018-2022 Oracle Corporation
+ * Authors: Liam R. Howlett <Liam.Howlett@oracle.com>
+ *	    Matthew Wilcox <willy@infradead.org>
+ */
+
+/*
+ * DOC: Interesting implementation details of the Maple Tree
+ *
+ * Each node type has a number of slots for entries and a number of slots for
+ * pivots.  In the case of dense nodes, the pivots are implied by the position
+ * and are simply the slot index + the minimum of the node.
+ *
+ * In regular B-Tree terms, pivots are called keys.  The term pivot is used to
+ * indicate that the tree is specifying ranges,  Pivots may appear in the
+ * subtree with an entry attached to the value where as keys are unique to a
+ * specific position of a B-tree.  Pivot values are inclusive of the slot with
+ * the same index.
+ *
+ *
+ * The following illustrates the layout of a range64 nodes slots and pivots.
+ *
+ *
+ *  Slots -> | 0 | 1 | 2 | ... | 12 | 13 | 14 | 15 |
+ *           ┬   ┬   ┬   ┬     ┬    ┬    ┬    ┬    ┬
+ *           │   │   │   │     │    │    │    │    └─ Implied maximum
+ *           │   │   │   │     │    │    │    └─ Pivot 14
+ *           │   │   │   │     │    │    └─ Pivot 13
+ *           │   │   │   │     │    └─ Pivot 12
+ *           │   │   │   │     └─ Pivot 11
+ *           │   │   │   └─ Pivot 2
+ *           │   │   └─ Pivot 1
+ *           │   └─ Pivot 0
+ *           └─  Implied minimum
+ *
+ * Slot contents:
+ *  Internal (non-leaf) nodes contain pointers to other nodes.
+ *  Leaf nodes contain entries.
+ *
+ * The location of interest is often referred to as an offset.  All offsets have
+ * a slot, but the last offset has an implied pivot from the node above (or
+ * UINT_MAX for the root node.
+ *
+ * Ranges complicate certain write activities.  When modifying any of
+ * the B-tree variants, it is known that one entry will either be added or
+ * deleted.  When modifying the Maple Tree, one store operation may overwrite
+ * the entire data set, or one half of the tree, or the middle half of the tree.
+ *
+ */
+
+
+#include <linux/maple_tree.h>
+#include <linux/xarray.h>
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/limits.h>
+#include <asm/barrier.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/maple_tree.h>
+
+#define MA_ROOT_PARENT 1
+
+/*
+ * Maple state flags
+ * * MA_STATE_BULK		- Bulk insert mode
+ * * MA_STATE_REBALANCE		- Indicate a rebalance during bulk insert
+ * * MA_STATE_PREALLOC		- Preallocated nodes, WARN_ON allocation
+ */
+#define MA_STATE_BULK		1
+#define MA_STATE_REBALANCE	2
+#define MA_STATE_PREALLOC	4
+
+#define ma_parent_ptr(x) ((struct maple_pnode *)(x))
+#define ma_mnode_ptr(x) ((struct maple_node *)(x))
+#define ma_enode_ptr(x) ((struct maple_enode *)(x))
+static struct kmem_cache *maple_node_cache;
+
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+static const unsigned long mt_max[] = {
+	[maple_dense]		= MAPLE_NODE_SLOTS,
+	[maple_leaf_64]		= ULONG_MAX,
+	[maple_range_64]	= ULONG_MAX,
+	[maple_arange_64]	= ULONG_MAX,
+};
+#define mt_node_max(x) mt_max[mte_node_type(x)]
+#endif
+
+static const unsigned char mt_slots[] = {
+	[maple_dense]		= MAPLE_NODE_SLOTS,
+	[maple_leaf_64]		= MAPLE_RANGE64_SLOTS,
+	[maple_range_64]	= MAPLE_RANGE64_SLOTS,
+	[maple_arange_64]	= MAPLE_ARANGE64_SLOTS,
+};
+#define mt_slot_count(x) mt_slots[mte_node_type(x)]
+
+static const unsigned char mt_pivots[] = {
+	[maple_dense]		= 0,
+	[maple_leaf_64]		= MAPLE_RANGE64_SLOTS - 1,
+	[maple_range_64]	= MAPLE_RANGE64_SLOTS - 1,
+	[maple_arange_64]	= MAPLE_ARANGE64_SLOTS - 1,
+};
+#define mt_pivot_count(x) mt_pivots[mte_node_type(x)]
+
+static const unsigned char mt_min_slots[] = {
+	[maple_dense]		= MAPLE_NODE_SLOTS / 2,
+	[maple_leaf_64]		= (MAPLE_RANGE64_SLOTS / 2) - 2,
+	[maple_range_64]	= (MAPLE_RANGE64_SLOTS / 2) - 2,
+	[maple_arange_64]	= (MAPLE_ARANGE64_SLOTS / 2) - 1,
+};
+#define mt_min_slot_count(x) mt_min_slots[mte_node_type(x)]
+
+#define MAPLE_BIG_NODE_SLOTS	(MAPLE_RANGE64_SLOTS * 2 + 2)
+#define MAPLE_BIG_NODE_GAPS	(MAPLE_ARANGE64_SLOTS * 2 + 1)
+
+struct maple_big_node {
+	struct maple_pnode *parent;
+	unsigned long pivot[MAPLE_BIG_NODE_SLOTS - 1];
+	union {
+		struct maple_enode *slot[MAPLE_BIG_NODE_SLOTS];
+		struct {
+			unsigned long padding[MAPLE_BIG_NODE_GAPS];
+			unsigned long gap[MAPLE_BIG_NODE_GAPS];
+		};
+	};
+	unsigned char b_end;
+	enum maple_type type;
+};
+
+/*
+ * The maple_subtree_state is used to build a tree to replace a segment of an
+ * existing tree in a more atomic way.  Any walkers of the older tree will hit a
+ * dead node and restart on updates.
+ */
+struct maple_subtree_state {
+	struct ma_state *orig_l;	/* Original left side of subtree */
+	struct ma_state *orig_r;	/* Original right side of subtree */
+	struct ma_state *l;		/* New left side of subtree */
+	struct ma_state *m;		/* New middle of subtree (rare) */
+	struct ma_state *r;		/* New right side of subtree */
+	struct ma_topiary *free;	/* nodes to be freed */
+	struct ma_topiary *destroy;	/* Nodes to be destroyed (walked and freed) */
+	struct maple_big_node *bn;
+};
+
+/* Functions */
+static inline struct maple_node *mt_alloc_one(gfp_t gfp)
+{
+	return kmem_cache_alloc(maple_node_cache, gfp);
+}
+
+static inline int mt_alloc_bulk(gfp_t gfp, size_t size, void **nodes)
+{
+	return kmem_cache_alloc_bulk(maple_node_cache, gfp, size, nodes);
+}
+
+static inline void mt_free_bulk(size_t size, void __rcu **nodes)
+{
+	kmem_cache_free_bulk(maple_node_cache, size, (void **)nodes);
+}
+
+static void mt_free_rcu(struct rcu_head *head)
+{
+	struct maple_node *node = container_of(head, struct maple_node, rcu);
+
+	kmem_cache_free(maple_node_cache, node);
+}
+
+/*
+ * ma_free_rcu() - Use rcu callback to free a maple node
+ * @node: The node to free
+ *
+ * The maple tree uses the parent pointer to indicate this node is no longer in
+ * use and will be freed.
+ */
+static void ma_free_rcu(struct maple_node *node)
+{
+	WARN_ON(node->parent != ma_parent_ptr(node));
+	call_rcu(&node->rcu, mt_free_rcu);
+}
+
+
+static void mas_set_height(struct ma_state *mas)
+{
+	unsigned int new_flags = mas->tree->ma_flags;
+
+	new_flags &= ~MT_FLAGS_HEIGHT_MASK;
+	BUG_ON(mas->depth > MAPLE_HEIGHT_MAX);
+	new_flags |= mas->depth << MT_FLAGS_HEIGHT_OFFSET;
+	mas->tree->ma_flags = new_flags;
+}
+
+static unsigned int mas_mt_height(struct ma_state *mas)
+{
+	return mt_height(mas->tree);
+}
+
+static inline enum maple_type mte_node_type(const struct maple_enode *entry)
+{
+	return ((unsigned long)entry >> MAPLE_NODE_TYPE_SHIFT) &
+		MAPLE_NODE_TYPE_MASK;
+}
+
+static inline bool ma_is_dense(const enum maple_type type)
+{
+	return type < maple_leaf_64;
+}
+
+static inline bool ma_is_leaf(const enum maple_type type)
+{
+	return type < maple_range_64;
+}
+
+static inline bool mte_is_leaf(const struct maple_enode *entry)
+{
+	return ma_is_leaf(mte_node_type(entry));
+}
+
+/*
+ * We also reserve values with the bottom two bits set to '10' which are
+ * below 4096
+ */
+static inline bool mt_is_reserved(const void *entry)
+{
+	return ((unsigned long)entry < MAPLE_RESERVED_RANGE) &&
+		xa_is_internal(entry);
+}
+
+static inline void mas_set_err(struct ma_state *mas, long err)
+{
+	mas->node = MA_ERROR(err);
+}
+
+static inline bool mas_is_ptr(struct ma_state *mas)
+{
+	return mas->node == MAS_ROOT;
+}
+
+static inline bool mas_is_start(struct ma_state *mas)
+{
+	return mas->node == MAS_START;
+}
+
+bool mas_is_err(struct ma_state *mas)
+{
+	return xa_is_err(mas->node);
+}
+
+static inline bool mas_searchable(struct ma_state *mas)
+{
+	if (mas_is_none(mas))
+		return false;
+
+	if (mas_is_ptr(mas))
+		return false;
+
+	return true;
+}
+
+static inline struct maple_node *mte_to_node(const struct maple_enode *entry)
+{
+	return (struct maple_node *)((unsigned long)entry & ~MAPLE_NODE_MASK);
+}
+
+/*
+ * mte_to_mat() - Convert a maple encoded node to a maple topiary node.
+ * @entry: The maple encoded node
+ *
+ * Return: a maple topiary pointer
+ */
+static inline struct maple_topiary *mte_to_mat(const struct maple_enode *entry)
+{
+	return (struct maple_topiary *)
+		((unsigned long)entry & ~MAPLE_NODE_MASK);
+}
+
+/*
+ * mas_mn() - Get the maple state node.
+ * @mas: The maple state
+ *
+ * Return: the maple node (not encoded - bare pointer).
+ */
+static inline struct maple_node *mas_mn(const struct ma_state *mas)
+{
+	return mte_to_node(mas->node);
+}
+
+/*
+ * mte_set_node_dead() - Set a maple encoded node as dead.
+ * @mn: The maple encoded node.
+ */
+static inline void mte_set_node_dead(struct maple_enode *mn)
+{
+	mte_to_node(mn)->parent = ma_parent_ptr(mte_to_node(mn));
+	smp_wmb(); /* Needed for RCU */
+}
+
+/* Bit 1 indicates the root is a node */
+#define MAPLE_ROOT_NODE			0x02
+/* maple_type stored bit 3-6 */
+#define MAPLE_ENODE_TYPE_SHIFT		0x03
+/* Bit 2 means a NULL somewhere below */
+#define MAPLE_ENODE_NULL		0x04
+
+static inline struct maple_enode *mt_mk_node(const struct maple_node *node,
+					     enum maple_type type)
+{
+	return (void *)((unsigned long)node |
+			(type << MAPLE_ENODE_TYPE_SHIFT) | MAPLE_ENODE_NULL);
+}
+
+static inline void *mte_mk_root(const struct maple_enode *node)
+{
+	return (void *)((unsigned long)node | MAPLE_ROOT_NODE);
+}
+
+static inline void *mte_safe_root(const struct maple_enode *node)
+{
+	return (void *)((unsigned long)node & ~MAPLE_ROOT_NODE);
+}
+
+static inline void mte_set_full(const struct maple_enode *node)
+{
+	node = (void *)((unsigned long)node & ~MAPLE_ENODE_NULL);
+}
+
+static inline void mte_clear_full(const struct maple_enode *node)
+{
+	node = (void *)((unsigned long)node | MAPLE_ENODE_NULL);
+}
+
+static inline bool ma_is_root(struct maple_node *node)
+{
+	return ((unsigned long)node->parent & MA_ROOT_PARENT);
+}
+
+static inline bool mte_is_root(const struct maple_enode *node)
+{
+	return ma_is_root(mte_to_node(node));
+}
+
+static inline bool mas_is_root_limits(const struct ma_state *mas)
+{
+	return !mas->min && mas->max == ULONG_MAX;
+}
+
+static inline bool mt_is_alloc(struct maple_tree *mt)
+{
+	return (mt->ma_flags & MT_FLAGS_ALLOC_RANGE);
+}
+
+/*
+ * The Parent Pointer
+ * Excluding root, the parent pointer is 256B aligned like all other tree nodes.
+ * When storing a 32 or 64 bit values, the offset can fit into 5 bits.  The 16
+ * bit values need an extra bit to store the offset.  This extra bit comes from
+ * a reuse of the last bit in the node type.  This is possible by using bit 1 to
+ * indicate if bit 2 is part of the type or the slot.
+ *
+ * Note types:
+ *  0x??1 = Root
+ *  0x?00 = 16 bit nodes
+ *  0x010 = 32 bit nodes
+ *  0x110 = 64 bit nodes
+ *
+ * Slot size and alignment
+ *  0b??1 : Root
+ *  0b?00 : 16 bit values, type in 0-1, slot in 2-7
+ *  0b010 : 32 bit values, type in 0-2, slot in 3-7
+ *  0b110 : 64 bit values, type in 0-2, slot in 3-7
+ */
+
+#define MAPLE_PARENT_ROOT		0x01
+
+#define MAPLE_PARENT_SLOT_SHIFT		0x03
+#define MAPLE_PARENT_SLOT_MASK		0xF8
+
+#define MAPLE_PARENT_16B_SLOT_SHIFT	0x02
+#define MAPLE_PARENT_16B_SLOT_MASK	0xFC
+
+#define MAPLE_PARENT_RANGE64		0x06
+#define MAPLE_PARENT_RANGE32		0x04
+#define MAPLE_PARENT_NOT_RANGE16	0x02
+
+/*
+ * mte_parent_shift() - Get the parent shift for the slot storage.
+ * @parent: The parent pointer cast as an unsigned long
+ * Return: The shift into that pointer to the star to of the slot
+ */
+static inline unsigned long mte_parent_shift(unsigned long parent)
+{
+	/* Note bit 1 == 0 means 16B */
+	if (likely(parent & MAPLE_PARENT_NOT_RANGE16))
+		return MAPLE_PARENT_SLOT_SHIFT;
+
+	return MAPLE_PARENT_16B_SLOT_SHIFT;
+}
+
+/*
+ * mte_parent_slot_mask() - Get the slot mask for the parent.
+ * @parent: The parent pointer cast as an unsigned long.
+ * Return: The slot mask for that parent.
+ */
+static inline unsigned long mte_parent_slot_mask(unsigned long parent)
+{
+	/* Note bit 1 == 0 means 16B */
+	if (likely(parent & MAPLE_PARENT_NOT_RANGE16))
+		return MAPLE_PARENT_SLOT_MASK;
+
+	return MAPLE_PARENT_16B_SLOT_MASK;
+}
+
+/*
+ * mas_parent_enum() - Return the maple_type of the parent from the stored
+ * parent type.
+ * @mas: The maple state
+ * @node: The maple_enode to extract the parent's enum
+ * Return: The node->parent maple_type
+ */
+static inline
+enum maple_type mte_parent_enum(struct maple_enode *p_enode,
+				struct maple_tree *mt)
+{
+	unsigned long p_type;
+
+	p_type = (unsigned long)p_enode;
+	if (p_type & MAPLE_PARENT_ROOT)
+		return 0; /* Validated in the caller. */
+
+	p_type &= MAPLE_NODE_MASK;
+	p_type = p_type & ~(MAPLE_PARENT_ROOT | mte_parent_slot_mask(p_type));
+
+	switch (p_type) {
+	case MAPLE_PARENT_RANGE64: /* or MAPLE_PARENT_ARANGE64 */
+		if (mt_is_alloc(mt))
+			return maple_arange_64;
+		return maple_range_64;
+	}
+
+	return 0;
+}
+
+static inline
+enum maple_type mas_parent_enum(struct ma_state *mas, struct maple_enode *enode)
+{
+	return mte_parent_enum(ma_enode_ptr(mte_to_node(enode)->parent), mas->tree);
+}
+
+/*
+ * mte_set_parent() - Set the parent node and encode the slot
+ * @enode: The encoded maple node.
+ * @parent: The encoded maple node that is the parent of @enode.
+ * @slot: The slot that @enode resides in @parent.
+ *
+ * Slot number is encoded in the enode->parent bit 3-6 or 2-6, depending on the
+ * parent type.
+ */
+static inline
+void mte_set_parent(struct maple_enode *enode, const struct maple_enode *parent,
+		    unsigned char slot)
+{
+	unsigned long val = (unsigned long) parent;
+	unsigned long shift;
+	unsigned long type;
+	enum maple_type p_type = mte_node_type(parent);
+
+	BUG_ON(p_type == maple_dense);
+	BUG_ON(p_type == maple_leaf_64);
+
+	switch (p_type) {
+	case maple_range_64:
+	case maple_arange_64:
+		shift = MAPLE_PARENT_SLOT_SHIFT;
+		type = MAPLE_PARENT_RANGE64;
+		break;
+	default:
+	case maple_dense:
+	case maple_leaf_64:
+		shift = type = 0;
+		break;
+	}
+
+	val &= ~MAPLE_NODE_MASK; /* Clear all node metadata in parent */
+	val |= (slot << shift) | type;
+	mte_to_node(enode)->parent = ma_parent_ptr(val);
+}
+
+/*
+ * mte_parent_slot() - get the parent slot of @enode.
+ * @enode: The encoded maple node.
+ *
+ * Return: The slot in the parent node where @enode resides.
+ */
+static inline unsigned int mte_parent_slot(const struct maple_enode *enode)
+{
+	unsigned long val = (unsigned long) mte_to_node(enode)->parent;
+
+	/* Root. */
+	if (val & 1)
+		return 0;
+
+	/*
+	 * Okay to use MAPLE_PARENT_16B_SLOT_MASK as the last bit will be lost
+	 * by shift if the parent shift is MAPLE_PARENT_SLOT_SHIFT
+	 */
+	return (val & MAPLE_PARENT_16B_SLOT_MASK) >> mte_parent_shift(val);
+}
+
+/*
+ * mte_parent() - Get the parent of @node.
+ * @node: The encoded maple node.
+ *
+ * Return: The parent maple node.
+ */
+static inline struct maple_node *mte_parent(const struct maple_enode *enode)
+{
+	return (void *)((unsigned long)
+			(mte_to_node(enode)->parent) & ~MAPLE_NODE_MASK);
+}
+
+/*
+ * ma_dead_node() - check if the @enode is dead.
+ * @enode: The encoded maple node
+ *
+ * Return: true if dead, false otherwise.
+ */
+static inline bool ma_dead_node(const struct maple_node *node)
+{
+	struct maple_node *parent;
+
+	/* Do not reorder reads from the node prior to the parent check */
+	smp_rmb();
+	parent = (void *)((unsigned long) node->parent & ~MAPLE_NODE_MASK);
+	return (parent == node);
+}
+
+/*
+ * mte_dead_node() - check if the @enode is dead.
+ * @enode: The encoded maple node
+ *
+ * Return: true if dead, false otherwise.
+ */
+static inline bool mte_dead_node(const struct maple_enode *enode)
+{
+	struct maple_node *parent, *node;
+
+	node = mte_to_node(enode);
+	/* Do not reorder reads from the node prior to the parent check */
+	smp_rmb();
+	parent = mte_parent(enode);
+	return (parent == node);
+}
+
+/*
+ * mas_allocated() - Get the number of nodes allocated in a maple state.
+ * @mas: The maple state
+ *
+ * The ma_state alloc member is overloaded to hold a pointer to the first
+ * allocated node or to the number of requested nodes to allocate.  If bit 0 is
+ * set, then the alloc contains the number of requested nodes.  If there is an
+ * allocated node, then the total allocated nodes is in that node.
+ *
+ * Return: The total number of nodes allocated
+ */
+static inline unsigned long mas_allocated(const struct ma_state *mas)
+{
+	if (!mas->alloc || ((unsigned long)mas->alloc & 0x1))
+		return 0;
+
+	return mas->alloc->total;
+}
+
+/*
+ * mas_set_alloc_req() - Set the requested number of allocations.
+ * @mas: the maple state
+ * @count: the number of allocations.
+ *
+ * The requested number of allocations is either in the first allocated node,
+ * located in @mas->alloc->request_count, or directly in @mas->alloc if there is
+ * no allocated node.  Set the request either in the node or do the necessary
+ * encoding to store in @mas->alloc directly.
+ */
+static inline void mas_set_alloc_req(struct ma_state *mas, unsigned long count)
+{
+	if (!mas->alloc || ((unsigned long)mas->alloc & 0x1)) {
+		if (!count)
+			mas->alloc = NULL;
+		else
+			mas->alloc = (struct maple_alloc *)(((count) << 1U) | 1U);
+		return;
+	}
+
+	mas->alloc->request_count = count;
+}
+
+/*
+ * mas_alloc_req() - get the requested number of allocations.
+ * @mas: The maple state
+ *
+ * The alloc count is either stored directly in @mas, or in
+ * @mas->alloc->request_count if there is at least one node allocated.  Decode
+ * the request count if it's stored directly in @mas->alloc.
+ *
+ * Return: The allocation request count.
+ */
+static inline unsigned int mas_alloc_req(const struct ma_state *mas)
+{
+	if ((unsigned long)mas->alloc & 0x1)
+		return (unsigned long)(mas->alloc) >> 1;
+	else if (mas->alloc)
+		return mas->alloc->request_count;
+	return 0;
+}
+
+/*
+ * ma_pivots() - Get a pointer to the maple node pivots.
+ * @node - the maple node
+ * @type - the node type
+ *
+ * In the event of a dead node, this array may be %NULL
+ *
+ * Return: A pointer to the maple node pivots
+ */
+static inline unsigned long *ma_pivots(struct maple_node *node,
+					   enum maple_type type)
+{
+	switch (type) {
+	case maple_arange_64:
+		return node->ma64.pivot;
+	case maple_range_64:
+	case maple_leaf_64:
+		return node->mr64.pivot;
+	case maple_dense:
+		return NULL;
+	}
+	return NULL;
+}
+
+/*
+ * ma_gaps() - Get a pointer to the maple node gaps.
+ * @node - the maple node
+ * @type - the node type
+ *
+ * Return: A pointer to the maple node gaps
+ */
+static inline unsigned long *ma_gaps(struct maple_node *node,
+				     enum maple_type type)
+{
+	switch (type) {
+	case maple_arange_64:
+		return node->ma64.gap;
+	case maple_range_64:
+	case maple_leaf_64:
+	case maple_dense:
+		return NULL;
+	}
+	return NULL;
+}
+
+/*
+ * mte_pivot() - Get the pivot at @piv of the maple encoded node.
+ * @mn: The maple encoded node.
+ * @piv: The pivot.
+ *
+ * Return: the pivot at @piv of @mn.
+ */
+static inline unsigned long mte_pivot(const struct maple_enode *mn,
+				 unsigned char piv)
+{
+	struct maple_node *node = mte_to_node(mn);
+	enum maple_type type = mte_node_type(mn);
+
+	if (piv >= mt_pivots[type]) {
+		WARN_ON(1);
+		return 0;
+	}
+	switch (type) {
+	case maple_arange_64:
+		return node->ma64.pivot[piv];
+	case maple_range_64:
+	case maple_leaf_64:
+		return node->mr64.pivot[piv];
+	case maple_dense:
+		return 0;
+	}
+	return 0;
+}
+
+/*
+ * mas_safe_pivot() - get the pivot at @piv or mas->max.
+ * @mas: The maple state
+ * @pivots: The pointer to the maple node pivots
+ * @piv: The pivot to fetch
+ * @type: The maple node type
+ *
+ * Return: The pivot at @piv within the limit of the @pivots array, @mas->max
+ * otherwise.
+ */
+static inline unsigned long
+mas_safe_pivot(const struct ma_state *mas, unsigned long *pivots,
+	       unsigned char piv, enum maple_type type)
+{
+	if (piv >= mt_pivots[type])
+		return mas->max;
+
+	return pivots[piv];
+}
+
+/*
+ * mas_safe_min() - Return the minimum for a given offset.
+ * @mas: The maple state
+ * @pivots: The pointer to the maple node pivots
+ * @offset: The offset into the pivot array
+ *
+ * Return: The minimum range value that is contained in @offset.
+ */
+static inline unsigned long
+mas_safe_min(struct ma_state *mas, unsigned long *pivots, unsigned char offset)
+{
+	if (likely(offset))
+		return pivots[offset - 1] + 1;
+
+	return mas->min;
+}
+
+/*
+ * mas_logical_pivot() - Get the logical pivot of a given offset.
+ * @mas: The maple state
+ * @pivots: The pointer to the maple node pivots
+ * @offset: The offset into the pivot array
+ * @type: The maple node type
+ *
+ * When there is no value at a pivot (beyond the end of the data), then the
+ * pivot is actually @mas->max.
+ *
+ * Return: the logical pivot of a given @offset.
+ */
+static inline unsigned long
+mas_logical_pivot(struct ma_state *mas, unsigned long *pivots,
+		  unsigned char offset, enum maple_type type)
+{
+	unsigned long lpiv = mas_safe_pivot(mas, pivots, offset, type);
+
+	if (likely(lpiv))
+		return lpiv;
+
+	if (likely(offset))
+		return mas->max;
+
+	return lpiv;
+}
+
+/*
+ * mte_set_pivot() - Set a pivot to a value in an encoded maple node.
+ * @mn: The encoded maple node
+ * @piv: The pivot offset
+ * @val: The value of the pivot
+ */
+static inline void mte_set_pivot(struct maple_enode *mn, unsigned char piv,
+				unsigned long val)
+{
+	struct maple_node *node = mte_to_node(mn);
+	enum maple_type type = mte_node_type(mn);
+
+	BUG_ON(piv >= mt_pivots[type]);
+	switch (type) {
+	default:
+	case maple_range_64:
+	case maple_leaf_64:
+		node->mr64.pivot[piv] = val;
+		break;
+	case maple_arange_64:
+		node->ma64.pivot[piv] = val;
+		break;
+	case maple_dense:
+		break;
+	}
+
+}
+
+/*
+ * ma_slots() - Get a pointer to the maple node slots.
+ * @mn: The maple node
+ * @mt: The maple node type
+ *
+ * Return: A pointer to the maple node slots
+ */
+static inline void __rcu **ma_slots(struct maple_node *mn, enum maple_type mt)
+{
+	switch (mt) {
+	default:
+	case maple_arange_64:
+		return mn->ma64.slot;
+	case maple_range_64:
+	case maple_leaf_64:
+		return mn->mr64.slot;
+	case maple_dense:
+		return mn->slot;
+	}
+}
+
+static inline bool mt_locked(const struct maple_tree *mt)
+{
+	return mt_external_lock(mt) ? mt_lock_is_held(mt) :
+		lockdep_is_held(&mt->ma_lock);
+}
+
+static inline void *mt_slot(const struct maple_tree *mt,
+		void __rcu **slots, unsigned char offset)
+{
+	return rcu_dereference_check(slots[offset], mt_locked(mt));
+}
+
+static inline void *mt_slot_locked(struct maple_tree *mt, void __rcu **slots,
+				   unsigned char offset)
+{
+	return rcu_dereference_protected(slots[offset], mt_locked(mt));
+}
+/*
+ * mas_slot_locked() - Get the slot value when holding the maple tree lock.
+ * @mas: The maple state
+ * @slots: The pointer to the slots
+ * @offset: The offset into the slots array to fetch
+ *
+ * Return: The entry stored in @slots at the @offset.
+ */
+static inline void *mas_slot_locked(struct ma_state *mas, void __rcu **slots,
+				       unsigned char offset)
+{
+	return mt_slot_locked(mas->tree, slots, offset);
+}
+
+/*
+ * mas_slot() - Get the slot value when not holding the maple tree lock.
+ * @mas: The maple state
+ * @slots: The pointer to the slots
+ * @offset: The offset into the slots array to fetch
+ *
+ * Return: The entry stored in @slots at the @offset
+ */
+static inline void *mas_slot(struct ma_state *mas, void __rcu **slots,
+			     unsigned char offset)
+{
+	return mt_slot(mas->tree, slots, offset);
+}
+
+/*
+ * mas_root() - Get the maple tree root.
+ * @mas: The maple state.
+ *
+ * Return: The pointer to the root of the tree
+ */
+static inline void *mas_root(struct ma_state *mas)
+{
+	return rcu_dereference_check(mas->tree->ma_root, mt_locked(mas->tree));
+}
+
+static inline void *mt_root_locked(struct maple_tree *mt)
+{
+	return rcu_dereference_protected(mt->ma_root, mt_locked(mt));
+}
+
+/*
+ * mas_root_locked() - Get the maple tree root when holding the maple tree lock.
+ * @mas: The maple state.
+ *
+ * Return: The pointer to the root of the tree
+ */
+static inline void *mas_root_locked(struct ma_state *mas)
+{
+	return mt_root_locked(mas->tree);
+}
+
+static inline struct maple_metadata *ma_meta(struct maple_node *mn,
+					     enum maple_type mt)
+{
+	switch (mt) {
+	case maple_arange_64:
+		return &mn->ma64.meta;
+	default:
+		return &mn->mr64.meta;
+	}
+}
+
+/*
+ * ma_set_meta() - Set the metadata information of a node.
+ * @mn: The maple node
+ * @mt: The maple node type
+ * @offset: The offset of the highest sub-gap in this node.
+ * @end: The end of the data in this node.
+ */
+static inline void ma_set_meta(struct maple_node *mn, enum maple_type mt,
+			       unsigned char offset, unsigned char end)
+{
+	struct maple_metadata *meta = ma_meta(mn, mt);
+
+	meta->gap = offset;
+	meta->end = end;
+}
+
+/*
+ * mt_clear_meta() - clear the metadata information of a node, if it exists
+ * @mt: The maple tree
+ * @mn: The maple node
+ * @type: The maple node type
+ * @offset: The offset of the highest sub-gap in this node.
+ * @end: The end of the data in this node.
+ */
+static inline void mt_clear_meta(struct maple_tree *mt, struct maple_node *mn,
+				  enum maple_type type)
+{
+	struct maple_metadata *meta;
+	unsigned long *pivots;
+	void __rcu **slots;
+	void *next;
+
+	switch (type) {
+	case maple_range_64:
+		pivots = mn->mr64.pivot;
+		if (unlikely(pivots[MAPLE_RANGE64_SLOTS - 2])) {
+			slots = mn->mr64.slot;
+			next = mt_slot_locked(mt, slots,
+					      MAPLE_RANGE64_SLOTS - 1);
+			if (unlikely((mte_to_node(next) &&
+				      mte_node_type(next))))
+				return; /* no metadata, could be node */
+		}
+		fallthrough;
+	case maple_arange_64:
+		meta = ma_meta(mn, type);
+		break;
+	default:
+		return;
+	}
+
+	meta->gap = 0;
+	meta->end = 0;
+}
+
+/*
+ * ma_meta_end() - Get the data end of a node from the metadata
+ * @mn: The maple node
+ * @mt: The maple node type
+ */
+static inline unsigned char ma_meta_end(struct maple_node *mn,
+					enum maple_type mt)
+{
+	struct maple_metadata *meta = ma_meta(mn, mt);
+
+	return meta->end;
+}
+
+/*
+ * ma_meta_gap() - Get the largest gap location of a node from the metadata
+ * @mn: The maple node
+ * @mt: The maple node type
+ */
+static inline unsigned char ma_meta_gap(struct maple_node *mn,
+					enum maple_type mt)
+{
+	BUG_ON(mt != maple_arange_64);
+
+	return mn->ma64.meta.gap;
+}
+
+/*
+ * ma_set_meta_gap() - Set the largest gap location in a nodes metadata
+ * @mn: The maple node
+ * @mn: The maple node type
+ * @offset: The location of the largest gap.
+ */
+static inline void ma_set_meta_gap(struct maple_node *mn, enum maple_type mt,
+				   unsigned char offset)
+{
+
+	struct maple_metadata *meta = ma_meta(mn, mt);
+
+	meta->gap = offset;
+}
+
+/*
+ * mat_add() - Add a @dead_enode to the ma_topiary of a list of dead nodes.
+ * @mat - the ma_topiary, a linked list of dead nodes.
+ * @dead_enode - the node to be marked as dead and added to the tail of the list
+ *
+ * Add the @dead_enode to the linked list in @mat.
+ */
+static inline void mat_add(struct ma_topiary *mat,
+			   struct maple_enode *dead_enode)
+{
+	mte_set_node_dead(dead_enode);
+	mte_to_mat(dead_enode)->next = NULL;
+	if (!mat->tail) {
+		mat->tail = mat->head = dead_enode;
+		return;
+	}
+
+	mte_to_mat(mat->tail)->next = dead_enode;
+	mat->tail = dead_enode;
+}
+
+static void mte_destroy_walk(struct maple_enode *, struct maple_tree *);
+static inline void mas_free(struct ma_state *mas, struct maple_enode *used);
+
+/*
+ * mas_mat_free() - Free all nodes in a dead list.
+ * @mas - the maple state
+ * @mat - the ma_topiary linked list of dead nodes to free.
+ *
+ * Free walk a dead list.
+ */
+static void mas_mat_free(struct ma_state *mas, struct ma_topiary *mat)
+{
+	struct maple_enode *next;
+
+	while (mat->head) {
+		next = mte_to_mat(mat->head)->next;
+		mas_free(mas, mat->head);
+		mat->head = next;
+	}
+}
+
+/*
+ * mas_mat_destroy() - Free all nodes and subtrees in a dead list.
+ * @mas - the maple state
+ * @mat - the ma_topiary linked list of dead nodes to free.
+ *
+ * Destroy walk a dead list.
+ */
+static void mas_mat_destroy(struct ma_state *mas, struct ma_topiary *mat)
+{
+	struct maple_enode *next;
+
+	while (mat->head) {
+		next = mte_to_mat(mat->head)->next;
+		mte_destroy_walk(mat->head, mat->mtree);
+		mat->head = next;
+	}
+}
+/*
+ * mas_descend() - Descend into the slot stored in the ma_state.
+ * @mas - the maple state.
+ *
+ * Note: Not RCU safe, only use in write side or debug code.
+ */
+static inline void mas_descend(struct ma_state *mas)
+{
+	enum maple_type type;
+	unsigned long *pivots;
+	struct maple_node *node;
+	void __rcu **slots;
+
+	node = mas_mn(mas);
+	type = mte_node_type(mas->node);
+	pivots = ma_pivots(node, type);
+	slots = ma_slots(node, type);
+
+	if (mas->offset)
+		mas->min = pivots[mas->offset - 1] + 1;
+	mas->max = mas_safe_pivot(mas, pivots, mas->offset, type);
+	mas->node = mas_slot(mas, slots, mas->offset);
+}
+
+/*
+ * mte_set_gap() - Set a maple node gap.
+ * @mn: The encoded maple node
+ * @gap: The offset of the gap to set
+ * @val: The gap value
+ */
+static inline void mte_set_gap(const struct maple_enode *mn,
+				 unsigned char gap, unsigned long val)
+{
+	switch (mte_node_type(mn)) {
+	default:
+		break;
+	case maple_arange_64:
+		mte_to_node(mn)->ma64.gap[gap] = val;
+		break;
+	}
+}
+
+/*
+ * mas_ascend() - Walk up a level of the tree.
+ * @mas: The maple state
+ *
+ * Sets the @mas->max and @mas->min to the correct values when walking up.  This
+ * may cause several levels of walking up to find the correct min and max.
+ * May find a dead node which will cause a premature return.
+ * Return: 1 on dead node, 0 otherwise
+ */
+static int mas_ascend(struct ma_state *mas)
+{
+	struct maple_enode *p_enode; /* parent enode. */
+	struct maple_enode *a_enode; /* ancestor enode. */
+	struct maple_node *a_node; /* ancestor node. */
+	struct maple_node *p_node; /* parent node. */
+	unsigned char a_slot;
+	enum maple_type a_type;
+	unsigned long min, max;
+	unsigned long *pivots;
+	unsigned char offset;
+	bool set_max = false, set_min = false;
+
+	a_node = mas_mn(mas);
+	if (ma_is_root(a_node)) {
+		mas->offset = 0;
+		return 0;
+	}
+
+	p_node = mte_parent(mas->node);
+	if (unlikely(a_node == p_node))
+		return 1;
+	a_type = mas_parent_enum(mas, mas->node);
+	offset = mte_parent_slot(mas->node);
+	a_enode = mt_mk_node(p_node, a_type);
+
+	/* Check to make sure all parent information is still accurate */
+	if (p_node != mte_parent(mas->node))
+		return 1;
+
+	mas->node = a_enode;
+	mas->offset = offset;
+
+	if (mte_is_root(a_enode)) {
+		mas->max = ULONG_MAX;
+		mas->min = 0;
+		return 0;
+	}
+
+	min = 0;
+	max = ULONG_MAX;
+	do {
+		p_enode = a_enode;
+		a_type = mas_parent_enum(mas, p_enode);
+		a_node = mte_parent(p_enode);
+		a_slot = mte_parent_slot(p_enode);
+		a_enode = mt_mk_node(a_node, a_type);
+		pivots = ma_pivots(a_node, a_type);
+
+		if (unlikely(ma_dead_node(a_node)))
+			return 1;
+
+		if (!set_min && a_slot) {
+			set_min = true;
+			min = pivots[a_slot - 1] + 1;
+		}
+
+		if (!set_max && a_slot < mt_pivots[a_type]) {
+			set_max = true;
+			max = pivots[a_slot];
+		}
+
+		if (unlikely(ma_dead_node(a_node)))
+			return 1;
+
+		if (unlikely(ma_is_root(a_node)))
+			break;
+
+	} while (!set_min || !set_max);
+
+	mas->max = max;
+	mas->min = min;
+	return 0;
+}
+
+/*
+ * mas_pop_node() - Get a previously allocated maple node from the maple state.
+ * @mas: The maple state
+ *
+ * Return: A pointer to a maple node.
+ */
+static inline struct maple_node *mas_pop_node(struct ma_state *mas)
+{
+	struct maple_alloc *ret, *node = mas->alloc;
+	unsigned long total = mas_allocated(mas);
+	unsigned int req = mas_alloc_req(mas);
+
+	/* nothing or a request pending. */
+	if (WARN_ON(!total))
+		return NULL;
+
+	if (total == 1) {
+		/* single allocation in this ma_state */
+		mas->alloc = NULL;
+		ret = node;
+		goto single_node;
+	}
+
+	if (node->node_count == 1) {
+		/* Single allocation in this node. */
+		mas->alloc = node->slot[0];
+		mas->alloc->total = node->total - 1;
+		ret = node;
+		goto new_head;
+	}
+	node->total--;
+	ret = node->slot[--node->node_count];
+	node->slot[node->node_count] = NULL;
+
+single_node:
+new_head:
+	if (req) {
+		req++;
+		mas_set_alloc_req(mas, req);
+	}
+
+	memset(ret, 0, sizeof(*ret));
+	return (struct maple_node *)ret;
+}
+
+/*
+ * mas_push_node() - Push a node back on the maple state allocation.
+ * @mas: The maple state
+ * @used: The used maple node
+ *
+ * Stores the maple node back into @mas->alloc for reuse.  Updates allocated and
+ * requested node count as necessary.
+ */
+static inline void mas_push_node(struct ma_state *mas, struct maple_node *used)
+{
+	struct maple_alloc *reuse = (struct maple_alloc *)used;
+	struct maple_alloc *head = mas->alloc;
+	unsigned long count;
+	unsigned int requested = mas_alloc_req(mas);
+
+	count = mas_allocated(mas);
+
+	reuse->request_count = 0;
+	reuse->node_count = 0;
+	if (count && (head->node_count < MAPLE_ALLOC_SLOTS)) {
+		head->slot[head->node_count++] = reuse;
+		head->total++;
+		goto done;
+	}
+
+	reuse->total = 1;
+	if ((head) && !((unsigned long)head & 0x1)) {
+		reuse->slot[0] = head;
+		reuse->node_count = 1;
+		reuse->total += head->total;
+	}
+
+	mas->alloc = reuse;
+done:
+	if (requested > 1)
+		mas_set_alloc_req(mas, requested - 1);
+}
+
+/*
+ * mas_alloc_nodes() - Allocate nodes into a maple state
+ * @mas: The maple state
+ * @gfp: The GFP Flags
+ */
+static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
+{
+	struct maple_alloc *node;
+	unsigned long allocated = mas_allocated(mas);
+	unsigned int requested = mas_alloc_req(mas);
+	unsigned int count;
+	void **slots = NULL;
+	unsigned int max_req = 0;
+
+	if (!requested)
+		return;
+
+	mas_set_alloc_req(mas, 0);
+	if (mas->mas_flags & MA_STATE_PREALLOC) {
+		if (allocated)
+			return;
+		WARN_ON(!allocated);
+	}
+
+	if (!allocated || mas->alloc->node_count == MAPLE_ALLOC_SLOTS) {
+		node = (struct maple_alloc *)mt_alloc_one(gfp);
+		if (!node)
+			goto nomem_one;
+
+		if (allocated) {
+			node->slot[0] = mas->alloc;
+			node->node_count = 1;
+		} else {
+			node->node_count = 0;
+		}
+
+		mas->alloc = node;
+		node->total = ++allocated;
+		requested--;
+	}
+
+	node = mas->alloc;
+	node->request_count = 0;
+	while (requested) {
+		max_req = MAPLE_ALLOC_SLOTS - node->node_count;
+		slots = (void **)&node->slot[node->node_count];
+		max_req = min(requested, max_req);
+		count = mt_alloc_bulk(gfp, max_req, slots);
+		if (!count)
+			goto nomem_bulk;
+
+		if (node->node_count == 0) {
+			node->slot[0]->node_count = 0;
+			node->slot[0]->request_count = 0;
+		}
+
+		node->node_count += count;
+		allocated += count;
+		node = node->slot[0];
+		requested -= count;
+	}
+	mas->alloc->total = allocated;
+	return;
+
+nomem_bulk:
+	/* Clean up potential freed allocations on bulk failure */
+	memset(slots, 0, max_req * sizeof(unsigned long));
+nomem_one:
+	mas_set_alloc_req(mas, requested);
+	if (mas->alloc && !(((unsigned long)mas->alloc & 0x1)))
+		mas->alloc->total = allocated;
+	mas_set_err(mas, -ENOMEM);
+	return;
+
+}
+
+/*
+ * mas_free() - Free an encoded maple node
+ * @mas: The maple state
+ * @used: The encoded maple node to free.
+ *
+ * Uses rcu free if necessary, pushes @used back on the maple state allocations
+ * otherwise.
+ */
+static inline void mas_free(struct ma_state *mas, struct maple_enode *used)
+{
+	struct maple_node *tmp = mte_to_node(used);
+
+	if (mt_in_rcu(mas->tree))
+		ma_free_rcu(tmp);
+	else
+		mas_push_node(mas, tmp);
+}
+
+/*
+ * mas_node_count() - Check if enough nodes are allocated and request more if
+ * there is not enough nodes.
+ * @mas: The maple state
+ * @count: The number of nodes needed
+ * @gfp: the gfp flags
+ */
+static void mas_node_count_gfp(struct ma_state *mas, int count, gfp_t gfp)
+{
+	unsigned long allocated = mas_allocated(mas);
+
+	if (allocated < count) {
+		mas_set_alloc_req(mas, count - allocated);
+		mas_alloc_nodes(mas, gfp);
+	}
+}
+
+/*
+ * mas_node_count() - Check if enough nodes are allocated and request more if
+ * there is not enough nodes.
+ * @mas: The maple state
+ * @count: The number of nodes needed
+ *
+ * Note: Uses GFP_NOWAIT | __GFP_NOWARN for gfp flags.
+ */
+static void mas_node_count(struct ma_state *mas, int count)
+{
+	return mas_node_count_gfp(mas, count, GFP_NOWAIT | __GFP_NOWARN);
+}
+
+/*
+ * mas_start() - Sets up maple state for operations.
+ * @mas: The maple state.
+ *
+ * If mas->node == MAS_START, then set the min, max and depth to
+ * defaults.
+ *
+ * Return:
+ * - If mas->node is an error or not MAS_START, return NULL.
+ * - If it's an empty tree:     NULL & mas->node == MAS_NONE
+ * - If it's a single entry:    The entry & mas->node == MAS_ROOT
+ * - If it's a tree:            NULL & mas->node == safe root node.
+ */
+static inline struct maple_enode *mas_start(struct ma_state *mas)
+{
+	if (likely(mas_is_start(mas))) {
+		struct maple_enode *root;
+
+		mas->min = 0;
+		mas->max = ULONG_MAX;
+		mas->depth = 0;
+
+retry:
+		root = mas_root(mas);
+		/* Tree with nodes */
+		if (likely(xa_is_node(root))) {
+			mas->depth = 1;
+			mas->node = mte_safe_root(root);
+			mas->offset = 0;
+			if (mte_dead_node(mas->node))
+				goto retry;
+
+			return NULL;
+		}
+
+		/* empty tree */
+		if (unlikely(!root)) {
+			mas->node = MAS_NONE;
+			mas->offset = MAPLE_NODE_SLOTS;
+			return NULL;
+		}
+
+		/* Single entry tree */
+		mas->node = MAS_ROOT;
+		mas->offset = MAPLE_NODE_SLOTS;
+
+		/* Single entry tree. */
+		if (mas->index > 0)
+			return NULL;
+
+		return root;
+	}
+
+	return NULL;
+}
+
+/*
+ * ma_data_end() - Find the end of the data in a node.
+ * @node: The maple node
+ * @type: The maple node type
+ * @pivots: The array of pivots in the node
+ * @max: The maximum value in the node
+ *
+ * Uses metadata to find the end of the data when possible.
+ * Return: The zero indexed last slot with data (may be null).
+ */
+static inline unsigned char ma_data_end(struct maple_node *node,
+					enum maple_type type,
+					unsigned long *pivots,
+					unsigned long max)
+{
+	unsigned char offset;
+
+	if (!pivots)
+		return 0;
+
+	if (type == maple_arange_64)
+		return ma_meta_end(node, type);
+
+	offset = mt_pivots[type] - 1;
+	if (likely(!pivots[offset]))
+		return ma_meta_end(node, type);
+
+	if (likely(pivots[offset] == max))
+		return offset;
+
+	return mt_pivots[type];
+}
+
+/*
+ * mas_data_end() - Find the end of the data (slot).
+ * @mas: the maple state
+ *
+ * This method is optimized to check the metadata of a node if the node type
+ * supports data end metadata.
+ *
+ * Return: The zero indexed last slot with data (may be null).
+ */
+static inline unsigned char mas_data_end(struct ma_state *mas)
+{
+	enum maple_type type;
+	struct maple_node *node;
+	unsigned char offset;
+	unsigned long *pivots;
+
+	type = mte_node_type(mas->node);
+	node = mas_mn(mas);
+	if (type == maple_arange_64)
+		return ma_meta_end(node, type);
+
+	pivots = ma_pivots(node, type);
+	if (unlikely(ma_dead_node(node)))
+		return 0;
+
+	offset = mt_pivots[type] - 1;
+	if (likely(!pivots[offset]))
+		return ma_meta_end(node, type);
+
+	if (likely(pivots[offset] == mas->max))
+		return offset;
+
+	return mt_pivots[type];
+}
+
+/*
+ * mas_leaf_max_gap() - Returns the largest gap in a leaf node
+ * @mas - the maple state
+ *
+ * Return: The maximum gap in the leaf.
+ */
+static unsigned long mas_leaf_max_gap(struct ma_state *mas)
+{
+	enum maple_type mt;
+	unsigned long pstart, gap, max_gap;
+	struct maple_node *mn;
+	unsigned long *pivots;
+	void __rcu **slots;
+	unsigned char i;
+	unsigned char max_piv;
+
+	mt = mte_node_type(mas->node);
+	mn = mas_mn(mas);
+	slots = ma_slots(mn, mt);
+	max_gap = 0;
+	if (unlikely(ma_is_dense(mt))) {
+		gap = 0;
+		for (i = 0; i < mt_slots[mt]; i++) {
+			if (slots[i]) {
+				if (gap > max_gap)
+					max_gap = gap;
+				gap = 0;
+			} else {
+				gap++;
+			}
+		}
+		if (gap > max_gap)
+			max_gap = gap;
+		return max_gap;
+	}
+
+	/*
+	 * Check the first implied pivot optimizes the loop below and slot 1 may
+	 * be skipped if there is a gap in slot 0.
+	 */
+	pivots = ma_pivots(mn, mt);
+	if (likely(!slots[0])) {
+		max_gap = pivots[0] - mas->min + 1;
+		i = 2;
+	} else {
+		i = 1;
+	}
+
+	/* reduce max_piv as the special case is checked before the loop */
+	max_piv = ma_data_end(mn, mt, pivots, mas->max) - 1;
+	/*
+	 * Check end implied pivot which can only be a gap on the right most
+	 * node.
+	 */
+	if (unlikely(mas->max == ULONG_MAX) && !slots[max_piv + 1]) {
+		gap = ULONG_MAX - pivots[max_piv];
+		if (gap > max_gap)
+			max_gap = gap;
+	}
+
+	for (; i <= max_piv; i++) {
+		/* data == no gap. */
+		if (likely(slots[i]))
+			continue;
+
+		pstart = pivots[i - 1];
+		gap = pivots[i] - pstart;
+		if (gap > max_gap)
+			max_gap = gap;
+
+		/* There cannot be two gaps in a row. */
+		i++;
+	}
+	return max_gap;
+}
+
+/*
+ * ma_max_gap() - Get the maximum gap in a maple node (non-leaf)
+ * @node: The maple node
+ * @gaps: The pointer to the gaps
+ * @mt: The maple node type
+ * @*off: Pointer to store the offset location of the gap.
+ *
+ * Uses the metadata data end to scan backwards across set gaps.
+ *
+ * Return: The maximum gap value
+ */
+static inline unsigned long
+ma_max_gap(struct maple_node *node, unsigned long *gaps, enum maple_type mt,
+	    unsigned char *off)
+{
+	unsigned char offset, i;
+	unsigned long max_gap = 0;
+
+	i = offset = ma_meta_end(node, mt);
+	do {
+		if (gaps[i] > max_gap) {
+			max_gap = gaps[i];
+			offset = i;
+		}
+	} while (i--);
+
+	*off = offset;
+	return max_gap;
+}
+
+/*
+ * mas_max_gap() - find the largest gap in a non-leaf node and set the slot.
+ * @mas: The maple state.
+ *
+ * If the metadata gap is set to MAPLE_ARANGE64_META_MAX, there is no gap.
+ *
+ * Return: The gap value.
+ */
+static inline unsigned long mas_max_gap(struct ma_state *mas)
+{
+	unsigned long *gaps;
+	unsigned char offset;
+	enum maple_type mt;
+	struct maple_node *node;
+
+	mt = mte_node_type(mas->node);
+	if (ma_is_leaf(mt))
+		return mas_leaf_max_gap(mas);
+
+	node = mas_mn(mas);
+	offset = ma_meta_gap(node, mt);
+	if (offset == MAPLE_ARANGE64_META_MAX)
+		return 0;
+
+	gaps = ma_gaps(node, mt);
+	return gaps[offset];
+}
+
+/*
+ * mas_parent_gap() - Set the parent gap and any gaps above, as needed
+ * @mas: The maple state
+ * @offset: The gap offset in the parent to set
+ * @new: The new gap value.
+ *
+ * Set the parent gap then continue to set the gap upwards, using the metadata
+ * of the parent to see if it is necessary to check the node above.
+ */
+static inline void mas_parent_gap(struct ma_state *mas, unsigned char offset,
+		unsigned long new)
+{
+	unsigned long meta_gap = 0;
+	struct maple_node *pnode;
+	struct maple_enode *penode;
+	unsigned long *pgaps;
+	unsigned char meta_offset;
+	enum maple_type pmt;
+
+	pnode = mte_parent(mas->node);
+	pmt = mas_parent_enum(mas, mas->node);
+	penode = mt_mk_node(pnode, pmt);
+	pgaps = ma_gaps(pnode, pmt);
+
+ascend:
+	meta_offset = ma_meta_gap(pnode, pmt);
+	if (meta_offset == MAPLE_ARANGE64_META_MAX)
+		meta_gap = 0;
+	else
+		meta_gap = pgaps[meta_offset];
+
+	pgaps[offset] = new;
+
+	if (meta_gap == new)
+		return;
+
+	if (offset != meta_offset) {
+		if (meta_gap > new)
+			return;
+
+		ma_set_meta_gap(pnode, pmt, offset);
+	} else if (new < meta_gap) {
+		meta_offset = 15;
+		new = ma_max_gap(pnode, pgaps, pmt, &meta_offset);
+		ma_set_meta_gap(pnode, pmt, meta_offset);
+	}
+
+	if (ma_is_root(pnode))
+		return;
+
+	/* Go to the parent node. */
+	pnode = mte_parent(penode);
+	pmt = mas_parent_enum(mas, penode);
+	pgaps = ma_gaps(pnode, pmt);
+	offset = mte_parent_slot(penode);
+	penode = mt_mk_node(pnode, pmt);
+	goto ascend;
+}
+
+/*
+ * mas_update_gap() - Update a nodes gaps and propagate up if necessary.
+ * @mas - the maple state.
+ */
+static inline void mas_update_gap(struct ma_state *mas)
+{
+	unsigned char pslot;
+	unsigned long p_gap;
+	unsigned long max_gap;
+
+	if (!mt_is_alloc(mas->tree))
+		return;
+
+	if (mte_is_root(mas->node))
+		return;
+
+	max_gap = mas_max_gap(mas);
+
+	pslot = mte_parent_slot(mas->node);
+	p_gap = ma_gaps(mte_parent(mas->node),
+			mas_parent_enum(mas, mas->node))[pslot];
+
+	if (p_gap != max_gap)
+		mas_parent_gap(mas, pslot, max_gap);
+}
+
+/*
+ * mas_adopt_children() - Set the parent pointer of all nodes in @parent to
+ * @parent with the slot encoded.
+ * @mas - the maple state (for the tree)
+ * @parent - the maple encoded node containing the children.
+ */
+static inline void mas_adopt_children(struct ma_state *mas,
+		struct maple_enode *parent)
+{
+	enum maple_type type = mte_node_type(parent);
+	struct maple_node *node = mas_mn(mas);
+	void __rcu **slots = ma_slots(node, type);
+	unsigned long *pivots = ma_pivots(node, type);
+	struct maple_enode *child;
+	unsigned char offset;
+
+	offset = ma_data_end(node, type, pivots, mas->max);
+	do {
+		child = mas_slot_locked(mas, slots, offset);
+		mte_set_parent(child, parent, offset);
+	} while (offset--);
+}
+
+/*
+ * mas_replace() - Replace a maple node in the tree with mas->node.  Uses the
+ * parent encoding to locate the maple node in the tree.
+ * @mas - the ma_state to use for operations.
+ * @advanced - boolean to adopt the child nodes and free the old node (false) or
+ * leave the node (true) and handle the adoption and free elsewhere.
+ */
+static inline void mas_replace(struct ma_state *mas, bool advanced)
+	__must_hold(mas->tree->lock)
+{
+	struct maple_node *mn = mas_mn(mas);
+	struct maple_enode *old_enode;
+	unsigned char offset = 0;
+	void __rcu **slots = NULL;
+
+	if (ma_is_root(mn)) {
+		old_enode = mas_root_locked(mas);
+	} else {
+		offset = mte_parent_slot(mas->node);
+		slots = ma_slots(mte_parent(mas->node),
+				 mas_parent_enum(mas, mas->node));
+		old_enode = mas_slot_locked(mas, slots, offset);
+	}
+
+	if (!advanced && !mte_is_leaf(mas->node))
+		mas_adopt_children(mas, mas->node);
+
+	if (mte_is_root(mas->node)) {
+		mn->parent = ma_parent_ptr(
+			      ((unsigned long)mas->tree | MA_ROOT_PARENT));
+		rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
+		mas_set_height(mas);
+	} else {
+		rcu_assign_pointer(slots[offset], mas->node);
+	}
+
+	if (!advanced) {
+		mte_set_node_dead(old_enode);
+		mas_free(mas, old_enode);
+	}
+}
+
+/*
+ * mas_new_child() - Find the new child of a node.
+ * @mas: the maple state
+ * @child: the maple state to store the child.
+ */
+static inline bool mas_new_child(struct ma_state *mas, struct ma_state *child)
+	__must_hold(mas->tree->lock)
+{
+	enum maple_type mt;
+	unsigned char offset;
+	unsigned char end;
+	unsigned long *pivots;
+	struct maple_enode *entry;
+	struct maple_node *node;
+	void __rcu **slots;
+
+	mt = mte_node_type(mas->node);
+	node = mas_mn(mas);
+	slots = ma_slots(node, mt);
+	pivots = ma_pivots(node, mt);
+	end = ma_data_end(node, mt, pivots, mas->max);
+	for (offset = mas->offset; offset <= end; offset++) {
+		entry = mas_slot_locked(mas, slots, offset);
+		if (mte_parent(entry) == node) {
+			*child = *mas;
+			mas->offset = offset + 1;
+			child->offset = offset;
+			mas_descend(child);
+			child->offset = 0;
+			return true;
+		}
+	}
+	return false;
+}
+
+/*
+ * mab_shift_right() - Shift the data in mab right. Note, does not clean out the
+ * old data or set b_node->b_end.
+ * @b_node: the maple_big_node
+ * @shift: the shift count
+ */
+static inline void mab_shift_right(struct maple_big_node *b_node,
+				 unsigned char shift)
+{
+	unsigned long size = b_node->b_end * sizeof(unsigned long);
+
+	memmove(b_node->pivot + shift, b_node->pivot, size);
+	memmove(b_node->slot + shift, b_node->slot, size);
+	if (b_node->type == maple_arange_64)
+		memmove(b_node->gap + shift, b_node->gap, size);
+}
+
+/*
+ * mab_middle_node() - Check if a middle node is needed (unlikely)
+ * @b_node: the maple_big_node that contains the data.
+ * @size: the amount of data in the b_node
+ * @split: the potential split location
+ * @slot_count: the size that can be stored in a single node being considered.
+ *
+ * Return: true if a middle node is required.
+ */
+static inline bool mab_middle_node(struct maple_big_node *b_node, int split,
+				   unsigned char slot_count)
+{
+	unsigned char size = b_node->b_end;
+
+	if (size >= 2 * slot_count)
+		return true;
+
+	if (!b_node->slot[split] && (size >= 2 * slot_count - 1))
+		return true;
+
+	return false;
+}
+
+/*
+ * mab_no_null_split() - ensure the split doesn't fall on a NULL
+ * @b_node: the maple_big_node with the data
+ * @split: the suggested split location
+ * @slot_count: the number of slots in the node being considered.
+ *
+ * Return: the split location.
+ */
+static inline int mab_no_null_split(struct maple_big_node *b_node,
+				    unsigned char split, unsigned char slot_count)
+{
+	if (!b_node->slot[split]) {
+		/*
+		 * If the split is less than the max slot && the right side will
+		 * still be sufficient, then increment the split on NULL.
+		 */
+		if ((split < slot_count - 1) &&
+		    (b_node->b_end - split) > (mt_min_slots[b_node->type]))
+			split++;
+		else
+			split--;
+	}
+	return split;
+}
+
+/*
+ * mab_calc_split() - Calculate the split location and if there needs to be two
+ * splits.
+ * @bn: The maple_big_node with the data
+ * @mid_split: The second split, if required.  0 otherwise.
+ *
+ * Return: The first split location.  The middle split is set in @mid_split.
+ */
+static inline int mab_calc_split(struct ma_state *mas,
+	 struct maple_big_node *bn, unsigned char *mid_split, unsigned long min)
+{
+	unsigned char b_end = bn->b_end;
+	int split = b_end / 2; /* Assume equal split. */
+	unsigned char slot_min, slot_count = mt_slots[bn->type];
+
+	/*
+	 * To support gap tracking, all NULL entries are kept together and a node cannot
+	 * end on a NULL entry, with the exception of the left-most leaf.  The
+	 * limitation means that the split of a node must be checked for this condition
+	 * and be able to put more data in one direction or the other.
+	 */
+	if (unlikely((mas->mas_flags & MA_STATE_BULK))) {
+		*mid_split = 0;
+		split = b_end - mt_min_slots[bn->type];
+
+		if (!ma_is_leaf(bn->type))
+			return split;
+
+		mas->mas_flags |= MA_STATE_REBALANCE;
+		if (!bn->slot[split])
+			split--;
+		return split;
+	}
+
+	/*
+	 * Although extremely rare, it is possible to enter what is known as the 3-way
+	 * split scenario.  The 3-way split comes about by means of a store of a range
+	 * that overwrites the end and beginning of two full nodes.  The result is a set
+	 * of entries that cannot be stored in 2 nodes.  Sometimes, these two nodes can
+	 * also be located in different parent nodes which are also full.  This can
+	 * carry upwards all the way to the root in the worst case.
+	 */
+	if (unlikely(mab_middle_node(bn, split, slot_count))) {
+		split = b_end / 3;
+		*mid_split = split * 2;
+	} else {
+		slot_min = mt_min_slots[bn->type];
+
+		*mid_split = 0;
+		/*
+		 * Avoid having a range less than the slot count unless it
+		 * causes one node to be deficient.
+		 * NOTE: mt_min_slots is 1 based, b_end and split are zero.
+		 */
+		while (((bn->pivot[split] - min) < slot_count - 1) &&
+		       (split < slot_count - 1) && (b_end - split > slot_min))
+			split++;
+	}
+
+	/* Avoid ending a node on a NULL entry */
+	split = mab_no_null_split(bn, split, slot_count);
+	if (!(*mid_split))
+		return split;
+
+	*mid_split = mab_no_null_split(bn, *mid_split, slot_count);
+
+	return split;
+}
+
+/*
+ * mas_mab_cp() - Copy data from a maple state inclusively to a maple_big_node
+ * and set @b_node->b_end to the next free slot.
+ * @mas: The maple state
+ * @mas_start: The starting slot to copy
+ * @mas_end: The end slot to copy (inclusively)
+ * @b_node: The maple_big_node to place the data
+ * @mab_start: The starting location in maple_big_node to store the data.
+ */
+static inline void mas_mab_cp(struct ma_state *mas, unsigned char mas_start,
+			unsigned char mas_end, struct maple_big_node *b_node,
+			unsigned char mab_start)
+{
+	enum maple_type mt;
+	struct maple_node *node;
+	void __rcu **slots;
+	unsigned long *pivots, *gaps;
+	int i = mas_start, j = mab_start;
+	unsigned char piv_end;
+
+	node = mas_mn(mas);
+	mt = mte_node_type(mas->node);
+	pivots = ma_pivots(node, mt);
+	if (!i) {
+		b_node->pivot[j] = pivots[i++];
+		if (unlikely(i > mas_end))
+			goto complete;
+		j++;
+	}
+
+	piv_end = min(mas_end, mt_pivots[mt]);
+	for (; i < piv_end; i++, j++) {
+		b_node->pivot[j] = pivots[i];
+		if (unlikely(!b_node->pivot[j]))
+			break;
+
+		if (unlikely(mas->max == b_node->pivot[j]))
+			goto complete;
+	}
+
+	if (likely(i <= mas_end))
+		b_node->pivot[j] = mas_safe_pivot(mas, pivots, i, mt);
+
+complete:
+	b_node->b_end = ++j;
+	j -= mab_start;
+	slots = ma_slots(node, mt);
+	memcpy(b_node->slot + mab_start, slots + mas_start, sizeof(void *) * j);
+	if (!ma_is_leaf(mt) && mt_is_alloc(mas->tree)) {
+		gaps = ma_gaps(node, mt);
+		memcpy(b_node->gap + mab_start, gaps + mas_start,
+		       sizeof(unsigned long) * j);
+	}
+}
+
+/*
+ * mas_leaf_set_meta() - Set the metadata of a leaf if possible.
+ * @mas: The maple state
+ * @node: The maple node
+ * @pivots: pointer to the maple node pivots
+ * @mt: The maple type
+ * @end: The assumed end
+ *
+ * Note, end may be incremented within this function but not modified at the
+ * source.  This is fine since the metadata is the last thing to be stored in a
+ * node during a write.
+ */
+static inline void mas_leaf_set_meta(struct ma_state *mas,
+		struct maple_node *node, unsigned long *pivots,
+		enum maple_type mt, unsigned char end)
+{
+	/* There is no room for metadata already */
+	if (mt_pivots[mt] <= end)
+		return;
+
+	if (pivots[end] && pivots[end] < mas->max)
+		end++;
+
+	if (end < mt_slots[mt] - 1)
+		ma_set_meta(node, mt, 0, end);
+}
+
+/*
+ * mab_mas_cp() - Copy data from maple_big_node to a maple encoded node.
+ * @b_node: the maple_big_node that has the data
+ * @mab_start: the start location in @b_node.
+ * @mab_end: The end location in @b_node (inclusively)
+ * @mas: The maple state with the maple encoded node.
+ */
+static inline void mab_mas_cp(struct maple_big_node *b_node,
+			      unsigned char mab_start, unsigned char mab_end,
+			      struct ma_state *mas, bool new_max)
+{
+	int i, j = 0;
+	enum maple_type mt = mte_node_type(mas->node);
+	struct maple_node *node = mte_to_node(mas->node);
+	void __rcu **slots = ma_slots(node, mt);
+	unsigned long *pivots = ma_pivots(node, mt);
+	unsigned long *gaps = NULL;
+	unsigned char end;
+
+	if (mab_end - mab_start > mt_pivots[mt])
+		mab_end--;
+
+	if (!pivots[mt_pivots[mt] - 1])
+		slots[mt_pivots[mt]] = NULL;
+
+	i = mab_start;
+	do {
+		pivots[j++] = b_node->pivot[i++];
+	} while (i <= mab_end && likely(b_node->pivot[i]));
+
+	memcpy(slots, b_node->slot + mab_start,
+	       sizeof(void *) * (i - mab_start));
+
+	if (new_max)
+		mas->max = b_node->pivot[i - 1];
+
+	end = j - 1;
+	if (likely(!ma_is_leaf(mt) && mt_is_alloc(mas->tree))) {
+		unsigned long max_gap = 0;
+		unsigned char offset = 15;
+
+		gaps = ma_gaps(node, mt);
+		do {
+			gaps[--j] = b_node->gap[--i];
+			if (gaps[j] > max_gap) {
+				offset = j;
+				max_gap = gaps[j];
+			}
+		} while (j);
+
+		ma_set_meta(node, mt, offset, end);
+	} else {
+		mas_leaf_set_meta(mas, node, pivots, mt, end);
+	}
+}
+
+/*
+ * mas_descend_adopt() - Descend through a sub-tree and adopt children.
+ * @mas: the maple state with the maple encoded node of the sub-tree.
+ *
+ * Descend through a sub-tree and adopt children who do not have the correct
+ * parents set.  Follow the parents which have the correct parents as they are
+ * the new entries which need to be followed to find other incorrectly set
+ * parents.
+ */
+static inline void mas_descend_adopt(struct ma_state *mas)
+{
+	struct ma_state list[3], next[3];
+	int i, n;
+
+	/*
+	 * At each level there may be up to 3 correct parent pointers which indicates
+	 * the new nodes which need to be walked to find any new nodes at a lower level.
+	 */
+
+	for (i = 0; i < 3; i++) {
+		list[i] = *mas;
+		list[i].offset = 0;
+		next[i].offset = 0;
+	}
+	next[0] = *mas;
+
+	while (!mte_is_leaf(list[0].node)) {
+		n = 0;
+		for (i = 0; i < 3; i++) {
+			if (mas_is_none(&list[i]))
+				continue;
+
+			if (i && list[i-1].node == list[i].node)
+				continue;
+
+			while ((n < 3) && (mas_new_child(&list[i], &next[n])))
+				n++;
+
+			mas_adopt_children(&list[i], list[i].node);
+		}
+
+		while (n < 3)
+			next[n++].node = MAS_NONE;
+
+		/* descend by setting the list to the children */
+		for (i = 0; i < 3; i++)
+			list[i] = next[i];
+	}
+}
+
+/*
+ * mas_bulk_rebalance() - Rebalance the end of a tree after a bulk insert.
+ * @mas: The maple state
+ * @end: The maple node end
+ * @mt: The maple node type
+ */
+static inline void mas_bulk_rebalance(struct ma_state *mas, unsigned char end,
+				      enum maple_type mt)
+{
+	if (!(mas->mas_flags & MA_STATE_BULK))
+		return;
+
+	if (mte_is_root(mas->node))
+		return;
+
+	if (end > mt_min_slots[mt]) {
+		mas->mas_flags &= ~MA_STATE_REBALANCE;
+		return;
+	}
+}
+
+/*
+ * mas_store_b_node() - Store an @entry into the b_node while also copying the
+ * data from a maple encoded node.
+ * @wr_mas: the maple write state
+ * @b_node: the maple_big_node to fill with data
+ * @offset_end: the offset to end copying
+ *
+ * Return: The actual end of the data stored in @b_node
+ */
+static inline void mas_store_b_node(struct ma_wr_state *wr_mas,
+		struct maple_big_node *b_node, unsigned char offset_end)
+{
+	unsigned char slot;
+	unsigned char b_end;
+	/* Possible underflow of piv will wrap back to 0 before use. */
+	unsigned long piv;
+	struct ma_state *mas = wr_mas->mas;
+
+	b_node->type = wr_mas->type;
+	b_end = 0;
+	slot = mas->offset;
+	if (slot) {
+		/* Copy start data up to insert. */
+		mas_mab_cp(mas, 0, slot - 1, b_node, 0);
+		b_end = b_node->b_end;
+		piv = b_node->pivot[b_end - 1];
+	} else
+		piv = mas->min - 1;
+
+	if (piv + 1 < mas->index) {
+		/* Handle range starting after old range */
+		b_node->slot[b_end] = wr_mas->content;
+		if (!wr_mas->content)
+			b_node->gap[b_end] = mas->index - 1 - piv;
+		b_node->pivot[b_end++] = mas->index - 1;
+	}
+
+	/* Store the new entry. */
+	mas->offset = b_end;
+	b_node->slot[b_end] = wr_mas->entry;
+	b_node->pivot[b_end] = mas->last;
+
+	/* Appended. */
+	if (mas->last >= mas->max)
+		goto b_end;
+
+	/* Handle new range ending before old range ends */
+	piv = mas_logical_pivot(mas, wr_mas->pivots, offset_end, wr_mas->type);
+	if (piv > mas->last) {
+		if (piv == ULONG_MAX)
+			mas_bulk_rebalance(mas, b_node->b_end, wr_mas->type);
+
+		if (offset_end != slot)
+			wr_mas->content = mas_slot_locked(mas, wr_mas->slots,
+							  offset_end);
+
+		b_node->slot[++b_end] = wr_mas->content;
+		if (!wr_mas->content)
+			b_node->gap[b_end] = piv - mas->last + 1;
+		b_node->pivot[b_end] = piv;
+	}
+
+	slot = offset_end + 1;
+	if (slot > wr_mas->node_end)
+		goto b_end;
+
+	/* Copy end data to the end of the node. */
+	mas_mab_cp(mas, slot, wr_mas->node_end + 1, b_node, ++b_end);
+	b_node->b_end--;
+	return;
+
+b_end:
+	b_node->b_end = b_end;
+}
+
+/*
+ * mas_prev_sibling() - Find the previous node with the same parent.
+ * @mas: the maple state
+ *
+ * Return: True if there is a previous sibling, false otherwise.
+ */
+static inline bool mas_prev_sibling(struct ma_state *mas)
+{
+	unsigned int p_slot = mte_parent_slot(mas->node);
+
+	if (mte_is_root(mas->node))
+		return false;
+
+	if (!p_slot)
+		return false;
+
+	mas_ascend(mas);
+	mas->offset = p_slot - 1;
+	mas_descend(mas);
+	return true;
+}
+
+/*
+ * mas_next_sibling() - Find the next node with the same parent.
+ * @mas: the maple state
+ *
+ * Return: true if there is a next sibling, false otherwise.
+ */
+static inline bool mas_next_sibling(struct ma_state *mas)
+{
+	MA_STATE(parent, mas->tree, mas->index, mas->last);
+
+	if (mte_is_root(mas->node))
+		return false;
+
+	parent = *mas;
+	mas_ascend(&parent);
+	parent.offset = mte_parent_slot(mas->node) + 1;
+	if (parent.offset > mas_data_end(&parent))
+		return false;
+
+	*mas = parent;
+	mas_descend(mas);
+	return true;
+}
+
+/*
+ * mte_node_or_node() - Return the encoded node or MAS_NONE.
+ * @enode: The encoded maple node.
+ *
+ * Shorthand to avoid setting %NULLs in the tree or maple_subtree_state.
+ *
+ * Return: @enode or MAS_NONE
+ */
+static inline struct maple_enode *mte_node_or_none(struct maple_enode *enode)
+{
+	if (enode)
+		return enode;
+
+	return ma_enode_ptr(MAS_NONE);
+}
+
+/*
+ * mas_wr_node_walk() - Find the correct offset for the index in the @mas.
+ * @wr_mas: The maple write state
+ *
+ * Uses mas_slot_locked() and does not need to worry about dead nodes.
+ */
+static inline void mas_wr_node_walk(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+	unsigned char count;
+	unsigned char offset;
+	unsigned long index, min, max;
+
+	if (unlikely(ma_is_dense(wr_mas->type))) {
+		wr_mas->r_max = wr_mas->r_min = mas->index;
+		mas->offset = mas->index = mas->min;
+		return;
+	}
+
+	wr_mas->node = mas_mn(wr_mas->mas);
+	wr_mas->pivots = ma_pivots(wr_mas->node, wr_mas->type);
+	count = wr_mas->node_end = ma_data_end(wr_mas->node, wr_mas->type,
+					       wr_mas->pivots, mas->max);
+	offset = mas->offset;
+	min = mas_safe_min(mas, wr_mas->pivots, offset);
+	if (unlikely(offset == count))
+		goto max;
+
+	max = wr_mas->pivots[offset];
+	index = mas->index;
+	if (unlikely(index <= max))
+		goto done;
+
+	if (unlikely(!max && offset))
+		goto max;
+
+	min = max + 1;
+	while (++offset < count) {
+		max = wr_mas->pivots[offset];
+		if (index <= max)
+			goto done;
+		else if (unlikely(!max))
+			break;
+
+		min = max + 1;
+	}
+
+max:
+	max = mas->max;
+done:
+	wr_mas->r_max = max;
+	wr_mas->r_min = min;
+	wr_mas->offset_end = mas->offset = offset;
+}
+
+/*
+ * mas_topiary_range() - Add a range of slots to the topiary.
+ * @mas: The maple state
+ * @destroy: The topiary to add the slots (usually destroy)
+ * @start: The starting slot inclusively
+ * @end: The end slot inclusively
+ */
+static inline void mas_topiary_range(struct ma_state *mas,
+	struct ma_topiary *destroy, unsigned char start, unsigned char end)
+{
+	void __rcu **slots;
+	unsigned char offset;
+
+	MT_BUG_ON(mas->tree, mte_is_leaf(mas->node));
+	slots = ma_slots(mas_mn(mas), mte_node_type(mas->node));
+	for (offset = start; offset <= end; offset++) {
+		struct maple_enode *enode = mas_slot_locked(mas, slots, offset);
+
+		if (mte_dead_node(enode))
+			continue;
+
+		mat_add(destroy, enode);
+	}
+}
+
+/*
+ * mast_topiary() - Add the portions of the tree to the removal list; either to
+ * be freed or discarded (destroy walk).
+ * @mast: The maple_subtree_state.
+ */
+static inline void mast_topiary(struct maple_subtree_state *mast)
+{
+	MA_WR_STATE(wr_mas, mast->orig_l, NULL);
+	unsigned char r_start, r_end;
+	unsigned char l_start, l_end;
+	void __rcu **l_slots, **r_slots;
+
+	wr_mas.type = mte_node_type(mast->orig_l->node);
+	mast->orig_l->index = mast->orig_l->last;
+	mas_wr_node_walk(&wr_mas);
+	l_start = mast->orig_l->offset + 1;
+	l_end = mas_data_end(mast->orig_l);
+	r_start = 0;
+	r_end = mast->orig_r->offset;
+
+	if (r_end)
+		r_end--;
+
+	l_slots = ma_slots(mas_mn(mast->orig_l),
+			   mte_node_type(mast->orig_l->node));
+
+	r_slots = ma_slots(mas_mn(mast->orig_r),
+			   mte_node_type(mast->orig_r->node));
+
+	if ((l_start < l_end) &&
+	    mte_dead_node(mas_slot_locked(mast->orig_l, l_slots, l_start))) {
+		l_start++;
+	}
+
+	if (mte_dead_node(mas_slot_locked(mast->orig_r, r_slots, r_end))) {
+		if (r_end)
+			r_end--;
+	}
+
+	if ((l_start > r_end) && (mast->orig_l->node == mast->orig_r->node))
+		return;
+
+	/* At the node where left and right sides meet, add the parts between */
+	if (mast->orig_l->node == mast->orig_r->node) {
+		return mas_topiary_range(mast->orig_l, mast->destroy,
+					     l_start, r_end);
+	}
+
+	/* mast->orig_r is different and consumed. */
+	if (mte_is_leaf(mast->orig_r->node))
+		return;
+
+	if (mte_dead_node(mas_slot_locked(mast->orig_l, l_slots, l_end)))
+		l_end--;
+
+
+	if (l_start <= l_end)
+		mas_topiary_range(mast->orig_l, mast->destroy, l_start, l_end);
+
+	if (mte_dead_node(mas_slot_locked(mast->orig_r, r_slots, r_start)))
+		r_start++;
+
+	if (r_start <= r_end)
+		mas_topiary_range(mast->orig_r, mast->destroy, 0, r_end);
+}
+
+/*
+ * mast_rebalance_next() - Rebalance against the next node
+ * @mast: The maple subtree state
+ * @old_r: The encoded maple node to the right (next node).
+ */
+static inline void mast_rebalance_next(struct maple_subtree_state *mast)
+{
+	unsigned char b_end = mast->bn->b_end;
+
+	mas_mab_cp(mast->orig_r, 0, mt_slot_count(mast->orig_r->node),
+		   mast->bn, b_end);
+	mast->orig_r->last = mast->orig_r->max;
+}
+
+/*
+ * mast_rebalance_prev() - Rebalance against the previous node
+ * @mast: The maple subtree state
+ * @old_l: The encoded maple node to the left (previous node)
+ */
+static inline void mast_rebalance_prev(struct maple_subtree_state *mast)
+{
+	unsigned char end = mas_data_end(mast->orig_l) + 1;
+	unsigned char b_end = mast->bn->b_end;
+
+	mab_shift_right(mast->bn, end);
+	mas_mab_cp(mast->orig_l, 0, end - 1, mast->bn, 0);
+	mast->l->min = mast->orig_l->min;
+	mast->orig_l->index = mast->orig_l->min;
+	mast->bn->b_end = end + b_end;
+	mast->l->offset += end;
+}
+
+/*
+ * mast_spanning_rebalance() - Rebalance nodes with nearest neighbour favouring
+ * the node to the right.  Checking the nodes to the right then the left at each
+ * level upwards until root is reached.  Free and destroy as needed.
+ * Data is copied into the @mast->bn.
+ * @mast: The maple_subtree_state.
+ */
+static inline
+bool mast_spanning_rebalance(struct maple_subtree_state *mast)
+{
+	struct ma_state r_tmp = *mast->orig_r;
+	struct ma_state l_tmp = *mast->orig_l;
+	struct maple_enode *ancestor = NULL;
+	unsigned char start, end;
+	unsigned char depth = 0;
+
+	r_tmp = *mast->orig_r;
+	l_tmp = *mast->orig_l;
+	do {
+		mas_ascend(mast->orig_r);
+		mas_ascend(mast->orig_l);
+		depth++;
+		if (!ancestor &&
+		    (mast->orig_r->node == mast->orig_l->node)) {
+			ancestor = mast->orig_r->node;
+			end = mast->orig_r->offset - 1;
+			start = mast->orig_l->offset + 1;
+		}
+
+		if (mast->orig_r->offset < mas_data_end(mast->orig_r)) {
+			if (!ancestor) {
+				ancestor = mast->orig_r->node;
+				start = 0;
+			}
+
+			mast->orig_r->offset++;
+			do {
+				mas_descend(mast->orig_r);
+				mast->orig_r->offset = 0;
+				depth--;
+			} while (depth);
+
+			mast_rebalance_next(mast);
+			do {
+				unsigned char l_off = 0;
+				struct maple_enode *child = r_tmp.node;
+
+				mas_ascend(&r_tmp);
+				if (ancestor == r_tmp.node)
+					l_off = start;
+
+				if (r_tmp.offset)
+					r_tmp.offset--;
+
+				if (l_off < r_tmp.offset)
+					mas_topiary_range(&r_tmp, mast->destroy,
+							  l_off, r_tmp.offset);
+
+				if (l_tmp.node != child)
+					mat_add(mast->free, child);
+
+			} while (r_tmp.node != ancestor);
+
+			*mast->orig_l = l_tmp;
+			return true;
+
+		} else if (mast->orig_l->offset != 0) {
+			if (!ancestor) {
+				ancestor = mast->orig_l->node;
+				end = mas_data_end(mast->orig_l);
+			}
+
+			mast->orig_l->offset--;
+			do {
+				mas_descend(mast->orig_l);
+				mast->orig_l->offset =
+					mas_data_end(mast->orig_l);
+				depth--;
+			} while (depth);
+
+			mast_rebalance_prev(mast);
+			do {
+				unsigned char r_off;
+				struct maple_enode *child = l_tmp.node;
+
+				mas_ascend(&l_tmp);
+				if (ancestor == l_tmp.node)
+					r_off = end;
+				else
+					r_off = mas_data_end(&l_tmp);
+
+				if (l_tmp.offset < r_off)
+					l_tmp.offset++;
+
+				if (l_tmp.offset < r_off)
+					mas_topiary_range(&l_tmp, mast->destroy,
+							  l_tmp.offset, r_off);
+
+				if (r_tmp.node != child)
+					mat_add(mast->free, child);
+
+			} while (l_tmp.node != ancestor);
+
+			*mast->orig_r = r_tmp;
+			return true;
+		}
+	} while (!mte_is_root(mast->orig_r->node));
+
+	*mast->orig_r = r_tmp;
+	*mast->orig_l = l_tmp;
+	return false;
+}
+
+/*
+ * mast_ascend_free() - Add current original maple state nodes to the free list
+ * and ascend.
+ * @mast: the maple subtree state.
+ *
+ * Ascend the original left and right sides and add the previous nodes to the
+ * free list.  Set the slots to point to the correct location in the new nodes.
+ */
+static inline void
+mast_ascend_free(struct maple_subtree_state *mast)
+{
+	MA_WR_STATE(wr_mas, mast->orig_r,  NULL);
+	struct maple_enode *left = mast->orig_l->node;
+	struct maple_enode *right = mast->orig_r->node;
+
+	mas_ascend(mast->orig_l);
+	mas_ascend(mast->orig_r);
+	mat_add(mast->free, left);
+
+	if (left != right)
+		mat_add(mast->free, right);
+
+	mast->orig_r->offset = 0;
+	mast->orig_r->index = mast->r->max;
+	/* last should be larger than or equal to index */
+	if (mast->orig_r->last < mast->orig_r->index)
+		mast->orig_r->last = mast->orig_r->index;
+	/*
+	 * The node may not contain the value so set slot to ensure all
+	 * of the nodes contents are freed or destroyed.
+	 */
+	wr_mas.type = mte_node_type(mast->orig_r->node);
+	mas_wr_node_walk(&wr_mas);
+	/* Set up the left side of things */
+	mast->orig_l->offset = 0;
+	mast->orig_l->index = mast->l->min;
+	wr_mas.mas = mast->orig_l;
+	wr_mas.type = mte_node_type(mast->orig_l->node);
+	mas_wr_node_walk(&wr_mas);
+
+	mast->bn->type = wr_mas.type;
+}
+
+/*
+ * mas_new_ma_node() - Create and return a new maple node.  Helper function.
+ * @mas: the maple state with the allocations.
+ * @b_node: the maple_big_node with the type encoding.
+ *
+ * Use the node type from the maple_big_node to allocate a new node from the
+ * ma_state.  This function exists mainly for code readability.
+ *
+ * Return: A new maple encoded node
+ */
+static inline struct maple_enode
+*mas_new_ma_node(struct ma_state *mas, struct maple_big_node *b_node)
+{
+	return mt_mk_node(ma_mnode_ptr(mas_pop_node(mas)), b_node->type);
+}
+
+/*
+ * mas_mab_to_node() - Set up right and middle nodes
+ *
+ * @mas: the maple state that contains the allocations.
+ * @b_node: the node which contains the data.
+ * @left: The pointer which will have the left node
+ * @right: The pointer which may have the right node
+ * @middle: the pointer which may have the middle node (rare)
+ * @mid_split: the split location for the middle node
+ *
+ * Return: the split of left.
+ */
+static inline unsigned char mas_mab_to_node(struct ma_state *mas,
+	struct maple_big_node *b_node, struct maple_enode **left,
+	struct maple_enode **right, struct maple_enode **middle,
+	unsigned char *mid_split, unsigned long min)
+{
+	unsigned char split = 0;
+	unsigned char slot_count = mt_slots[b_node->type];
+
+	*left = mas_new_ma_node(mas, b_node);
+	*right = NULL;
+	*middle = NULL;
+	*mid_split = 0;
+
+	if (b_node->b_end < slot_count) {
+		split = b_node->b_end;
+	} else {
+		split = mab_calc_split(mas, b_node, mid_split, min);
+		*right = mas_new_ma_node(mas, b_node);
+	}
+
+	if (*mid_split)
+		*middle = mas_new_ma_node(mas, b_node);
+
+	return split;
+
+}
+
+/*
+ * mab_set_b_end() - Add entry to b_node at b_node->b_end and increment the end
+ * pointer.
+ * @b_node - the big node to add the entry
+ * @mas - the maple state to get the pivot (mas->max)
+ * @entry - the entry to add, if NULL nothing happens.
+ */
+static inline void mab_set_b_end(struct maple_big_node *b_node,
+				 struct ma_state *mas,
+				 void *entry)
+{
+	if (!entry)
+		return;
+
+	b_node->slot[b_node->b_end] = entry;
+	if (mt_is_alloc(mas->tree))
+		b_node->gap[b_node->b_end] = mas_max_gap(mas);
+	b_node->pivot[b_node->b_end++] = mas->max;
+}
+
+/*
+ * mas_set_split_parent() - combine_then_separate helper function.  Sets the parent
+ * of @mas->node to either @left or @right, depending on @slot and @split
+ *
+ * @mas - the maple state with the node that needs a parent
+ * @left - possible parent 1
+ * @right - possible parent 2
+ * @slot - the slot the mas->node was placed
+ * @split - the split location between @left and @right
+ */
+static inline void mas_set_split_parent(struct ma_state *mas,
+					struct maple_enode *left,
+					struct maple_enode *right,
+					unsigned char *slot, unsigned char split)
+{
+	if (mas_is_none(mas))
+		return;
+
+	if ((*slot) <= split)
+		mte_set_parent(mas->node, left, *slot);
+	else if (right)
+		mte_set_parent(mas->node, right, (*slot) - split - 1);
+
+	(*slot)++;
+}
+
+/*
+ * mte_mid_split_check() - Check if the next node passes the mid-split
+ * @**l: Pointer to left encoded maple node.
+ * @**m: Pointer to middle encoded maple node.
+ * @**r: Pointer to right encoded maple node.
+ * @slot: The offset
+ * @*split: The split location.
+ * @mid_split: The middle split.
+ */
+static inline void mte_mid_split_check(struct maple_enode **l,
+				       struct maple_enode **r,
+				       struct maple_enode *right,
+				       unsigned char slot,
+				       unsigned char *split,
+				       unsigned char mid_split)
+{
+	if (*r == right)
+		return;
+
+	if (slot < mid_split)
+		return;
+
+	*l = *r;
+	*r = right;
+	*split = mid_split;
+}
+
+/*
+ * mast_set_split_parents() - Helper function to set three nodes parents.  Slot
+ * is taken from @mast->l.
+ * @mast - the maple subtree state
+ * @left - the left node
+ * @right - the right node
+ * @split - the split location.
+ */
+static inline void mast_set_split_parents(struct maple_subtree_state *mast,
+					  struct maple_enode *left,
+					  struct maple_enode *middle,
+					  struct maple_enode *right,
+					  unsigned char split,
+					  unsigned char mid_split)
+{
+	unsigned char slot;
+	struct maple_enode *l = left;
+	struct maple_enode *r = right;
+
+	if (mas_is_none(mast->l))
+		return;
+
+	if (middle)
+		r = middle;
+
+	slot = mast->l->offset;
+
+	mte_mid_split_check(&l, &r, right, slot, &split, mid_split);
+	mas_set_split_parent(mast->l, l, r, &slot, split);
+
+	mte_mid_split_check(&l, &r, right, slot, &split, mid_split);
+	mas_set_split_parent(mast->m, l, r, &slot, split);
+
+	mte_mid_split_check(&l, &r, right, slot, &split, mid_split);
+	mas_set_split_parent(mast->r, l, r, &slot, split);
+}
+
+/*
+ * mas_wmb_replace() - Write memory barrier and replace
+ * @mas: The maple state
+ * @free: the maple topiary list of nodes to free
+ * @destroy: The maple topiary list of nodes to destroy (walk and free)
+ *
+ * Updates gap as necessary.
+ */
+static inline void mas_wmb_replace(struct ma_state *mas,
+				   struct ma_topiary *free,
+				   struct ma_topiary *destroy)
+{
+	/* All nodes must see old data as dead prior to replacing that data */
+	smp_wmb(); /* Needed for RCU */
+
+	/* Insert the new data in the tree */
+	mas_replace(mas, true);
+
+	if (!mte_is_leaf(mas->node))
+		mas_descend_adopt(mas);
+
+	mas_mat_free(mas, free);
+
+	if (destroy)
+		mas_mat_destroy(mas, destroy);
+
+	if (mte_is_leaf(mas->node))
+		return;
+
+	mas_update_gap(mas);
+}
+
+/*
+ * mast_new_root() - Set a new tree root during subtree creation
+ * @mast: The maple subtree state
+ * @mas: The maple state
+ */
+static inline void mast_new_root(struct maple_subtree_state *mast,
+				 struct ma_state *mas)
+{
+	mas_mn(mast->l)->parent =
+		ma_parent_ptr(((unsigned long)mas->tree | MA_ROOT_PARENT));
+	if (!mte_dead_node(mast->orig_l->node) &&
+	    !mte_is_root(mast->orig_l->node)) {
+		do {
+			mast_ascend_free(mast);
+			mast_topiary(mast);
+		} while (!mte_is_root(mast->orig_l->node));
+	}
+	if ((mast->orig_l->node != mas->node) &&
+		   (mast->l->depth > mas_mt_height(mas))) {
+		mat_add(mast->free, mas->node);
+	}
+}
+
+/*
+ * mast_cp_to_nodes() - Copy data out to nodes.
+ * @mast: The maple subtree state
+ * @left: The left encoded maple node
+ * @middle: The middle encoded maple node
+ * @right: The right encoded maple node
+ * @split: The location to split between left and (middle ? middle : right)
+ * @mid_split: The location to split between middle and right.
+ */
+static inline void mast_cp_to_nodes(struct maple_subtree_state *mast,
+	struct maple_enode *left, struct maple_enode *middle,
+	struct maple_enode *right, unsigned char split, unsigned char mid_split)
+{
+	bool new_lmax = true;
+
+	mast->l->node = mte_node_or_none(left);
+	mast->m->node = mte_node_or_none(middle);
+	mast->r->node = mte_node_or_none(right);
+
+	mast->l->min = mast->orig_l->min;
+	if (split == mast->bn->b_end) {
+		mast->l->max = mast->orig_r->max;
+		new_lmax = false;
+	}
+
+	mab_mas_cp(mast->bn, 0, split, mast->l, new_lmax);
+
+	if (middle) {
+		mab_mas_cp(mast->bn, 1 + split, mid_split, mast->m, true);
+		mast->m->min = mast->bn->pivot[split] + 1;
+		split = mid_split;
+	}
+
+	mast->r->max = mast->orig_r->max;
+	if (right) {
+		mab_mas_cp(mast->bn, 1 + split, mast->bn->b_end, mast->r, false);
+		mast->r->min = mast->bn->pivot[split] + 1;
+	}
+}
+
+/*
+ * mast_combine_cp_left - Copy in the original left side of the tree into the
+ * combined data set in the maple subtree state big node.
+ * @mast: The maple subtree state
+ */
+static inline void mast_combine_cp_left(struct maple_subtree_state *mast)
+{
+	unsigned char l_slot = mast->orig_l->offset;
+
+	if (!l_slot)
+		return;
+
+	mas_mab_cp(mast->orig_l, 0, l_slot - 1, mast->bn, 0);
+}
+
+/*
+ * mast_combine_cp_right: Copy in the original right side of the tree into the
+ * combined data set in the maple subtree state big node.
+ * @mast: The maple subtree state
+ */
+static inline void mast_combine_cp_right(struct maple_subtree_state *mast)
+{
+	if (mast->bn->pivot[mast->bn->b_end - 1] >= mast->orig_r->max)
+		return;
+
+	mas_mab_cp(mast->orig_r, mast->orig_r->offset + 1,
+		   mt_slot_count(mast->orig_r->node), mast->bn,
+		   mast->bn->b_end);
+	mast->orig_r->last = mast->orig_r->max;
+}
+
+/*
+ * mast_sufficient: Check if the maple subtree state has enough data in the big
+ * node to create at least one sufficient node
+ * @mast: the maple subtree state
+ */
+static inline bool mast_sufficient(struct maple_subtree_state *mast)
+{
+	if (mast->bn->b_end > mt_min_slot_count(mast->orig_l->node))
+		return true;
+
+	return false;
+}
+
+/*
+ * mast_overflow: Check if there is too much data in the subtree state for a
+ * single node.
+ * @mast: The maple subtree state
+ */
+static inline bool mast_overflow(struct maple_subtree_state *mast)
+{
+	if (mast->bn->b_end >= mt_slot_count(mast->orig_l->node))
+		return true;
+
+	return false;
+}
+
+static inline void *mtree_range_walk(struct ma_state *mas)
+{
+	unsigned long *pivots;
+	unsigned char offset;
+	struct maple_node *node;
+	struct maple_enode *next, *last;
+	enum maple_type type;
+	void __rcu **slots;
+	unsigned char end;
+	unsigned long max, min;
+	unsigned long prev_max, prev_min;
+
+	next = mas->node;
+	min = mas->min;
+	max = mas->max;
+	do {
+		offset = 0;
+		last = next;
+		node = mte_to_node(next);
+		type = mte_node_type(next);
+		pivots = ma_pivots(node, type);
+		end = ma_data_end(node, type, pivots, max);
+		if (unlikely(ma_dead_node(node)))
+			goto dead_node;
+
+		if (pivots[offset] >= mas->index) {
+			prev_max = max;
+			prev_min = min;
+			max = pivots[offset];
+			goto next;
+		}
+
+		do {
+			offset++;
+		} while ((offset < end) && (pivots[offset] < mas->index));
+
+		prev_min = min;
+		min = pivots[offset - 1] + 1;
+		prev_max = max;
+		if (likely(offset < end && pivots[offset]))
+			max = pivots[offset];
+
+next:
+		slots = ma_slots(node, type);
+		next = mt_slot(mas->tree, slots, offset);
+		if (unlikely(ma_dead_node(node)))
+			goto dead_node;
+	} while (!ma_is_leaf(type));
+
+	mas->offset = offset;
+	mas->index = min;
+	mas->last = max;
+	mas->min = prev_min;
+	mas->max = prev_max;
+	mas->node = last;
+	return (void *) next;
+
+dead_node:
+	mas_reset(mas);
+	return NULL;
+}
+
+/*
+ * mas_spanning_rebalance() - Rebalance across two nodes which may not be peers.
+ * @mas: The starting maple state
+ * @mast: The maple_subtree_state, keeps track of 4 maple states.
+ * @count: The estimated count of iterations needed.
+ *
+ * Follow the tree upwards from @l_mas and @r_mas for @count, or until the root
+ * is hit.  First @b_node is split into two entries which are inserted into the
+ * next iteration of the loop.  @b_node is returned populated with the final
+ * iteration. @mas is used to obtain allocations.  orig_l_mas keeps track of the
+ * nodes that will remain active by using orig_l_mas->index and orig_l_mas->last
+ * to account of what has been copied into the new sub-tree.  The update of
+ * orig_l_mas->last is used in mas_consume to find the slots that will need to
+ * be either freed or destroyed.  orig_l_mas->depth keeps track of the height of
+ * the new sub-tree in case the sub-tree becomes the full tree.
+ *
+ * Return: the number of elements in b_node during the last loop.
+ */
+static int mas_spanning_rebalance(struct ma_state *mas,
+		struct maple_subtree_state *mast, unsigned char count)
+{
+	unsigned char split, mid_split;
+	unsigned char slot = 0;
+	struct maple_enode *left = NULL, *middle = NULL, *right = NULL;
+
+	MA_STATE(l_mas, mas->tree, mas->index, mas->index);
+	MA_STATE(r_mas, mas->tree, mas->index, mas->last);
+	MA_STATE(m_mas, mas->tree, mas->index, mas->index);
+	MA_TOPIARY(free, mas->tree);
+	MA_TOPIARY(destroy, mas->tree);
+
+	/*
+	 * The tree needs to be rebalanced and leaves need to be kept at the same level.
+	 * Rebalancing is done by use of the ``struct maple_topiary``.
+	 */
+	mast->l = &l_mas;
+	mast->m = &m_mas;
+	mast->r = &r_mas;
+	mast->free = &free;
+	mast->destroy = &destroy;
+	l_mas.node = r_mas.node = m_mas.node = MAS_NONE;
+
+	/* Check if this is not root and has sufficient data.  */
+	if (((mast->orig_l->min != 0) || (mast->orig_r->max != ULONG_MAX)) &&
+	    unlikely(mast->bn->b_end <= mt_min_slots[mast->bn->type]))
+		mast_spanning_rebalance(mast);
+
+	mast->orig_l->depth = 0;
+
+	/*
+	 * Each level of the tree is examined and balanced, pushing data to the left or
+	 * right, or rebalancing against left or right nodes is employed to avoid
+	 * rippling up the tree to limit the amount of churn.  Once a new sub-section of
+	 * the tree is created, there may be a mix of new and old nodes.  The old nodes
+	 * will have the incorrect parent pointers and currently be in two trees: the
+	 * original tree and the partially new tree.  To remedy the parent pointers in
+	 * the old tree, the new data is swapped into the active tree and a walk down
+	 * the tree is performed and the parent pointers are updated.
+	 * See mas_descend_adopt() for more information..
+	 */
+	while (count--) {
+		mast->bn->b_end--;
+		mast->bn->type = mte_node_type(mast->orig_l->node);
+		split = mas_mab_to_node(mas, mast->bn, &left, &right, &middle,
+					&mid_split, mast->orig_l->min);
+		mast_set_split_parents(mast, left, middle, right, split,
+				       mid_split);
+		mast_cp_to_nodes(mast, left, middle, right, split, mid_split);
+
+		/*
+		 * Copy data from next level in the tree to mast->bn from next
+		 * iteration
+		 */
+		memset(mast->bn, 0, sizeof(struct maple_big_node));
+		mast->bn->type = mte_node_type(left);
+		mast->orig_l->depth++;
+
+		/* Root already stored in l->node. */
+		if (mas_is_root_limits(mast->l))
+			goto new_root;
+
+		mast_ascend_free(mast);
+		mast_combine_cp_left(mast);
+		l_mas.offset = mast->bn->b_end;
+		mab_set_b_end(mast->bn, &l_mas, left);
+		mab_set_b_end(mast->bn, &m_mas, middle);
+		mab_set_b_end(mast->bn, &r_mas, right);
+
+		/* Copy anything necessary out of the right node. */
+		mast_combine_cp_right(mast);
+		mast_topiary(mast);
+		mast->orig_l->last = mast->orig_l->max;
+
+		if (mast_sufficient(mast))
+			continue;
+
+		if (mast_overflow(mast))
+			continue;
+
+		/* May be a new root stored in mast->bn */
+		if (mas_is_root_limits(mast->orig_l))
+			break;
+
+		mast_spanning_rebalance(mast);
+
+		/* rebalancing from other nodes may require another loop. */
+		if (!count)
+			count++;
+	}
+
+	l_mas.node = mt_mk_node(ma_mnode_ptr(mas_pop_node(mas)),
+				mte_node_type(mast->orig_l->node));
+	mast->orig_l->depth++;
+	mab_mas_cp(mast->bn, 0, mt_slots[mast->bn->type] - 1, &l_mas, true);
+	mte_set_parent(left, l_mas.node, slot);
+	if (middle)
+		mte_set_parent(middle, l_mas.node, ++slot);
+
+	if (right)
+		mte_set_parent(right, l_mas.node, ++slot);
+
+	if (mas_is_root_limits(mast->l)) {
+new_root:
+		mast_new_root(mast, mas);
+	} else {
+		mas_mn(&l_mas)->parent = mas_mn(mast->orig_l)->parent;
+	}
+
+	if (!mte_dead_node(mast->orig_l->node))
+		mat_add(&free, mast->orig_l->node);
+
+	mas->depth = mast->orig_l->depth;
+	*mast->orig_l = l_mas;
+	mte_set_node_dead(mas->node);
+
+	/* Set up mas for insertion. */
+	mast->orig_l->depth = mas->depth;
+	mast->orig_l->alloc = mas->alloc;
+	*mas = *mast->orig_l;
+	mas_wmb_replace(mas, &free, &destroy);
+	mtree_range_walk(mas);
+	return mast->bn->b_end;
+}
+
+/*
+ * mas_rebalance() - Rebalance a given node.
+ * @mas: The maple state
+ * @b_node: The big maple node.
+ *
+ * Rebalance two nodes into a single node or two new nodes that are sufficient.
+ * Continue upwards until tree is sufficient.
+ *
+ * Return: the number of elements in b_node during the last loop.
+ */
+static inline int mas_rebalance(struct ma_state *mas,
+				struct maple_big_node *b_node)
+{
+	char empty_count = mas_mt_height(mas);
+	struct maple_subtree_state mast;
+	unsigned char shift, b_end = ++b_node->b_end;
+
+	MA_STATE(l_mas, mas->tree, mas->index, mas->last);
+	MA_STATE(r_mas, mas->tree, mas->index, mas->last);
+
+	trace_ma_op(__func__, mas);
+
+	/*
+	 * Rebalancing occurs if a node is insufficient.  Data is rebalanced
+	 * against the node to the right if it exists, otherwise the node to the
+	 * left of this node is rebalanced against this node.  If rebalancing
+	 * causes just one node to be produced instead of two, then the parent
+	 * is also examined and rebalanced if it is insufficient.  Every level
+	 * tries to combine the data in the same way.  If one node contains the
+	 * entire range of the tree, then that node is used as a new root node.
+	 */
+	mas_node_count(mas, 1 + empty_count * 3);
+	if (mas_is_err(mas))
+		return 0;
+
+	mast.orig_l = &l_mas;
+	mast.orig_r = &r_mas;
+	mast.bn = b_node;
+	mast.bn->type = mte_node_type(mas->node);
+
+	l_mas = r_mas = *mas;
+
+	if (mas_next_sibling(&r_mas)) {
+		mas_mab_cp(&r_mas, 0, mt_slot_count(r_mas.node), b_node, b_end);
+		r_mas.last = r_mas.index = r_mas.max;
+	} else {
+		mas_prev_sibling(&l_mas);
+		shift = mas_data_end(&l_mas) + 1;
+		mab_shift_right(b_node, shift);
+		mas->offset += shift;
+		mas_mab_cp(&l_mas, 0, shift - 1, b_node, 0);
+		b_node->b_end = shift + b_end;
+		l_mas.index = l_mas.last = l_mas.min;
+	}
+
+	return mas_spanning_rebalance(mas, &mast, empty_count);
+}
+
+/*
+ * mas_destroy_rebalance() - Rebalance left-most node while destroying the maple
+ * state.
+ * @mas: The maple state
+ * @end: The end of the left-most node.
+ *
+ * During a mass-insert event (such as forking), it may be necessary to
+ * rebalance the left-most node when it is not sufficient.
+ */
+static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end)
+{
+	enum maple_type mt = mte_node_type(mas->node);
+	struct maple_node reuse, *newnode, *parent, *new_left, *left, *node;
+	struct maple_enode *eparent;
+	unsigned char offset, tmp, split = mt_slots[mt] / 2;
+	void __rcu **l_slots, **slots;
+	unsigned long *l_pivs, *pivs, gap;
+	bool in_rcu = mt_in_rcu(mas->tree);
+
+	MA_STATE(l_mas, mas->tree, mas->index, mas->last);
+
+	l_mas = *mas;
+	mas_prev_sibling(&l_mas);
+
+	/* set up node. */
+	if (in_rcu) {
+		/* Allocate for both left and right as well as parent. */
+		mas_node_count(mas, 3);
+		if (mas_is_err(mas))
+			return;
+
+		newnode = mas_pop_node(mas);
+	} else {
+		newnode = &reuse;
+	}
+
+	node = mas_mn(mas);
+	newnode->parent = node->parent;
+	slots = ma_slots(newnode, mt);
+	pivs = ma_pivots(newnode, mt);
+	left = mas_mn(&l_mas);
+	l_slots = ma_slots(left, mt);
+	l_pivs = ma_pivots(left, mt);
+	if (!l_slots[split])
+		split++;
+	tmp = mas_data_end(&l_mas) - split;
+
+	memcpy(slots, l_slots + split + 1, sizeof(void *) * tmp);
+	memcpy(pivs, l_pivs + split + 1, sizeof(unsigned long) * tmp);
+	pivs[tmp] = l_mas.max;
+	memcpy(slots + tmp, ma_slots(node, mt), sizeof(void *) * end);
+	memcpy(pivs + tmp, ma_pivots(node, mt), sizeof(unsigned long) * end);
+
+	l_mas.max = l_pivs[split];
+	mas->min = l_mas.max + 1;
+	eparent = mt_mk_node(mte_parent(l_mas.node),
+			     mas_parent_enum(&l_mas, l_mas.node));
+	tmp += end;
+	if (!in_rcu) {
+		unsigned char max_p = mt_pivots[mt];
+		unsigned char max_s = mt_slots[mt];
+
+		if (tmp < max_p)
+			memset(pivs + tmp, 0,
+			       sizeof(unsigned long *) * (max_p - tmp));
+
+		if (tmp < mt_slots[mt])
+			memset(slots + tmp, 0, sizeof(void *) * (max_s - tmp));
+
+		memcpy(node, newnode, sizeof(struct maple_node));
+		ma_set_meta(node, mt, 0, tmp - 1);
+		mte_set_pivot(eparent, mte_parent_slot(l_mas.node),
+			      l_pivs[split]);
+
+		/* Remove data from l_pivs. */
+		tmp = split + 1;
+		memset(l_pivs + tmp, 0, sizeof(unsigned long) * (max_p - tmp));
+		memset(l_slots + tmp, 0, sizeof(void *) * (max_s - tmp));
+		ma_set_meta(left, mt, 0, split);
+
+		goto done;
+	}
+
+	/* RCU requires replacing both l_mas, mas, and parent. */
+	mas->node = mt_mk_node(newnode, mt);
+	ma_set_meta(newnode, mt, 0, tmp);
+
+	new_left = mas_pop_node(mas);
+	new_left->parent = left->parent;
+	mt = mte_node_type(l_mas.node);
+	slots = ma_slots(new_left, mt);
+	pivs = ma_pivots(new_left, mt);
+	memcpy(slots, l_slots, sizeof(void *) * split);
+	memcpy(pivs, l_pivs, sizeof(unsigned long) * split);
+	ma_set_meta(new_left, mt, 0, split);
+	l_mas.node = mt_mk_node(new_left, mt);
+
+	/* replace parent. */
+	offset = mte_parent_slot(mas->node);
+	mt = mas_parent_enum(&l_mas, l_mas.node);
+	parent = mas_pop_node(mas);
+	slots = ma_slots(parent, mt);
+	pivs = ma_pivots(parent, mt);
+	memcpy(parent, mte_to_node(eparent), sizeof(struct maple_node));
+	rcu_assign_pointer(slots[offset], mas->node);
+	rcu_assign_pointer(slots[offset - 1], l_mas.node);
+	pivs[offset - 1] = l_mas.max;
+	eparent = mt_mk_node(parent, mt);
+done:
+	gap = mas_leaf_max_gap(mas);
+	mte_set_gap(eparent, mte_parent_slot(mas->node), gap);
+	gap = mas_leaf_max_gap(&l_mas);
+	mte_set_gap(eparent, mte_parent_slot(l_mas.node), gap);
+	mas_ascend(mas);
+
+	if (in_rcu)
+		mas_replace(mas, false);
+
+	mas_update_gap(mas);
+}
+
+/*
+ * mas_split_final_node() - Split the final node in a subtree operation.
+ * @mast: the maple subtree state
+ * @mas: The maple state
+ * @height: The height of the tree in case it's a new root.
+ */
+static inline bool mas_split_final_node(struct maple_subtree_state *mast,
+					struct ma_state *mas, int height)
+{
+	struct maple_enode *ancestor;
+
+	if (mte_is_root(mas->node)) {
+		if (mt_is_alloc(mas->tree))
+			mast->bn->type = maple_arange_64;
+		else
+			mast->bn->type = maple_range_64;
+		mas->depth = height;
+	}
+	/*
+	 * Only a single node is used here, could be root.
+	 * The Big_node data should just fit in a single node.
+	 */
+	ancestor = mas_new_ma_node(mas, mast->bn);
+	mte_set_parent(mast->l->node, ancestor, mast->l->offset);
+	mte_set_parent(mast->r->node, ancestor, mast->r->offset);
+	mte_to_node(ancestor)->parent = mas_mn(mas)->parent;
+
+	mast->l->node = ancestor;
+	mab_mas_cp(mast->bn, 0, mt_slots[mast->bn->type] - 1, mast->l, true);
+	mas->offset = mast->bn->b_end - 1;
+	return true;
+}
+
+/*
+ * mast_fill_bnode() - Copy data into the big node in the subtree state
+ * @mast: The maple subtree state
+ * @mas: the maple state
+ * @skip: The number of entries to skip for new nodes insertion.
+ */
+static inline void mast_fill_bnode(struct maple_subtree_state *mast,
+					 struct ma_state *mas,
+					 unsigned char skip)
+{
+	bool cp = true;
+	struct maple_enode *old = mas->node;
+	unsigned char split;
+
+	memset(mast->bn->gap, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->gap));
+	memset(mast->bn->slot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->slot));
+	memset(mast->bn->pivot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->pivot));
+	mast->bn->b_end = 0;
+
+	if (mte_is_root(mas->node)) {
+		cp = false;
+	} else {
+		mas_ascend(mas);
+		mat_add(mast->free, old);
+		mas->offset = mte_parent_slot(mas->node);
+	}
+
+	if (cp && mast->l->offset)
+		mas_mab_cp(mas, 0, mast->l->offset - 1, mast->bn, 0);
+
+	split = mast->bn->b_end;
+	mab_set_b_end(mast->bn, mast->l, mast->l->node);
+	mast->r->offset = mast->bn->b_end;
+	mab_set_b_end(mast->bn, mast->r, mast->r->node);
+	if (mast->bn->pivot[mast->bn->b_end - 1] == mas->max)
+		cp = false;
+
+	if (cp)
+		mas_mab_cp(mas, split + skip, mt_slot_count(mas->node) - 1,
+			   mast->bn, mast->bn->b_end);
+
+	mast->bn->b_end--;
+	mast->bn->type = mte_node_type(mas->node);
+}
+
+/*
+ * mast_split_data() - Split the data in the subtree state big node into regular
+ * nodes.
+ * @mast: The maple subtree state
+ * @mas: The maple state
+ * @split: The location to split the big node
+ */
+static inline void mast_split_data(struct maple_subtree_state *mast,
+	   struct ma_state *mas, unsigned char split)
+{
+	unsigned char p_slot;
+
+	mab_mas_cp(mast->bn, 0, split, mast->l, true);
+	mte_set_pivot(mast->r->node, 0, mast->r->max);
+	mab_mas_cp(mast->bn, split + 1, mast->bn->b_end, mast->r, false);
+	mast->l->offset = mte_parent_slot(mas->node);
+	mast->l->max = mast->bn->pivot[split];
+	mast->r->min = mast->l->max + 1;
+	if (mte_is_leaf(mas->node))
+		return;
+
+	p_slot = mast->orig_l->offset;
+	mas_set_split_parent(mast->orig_l, mast->l->node, mast->r->node,
+			     &p_slot, split);
+	mas_set_split_parent(mast->orig_r, mast->l->node, mast->r->node,
+			     &p_slot, split);
+}
+
+/*
+ * mas_push_data() - Instead of splitting a node, it is beneficial to push the
+ * data to the right or left node if there is room.
+ * @mas: The maple state
+ * @height: The current height of the maple state
+ * @mast: The maple subtree state
+ * @left: Push left or not.
+ *
+ * Keeping the height of the tree low means faster lookups.
+ *
+ * Return: True if pushed, false otherwise.
+ */
+static inline bool mas_push_data(struct ma_state *mas, int height,
+				 struct maple_subtree_state *mast, bool left)
+{
+	unsigned char slot_total = mast->bn->b_end;
+	unsigned char end, space, split;
+
+	MA_STATE(tmp_mas, mas->tree, mas->index, mas->last);
+	tmp_mas = *mas;
+	tmp_mas.depth = mast->l->depth;
+
+	if (left && !mas_prev_sibling(&tmp_mas))
+		return false;
+	else if (!left && !mas_next_sibling(&tmp_mas))
+		return false;
+
+	end = mas_data_end(&tmp_mas);
+	slot_total += end;
+	space = 2 * mt_slot_count(mas->node) - 2;
+	/* -2 instead of -1 to ensure there isn't a triple split */
+	if (ma_is_leaf(mast->bn->type))
+		space--;
+
+	if (mas->max == ULONG_MAX)
+		space--;
+
+	if (slot_total >= space)
+		return false;
+
+	/* Get the data; Fill mast->bn */
+	mast->bn->b_end++;
+	if (left) {
+		mab_shift_right(mast->bn, end + 1);
+		mas_mab_cp(&tmp_mas, 0, end, mast->bn, 0);
+		mast->bn->b_end = slot_total + 1;
+	} else {
+		mas_mab_cp(&tmp_mas, 0, end, mast->bn, mast->bn->b_end);
+	}
+
+	/* Configure mast for splitting of mast->bn */
+	split = mt_slots[mast->bn->type] - 2;
+	if (left) {
+		/*  Switch mas to prev node  */
+		mat_add(mast->free, mas->node);
+		*mas = tmp_mas;
+		/* Start using mast->l for the left side. */
+		tmp_mas.node = mast->l->node;
+		*mast->l = tmp_mas;
+	} else {
+		mat_add(mast->free, tmp_mas.node);
+		tmp_mas.node = mast->r->node;
+		*mast->r = tmp_mas;
+		split = slot_total - split;
+	}
+	split = mab_no_null_split(mast->bn, split, mt_slots[mast->bn->type]);
+	/* Update parent slot for split calculation. */
+	if (left)
+		mast->orig_l->offset += end + 1;
+
+	mast_split_data(mast, mas, split);
+	mast_fill_bnode(mast, mas, 2);
+	mas_split_final_node(mast, mas, height + 1);
+	return true;
+}
+
+/*
+ * mas_split() - Split data that is too big for one node into two.
+ * @mas: The maple state
+ * @b_node: The maple big node
+ * Return: 1 on success, 0 on failure.
+ */
+static int mas_split(struct ma_state *mas, struct maple_big_node *b_node)
+{
+
+	struct maple_subtree_state mast;
+	int height = 0;
+	unsigned char mid_split, split = 0;
+
+	/*
+	 * Splitting is handled differently from any other B-tree; the Maple
+	 * Tree splits upwards.  Splitting up means that the split operation
+	 * occurs when the walk of the tree hits the leaves and not on the way
+	 * down.  The reason for splitting up is that it is impossible to know
+	 * how much space will be needed until the leaf is (or leaves are)
+	 * reached.  Since overwriting data is allowed and a range could
+	 * overwrite more than one range or result in changing one entry into 3
+	 * entries, it is impossible to know if a split is required until the
+	 * data is examined.
+	 *
+	 * Splitting is a balancing act between keeping allocations to a minimum
+	 * and avoiding a 'jitter' event where a tree is expanded to make room
+	 * for an entry followed by a contraction when the entry is removed.  To
+	 * accomplish the balance, there are empty slots remaining in both left
+	 * and right nodes after a split.
+	 */
+	MA_STATE(l_mas, mas->tree, mas->index, mas->last);
+	MA_STATE(r_mas, mas->tree, mas->index, mas->last);
+	MA_STATE(prev_l_mas, mas->tree, mas->index, mas->last);
+	MA_STATE(prev_r_mas, mas->tree, mas->index, mas->last);
+	MA_TOPIARY(mat, mas->tree);
+
+	trace_ma_op(__func__, mas);
+	mas->depth = mas_mt_height(mas);
+	/* Allocation failures will happen early. */
+	mas_node_count(mas, 1 + mas->depth * 2);
+	if (mas_is_err(mas))
+		return 0;
+
+	mast.l = &l_mas;
+	mast.r = &r_mas;
+	mast.orig_l = &prev_l_mas;
+	mast.orig_r = &prev_r_mas;
+	mast.free = &mat;
+	mast.bn = b_node;
+
+	while (height++ <= mas->depth) {
+		if (mt_slots[b_node->type] > b_node->b_end) {
+			mas_split_final_node(&mast, mas, height);
+			break;
+		}
+
+		l_mas = r_mas = *mas;
+		l_mas.node = mas_new_ma_node(mas, b_node);
+		r_mas.node = mas_new_ma_node(mas, b_node);
+		/*
+		 * Another way that 'jitter' is avoided is to terminate a split up early if the
+		 * left or right node has space to spare.  This is referred to as "pushing left"
+		 * or "pushing right" and is similar to the B* tree, except the nodes left or
+		 * right can rarely be reused due to RCU, but the ripple upwards is halted which
+		 * is a significant savings.
+		 */
+		/* Try to push left. */
+		if (mas_push_data(mas, height, &mast, true))
+			break;
+
+		/* Try to push right. */
+		if (mas_push_data(mas, height, &mast, false))
+			break;
+
+		split = mab_calc_split(mas, b_node, &mid_split, prev_l_mas.min);
+		mast_split_data(&mast, mas, split);
+		/*
+		 * Usually correct, mab_mas_cp in the above call overwrites
+		 * r->max.
+		 */
+		mast.r->max = mas->max;
+		mast_fill_bnode(&mast, mas, 1);
+		prev_l_mas = *mast.l;
+		prev_r_mas = *mast.r;
+	}
+
+	/* Set the original node as dead */
+	mat_add(mast.free, mas->node);
+	mas->node = l_mas.node;
+	mas_wmb_replace(mas, mast.free, NULL);
+	mtree_range_walk(mas);
+	return 1;
+}
+
+/*
+ * mas_reuse_node() - Reuse the node to store the data.
+ * @wr_mas: The maple write state
+ * @bn: The maple big node
+ * @end: The end of the data.
+ *
+ * Will always return false in RCU mode.
+ *
+ * Return: True if node was reused, false otherwise.
+ */
+static inline bool mas_reuse_node(struct ma_wr_state *wr_mas,
+			  struct maple_big_node *bn, unsigned char end)
+{
+	/* Need to be rcu safe. */
+	if (mt_in_rcu(wr_mas->mas->tree))
+		return false;
+
+	if (end > bn->b_end) {
+		int clear = mt_slots[wr_mas->type] - bn->b_end;
+
+		memset(wr_mas->slots + bn->b_end, 0, sizeof(void *) * clear--);
+		memset(wr_mas->pivots + bn->b_end, 0, sizeof(void *) * clear);
+	}
+	mab_mas_cp(bn, 0, bn->b_end, wr_mas->mas, false);
+	return true;
+}
+
+/*
+ * mas_commit_b_node() - Commit the big node into the tree.
+ * @wr_mas: The maple write state
+ * @b_node: The maple big node
+ * @end: The end of the data.
+ */
+static inline int mas_commit_b_node(struct ma_wr_state *wr_mas,
+			    struct maple_big_node *b_node, unsigned char end)
+{
+	struct maple_node *node;
+	unsigned char b_end = b_node->b_end;
+	enum maple_type b_type = b_node->type;
+
+	if ((b_end < mt_min_slots[b_type]) &&
+	    (!mte_is_root(wr_mas->mas->node)) &&
+	    (mas_mt_height(wr_mas->mas) > 1))
+		return mas_rebalance(wr_mas->mas, b_node);
+
+	if (b_end >= mt_slots[b_type])
+		return mas_split(wr_mas->mas, b_node);
+
+	if (mas_reuse_node(wr_mas, b_node, end))
+		goto reuse_node;
+
+	mas_node_count(wr_mas->mas, 1);
+	if (mas_is_err(wr_mas->mas))
+		return 0;
+
+	node = mas_pop_node(wr_mas->mas);
+	node->parent = mas_mn(wr_mas->mas)->parent;
+	wr_mas->mas->node = mt_mk_node(node, b_type);
+	mab_mas_cp(b_node, 0, b_end, wr_mas->mas, false);
+	mas_replace(wr_mas->mas, false);
+reuse_node:
+	mas_update_gap(wr_mas->mas);
+	return 1;
+}
+
+/*
+ * mas_root_expand() - Expand a root to a node
+ * @mas: The maple state
+ * @entry: The entry to store into the tree
+ */
+static inline int mas_root_expand(struct ma_state *mas, void *entry)
+{
+	void *contents = mas_root_locked(mas);
+	enum maple_type type = maple_leaf_64;
+	struct maple_node *node;
+	void __rcu **slots;
+	unsigned long *pivots;
+	int slot = 0;
+
+	mas_node_count(mas, 1);
+	if (unlikely(mas_is_err(mas)))
+		return 0;
+
+	node = mas_pop_node(mas);
+	pivots = ma_pivots(node, type);
+	slots = ma_slots(node, type);
+	node->parent = ma_parent_ptr(
+		      ((unsigned long)mas->tree | MA_ROOT_PARENT));
+	mas->node = mt_mk_node(node, type);
+
+	if (mas->index) {
+		if (contents) {
+			rcu_assign_pointer(slots[slot], contents);
+			if (likely(mas->index > 1))
+				slot++;
+		}
+		pivots[slot++] = mas->index - 1;
+	}
+
+	rcu_assign_pointer(slots[slot], entry);
+	mas->offset = slot;
+	pivots[slot] = mas->last;
+	if (mas->last != ULONG_MAX)
+		pivots[++slot] = ULONG_MAX;
+
+	mas->depth = 1;
+	mas_set_height(mas);
+	ma_set_meta(node, maple_leaf_64, 0, slot);
+	/* swap the new root into the tree */
+	rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
+	return slot;
+}
+
+static inline void mas_store_root(struct ma_state *mas, void *entry)
+{
+	if (likely((mas->last != 0) || (mas->index != 0)))
+		mas_root_expand(mas, entry);
+	else if (((unsigned long) (entry) & 3) == 2)
+		mas_root_expand(mas, entry);
+	else {
+		rcu_assign_pointer(mas->tree->ma_root, entry);
+		mas->node = MAS_START;
+	}
+}
+
+/*
+ * mas_is_span_wr() - Check if the write needs to be treated as a write that
+ * spans the node.
+ * @mas: The maple state
+ * @piv: The pivot value being written
+ * @type: The maple node type
+ * @entry: The data to write
+ *
+ * Spanning writes are writes that start in one node and end in another OR if
+ * the write of a %NULL will cause the node to end with a %NULL.
+ *
+ * Return: True if this is a spanning write, false otherwise.
+ */
+static bool mas_is_span_wr(struct ma_wr_state *wr_mas)
+{
+	unsigned long max;
+	unsigned long last = wr_mas->mas->last;
+	unsigned long piv = wr_mas->r_max;
+	enum maple_type type = wr_mas->type;
+	void *entry = wr_mas->entry;
+
+	/* Contained in this pivot */
+	if (piv > last)
+		return false;
+
+	max = wr_mas->mas->max;
+	if (unlikely(ma_is_leaf(type))) {
+		/* Fits in the node, but may span slots. */
+		if (last < max)
+			return false;
+
+		/* Writes to the end of the node but not null. */
+		if ((last == max) && entry)
+			return false;
+
+		/*
+		 * Writing ULONG_MAX is not a spanning write regardless of the
+		 * value being written as long as the range fits in the node.
+		 */
+		if ((last == ULONG_MAX) && (last == max))
+			return false;
+	} else if (piv == last) {
+		if (entry)
+			return false;
+
+		/* Detect spanning store wr walk */
+		if (last == ULONG_MAX)
+			return false;
+	}
+
+	trace_ma_write(__func__, wr_mas->mas, piv, entry);
+
+	return true;
+}
+
+static inline void mas_wr_walk_descend(struct ma_wr_state *wr_mas)
+{
+	wr_mas->type = mte_node_type(wr_mas->mas->node);
+	mas_wr_node_walk(wr_mas);
+	wr_mas->slots = ma_slots(wr_mas->node, wr_mas->type);
+}
+
+static inline void mas_wr_walk_traverse(struct ma_wr_state *wr_mas)
+{
+	wr_mas->mas->max = wr_mas->r_max;
+	wr_mas->mas->min = wr_mas->r_min;
+	wr_mas->mas->node = wr_mas->content;
+	wr_mas->mas->offset = 0;
+	wr_mas->mas->depth++;
+}
+/*
+ * mas_wr_walk() - Walk the tree for a write.
+ * @wr_mas: The maple write state
+ *
+ * Uses mas_slot_locked() and does not need to worry about dead nodes.
+ *
+ * Return: True if it's contained in a node, false on spanning write.
+ */
+static bool mas_wr_walk(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+
+	while (true) {
+		mas_wr_walk_descend(wr_mas);
+		if (unlikely(mas_is_span_wr(wr_mas)))
+			return false;
+
+		wr_mas->content = mas_slot_locked(mas, wr_mas->slots,
+						  mas->offset);
+		if (ma_is_leaf(wr_mas->type))
+			return true;
+
+		mas_wr_walk_traverse(wr_mas);
+	}
+
+	return true;
+}
+
+static bool mas_wr_walk_index(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+
+	while (true) {
+		mas_wr_walk_descend(wr_mas);
+		wr_mas->content = mas_slot_locked(mas, wr_mas->slots,
+						  mas->offset);
+		if (ma_is_leaf(wr_mas->type))
+			return true;
+		mas_wr_walk_traverse(wr_mas);
+
+	}
+	return true;
+}
+/*
+ * mas_extend_spanning_null() - Extend a store of a %NULL to include surrounding %NULLs.
+ * @l_wr_mas: The left maple write state
+ * @r_wr_mas: The right maple write state
+ */
+static inline void mas_extend_spanning_null(struct ma_wr_state *l_wr_mas,
+					    struct ma_wr_state *r_wr_mas)
+{
+	struct ma_state *r_mas = r_wr_mas->mas;
+	struct ma_state *l_mas = l_wr_mas->mas;
+	unsigned char l_slot;
+
+	l_slot = l_mas->offset;
+	if (!l_wr_mas->content)
+		l_mas->index = l_wr_mas->r_min;
+
+	if ((l_mas->index == l_wr_mas->r_min) &&
+		 (l_slot &&
+		  !mas_slot_locked(l_mas, l_wr_mas->slots, l_slot - 1))) {
+		if (l_slot > 1)
+			l_mas->index = l_wr_mas->pivots[l_slot - 2] + 1;
+		else
+			l_mas->index = l_mas->min;
+
+		l_mas->offset = l_slot - 1;
+	}
+
+	if (!r_wr_mas->content) {
+		if (r_mas->last < r_wr_mas->r_max)
+			r_mas->last = r_wr_mas->r_max;
+		r_mas->offset++;
+	} else if ((r_mas->last == r_wr_mas->r_max) &&
+	    (r_mas->last < r_mas->max) &&
+	    !mas_slot_locked(r_mas, r_wr_mas->slots, r_mas->offset + 1)) {
+		r_mas->last = mas_safe_pivot(r_mas, r_wr_mas->pivots,
+					     r_wr_mas->type, r_mas->offset + 1);
+		r_mas->offset++;
+	}
+}
+
+static inline void *mas_state_walk(struct ma_state *mas)
+{
+	void *entry;
+
+	entry = mas_start(mas);
+	if (mas_is_none(mas))
+		return NULL;
+
+	if (mas_is_ptr(mas))
+		return entry;
+
+	return mtree_range_walk(mas);
+}
+
+/*
+ * mtree_lookup_walk() - Internal quick lookup that does not keep maple state up
+ * to date.
+ *
+ * @mas: The maple state.
+ *
+ * Note: Leaves mas in undesirable state.
+ * Return: The entry for @mas->index or %NULL on dead node.
+ */
+static inline void *mtree_lookup_walk(struct ma_state *mas)
+{
+	unsigned long *pivots;
+	unsigned char offset;
+	struct maple_node *node;
+	struct maple_enode *next;
+	enum maple_type type;
+	void __rcu **slots;
+	unsigned char end;
+	unsigned long max;
+
+	next = mas->node;
+	max = ULONG_MAX;
+	do {
+		offset = 0;
+		node = mte_to_node(next);
+		type = mte_node_type(next);
+		pivots = ma_pivots(node, type);
+		end = ma_data_end(node, type, pivots, max);
+		if (unlikely(ma_dead_node(node)))
+			goto dead_node;
+		do {
+			if (pivots[offset] >= mas->index) {
+				max = pivots[offset];
+				break;
+			}
+		} while (++offset < end);
+
+		slots = ma_slots(node, type);
+		next = mt_slot(mas->tree, slots, offset);
+		if (unlikely(ma_dead_node(node)))
+			goto dead_node;
+	} while (!ma_is_leaf(type));
+
+	return (void *) next;
+
+dead_node:
+	mas_reset(mas);
+	return NULL;
+}
+
+/*
+ * mas_new_root() - Create a new root node that only contains the entry passed
+ * in.
+ * @mas: The maple state
+ * @entry: The entry to store.
+ *
+ * Only valid when the index == 0 and the last == ULONG_MAX
+ *
+ * Return 0 on error, 1 on success.
+ */
+static inline int mas_new_root(struct ma_state *mas, void *entry)
+{
+	struct maple_enode *root = mas_root_locked(mas);
+	enum maple_type type = maple_leaf_64;
+	struct maple_node *node;
+	void __rcu **slots;
+	unsigned long *pivots;
+
+	if (!entry && !mas->index && mas->last == ULONG_MAX) {
+		mas->depth = 0;
+		mas_set_height(mas);
+		rcu_assign_pointer(mas->tree->ma_root, entry);
+		mas->node = MAS_START;
+		goto done;
+	}
+
+	mas_node_count(mas, 1);
+	if (mas_is_err(mas))
+		return 0;
+
+	node = mas_pop_node(mas);
+	pivots = ma_pivots(node, type);
+	slots = ma_slots(node, type);
+	node->parent = ma_parent_ptr(
+		      ((unsigned long)mas->tree | MA_ROOT_PARENT));
+	mas->node = mt_mk_node(node, type);
+	rcu_assign_pointer(slots[0], entry);
+	pivots[0] = mas->last;
+	mas->depth = 1;
+	mas_set_height(mas);
+	rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
+
+done:
+	if (xa_is_node(root))
+		mte_destroy_walk(root, mas->tree);
+
+	return 1;
+}
+/*
+ * mas_wr_spanning_store() - Create a subtree with the store operation completed
+ * and new nodes where necessary, then place the sub-tree in the actual tree.
+ * Note that mas is expected to point to the node which caused the store to
+ * span.
+ * @wr_mas: The maple write state
+ *
+ * Return: 0 on error, positive on success.
+ */
+static inline int mas_wr_spanning_store(struct ma_wr_state *wr_mas)
+{
+	struct maple_subtree_state mast;
+	struct maple_big_node b_node;
+	struct ma_state *mas;
+	unsigned char height;
+
+	/* Left and Right side of spanning store */
+	MA_STATE(l_mas, NULL, 0, 0);
+	MA_STATE(r_mas, NULL, 0, 0);
+
+	MA_WR_STATE(r_wr_mas, &r_mas, wr_mas->entry);
+	MA_WR_STATE(l_wr_mas, &l_mas, wr_mas->entry);
+
+	/*
+	 * A store operation that spans multiple nodes is called a spanning
+	 * store and is handled early in the store call stack by the function
+	 * mas_is_span_wr().  When a spanning store is identified, the maple
+	 * state is duplicated.  The first maple state walks the left tree path
+	 * to ``index``, the duplicate walks the right tree path to ``last``.
+	 * The data in the two nodes are combined into a single node, two nodes,
+	 * or possibly three nodes (see the 3-way split above).  A ``NULL``
+	 * written to the last entry of a node is considered a spanning store as
+	 * a rebalance is required for the operation to complete and an overflow
+	 * of data may happen.
+	 */
+	mas = wr_mas->mas;
+	trace_ma_op(__func__, mas);
+
+	if (unlikely(!mas->index && mas->last == ULONG_MAX))
+		return mas_new_root(mas, wr_mas->entry);
+	/*
+	 * Node rebalancing may occur due to this store, so there may be three new
+	 * entries per level plus a new root.
+	 */
+	height = mas_mt_height(mas);
+	mas_node_count(mas, 1 + height * 3);
+	if (mas_is_err(mas))
+		return 0;
+
+	/*
+	 * Set up right side.  Need to get to the next offset after the spanning
+	 * store to ensure it's not NULL and to combine both the next node and
+	 * the node with the start together.
+	 */
+	r_mas = *mas;
+	/* Avoid overflow, walk to next slot in the tree. */
+	if (r_mas.last + 1)
+		r_mas.last++;
+
+	r_mas.index = r_mas.last;
+	mas_wr_walk_index(&r_wr_mas);
+	r_mas.last = r_mas.index = mas->last;
+
+	/* Set up left side. */
+	l_mas = *mas;
+	mas_wr_walk_index(&l_wr_mas);
+
+	if (!wr_mas->entry) {
+		mas_extend_spanning_null(&l_wr_mas, &r_wr_mas);
+		mas->offset = l_mas.offset;
+		mas->index = l_mas.index;
+		mas->last = l_mas.last = r_mas.last;
+	}
+
+	/* expanding NULLs may make this cover the entire range */
+	if (!l_mas.index && r_mas.last == ULONG_MAX) {
+		mas_set_range(mas, 0, ULONG_MAX);
+		return mas_new_root(mas, wr_mas->entry);
+	}
+
+	memset(&b_node, 0, sizeof(struct maple_big_node));
+	/* Copy l_mas and store the value in b_node. */
+	mas_store_b_node(&l_wr_mas, &b_node, l_wr_mas.node_end);
+	/* Copy r_mas into b_node. */
+	if (r_mas.offset <= r_wr_mas.node_end)
+		mas_mab_cp(&r_mas, r_mas.offset, r_wr_mas.node_end,
+			   &b_node, b_node.b_end + 1);
+	else
+		b_node.b_end++;
+
+	/* Stop spanning searches by searching for just index. */
+	l_mas.index = l_mas.last = mas->index;
+
+	mast.bn = &b_node;
+	mast.orig_l = &l_mas;
+	mast.orig_r = &r_mas;
+	/* Combine l_mas and r_mas and split them up evenly again. */
+	return mas_spanning_rebalance(mas, &mast, height + 1);
+}
+
+/*
+ * mas_wr_node_store() - Attempt to store the value in a node
+ * @wr_mas: The maple write state
+ *
+ * Attempts to reuse the node, but may allocate.
+ *
+ * Return: True if stored, false otherwise
+ */
+static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+	void __rcu **dst_slots;
+	unsigned long *dst_pivots;
+	unsigned char dst_offset;
+	unsigned char new_end = wr_mas->node_end;
+	unsigned char offset;
+	unsigned char node_slots = mt_slots[wr_mas->type];
+	struct maple_node reuse, *newnode;
+	unsigned char copy_size, max_piv = mt_pivots[wr_mas->type];
+	bool in_rcu = mt_in_rcu(mas->tree);
+
+	offset = mas->offset;
+	if (mas->last == wr_mas->r_max) {
+		/* runs right to the end of the node */
+		if (mas->last == mas->max)
+			new_end = offset;
+		/* don't copy this offset */
+		wr_mas->offset_end++;
+	} else if (mas->last < wr_mas->r_max) {
+		/* new range ends in this range */
+		if (unlikely(wr_mas->r_max == ULONG_MAX))
+			mas_bulk_rebalance(mas, wr_mas->node_end, wr_mas->type);
+
+		new_end++;
+	} else {
+		if (wr_mas->end_piv == mas->last)
+			wr_mas->offset_end++;
+
+		new_end -= wr_mas->offset_end - offset - 1;
+	}
+
+	/* new range starts within a range */
+	if (wr_mas->r_min < mas->index)
+		new_end++;
+
+	/* Not enough room */
+	if (new_end >= node_slots)
+		return false;
+
+	/* Not enough data. */
+	if (!mte_is_root(mas->node) && (new_end <= mt_min_slots[wr_mas->type]) &&
+	    !(mas->mas_flags & MA_STATE_BULK))
+		return false;
+
+	/* set up node. */
+	if (in_rcu) {
+		mas_node_count(mas, 1);
+		if (mas_is_err(mas))
+			return false;
+
+		newnode = mas_pop_node(mas);
+	} else {
+		memset(&reuse, 0, sizeof(struct maple_node));
+		newnode = &reuse;
+	}
+
+	newnode->parent = mas_mn(mas)->parent;
+	dst_pivots = ma_pivots(newnode, wr_mas->type);
+	dst_slots = ma_slots(newnode, wr_mas->type);
+	/* Copy from start to insert point */
+	memcpy(dst_pivots, wr_mas->pivots, sizeof(unsigned long) * (offset + 1));
+	memcpy(dst_slots, wr_mas->slots, sizeof(void *) * (offset + 1));
+	dst_offset = offset;
+
+	/* Handle insert of new range starting after old range */
+	if (wr_mas->r_min < mas->index) {
+		mas->offset++;
+		rcu_assign_pointer(dst_slots[dst_offset], wr_mas->content);
+		dst_pivots[dst_offset++] = mas->index - 1;
+	}
+
+	/* Store the new entry and range end. */
+	if (dst_offset < max_piv)
+		dst_pivots[dst_offset] = mas->last;
+	mas->offset = dst_offset;
+	rcu_assign_pointer(dst_slots[dst_offset], wr_mas->entry);
+
+	/*
+	 * this range wrote to the end of the node or it overwrote the rest of
+	 * the data
+	 */
+	if (wr_mas->offset_end > wr_mas->node_end || mas->last >= mas->max) {
+		new_end = dst_offset;
+		goto done;
+	}
+
+	dst_offset++;
+	/* Copy to the end of node if necessary. */
+	copy_size = wr_mas->node_end - wr_mas->offset_end + 1;
+	memcpy(dst_slots + dst_offset, wr_mas->slots + wr_mas->offset_end,
+	       sizeof(void *) * copy_size);
+	if (dst_offset < max_piv) {
+		if (copy_size > max_piv - dst_offset)
+			copy_size = max_piv - dst_offset;
+
+		memcpy(dst_pivots + dst_offset,
+		       wr_mas->pivots + wr_mas->offset_end,
+		       sizeof(unsigned long) * copy_size);
+	}
+
+	if ((wr_mas->node_end == node_slots - 1) && (new_end < node_slots - 1))
+		dst_pivots[new_end] = mas->max;
+
+done:
+	mas_leaf_set_meta(mas, newnode, dst_pivots, maple_leaf_64, new_end);
+	if (in_rcu) {
+		mte_set_node_dead(mas->node);
+		mas->node = mt_mk_node(newnode, wr_mas->type);
+		mas_replace(mas, false);
+	} else {
+		memcpy(wr_mas->node, newnode, sizeof(struct maple_node));
+	}
+	trace_ma_write(__func__, mas, 0, wr_mas->entry);
+	mas_update_gap(mas);
+	return true;
+}
+
+/*
+ * mas_wr_slot_store: Attempt to store a value in a slot.
+ * @wr_mas: the maple write state
+ *
+ * Return: True if stored, false otherwise
+ */
+static inline bool mas_wr_slot_store(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+	unsigned long lmax; /* Logical max. */
+	unsigned char offset = mas->offset;
+
+	if ((wr_mas->r_max > mas->last) && ((wr_mas->r_min != mas->index) ||
+				  (offset != wr_mas->node_end)))
+		return false;
+
+	if (offset == wr_mas->node_end - 1)
+		lmax = mas->max;
+	else
+		lmax = wr_mas->pivots[offset + 1];
+
+	/* going to overwrite too many slots. */
+	if (lmax < mas->last)
+		return false;
+
+	if (wr_mas->r_min == mas->index) {
+		/* overwriting two or more ranges with one. */
+		if (lmax == mas->last)
+			return false;
+
+		/* Overwriting all of offset and a portion of offset + 1. */
+		rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry);
+		wr_mas->pivots[offset] = mas->last;
+		goto done;
+	}
+
+	/* Doesn't end on the next range end. */
+	if (lmax != mas->last)
+		return false;
+
+	/* Overwriting a portion of offset and all of offset + 1 */
+	if ((offset + 1 < mt_pivots[wr_mas->type]) &&
+	    (wr_mas->entry || wr_mas->pivots[offset + 1]))
+		wr_mas->pivots[offset + 1] = mas->last;
+
+	rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
+	wr_mas->pivots[offset] = mas->index - 1;
+	mas->offset++; /* Keep mas accurate. */
+
+done:
+	trace_ma_write(__func__, mas, 0, wr_mas->entry);
+	mas_update_gap(mas);
+	return true;
+}
+
+static inline void mas_wr_end_piv(struct ma_wr_state *wr_mas)
+{
+	while ((wr_mas->offset_end < wr_mas->node_end) &&
+	       (wr_mas->mas->last > wr_mas->pivots[wr_mas->offset_end]))
+		wr_mas->offset_end++;
+
+	if (wr_mas->offset_end < wr_mas->node_end)
+		wr_mas->end_piv = wr_mas->pivots[wr_mas->offset_end];
+	else
+		wr_mas->end_piv = wr_mas->mas->max;
+}
+
+static inline void mas_wr_extend_null(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+
+	if (mas->last < wr_mas->end_piv && !wr_mas->slots[wr_mas->offset_end])
+		mas->last = wr_mas->end_piv;
+
+	/* Check next slot(s) if we are overwriting the end */
+	if ((mas->last == wr_mas->end_piv) &&
+	    (wr_mas->node_end != wr_mas->offset_end) &&
+	    !wr_mas->slots[wr_mas->offset_end + 1]) {
+		wr_mas->offset_end++;
+		if (wr_mas->offset_end == wr_mas->node_end)
+			mas->last = mas->max;
+		else
+			mas->last = wr_mas->pivots[wr_mas->offset_end];
+		wr_mas->end_piv = mas->last;
+	}
+
+	if (!wr_mas->content) {
+		/* If this one is null, the next and prev are not */
+		mas->index = wr_mas->r_min;
+	} else {
+		/* Check prev slot if we are overwriting the start */
+		if (mas->index == wr_mas->r_min && mas->offset &&
+		    !wr_mas->slots[mas->offset - 1]) {
+			mas->offset--;
+			wr_mas->r_min = mas->index =
+				mas_safe_min(mas, wr_mas->pivots, mas->offset);
+			wr_mas->r_max = wr_mas->pivots[mas->offset];
+		}
+	}
+}
+
+static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
+{
+	unsigned char end = wr_mas->node_end;
+	unsigned char new_end = end + 1;
+	struct ma_state *mas = wr_mas->mas;
+	unsigned char node_pivots = mt_pivots[wr_mas->type];
+
+	if (mt_in_rcu(mas->tree))
+		return false;
+
+	if ((mas->index != wr_mas->r_min) && (mas->last == wr_mas->r_max)) {
+		if (new_end < node_pivots)
+			wr_mas->pivots[new_end] = wr_mas->pivots[end];
+
+		if (new_end < node_pivots)
+			ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
+
+		rcu_assign_pointer(wr_mas->slots[new_end], wr_mas->entry);
+		mas->offset = new_end;
+		wr_mas->pivots[end] = mas->index - 1;
+
+		return true;
+	}
+
+	if ((mas->index == wr_mas->r_min) && (mas->last < wr_mas->r_max)) {
+		if (new_end < node_pivots)
+			wr_mas->pivots[new_end] = wr_mas->pivots[end];
+
+		rcu_assign_pointer(wr_mas->slots[new_end], wr_mas->content);
+		if (new_end < node_pivots)
+			ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
+
+		wr_mas->pivots[end] = mas->last;
+		rcu_assign_pointer(wr_mas->slots[end], wr_mas->entry);
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * mas_wr_bnode() - Slow path for a modification.
+ * @wr_mas: The write maple state
+ *
+ * This is where split, rebalance end up.
+ */
+static void mas_wr_bnode(struct ma_wr_state *wr_mas)
+{
+	struct maple_big_node b_node;
+
+	trace_ma_write(__func__, wr_mas->mas, 0, wr_mas->entry);
+	memset(&b_node, 0, sizeof(struct maple_big_node));
+	mas_store_b_node(wr_mas, &b_node, wr_mas->offset_end);
+	mas_commit_b_node(wr_mas, &b_node, wr_mas->node_end);
+}
+
+static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
+{
+	unsigned char node_slots;
+	unsigned char node_size;
+	struct ma_state *mas = wr_mas->mas;
+
+	/* Direct replacement */
+	if (wr_mas->r_min == mas->index && wr_mas->r_max == mas->last) {
+		rcu_assign_pointer(wr_mas->slots[mas->offset], wr_mas->entry);
+		if (!!wr_mas->entry ^ !!wr_mas->content)
+			mas_update_gap(mas);
+		return;
+	}
+
+	/* Attempt to append */
+	node_slots = mt_slots[wr_mas->type];
+	node_size = wr_mas->node_end - wr_mas->offset_end + mas->offset + 2;
+	if (mas->max == ULONG_MAX)
+		node_size++;
+
+	/* slot and node store will not fit, go to the slow path */
+	if (unlikely(node_size >= node_slots))
+		goto slow_path;
+
+	if (wr_mas->entry && (wr_mas->node_end < node_slots - 1) &&
+	    (mas->offset == wr_mas->node_end) && mas_wr_append(wr_mas)) {
+		if (!wr_mas->content || !wr_mas->entry)
+			mas_update_gap(mas);
+		return;
+	}
+
+	if ((wr_mas->offset_end - mas->offset <= 1) && mas_wr_slot_store(wr_mas))
+		return;
+	else if (mas_wr_node_store(wr_mas))
+		return;
+
+	if (mas_is_err(mas))
+		return;
+
+slow_path:
+	mas_wr_bnode(wr_mas);
+}
+
+/*
+ * mas_wr_store_entry() - Internal call to store a value
+ * @mas: The maple state
+ * @entry: The entry to store.
+ *
+ * Return: The contents that was stored at the index.
+ */
+static inline void *mas_wr_store_entry(struct ma_wr_state *wr_mas)
+{
+	struct ma_state *mas = wr_mas->mas;
+
+	wr_mas->content = mas_start(mas);
+	if (mas_is_none(mas) || mas_is_ptr(mas)) {
+		mas_store_root(mas, wr_mas->entry);
+		return wr_mas->content;
+	}
+
+	if (unlikely(!mas_wr_walk(wr_mas))) {
+		mas_wr_spanning_store(wr_mas);
+		return wr_mas->content;
+	}
+
+	/* At this point, we are at the leaf node that needs to be altered. */
+	mas_wr_end_piv(wr_mas);
+
+	if (!wr_mas->entry)
+		mas_wr_extend_null(wr_mas);
+
+	/* New root for a single pointer */
+	if (unlikely(!mas->index && mas->last == ULONG_MAX)) {
+		mas_new_root(mas, wr_mas->entry);
+		return wr_mas->content;
+	}
+
+	mas_wr_modify(wr_mas);
+	return wr_mas->content;
+}
+
+/**
+ * mas_insert() - Internal call to insert a value
+ * @mas: The maple state
+ * @entry: The entry to store
+ *
+ * Return: %NULL or the contents that already exists at the requested index
+ * otherwise.  The maple state needs to be checked for error conditions.
+ */
+static inline void *mas_insert(struct ma_state *mas, void *entry)
+{
+	MA_WR_STATE(wr_mas, mas, entry);
+
+	/*
+	 * Inserting a new range inserts either 0, 1, or 2 pivots within the
+	 * tree.  If the insert fits exactly into an existing gap with a value
+	 * of NULL, then the slot only needs to be written with the new value.
+	 * If the range being inserted is adjacent to another range, then only a
+	 * single pivot needs to be inserted (as well as writing the entry).  If
+	 * the new range is within a gap but does not touch any other ranges,
+	 * then two pivots need to be inserted: the start - 1, and the end.  As
+	 * usual, the entry must be written.  Most operations require a new node
+	 * to be allocated and replace an existing node to ensure RCU safety,
+	 * when in RCU mode.  The exception to requiring a newly allocated node
+	 * is when inserting at the end of a node (appending).  When done
+	 * carefully, appending can reuse the node in place.
+	 */
+	wr_mas.content = mas_start(mas);
+	if (wr_mas.content)
+		goto exists;
+
+	if (mas_is_none(mas) || mas_is_ptr(mas)) {
+		mas_store_root(mas, entry);
+		return NULL;
+	}
+
+	/* spanning writes always overwrite something */
+	if (!mas_wr_walk(&wr_mas))
+		goto exists;
+
+	/* At this point, we are at the leaf node that needs to be altered. */
+	wr_mas.offset_end = mas->offset;
+	wr_mas.end_piv = wr_mas.r_max;
+
+	if (wr_mas.content || (mas->last > wr_mas.r_max))
+		goto exists;
+
+	if (!entry)
+		return NULL;
+
+	mas_wr_modify(&wr_mas);
+	return wr_mas.content;
+
+exists:
+	mas_set_err(mas, -EEXIST);
+	return wr_mas.content;
+
+}
+
+/*
+ * mas_prev_node() - Find the prev non-null entry at the same level in the
+ * tree.  The prev value will be mas->node[mas->offset] or MAS_NONE.
+ * @mas: The maple state
+ * @min: The lower limit to search
+ *
+ * The prev node value will be mas->node[mas->offset] or MAS_NONE.
+ * Return: 1 if the node is dead, 0 otherwise.
+ */
+static inline int mas_prev_node(struct ma_state *mas, unsigned long min)
+{
+	enum maple_type mt;
+	int offset, level;
+	void __rcu **slots;
+	struct maple_node *node;
+	struct maple_enode *enode;
+	unsigned long *pivots;
+
+	if (mas_is_none(mas))
+		return 0;
+
+	level = 0;
+	do {
+		node = mas_mn(mas);
+		if (ma_is_root(node))
+			goto no_entry;
+
+		/* Walk up. */
+		if (unlikely(mas_ascend(mas)))
+			return 1;
+		offset = mas->offset;
+		level++;
+	} while (!offset);
+
+	offset--;
+	mt = mte_node_type(mas->node);
+	node = mas_mn(mas);
+	slots = ma_slots(node, mt);
+	pivots = ma_pivots(node, mt);
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	mas->max = pivots[offset];
+	if (offset)
+		mas->min = pivots[offset - 1] + 1;
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	if (mas->max < min)
+		goto no_entry_min;
+
+	while (level > 1) {
+		level--;
+		enode = mas_slot(mas, slots, offset);
+		if (unlikely(ma_dead_node(node)))
+			return 1;
+
+		mas->node = enode;
+		mt = mte_node_type(mas->node);
+		node = mas_mn(mas);
+		slots = ma_slots(node, mt);
+		pivots = ma_pivots(node, mt);
+		offset = ma_data_end(node, mt, pivots, mas->max);
+		if (unlikely(ma_dead_node(node)))
+			return 1;
+
+		if (offset)
+			mas->min = pivots[offset - 1] + 1;
+
+		if (offset < mt_pivots[mt])
+			mas->max = pivots[offset];
+
+		if (mas->max < min)
+			goto no_entry;
+	}
+
+	mas->node = mas_slot(mas, slots, offset);
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	mas->offset = mas_data_end(mas);
+	if (unlikely(mte_dead_node(mas->node)))
+		return 1;
+
+	return 0;
+
+no_entry_min:
+	mas->offset = offset;
+	if (offset)
+		mas->min = pivots[offset - 1] + 1;
+no_entry:
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	mas->node = MAS_NONE;
+	return 0;
+}
+
+/*
+ * mas_next_node() - Get the next node at the same level in the tree.
+ * @mas: The maple state
+ * @max: The maximum pivot value to check.
+ *
+ * The next value will be mas->node[mas->offset] or MAS_NONE.
+ * Return: 1 on dead node, 0 otherwise.
+ */
+static inline int mas_next_node(struct ma_state *mas, struct maple_node *node,
+				unsigned long max)
+{
+	unsigned long min, pivot;
+	unsigned long *pivots;
+	struct maple_enode *enode;
+	int level = 0;
+	unsigned char offset;
+	unsigned char node_end;
+	enum maple_type mt;
+	void __rcu **slots;
+
+	if (mas->max >= max)
+		goto no_entry;
+
+	level = 0;
+	do {
+		if (ma_is_root(node))
+			goto no_entry;
+
+		min = mas->max + 1;
+		if (min > max)
+			goto no_entry;
+
+		if (unlikely(mas_ascend(mas)))
+			return 1;
+
+		offset = mas->offset;
+		level++;
+		node = mas_mn(mas);
+		mt = mte_node_type(mas->node);
+		pivots = ma_pivots(node, mt);
+		node_end = ma_data_end(node, mt, pivots, mas->max);
+		if (unlikely(ma_dead_node(node)))
+			return 1;
+
+	} while (unlikely(offset == node_end));
+
+	slots = ma_slots(node, mt);
+	pivot = mas_safe_pivot(mas, pivots, ++offset, mt);
+	while (unlikely(level > 1)) {
+		/* Descend, if necessary */
+		enode = mas_slot(mas, slots, offset);
+		if (unlikely(ma_dead_node(node)))
+			return 1;
+
+		mas->node = enode;
+		level--;
+		node = mas_mn(mas);
+		mt = mte_node_type(mas->node);
+		slots = ma_slots(node, mt);
+		pivots = ma_pivots(node, mt);
+		if (unlikely(ma_dead_node(node)))
+			return 1;
+
+		offset = 0;
+		pivot = pivots[0];
+	}
+
+	enode = mas_slot(mas, slots, offset);
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	mas->node = enode;
+	mas->min = min;
+	mas->max = pivot;
+	return 0;
+
+no_entry:
+	if (unlikely(ma_dead_node(node)))
+		return 1;
+
+	mas->node = MAS_NONE;
+	return 0;
+}
+
+/*
+ * mas_next_nentry() - Get the next node entry
+ * @mas: The maple state
+ * @max: The maximum value to check
+ * @*range_start: Pointer to store the start of the range.
+ *
+ * Sets @mas->offset to the offset of the next node entry, @mas->last to the
+ * pivot of the entry.
+ *
+ * Return: The next entry, %NULL otherwise
+ */
+static inline void *mas_next_nentry(struct ma_state *mas,
+	    struct maple_node *node, unsigned long max, enum maple_type type)
+{
+	unsigned char count;
+	unsigned long pivot;
+	unsigned long *pivots;
+	void __rcu **slots;
+	void *entry;
+
+	if (mas->last == mas->max) {
+		mas->index = mas->max;
+		return NULL;
+	}
+
+	slots = ma_slots(node, type);
+	pivots = ma_pivots(node, type);
+	count = ma_data_end(node, type, pivots, mas->max);
+	if (unlikely(ma_dead_node(node)))
+		return NULL;
+
+	mas->index = mas_safe_min(mas, pivots, mas->offset);
+	if (unlikely(ma_dead_node(node)))
+		return NULL;
+
+	if (mas->index > max)
+		return NULL;
+
+	if (mas->offset > count)
+		return NULL;
+
+	while (mas->offset < count) {
+		pivot = pivots[mas->offset];
+		entry = mas_slot(mas, slots, mas->offset);
+		if (ma_dead_node(node))
+			return NULL;
+
+		if (entry)
+			goto found;
+
+		if (pivot >= max)
+			return NULL;
+
+		mas->index = pivot + 1;
+		mas->offset++;
+	}
+
+	if (mas->index > mas->max) {
+		mas->index = mas->last;
+		return NULL;
+	}
+
+	pivot = mas_safe_pivot(mas, pivots, mas->offset, type);
+	entry = mas_slot(mas, slots, mas->offset);
+	if (ma_dead_node(node))
+		return NULL;
+
+	if (!pivot)
+		return NULL;
+
+	if (!entry)
+		return NULL;
+
+found:
+	mas->last = pivot;
+	return entry;
+}
+
+static inline void mas_rewalk(struct ma_state *mas, unsigned long index)
+{
+
+retry:
+	mas_set(mas, index);
+	mas_state_walk(mas);
+	if (mas_is_start(mas))
+		goto retry;
+
+	return;
+
+}
+
+/*
+ * mas_next_entry() - Internal function to get the next entry.
+ * @mas: The maple state
+ * @limit: The maximum range start.
+ *
+ * Set the @mas->node to the next entry and the range_start to
+ * the beginning value for the entry.  Does not check beyond @limit.
+ * Sets @mas->index and @mas->last to the limit if it is hit.
+ * Restarts on dead nodes.
+ *
+ * Return: the next entry or %NULL.
+ */
+static inline void *mas_next_entry(struct ma_state *mas, unsigned long limit)
+{
+	void *entry = NULL;
+	struct maple_enode *prev_node;
+	struct maple_node *node;
+	unsigned char offset;
+	unsigned long last;
+	enum maple_type mt;
+
+	if (mas->index > limit) {
+		mas->index = mas->last = limit;
+		mas_pause(mas);
+		return NULL;
+	}
+	last = mas->last;
+retry:
+	offset = mas->offset;
+	prev_node = mas->node;
+	node = mas_mn(mas);
+	mt = mte_node_type(mas->node);
+	mas->offset++;
+	if (unlikely(mas->offset >= mt_slots[mt])) {
+		mas->offset = mt_slots[mt] - 1;
+		goto next_node;
+	}
+
+	while (!mas_is_none(mas)) {
+		entry = mas_next_nentry(mas, node, limit, mt);
+		if (unlikely(ma_dead_node(node))) {
+			mas_rewalk(mas, last);
+			goto retry;
+		}
+
+		if (likely(entry))
+			return entry;
+
+		if (unlikely((mas->index > limit)))
+			break;
+
+next_node:
+		prev_node = mas->node;
+		offset = mas->offset;
+		if (unlikely(mas_next_node(mas, node, limit))) {
+			mas_rewalk(mas, last);
+			goto retry;
+		}
+		mas->offset = 0;
+		node = mas_mn(mas);
+		mt = mte_node_type(mas->node);
+	}
+
+	mas->index = mas->last = limit;
+	mas->offset = offset;
+	mas->node = prev_node;
+	return NULL;
+}
+
+/*
+ * mas_prev_nentry() - Get the previous node entry.
+ * @mas: The maple state.
+ * @limit: The lower limit to check for a value.
+ *
+ * Return: the entry, %NULL otherwise.
+ */
+static inline void *mas_prev_nentry(struct ma_state *mas, unsigned long limit,
+				    unsigned long index)
+{
+	unsigned long pivot, min;
+	unsigned char offset;
+	struct maple_node *mn;
+	enum maple_type mt;
+	unsigned long *pivots;
+	void __rcu **slots;
+	void *entry;
+
+retry:
+	if (!mas->offset)
+		return NULL;
+
+	mn = mas_mn(mas);
+	mt = mte_node_type(mas->node);
+	offset = mas->offset - 1;
+	if (offset >= mt_slots[mt])
+		offset = mt_slots[mt] - 1;
+
+	slots = ma_slots(mn, mt);
+	pivots = ma_pivots(mn, mt);
+	if (unlikely(ma_dead_node(mn))) {
+		mas_rewalk(mas, index);
+		goto retry;
+	}
+
+	if (offset == mt_pivots[mt])
+		pivot = mas->max;
+	else
+		pivot = pivots[offset];
+
+	if (unlikely(ma_dead_node(mn))) {
+		mas_rewalk(mas, index);
+		goto retry;
+	}
+
+	while (offset && ((!mas_slot(mas, slots, offset) && pivot >= limit) ||
+	       !pivot))
+		pivot = pivots[--offset];
+
+	min = mas_safe_min(mas, pivots, offset);
+	entry = mas_slot(mas, slots, offset);
+	if (unlikely(ma_dead_node(mn))) {
+		mas_rewalk(mas, index);
+		goto retry;
+	}
+
+	if (likely(entry)) {
+		mas->offset = offset;
+		mas->last = pivot;
+		mas->index = min;
+	}
+	return entry;
+}
+
+static inline void *mas_prev_entry(struct ma_state *mas, unsigned long min)
+{
+	void *entry;
+
+	if (mas->index < min) {
+		mas->index = mas->last = min;
+		mas->node = MAS_NONE;
+		return NULL;
+	}
+retry:
+	while (likely(!mas_is_none(mas))) {
+		entry = mas_prev_nentry(mas, min, mas->index);
+		if (unlikely(mas->last < min))
+			goto not_found;
+
+		if (likely(entry))
+			return entry;
+
+		if (unlikely(mas_prev_node(mas, min))) {
+			mas_rewalk(mas, mas->index);
+			goto retry;
+		}
+
+		mas->offset++;
+	}
+
+	mas->offset--;
+not_found:
+	mas->index = mas->last = min;
+	return NULL;
+}
+
+/*
+ * mas_rev_awalk() - Internal function.  Reverse allocation walk.  Find the
+ * highest gap address of a given size in a given node and descend.
+ * @mas: The maple state
+ * @size: The needed size.
+ *
+ * Return: True if found in a leaf, false otherwise.
+ *
+ */
+static bool mas_rev_awalk(struct ma_state *mas, unsigned long size,
+		unsigned long *gap_min, unsigned long *gap_max)
+{
+	enum maple_type type = mte_node_type(mas->node);
+	struct maple_node *node = mas_mn(mas);
+	unsigned long *pivots, *gaps;
+	void __rcu **slots;
+	unsigned long gap = 0;
+	unsigned long max, min;
+	unsigned char offset;
+
+	if (unlikely(mas_is_err(mas)))
+		return true;
+
+	if (ma_is_dense(type)) {
+		/* dense nodes. */
+		mas->offset = (unsigned char)(mas->index - mas->min);
+		return true;
+	}
+
+	pivots = ma_pivots(node, type);
+	slots = ma_slots(node, type);
+	gaps = ma_gaps(node, type);
+	offset = mas->offset;
+	min = mas_safe_min(mas, pivots, offset);
+	/* Skip out of bounds. */
+	while (mas->last < min)
+		min = mas_safe_min(mas, pivots, --offset);
+
+	max = mas_safe_pivot(mas, pivots, offset, type);
+	while (mas->index <= max) {
+		gap = 0;
+		if (gaps)
+			gap = gaps[offset];
+		else if (!mas_slot(mas, slots, offset))
+			gap = max - min + 1;
+
+		if (gap) {
+			if ((size <= gap) && (size <= mas->last - min + 1))
+				break;
+
+			if (!gaps) {
+				/* Skip the next slot, it cannot be a gap. */
+				if (offset < 2)
+					goto ascend;
+
+				offset -= 2;
+				max = pivots[offset];
+				min = mas_safe_min(mas, pivots, offset);
+				continue;
+			}
+		}
+
+		if (!offset)
+			goto ascend;
+
+		offset--;
+		max = min - 1;
+		min = mas_safe_min(mas, pivots, offset);
+	}
+
+	if (unlikely((mas->index > max) || (size - 1 > max - mas->index)))
+		goto no_space;
+
+	if (unlikely(ma_is_leaf(type))) {
+		mas->offset = offset;
+		*gap_min = min;
+		*gap_max = min + gap - 1;
+		return true;
+	}
+
+	/* descend, only happens under lock. */
+	mas->node = mas_slot(mas, slots, offset);
+	mas->min = min;
+	mas->max = max;
+	mas->offset = mas_data_end(mas);
+	return false;
+
+ascend:
+	if (!mte_is_root(mas->node))
+		return false;
+
+no_space:
+	mas_set_err(mas, -EBUSY);
+	return false;
+}
+
+static inline bool mas_anode_descend(struct ma_state *mas, unsigned long size)
+{
+	enum maple_type type = mte_node_type(mas->node);
+	unsigned long pivot, min, gap = 0;
+	unsigned char offset, data_end;
+	unsigned long *gaps, *pivots;
+	void __rcu **slots;
+	struct maple_node *node;
+	bool found = false;
+
+	if (ma_is_dense(type)) {
+		mas->offset = (unsigned char)(mas->index - mas->min);
+		return true;
+	}
+
+	node = mas_mn(mas);
+	pivots = ma_pivots(node, type);
+	slots = ma_slots(node, type);
+	gaps = ma_gaps(node, type);
+	offset = mas->offset;
+	min = mas_safe_min(mas, pivots, offset);
+	data_end = ma_data_end(node, type, pivots, mas->max);
+	for (; offset <= data_end; offset++) {
+		pivot = mas_logical_pivot(mas, pivots, offset, type);
+
+		/* Not within lower bounds */
+		if (mas->index > pivot)
+			goto next_slot;
+
+		if (gaps)
+			gap = gaps[offset];
+		else if (!mas_slot(mas, slots, offset))
+			gap = min(pivot, mas->last) - max(mas->index, min) + 1;
+		else
+			goto next_slot;
+
+		if (gap >= size) {
+			if (ma_is_leaf(type)) {
+				found = true;
+				goto done;
+			}
+			if (mas->index <= pivot) {
+				mas->node = mas_slot(mas, slots, offset);
+				mas->min = min;
+				mas->max = pivot;
+				offset = 0;
+				break;
+			}
+		}
+next_slot:
+		min = pivot + 1;
+		if (mas->last <= pivot) {
+			mas_set_err(mas, -EBUSY);
+			return true;
+		}
+	}
+
+	if (mte_is_root(mas->node))
+		found = true;
+done:
+	mas->offset = offset;
+	return found;
+}
+
+/**
+ * mas_walk() - Search for @mas->index in the tree.
+ * @mas: The maple state.
+ *
+ * mas->index and mas->last will be set to the range if there is a value.  If
+ * mas->node is MAS_NONE, reset to MAS_START.
+ *
+ * Return: the entry at the location or %NULL.
+ */
+void *mas_walk(struct ma_state *mas)
+{
+	void *entry;
+
+retry:
+	entry = mas_state_walk(mas);
+	if (mas_is_start(mas))
+		goto retry;
+
+	if (mas_is_ptr(mas)) {
+		if (!mas->index) {
+			mas->last = 0;
+		} else {
+			mas->index = 1;
+			mas->last = ULONG_MAX;
+		}
+		return entry;
+	}
+
+	if (mas_is_none(mas)) {
+		mas->index = 0;
+		mas->last = ULONG_MAX;
+	}
+
+	return entry;
+}
+EXPORT_SYMBOL_GPL(mas_walk);
+
+static inline bool mas_rewind_node(struct ma_state *mas)
+{
+	unsigned char slot;
+
+	do {
+		if (mte_is_root(mas->node)) {
+			slot = mas->offset;
+			if (!slot)
+				return false;
+		} else {
+			mas_ascend(mas);
+			slot = mas->offset;
+		}
+	} while (!slot);
+
+	mas->offset = --slot;
+	return true;
+}
+
+/*
+ * mas_skip_node() - Internal function.  Skip over a node.
+ * @mas: The maple state.
+ *
+ * Return: true if there is another node, false otherwise.
+ */
+static inline bool mas_skip_node(struct ma_state *mas)
+{
+	if (mas_is_err(mas))
+		return false;
+
+	do {
+		if (mte_is_root(mas->node)) {
+			if (mas->offset >= mas_data_end(mas)) {
+				mas_set_err(mas, -EBUSY);
+				return false;
+			}
+		} else {
+			mas_ascend(mas);
+		}
+	} while (mas->offset >= mas_data_end(mas));
+
+	mas->offset++;
+	return true;
+}
+
+/*
+ * mas_awalk() - Allocation walk.  Search from low address to high, for a gap of
+ * @size
+ * @mas: The maple state
+ * @size: The size of the gap required
+ *
+ * Search between @mas->index and @mas->last for a gap of @size.
+ */
+static inline void mas_awalk(struct ma_state *mas, unsigned long size)
+{
+	struct maple_enode *last = NULL;
+
+	/*
+	 * There are 4 options:
+	 * go to child (descend)
+	 * go back to parent (ascend)
+	 * no gap found. (return, slot == MAPLE_NODE_SLOTS)
+	 * found the gap. (return, slot != MAPLE_NODE_SLOTS)
+	 */
+	while (!mas_is_err(mas) && !mas_anode_descend(mas, size)) {
+		if (last == mas->node)
+			mas_skip_node(mas);
+		else
+			last = mas->node;
+	}
+}
+
+/*
+ * mas_fill_gap() - Fill a located gap with @entry.
+ * @mas: The maple state
+ * @entry: The value to store
+ * @slot: The offset into the node to store the @entry
+ * @size: The size of the entry
+ * @index: The start location
+ */
+static inline void mas_fill_gap(struct ma_state *mas, void *entry,
+		unsigned char slot, unsigned long size, unsigned long *index)
+{
+	MA_WR_STATE(wr_mas, mas, entry);
+	unsigned char pslot = mte_parent_slot(mas->node);
+	struct maple_enode *mn = mas->node;
+	unsigned long *pivots;
+	enum maple_type ptype;
+	/*
+	 * mas->index is the start address for the search
+	 *  which may no longer be needed.
+	 * mas->last is the end address for the search
+	 */
+
+	*index = mas->index;
+	mas->last = mas->index + size - 1;
+
+	/*
+	 * It is possible that using mas->max and mas->min to correctly
+	 * calculate the index and last will cause an issue in the gap
+	 * calculation, so fix the ma_state here
+	 */
+	mas_ascend(mas);
+	ptype = mte_node_type(mas->node);
+	pivots = ma_pivots(mas_mn(mas), ptype);
+	mas->max = mas_safe_pivot(mas, pivots, pslot, ptype);
+	mas->min = mas_safe_min(mas, pivots, pslot);
+	mas->node = mn;
+	mas->offset = slot;
+	mas_wr_store_entry(&wr_mas);
+}
+
+/*
+ * mas_sparse_area() - Internal function.  Return upper or lower limit when
+ * searching for a gap in an empty tree.
+ * @mas: The maple state
+ * @min: the minimum range
+ * @max: The maximum range
+ * @size: The size of the gap
+ * @fwd: Searching forward or back
+ */
+static inline void mas_sparse_area(struct ma_state *mas, unsigned long min,
+				unsigned long max, unsigned long size, bool fwd)
+{
+	unsigned long start = 0;
+
+	if (!unlikely(mas_is_none(mas)))
+		start++;
+	/* mas_is_ptr */
+
+	if (start < min)
+		start = min;
+
+	if (fwd) {
+		mas->index = start;
+		mas->last = start + size - 1;
+		return;
+	}
+
+	mas->index = max;
+}
+
+/*
+ * mas_empty_area() - Get the lowest address within the range that is
+ * sufficient for the size requested.
+ * @mas: The maple state
+ * @min: The lowest value of the range
+ * @max: The highest value of the range
+ * @size: The size needed
+ */
+int mas_empty_area(struct ma_state *mas, unsigned long min,
+		unsigned long max, unsigned long size)
+{
+	unsigned char offset;
+	unsigned long *pivots;
+	enum maple_type mt;
+
+	if (min >= max)
+		return -EINVAL;
+
+	if (mas_is_start(mas))
+		mas_start(mas);
+	else if (mas->offset >= 2)
+		mas->offset -= 2;
+	else if (!mas_skip_node(mas))
+		return -EBUSY;
+
+	/* Empty set */
+	if (mas_is_none(mas) || mas_is_ptr(mas)) {
+		mas_sparse_area(mas, min, max, size, true);
+		return 0;
+	}
+
+	/* The start of the window can only be within these values */
+	mas->index = min;
+	mas->last = max;
+	mas_awalk(mas, size);
+
+	if (unlikely(mas_is_err(mas)))
+		return xa_err(mas->node);
+
+	offset = mas->offset;
+	if (unlikely(offset == MAPLE_NODE_SLOTS))
+		return -EBUSY;
+
+	mt = mte_node_type(mas->node);
+	pivots = ma_pivots(mas_mn(mas), mt);
+	min = mas_safe_min(mas, pivots, offset);
+	if (mas->index < min)
+		mas->index = min;
+	mas->last = mas->index + size - 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mas_empty_area);
+
+/*
+ * mas_empty_area_rev() - Get the highest address within the range that is
+ * sufficient for the size requested.
+ * @mas: The maple state
+ * @min: The lowest value of the range
+ * @max: The highest value of the range
+ * @size: The size needed
+ */
+int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
+		unsigned long max, unsigned long size)
+{
+	struct maple_enode *last = mas->node;
+
+	if (min >= max)
+		return -EINVAL;
+
+	if (mas_is_start(mas)) {
+		mas_start(mas);
+		mas->offset = mas_data_end(mas);
+	} else if (mas->offset >= 2) {
+		mas->offset -= 2;
+	} else if (!mas_rewind_node(mas)) {
+		return -EBUSY;
+	}
+
+	/* Empty set. */
+	if (mas_is_none(mas) || mas_is_ptr(mas)) {
+		mas_sparse_area(mas, min, max, size, false);
+		return 0;
+	}
+
+	/* The start of the window can only be within these values. */
+	mas->index = min;
+	mas->last = max;
+
+	while (!mas_rev_awalk(mas, size, &min, &max)) {
+		if (last == mas->node) {
+			if (!mas_rewind_node(mas))
+				return -EBUSY;
+		} else {
+			last = mas->node;
+		}
+	}
+
+	if (mas_is_err(mas))
+		return xa_err(mas->node);
+
+	if (unlikely(mas->offset == MAPLE_NODE_SLOTS))
+		return -EBUSY;
+
+	/* Trim the upper limit to the max. */
+	if (max <= mas->last)
+		mas->last = max;
+
+	mas->index = mas->last - size + 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mas_empty_area_rev);
+
+static inline int mas_alloc(struct ma_state *mas, void *entry,
+		unsigned long size, unsigned long *index)
+{
+	unsigned long min;
+
+	mas_start(mas);
+	if (mas_is_none(mas) || mas_is_ptr(mas)) {
+		mas_root_expand(mas, entry);
+		if (mas_is_err(mas))
+			return xa_err(mas->node);
+
+		if (!mas->index)
+			return mte_pivot(mas->node, 0);
+		return mte_pivot(mas->node, 1);
+	}
+
+	/* Must be walking a tree. */
+	mas_awalk(mas, size);
+	if (mas_is_err(mas))
+		return xa_err(mas->node);
+
+	if (mas->offset == MAPLE_NODE_SLOTS)
+		goto no_gap;
+
+	/*
+	 * At this point, mas->node points to the right node and we have an
+	 * offset that has a sufficient gap.
+	 */
+	min = mas->min;
+	if (mas->offset)
+		min = mte_pivot(mas->node, mas->offset - 1) + 1;
+
+	if (mas->index < min)
+		mas->index = min;
+
+	mas_fill_gap(mas, entry, mas->offset, size, index);
+	return 0;
+
+no_gap:
+	return -EBUSY;
+}
+
+static inline int mas_rev_alloc(struct ma_state *mas, unsigned long min,
+				unsigned long max, void *entry,
+				unsigned long size, unsigned long *index)
+{
+	int ret = 0;
+
+	ret = mas_empty_area_rev(mas, min, max, size);
+	if (ret)
+		return ret;
+
+	if (mas_is_err(mas))
+		return xa_err(mas->node);
+
+	if (mas->offset == MAPLE_NODE_SLOTS)
+		goto no_gap;
+
+	mas_fill_gap(mas, entry, mas->offset, size, index);
+	return 0;
+
+no_gap:
+	return -EBUSY;
+}
+
+/*
+ * mte_dead_leaves() - Mark all leaves of a node as dead.
+ * @mas: The maple state
+ * @slots: Pointer to the slot array
+ * @type: The maple node type
+ *
+ * Must hold the write lock.
+ *
+ * Return: The number of leaves marked as dead.
+ */
+static inline
+unsigned char mte_dead_leaves(struct maple_enode *enode, struct maple_tree *mt,
+			      void __rcu **slots)
+{
+	struct maple_node *node;
+	enum maple_type type;
+	void *entry;
+	int offset;
+
+	for (offset = 0; offset < mt_slot_count(enode); offset++) {
+		entry = mt_slot(mt, slots, offset);
+		type = mte_node_type(entry);
+		node = mte_to_node(entry);
+		/* Use both node and type to catch LE & BE metadata */
+		if (!node || !type)
+			break;
+
+		mte_set_node_dead(entry);
+		node->type = type;
+		rcu_assign_pointer(slots[offset], node);
+	}
+
+	return offset;
+}
+
+/**
+ * mte_dead_walk() - Walk down a dead tree to just before the leaves
+ * @enode: The maple encoded node
+ * @offset: The starting offset
+ *
+ * Note: This can only be used from the RCU callback context.
+ */
+static void __rcu **mte_dead_walk(struct maple_enode **enode, unsigned char offset)
+{
+	struct maple_node *node, *next;
+	void __rcu **slots = NULL;
+
+	next = mte_to_node(*enode);
+	do {
+		*enode = ma_enode_ptr(next);
+		node = mte_to_node(*enode);
+		slots = ma_slots(node, node->type);
+		next = rcu_dereference_protected(slots[offset],
+					lock_is_held(&rcu_callback_map));
+		offset = 0;
+	} while (!ma_is_leaf(next->type));
+
+	return slots;
+}
+
+/**
+ * mt_free_walk() - Walk & free a tree in the RCU callback context
+ * @head: The RCU head that's within the node.
+ *
+ * Note: This can only be used from the RCU callback context.
+ */
+static void mt_free_walk(struct rcu_head *head)
+{
+	void __rcu **slots;
+	struct maple_node *node, *start;
+	struct maple_enode *enode;
+	unsigned char offset;
+	enum maple_type type;
+
+	node = container_of(head, struct maple_node, rcu);
+
+	if (ma_is_leaf(node->type))
+		goto free_leaf;
+
+	start = node;
+	enode = mt_mk_node(node, node->type);
+	slots = mte_dead_walk(&enode, 0);
+	node = mte_to_node(enode);
+	do {
+		mt_free_bulk(node->slot_len, slots);
+		offset = node->parent_slot + 1;
+		enode = node->piv_parent;
+		if (mte_to_node(enode) == node)
+			goto free_leaf;
+
+		type = mte_node_type(enode);
+		slots = ma_slots(mte_to_node(enode), type);
+		if ((offset < mt_slots[type]) &&
+		    rcu_dereference_protected(slots[offset],
+					      lock_is_held(&rcu_callback_map)))
+			slots = mte_dead_walk(&enode, offset);
+		node = mte_to_node(enode);
+	} while ((node != start) || (node->slot_len < offset));
+
+	slots = ma_slots(node, node->type);
+	mt_free_bulk(node->slot_len, slots);
+
+free_leaf:
+	mt_free_rcu(&node->rcu);
+}
+
+static inline void __rcu **mte_destroy_descend(struct maple_enode **enode,
+	struct maple_tree *mt, struct maple_enode *prev, unsigned char offset)
+{
+	struct maple_node *node;
+	struct maple_enode *next = *enode;
+	void __rcu **slots = NULL;
+	enum maple_type type;
+	unsigned char next_offset = 0;
+
+	do {
+		*enode = next;
+		node = mte_to_node(*enode);
+		type = mte_node_type(*enode);
+		slots = ma_slots(node, type);
+		next = mt_slot_locked(mt, slots, next_offset);
+		if ((mte_dead_node(next)))
+			next = mt_slot_locked(mt, slots, ++next_offset);
+
+		mte_set_node_dead(*enode);
+		node->type = type;
+		node->piv_parent = prev;
+		node->parent_slot = offset;
+		offset = next_offset;
+		next_offset = 0;
+		prev = *enode;
+	} while (!mte_is_leaf(next));
+
+	return slots;
+}
+
+static void mt_destroy_walk(struct maple_enode *enode, struct maple_tree *mt,
+			    bool free)
+{
+	void __rcu **slots;
+	struct maple_node *node = mte_to_node(enode);
+	struct maple_enode *start;
+
+	if (mte_is_leaf(enode)) {
+		node->type = mte_node_type(enode);
+		goto free_leaf;
+	}
+
+	start = enode;
+	slots = mte_destroy_descend(&enode, mt, start, 0);
+	node = mte_to_node(enode); // Updated in the above call.
+	do {
+		enum maple_type type;
+		unsigned char offset;
+		struct maple_enode *parent, *tmp;
+
+		node->slot_len = mte_dead_leaves(enode, mt, slots);
+		if (free)
+			mt_free_bulk(node->slot_len, slots);
+		offset = node->parent_slot + 1;
+		enode = node->piv_parent;
+		if (mte_to_node(enode) == node)
+			goto free_leaf;
+
+		type = mte_node_type(enode);
+		slots = ma_slots(mte_to_node(enode), type);
+		if (offset >= mt_slots[type])
+			goto next;
+
+		tmp = mt_slot_locked(mt, slots, offset);
+		if (mte_node_type(tmp) && mte_to_node(tmp)) {
+			parent = enode;
+			enode = tmp;
+			slots = mte_destroy_descend(&enode, mt, parent, offset);
+		}
+next:
+		node = mte_to_node(enode);
+	} while (start != enode);
+
+	node = mte_to_node(enode);
+	node->slot_len = mte_dead_leaves(enode, mt, slots);
+	if (free)
+		mt_free_bulk(node->slot_len, slots);
+
+free_leaf:
+	if (free)
+		mt_free_rcu(&node->rcu);
+	else
+		mt_clear_meta(mt, node, node->type);
+}
+
+/*
+ * mte_destroy_walk() - Free a tree or sub-tree.
+ * @enode - the encoded maple node (maple_enode) to start
+ * @mn - the tree to free - needed for node types.
+ *
+ * Must hold the write lock.
+ */
+static inline void mte_destroy_walk(struct maple_enode *enode,
+				    struct maple_tree *mt)
+{
+	struct maple_node *node = mte_to_node(enode);
+
+	if (mt_in_rcu(mt)) {
+		mt_destroy_walk(enode, mt, false);
+		call_rcu(&node->rcu, mt_free_walk);
+	} else {
+		mt_destroy_walk(enode, mt, true);
+	}
+}
+
+static void mas_wr_store_setup(struct ma_wr_state *wr_mas)
+{
+	if (unlikely(mas_is_paused(wr_mas->mas)))
+		mas_reset(wr_mas->mas);
+
+	if (!mas_is_start(wr_mas->mas)) {
+		if (mas_is_none(wr_mas->mas)) {
+			mas_reset(wr_mas->mas);
+		} else {
+			wr_mas->r_max = wr_mas->mas->max;
+			wr_mas->type = mte_node_type(wr_mas->mas->node);
+			if (mas_is_span_wr(wr_mas))
+				mas_reset(wr_mas->mas);
+		}
+	}
+
+}
+
+/* Interface */
+
+/**
+ * mas_store() - Store an @entry.
+ * @mas: The maple state.
+ * @entry: The entry to store.
+ *
+ * The @mas->index and @mas->last is used to set the range for the @entry.
+ * Note: The @mas should have pre-allocated entries to ensure there is memory to
+ * store the entry.  Please see mas_expected_entries()/mas_destroy() for more details.
+ *
+ * Return: the first entry between mas->index and mas->last or %NULL.
+ */
+void *mas_store(struct ma_state *mas, void *entry)
+{
+	MA_WR_STATE(wr_mas, mas, entry);
+
+	trace_ma_write(__func__, mas, 0, entry);
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+	if (mas->index > mas->last)
+		pr_err("Error %lu > %lu %p\n", mas->index, mas->last, entry);
+	MT_BUG_ON(mas->tree, mas->index > mas->last);
+	if (mas->index > mas->last) {
+		mas_set_err(mas, -EINVAL);
+		return NULL;
+	}
+
+#endif
+
+	/*
+	 * Storing is the same operation as insert with the added caveat that it
+	 * can overwrite entries.  Although this seems simple enough, one may
+	 * want to examine what happens if a single store operation was to
+	 * overwrite multiple entries within a self-balancing B-Tree.
+	 */
+	mas_wr_store_setup(&wr_mas);
+	mas_wr_store_entry(&wr_mas);
+	return wr_mas.content;
+}
+EXPORT_SYMBOL_GPL(mas_store);
+
+/**
+ * mas_store_gfp() - Store a value into the tree.
+ * @mas: The maple state
+ * @entry: The entry to store
+ * @gfp: The GFP_FLAGS to use for allocations if necessary.
+ *
+ * Return: 0 on success, -EINVAL on invalid request, -ENOMEM if memory could not
+ * be allocated.
+ */
+int mas_store_gfp(struct ma_state *mas, void *entry, gfp_t gfp)
+{
+	MA_WR_STATE(wr_mas, mas, entry);
+
+	mas_wr_store_setup(&wr_mas);
+	trace_ma_write(__func__, mas, 0, entry);
+retry:
+	mas_wr_store_entry(&wr_mas);
+	if (unlikely(mas_nomem(mas, gfp)))
+		goto retry;
+
+	if (unlikely(mas_is_err(mas)))
+		return xa_err(mas->node);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mas_store_gfp);
+
+/**
+ * mas_store_prealloc() - Store a value into the tree using memory
+ * preallocated in the maple state.
+ * @mas: The maple state
+ * @entry: The entry to store.
+ */
+void mas_store_prealloc(struct ma_state *mas, void *entry)
+{
+	MA_WR_STATE(wr_mas, mas, entry);
+
+	mas_wr_store_setup(&wr_mas);
+	trace_ma_write(__func__, mas, 0, entry);
+	mas_wr_store_entry(&wr_mas);
+	BUG_ON(mas_is_err(mas));
+	mas_destroy(mas);
+}
+EXPORT_SYMBOL_GPL(mas_store_prealloc);
+
+/**
+ * mas_preallocate() - Preallocate enough nodes for a store operation
+ * @mas: The maple state
+ * @entry: The entry that will be stored
+ * @gfp: The GFP_FLAGS to use for allocations.
+ *
+ * Return: 0 on success, -ENOMEM if memory could not be allocated.
+ */
+int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
+{
+	int ret;
+
+	mas_node_count_gfp(mas, 1 + mas_mt_height(mas) * 3, gfp);
+	mas->mas_flags |= MA_STATE_PREALLOC;
+	if (likely(!mas_is_err(mas)))
+		return 0;
+
+	mas_set_alloc_req(mas, 0);
+	ret = xa_err(mas->node);
+	mas_reset(mas);
+	mas_destroy(mas);
+	mas_reset(mas);
+	return ret;
+}
+
+/*
+ * mas_destroy() - destroy a maple state.
+ * @mas: The maple state
+ *
+ * Upon completion, check the left-most node and rebalance against the node to
+ * the right if necessary.  Frees any allocated nodes associated with this maple
+ * state.
+ */
+void mas_destroy(struct ma_state *mas)
+{
+	struct maple_alloc *node;
+	unsigned long total;
+
+	/*
+	 * When using mas_for_each() to insert an expected number of elements,
+	 * it is possible that the number inserted is less than the expected
+	 * number.  To fix an invalid final node, a check is performed here to
+	 * rebalance the previous node with the final node.
+	 */
+	if (mas->mas_flags & MA_STATE_REBALANCE) {
+		unsigned char end;
+
+		if (mas_is_start(mas))
+			mas_start(mas);
+
+		mtree_range_walk(mas);
+		end = mas_data_end(mas) + 1;
+		if (end < mt_min_slot_count(mas->node) - 1)
+			mas_destroy_rebalance(mas, end);
+
+		mas->mas_flags &= ~MA_STATE_REBALANCE;
+	}
+	mas->mas_flags &= ~(MA_STATE_BULK|MA_STATE_PREALLOC);
+
+	total = mas_allocated(mas);
+	while (total) {
+		node = mas->alloc;
+		mas->alloc = node->slot[0];
+		if (node->node_count > 1) {
+			size_t count = node->node_count - 1;
+
+			mt_free_bulk(count, (void __rcu **)&node->slot[1]);
+			total -= count;
+		}
+		kmem_cache_free(maple_node_cache, node);
+		total--;
+	}
+
+	mas->alloc = NULL;
+}
+EXPORT_SYMBOL_GPL(mas_destroy);
+
+/*
+ * mas_expected_entries() - Set the expected number of entries that will be inserted.
+ * @mas: The maple state
+ * @nr_entries: The number of expected entries.
+ *
+ * This will attempt to pre-allocate enough nodes to store the expected number
+ * of entries.  The allocations will occur using the bulk allocator interface
+ * for speed.  Please call mas_destroy() on the @mas after inserting the entries
+ * to ensure any unused nodes are freed.
+ *
+ * Return: 0 on success, -ENOMEM if memory could not be allocated.
+ */
+int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries)
+{
+	int nonleaf_cap = MAPLE_ARANGE64_SLOTS - 2;
+	struct maple_enode *enode = mas->node;
+	int nr_nodes;
+	int ret;
+
+	/*
+	 * Sometimes it is necessary to duplicate a tree to a new tree, such as
+	 * forking a process and duplicating the VMAs from one tree to a new
+	 * tree.  When such a situation arises, it is known that the new tree is
+	 * not going to be used until the entire tree is populated.  For
+	 * performance reasons, it is best to use a bulk load with RCU disabled.
+	 * This allows for optimistic splitting that favours the left and reuse
+	 * of nodes during the operation.
+	 */
+
+	/* Optimize splitting for bulk insert in-order */
+	mas->mas_flags |= MA_STATE_BULK;
+
+	/*
+	 * Avoid overflow, assume a gap between each entry and a trailing null.
+	 * If this is wrong, it just means allocation can happen during
+	 * insertion of entries.
+	 */
+	nr_nodes = max(nr_entries, nr_entries * 2 + 1);
+	if (!mt_is_alloc(mas->tree))
+		nonleaf_cap = MAPLE_RANGE64_SLOTS - 2;
+
+	/* Leaves; reduce slots to keep space for expansion */
+	nr_nodes = DIV_ROUND_UP(nr_nodes, MAPLE_RANGE64_SLOTS - 2);
+	/* Internal nodes */
+	nr_nodes += DIV_ROUND_UP(nr_nodes, nonleaf_cap);
+	/* Add working room for split (2 nodes) + new parents */
+	mas_node_count_gfp(mas, nr_nodes + 3, GFP_KERNEL);
+
+	/* Detect if allocations run out */
+	mas->mas_flags |= MA_STATE_PREALLOC;
+
+	if (!mas_is_err(mas))
+		return 0;
+
+	ret = xa_err(mas->node);
+	mas->node = enode;
+	mas_destroy(mas);
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(mas_expected_entries);
+
+/**
+ * mas_next() - Get the next entry.
+ * @mas: The maple state
+ * @max: The maximum index to check.
+ *
+ * Returns the next entry after @mas->index.
+ * Must hold rcu_read_lock or the write lock.
+ * Can return the zero entry.
+ *
+ * Return: The next entry or %NULL
+ */
+void *mas_next(struct ma_state *mas, unsigned long max)
+{
+	if (mas_is_none(mas) || mas_is_paused(mas))
+		mas->node = MAS_START;
+
+	if (mas_is_start(mas))
+		mas_walk(mas); /* Retries on dead nodes handled by mas_walk */
+
+	if (mas_is_ptr(mas)) {
+		if (!mas->index) {
+			mas->index = 1;
+			mas->last = ULONG_MAX;
+		}
+		return NULL;
+	}
+
+	if (mas->last == ULONG_MAX)
+		return NULL;
+
+	/* Retries on dead nodes handled by mas_next_entry */
+	return mas_next_entry(mas, max);
+}
+EXPORT_SYMBOL_GPL(mas_next);
+
+/**
+ * mt_next() - get the next value in the maple tree
+ * @mt: The maple tree
+ * @index: The start index
+ * @max: The maximum index to check
+ *
+ * Return: The entry at @index or higher, or %NULL if nothing is found.
+ */
+void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max)
+{
+	void *entry = NULL;
+	MA_STATE(mas, mt, index, index);
+
+	rcu_read_lock();
+	entry = mas_next(&mas, max);
+	rcu_read_unlock();
+	return entry;
+}
+EXPORT_SYMBOL_GPL(mt_next);
+
+/**
+ * mas_prev() - Get the previous entry
+ * @mas: The maple state
+ * @min: The minimum value to check.
+ *
+ * Must hold rcu_read_lock or the write lock.
+ * Will reset mas to MAS_START if the node is MAS_NONE.  Will stop on not
+ * searchable nodes.
+ *
+ * Return: the previous value or %NULL.
+ */
+void *mas_prev(struct ma_state *mas, unsigned long min)
+{
+	if (!mas->index) {
+		/* Nothing comes before 0 */
+		mas->last = 0;
+		mas->node = MAS_NONE;
+		return NULL;
+	}
+
+	if (unlikely(mas_is_ptr(mas)))
+		return NULL;
+
+	if (mas_is_none(mas) || mas_is_paused(mas))
+		mas->node = MAS_START;
+
+	if (mas_is_start(mas)) {
+		mas_walk(mas);
+		if (!mas->index)
+			return NULL;
+	}
+
+	if (mas_is_ptr(mas)) {
+		if (!mas->index) {
+			mas->last = 0;
+			return NULL;
+		}
+
+		mas->index = mas->last = 0;
+		return mas_root_locked(mas);
+	}
+	return mas_prev_entry(mas, min);
+}
+EXPORT_SYMBOL_GPL(mas_prev);
+
+/**
+ * mt_prev() - get the previous value in the maple tree
+ * @mt: The maple tree
+ * @index: The start index
+ * @min: The minimum index to check
+ *
+ * Return: The entry at @index or lower, or %NULL if nothing is found.
+ */
+void *mt_prev(struct maple_tree *mt, unsigned long index, unsigned long min)
+{
+	void *entry = NULL;
+	MA_STATE(mas, mt, index, index);
+
+	rcu_read_lock();
+	entry = mas_prev(&mas, min);
+	rcu_read_unlock();
+	return entry;
+}
+EXPORT_SYMBOL_GPL(mt_prev);
+
+/**
+ * mas_pause() - Pause a mas_find/mas_for_each to drop the lock.
+ * @mas: The maple state to pause
+ *
+ * Some users need to pause a walk and drop the lock they're holding in
+ * order to yield to a higher priority thread or carry out an operation
+ * on an entry.  Those users should call this function before they drop
+ * the lock.  It resets the @mas to be suitable for the next iteration
+ * of the loop after the user has reacquired the lock.  If most entries
+ * found during a walk require you to call mas_pause(), the mt_for_each()
+ * iterator may be more appropriate.
+ *
+ */
+void mas_pause(struct ma_state *mas)
+{
+	mas->node = MAS_PAUSE;
+}
+EXPORT_SYMBOL_GPL(mas_pause);
+
+/**
+ * mas_find() - On the first call, find the entry at or after mas->index up to
+ * %max.  Otherwise, find the entry after mas->index.
+ * @mas: The maple state
+ * @max: The maximum value to check.
+ *
+ * Must hold rcu_read_lock or the write lock.
+ * If an entry exists, last and index are updated accordingly.
+ * May set @mas->node to MAS_NONE.
+ *
+ * Return: The entry or %NULL.
+ */
+void *mas_find(struct ma_state *mas, unsigned long max)
+{
+	if (unlikely(mas_is_paused(mas))) {
+		if (unlikely(mas->last == ULONG_MAX)) {
+			mas->node = MAS_NONE;
+			return NULL;
+		}
+		mas->node = MAS_START;
+		mas->index = ++mas->last;
+	}
+
+	if (unlikely(mas_is_none(mas)))
+		mas->node = MAS_START;
+
+	if (unlikely(mas_is_start(mas))) {
+		/* First run or continue */
+		void *entry;
+
+		if (mas->index > max)
+			return NULL;
+
+		entry = mas_walk(mas);
+		if (entry)
+			return entry;
+	}
+
+	if (unlikely(!mas_searchable(mas)))
+		return NULL;
+
+	/* Retries on dead nodes handled by mas_next_entry */
+	return mas_next_entry(mas, max);
+}
+EXPORT_SYMBOL_GPL(mas_find);
+
+/**
+ * mas_find_rev: On the first call, find the first non-null entry at or below
+ * mas->index down to %min.  Otherwise find the first non-null entry below
+ * mas->index down to %min.
+ * @mas: The maple state
+ * @min: The minimum value to check.
+ *
+ * Must hold rcu_read_lock or the write lock.
+ * If an entry exists, last and index are updated accordingly.
+ * May set @mas->node to MAS_NONE.
+ *
+ * Return: The entry or %NULL.
+ */
+void *mas_find_rev(struct ma_state *mas, unsigned long min)
+{
+	if (unlikely(mas_is_paused(mas))) {
+		if (unlikely(mas->last == ULONG_MAX)) {
+			mas->node = MAS_NONE;
+			return NULL;
+		}
+		mas->node = MAS_START;
+		mas->last = --mas->index;
+	}
+
+	if (unlikely(mas_is_start(mas))) {
+		/* First run or continue */
+		void *entry;
+
+		if (mas->index < min)
+			return NULL;
+
+		entry = mas_walk(mas);
+		if (entry)
+			return entry;
+	}
+
+	if (unlikely(!mas_searchable(mas)))
+		return NULL;
+
+	if (mas->index < min)
+		return NULL;
+
+	/* Retries on dead nodes handled by mas_next_entry */
+	return mas_prev_entry(mas, min);
+}
+EXPORT_SYMBOL_GPL(mas_find_rev);
+
+/**
+ * mas_erase() - Find the range in which index resides and erase the entire
+ * range.
+ * @mas: The maple state
+ *
+ * Must hold the write lock.
+ * Searches for @mas->index, sets @mas->index and @mas->last to the range and
+ * erases that range.
+ *
+ * Return: the entry that was erased or %NULL, @mas->index and @mas->last are updated.
+ */
+void *mas_erase(struct ma_state *mas)
+{
+	void *entry;
+	MA_WR_STATE(wr_mas, mas, NULL);
+
+	if (mas_is_none(mas) || mas_is_paused(mas))
+		mas->node = MAS_START;
+
+	/* Retry unnecessary when holding the write lock. */
+	entry = mas_state_walk(mas);
+	if (!entry)
+		return NULL;
+
+write_retry:
+	/* Must reset to ensure spanning writes of last slot are detected */
+	mas_reset(mas);
+	mas_wr_store_setup(&wr_mas);
+	mas_wr_store_entry(&wr_mas);
+	if (mas_nomem(mas, GFP_KERNEL))
+		goto write_retry;
+
+	return entry;
+}
+EXPORT_SYMBOL_GPL(mas_erase);
+
+/**
+ * mas_nomem() - Check if there was an error allocating and do the allocation
+ * if necessary If there are allocations, then free them.
+ * @mas: The maple state
+ * @gfp: The GFP_FLAGS to use for allocations
+ * Return: true on allocation, false otherwise.
+ */
+bool mas_nomem(struct ma_state *mas, gfp_t gfp)
+	__must_hold(mas->tree->lock)
+{
+	if (likely(mas->node != MA_ERROR(-ENOMEM))) {
+		mas_destroy(mas);
+		return false;
+	}
+
+	if (gfpflags_allow_blocking(gfp) && !mt_external_lock(mas->tree)) {
+		mtree_unlock(mas->tree);
+		mas_alloc_nodes(mas, gfp);
+		mtree_lock(mas->tree);
+	} else {
+		mas_alloc_nodes(mas, gfp);
+	}
+
+	if (!mas_allocated(mas))
+		return false;
+
+	mas->node = MAS_START;
+	return true;
+}
+
+void __init maple_tree_init(void)
+{
+	maple_node_cache = kmem_cache_create("maple_node",
+			sizeof(struct maple_node), sizeof(struct maple_node),
+			SLAB_PANIC, NULL);
+}
+
+/**
+ * mtree_load() - Load a value stored in a maple tree
+ * @mt: The maple tree
+ * @index: The index to load
+ *
+ * Return: the entry or %NULL
+ */
+void *mtree_load(struct maple_tree *mt, unsigned long index)
+{
+	MA_STATE(mas, mt, index, index);
+	void *entry;
+
+	trace_ma_read(__func__, &mas);
+	rcu_read_lock();
+retry:
+	entry = mas_start(&mas);
+	if (unlikely(mas_is_none(&mas)))
+		goto unlock;
+
+	if (unlikely(mas_is_ptr(&mas))) {
+		if (index)
+			entry = NULL;
+
+		goto unlock;
+	}
+
+	entry = mtree_lookup_walk(&mas);
+	if (!entry && unlikely(mas_is_start(&mas)))
+		goto retry;
+unlock:
+	rcu_read_unlock();
+	if (xa_is_zero(entry))
+		return NULL;
+
+	return entry;
+}
+EXPORT_SYMBOL(mtree_load);
+
+/**
+ * mtree_store_range() - Store an entry at a given range.
+ * @mt: The maple tree
+ * @index: The start of the range
+ * @last: The end of the range
+ * @entry: The entry to store
+ * @gfp: The GFP_FLAGS to use for allocations
+ *
+ * Return: 0 on success, -EINVAL on invalid request, -ENOMEM if memory could not
+ * be allocated.
+ */
+int mtree_store_range(struct maple_tree *mt, unsigned long index,
+		unsigned long last, void *entry, gfp_t gfp)
+{
+	MA_STATE(mas, mt, index, last);
+	MA_WR_STATE(wr_mas, &mas, entry);
+
+	trace_ma_write(__func__, &mas, 0, entry);
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
+		return -EINVAL;
+
+	if (index > last)
+		return -EINVAL;
+
+	mtree_lock(mt);
+retry:
+	mas_wr_store_entry(&wr_mas);
+	if (mas_nomem(&mas, gfp))
+		goto retry;
+
+	mtree_unlock(mt);
+	if (mas_is_err(&mas))
+		return xa_err(mas.node);
+
+	return 0;
+}
+EXPORT_SYMBOL(mtree_store_range);
+
+/**
+ * mtree_store() - Store an entry at a given index.
+ * @mt: The maple tree
+ * @index: The index to store the value
+ * @entry: The entry to store
+ * @gfp: The GFP_FLAGS to use for allocations
+ *
+ * Return: 0 on success, -EINVAL on invalid request, -ENOMEM if memory could not
+ * be allocated.
+ */
+int mtree_store(struct maple_tree *mt, unsigned long index, void *entry,
+		 gfp_t gfp)
+{
+	return mtree_store_range(mt, index, index, entry, gfp);
+}
+EXPORT_SYMBOL(mtree_store);
+
+/**
+ * mtree_insert_range() - Insert an entry at a give range if there is no value.
+ * @mt: The maple tree
+ * @first: The start of the range
+ * @last: The end of the range
+ * @entry: The entry to store
+ * @gfp: The GFP_FLAGS to use for allocations.
+ *
+ * Return: 0 on success, -EEXISTS if the range is occupied, -EINVAL on invalid
+ * request, -ENOMEM if memory could not be allocated.
+ */
+int mtree_insert_range(struct maple_tree *mt, unsigned long first,
+		unsigned long last, void *entry, gfp_t gfp)
+{
+	MA_STATE(ms, mt, first, last);
+
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
+		return -EINVAL;
+
+	if (first > last)
+		return -EINVAL;
+
+	mtree_lock(mt);
+retry:
+	mas_insert(&ms, entry);
+	if (mas_nomem(&ms, gfp))
+		goto retry;
+
+	mtree_unlock(mt);
+	if (mas_is_err(&ms))
+		return xa_err(ms.node);
+
+	return 0;
+}
+EXPORT_SYMBOL(mtree_insert_range);
+
+/**
+ * mtree_insert() - Insert an entry at a give index if there is no value.
+ * @mt: The maple tree
+ * @index : The index to store the value
+ * @entry: The entry to store
+ * @gfp: The FGP_FLAGS to use for allocations.
+ *
+ * Return: 0 on success, -EEXISTS if the range is occupied, -EINVAL on invalid
+ * request, -ENOMEM if memory could not be allocated.
+ */
+int mtree_insert(struct maple_tree *mt, unsigned long index, void *entry,
+		 gfp_t gfp)
+{
+	return mtree_insert_range(mt, index, index, entry, gfp);
+}
+EXPORT_SYMBOL(mtree_insert);
+
+int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
+		void *entry, unsigned long size, unsigned long min,
+		unsigned long max, gfp_t gfp)
+{
+	int ret = 0;
+
+	MA_STATE(mas, mt, min, max - size);
+	if (!mt_is_alloc(mt))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(mt_is_reserved(entry)))
+		return -EINVAL;
+
+	if (min > max)
+		return -EINVAL;
+
+	if (max < size)
+		return -EINVAL;
+
+	if (!size)
+		return -EINVAL;
+
+	mtree_lock(mt);
+retry:
+	mas.offset = 0;
+	mas.index = min;
+	mas.last = max - size;
+	ret = mas_alloc(&mas, entry, size, startp);
+	if (mas_nomem(&mas, gfp))
+		goto retry;
+
+	mtree_unlock(mt);
+	return ret;
+}
+EXPORT_SYMBOL(mtree_alloc_range);
+
+int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
+		void *entry, unsigned long size, unsigned long min,
+		unsigned long max, gfp_t gfp)
+{
+	int ret = 0;
+
+	MA_STATE(mas, mt, min, max - size);
+	if (!mt_is_alloc(mt))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(mt_is_reserved(entry)))
+		return -EINVAL;
+
+	if (min >= max)
+		return -EINVAL;
+
+	if (max < size - 1)
+		return -EINVAL;
+
+	if (!size)
+		return -EINVAL;
+
+	mtree_lock(mt);
+retry:
+	ret = mas_rev_alloc(&mas, min, max, entry, size, startp);
+	if (mas_nomem(&mas, gfp))
+		goto retry;
+
+	mtree_unlock(mt);
+	return ret;
+}
+EXPORT_SYMBOL(mtree_alloc_rrange);
+
+/**
+ * mtree_erase() - Find an index and erase the entire range.
+ * @mt: The maple tree
+ * @index: The index to erase
+ *
+ * Erasing is the same as a walk to an entry then a store of a NULL to that
+ * ENTIRE range.  In fact, it is implemented as such using the advanced API.
+ *
+ * Return: The entry stored at the @index or %NULL
+ */
+void *mtree_erase(struct maple_tree *mt, unsigned long index)
+{
+	void *entry = NULL;
+
+	MA_STATE(mas, mt, index, index);
+	trace_ma_op(__func__, &mas);
+
+	mtree_lock(mt);
+	entry = mas_erase(&mas);
+	mtree_unlock(mt);
+
+	return entry;
+}
+EXPORT_SYMBOL(mtree_erase);
+
+/**
+ * __mt_destroy() - Walk and free all nodes of a locked maple tree.
+ * @mt: The maple tree
+ *
+ * Note: Does not handle locking.
+ */
+void __mt_destroy(struct maple_tree *mt)
+{
+	void *root = mt_root_locked(mt);
+
+	rcu_assign_pointer(mt->ma_root, NULL);
+	if (xa_is_node(root))
+		mte_destroy_walk(root, mt);
+
+	mt->ma_flags = 0;
+}
+EXPORT_SYMBOL_GPL(__mt_destroy);
+
+/**
+ * mtree_destroy() - Destroy a maple tree
+ * @mt: The maple tree
+ *
+ * Frees all resources used by the tree.  Handles locking.
+ */
+void mtree_destroy(struct maple_tree *mt)
+{
+	mtree_lock(mt);
+	__mt_destroy(mt);
+	mtree_unlock(mt);
+}
+EXPORT_SYMBOL(mtree_destroy);
+
+/**
+ * mt_find() - Search from the start up until an entry is found.
+ * @mt: The maple tree
+ * @index: Pointer which contains the start location of the search
+ * @max: The maximum value to check
+ *
+ * Handles locking.  @index will be incremented to one beyond the range.
+ *
+ * Return: The entry at or after the @index or %NULL
+ */
+void *mt_find(struct maple_tree *mt, unsigned long *index, unsigned long max)
+{
+	MA_STATE(mas, mt, *index, *index);
+	void *entry;
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+	unsigned long copy = *index;
+#endif
+
+	trace_ma_read(__func__, &mas);
+
+	if ((*index) > max)
+		return NULL;
+
+	rcu_read_lock();
+retry:
+	entry = mas_state_walk(&mas);
+	if (mas_is_start(&mas))
+		goto retry;
+
+	if (unlikely(xa_is_zero(entry)))
+		entry = NULL;
+
+	if (entry)
+		goto unlock;
+
+	while (mas_searchable(&mas) && (mas.index < max)) {
+		entry = mas_next_entry(&mas, max);
+		if (likely(entry && !xa_is_zero(entry)))
+			break;
+	}
+
+	if (unlikely(xa_is_zero(entry)))
+		entry = NULL;
+unlock:
+	rcu_read_unlock();
+	if (likely(entry)) {
+		*index = mas.last + 1;
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+		if ((*index) && (*index) <= copy)
+			pr_err("index not increased! %lx <= %lx\n",
+			       *index, copy);
+		MT_BUG_ON(mt, (*index) && ((*index) <= copy));
+#endif
+	}
+
+	return entry;
+}
+EXPORT_SYMBOL(mt_find);
+
+/**
+ * mt_find_after() - Search from the start up until an entry is found.
+ * @mt: The maple tree
+ * @index: Pointer which contains the start location of the search
+ * @max: The maximum value to check
+ *
+ * Handles locking, detects wrapping on index == 0
+ *
+ * Return: The entry at or after the @index or %NULL
+ */
+void *mt_find_after(struct maple_tree *mt, unsigned long *index,
+		    unsigned long max)
+{
+	if (!(*index))
+		return NULL;
+
+	return mt_find(mt, index, max);
+}
+EXPORT_SYMBOL(mt_find_after);
+
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+atomic_t maple_tree_tests_run;
+EXPORT_SYMBOL_GPL(maple_tree_tests_run);
+atomic_t maple_tree_tests_passed;
+EXPORT_SYMBOL_GPL(maple_tree_tests_passed);
+
+#ifndef __KERNEL__
+extern void kmem_cache_set_non_kernel(struct kmem_cache *, unsigned int);
+void mt_set_non_kernel(unsigned int val)
+{
+	kmem_cache_set_non_kernel(maple_node_cache, val);
+}
+
+extern unsigned long kmem_cache_get_alloc(struct kmem_cache *);
+unsigned long mt_get_alloc_size(void)
+{
+	return kmem_cache_get_alloc(maple_node_cache);
+}
+
+extern void kmem_cache_zero_nr_tallocated(struct kmem_cache *);
+void mt_zero_nr_tallocated(void)
+{
+	kmem_cache_zero_nr_tallocated(maple_node_cache);
+}
+
+extern unsigned int kmem_cache_nr_tallocated(struct kmem_cache *);
+unsigned int mt_nr_tallocated(void)
+{
+	return kmem_cache_nr_tallocated(maple_node_cache);
+}
+
+extern unsigned int kmem_cache_nr_allocated(struct kmem_cache *);
+unsigned int mt_nr_allocated(void)
+{
+	return kmem_cache_nr_allocated(maple_node_cache);
+}
+
+/*
+ * mas_dead_node() - Check if the maple state is pointing to a dead node.
+ * @mas: The maple state
+ * @index: The index to restore in @mas.
+ *
+ * Used in test code.
+ * Return: 1 if @mas has been reset to MAS_START, 0 otherwise.
+ */
+static inline int mas_dead_node(struct ma_state *mas, unsigned long index)
+{
+	if (unlikely(!mas_searchable(mas) || mas_is_start(mas)))
+		return 0;
+
+	if (likely(!mte_dead_node(mas->node)))
+		return 0;
+
+	mas_rewalk(mas, index);
+	return 1;
+}
+
+void mt_cache_shrink(void)
+{
+}
+#else
+/*
+ * mt_cache_shrink() - For testing, don't use this.
+ *
+ * Certain testcases can trigger an OOM when combined with other memory
+ * debugging configuration options.  This function is used to reduce the
+ * possibility of an out of memory even due to kmem_cache objects remaining
+ * around for longer than usual.
+ */
+void mt_cache_shrink(void)
+{
+	kmem_cache_shrink(maple_node_cache);
+
+}
+EXPORT_SYMBOL_GPL(mt_cache_shrink);
+
+#endif /* not defined __KERNEL__ */
+/*
+ * mas_get_slot() - Get the entry in the maple state node stored at @offset.
+ * @mas: The maple state
+ * @offset: The offset into the slot array to fetch.
+ *
+ * Return: The entry stored at @offset.
+ */
+static inline struct maple_enode *mas_get_slot(struct ma_state *mas,
+		unsigned char offset)
+{
+	return mas_slot(mas, ma_slots(mas_mn(mas), mte_node_type(mas->node)),
+			offset);
+}
+
+
+/*
+ * mas_first_entry() - Go the first leaf and find the first entry.
+ * @mas: the maple state.
+ * @limit: the maximum index to check.
+ * @*r_start: Pointer to set to the range start.
+ *
+ * Sets mas->offset to the offset of the entry, r_start to the range minimum.
+ *
+ * Return: The first entry or MAS_NONE.
+ */
+static inline void *mas_first_entry(struct ma_state *mas, struct maple_node *mn,
+		unsigned long limit, enum maple_type mt)
+
+{
+	unsigned long max;
+	unsigned long *pivots;
+	void __rcu **slots;
+	void *entry = NULL;
+
+	mas->index = mas->min;
+	if (mas->index > limit)
+		goto none;
+
+	max = mas->max;
+	mas->offset = 0;
+	while (likely(!ma_is_leaf(mt))) {
+		MT_BUG_ON(mas->tree, mte_dead_node(mas->node));
+		slots = ma_slots(mn, mt);
+		entry = mas_slot(mas, slots, 0);
+		pivots = ma_pivots(mn, mt);
+		if (unlikely(ma_dead_node(mn)))
+			return NULL;
+		max = pivots[0];
+		mas->node = entry;
+		mn = mas_mn(mas);
+		mt = mte_node_type(mas->node);
+	}
+	MT_BUG_ON(mas->tree, mte_dead_node(mas->node));
+
+	mas->max = max;
+	slots = ma_slots(mn, mt);
+	entry = mas_slot(mas, slots, 0);
+	if (unlikely(ma_dead_node(mn)))
+		return NULL;
+
+	/* Slot 0 or 1 must be set */
+	if (mas->index > limit)
+		goto none;
+
+	if (likely(entry))
+		return entry;
+
+	mas->offset = 1;
+	entry = mas_slot(mas, slots, 1);
+	pivots = ma_pivots(mn, mt);
+	if (unlikely(ma_dead_node(mn)))
+		return NULL;
+
+	mas->index = pivots[0] + 1;
+	if (mas->index > limit)
+		goto none;
+
+	if (likely(entry))
+		return entry;
+
+none:
+	if (likely(!ma_dead_node(mn)))
+		mas->node = MAS_NONE;
+	return NULL;
+}
+
+/* Depth first search, post-order */
+static void mas_dfs_postorder(struct ma_state *mas, unsigned long max)
+{
+
+	struct maple_enode *p = MAS_NONE, *mn = mas->node;
+	unsigned long p_min, p_max;
+
+	mas_next_node(mas, mas_mn(mas), max);
+	if (!mas_is_none(mas))
+		return;
+
+	if (mte_is_root(mn))
+		return;
+
+	mas->node = mn;
+	mas_ascend(mas);
+	while (mas->node != MAS_NONE) {
+		p = mas->node;
+		p_min = mas->min;
+		p_max = mas->max;
+		mas_prev_node(mas, 0);
+	}
+
+	if (p == MAS_NONE)
+		return;
+
+	mas->node = p;
+	mas->max = p_max;
+	mas->min = p_min;
+}
+
+/* Tree validations */
+static void mt_dump_node(const struct maple_tree *mt, void *entry,
+		unsigned long min, unsigned long max, unsigned int depth);
+static void mt_dump_range(unsigned long min, unsigned long max,
+			  unsigned int depth)
+{
+	static const char spaces[] = "                                ";
+
+	if (min == max)
+		pr_info("%.*s%lu: ", depth * 2, spaces, min);
+	else
+		pr_info("%.*s%lu-%lu: ", depth * 2, spaces, min, max);
+}
+
+static void mt_dump_entry(void *entry, unsigned long min, unsigned long max,
+			  unsigned int depth)
+{
+	mt_dump_range(min, max, depth);
+
+	if (xa_is_value(entry))
+		pr_cont("value %ld (0x%lx) [%p]\n", xa_to_value(entry),
+				xa_to_value(entry), entry);
+	else if (xa_is_zero(entry))
+		pr_cont("zero (%ld)\n", xa_to_internal(entry));
+	else if (mt_is_reserved(entry))
+		pr_cont("UNKNOWN ENTRY (%p)\n", entry);
+	else
+		pr_cont("%p\n", entry);
+}
+
+static void mt_dump_range64(const struct maple_tree *mt, void *entry,
+			unsigned long min, unsigned long max, unsigned int depth)
+{
+	struct maple_range_64 *node = &mte_to_node(entry)->mr64;
+	bool leaf = mte_is_leaf(entry);
+	unsigned long first = min;
+	int i;
+
+	pr_cont(" contents: ");
+	for (i = 0; i < MAPLE_RANGE64_SLOTS - 1; i++)
+		pr_cont("%p %lu ", node->slot[i], node->pivot[i]);
+	pr_cont("%p\n", node->slot[i]);
+	for (i = 0; i < MAPLE_RANGE64_SLOTS; i++) {
+		unsigned long last = max;
+
+		if (i < (MAPLE_RANGE64_SLOTS - 1))
+			last = node->pivot[i];
+		else if (!node->slot[i] && max != mt_max[mte_node_type(entry)])
+			break;
+		if (last == 0 && i > 0)
+			break;
+		if (leaf)
+			mt_dump_entry(mt_slot(mt, node->slot, i),
+					first, last, depth + 1);
+		else if (node->slot[i])
+			mt_dump_node(mt, mt_slot(mt, node->slot, i),
+					first, last, depth + 1);
+
+		if (last == max)
+			break;
+		if (last > max) {
+			pr_err("node %p last (%lu) > max (%lu) at pivot %d!\n",
+					node, last, max, i);
+			break;
+		}
+		first = last + 1;
+	}
+}
+
+static void mt_dump_arange64(const struct maple_tree *mt, void *entry,
+			unsigned long min, unsigned long max, unsigned int depth)
+{
+	struct maple_arange_64 *node = &mte_to_node(entry)->ma64;
+	bool leaf = mte_is_leaf(entry);
+	unsigned long first = min;
+	int i;
+
+	pr_cont(" contents: ");
+	for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++)
+		pr_cont("%lu ", node->gap[i]);
+	pr_cont("| %02X %02X| ", node->meta.end, node->meta.gap);
+	for (i = 0; i < MAPLE_ARANGE64_SLOTS - 1; i++)
+		pr_cont("%p %lu ", node->slot[i], node->pivot[i]);
+	pr_cont("%p\n", node->slot[i]);
+	for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++) {
+		unsigned long last = max;
+
+		if (i < (MAPLE_ARANGE64_SLOTS - 1))
+			last = node->pivot[i];
+		else if (!node->slot[i])
+			break;
+		if (last == 0 && i > 0)
+			break;
+		if (leaf)
+			mt_dump_entry(mt_slot(mt, node->slot, i),
+					first, last, depth + 1);
+		else if (node->slot[i])
+			mt_dump_node(mt, mt_slot(mt, node->slot, i),
+					first, last, depth + 1);
+
+		if (last == max)
+			break;
+		if (last > max) {
+			pr_err("node %p last (%lu) > max (%lu) at pivot %d!\n",
+					node, last, max, i);
+			break;
+		}
+		first = last + 1;
+	}
+}
+
+static void mt_dump_node(const struct maple_tree *mt, void *entry,
+		unsigned long min, unsigned long max, unsigned int depth)
+{
+	struct maple_node *node = mte_to_node(entry);
+	unsigned int type = mte_node_type(entry);
+	unsigned int i;
+
+	mt_dump_range(min, max, depth);
+
+	pr_cont("node %p depth %d type %d parent %p", node, depth, type,
+			node ? node->parent : NULL);
+	switch (type) {
+	case maple_dense:
+		pr_cont("\n");
+		for (i = 0; i < MAPLE_NODE_SLOTS; i++) {
+			if (min + i > max)
+				pr_cont("OUT OF RANGE: ");
+			mt_dump_entry(mt_slot(mt, node->slot, i),
+					min + i, min + i, depth);
+		}
+		break;
+	case maple_leaf_64:
+	case maple_range_64:
+		mt_dump_range64(mt, entry, min, max, depth);
+		break;
+	case maple_arange_64:
+		mt_dump_arange64(mt, entry, min, max, depth);
+		break;
+
+	default:
+		pr_cont(" UNKNOWN TYPE\n");
+	}
+}
+
+void mt_dump(const struct maple_tree *mt)
+{
+	void *entry = rcu_dereference_check(mt->ma_root, mt_locked(mt));
+
+	pr_info("maple_tree(%p) flags %X, height %u root %p\n",
+		 mt, mt->ma_flags, mt_height(mt), entry);
+	if (!xa_is_node(entry))
+		mt_dump_entry(entry, 0, 0, 0);
+	else if (entry)
+		mt_dump_node(mt, entry, 0, mt_max[mte_node_type(entry)], 0);
+}
+EXPORT_SYMBOL_GPL(mt_dump);
+
+/*
+ * Calculate the maximum gap in a node and check if that's what is reported in
+ * the parent (unless root).
+ */
+static void mas_validate_gaps(struct ma_state *mas)
+{
+	struct maple_enode *mte = mas->node;
+	struct maple_node *p_mn;
+	unsigned long gap = 0, max_gap = 0;
+	unsigned long p_end, p_start = mas->min;
+	unsigned char p_slot;
+	unsigned long *gaps = NULL;
+	unsigned long *pivots = ma_pivots(mte_to_node(mte), mte_node_type(mte));
+	int i;
+
+	if (ma_is_dense(mte_node_type(mte))) {
+		for (i = 0; i < mt_slot_count(mte); i++) {
+			if (mas_get_slot(mas, i)) {
+				if (gap > max_gap)
+					max_gap = gap;
+				gap = 0;
+				continue;
+			}
+			gap++;
+		}
+		goto counted;
+	}
+
+	gaps = ma_gaps(mte_to_node(mte), mte_node_type(mte));
+	for (i = 0; i < mt_slot_count(mte); i++) {
+		p_end = mas_logical_pivot(mas, pivots, i, mte_node_type(mte));
+
+		if (!gaps) {
+			if (mas_get_slot(mas, i)) {
+				gap = 0;
+				goto not_empty;
+			}
+
+			gap += p_end - p_start + 1;
+		} else {
+			void *entry = mas_get_slot(mas, i);
+
+			gap = gaps[i];
+			if (!entry) {
+				if (gap != p_end - p_start + 1) {
+					pr_err("%p[%u] -> %p %lu != %lu - %lu + 1\n",
+						mas_mn(mas), i,
+						mas_get_slot(mas, i), gap,
+						p_end, p_start);
+					mt_dump(mas->tree);
+
+					MT_BUG_ON(mas->tree,
+						gap != p_end - p_start + 1);
+				}
+			} else {
+				if (gap > p_end - p_start + 1) {
+					pr_err("%p[%u] %lu >= %lu - %lu + 1 (%lu)\n",
+					mas_mn(mas), i, gap, p_end, p_start,
+					p_end - p_start + 1);
+					MT_BUG_ON(mas->tree,
+						gap > p_end - p_start + 1);
+				}
+			}
+		}
+
+		if (gap > max_gap)
+			max_gap = gap;
+not_empty:
+		p_start = p_end + 1;
+		if (p_end >= mas->max)
+			break;
+	}
+
+counted:
+	if (mte_is_root(mte))
+		return;
+
+	p_slot = mte_parent_slot(mas->node);
+	p_mn = mte_parent(mte);
+	MT_BUG_ON(mas->tree, max_gap > mas->max);
+	if (ma_gaps(p_mn, mas_parent_enum(mas, mte))[p_slot] != max_gap) {
+		pr_err("gap %p[%u] != %lu\n", p_mn, p_slot, max_gap);
+		mt_dump(mas->tree);
+	}
+
+	MT_BUG_ON(mas->tree,
+		  ma_gaps(p_mn, mas_parent_enum(mas, mte))[p_slot] != max_gap);
+}
+
+static void mas_validate_parent_slot(struct ma_state *mas)
+{
+	struct maple_node *parent;
+	struct maple_enode *node;
+	enum maple_type p_type = mas_parent_enum(mas, mas->node);
+	unsigned char p_slot = mte_parent_slot(mas->node);
+	void __rcu **slots;
+	int i;
+
+	if (mte_is_root(mas->node))
+		return;
+
+	parent = mte_parent(mas->node);
+	slots = ma_slots(parent, p_type);
+	MT_BUG_ON(mas->tree, mas_mn(mas) == parent);
+
+	/* Check prev/next parent slot for duplicate node entry */
+
+	for (i = 0; i < mt_slots[p_type]; i++) {
+		node = mas_slot(mas, slots, i);
+		if (i == p_slot) {
+			if (node != mas->node)
+				pr_err("parent %p[%u] does not have %p\n",
+					parent, i, mas_mn(mas));
+			MT_BUG_ON(mas->tree, node != mas->node);
+		} else if (node == mas->node) {
+			pr_err("Invalid child %p at parent %p[%u] p_slot %u\n",
+			       mas_mn(mas), parent, i, p_slot);
+			MT_BUG_ON(mas->tree, node == mas->node);
+		}
+	}
+}
+
+static void mas_validate_child_slot(struct ma_state *mas)
+{
+	enum maple_type type = mte_node_type(mas->node);
+	void __rcu **slots = ma_slots(mte_to_node(mas->node), type);
+	unsigned long *pivots = ma_pivots(mte_to_node(mas->node), type);
+	struct maple_enode *child;
+	unsigned char i;
+
+	if (mte_is_leaf(mas->node))
+		return;
+
+	for (i = 0; i < mt_slots[type]; i++) {
+		child = mas_slot(mas, slots, i);
+		if (!pivots[i] || pivots[i] == mas->max)
+			break;
+
+		if (!child)
+			break;
+
+		if (mte_parent_slot(child) != i) {
+			pr_err("Slot error at %p[%u]: child %p has pslot %u\n",
+			       mas_mn(mas), i, mte_to_node(child),
+			       mte_parent_slot(child));
+			MT_BUG_ON(mas->tree, 1);
+		}
+
+		if (mte_parent(child) != mte_to_node(mas->node)) {
+			pr_err("child %p has parent %p not %p\n",
+			       mte_to_node(child), mte_parent(child),
+			       mte_to_node(mas->node));
+			MT_BUG_ON(mas->tree, 1);
+		}
+	}
+}
+
+/*
+ * Validate all pivots are within mas->min and mas->max.
+ */
+static void mas_validate_limits(struct ma_state *mas)
+{
+	int i;
+	unsigned long prev_piv = 0;
+	enum maple_type type = mte_node_type(mas->node);
+	void __rcu **slots = ma_slots(mte_to_node(mas->node), type);
+	unsigned long *pivots = ma_pivots(mas_mn(mas), type);
+
+	/* all limits are fine here. */
+	if (mte_is_root(mas->node))
+		return;
+
+	for (i = 0; i < mt_slots[type]; i++) {
+		unsigned long piv;
+
+		piv = mas_safe_pivot(mas, pivots, i, type);
+
+		if (!piv && (i != 0))
+			break;
+
+		if (!mte_is_leaf(mas->node)) {
+			void *entry = mas_slot(mas, slots, i);
+
+			if (!entry)
+				pr_err("%p[%u] cannot be null\n",
+				       mas_mn(mas), i);
+
+			MT_BUG_ON(mas->tree, !entry);
+		}
+
+		if (prev_piv > piv) {
+			pr_err("%p[%u] piv %lu < prev_piv %lu\n",
+				mas_mn(mas), i, piv, prev_piv);
+			MT_BUG_ON(mas->tree, piv < prev_piv);
+		}
+
+		if (piv < mas->min) {
+			pr_err("%p[%u] %lu < %lu\n", mas_mn(mas), i,
+				piv, mas->min);
+			MT_BUG_ON(mas->tree, piv < mas->min);
+		}
+		if (piv > mas->max) {
+			pr_err("%p[%u] %lu > %lu\n", mas_mn(mas), i,
+				piv, mas->max);
+			MT_BUG_ON(mas->tree, piv > mas->max);
+		}
+		prev_piv = piv;
+		if (piv == mas->max)
+			break;
+	}
+	for (i += 1; i < mt_slots[type]; i++) {
+		void *entry = mas_slot(mas, slots, i);
+
+		if (entry && (i != mt_slots[type] - 1)) {
+			pr_err("%p[%u] should not have entry %p\n", mas_mn(mas),
+			       i, entry);
+			MT_BUG_ON(mas->tree, entry != NULL);
+		}
+
+		if (i < mt_pivots[type]) {
+			unsigned long piv = pivots[i];
+
+			if (!piv)
+				continue;
+
+			pr_err("%p[%u] should not have piv %lu\n",
+			       mas_mn(mas), i, piv);
+			MT_BUG_ON(mas->tree, i < mt_pivots[type] - 1);
+		}
+	}
+}
+
+static void mt_validate_nulls(struct maple_tree *mt)
+{
+	void *entry, *last = (void *)1;
+	unsigned char offset = 0;
+	void __rcu **slots;
+	MA_STATE(mas, mt, 0, 0);
+
+	mas_start(&mas);
+	if (mas_is_none(&mas) || (mas.node == MAS_ROOT))
+		return;
+
+	while (!mte_is_leaf(mas.node))
+		mas_descend(&mas);
+
+	slots = ma_slots(mte_to_node(mas.node), mte_node_type(mas.node));
+	do {
+		entry = mas_slot(&mas, slots, offset);
+		if (!last && !entry) {
+			pr_err("Sequential nulls end at %p[%u]\n",
+				mas_mn(&mas), offset);
+		}
+		MT_BUG_ON(mt, !last && !entry);
+		last = entry;
+		if (offset == mas_data_end(&mas)) {
+			mas_next_node(&mas, mas_mn(&mas), ULONG_MAX);
+			if (mas_is_none(&mas))
+				return;
+			offset = 0;
+			slots = ma_slots(mte_to_node(mas.node),
+					 mte_node_type(mas.node));
+		} else {
+			offset++;
+		}
+
+	} while (!mas_is_none(&mas));
+}
+
+/*
+ * validate a maple tree by checking:
+ * 1. The limits (pivots are within mas->min to mas->max)
+ * 2. The gap is correctly set in the parents
+ */
+void mt_validate(struct maple_tree *mt)
+{
+	unsigned char end;
+
+	MA_STATE(mas, mt, 0, 0);
+	rcu_read_lock();
+	mas_start(&mas);
+	if (!mas_searchable(&mas))
+		goto done;
+
+	mas_first_entry(&mas, mas_mn(&mas), ULONG_MAX, mte_node_type(mas.node));
+	while (!mas_is_none(&mas)) {
+		MT_BUG_ON(mas.tree, mte_dead_node(mas.node));
+		if (!mte_is_root(mas.node)) {
+			end = mas_data_end(&mas);
+			if ((end < mt_min_slot_count(mas.node)) &&
+			    (mas.max != ULONG_MAX)) {
+				pr_err("Invalid size %u of %p\n", end,
+				mas_mn(&mas));
+				MT_BUG_ON(mas.tree, 1);
+			}
+
+		}
+		mas_validate_parent_slot(&mas);
+		mas_validate_child_slot(&mas);
+		mas_validate_limits(&mas);
+		if (mt_is_alloc(mt))
+			mas_validate_gaps(&mas);
+		mas_dfs_postorder(&mas, ULONG_MAX);
+	}
+	mt_validate_nulls(mt);
+done:
+	rcu_read_unlock();
+
+}
+EXPORT_SYMBOL_GPL(mt_validate);
+
+#endif /* CONFIG_DEBUG_MAPLE_TREE */