// SPDX-License-Identifier: GPL-2.0+
/*
 * Maple Tree implementation
 * Copyright (c) 2018-2022 Oracle Corporation
 * Authors: Liam R. Howlett <liam@infradead.org>
 *          Matthew Wilcox <willy@infradead.org>
 * Copyright (c) 2023 ByteDance
 * Author: Peng Zhang <zhangpeng.00@bytedance.com>
 */

/*
 * 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 whereas 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 TP_FCT tracepoint_string(__func__)

/*
 * Kernel pointer hashing renders much of the maple tree dump useless as tagged
 * pointers get hashed to arbitrary values.
 *
 * If CONFIG_DEBUG_VM_MAPLE_TREE is set we are in a debug mode where it is
 * permissible to bypass this. Otherwise remain cautious and retain the hashing.
 *
 * Userland doesn't know about %px so also use %p there.
 */
#if defined(__KERNEL__) && defined(CONFIG_DEBUG_VM_MAPLE_TREE)
#define PTR_FMT "%px"
#else
#define PTR_FMT "%p"
#endif

#define MA_ROOT_PARENT 1

/*
 * Maple state flags
 * * MA_STATE_PREALLOC          - Preallocated nodes, WARN_ON allocation
 */
#define MA_STATE_PREALLOC       1

#define ma_parent_ptr(x) ((struct maple_pnode *)(x))
#define mas_tree_parent(x) ((unsigned long)(x->tree) | MA_ROOT_PARENT)
#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,
        [maple_copy]            = 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,
        [maple_copy]            = 3,
};
#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,
        [maple_copy]            = 3,
};
#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,
        [maple_copy]            = 1, /* Should never be used */
};
#define mt_min_slot_count(x) mt_min_slots[mte_node_type(x)]

/* Functions */
static inline struct maple_node *mt_alloc_one(gfp_t gfp)
{
        return kmem_cache_alloc(maple_node_cache, gfp);
}

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_return_sheaf(struct slab_sheaf *sheaf)
{
        kmem_cache_return_sheaf(maple_node_cache, GFP_NOWAIT, sheaf);
}

static struct slab_sheaf *mt_get_sheaf(gfp_t gfp, int count)
{
        return kmem_cache_prefill_sheaf(maple_node_cache, gfp, count);
}

static int mt_refill_sheaf(gfp_t gfp, struct slab_sheaf **sheaf,
                unsigned int size)
{
        return kmem_cache_refill_sheaf(maple_node_cache, gfp, sheaf, size);
}

/*
 * 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));
        kfree_rcu(node, rcu);
}

static void mt_set_height(struct maple_tree *mt, unsigned char height)
{
        unsigned int new_flags = mt->ma_flags;

        new_flags &= ~MT_FLAGS_HEIGHT_MASK;
        MT_BUG_ON(mt, height > MAPLE_HEIGHT_MAX);
        new_flags |= height << MT_FLAGS_HEIGHT_OFFSET;
        mt->ma_flags = new_flags;
}

static unsigned int mas_mt_height(struct ma_state *mas)
{
        return mt_height(mas->tree);
}

static inline unsigned int mt_attr(struct maple_tree *mt)
{
        return mt->ma_flags & ~MT_FLAGS_HEIGHT_MASK;
}

static __always_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 __always_inline bool ma_is_dense(const enum maple_type type)
{
        return type < maple_leaf_64;
}

static __always_inline bool ma_is_leaf(const enum maple_type type)
{
        return type < maple_range_64;
}

static __always_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 __always_inline bool mt_is_reserved(const void *entry)
{
        return ((unsigned long)entry < MAPLE_RESERVED_RANGE) &&
                xa_is_internal(entry);
}

static __always_inline void mas_set_err(struct ma_state *mas, long err)
{
        mas->node = MA_ERROR(err);
        mas->status = ma_error;
}

static __always_inline bool mas_is_ptr(const struct ma_state *mas)
{
        return mas->status == ma_root;
}

static __always_inline bool mas_is_start(const struct ma_state *mas)
{
        return mas->status == ma_start;
}

static __always_inline bool mas_is_none(const struct ma_state *mas)
{
        return mas->status == ma_none;
}

static __always_inline bool mas_is_paused(const struct ma_state *mas)
{
        return mas->status == ma_pause;
}

static __always_inline bool mas_is_overflow(struct ma_state *mas)
{
        return mas->status == ma_overflow;
}

static inline bool mas_is_underflow(struct ma_state *mas)
{
        return mas->status == ma_underflow;
}

static __always_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 ma_init_slot(void __rcu **slot, const struct maple_node *mn,
                                const enum maple_type mt)
{
        /* WARNING: this is unsafe if the slot is exposed to readers. */
        RCU_INIT_POINTER(*slot, (void *)mt_mk_node(mn, mt));
}

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 __maybe_unused *mte_set_full(const struct maple_enode *node)
{
        return (void *)((unsigned long)node & ~MAPLE_ENODE_NULL);
}

static inline void __maybe_unused *mte_clear_full(const struct maple_enode *node)
{
        return (void *)((unsigned long)node | MAPLE_ENODE_NULL);
}

static inline bool __maybe_unused mte_has_null(const struct maple_enode *node)
{
        return (unsigned long)node & MAPLE_ENODE_NULL;
}

static __always_inline bool ma_is_root(struct maple_node *node)
{
        return ((unsigned long)node->parent & MA_ROOT_PARENT);
}

static __always_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 __always_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.
 *
 * Node types:
 *  0b??1 = Root
 *  0b?00 = 16 bit nodes
 *  0b010 = 32 bit nodes
 *  0b110 = 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            0x02
#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_type() - Return the maple_type of the parent from the stored
 * parent type.
 * @mas: The maple state
 * @enode: The maple_enode to extract the parent's enum
 * Return: The node->parent maple_type
 */
static inline
enum maple_type mas_parent_type(struct ma_state *mas, struct maple_enode *enode)
{
        unsigned long p_type;

        p_type = (unsigned long)mte_to_node(enode)->parent;
        if (WARN_ON(p_type & MAPLE_PARENT_ROOT))
                return 0;

        p_type &= MAPLE_NODE_MASK;
        p_type &= ~mte_parent_slot_mask(p_type);
        switch (p_type) {
        case MAPLE_PARENT_RANGE64: /* or MAPLE_PARENT_ARANGE64 */
                if (mt_is_alloc(mas->tree))
                        return maple_arange_64;
                return maple_range_64;
        }

        return 0;
}

/*
 * mas_set_parent() - Set the parent node and encode the slot
 * @mas: The maple state
 * @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 mas_set_parent(struct ma_state *mas, 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);

        MAS_BUG_ON(mas, p_type == maple_dense);
        MAS_BUG_ON(mas, 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 __always_inline
unsigned int mte_parent_slot(const struct maple_enode *enode)
{
        unsigned long val = (unsigned long)mte_to_node(enode)->parent;

        if (unlikely(val & MA_ROOT_PARENT))
                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.
 * @enode: The encoded maple node.
 *
 * Return: The parent maple node.
 */
static __always_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 __always_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 __always_inline bool mte_dead_node(const struct maple_enode *enode)
{
        struct maple_node *node;

        node = mte_to_node(enode);
        return ma_dead_node(node);
}

/*
 * 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_copy:
                return node->cp.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_copy:
                return node->cp.gap;
        case maple_range_64:
        case maple_leaf_64:
        case maple_dense:
                return NULL;
        }
        return NULL;
}

/*
 * 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 __always_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;
}

/*
 * 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) {
        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_copy:
        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) {
        case maple_arange_64:
                return mn->ma64.slot;
        case maple_range_64:
        case maple_leaf_64:
                return mn->mr64.slot;
        case maple_copy:
                return mn->cp.slot;
        case maple_dense:
                return mn->slot;
        }

        return NULL;
}

static inline bool mt_write_locked(const struct maple_tree *mt)
{
        return mt_external_lock(mt) ? mt_write_lock_is_held(mt) :
                lockdep_is_held(&mt->ma_lock);
}

static __always_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 __always_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 __always_inline void *mt_slot_locked(struct maple_tree *mt,
                void __rcu **slots, unsigned char offset)
{
        return rcu_dereference_protected(slots[offset], mt_write_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 __always_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 __always_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 __always_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_write_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
 */
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
 */
static inline unsigned char ma_meta_gap(struct maple_node *mn)
{
        return mn->ma64.meta.gap;
}

/*
 * ma_set_meta_gap() - Set the largest gap location in a nodes metadata
 * @mn: The maple node
 * @mt: 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 mt_free_walk(struct rcu_head *head);
static void mt_destroy_walk(struct maple_enode *enode, struct maple_tree *mt,
                            bool free);
/*
 * 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;
        struct maple_node *node;
        bool in_rcu = mt_in_rcu(mas->tree);

        while (mat->head) {
                next = mte_to_mat(mat->head)->next;
                node = mte_to_node(mat->head);
                mt_destroy_walk(mat->head, mas->tree, !in_rcu);
                if (in_rcu)
                        call_rcu(&node->rcu, mt_free_walk);
                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);
}

/*
 * mas_ascend() - Walk up a level of the tree.
 * @mas: The maple state
 *
 * Sets the @mas->max and @mas->min for the parent node of mas->node.  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;
        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_type(mas, mas->node);
        mas->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;

        if (mte_is_root(a_enode)) {
                mas->max = ULONG_MAX;
                mas->min = 0;
                return 0;
        }

        min = 0;
        max = ULONG_MAX;

        /*
         * !mas->offset implies that parent node min == mas->min.
         * mas->offset > 0 implies that we need to walk up to find the
         * implied pivot min.
         */
        if (!mas->offset) {
                min = mas->min;
                set_min = true;
        }

        if (mas->max == ULONG_MAX)
                set_max = true;

        do {
                p_enode = a_enode;
                a_type = mas_parent_type(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 __always_inline struct maple_node *mas_pop_node(struct ma_state *mas)
{
        struct maple_node *ret;

        if (mas->alloc) {
                ret = mas->alloc;
                mas->alloc = NULL;
                goto out;
        }

        if (WARN_ON_ONCE(!mas->sheaf))
                return NULL;

        ret = kmem_cache_alloc_from_sheaf(maple_node_cache, GFP_NOWAIT, mas->sheaf);

out:
        memset(ret, 0, sizeof(*ret));
        return ret;
}

/*
 * 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)
{
        if (!mas->node_request)
                return;

        if (mas->node_request == 1) {
                if (mas->sheaf)
                        goto use_sheaf;

                if (mas->alloc)
                        return;

                mas->alloc = mt_alloc_one(gfp);
                if (!mas->alloc)
                        goto error;

                mas->node_request = 0;
                return;
        }

use_sheaf:
        if (unlikely(mas->alloc)) {
                kfree(mas->alloc);
                mas->alloc = NULL;
        }

        if (mas->sheaf) {
                unsigned long refill;

                refill = mas->node_request;
                if (kmem_cache_sheaf_size(mas->sheaf) >= refill) {
                        mas->node_request = 0;
                        return;
                }

                if (mt_refill_sheaf(gfp, &mas->sheaf, refill))
                        goto error;

                mas->node_request = 0;
                return;
        }

        mas->sheaf = mt_get_sheaf(gfp, mas->node_request);
        if (likely(mas->sheaf)) {
                mas->node_request = 0;
                return;
        }

error:
        mas_set_err(mas, -ENOMEM);
}

static inline void mas_empty_nodes(struct ma_state *mas)
{
        mas->node_request = 0;
        if (mas->sheaf) {
                mt_return_sheaf(mas->sheaf);
                mas->sheaf = NULL;
        }

        if (mas->alloc) {
                kfree(mas->alloc);
                mas->alloc = NULL;
        }
}

/*
 * 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)
{
        ma_free_rcu(mte_to_node(used));
}

/*
 * mas_start() - Sets up maple state for operations.
 * @mas: The maple state.
 *
 * If mas->status == ma_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->status == ma_none
 * - If it's a single entry:    The entry & mas->status == ma_root
 * - If it's a tree:            NULL & mas->status == ma_active
 */
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;

retry:
                mas->depth = 0;
                root = mas_root(mas);
                /* Tree with nodes */
                if (likely(xa_is_node(root))) {
                        mas->depth = 0;
                        mas->status = ma_active;
                        mas->node = mte_safe_root(root);
                        mas->offset = 0;
                        if (mte_dead_node(mas->node))
                                goto retry;

                        return NULL;
                }

                mas->node = NULL;
                /* empty tree */
                if (unlikely(!root)) {
                        mas->status = ma_none;
                        mas->offset = MAPLE_NODE_SLOTS;
                        return NULL;
                }

                /* Single entry tree */
                mas->status = ma_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 __always_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];
}

static inline
void wr_mas_setup(struct ma_wr_state *wr_mas, struct ma_state *mas)
{
        wr_mas->node = mas_mn(mas);
        wr_mas->type = mte_node_type(mas->node);
        wr_mas->pivots = ma_pivots(wr_mas->node, wr_mas->type);
        wr_mas->slots = ma_slots(wr_mas->node, wr_mas->type);
        wr_mas->r_min = mas_safe_min(mas, wr_mas->pivots, mas->offset);
        wr_mas->r_max = mas_safe_pivot(mas, wr_mas->pivots, mas->offset,
                                       wr_mas->type);
}

static inline
void wr_mas_ascend(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;

        mas_ascend(mas);
        wr_mas_setup(wr_mas, mas);
        mas->end = ma_data_end(wr_mas->node, wr_mas->type, wr_mas->pivots,
                               mas->max);
        /* Careful, this may be wrong.. */
        wr_mas->end_piv = wr_mas->r_max;
        wr_mas->offset_end = mas->offset;
}

static inline unsigned long ma_leaf_max_gap(struct maple_node *mn,
                enum maple_type mt, unsigned long min, unsigned long max,
                unsigned long *pivots, void __rcu **slots)
{
        unsigned long pstart, gap, max_gap;
        unsigned char i;
        unsigned char max_piv;

        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.
         */
        if (likely(!slots[0])) {
                max_gap = pivots[0] - 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, max) - 1;
        /*
         * Check end implied pivot which can only be a gap on the right most
         * node.
         */
        if (unlikely(max == ULONG_MAX) && !slots[max_piv + 1]) {
                gap = ULONG_MAX - pivots[max_piv];
                if (gap > max_gap)
                        max_gap = gap;

                if (max_gap > pivots[max_piv] - min)
                        return max_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;
}

/*
 * mas_leaf_max_gap() - Returns the largest gap in a leaf node
 * @mas: the maple state
 *
 * Return: The maximum gap in the leaf.
 */
static inline unsigned long mas_leaf_max_gap(struct ma_state *mas)
{
        enum maple_type mt;
        struct maple_node *mn;
        unsigned long *pivots;
        void __rcu **slots;

        mn = mas_mn(mas);
        mt = mte_node_type(mas->node);
        slots = ma_slots(mn, mt);
        pivots = ma_pivots(mn, mt);

        return ma_leaf_max_gap(mn, mt, mas->min, mas->max, pivots, slots);
}

/*
 * 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.
 *
 * 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);
        MAS_BUG_ON(mas, mt != maple_arange_64);
        offset = ma_meta_gap(node);
        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_type(mas, mas->node);
        penode = mt_mk_node(pnode, pmt);
        pgaps = ma_gaps(pnode, pmt);

ascend:
        MAS_BUG_ON(mas, pmt != maple_arange_64);
        meta_offset = ma_meta_gap(pnode);
        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) {
                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_type(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_type(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 = mte_to_node(parent);
        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);
                mas_set_parent(mas, child, parent, offset);
        } while (offset--);
}

/*
 * mas_put_in_tree() - Put a new node in the tree, smp_wmb(), and mark the old
 * node as dead.
 * @mas: the maple state with the new node
 * @old_enode: The old maple encoded node to replace.
 * @new_height: if we are inserting a root node, update the height of the tree
 */
static inline void mas_put_in_tree(struct ma_state *mas,
                struct maple_enode *old_enode, char new_height)
        __must_hold(mas->tree->ma_lock)
{
        unsigned char offset;
        void __rcu **slots;

        if (mte_is_root(mas->node)) {
                mas_mn(mas)->parent = ma_parent_ptr(mas_tree_parent(mas));
                rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
                mt_set_height(mas->tree, new_height);
        } else {

                offset = mte_parent_slot(mas->node);
                slots = ma_slots(mte_parent(mas->node),
                                 mas_parent_type(mas, mas->node));
                rcu_assign_pointer(slots[offset], mas->node);
        }

        mte_set_node_dead(old_enode);
}

/*
 * mas_replace_node() - Replace a node by putting it in the tree, marking it
 * dead, and freeing it.
 * the parent encoding to locate the maple node in the tree.
 * @mas: the ma_state with @mas->node pointing to the new node.
 * @old_enode: The old maple encoded node.
 * @new_height: The new height of the tree as a result of the operation
 */
static inline void mas_replace_node(struct ma_state *mas,
                struct maple_enode *old_enode, unsigned char new_height)
        __must_hold(mas->tree->ma_lock)
{
        mas_put_in_tree(mas, old_enode, new_height);
        mas_free(mas, old_enode);
}

/*
 * mas_find_child() - Find a child who has the parent @mas->node.
 * @mas: the maple state with the parent.
 * @child: the maple state to store the child.
 */
static inline bool mas_find_child(struct ma_state *mas, struct ma_state *child)
        __must_hold(mas->tree->ma_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;
}

/*
 * mas_leaf_set_meta() - Set the metadata of a leaf if possible.
 * @node: The maple node
 * @mt: The maple type
 * @end: The node end
 */
static inline void mas_leaf_set_meta(struct maple_node *node,
                enum maple_type mt, unsigned char end)
{
        if (end < mt_slots[mt] - 1)
                ma_set_meta(node, mt, 0, 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);

        /* For root node, p_slot is set to 0 by mte_parent_slot(). */
        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;
}

/*
 * mas_wr_node_walk() - Find the correct offset for the index in the @mas.
 *                      If @mas->index cannot be found within the containing
 *                      node, we traverse to the last entry in the node.
 * @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, offset;

        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 = mas->end = ma_data_end(wr_mas->node, wr_mas->type,
                                       wr_mas->pivots, mas->max);
        offset = mas->offset;

        while (offset < count && mas->index > wr_mas->pivots[offset])
                offset++;

        wr_mas->r_max = offset < count ? wr_mas->pivots[offset] : mas->max;
        wr_mas->r_min = mas_safe_min(mas, wr_mas->pivots, offset);
        wr_mas->offset_end = mas->offset = offset;
}

static inline void rebalance_sib(struct ma_state *parent, struct ma_state *sib)
{
        *sib = *parent;
        /* Prioritize move right to pull data left */
        if (sib->offset < sib->end)
                sib->offset++;
        else
                sib->offset--;

        mas_descend(sib);
        sib->end = mas_data_end(sib);
}

static inline
void spanning_sib(struct ma_wr_state *l_wr_mas,
                struct ma_wr_state *r_wr_mas, struct ma_state *nneighbour)
{
        struct ma_state l_tmp = *l_wr_mas->mas;
        struct ma_state r_tmp = *r_wr_mas->mas;
        unsigned char depth = 0;

        do {
                mas_ascend(&r_tmp);
                mas_ascend(&l_tmp);
                depth++;
                if (r_tmp.offset < mas_data_end(&r_tmp)) {
                        r_tmp.offset++;
                        mas_descend(&r_tmp);
                        r_tmp.offset = 0;
                        while (--depth)
                                mas_descend(&r_tmp);

                        r_tmp.end = mas_data_end(&r_tmp);
                        *nneighbour = r_tmp;
                        return;
                } else if (l_tmp.offset) {
                        l_tmp.offset--;
                        do {
                                mas_descend(&l_tmp);
                                l_tmp.offset = mas_data_end(&l_tmp);
                        } while (--depth);

                        l_tmp.end = l_tmp.offset;
                        *nneighbour = l_tmp;
                        return;
                }
        } while (!mte_is_root(r_tmp.node));

        WARN_ON_ONCE(1);
}

/*
 * mas_topiary_node() - Dispose of a single node
 * @mas: The maple state for pushing nodes
 * @in_rcu: If the tree is in rcu mode
 *
 * The node will either be RCU freed or pushed back on the maple state.
 */
static inline void mas_topiary_node(struct ma_state *mas,
                struct ma_state *tmp_mas, bool in_rcu)
{
        struct maple_node *tmp;
        struct maple_enode *enode;

        if (mas_is_none(tmp_mas))
                return;

        enode = tmp_mas->node;
        tmp = mte_to_node(enode);
        mte_set_node_dead(enode);
        ma_free_rcu(tmp);
}

/*
 * mas_topiary_replace() - Replace the data with new data, then repair the
 * parent links within the new tree.  Iterate over the dead sub-tree and collect
 * the dead subtrees and topiary the nodes that are no longer of use.
 *
 * The new tree will have up to three children with the correct parent.  Keep
 * track of the new entries as they need to be followed to find the next level
 * of new entries.
 *
 * The old tree will have up to three children with the old parent.  Keep track
 * of the old entries as they may have more nodes below replaced.  Nodes within
 * [index, last] are dead subtrees, others need to be freed and followed.
 *
 * @mas: The maple state pointing at the new data
 * @old_enode: The maple encoded node being replaced
 * @new_height: The new height of the tree as a result of the operation
 *
 */
static inline void mas_topiary_replace(struct ma_state *mas,
                struct maple_enode *old_enode, unsigned char new_height)
{
        struct ma_state tmp[3], tmp_next[3];
        MA_TOPIARY(subtrees, mas->tree);
        bool in_rcu;
        int i, n;

        /* Place data in tree & then mark node as old */
        mas_put_in_tree(mas, old_enode, new_height);

        /* Update the parent pointers in the tree */
        tmp[0] = *mas;
        tmp[0].offset = 0;
        tmp[1].status = ma_none;
        tmp[2].status = ma_none;
        while (!mte_is_leaf(tmp[0].node)) {
                n = 0;
                for (i = 0; i < 3; i++) {
                        if (mas_is_none(&tmp[i]))
                                continue;

                        while (n < 3) {
                                if (!mas_find_child(&tmp[i], &tmp_next[n]))
                                        break;
                                n++;
                        }

                        mas_adopt_children(&tmp[i], tmp[i].node);
                }

                if (MAS_WARN_ON(mas, n == 0))
                        break;

                while (n < 3)
                        tmp_next[n++].status = ma_none;

                for (i = 0; i < 3; i++)
                        tmp[i] = tmp_next[i];
        }

        /* Collect the old nodes that need to be discarded */
        if (mte_is_leaf(old_enode))
                return mas_free(mas, old_enode);

        tmp[0] = *mas;
        tmp[0].offset = 0;
        tmp[0].node = old_enode;
        tmp[1].status = ma_none;
        tmp[2].status = ma_none;
        in_rcu = mt_in_rcu(mas->tree);
        do {
                n = 0;
                for (i = 0; i < 3; i++) {
                        if (mas_is_none(&tmp[i]))
                                continue;

                        while (n < 3) {
                                if (!mas_find_child(&tmp[i], &tmp_next[n]))
                                        break;

                                if ((tmp_next[n].min >= tmp_next->index) &&
                                    (tmp_next[n].max <= tmp_next->last)) {
                                        mat_add(&subtrees, tmp_next[n].node);
                                        tmp_next[n].status = ma_none;
                                } else {
                                        n++;
                                }
                        }
                }

                if (MAS_WARN_ON(mas, n == 0))
                        break;

                while (n < 3)
                        tmp_next[n++].status = ma_none;

                for (i = 0; i < 3; i++) {
                        mas_topiary_node(mas, &tmp[i], in_rcu);
                        tmp[i] = tmp_next[i];
                }
        } while (!mte_is_leaf(tmp[0].node));

        for (i = 0; i < 3; i++)
                mas_topiary_node(mas, &tmp[i], in_rcu);

        mas_mat_destroy(mas, &subtrees);
}

/*
 * node_copy() - Copy from one node to another.
 *
 * @mas: The maple state
 * @src: The source node
 * @start: The offset into the src to start copying
 * @size: The size to copy (non-zero)
 * @s_max: The source node max
 * @s_mt: The source maple node type
 * @dst: The destination
 * @d_start: The start location in the destination node
 * @d_mt: The destination maple node type
 */
static inline
unsigned long node_copy(struct ma_state *mas, struct maple_node *src,
        unsigned char start, unsigned char size, unsigned long s_max,
        enum maple_type s_mt, struct maple_node *dst, unsigned char d_start,
        enum maple_type d_mt)
{
        unsigned long *s_pivots, *d_pivots;
        void __rcu **s_slots, **d_slots;
        unsigned long *s_gaps, *d_gaps;
        unsigned long d_max;

        d_slots = ma_slots(dst, d_mt) + d_start;
        d_pivots = ma_pivots(dst, d_mt) + d_start;
        s_slots = ma_slots(src, s_mt) + start;
        s_pivots = ma_pivots(src, s_mt) + start;
        memcpy(d_slots, s_slots, size * sizeof(void __rcu *));
        if (!ma_is_leaf(d_mt) && s_mt == maple_copy) {
                struct maple_enode *edst = mt_mk_node(dst, d_mt);


                for (int i = 0; i < size; i++)
                        mas_set_parent(mas,
                                       mt_slot_locked(mas->tree, d_slots, i),
                                       edst, d_start + i);
        }

        d_gaps = ma_gaps(dst, d_mt);
        if (d_gaps) {
                s_gaps = ma_gaps(src, s_mt) + start;
                d_gaps += d_start;
                memcpy(d_gaps, s_gaps, size * sizeof(unsigned long));
        }

        if (start + size - 1 < mt_pivots[s_mt])
                d_max = s_pivots[size - 1];
        else
                d_max = s_max;

        if (d_start + size <= mt_pivots[d_mt])
                d_pivots[size - 1] = d_max;

        size--;
        if (size)
                memcpy(d_pivots, s_pivots, size * sizeof(unsigned long));

        return d_max;
}

/*
 * node_finalise() - Zero out unused area and populate metadata
 * @node: The maple node
 * @mt: The maple node type
 * @end: The end of the used area
 */
static inline
void node_finalise(struct maple_node *node, enum maple_type mt,
                   unsigned char end)
{
        unsigned char max_end = mt_slots[mt];
        unsigned char size;
        unsigned long *gaps;
        unsigned char gap_slot;

        gaps = ma_gaps(node, mt);
        if (end < max_end - 1) {
                size = max_end - end;
                memset(ma_slots(node, mt) + end, 0, size * sizeof(void *));

                if (gaps)
                        memset(gaps + end, 0, size * sizeof(unsigned long));

                if (--size)
                        memset(ma_pivots(node, mt) + end, 0, size * sizeof(unsigned long));
        }

        gap_slot = 0;
        if (gaps && !ma_is_leaf(mt)) {
                unsigned long max_gap;

                max_gap = 0;
                for (int i = 0; i <= end; i++)
                        if (gaps[i] > max_gap) {
                                gap_slot = i;
                                max_gap = gaps[i];
                        }
        }

        if (mt == maple_arange_64)
                ma_set_meta(node, mt, gap_slot, end - 1);
        else if (end <= max_end - 1)
                ma_set_meta(node, mt, gap_slot, end - 1);
}

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 {
                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);
                prev_min = min;
                prev_max = max;
                if (pivots[0] >= mas->index) {
                        offset = 0;
                        max = pivots[0];
                        goto next;
                }

                offset = 1;
                while (offset < end) {
                        if (pivots[offset] >= mas->index) {
                                max = pivots[offset];
                                break;
                        }
                        offset++;
                }

                min = pivots[offset - 1] + 1;
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->end = end;
        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_wmb_replace() - Write memory barrier and replace
 * @mas: The maple state
 * @cp: The maple copy node
 *
 * Updates gap as necessary.
 */
static inline void mas_wmb_replace(struct ma_state *mas, struct maple_copy *cp)
{
        struct maple_enode *old_enode;

        old_enode = mas->node;
        mas->node = mt_slot_locked(mas->tree, cp->slot, 0);
        /* Insert the new data in the tree */
        mas_topiary_replace(mas, old_enode, cp->height);
        if (!mte_is_leaf(mas->node))
                mas_update_gap(mas);

        mtree_range_walk(mas);
}


/*
 * cp_leaf_init() - Initialize a maple_copy node for the leaf level of a
 * spanning store
 * @cp: The maple copy node
 * @mas: The maple state
 * @l_wr_mas: The left write state of the spanning store
 * @r_wr_mas: The right write state of the spanning store
 */
static inline void cp_leaf_init(struct maple_copy *cp,
                struct ma_state *mas, struct ma_wr_state *l_wr_mas,
                struct ma_wr_state *r_wr_mas)
{
        unsigned char end = 0;

        /*
         * WARNING: The use of RCU_INIT_POINTER() makes it extremely important
         * to not expose the maple_copy node to any readers.  Exposure may
         * result in buggy code when a compiler reorders the instructions.
         */

        cp->height = 1;
        /* Create entries to insert including split entries to left and right */
        if (l_wr_mas->r_min < mas->index) {
                end++;
                RCU_INIT_POINTER(cp->slot[0], l_wr_mas->content);
                cp->pivot[0] = mas->index - 1;
        }
        RCU_INIT_POINTER(cp->slot[end], l_wr_mas->entry);
        cp->pivot[end] = mas->last;

        if (r_wr_mas->end_piv > mas->last) {
                end++;
                RCU_INIT_POINTER(cp->slot[end],
                                 r_wr_mas->slots[r_wr_mas->offset_end]);
                cp->pivot[end] = r_wr_mas->end_piv;
        }

        cp->min = l_wr_mas->r_min;
        cp->max = cp->pivot[end];
        cp->end = end;
}

/*
 * cp_data_calc() - Calculate the size of the data (1 indexed).
 * @cp: The maple copy struct with the new data populated.
 * @l_wr_mas: The maple write state containing the data to the left of the write
 * @r_wr_mas: The maple write state containing the data to the right of the
 * write
 *
 * cp->data is a size (not indexed by 0).
 */
static inline void cp_data_calc(struct maple_copy *cp,
                struct ma_wr_state *l_wr_mas, struct ma_wr_state *r_wr_mas)
{

        /* Add 1 every time for the 0th element */
        cp->data = l_wr_mas->mas->offset;
        /* Add the new data and any partial overwrites */
        cp->data += cp->end + 1;
        /* Data from right (offset + 1 to end), +1 for zero */
        cp->data += r_wr_mas->mas->end - r_wr_mas->offset_end;
}

static bool data_fits(struct ma_state *sib, struct ma_state *mas,
                struct maple_copy *cp)
{
        unsigned char new_data;
        enum maple_type type;
        unsigned char space;
        unsigned char end;

        type = mte_node_type(mas->node);
        space = 2 * mt_slots[type];
        end = sib->end;

        new_data = end + 1 + cp->data;
        if (new_data > space)
                return false;

        /*
         * This is off by one by design.  The extra space is left to reduce
         * jitter in operations that add then remove two entries.
         *
         * end is an index while new space and data are both sizes.  Adding one
         * to end to convert the index to a size means that the below
         * calculation should be <=, but we want to keep an extra space in nodes
         * to reduce jitter.
         *
         * Note that it is still possible to get a full node on the left by the
         * NULL landing exactly on the split.  The NULL ending of a node happens
         * in the dst_setup() function, where we will either increase the split
         * by one or decrease it by one, if possible.  In the case of split
         * (this case), it is always possible to shift the spilt by one - again
         * because there is at least one slot free by the below checking.
         */
        if (new_data < space)
                return true;

        return false;
}

static inline void push_data_sib(struct maple_copy *cp, struct ma_state *mas,
                struct ma_state *sib, struct ma_state *parent)
{

        if (mte_is_root(mas->node))
                goto no_push;


        *sib = *parent;
        if (sib->offset) {
                sib->offset--;
                mas_descend(sib);
                sib->end = mas_data_end(sib);
                if (data_fits(sib, mas, cp))    /* Push left */
                        return;

                *sib = *parent;
        }

        if (sib->offset >= sib->end)
                goto no_push;

        sib->offset++;
        mas_descend(sib);
        sib->end = mas_data_end(sib);
        if (data_fits(sib, mas, cp))            /* Push right*/
                return;

no_push:
        sib->end = 0;
}

/*
 * rebalance_data() - Calculate the @cp data, populate @sib if insufficient or
 * if the data can be pushed into a sibling.
 * @cp: The maple copy node
 * @wr_mas: The left write maple state
 * @sib: The maple state of the sibling.
 *
 * Note: @cp->data is a size and not indexed by 0. @sib->end may be set to 0 to
 * indicate it will not be used.
 *
 */
static inline void rebalance_data(struct maple_copy *cp,
                struct ma_wr_state *wr_mas, struct ma_state *sib,
                struct ma_state *parent)
{
        cp_data_calc(cp, wr_mas, wr_mas);
        sib->end = 0;
        if (cp->data > mt_slots[wr_mas->type]) {
                push_data_sib(cp, wr_mas->mas, sib, parent);
                if (sib->end)
                        goto use_sib;
        } else if (cp->data <= mt_min_slots[wr_mas->type]) {
                if ((wr_mas->mas->min != 0) ||
                    (wr_mas->mas->max != ULONG_MAX)) {
                        rebalance_sib(parent, sib);
                        goto use_sib;
                }
        }

        return;

use_sib:

        cp->data += sib->end + 1;
}

/*
 * spanning_data() - Calculate the @cp data and populate @sib if insufficient
 * @cp: The maple copy node
 * @l_wr_mas: The left write maple state
 * @r_wr_mas: The right write maple state
 * @sib: The maple state of the sibling.
 *
 * Note: @cp->data is a size and not indexed by 0. @sib->end may be set to 0 to
 * indicate it will not be used.
 */
static inline void spanning_data(struct maple_copy *cp,
                struct ma_wr_state *l_wr_mas, struct ma_wr_state *r_wr_mas,
                struct ma_state *sib)
{
        cp_data_calc(cp, l_wr_mas, r_wr_mas);
        if (((l_wr_mas->mas->min != 0) || (r_wr_mas->mas->max != ULONG_MAX)) &&
            (cp->data <= mt_min_slots[l_wr_mas->type])) {
                spanning_sib(l_wr_mas, r_wr_mas, sib);
                cp->data += sib->end + 1;
        } else {
                sib->end = 0;
        }
}

/*
 * dst_setup() - Set up one or more destinations for the new data.
 * @cp: The maple copy node
 * @mas: The maple state
 * @mt: The source node type
 */
static inline
void dst_setup(struct maple_copy *cp, struct ma_state *mas, enum maple_type mt)
{
        /* Data is 1 indexed, every src has +1 added.  */

        if (cp->data <= mt_slots[mt]) {
                cp->split = cp->data - 1;
                cp->d_count = 1;
                goto node_setup;
        }

        cp->split = (cp->data - 1) / 2;
        cp->d_count = 2;
        if (cp->data < mt_slots[mt] * 2)
                goto node_setup;

        if (cp->data == mt_slots[mt] * 2) {
                unsigned char off;
                unsigned char s;

                if (!ma_is_leaf(mt))
                        goto node_setup;

                /*
                 * Leaf nodes are a bit tricky because we cannot assume the data
                 * can fit due to the NULL limitation on node ends.
                 */
                off = cp->split;
                for (s = 0; s < cp->s_count; s++) {
                        unsigned char s_off;

                        s_off = cp->src[s].end - cp->src[s].start;
                        if (s_off >= off)
                                break;

                        s_off++;
                        off -= s_off;
                }

                off += cp->src[s].start;
                if (ma_slots(cp->src[s].node, cp->src[s].mt)[off])
                        goto node_setup;

                cp->split++;
                if (cp->split < mt_slots[mt])
                        goto node_setup;

                cp->split -= 2;
                if (cp->data - 2 - cp->split < mt_slots[mt])
                        goto node_setup;

        }

        /* No other choice but to 3-way split the data */
        cp->split = (cp->data + 2) / 3;
        cp->d_count = 3;

node_setup:
        for (int i = 0; i < cp->d_count; i++) {
                cp->dst[i].mt = mt;
                cp->dst[i].node = ma_mnode_ptr(mas_pop_node(mas));
        }
}

static inline void append_mas_cp(struct maple_copy *cp,
        struct ma_state *mas, unsigned char start, unsigned char end)
{
        struct maple_node *node;
        enum maple_type mt;
        unsigned char count;

        count = cp->s_count;
        node = mas_mn(mas);
        mt = mte_node_type(mas->node);
        cp->src[count].node = node;
        cp->src[count].mt = mt;
        if (mas->end <= end)
                cp->src[count].max = mas->max;
        else
                cp->src[count].max = ma_pivots(node, mt)[end];

        cp->src[count].start = start;
        cp->src[count].end = end;
        cp->s_count++;
}

static inline void append_wr_mas_cp(struct maple_copy *cp,
        struct ma_wr_state *wr_mas, unsigned char start, unsigned char end)
{
        unsigned char count;

        count = cp->s_count;
        cp->src[count].node = wr_mas->node;
        cp->src[count].mt = wr_mas->type;
        if (wr_mas->mas->end <= end)
                cp->src[count].max = wr_mas->mas->max;
        else
                cp->src[count].max = wr_mas->pivots[end];

        cp->src[count].start = start;
        cp->src[count].end = end;
        cp->s_count++;
}

static inline void init_cp_src(struct maple_copy *cp)
{
        cp->src[cp->s_count].node = ma_mnode_ptr(cp);
        cp->src[cp->s_count].mt = maple_copy;
        cp->src[cp->s_count].max = cp->max;
        cp->src[cp->s_count].start = 0;
        cp->src[cp->s_count].end = cp->end;
        cp->s_count++;
}

/*
 * multi_src_setup() - Set the @cp node up with multiple sources to copy from.
 * @cp: The maple copy node
 * @l_wr_mas: The left write maple state
 * @r_wr_mas: The right write maple state
 * @sib: The sibling maple state
 *
 * Note: @sib->end == 0 indicates no sibling will be used.
 */
static inline
void multi_src_setup(struct maple_copy *cp, struct ma_wr_state *l_wr_mas,
                struct ma_wr_state *r_wr_mas, struct ma_state *sib)
{
        cp->s_count = 0;
        if (sib->end && sib->max < l_wr_mas->mas->min)
                append_mas_cp(cp, sib, 0, sib->end);

        /* Copy left 0 - offset */
        if (l_wr_mas->mas->offset) {
                unsigned char off = l_wr_mas->mas->offset - 1;

                append_wr_mas_cp(cp, l_wr_mas, 0, off);
                cp->src[cp->s_count - 1].max = cp->min - 1;
        }

        init_cp_src(cp);

        /* Copy right either from offset or offset + 1 pending on r_max */
        if (r_wr_mas->mas->end != r_wr_mas->offset_end)
                append_wr_mas_cp(cp, r_wr_mas, r_wr_mas->offset_end + 1,
                               r_wr_mas->mas->end);

        if (sib->end && sib->min > r_wr_mas->mas->max)
                append_mas_cp(cp, sib, 0, sib->end);
}

static inline
void cp_data_write(struct maple_copy *cp, struct ma_state *mas)
{
        struct maple_node *dst, *src;
        unsigned char s, d;
        unsigned char dst_offset;
        unsigned char data_offset;
        unsigned char src_end, s_offset;
        unsigned char split;
        unsigned long s_max, d_max;
        unsigned char dst_size;
        enum maple_type s_mt, d_mt;

        data_offset = 0;
        s = d = 0;
        /* Readability help */
        src = cp->src[s].node;
        dst = cp->dst[d].node;
        s_offset = cp->src[s].start;
        src_end = cp->src[s].end;
        split = cp->split;
        s_max = cp->src[s].max;
        s_mt = cp->src[s].mt;
        d_mt = cp->dst[d].mt;
        do {
                dst_offset = 0;
                d_max = 0;
                dst = cp->dst[d].node;
                d_mt = cp->dst[d].mt;
                dst_size = split + 1;

                while (dst_size) {
                        unsigned char size;

                        if (src_end - s_offset + 1 < dst_size)
                                size = src_end - s_offset + 1;
                        else
                                size = dst_size;

                        d_max = node_copy(mas, src, s_offset, size, s_max, s_mt,
                                          dst, dst_offset, d_mt);

                        dst_offset += size;
                        s_offset += size;
                        if (s_offset > src_end) {
                                /* This source is exhausted */
                                s++;
                                if (s >= cp->s_count) {
                                        cp->dst[d].max = d_max;
                                        node_finalise(dst, d_mt, dst_offset);
                                        return;
                                }
                                /* Reset local src */
                                src = cp->src[s].node;
                                s_offset = cp->src[s].start;
                                src_end = cp->src[s].end;
                                s_max = cp->src[s].max;
                                s_mt = cp->src[s].mt;
                        }

                        dst_size -= size;
                        data_offset += size;
                }

                split = cp->split;
                cp->dst[d].max = d_max;
                /* Handle null entries */
                if (cp->dst[d].max != ULONG_MAX &&
                    !ma_slots(dst, d_mt)[dst_offset - 1]) {
                        if (s_offset == cp->src[s].start) {
                                s--;
                                src = cp->src[s].node;
                                src_end = cp->src[s].end;
                                s_max = cp->src[s].max;
                                s_mt = cp->src[s].mt;
                                s_offset = src_end;
                        } else {
                                s_offset--;
                        }
                        /* Set dst max and clear pivot */
                        split++;
                        data_offset--;
                        dst_offset--;
                        cp->dst[d].max = ma_pivots(dst, d_mt)[dst_offset - 1];
                }

                node_finalise(dst, d_mt, dst_offset);
                ++d; /* Next destination */
                if (d == cp->d_count - 1)
                        split = cp->data - data_offset;

                if (d >= cp->d_count) {
                        WARN_ON(data_offset < cp->data);
                        return;
                }

        } while (data_offset <= cp->data);
}

/*
 * cp_dst_to_slots() - Migrate the maple copy destination to the maple copy
 * slots
 * @cp: The maple copy node
 * @min: The minimal value represented
 * @max: The maximum value represented
 * @mas: The maple state
 */
static inline void cp_dst_to_slots(struct maple_copy *cp, unsigned long min,
                unsigned long max, struct ma_state *mas)
{
        unsigned char d;
        unsigned long slot_min = min;

        for (d = 0; d < cp->d_count; d++) {
                struct maple_node *mn = cp->dst[d].node;
                enum maple_type mt = cp->dst[d].mt;
                unsigned long slot_max = cp->dst[d].max;

                /*
                 * Warning, see cp_leaf_init() comment and rcu_assign_pointer()
                 * documentation.  Since these are new nodes, there are no
                 * read-side operations that can view them until they are
                 * inserted into the tree after an rcu_assign_pointer() call.
                 */
                ma_init_slot(&cp->slot[d], mn, mt);
                cp->pivot[d] = slot_max;
                if (mt_is_alloc(mas->tree)) {
                        if (ma_is_leaf(mt)) {
                                cp->gap[d] = ma_leaf_max_gap(mn, mt, slot_min,
                                                 slot_max, ma_pivots(mn, mt),
                                                 ma_slots(mn, mt));
                        } else {
                                unsigned long *gaps = ma_gaps(mn, mt);

                                if (gaps) {
                                        unsigned char gap_slot;

                                        gap_slot = ma_meta_gap(mn);
                                        cp->gap[d] = gaps[gap_slot];
                                }
                        }
                }
                slot_min = slot_max + 1;
        }

        cp->end = cp->d_count - 1;
        cp->min = min;
        cp->max = max;
}

static inline bool cp_is_new_root(struct maple_copy *cp, struct ma_state *mas)
{
        if (cp->min || cp->max != ULONG_MAX)
                return false;

        if (cp->d_count != 1) {
                enum maple_type mt = maple_arange_64;

                if (!mt_is_alloc(mas->tree))
                        mt = maple_range_64;

                cp->data = cp->d_count;
                cp->s_count = 0;
                dst_setup(cp, mas, mt);
                init_cp_src(cp);
                node_copy(mas, cp->src[0].node, 0, cp->data, cp->max, maple_copy,
                          cp->dst[0].node, 0, mt);
                node_finalise(cp->dst[0].node, mt, cp->end + 1);
                /*
                 * Warning, see cp_leaf_init() comment and rcu_assign_pointer()
                 * documentation.  Since this is a new root, there are no
                 * read-side operations that can view it until it is insert into
                 * the tree after an rcu_assign_pointer() call.
                 */
                ma_init_slot(&cp->slot[0], cp->dst[0].node, mt);
                cp->height++;
        }
        WARN_ON_ONCE(cp->dst[0].node != mte_to_node(
                                mt_slot_locked(mas->tree, cp->slot, 0)));
        cp->dst[0].node->parent = ma_parent_ptr(mas_tree_parent(mas));
        mas->min = 0;
        mas->max = ULONG_MAX;
        mas->depth = 0;
        mas->node = mas_root_locked(mas);
        return true;
}

static inline bool cp_converged(struct maple_copy *cp, struct ma_state *mas,
                                struct ma_state *sib)
{
        if (cp->d_count != 1 || sib->end)
                return false;

        cp->dst[0].node->parent = ma_parent_ptr(mas_mn(mas)->parent);
        return true;
}

/*
 * spanning_ascend() - See if a spanning store operation has to keep walking up
 * the tree
 * @cp: The maple_copy node
 * @l_wr_mas: The left maple write state
 * @r_wr_mas: The right maple write state
 * @sib: the maple state of the sibling
 *
 * Returns: True if another iteration is necessary.
 */
static bool spanning_ascend(struct maple_copy *cp, struct ma_state *mas,
                            struct ma_wr_state *l_wr_mas, struct ma_wr_state *r_wr_mas,
                            struct ma_state *sib)
{
        if (sib->end) {
                if (sib->max < l_wr_mas->mas->min)
                        *l_wr_mas->mas = *sib;
                else
                        *r_wr_mas->mas = *sib;
        }

        cp_dst_to_slots(cp, l_wr_mas->mas->min, r_wr_mas->mas->max, mas);
        if (cp_is_new_root(cp, mas))
                return false;

        /* Converged and has a single destination */
        if ((cp->d_count == 1) &&
            (l_wr_mas->mas->node == r_wr_mas->mas->node)) {
                cp->dst[0].node->parent = ma_parent_ptr(mas_mn(mas)->parent);
                return false;
        }

        cp->height++;
        wr_mas_ascend(l_wr_mas);
        wr_mas_ascend(r_wr_mas);
        return true;
}

static inline
void copy_tree_location(const struct ma_state *src, struct ma_state *dst)
{
        dst->node = src->node;
        dst->offset = src->offset;
        dst->min = src->min;
        dst->max = src->max;
        dst->end = src->end;
        dst->depth = src->depth;
}

/*
 * rebalance_ascend() - Ascend the tree and set up for the next loop - if
 * necessary
 *
 * Return: True if there another rebalancing operation on the next level is
 * needed, false otherwise.
 */
static inline bool rebalance_ascend(struct maple_copy *cp,
                struct ma_wr_state *wr_mas, struct ma_state *sib,
                struct ma_state *parent)
{
        struct ma_state *mas;
        unsigned long min, max;

        mas = wr_mas->mas;
        if (!sib->end) {
                min = mas->min;
                max = mas->max;
        } else if (sib->min > mas->max) { /* Move right succeeded */
                min = mas->min;
                max = sib->max;
                wr_mas->offset_end = parent->offset + 1;
        } else {
                min = sib->min;
                max = mas->max;
                wr_mas->offset_end = parent->offset;
                parent->offset--;
        }

        cp_dst_to_slots(cp, min, max, mas);
        if (cp_is_new_root(cp, mas))
                return false;

        if (cp_converged(cp, mas, sib))
                return false;

        cp->height++;
        copy_tree_location(parent, mas);
        wr_mas_setup(wr_mas, mas);
        return true;
}

/*
 * mas_root_expand() - Expand a root to a node
 * @mas: The maple state
 * @entry: The entry to store into the tree
 */
static inline void 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;

        node = mas_pop_node(mas);
        pivots = ma_pivots(node, type);
        slots = ma_slots(node, type);
        node->parent = ma_parent_ptr(mas_tree_parent(mas));
        mas->node = mt_mk_node(node, type);
        mas->status = ma_active;

        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;

        mt_set_height(mas->tree, 1);
        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));
}

/*
 * mas_store_root() - Storing value into root.
 * @mas: The maple state
 * @entry: The entry to store.
 *
 * There is no root node now and we are storing a value into the root - this
 * function either assigns the pointer or expands into a node.
 */
static inline void mas_store_root(struct ma_state *mas, void *entry)
{
        if (!entry) {
                if (!mas->index)
                        rcu_assign_pointer(mas->tree->ma_root, NULL);
        } else 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->status = ma_start;
        }
}

/*
 * mas_is_span_wr() - Check if the write needs to be treated as a write that
 * spans the node.
 * @wr_mas: The maple write state
 *
 * 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 = wr_mas->r_max;
        unsigned long last = wr_mas->mas->last;
        enum maple_type type = wr_mas->type;
        void *entry = wr_mas->entry;

        /* Contained in this pivot, fast path */
        if (last < max)
                return false;

        if (ma_is_leaf(type)) {
                max = wr_mas->mas->max;
                if (last < max)
                        return false;
        }

        if (last == max) {
                /*
                 * The last entry of leaf node cannot be NULL unless it is the
                 * rightmost node (writing ULONG_MAX), otherwise it spans slots.
                 */
                if (entry || last == ULONG_MAX)
                        return false;
        }

        trace_ma_write(TP_FCT, wr_mas->mas, wr_mas->r_max, 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;

                if (mas->end < mt_slots[wr_mas->type] - 1)
                        wr_mas->vacant_height = mas->depth + 1;

                if (ma_is_root(mas_mn(mas))) {
                        /* root needs more than 2 entries to be sufficient + 1 */
                        if (mas->end > 2)
                                wr_mas->sufficient_height = 1;
                } else if (mas->end > mt_min_slots[wr_mas->type] + 1)
                        wr_mas->sufficient_height = mas->depth + 1;

                mas_wr_walk_traverse(wr_mas);
        }

        return true;
}

static void 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;
                mas_wr_walk_traverse(wr_mas);
        }
}
/*
 * 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;
                l_wr_mas->r_min = l_mas->index;
        }

        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++;
                r_wr_mas->r_max = r_mas->last;
        }
}

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;

        next = mas->node;
        do {
                node = mte_to_node(next);
                type = mte_node_type(next);
                pivots = ma_pivots(node, type);
                end = mt_pivots[type];
                offset = 0;
                do {
                        if (pivots[offset] >= mas->index)
                                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;
}

static void mte_destroy_walk(struct maple_enode *, struct maple_tree *);
/*
 * 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
 */
static inline void 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;

        WARN_ON_ONCE(mas->index || mas->last != ULONG_MAX);

        if (!entry) {
                mt_set_height(mas->tree, 0);
                rcu_assign_pointer(mas->tree->ma_root, entry);
                mas->status = ma_start;
                goto done;
        }

        node = mas_pop_node(mas);
        pivots = ma_pivots(node, type);
        slots = ma_slots(node, type);
        node->parent = ma_parent_ptr(mas_tree_parent(mas));
        mas->node = mt_mk_node(node, type);
        mas->status = ma_active;
        rcu_assign_pointer(slots[0], entry);
        pivots[0] = mas->last;
        mt_set_height(mas->tree, 1);
        rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));

done:
        if (xa_is_node(root))
                mte_destroy_walk(root, mas->tree);
}
/*
 * 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
 */
static void mas_wr_spanning_store(struct ma_wr_state *wr_mas)
{
        struct maple_copy cp;
        struct ma_state *mas;
        struct ma_state sib;

        /* Left and Right side of spanning store */
        MA_STATE(r_mas, NULL, 0, 0);
        MA_WR_STATE(r_wr_mas, &r_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(TP_FCT, 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.
         */

        /*
         * 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;
        r_wr_mas.end_piv = r_wr_mas.r_max;

        /* Set up left side. */
        mas_wr_walk_index(wr_mas);

        if (!wr_mas->entry) {
                mas_extend_spanning_null(wr_mas, &r_wr_mas);
                mas->last = r_mas.last;
        }

        /* expanding NULLs may make this cover the entire range */
        if (!mas->index && r_mas.last == ULONG_MAX) {
                mas_set_range(mas, 0, ULONG_MAX);
                return mas_new_root(mas, wr_mas->entry);
        }

        cp_leaf_init(&cp, mas, wr_mas, &r_wr_mas);
        do {
                spanning_data(&cp, wr_mas, &r_wr_mas, &sib);
                multi_src_setup(&cp, wr_mas, &r_wr_mas, &sib);
                dst_setup(&cp, mas, wr_mas->type);
                cp_data_write(&cp, mas);
        } while (spanning_ascend(&cp, mas, wr_mas, &r_wr_mas, &sib));

        mas_wmb_replace(mas, &cp);
}

/*
 * 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.
 */
static inline void mas_wr_node_store(struct ma_wr_state *wr_mas)
{
        unsigned char dst_offset, offset_end;
        unsigned char copy_size, node_pivots;
        struct maple_node reuse, *newnode;
        unsigned long *dst_pivots;
        void __rcu **dst_slots;
        unsigned char new_end;
        struct ma_state *mas;
        bool in_rcu;

        mas = wr_mas->mas;
        trace_ma_op(TP_FCT, mas);
        in_rcu = mt_in_rcu(mas->tree);
        offset_end = wr_mas->offset_end;
        node_pivots = mt_pivots[wr_mas->type];
        /* Assume last adds an entry */
        new_end = mas->end + 1 - offset_end + mas->offset;
        if (mas->last == wr_mas->end_piv) {
                offset_end++; /* don't copy this offset */
                new_end--;
        }

        /* set up node. */
        if (in_rcu) {
                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 */
        if (mas->offset) {
                memcpy(dst_pivots, wr_mas->pivots, sizeof(unsigned long) * mas->offset);
                memcpy(dst_slots, wr_mas->slots, sizeof(void __rcu *) * mas->offset);
        }

        /* Handle insert of new range starting after old range */
        if (wr_mas->r_min < mas->index) {
                rcu_assign_pointer(dst_slots[mas->offset], wr_mas->content);
                dst_pivots[mas->offset++] = mas->index - 1;
                new_end++;
        }

        /* Store the new entry and range end. */
        if (mas->offset < node_pivots)
                dst_pivots[mas->offset] = mas->last;
        rcu_assign_pointer(dst_slots[mas->offset], wr_mas->entry);

        /*
         * this range wrote to the end of the node or it overwrote the rest of
         * the data
         */
        if (offset_end > mas->end)
                goto done;

        dst_offset = mas->offset + 1;
        /* Copy to the end of node if necessary. */
        copy_size = mas->end - offset_end + 1;
        memcpy(dst_slots + dst_offset, wr_mas->slots + offset_end,
               sizeof(void __rcu *) * copy_size);
        memcpy(dst_pivots + dst_offset, wr_mas->pivots + offset_end,
               sizeof(unsigned long) * (copy_size - 1));

        if (new_end < node_pivots)
                dst_pivots[new_end] = mas->max;

done:
        mas_leaf_set_meta(newnode, maple_leaf_64, new_end);
        if (in_rcu) {
                struct maple_enode *old_enode = mas->node;

                mas->node = mt_mk_node(newnode, wr_mas->type);
                mas_replace_node(mas, old_enode, mas_mt_height(mas));
        } else {
                memcpy(wr_mas->node, newnode, sizeof(struct maple_node));
        }
        trace_ma_write(TP_FCT, mas, 0, wr_mas->entry);
        mas_update_gap(mas);
        mas->end = new_end;
}

/*
 * mas_wr_slot_store: Attempt to store a value in a slot.
 * @wr_mas: the maple write state
 */
static inline void mas_wr_slot_store(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;
        unsigned char offset = mas->offset;
        void __rcu **slots = wr_mas->slots;
        bool gap = false;

        gap |= !mt_slot_locked(mas->tree, slots, offset);
        gap |= !mt_slot_locked(mas->tree, slots, offset + 1);

        if (wr_mas->offset_end - offset == 1) {
                if (mas->index == wr_mas->r_min) {
                        /* Overwriting the range and a part of the next one */
                        rcu_assign_pointer(slots[offset], wr_mas->entry);
                        wr_mas->pivots[offset] = mas->last;
                } else {
                        /* Overwriting a part of the range and the next one */
                        rcu_assign_pointer(slots[offset + 1], wr_mas->entry);
                        wr_mas->pivots[offset] = mas->index - 1;
                        mas->offset++; /* Keep mas accurate. */
                }
        } else {
                WARN_ON_ONCE(mt_in_rcu(mas->tree));
                /*
                 * Expand the range, only partially overwriting the previous and
                 * next ranges
                 */
                gap |= !mt_slot_locked(mas->tree, slots, offset + 2);
                rcu_assign_pointer(slots[offset + 1], wr_mas->entry);
                wr_mas->pivots[offset] = mas->index - 1;
                wr_mas->pivots[offset + 1] = mas->last;
                mas->offset++; /* Keep mas accurate. */
        }

        trace_ma_write(TP_FCT, mas, 0, wr_mas->entry);
        /*
         * Only update gap when the new entry is empty or there is an empty
         * entry in the original two ranges.
         */
        if (!wr_mas->entry || gap)
                mas_update_gap(mas);
}

static inline void mas_wr_extend_null(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;

        if (!wr_mas->slots[wr_mas->offset_end]) {
                /* If this one is null, the next and prev are not */
                mas->last = wr_mas->end_piv;
        } else {
                /* Check next slot(s) if we are overwriting the end */
                if ((mas->last == wr_mas->end_piv) &&
                    (mas->end != wr_mas->offset_end) &&
                    !wr_mas->slots[wr_mas->offset_end + 1]) {
                        wr_mas->offset_end++;
                        if (wr_mas->offset_end == mas->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 void mas_wr_end_piv(struct ma_wr_state *wr_mas)
{
        while ((wr_mas->offset_end < wr_mas->mas->end) &&
               (wr_mas->mas->last > wr_mas->pivots[wr_mas->offset_end]))
                wr_mas->offset_end++;

        if (wr_mas->offset_end < wr_mas->mas->end)
                wr_mas->end_piv = wr_mas->pivots[wr_mas->offset_end];
        else
                wr_mas->end_piv = wr_mas->mas->max;
}

static inline unsigned char mas_wr_new_end(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;
        unsigned char new_end = mas->end + 2;

        new_end -= wr_mas->offset_end - mas->offset;
        if (wr_mas->r_min == mas->index)
                new_end--;

        if (wr_mas->end_piv == mas->last)
                new_end--;

        return new_end;
}

/*
 * mas_wr_append: Attempt to append
 * @wr_mas: the maple write state
 *
 * This is currently unsafe in rcu mode since the end of the node may be cached
 * by readers while the node contents may be updated which could result in
 * inaccurate information.
 */
static inline void mas_wr_append(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;
        void __rcu **slots;
        unsigned char end = mas->end;
        unsigned char new_end = mas_wr_new_end(wr_mas);

        if (new_end < mt_pivots[wr_mas->type]) {
                wr_mas->pivots[new_end] = wr_mas->pivots[end];
                ma_set_meta(wr_mas->node, wr_mas->type, 0, new_end);
        }

        slots = wr_mas->slots;
        if (new_end == end + 1) {
                if (mas->last == wr_mas->r_max) {
                        /* Append to end of range */
                        rcu_assign_pointer(slots[new_end], wr_mas->entry);
                        wr_mas->pivots[end] = mas->index - 1;
                        mas->offset = new_end;
                } else {
                        /* Append to start of range */
                        rcu_assign_pointer(slots[new_end], wr_mas->content);
                        wr_mas->pivots[end] = mas->last;
                        rcu_assign_pointer(slots[end], wr_mas->entry);
                }
        } else {
                /* Append to the range without touching any boundaries. */
                rcu_assign_pointer(slots[new_end], wr_mas->content);
                wr_mas->pivots[end + 1] = mas->last;
                rcu_assign_pointer(slots[end + 1], wr_mas->entry);
                wr_mas->pivots[end] = mas->index - 1;
                mas->offset = end + 1;
        }

        if (!wr_mas->content || !wr_mas->entry)
                mas_update_gap(mas);

        mas->end = new_end;
        trace_ma_write(TP_FCT, mas, new_end, wr_mas->entry);
}

/*
 * split_ascend() - See if a split operation has to keep walking up the tree
 * @cp: The maple_copy node
 * @wr_mas: The maple write state
 * @sib: the maple state of the sibling
 *
 * Return: true if another split operation on the next level is needed, false
 * otherwise
 */
static inline bool split_ascend(struct maple_copy *cp,
                struct ma_wr_state *wr_mas, struct ma_state *sib,
                struct ma_state *parent)
{
        struct ma_state *mas;
        unsigned long min, max;

        mas = wr_mas->mas;
        min = mas->min; /* push right, or normal split */
        max = mas->max;
        wr_mas->offset_end = parent->offset;
        if (sib->end) {
                if (sib->max < mas->min) {
                        min = sib->min; /* push left */
                        parent->offset--;
                } else {
                        max = sib->max; /* push right */
                        wr_mas->offset_end++;
                }
        }

        cp_dst_to_slots(cp, min, max, mas);
        if (cp_is_new_root(cp, mas))
                return false;

        if (cp_converged(cp, mas, sib))
                return false;

        cp->height++;
        copy_tree_location(parent, mas);
        wr_mas_setup(wr_mas, mas);
        return true;
}

/*
 * split_data() - Calculate the @cp data, populate @sib if the data can be
 * pushed into a sibling.
 * @cp: The maple copy node
 * @wr_mas: The left write maple state
 * @sib: The maple state of the sibling.
 *
 * Note: @cp->data is a size and not indexed by 0. @sib->end may be set to 0 to
 * indicate it will not be used.
 *
 */
static inline void split_data(struct maple_copy *cp,
                struct ma_wr_state *wr_mas, struct ma_state *sib,
                struct ma_state *parent)
{
        cp_data_calc(cp, wr_mas, wr_mas);
        if (cp->data <= mt_slots[wr_mas->type]) {
                sib->end = 0;
                return;
        }

        push_data_sib(cp, wr_mas->mas, sib, parent);
        if (sib->end)
                cp->data += sib->end + 1;
}

/*
 * mas_wr_split() - Expand one node into two
 * @wr_mas: The write maple state
 */
static void mas_wr_split(struct ma_wr_state *wr_mas)
{
        struct ma_state parent;
        struct ma_state *mas;
        struct maple_copy cp;
        struct ma_state sib;

        mas = wr_mas->mas;
        trace_ma_write(TP_FCT, wr_mas->mas, 0, wr_mas->entry);
        parent = *mas;
        cp_leaf_init(&cp, mas, wr_mas, wr_mas);
        do {
                if (!mte_is_root(parent.node)) {
                        mas_ascend(&parent);
                        parent.end = mas_data_end(&parent);
                }
                split_data(&cp, wr_mas, &sib, &parent);
                multi_src_setup(&cp, wr_mas, wr_mas, &sib);
                dst_setup(&cp, mas, wr_mas->type);
                cp_data_write(&cp, mas);
        } while (split_ascend(&cp, wr_mas, &sib, &parent));

        mas_wmb_replace(mas, &cp);
}

/*
 * mas_wr_rebalance() - Insufficient data in one node needs to either get data
 * from a sibling or absorb a sibling all together.
 * @wr_mas: The write maple state
 *
 * Rebalance is different than a spanning store in that the write state is
 * already at the leaf node that's being altered.
 */
static void mas_wr_rebalance(struct ma_wr_state *wr_mas)
{
        struct ma_state parent;
        struct ma_state *mas;
        struct maple_copy cp;
        struct ma_state sib;

        /*
         * 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 = wr_mas->mas;
        trace_ma_op(TP_FCT, mas);
        parent = *mas;
        cp_leaf_init(&cp, mas, wr_mas, wr_mas);
        do {
                if (!mte_is_root(parent.node)) {
                        mas_ascend(&parent);
                        parent.end = mas_data_end(&parent);
                }
                rebalance_data(&cp, wr_mas, &sib, &parent);
                multi_src_setup(&cp, wr_mas, wr_mas, &sib);
                dst_setup(&cp, mas, wr_mas->type);
                cp_data_write(&cp, mas);
        } while (rebalance_ascend(&cp, wr_mas, &sib, &parent));

        mas_wmb_replace(mas, &cp);
}

/*
 * mas_wr_store_entry() - Internal call to store a value
 * @wr_mas: The maple write state
 */
static inline void mas_wr_store_entry(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;

        switch (mas->store_type) {
        case wr_exact_fit:
                rcu_assign_pointer(wr_mas->slots[mas->offset], wr_mas->entry);
                if (!!wr_mas->entry ^ !!wr_mas->content)
                        mas_update_gap(mas);
                break;
        case wr_append:
                mas_wr_append(wr_mas);
                break;
        case wr_slot_store:
                mas_wr_slot_store(wr_mas);
                break;
        case wr_node_store:
                mas_wr_node_store(wr_mas);
                break;
        case wr_spanning_store:
                mas_wr_spanning_store(wr_mas);
                break;
        case wr_split_store:
                mas_wr_split(wr_mas);
                break;
        case wr_rebalance:
                mas_wr_rebalance(wr_mas);
                break;
        case wr_new_root:
                mas_new_root(mas, wr_mas->entry);
                break;
        case wr_store_root:
                mas_store_root(mas, wr_mas->entry);
                break;
        case wr_invalid:
                MT_BUG_ON(mas->tree, 1);
        }
}

static inline void mas_wr_prealloc_setup(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;

        if (!mas_is_active(mas)) {
                if (mas_is_start(mas))
                        goto set_content;

                if (unlikely(mas_is_paused(mas)))
                        goto reset;

                if (unlikely(mas_is_none(mas)))
                        goto reset;

                if (unlikely(mas_is_overflow(mas)))
                        goto reset;

                if (unlikely(mas_is_underflow(mas)))
                        goto reset;
        }

        /*
         * A less strict version of mas_is_span_wr() where we allow spanning
         * writes within this node.  This is to stop partial walks in
         * mas_prealloc() from being reset.
         */
        if (mas->last > mas->max)
                goto reset;

        if (wr_mas->entry)
                goto set_content;

        if (mte_is_leaf(mas->node) && mas->last == mas->max)
                goto reset;

        goto set_content;

reset:
        mas_reset(mas);
set_content:
        wr_mas->content = mas_start(mas);
}

/**
 * mas_prealloc_calc() - Calculate number of nodes needed for a
 * given store oepration
 * @wr_mas: The maple write state
 * @entry: The entry to store into the tree
 *
 * Return: Number of nodes required for preallocation.
 */
static inline void mas_prealloc_calc(struct ma_wr_state *wr_mas, void *entry)
{
        struct ma_state *mas = wr_mas->mas;
        unsigned char height = mas_mt_height(mas);
        int ret = height * 3 + 1;
        unsigned char delta = height - wr_mas->vacant_height;

        switch (mas->store_type) {
        case wr_exact_fit:
        case wr_append:
        case wr_slot_store:
                ret = 0;
                break;
        case wr_spanning_store:
                if (wr_mas->sufficient_height < wr_mas->vacant_height)
                        ret = (height - wr_mas->sufficient_height) * 3 + 1;
                else
                        ret = delta * 3 + 1;
                break;
        case wr_split_store:
                ret = delta * 2 + 1;
                break;
        case wr_rebalance:
                if (wr_mas->sufficient_height < wr_mas->vacant_height)
                        ret = (height - wr_mas->sufficient_height) * 2 + 1;
                else
                        ret = delta * 2 + 1;
                break;
        case wr_node_store:
                ret = mt_in_rcu(mas->tree) ? 1 : 0;
                break;
        case wr_new_root:
                ret = 1;
                break;
        case wr_store_root:
                if (likely((mas->last != 0) || (mas->index != 0)))
                        ret = 1;
                else if (((unsigned long) (entry) & 3) == 2)
                        ret = 1;
                else
                        ret = 0;
                break;
        case wr_invalid:
                WARN_ON_ONCE(1);
        }

        mas->node_request = ret;
}

/*
 * mas_wr_store_type() - Determine the store type for a given
 * store operation.
 * @wr_mas: The maple write state
 *
 * Return: the type of store needed for the operation
 */
static inline enum store_type mas_wr_store_type(struct ma_wr_state *wr_mas)
{
        struct ma_state *mas = wr_mas->mas;
        unsigned char new_end;

        if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))
                return wr_store_root;

        if (unlikely(!mas_wr_walk(wr_mas)))
                return wr_spanning_store;

        /* 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);

        if ((wr_mas->r_min == mas->index) && (wr_mas->r_max == mas->last))
                return wr_exact_fit;

        if (unlikely(!mas->index && mas->last == ULONG_MAX))
                return wr_new_root;

        new_end = mas_wr_new_end(wr_mas);
        /* Potential spanning rebalance collapsing a node */
        if (new_end < mt_min_slots[wr_mas->type]) {
                if (!mte_is_root(mas->node))
                        return  wr_rebalance;
                return wr_node_store;
        }

        if (new_end >= mt_slots[wr_mas->type])
                return wr_split_store;

        if (!mt_in_rcu(mas->tree) && (mas->offset == mas->end))
                return wr_append;

        if ((new_end == mas->end) && (!mt_in_rcu(mas->tree) ||
                (wr_mas->offset_end - mas->offset == 1)))
                return wr_slot_store;

        return wr_node_store;
}

/**
 * mas_wr_preallocate() - Preallocate enough nodes for a store operation
 * @wr_mas: The maple write state
 * @entry: The entry that will be stored
 *
 */
static inline void mas_wr_preallocate(struct ma_wr_state *wr_mas, void *entry)
{
        struct ma_state *mas = wr_mas->mas;

        mas_wr_prealloc_setup(wr_mas);
        mas->store_type = mas_wr_store_type(wr_mas);
        mas_prealloc_calc(wr_mas, entry);
        if (!mas->node_request)
                return;

        mas_alloc_nodes(mas, GFP_NOWAIT);
}

/**
 * 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;

        mas_wr_preallocate(&wr_mas, entry);
        if (mas_is_err(mas))
                return NULL;

        /* spanning writes always overwrite something */
        if (mas->store_type == wr_spanning_store)
                goto exists;

        /* At this point, we are at the leaf node that needs to be altered. */
        if (mas->store_type != wr_new_root && mas->store_type != wr_store_root) {
                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;
        }

        mas_wr_store_entry(&wr_mas);
        return wr_mas.content;

exists:
        mas_set_err(mas, -EEXIST);
        return wr_mas.content;

}

/**
 * mas_alloc_cyclic() - Internal call to find somewhere to store an entry
 * @mas: The maple state.
 * @startp: Pointer to ID.
 * @range_lo: Lower bound of range to search.
 * @range_hi: Upper bound of range to search.
 * @entry: The entry to store.
 * @next: Pointer to next ID to allocate.
 * @gfp: The GFP_FLAGS to use for allocations.
 *
 * Return: 0 if the allocation succeeded without wrapping, 1 if the
 * allocation succeeded after wrapping, or -EBUSY if there are no
 * free entries.
 */
int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp,
                void *entry, unsigned long range_lo, unsigned long range_hi,
                unsigned long *next, gfp_t gfp)
{
        unsigned long min = range_lo;
        int ret = 0;

        range_lo = max(min, *next);
        ret = mas_empty_area(mas, range_lo, range_hi, 1);
        if ((mas->tree->ma_flags & MT_FLAGS_ALLOC_WRAPPED) && ret == 0) {
                mas->tree->ma_flags &= ~MT_FLAGS_ALLOC_WRAPPED;
                ret = 1;
        }
        if (ret < 0 && range_lo > min) {
                mas_reset(mas);
                ret = mas_empty_area(mas, min, range_hi, 1);
                if (ret == 0)
                        ret = 1;
        }
        if (ret < 0)
                return ret;

        do {
                mas_insert(mas, entry);
        } while (mas_nomem(mas, gfp));
        if (mas_is_err(mas))
                return xa_err(mas->node);

        *startp = mas->index;
        *next = *startp + 1;
        if (*next == 0)
                mas->tree->ma_flags |= MT_FLAGS_ALLOC_WRAPPED;

        mas_destroy(mas);
        return ret;
}
EXPORT_SYMBOL(mas_alloc_cyclic);

static __always_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;
}

static __always_inline bool mas_rewalk_if_dead(struct ma_state *mas,
                struct maple_node *node, const unsigned long index)
{
        if (unlikely(ma_dead_node(node))) {
                mas_rewalk(mas, index);
                return true;
        }
        return false;
}

/*
 * 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 the status will be
 * ma_none.
 * @mas: The maple state
 * @min: The lower limit to search
 *
 * The prev node value will be mas->node[mas->offset] or the status will be
 * ma_none.
 * Return: 1 if the node is dead, 0 otherwise.
 */
static 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;
        unsigned long *pivots;
        unsigned long max;

        node = mas_mn(mas);
        if (!mas->min)
                goto no_entry;

        max = mas->min - 1;
        if (max < min)
                goto no_entry;

        level = 0;
        do {
                if (ma_is_root(node))
                        goto no_entry;

                /* Walk up. */
                if (unlikely(mas_ascend(mas)))
                        return 1;
                offset = mas->offset;
                level++;
                node = mas_mn(mas);
        } while (!offset);

        offset--;
        mt = mte_node_type(mas->node);
        while (level > 1) {
                level--;
                slots = ma_slots(node, mt);
                mas->node = mas_slot(mas, slots, offset);
                if (unlikely(ma_dead_node(node)))
                        return 1;

                mt = mte_node_type(mas->node);
                node = mas_mn(mas);
                pivots = ma_pivots(node, mt);
                offset = ma_data_end(node, mt, pivots, max);
                if (unlikely(ma_dead_node(node)))
                        return 1;
        }

        slots = ma_slots(node, mt);
        mas->node = mas_slot(mas, slots, offset);
        pivots = ma_pivots(node, mt);
        if (unlikely(ma_dead_node(node)))
                return 1;

        if (likely(offset))
                mas->min = pivots[offset - 1] + 1;
        mas->max = max;
        mas->offset = mas_data_end(mas);
        if (unlikely(mte_dead_node(mas->node)))
                return 1;

        mas->end = mas->offset;
        return 0;

no_entry:
        if (unlikely(ma_dead_node(node)))
                return 1;

        mas->status = ma_underflow;
        return 0;
}

/*
 * mas_prev_slot() - Get the entry in the previous slot
 *
 * @mas: The maple state
 * @min: The minimum starting range
 * @empty: Can be empty
 *
 * Return: The entry in the previous slot which is possibly NULL
 */
static void *mas_prev_slot(struct ma_state *mas, unsigned long min, bool empty)
{
        void *entry;
        void __rcu **slots;
        unsigned long pivot;
        enum maple_type type;
        unsigned long *pivots;
        struct maple_node *node;
        unsigned long save_point = mas->index;

retry:
        node = mas_mn(mas);
        type = mte_node_type(mas->node);
        pivots = ma_pivots(node, type);
        if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                goto retry;

        if (mas->min <= min) {
                pivot = mas_safe_min(mas, pivots, mas->offset);

                if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                        goto retry;

                if (pivot <= min)
                        goto underflow;
        }

again:
        if (likely(mas->offset)) {
                mas->offset--;
                mas->last = mas->index - 1;
                mas->index = mas_safe_min(mas, pivots, mas->offset);
        } else  {
                if (mas->index <= min)
                        goto underflow;

                if (mas_prev_node(mas, min)) {
                        mas_rewalk(mas, save_point);
                        goto retry;
                }

                if (WARN_ON_ONCE(mas_is_underflow(mas)))
                        return NULL;

                mas->last = mas->max;
                node = mas_mn(mas);
                type = mte_node_type(mas->node);
                pivots = ma_pivots(node, type);
                mas->index = pivots[mas->offset - 1] + 1;
        }

        slots = ma_slots(node, type);
        entry = mas_slot(mas, slots, mas->offset);
        if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                goto retry;

        if (likely(entry))
                return entry;

        if (!empty) {
                if (mas->index <= min)
                        goto underflow;

                goto again;
        }

        return entry;

underflow:
        mas->status = ma_underflow;
        return NULL;
}

/*
 * mas_next_node() - Get the next node at the same level in the tree.
 * @mas: The maple state
 * @node: The maple node
 * @max: The maximum pivot value to check.
 *
 * The next value will be mas->node[mas->offset] or the status will have
 * overflowed.
 * Return: 1 on dead node, 0 otherwise.
 */
static int mas_next_node(struct ma_state *mas, struct maple_node *node,
                unsigned long max)
{
        unsigned long min;
        unsigned long *pivots;
        struct maple_enode *enode;
        struct maple_node *tmp;
        int level = 0;
        unsigned char node_end;
        enum maple_type mt;
        void __rcu **slots;

        if (mas->max >= max)
                goto overflow;

        min = mas->max + 1;
        level = 0;
        do {
                if (ma_is_root(node))
                        goto overflow;

                /* Walk up. */
                if (unlikely(mas_ascend(mas)))
                        return 1;

                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(mas->offset == node_end));

        slots = ma_slots(node, mt);
        mas->offset++;
        enode = mas_slot(mas, slots, mas->offset);
        if (unlikely(ma_dead_node(node)))
                return 1;

        if (level > 1)
                mas->offset = 0;

        while (unlikely(level > 1)) {
                level--;
                mas->node = enode;
                node = mas_mn(mas);
                mt = mte_node_type(mas->node);
                slots = ma_slots(node, mt);
                enode = mas_slot(mas, slots, 0);
                if (unlikely(ma_dead_node(node)))
                        return 1;
        }

        if (!mas->offset)
                pivots = ma_pivots(node, mt);

        mas->max = mas_safe_pivot(mas, pivots, mas->offset, mt);
        tmp = mte_to_node(enode);
        mt = mte_node_type(enode);
        pivots = ma_pivots(tmp, mt);
        mas->end = ma_data_end(tmp, mt, pivots, mas->max);
        if (unlikely(ma_dead_node(node)))
                return 1;

        mas->node = enode;
        mas->min = min;
        return 0;

overflow:
        if (unlikely(ma_dead_node(node)))
                return 1;

        mas->status = ma_overflow;
        return 0;
}

/*
 * mas_next_slot() - Get the entry in the next slot
 *
 * @mas: The maple state
 * @max: The maximum starting range
 * @empty: Can be empty
 *
 * Return: The entry in the next slot which is possibly NULL
 */
static void *mas_next_slot(struct ma_state *mas, unsigned long max, bool empty)
{
        void __rcu **slots;
        unsigned long *pivots;
        unsigned long pivot;
        enum maple_type type;
        struct maple_node *node;
        unsigned long save_point = mas->last;
        void *entry;

retry:
        node = mas_mn(mas);
        type = mte_node_type(mas->node);
        pivots = ma_pivots(node, type);
        if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                goto retry;

        if (mas->max >= max) {
                if (likely(mas->offset < mas->end))
                        pivot = pivots[mas->offset];
                else
                        pivot = mas->max;

                if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                        goto retry;

                if (pivot >= max) { /* Was at the limit, next will extend beyond */
                        mas->status = ma_overflow;
                        return NULL;
                }
        }

        if (likely(mas->offset < mas->end)) {
                mas->index = pivots[mas->offset] + 1;
again:
                mas->offset++;
                if (likely(mas->offset < mas->end))
                        mas->last = pivots[mas->offset];
                else
                        mas->last = mas->max;
        } else  {
                if (mas->last >= max) {
                        mas->status = ma_overflow;
                        return NULL;
                }

                if (mas_next_node(mas, node, max)) {
                        mas_rewalk(mas, save_point);
                        goto retry;
                }

                if (WARN_ON_ONCE(mas_is_overflow(mas)))
                        return NULL;

                mas->offset = 0;
                mas->index = mas->min;
                node = mas_mn(mas);
                type = mte_node_type(mas->node);
                pivots = ma_pivots(node, type);
                mas->last = pivots[0];
        }

        slots = ma_slots(node, type);
        entry = mt_slot(mas->tree, slots, mas->offset);
        if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
                goto retry;

        if (entry)
                return entry;


        if (!empty) {
                if (mas->last >= max) {
                        mas->status = ma_overflow;
                        return NULL;
                }

                mas->index = mas->last + 1;
                goto again;
        }

        return entry;
}

/*
 * 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_safe_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;
                                break;
                        }

                        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;
                }
        }

        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->status is ma_none, reset to ma_start
 *
 * Return: the entry at the location or %NULL.
 */
void *mas_walk(struct ma_state *mas)
{
        void *entry;

        if (!mas_is_active(mas) && !mas_is_start(mas))
                mas->status = ma_start;
retry:
        entry = mas_state_walk(mas);
        if (mas_is_start(mas)) {
                goto retry;
        } else if (mas_is_none(mas)) {
                mas->index = 0;
                mas->last = ULONG_MAX;
        } else if (mas_is_ptr(mas)) {
                if (!mas->index) {
                        mas->last = 0;
                        return entry;
                }

                mas->index = 1;
                mas->last = ULONG_MAX;
                mas->status = ma_none;
                return NULL;
        }

        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, error == -EBUSY)
         * found the gap. (return)
         */
        while (!mas_is_err(mas) && !mas_anode_descend(mas, size)) {
                if (last == mas->node)
                        mas_skip_node(mas);
                else
                        last = mas->node;
        }
}

/*
 * 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 int mas_sparse_area(struct ma_state *mas, unsigned long min,
                                unsigned long max, unsigned long size, bool fwd)
{
        if (!unlikely(mas_is_none(mas)) && min == 0) {
                min++;
                /*
                 * At this time, min is increased, we need to recheck whether
                 * the size is satisfied.
                 */
                if (min > max || max - min + 1 < size)
                        return -EBUSY;
        }
        /* mas_is_ptr */

        if (fwd) {
                mas->index = min;
                mas->last = min + size - 1;
        } else {
                mas->last = max;
                mas->index = max - size + 1;
        }
        return 0;
}

/*
 * 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;
        struct maple_node *node;

        if (min > max)
                return -EINVAL;

        if (size == 0 || max - min < size - 1)
                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))
                return mas_sparse_area(mas, min, max, size, true);

        /* 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;
        node = mas_mn(mas);
        mt = mte_node_type(mas->node);
        pivots = ma_pivots(node, mt);
        min = mas_safe_min(mas, pivots, offset);
        if (mas->index < min)
                mas->index = min;
        mas->last = mas->index + size - 1;
        mas->end = ma_data_end(node, mt, pivots, mas->max);
        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 (size == 0 || max - min < size - 1)
                return -EINVAL;

        if (mas_is_start(mas))
                mas_start(mas);
        else if ((mas->offset < 2) && (!mas_rewind_node(mas)))
                return -EBUSY;

        if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))
                return mas_sparse_area(mas, min, max, size, false);
        else if (mas->offset >= 2)
                mas->offset -= 2;
        else
                mas->offset = mas_data_end(mas);


        /* 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;
        mas->end = mas_data_end(mas);
        return 0;
}
EXPORT_SYMBOL_GPL(mas_empty_area_rev);

/*
 * mte_dead_leaves() - Mark all leaves of a node as dead.
 * @enode: the encoded node
 * @mt: the maple tree
 * @slots: Pointer to the slot array
 *
 * 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:
        kfree(node);
}

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)) {
                mte_set_node_dead(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)
                kfree(node);
        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
 * @mt: 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);
        }
}
/* 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.
 *
 * 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(TP_FCT, mas, 0, entry);
#ifdef CONFIG_DEBUG_MAPLE_TREE
        if (MAS_WARN_ON(mas, mas->index > mas->last))
                pr_err("Error %lX > %lX " PTR_FMT "\n", mas->index, mas->last,
                       entry);

        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_prealloc_setup(&wr_mas);
        mas->store_type = mas_wr_store_type(&wr_mas);
        if (mas->mas_flags & MA_STATE_PREALLOC) {
                mas_wr_store_entry(&wr_mas);
                MAS_WR_BUG_ON(&wr_mas, mas_is_err(mas));
                return wr_mas.content;
        }

        mas_prealloc_calc(&wr_mas, entry);
        if (!mas->node_request)
                goto store;

        mas_alloc_nodes(mas, GFP_NOWAIT);
        if (mas_is_err(mas))
                return NULL;

store:
        mas_wr_store_entry(&wr_mas);
        mas_destroy(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)
{
        unsigned long index = mas->index;
        unsigned long last = mas->last;
        MA_WR_STATE(wr_mas, mas, entry);
        int ret = 0;

retry:
        mas_wr_preallocate(&wr_mas, entry);
        if (unlikely(mas_nomem(mas, gfp))) {
                if (!entry)
                        __mas_set_range(mas, index, last);
                goto retry;
        }

        if (mas_is_err(mas)) {
                ret = xa_err(mas->node);
                goto out;
        }

        mas_wr_store_entry(&wr_mas);
out:
        mas_destroy(mas);
        return ret;
}
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);

        if (mas->store_type == wr_store_root) {
                mas_wr_prealloc_setup(&wr_mas);
                goto store;
        }

        mas_wr_walk_descend(&wr_mas);
        if (mas->store_type != wr_spanning_store) {
                /* set wr_mas->content to current slot */
                wr_mas.content = mas_slot_locked(mas, wr_mas.slots, mas->offset);
                mas_wr_end_piv(&wr_mas);
        }

store:
        trace_ma_write(TP_FCT, mas, 0, entry);
        mas_wr_store_entry(&wr_mas);
        MAS_WR_BUG_ON(&wr_mas, 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)
{
        MA_WR_STATE(wr_mas, mas, entry);

        mas_wr_prealloc_setup(&wr_mas);
        mas->store_type = mas_wr_store_type(&wr_mas);
        mas_prealloc_calc(&wr_mas, entry);
        if (!mas->node_request)
                goto set_flag;

        mas->mas_flags &= ~MA_STATE_PREALLOC;
        mas_alloc_nodes(mas, gfp);
        if (mas_is_err(mas)) {
                int ret = xa_err(mas->node);

                mas->node_request = 0;
                mas_destroy(mas);
                mas_reset(mas);
                return ret;
        }

set_flag:
        mas->mas_flags |= MA_STATE_PREALLOC;
        return 0;
}
EXPORT_SYMBOL_GPL(mas_preallocate);

/*
 * 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)
{
        mas->mas_flags &= ~MA_STATE_PREALLOC;
        mas_empty_nodes(mas);
}
EXPORT_SYMBOL_GPL(mas_destroy);

static void mas_may_activate(struct ma_state *mas)
{
        if (!mas->node) {
                mas->status = ma_start;
        } else if (mas->index > mas->max || mas->index < mas->min) {
                mas->status = ma_start;
        } else {
                mas->status = ma_active;
        }
}

static bool mas_next_setup(struct ma_state *mas, unsigned long max,
                void **entry)
{
        bool was_none = mas_is_none(mas);

        if (unlikely(mas->last >= max)) {
                mas->status = ma_overflow;
                return true;
        }

        switch (mas->status) {
        case ma_active:
                return false;
        case ma_none:
                fallthrough;
        case ma_pause:
                mas->status = ma_start;
                fallthrough;
        case ma_start:
                mas_walk(mas); /* Retries on dead nodes handled by mas_walk */
                break;
        case ma_overflow:
                /* Overflowed before, but the max changed */
                mas_may_activate(mas);
                break;
        case ma_underflow:
                /* The user expects the mas to be one before where it is */
                mas_may_activate(mas);
                *entry = mas_walk(mas);
                if (*entry)
                        return true;
                break;
        case ma_root:
                break;
        case ma_error:
                return true;
        }

        if (likely(mas_is_active(mas))) /* Fast path */
                return false;

        if (mas_is_ptr(mas)) {
                *entry = NULL;
                if (was_none && mas->index == 0) {
                        mas->index = mas->last = 0;
                        return true;
                }
                mas->index = 1;
                mas->last = ULONG_MAX;
                mas->status = ma_none;
                return true;
        }

        if (mas_is_none(mas))
                return true;

        return false;
}

/**
 * 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)
{
        void *entry = NULL;

        if (mas_next_setup(mas, max, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_next_slot */
        return mas_next_slot(mas, max, false);
}
EXPORT_SYMBOL_GPL(mas_next);

/**
 * mas_next_range() - Advance the maple state to the next range
 * @mas: The maple state
 * @max: The maximum index to check.
 *
 * Sets @mas->index and @mas->last to the range.
 * Must hold rcu_read_lock or the write lock.
 * Can return the zero entry.
 *
 * Return: The next entry or %NULL
 */
void *mas_next_range(struct ma_state *mas, unsigned long max)
{
        void *entry = NULL;

        if (mas_next_setup(mas, max, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_next_slot */
        return mas_next_slot(mas, max, true);
}
EXPORT_SYMBOL_GPL(mas_next_range);

/**
 * mt_next() - get the next value in the maple tree
 * @mt: The maple tree
 * @index: The start index
 * @max: The maximum index to check
 *
 * Takes RCU read lock internally to protect the search, which does not
 * protect the returned pointer after dropping RCU read lock.
 * See also: Documentation/core-api/maple_tree.rst
 *
 * Return: The entry higher than @index 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);

static bool mas_prev_setup(struct ma_state *mas, unsigned long min, void **entry)
{
        if (unlikely(mas->index <= min)) {
                mas->status = ma_underflow;
                return true;
        }

        switch (mas->status) {
        case ma_active:
                return false;
        case ma_start:
                break;
        case ma_none:
                fallthrough;
        case ma_pause:
                mas->status = ma_start;
                break;
        case ma_underflow:
                /* underflowed before but the min changed */
                mas_may_activate(mas);
                break;
        case ma_overflow:
                /* User expects mas to be one after where it is */
                mas_may_activate(mas);
                *entry = mas_walk(mas);
                if (*entry)
                        return true;
                break;
        case ma_root:
                break;
        case ma_error:
                return true;
        }

        if (mas_is_start(mas))
                mas_walk(mas);

        if (unlikely(mas_is_ptr(mas))) {
                if (!mas->index) {
                        mas->status = ma_none;
                        return true;
                }
                mas->index = mas->last = 0;
                *entry = mas_root(mas);
                return true;
        }

        if (mas_is_none(mas)) {
                if (mas->index) {
                        /* Walked to out-of-range pointer? */
                        mas->index = mas->last = 0;
                        mas->status = ma_root;
                        *entry = mas_root(mas);
                        return true;
                }
                return true;
        }

        return false;
}

/**
 * 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 ma_start if the status is ma_none.  Will stop on not
 * searchable nodes.
 *
 * Return: the previous value or %NULL.
 */
void *mas_prev(struct ma_state *mas, unsigned long min)
{
        void *entry = NULL;

        if (mas_prev_setup(mas, min, &entry))
                return entry;

        return mas_prev_slot(mas, min, false);
}
EXPORT_SYMBOL_GPL(mas_prev);

/**
 * mas_prev_range() - Advance to the previous range
 * @mas: The maple state
 * @min: The minimum value to check.
 *
 * Sets @mas->index and @mas->last to the range.
 * Must hold rcu_read_lock or the write lock.
 * Will reset mas to ma_start if the node is ma_none.  Will stop on not
 * searchable nodes.
 *
 * Return: the previous value or %NULL.
 */
void *mas_prev_range(struct ma_state *mas, unsigned long min)
{
        void *entry = NULL;

        if (mas_prev_setup(mas, min, &entry))
                return entry;

        return mas_prev_slot(mas, min, true);
}
EXPORT_SYMBOL_GPL(mas_prev_range);

/**
 * mt_prev() - get the previous value in the maple tree
 * @mt: The maple tree
 * @index: The start index
 * @min: The minimum index to check
 *
 * Takes RCU read lock internally to protect the search, which does not
 * protect the returned pointer after dropping RCU read lock.
 * See also: Documentation/core-api/maple_tree.rst
 *
 * Return: The entry before @index 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->status = ma_pause;
        mas->node = NULL;
}
EXPORT_SYMBOL_GPL(mas_pause);

/**
 * mas_find_setup() - Internal function to set up mas_find*().
 * @mas: The maple state
 * @max: The maximum index
 * @entry: Pointer to the entry
 *
 * Returns: True if entry is the answer, false otherwise.
 */
static __always_inline bool mas_find_setup(struct ma_state *mas, unsigned long max, void **entry)
{
        switch (mas->status) {
        case ma_active:
                if (mas->last < max)
                        return false;
                return true;
        case ma_start:
                break;
        case ma_pause:
                if (unlikely(mas->last >= max))
                        return true;

                mas->index = ++mas->last;
                mas->status = ma_start;
                break;
        case ma_none:
                if (unlikely(mas->last >= max))
                        return true;

                mas->index = mas->last;
                mas->status = ma_start;
                break;
        case ma_underflow:
                /* mas is pointing at entry before unable to go lower */
                if (unlikely(mas->index >= max)) {
                        mas->status = ma_overflow;
                        return true;
                }

                mas_may_activate(mas);
                *entry = mas_walk(mas);
                if (*entry)
                        return true;
                break;
        case ma_overflow:
                if (unlikely(mas->last >= max))
                        return true;

                mas_may_activate(mas);
                *entry = mas_walk(mas);
                if (*entry)
                        return true;
                break;
        case ma_root:
                break;
        case ma_error:
                return true;
        }

        if (mas_is_start(mas)) {
                /* First run or continue */
                if (mas->index > max)
                        return true;

                *entry = mas_walk(mas);
                if (*entry)
                        return true;

        }

        if (unlikely(mas_is_ptr(mas)))
                goto ptr_out_of_range;

        if (unlikely(mas_is_none(mas)))
                return true;

        if (mas->index == max)
                return true;

        return false;

ptr_out_of_range:
        mas->status = ma_none;
        mas->index = 1;
        mas->last = ULONG_MAX;
        return true;
}

/**
 * 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->status to ma_overflow.
 *
 * Return: The entry or %NULL.
 */
void *mas_find(struct ma_state *mas, unsigned long max)
{
        void *entry = NULL;

        if (mas_find_setup(mas, max, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_next_slot */
        entry = mas_next_slot(mas, max, false);
        /* Ignore overflow */
        mas->status = ma_active;
        return entry;
}
EXPORT_SYMBOL_GPL(mas_find);

/**
 * mas_find_range() - On the first call, find the entry at or after
 * mas->index up to %max.  Otherwise, advance to the next slot 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->status to ma_overflow.
 *
 * Return: The entry or %NULL.
 */
void *mas_find_range(struct ma_state *mas, unsigned long max)
{
        void *entry = NULL;

        if (mas_find_setup(mas, max, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_next_slot */
        return mas_next_slot(mas, max, true);
}
EXPORT_SYMBOL_GPL(mas_find_range);

/**
 * mas_find_rev_setup() - Internal function to set up mas_find_*_rev()
 * @mas: The maple state
 * @min: The minimum index
 * @entry: Pointer to the entry
 *
 * Returns: True if entry is the answer, false otherwise.
 */
static bool mas_find_rev_setup(struct ma_state *mas, unsigned long min,
                void **entry)
{

        switch (mas->status) {
        case ma_active:
                goto active;
        case ma_start:
                break;
        case ma_pause:
                if (unlikely(mas->index <= min)) {
                        mas->status = ma_underflow;
                        return true;
                }
                mas->last = --mas->index;
                mas->status = ma_start;
                break;
        case ma_none:
                if (mas->index <= min)
                        goto none;

                mas->last = mas->index;
                mas->status = ma_start;
                break;
        case ma_overflow: /* user expects the mas to be one after where it is */
                if (unlikely(mas->index <= min)) {
                        mas->status = ma_underflow;
                        return true;
                }

                mas->status = ma_active;
                break;
        case ma_underflow: /* user expects the mas to be one before where it is */
                if (unlikely(mas->index <= min))
                        return true;

                mas->status = ma_active;
                break;
        case ma_root:
                break;
        case ma_error:
                return true;
        }

        if (mas_is_start(mas)) {
                /* First run or continue */
                if (mas->index < min)
                        return true;

                *entry = mas_walk(mas);
                if (*entry)
                        return true;
        }

        if (unlikely(mas_is_ptr(mas)))
                goto none;

        if (unlikely(mas_is_none(mas))) {
                /*
                 * Walked to the location, and there was nothing so the previous
                 * location is 0.
                 */
                mas->last = mas->index = 0;
                mas->status = ma_root;
                *entry = mas_root(mas);
                return true;
        }

active:
        if (mas->index < min)
                return true;

        return false;

none:
        mas->status = ma_none;
        return true;
}

/**
 * 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->status to ma_underflow.
 *
 * Return: The entry or %NULL.
 */
void *mas_find_rev(struct ma_state *mas, unsigned long min)
{
        void *entry = NULL;

        if (mas_find_rev_setup(mas, min, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_prev_slot */
        return mas_prev_slot(mas, min, false);

}
EXPORT_SYMBOL_GPL(mas_find_rev);

/**
 * mas_find_range_rev: On the first call, find the first non-null entry at or
 * below mas->index down to %min.  Otherwise advance to the previous slot after
 * 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->status to ma_underflow.
 *
 * Return: The entry or %NULL.
 */
void *mas_find_range_rev(struct ma_state *mas, unsigned long min)
{
        void *entry = NULL;

        if (mas_find_rev_setup(mas, min, &entry))
                return entry;

        /* Retries on dead nodes handled by mas_prev_slot */
        return mas_prev_slot(mas, min, true);
}
EXPORT_SYMBOL_GPL(mas_find_range_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;
        unsigned long index = mas->index;
        MA_WR_STATE(wr_mas, mas, NULL);

        if (!mas_is_active(mas) || !mas_is_start(mas))
                mas->status = ma_start;

write_retry:
        entry = mas_state_walk(mas);
        if (!entry)
                return NULL;

        /* Must reset to ensure spanning writes of last slot are detected */
        mas_reset(mas);
        mas_wr_preallocate(&wr_mas, NULL);
        if (mas_nomem(mas, GFP_KERNEL)) {
                /* in case the range of entry changed when unlocked */
                mas->index = mas->last = index;
                goto write_retry;
        }

        if (mas_is_err(mas))
                goto out;

        mas_wr_store_entry(&wr_mas);
out:
        mas_destroy(mas);
        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->ma_lock)
{
        if (likely(mas->node != MA_ERROR(-ENOMEM)))
                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->sheaf && !mas->alloc)
                return false;

        mas->status = ma_start;
        return true;
}

void __init maple_tree_init(void)
{
        struct kmem_cache_args args = {
                .align  = sizeof(struct maple_node),
                .sheaf_capacity = 32,
        };

        maple_node_cache = kmem_cache_create("maple_node",
                        sizeof(struct maple_node), &args,
                        SLAB_PANIC);
}

/**
 * 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(TP_FCT, &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);
        int ret = 0;

        trace_ma_write(TP_FCT, &mas, 0, entry);
        if (WARN_ON_ONCE(xa_is_advanced(entry)))
                return -EINVAL;

        if (index > last)
                return -EINVAL;

        mtree_lock(mt);
        ret = mas_store_gfp(&mas, entry, gfp);
        mtree_unlock(mt);

        return ret;
}
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 from [first, last] at a given range
 *                        if there is no value.
 * @mt: The maple tree
 * @first: The start of the range
 * @last: The end of the range (inclusive)
 * @entry: The entry to store
 * @gfp: The GFP_FLAGS to use for allocations.
 *
 * Note that @last is inclusive. That is, @last = @first + length - 1;
 *
 * 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);
        int ret = 0;

        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))
                ret = xa_err(ms.node);

        mas_destroy(&ms);
        return ret;
}
EXPORT_SYMBOL(mtree_insert_range);

/**
 * mtree_insert() - Insert an entry at a given index if there is no value.
 * @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, -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, 0, 0);
        if (!mt_is_alloc(mt))
                return -EINVAL;

        if (WARN_ON_ONCE(mt_is_reserved(entry)))
                return -EINVAL;

        mtree_lock(mt);
retry:
        ret = mas_empty_area(&mas, min, max, size);
        if (ret)
                goto unlock;

        mas_insert(&mas, entry);
        /*
         * mas_nomem() may release the lock, causing the allocated area
         * to be unavailable, so try to allocate a free area again.
         */
        if (mas_nomem(&mas, gfp))
                goto retry;

        if (mas_is_err(&mas))
                ret = xa_err(mas.node);
        else
                *startp = mas.index;

unlock:
        mtree_unlock(mt);
        mas_destroy(&mas);
        return ret;
}
EXPORT_SYMBOL(mtree_alloc_range);

/**
 * mtree_alloc_cyclic() - Find somewhere to store this entry in the tree.
 * @mt: The maple tree.
 * @startp: Pointer to ID.
 * @range_lo: Lower bound of range to search.
 * @range_hi: Upper bound of range to search.
 * @entry: The entry to store.
 * @next: Pointer to next ID to allocate.
 * @gfp: The GFP_FLAGS to use for allocations.
 *
 * Finds an empty entry in @mt after @next, stores the new index into
 * the @id pointer, stores the entry at that index, then updates @next.
 *
 * @mt must be initialized with the MT_FLAGS_ALLOC_RANGE flag.
 *
 * Context: Any context.  Takes and releases the mt.lock.  May sleep if
 * the @gfp flags permit.
 *
 * Return: 0 if the allocation succeeded without wrapping, 1 if the
 * allocation succeeded after wrapping, -ENOMEM if memory could not be
 * allocated, -EINVAL if @mt cannot be used, or -EBUSY if there are no
 * free entries.
 */
int mtree_alloc_cyclic(struct maple_tree *mt, unsigned long *startp,
                void *entry, unsigned long range_lo, unsigned long range_hi,
                unsigned long *next, gfp_t gfp)
{
        int ret;

        MA_STATE(mas, mt, 0, 0);

        if (!mt_is_alloc(mt))
                return -EINVAL;
        if (WARN_ON_ONCE(mt_is_reserved(entry)))
                return -EINVAL;
        mtree_lock(mt);
        ret = mas_alloc_cyclic(&mas, startp, entry, range_lo, range_hi,
                               next, gfp);
        mtree_unlock(mt);
        return ret;
}
EXPORT_SYMBOL(mtree_alloc_cyclic);

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, 0, 0);
        if (!mt_is_alloc(mt))
                return -EINVAL;

        if (WARN_ON_ONCE(mt_is_reserved(entry)))
                return -EINVAL;

        mtree_lock(mt);
retry:
        ret = mas_empty_area_rev(&mas, min, max, size);
        if (ret)
                goto unlock;

        mas_insert(&mas, entry);
        /*
         * mas_nomem() may release the lock, causing the allocated area
         * to be unavailable, so try to allocate a free area again.
         */
        if (mas_nomem(&mas, gfp))
                goto retry;

        if (mas_is_err(&mas))
                ret = xa_err(mas.node);
        else
                *startp = mas.index;

unlock:
        mtree_unlock(mt);
        mas_destroy(&mas);
        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(TP_FCT, &mas);

        mtree_lock(mt);
        entry = mas_erase(&mas);
        mtree_unlock(mt);

        return entry;
}
EXPORT_SYMBOL(mtree_erase);

/*
 * mas_dup_free() - Free an incomplete duplication of a tree.
 * @mas: The maple state of a incomplete tree.
 *
 * The parameter @mas->node passed in indicates that the allocation failed on
 * this node. This function frees all nodes starting from @mas->node in the
 * reverse order of mas_dup_build(). There is no need to hold the source tree
 * lock at this time.
 */
static void mas_dup_free(struct ma_state *mas)
{
        struct maple_node *node;
        enum maple_type type;
        void __rcu **slots;
        unsigned char count, i;

        /* Maybe the first node allocation failed. */
        if (mas_is_none(mas))
                return;

        while (!mte_is_root(mas->node)) {
                mas_ascend(mas);
                if (mas->offset) {
                        mas->offset--;
                        do {
                                mas_descend(mas);
                                mas->offset = mas_data_end(mas);
                        } while (!mte_is_leaf(mas->node));

                        mas_ascend(mas);
                }

                node = mte_to_node(mas->node);
                type = mte_node_type(mas->node);
                slots = ma_slots(node, type);
                count = mas_data_end(mas) + 1;
                for (i = 0; i < count; i++)
                        ((unsigned long *)slots)[i] &= ~MAPLE_NODE_MASK;
                mt_free_bulk(count, slots);
        }

        node = mte_to_node(mas->node);
        kfree(node);
}

/*
 * mas_copy_node() - Copy a maple node and replace the parent.
 * @mas: The maple state of source tree.
 * @new_mas: The maple state of new tree.
 * @parent: The parent of the new node.
 *
 * Copy @mas->node to @new_mas->node, set @parent to be the parent of
 * @new_mas->node. If memory allocation fails, @mas is set to -ENOMEM.
 */
static inline void mas_copy_node(struct ma_state *mas, struct ma_state *new_mas,
                struct maple_pnode *parent)
{
        struct maple_node *node = mte_to_node(mas->node);
        struct maple_node *new_node = mte_to_node(new_mas->node);
        unsigned long val;

        /* Copy the node completely. */
        memcpy(new_node, node, sizeof(struct maple_node));
        /* Update the parent node pointer. */
        val = (unsigned long)node->parent & MAPLE_NODE_MASK;
        new_node->parent = ma_parent_ptr(val | (unsigned long)parent);
}

/*
 * mas_dup_alloc() - Allocate child nodes for a maple node.
 * @mas: The maple state of source tree.
 * @new_mas: The maple state of new tree.
 * @gfp: The GFP_FLAGS to use for allocations.
 *
 * This function allocates child nodes for @new_mas->node during the duplication
 * process. If memory allocation fails, @mas is set to -ENOMEM.
 */
static inline void mas_dup_alloc(struct ma_state *mas, struct ma_state *new_mas,
                gfp_t gfp)
{
        struct maple_node *node = mte_to_node(mas->node);
        struct maple_node *new_node = mte_to_node(new_mas->node);
        enum maple_type type;
        unsigned char count, i;
        void __rcu **slots;
        void __rcu **new_slots;
        unsigned long val;

        /* Allocate memory for child nodes. */
        type = mte_node_type(mas->node);
        new_slots = ma_slots(new_node, type);
        count = mas->node_request = mas_data_end(mas) + 1;
        mas_alloc_nodes(mas, gfp);
        if (unlikely(mas_is_err(mas)))
                return;

        slots = ma_slots(node, type);
        for (i = 0; i < count; i++) {
                val = (unsigned long)mt_slot_locked(mas->tree, slots, i);
                val &= MAPLE_NODE_MASK;
                /*
                 * Warning, see rcu_assign_pointer() documentation.  Since this
                 * is a duplication of a tree, there are no readers walking the
                 * tree until after the rcu_assign_pointer() call in
                 * mas_dup_build().
                 */
                RCU_INIT_POINTER(new_slots[i],
                                 ma_mnode_ptr((unsigned long)mas_pop_node(mas) |
                                              val));
        }
}

/*
 * mas_dup_build() - Build a new maple tree from a source tree
 * @mas: The maple state of source tree, need to be in MAS_START state.
 * @new_mas: The maple state of new tree, need to be in MAS_START state.
 * @gfp: The GFP_FLAGS to use for allocations.
 *
 * This function builds a new tree in DFS preorder. If the memory allocation
 * fails, the error code -ENOMEM will be set in @mas, and @new_mas points to the
 * last node. mas_dup_free() will free the incomplete duplication of a tree.
 *
 * Note that the attributes of the two trees need to be exactly the same, and the
 * new tree needs to be empty, otherwise -EINVAL will be set in @mas.
 */
static inline void mas_dup_build(struct ma_state *mas, struct ma_state *new_mas,
                gfp_t gfp)
{
        struct maple_node *node;
        struct maple_pnode *parent = NULL;
        struct maple_enode *root;
        enum maple_type type;

        if (unlikely(mt_attr(mas->tree) != mt_attr(new_mas->tree)) ||
            unlikely(!mtree_empty(new_mas->tree))) {
                mas_set_err(mas, -EINVAL);
                return;
        }

        root = mas_start(mas);
        if (mas_is_ptr(mas) || mas_is_none(mas))
                goto set_new_tree;

        node = mt_alloc_one(gfp);
        if (!node) {
                new_mas->status = ma_none;
                mas_set_err(mas, -ENOMEM);
                return;
        }

        type = mte_node_type(mas->node);
        root = mt_mk_node(node, type);
        new_mas->node = root;
        new_mas->min = 0;
        new_mas->max = ULONG_MAX;
        root = mte_mk_root(root);
        while (1) {
                mas_copy_node(mas, new_mas, parent);
                if (!mte_is_leaf(mas->node)) {
                        /* Only allocate child nodes for non-leaf nodes. */
                        mas_dup_alloc(mas, new_mas, gfp);
                        if (unlikely(mas_is_err(mas)))
                                goto empty_mas;
                } else {
                        /*
                         * This is the last leaf node and duplication is
                         * completed.
                         */
                        if (mas->max == ULONG_MAX)
                                goto done;

                        /* This is not the last leaf node and needs to go up. */
                        do {
                                mas_ascend(mas);
                                mas_ascend(new_mas);
                        } while (mas->offset == mas_data_end(mas));

                        /* Move to the next subtree. */
                        mas->offset++;
                        new_mas->offset++;
                }

                mas_descend(mas);
                parent = ma_parent_ptr(mte_to_node(new_mas->node));
                mas_descend(new_mas);
                mas->offset = 0;
                new_mas->offset = 0;
        }
done:
        /* Specially handle the parent of the root node. */
        mte_to_node(root)->parent = ma_parent_ptr(mas_tree_parent(new_mas));
set_new_tree:
        /* Make them the same height */
        new_mas->tree->ma_flags = mas->tree->ma_flags;
        rcu_assign_pointer(new_mas->tree->ma_root, root);
empty_mas:
        mas_empty_nodes(mas);
}

/**
 * __mt_dup(): Duplicate an entire maple tree
 * @mt: The source maple tree
 * @new: The new maple tree
 * @gfp: The GFP_FLAGS to use for allocations
 *
 * This function duplicates a maple tree in Depth-First Search (DFS) pre-order
 * traversal. It uses memcpy() to copy nodes in the source tree and allocate
 * new child nodes in non-leaf nodes. The new node is exactly the same as the
 * source node except for all the addresses stored in it. It will be faster than
 * traversing all elements in the source tree and inserting them one by one into
 * the new tree.
 * The user needs to ensure that the attributes of the source tree and the new
 * tree are the same, and the new tree needs to be an empty tree, otherwise
 * -EINVAL will be returned.
 * Note that the user needs to manually lock the source tree and the new tree.
 *
 * Return: 0 on success, -ENOMEM if memory could not be allocated, -EINVAL If
 * the attributes of the two trees are different or the new tree is not an empty
 * tree.
 */
int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp)
{
        int ret = 0;
        MA_STATE(mas, mt, 0, 0);
        MA_STATE(new_mas, new, 0, 0);

        mas_dup_build(&mas, &new_mas, gfp);
        if (unlikely(mas_is_err(&mas))) {
                ret = xa_err(mas.node);
                if (ret == -ENOMEM)
                        mas_dup_free(&new_mas);
        }

        return ret;
}
EXPORT_SYMBOL(__mt_dup);

/**
 * mtree_dup(): Duplicate an entire maple tree
 * @mt: The source maple tree
 * @new: The new maple tree
 * @gfp: The GFP_FLAGS to use for allocations
 *
 * This function duplicates a maple tree in Depth-First Search (DFS) pre-order
 * traversal. It uses memcpy() to copy nodes in the source tree and allocate
 * new child nodes in non-leaf nodes. The new node is exactly the same as the
 * source node except for all the addresses stored in it. It will be faster than
 * traversing all elements in the source tree and inserting them one by one into
 * the new tree.
 * The user needs to ensure that the attributes of the source tree and the new
 * tree are the same, and the new tree needs to be an empty tree, otherwise
 * -EINVAL will be returned.
 *
 * Return: 0 on success, -ENOMEM if memory could not be allocated, -EINVAL If
 * the attributes of the two trees are different or the new tree is not an empty
 * tree.
 */
int mtree_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp)
{
        int ret = 0;
        MA_STATE(mas, mt, 0, 0);
        MA_STATE(new_mas, new, 0, 0);

        mas_lock(&new_mas);
        mas_lock_nested(&mas, SINGLE_DEPTH_NESTING);
        mas_dup_build(&mas, &new_mas, gfp);
        mas_unlock(&mas);
        if (unlikely(mas_is_err(&mas))) {
                ret = xa_err(mas.node);
                if (ret == -ENOMEM)
                        mas_dup_free(&new_mas);
        }

        mas_unlock(&new_mas);
        return ret;
}
EXPORT_SYMBOL(mtree_dup);

/**
 * __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 = mt_attr(mt);
}
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 of the search range
 *
 * Takes RCU read lock internally to protect the search, which does not
 * protect the returned pointer after dropping RCU read lock.
 * See also: Documentation/core-api/maple_tree.rst
 *
 * In case that an entry is found @index is updated to point to the next
 * possible entry independent whether the found entry is occupying a
 * single index or a range if indices.
 *
 * 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(TP_FCT, &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_is_active(&mas) && (mas.last < max)) {
                entry = mas_next_slot(&mas, max, false);
                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 (MT_WARN_ON(mt, (*index) && ((*index) <= copy)))
                        pr_err("index not increased! %lx <= %lx\n",
                               *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
 *
 * Same as mt_find() except that it checks @index for 0 before
 * searching. If @index == 0, the search is aborted. This covers a wrap
 * around of @index to 0 in an iterator loop.
 *
 * 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 void kmem_cache_set_callback(struct kmem_cache *cachep,
                void (*callback)(void *));
void mt_set_callback(void (*callback)(void *))
{
        kmem_cache_set_callback(maple_node_cache, callback);
}

extern void kmem_cache_set_private(struct kmem_cache *cachep, void *private);
void mt_set_private(void *private)
{
        kmem_cache_set_private(maple_node_cache, private);
}

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);
}

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);
}

/* Depth first search, post-order */
static void mas_dfs_postorder(struct ma_state *mas, unsigned long max)
{

        struct maple_enode *p, *mn = mas->node;
        unsigned long p_min, p_max;

        mas_next_node(mas, mas_mn(mas), max);
        if (!mas_is_overflow(mas))
                return;

        if (mte_is_root(mn))
                return;

        mas->node = mn;
        mas_ascend(mas);
        do {
                p = mas->node;
                p_min = mas->min;
                p_max = mas->max;
                mas_prev_node(mas, 0);
        } while (!mas_is_underflow(mas));

        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,
                enum mt_dump_format format);
static void mt_dump_range(unsigned long min, unsigned long max,
                          unsigned int depth, enum mt_dump_format format)
{
        static const char spaces[] = "                                ";

        switch(format) {
        case mt_dump_hex:
                if (min == max)
                        pr_info("%.*s%lx: ", depth * 2, spaces, min);
                else
                        pr_info("%.*s%lx-%lx: ", depth * 2, spaces, min, max);
                break;
        case mt_dump_dec:
                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, enum mt_dump_format format)
{
        mt_dump_range(min, max, depth, format);

        if (xa_is_value(entry))
                pr_cont("value %ld (0x%lx) [" PTR_FMT "]\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 (" PTR_FMT ")\n", entry);
        else
                pr_cont(PTR_FMT "\n", entry);
}

static void mt_dump_range64(const struct maple_tree *mt, void *entry,
                unsigned long min, unsigned long max, unsigned int depth,
                enum mt_dump_format format)
{
        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++) {
                switch(format) {
                case mt_dump_hex:
                        pr_cont(PTR_FMT " %lX ", node->slot[i], node->pivot[i]);
                        break;
                case mt_dump_dec:
                        pr_cont(PTR_FMT " %lu ", node->slot[i], node->pivot[i]);
                }
        }
        pr_cont(PTR_FMT "\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_node_max(entry))
                        break;
                if (last == 0 && i > 0)
                        break;
                if (leaf)
                        mt_dump_entry(mt_slot(mt, node->slot, i),
                                        first, last, depth + 1, format);
                else if (node->slot[i])
                        mt_dump_node(mt, mt_slot(mt, node->slot, i),
                                        first, last, depth + 1, format);

                if (last == max)
                        break;
                if (last > max) {
                        switch(format) {
                        case mt_dump_hex:
                                pr_err("node " PTR_FMT " last (%lx) > max (%lx) at pivot %d!\n",
                                        node, last, max, i);
                                break;
                        case mt_dump_dec:
                                pr_err("node " PTR_FMT " last (%lu) > max (%lu) at pivot %d!\n",
                                        node, last, max, i);
                        }
                }
                first = last + 1;
        }
}

static void mt_dump_arange64(const struct maple_tree *mt, void *entry,
        unsigned long min, unsigned long max, unsigned int depth,
        enum mt_dump_format format)
{
        struct maple_arange_64 *node = &mte_to_node(entry)->ma64;
        unsigned long first = min;
        int i;

        pr_cont(" contents: ");
        for (i = 0; i < MAPLE_ARANGE64_SLOTS; i++) {
                switch (format) {
                case mt_dump_hex:
                        pr_cont("%lx ", node->gap[i]);
                        break;
                case mt_dump_dec:
                        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++) {
                switch (format) {
                case mt_dump_hex:
                        pr_cont(PTR_FMT " %lX ", node->slot[i], node->pivot[i]);
                        break;
                case mt_dump_dec:
                        pr_cont(PTR_FMT " %lu ", node->slot[i], node->pivot[i]);
                }
        }
        pr_cont(PTR_FMT "\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 (node->slot[i])
                        mt_dump_node(mt, mt_slot(mt, node->slot, i),
                                        first, last, depth + 1, format);

                if (last == max)
                        break;
                if (last > max) {
                        switch(format) {
                        case mt_dump_hex:
                                pr_err("node " PTR_FMT " last (%lx) > max (%lx) at pivot %d!\n",
                                        node, last, max, i);
                                break;
                        case mt_dump_dec:
                                pr_err("node " PTR_FMT " last (%lu) > max (%lu) at pivot %d!\n",
                                        node, last, max, i);
                        }
                }
                first = last + 1;
        }
}

static void mt_dump_node(const struct maple_tree *mt, void *entry,
                unsigned long min, unsigned long max, unsigned int depth,
                enum mt_dump_format format)
{
        struct maple_node *node = mte_to_node(entry);
        unsigned int type = mte_node_type(entry);
        unsigned int i;

        mt_dump_range(min, max, depth, format);

        pr_cont("node " PTR_FMT " depth %d type %d parent " PTR_FMT, 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, format);
                }
                break;
        case maple_leaf_64:
        case maple_range_64:
                mt_dump_range64(mt, entry, min, max, depth, format);
                break;
        case maple_arange_64:
                mt_dump_arange64(mt, entry, min, max, depth, format);
                break;

        default:
                pr_cont(" UNKNOWN TYPE\n");
        }
}

void mt_dump(const struct maple_tree *mt, enum mt_dump_format format)
{
        void *entry = rcu_dereference_check(mt->ma_root, mt_locked(mt));

        pr_info("maple_tree(" PTR_FMT ") flags %X, height %u root " PTR_FMT "\n",
                 mt, mt->ma_flags, mt_height(mt), entry);
        if (xa_is_node(entry))
                mt_dump_node(mt, entry, 0, mt_node_max(entry), 0, format);
        else if (entry)
                mt_dump_entry(entry, 0, 0, 0, format);
        else
                pr_info("(empty)\n");
}
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, *node = mte_to_node(mte);
        enum maple_type mt = mte_node_type(mas->node);
        unsigned long gap = 0, max_gap = 0;
        unsigned long p_end, p_start = mas->min;
        unsigned char p_slot, offset;
        unsigned long *gaps = NULL;
        unsigned long *pivots = ma_pivots(node, mt);
        unsigned int i;

        if (ma_is_dense(mt)) {
                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(node, mt);
        for (i = 0; i < mt_slot_count(mte); i++) {
                p_end = mas_safe_pivot(mas, pivots, i, mt);

                if (!gaps) {
                        if (!mas_get_slot(mas, i))
                                gap = p_end - p_start + 1;
                } else {
                        void *entry = mas_get_slot(mas, i);

                        gap = gaps[i];
                        MT_BUG_ON(mas->tree, !entry);

                        if (gap > p_end - p_start + 1) {
                                pr_err(PTR_FMT "[%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;

                p_start = p_end + 1;
                if (p_end >= mas->max)
                        break;
        }

counted:
        if (mt == maple_arange_64) {
                MT_BUG_ON(mas->tree, !gaps);
                offset = ma_meta_gap(node);
                if (offset > i) {
                        pr_err("gap offset " PTR_FMT "[%u] is invalid\n", node, offset);
                        MT_BUG_ON(mas->tree, 1);
                }

                if (gaps[offset] != max_gap) {
                        pr_err("gap " PTR_FMT "[%u] is not the largest gap %lu\n",
                               node, offset, max_gap);
                        MT_BUG_ON(mas->tree, 1);
                }

                for (i++ ; i < mt_slot_count(mte); i++) {
                        if (gaps[i] != 0) {
                                pr_err("gap " PTR_FMT "[%u] beyond node limit != 0\n",
                                       node, i);
                                MT_BUG_ON(mas->tree, 1);
                        }
                }
        }

        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_type(mas, mte))[p_slot] != max_gap) {
                pr_err("gap " PTR_FMT "[%u] != %lu\n", p_mn, p_slot, max_gap);
                mt_dump(mas->tree, mt_dump_hex);
                MT_BUG_ON(mas->tree, 1);
        }
}

static void mas_validate_parent_slot(struct ma_state *mas)
{
        struct maple_node *parent;
        struct maple_enode *node;
        enum maple_type p_type;
        unsigned char p_slot;
        void __rcu **slots;
        int i;

        if (mte_is_root(mas->node))
                return;

        p_slot = mte_parent_slot(mas->node);
        p_type = mas_parent_type(mas, mas->node);
        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 " PTR_FMT "[%u] does not have " PTR_FMT "\n",
                                        parent, i, mas_mn(mas));
                        MT_BUG_ON(mas->tree, node != mas->node);
                } else if (node == mas->node) {
                        pr_err("Invalid child " PTR_FMT " at parent " PTR_FMT "[%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 (!child) {
                        pr_err("Non-leaf node lacks child at " PTR_FMT "[%u]\n",
                               mas_mn(mas), i);
                        MT_BUG_ON(mas->tree, 1);
                }

                if (mte_parent_slot(child) != i) {
                        pr_err("Slot error at " PTR_FMT "[%u]: child " PTR_FMT " 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 " PTR_FMT " has parent " PTR_FMT " not " PTR_FMT "\n",
                               mte_to_node(child), mte_parent(child),
                               mte_to_node(mas->node));
                        MT_BUG_ON(mas->tree, 1);
                }

                if (i < mt_pivots[type] && pivots[i] == mas->max)
                        break;
        }
}

/*
 * Validate all pivots are within mas->min and mas->max, check metadata ends
 * where the maximum ends and ensure there is no slots or pivots set outside of
 * the end of the data.
 */
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);

        for (i = 0; i < mt_slots[type]; i++) {
                unsigned long piv;

                piv = mas_safe_pivot(mas, pivots, i, type);

                if (!piv && (i != 0)) {
                        pr_err("Missing node limit pivot at " PTR_FMT "[%u]",
                               mas_mn(mas), i);
                        MAS_WARN_ON(mas, 1);
                }

                if (prev_piv > piv) {
                        pr_err(PTR_FMT "[%u] piv %lu < prev_piv %lu\n",
                                mas_mn(mas), i, piv, prev_piv);
                        MAS_WARN_ON(mas, piv < prev_piv);
                }

                if (piv < mas->min) {
                        pr_err(PTR_FMT "[%u] %lu < %lu\n", mas_mn(mas), i,
                                piv, mas->min);
                        MAS_WARN_ON(mas, piv < mas->min);
                }
                if (piv > mas->max) {
                        pr_err(PTR_FMT "[%u] %lu > %lu\n", mas_mn(mas), i,
                                piv, mas->max);
                        MAS_WARN_ON(mas, piv > mas->max);
                }
                prev_piv = piv;
                if (piv == mas->max)
                        break;
        }

        if (mas_data_end(mas) != i) {
                pr_err("node" PTR_FMT ": data_end %u != the last slot offset %u\n",
                       mas_mn(mas), mas_data_end(mas), i);
                MT_BUG_ON(mas->tree, 1);
        }

        for (i += 1; i < mt_slots[type]; i++) {
                void *entry = mas_slot(mas, slots, i);

                if (entry && (i != mt_slots[type] - 1)) {
                        pr_err(PTR_FMT "[%u] should not have entry " PTR_FMT "\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(PTR_FMT "[%u] should not have piv %lu\n",
                               mas_mn(mas), i, piv);
                        MAS_WARN_ON(mas, 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_is_ptr(&mas)))
                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 " PTR_FMT "[%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_overflow(&mas))
                                return;
                        offset = 0;
                        slots = ma_slots(mte_to_node(mas.node),
                                         mte_node_type(mas.node));
                } else {
                        offset++;
                }

        } while (!mas_is_overflow(&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)
        __must_hold(mas->tree->ma_lock)
{
        unsigned char end;

        MA_STATE(mas, mt, 0, 0);
        mas_start(&mas);
        if (!mas_is_active(&mas))
                return;

        while (!mte_is_leaf(mas.node))
                mas_descend(&mas);

        while (!mas_is_overflow(&mas)) {
                MAS_WARN_ON(&mas, mte_dead_node(mas.node));
                end = mas_data_end(&mas);
                if (MAS_WARN_ON(&mas, (end < mt_min_slot_count(mas.node)) &&
                                (!mte_is_root(mas.node)))) {
                        pr_err("Invalid size %u of " PTR_FMT "\n",
                               end, mas_mn(&mas));
                }

                mas_validate_parent_slot(&mas);
                mas_validate_limits(&mas);
                mas_validate_child_slot(&mas);
                if (mt_is_alloc(mt))
                        mas_validate_gaps(&mas);
                mas_dfs_postorder(&mas, ULONG_MAX);
        }
        mt_validate_nulls(mt);
}
EXPORT_SYMBOL_GPL(mt_validate);

void mas_dump(const struct ma_state *mas)
{
        pr_err("MAS: tree=" PTR_FMT " enode=" PTR_FMT " ",
               mas->tree, mas->node);
        switch (mas->status) {
        case ma_active:
                pr_err("(ma_active)");
                break;
        case ma_none:
                pr_err("(ma_none)");
                break;
        case ma_root:
                pr_err("(ma_root)");
                break;
        case ma_start:
                pr_err("(ma_start) ");
                break;
        case ma_pause:
                pr_err("(ma_pause) ");
                break;
        case ma_overflow:
                pr_err("(ma_overflow) ");
                break;
        case ma_underflow:
                pr_err("(ma_underflow) ");
                break;
        case ma_error:
                pr_err("(ma_error) ");
                break;
        }

        pr_err("Store Type: ");
        switch (mas->store_type) {
        case wr_invalid:
                pr_err("invalid store type\n");
                break;
        case wr_new_root:
                pr_err("new_root\n");
                break;
        case wr_store_root:
                pr_err("store_root\n");
                break;
        case wr_exact_fit:
                pr_err("exact_fit\n");
                break;
        case wr_split_store:
                pr_err("split_store\n");
                break;
        case wr_slot_store:
                pr_err("slot_store\n");
                break;
        case wr_append:
                pr_err("append\n");
                break;
        case wr_node_store:
                pr_err("node_store\n");
                break;
        case wr_spanning_store:
                pr_err("spanning_store\n");
                break;
        case wr_rebalance:
                pr_err("rebalance\n");
                break;
        }

        pr_err("[%u/%u] index=%lx last=%lx\n", mas->offset, mas->end,
               mas->index, mas->last);
        pr_err("     min=%lx max=%lx sheaf=" PTR_FMT ", request %lu depth=%u, flags=%x\n",
               mas->min, mas->max, mas->sheaf, mas->node_request, mas->depth,
               mas->mas_flags);
        if (mas->index > mas->last)
                pr_err("Check index & last\n");
}
EXPORT_SYMBOL_GPL(mas_dump);

void mas_wr_dump(const struct ma_wr_state *wr_mas)
{
        pr_err("WR_MAS: node=" PTR_FMT " r_min=%lx r_max=%lx\n",
               wr_mas->node, wr_mas->r_min, wr_mas->r_max);
        pr_err("        type=%u off_end=%u, node_end=%u, end_piv=%lx\n",
               wr_mas->type, wr_mas->offset_end, wr_mas->mas->end,
               wr_mas->end_piv);
}
EXPORT_SYMBOL_GPL(mas_wr_dump);

#endif /* CONFIG_DEBUG_MAPLE_TREE */