xarray.h

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/* SPDX-License-Identifier: GPL-2.0+ */
#ifndef _LINUX_XARRAY_H
#define _LINUX_XARRAY_H
/*
 * eXtensible Arrays
 * Copyright (c) 2017 Microsoft Corporation
 * Author: Matthew Wilcox <willy@infradead.org>
 *
 * See Documentation/core-api/xarray.rst for how to use the XArray.
 */
 
#include <linux/bitmap.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/kconfig.h>
#include <linux/limits.h>
#include <linux/lockdep.h>
#include <linux/rcupdate.h>
#include <linux/sched/mm.h>
#include <linux/spinlock.h>
#include <linux/types.h>
 
struct list_lru;
 
/*
 * The bottom two bits of the entry determine how the XArray interprets
 * the contents:
 *
 * 00: Pointer entry
 * 10: Internal entry
 * x1: Value entry or tagged pointer
 *
 * Attempting to store internal entries in the XArray is a bug.
 *
 * Most internal entries are pointers to the next node in the tree.
 * The following internal entries have a special meaning:
 *
 * 0-62: Sibling entries
 * 256: Retry entry
 * 257: Zero entry
 *
 * Errors are also represented as internal entries, but use the negative
 * space (-4094 to -2).  They're never stored in the slots array; only
 * returned by the normal API.
 */
 
#define BITS_PER_XA_VALUE   (BITS_PER_LONG - 1)
 
static inline void *xa_mk_value(unsigned long v)
{
    WARN_ON((long)v < 0);
    return (void *)((v << 1) | 1);
}
 
static inline unsigned long xa_to_value(const void *entry)
{
    return (unsigned long)entry >> 1;
}
 
static inline bool xa_is_value(const void *entry)
{
    return (unsigned long)entry & 1;
}
 
/*
 * DCL delta -- `uintptr_t` where mainline writes `unsigned long`.
 *
 * A tagged entry is a real address with its tag in the bottom two bits, so
 * the integer in the middle of the round trip has to be pointer width.
 * mainline gets that from `unsigned long` being 64 bits on arm64; this
 * target is aarch64-unknown-windows, which is LLP64 (verified:
 * sizeof(long) == 4), so mainline's spelling keeps the address's low 32
 * bits and hands back a pointer into the low 4 GB that nothing maps.
 * xa_tag_pointer()/xa_untag_pointer() here, and xa_mk_node()/xa_to_node()
 * further down, are the two round-trip pairs; xa_is_node() compares a whole
 * entry, so it widens too.  `~(uintptr_t)3` rather than mainline's `~3UL`
 * because the 32-bit mask would clear out the address half again.
 *
 * The casts that only read bits stay `unsigned long`: the tag in
 * xa_pointer_tag(), xa_is_internal() and xa_is_value() lives in the low
 * bits at either width, and the value entries (xa_mk_value()) are not
 * addresses.
 */
static inline void *xa_tag_pointer(void *p, unsigned long tag)
{
    return (void *)((uintptr_t)p | tag);
}
 
static inline void *xa_untag_pointer(void *entry)
{
    return (void *)((uintptr_t)entry & ~(uintptr_t)3);
}
 
static inline unsigned int xa_pointer_tag(void *entry)
{
    return (unsigned long)entry & 3UL;
}
 
/*
 * xa_mk_internal() - Create an internal entry.
 * @v: Value to turn into an internal entry.
 *
 * Internal entries are used for a number of purposes.  Entries 0-255 are
 * used for sibling entries (only 0-62 are used by the current code).  256
 * is used for the retry entry.  257 is used for the reserved / zero entry.
 * Negative internal entries are used to represent errnos.  Node pointers
 * are also tagged as internal entries in some situations.
 *
 * Context: Any context.
 * Return: An XArray internal entry corresponding to this value.
 */
static inline void *xa_mk_internal(unsigned long v)
{
    return (void *)((v << 2) | 2);
}
 
/*
 * xa_to_internal() - Extract the value from an internal entry.
 * @entry: XArray entry.
 *
 * Context: Any context.
 * Return: The value which was stored in the internal entry.
 */
static inline unsigned long xa_to_internal(const void *entry)
{
    return (unsigned long)entry >> 2;
}
 
/*
 * xa_is_internal() - Is the entry an internal entry?
 * @entry: XArray entry.
 *
 * Context: Any context.
 * Return: %true if the entry is an internal entry.
 */
static inline bool xa_is_internal(const void *entry)
{
    return ((unsigned long)entry & 3) == 2;
}
 
#define XA_ZERO_ENTRY       xa_mk_internal(257)
 
static inline bool xa_is_zero(const void *entry)
{
    return unlikely(entry == XA_ZERO_ENTRY);
}
 
static inline bool xa_is_err(const void *entry)
{
    return unlikely(xa_is_internal(entry) &&
            entry >= xa_mk_internal(-MAX_ERRNO));
}
 
static inline int xa_err(void *entry)
{
    /* xa_to_internal() would not do sign extension. */
    if (xa_is_err(entry))
        return (long)entry >> 2;
    return 0;
}
 
struct xa_limit {
    u32 max;
    u32 min;
};
 
#define XA_LIMIT(_min, _max) (struct xa_limit) { .min = _min, .max = _max }
 
#define xa_limit_32b    XA_LIMIT(0, UINT_MAX)
#define xa_limit_31b    XA_LIMIT(0, INT_MAX)
#define xa_limit_16b    XA_LIMIT(0, USHRT_MAX)
 
typedef unsigned __bitwise xa_mark_t;
#define XA_MARK_0       ((__force xa_mark_t)0U)
#define XA_MARK_1       ((__force xa_mark_t)1U)
#define XA_MARK_2       ((__force xa_mark_t)2U)
#define XA_PRESENT      ((__force xa_mark_t)8U)
#define XA_MARK_MAX     XA_MARK_2
#define XA_FREE_MARK        XA_MARK_0
 
enum xa_lock_type {
    XA_LOCK_IRQ = 1,
    XA_LOCK_BH = 2,
};
 
/*
 * Values for xa_flags.  The radix tree stores its GFP flags in the xa_flags,
 * and we remain compatible with that.
 */
#define XA_FLAGS_LOCK_IRQ   ((__force gfp_t)XA_LOCK_IRQ)
#define XA_FLAGS_LOCK_BH    ((__force gfp_t)XA_LOCK_BH)
#define XA_FLAGS_TRACK_FREE ((__force gfp_t)4U)
#define XA_FLAGS_ZERO_BUSY  ((__force gfp_t)8U)
#define XA_FLAGS_ALLOC_WRAPPED  ((__force gfp_t)16U)
#define XA_FLAGS_ACCOUNT    ((__force gfp_t)32U)
#define XA_FLAGS_MARK(mark) ((__force gfp_t)((1U << __GFP_BITS_SHIFT) << \
                        (__force unsigned)(mark)))
 
/* ALLOC is for a normal 0-based alloc.  ALLOC1 is for an 1-based alloc */
#define XA_FLAGS_ALLOC  (XA_FLAGS_TRACK_FREE | XA_FLAGS_MARK(XA_FREE_MARK))
#define XA_FLAGS_ALLOC1 (XA_FLAGS_TRACK_FREE | XA_FLAGS_ZERO_BUSY)
 
/*
 * If all of the entries in the array are NULL, @xa_head is a NULL pointer.
 * If the only non-NULL entry in the array is at index 0, @xa_head is that
 * entry.  If any other entry in the array is non-NULL, @xa_head points
 * to an @xa_node.
 */
struct xarray {
    spinlock_t  xa_lock;
/* private: The rest of the data structure is not to be used directly. */
    gfp_t       xa_flags;
    void __rcu *    xa_head;
};
 
#define XARRAY_INIT(name, flags) {              \
    .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock),      \
    .xa_flags = flags,                  \
    .xa_head = NULL,                    \
}
 
#define DEFINE_XARRAY_FLAGS(name, flags)                \
    struct xarray name = XARRAY_INIT(name, flags)
 
#define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)
 
#define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
 
#define DEFINE_XARRAY_ALLOC1(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC1)
 
void *xa_load(struct xarray *, unsigned long index);
void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *xa_erase(struct xarray *, unsigned long index);
void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
            void *entry, gfp_t);
bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
void *xa_find(struct xarray *xa, unsigned long *index,
        unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
void *xa_find_after(struct xarray *xa, unsigned long *index,
        unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
        unsigned long max, unsigned int n, xa_mark_t);
void xa_destroy(struct xarray *);
 
static inline void xa_init_flags(struct xarray *xa, gfp_t flags)
{
    spin_lock_init(&xa->xa_lock);
    xa->xa_flags = flags;
    xa->xa_head = NULL;
}
 
static inline void xa_init(struct xarray *xa)
{
    xa_init_flags(xa, 0);
}
 
static inline bool xa_empty(const struct xarray *xa)
{
    return xa->xa_head == NULL;
}
 
static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
{
    return xa->xa_flags & XA_FLAGS_MARK(mark);
}
 
#define xa_for_each_range(xa, index, entry, start, last)        \
    for (index = start,                     \
         entry = xa_find(xa, &index, last, XA_PRESENT);     \
         entry;                         \
         entry = xa_find_after(xa, &index, last, XA_PRESENT))
 
#define xa_for_each_start(xa, index, entry, start) \
    xa_for_each_range(xa, index, entry, start, ULONG_MAX)
 
#define xa_for_each(xa, index, entry) \
    xa_for_each_start(xa, index, entry, 0)
 
#define xa_for_each_marked(xa, index, entry, filter) \
    for (index = 0, entry = xa_find(xa, &index, ULONG_MAX, filter); \
         entry; entry = xa_find_after(xa, &index, ULONG_MAX, filter))
 
#define xa_trylock(xa)      spin_trylock(&(xa)->xa_lock)
#define xa_lock(xa)     spin_lock(&(xa)->xa_lock)
#define xa_unlock(xa)       spin_unlock(&(xa)->xa_lock)
#define xa_lock_bh(xa)      spin_lock_bh(&(xa)->xa_lock)
#define xa_unlock_bh(xa)    spin_unlock_bh(&(xa)->xa_lock)
#define xa_lock_irq(xa)     spin_lock_irq(&(xa)->xa_lock)
#define xa_unlock_irq(xa)   spin_unlock_irq(&(xa)->xa_lock)
#define xa_lock_irqsave(xa, flags) \
                spin_lock_irqsave(&(xa)->xa_lock, flags)
#define xa_unlock_irqrestore(xa, flags) \
                spin_unlock_irqrestore(&(xa)->xa_lock, flags)
#define xa_lock_nested(xa, subclass) \
                spin_lock_nested(&(xa)->xa_lock, subclass)
#define xa_lock_bh_nested(xa, subclass) \
                spin_lock_bh_nested(&(xa)->xa_lock, subclass)
#define xa_lock_irq_nested(xa, subclass) \
                spin_lock_irq_nested(&(xa)->xa_lock, subclass)
#define xa_lock_irqsave_nested(xa, flags, subclass) \
        spin_lock_irqsave_nested(&(xa)->xa_lock, flags, subclass)
 
/*
 * Versions of the normal API which require the caller to hold the
 * xa_lock.  If the GFP flags allow it, they will drop the lock to
 * allocate memory, then reacquire it afterwards.  These functions
 * may also re-enable interrupts if the XArray flags indicate the
 * locking should be interrupt safe.
 */
void *__xa_erase(struct xarray *, unsigned long index);
void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
        void *entry, gfp_t);
int __must_check __xa_insert(struct xarray *, unsigned long index,
        void *entry, gfp_t);
int __must_check __xa_alloc(struct xarray *, u32 *id, void *entry,
        struct xa_limit, gfp_t);
int __must_check __xa_alloc_cyclic(struct xarray *, u32 *id, void *entry,
        struct xa_limit, u32 *next, gfp_t);
void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
 
static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
        void *entry, gfp_t gfp)
{
    void *curr;
 
    might_alloc(gfp);
    xa_lock_bh(xa);
    curr = __xa_store(xa, index, entry, gfp);
    xa_unlock_bh(xa);
 
    return curr;
}
 
static inline void *xa_store_irq(struct xarray *xa, unsigned long index,
        void *entry, gfp_t gfp)
{
    void *curr;
 
    might_alloc(gfp);
    xa_lock_irq(xa);
    curr = __xa_store(xa, index, entry, gfp);
    xa_unlock_irq(xa);
 
    return curr;
}
 
static inline void *xa_erase_bh(struct xarray *xa, unsigned long index)
{
    void *entry;
 
    xa_lock_bh(xa);
    entry = __xa_erase(xa, index);
    xa_unlock_bh(xa);
 
    return entry;
}
 
static inline void *xa_erase_irq(struct xarray *xa, unsigned long index)
{
    void *entry;
 
    xa_lock_irq(xa);
    entry = __xa_erase(xa, index);
    xa_unlock_irq(xa);
 
    return entry;
}
 
static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index,
            void *old, void *entry, gfp_t gfp)
{
    void *curr;
 
    might_alloc(gfp);
    xa_lock(xa);
    curr = __xa_cmpxchg(xa, index, old, entry, gfp);
    xa_unlock(xa);
 
    return curr;
}
 
static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,
            void *old, void *entry, gfp_t gfp)
{
    void *curr;
 
    might_alloc(gfp);
    xa_lock_bh(xa);
    curr = __xa_cmpxchg(xa, index, old, entry, gfp);
    xa_unlock_bh(xa);
 
    return curr;
}
 
static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
            void *old, void *entry, gfp_t gfp)
{
    void *curr;
 
    might_alloc(gfp);
    xa_lock_irq(xa);
    curr = __xa_cmpxchg(xa, index, old, entry, gfp);
    xa_unlock_irq(xa);
 
    return curr;
}
 
static inline int __must_check xa_insert(struct xarray *xa,
        unsigned long index, void *entry, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock(xa);
    err = __xa_insert(xa, index, entry, gfp);
    xa_unlock(xa);
 
    return err;
}
 
static inline int __must_check xa_insert_bh(struct xarray *xa,
        unsigned long index, void *entry, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_bh(xa);
    err = __xa_insert(xa, index, entry, gfp);
    xa_unlock_bh(xa);
 
    return err;
}
 
static inline int __must_check xa_insert_irq(struct xarray *xa,
        unsigned long index, void *entry, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_irq(xa);
    err = __xa_insert(xa, index, entry, gfp);
    xa_unlock_irq(xa);
 
    return err;
}
 
static inline __must_check int xa_alloc(struct xarray *xa, u32 *id,
        void *entry, struct xa_limit limit, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock(xa);
    err = __xa_alloc(xa, id, entry, limit, gfp);
    xa_unlock(xa);
 
    return err;
}
 
static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id,
        void *entry, struct xa_limit limit, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_bh(xa);
    err = __xa_alloc(xa, id, entry, limit, gfp);
    xa_unlock_bh(xa);
 
    return err;
}
 
static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
        void *entry, struct xa_limit limit, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_irq(xa);
    err = __xa_alloc(xa, id, entry, limit, gfp);
    xa_unlock_irq(xa);
 
    return err;
}
 
static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
        struct xa_limit limit, u32 *next, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock(xa);
    err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
    xa_unlock(xa);
 
    return err < 0 ? err : 0;
}
 
static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
        struct xa_limit limit, u32 *next, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_bh(xa);
    err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
    xa_unlock_bh(xa);
 
    return err < 0 ? err : 0;
}
 
static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
        struct xa_limit limit, u32 *next, gfp_t gfp)
{
    int err;
 
    might_alloc(gfp);
    xa_lock_irq(xa);
    err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
    xa_unlock_irq(xa);
 
    return err < 0 ? err : 0;
}
 
static inline __must_check
int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp)
{
    return xa_err(xa_cmpxchg(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
 
static inline __must_check
int xa_reserve_bh(struct xarray *xa, unsigned long index, gfp_t gfp)
{
    return xa_err(xa_cmpxchg_bh(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
 
static inline __must_check
int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp)
{
    return xa_err(xa_cmpxchg_irq(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
 
static inline void xa_release(struct xarray *xa, unsigned long index)
{
    xa_cmpxchg(xa, index, XA_ZERO_ENTRY, NULL, 0);
}
 
/* Everything below here is the Advanced API.  Proceed with caution. */
 
/*
 * The xarray is constructed out of a set of 'chunks' of pointers.  Choosing
 * the best chunk size requires some tradeoffs.  A power of two recommends
 * itself so that we can walk the tree based purely on shifts and masks.
 * Generally, the larger the better; as the number of slots per level of the
 * tree increases, the less tall the tree needs to be.  But that needs to be
 * balanced against the memory consumption of each node.  On a 64-bit system,
 * xa_node is currently 576 bytes, and we get 7 of them per 4kB page.  If we
 * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
 */
#ifndef XA_CHUNK_SHIFT
#define XA_CHUNK_SHIFT      (IS_ENABLED(CONFIG_BASE_SMALL) ? 4 : 6)
#endif
#define XA_CHUNK_SIZE       (1UL << XA_CHUNK_SHIFT)
#define XA_CHUNK_MASK       (XA_CHUNK_SIZE - 1)
#define XA_MAX_MARKS        3
#define XA_MARK_LONGS       BITS_TO_LONGS(XA_CHUNK_SIZE)
 
/*
 * @count is the count of every non-NULL element in the ->slots array
 * whether that is a value entry, a retry entry, a user pointer,
 * a sibling entry or a pointer to the next level of the tree.
 * @nr_values is the count of every element in ->slots which is
 * either a value entry or a sibling of a value entry.
 */
struct xa_node {
    unsigned char   shift;      /* Bits remaining in each slot */
    unsigned char   offset;     /* Slot offset in parent */
    unsigned char   count;      /* Total entry count */
    unsigned char   nr_values;  /* Value entry count */
    struct xa_node __rcu *parent;   /* NULL at top of tree */
    struct xarray   *array;     /* The array we belong to */
    union {
        struct list_head private_list;  /* For tree user */
        struct rcu_head rcu_head;   /* Used when freeing node */
    };
    void __rcu  *slots[XA_CHUNK_SIZE];
    union {
        unsigned long   tags[XA_MAX_MARKS][XA_MARK_LONGS];
        unsigned long   marks[XA_MAX_MARKS][XA_MARK_LONGS];
    };
};
 
void xa_dump(const struct xarray *);
void xa_dump_node(const struct xa_node *);
 
#ifdef XA_DEBUG
#define XA_BUG_ON(xa, x) do {                   \
        if (x) {                    \
            xa_dump(xa);                \
            BUG();                  \
        }                       \
    } while (0)
#define XA_NODE_BUG_ON(node, x) do {                \
        if (x) {                    \
            if (node) xa_dump_node(node);       \
            BUG();                  \
        }                       \
    } while (0)
#else
#define XA_BUG_ON(xa, x)    do { } while (0)
#define XA_NODE_BUG_ON(node, x) do { } while (0)
#endif
 
/* Private */
static inline void *xa_head(const struct xarray *xa)
{
    return rcu_dereference_check(xa->xa_head,
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline void *xa_head_locked(const struct xarray *xa)
{
    return rcu_dereference_protected(xa->xa_head,
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline void *xa_entry(const struct xarray *xa,
                const struct xa_node *node, unsigned int offset)
{
    XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
    return rcu_dereference_check(node->slots[offset],
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline void *xa_entry_locked(const struct xarray *xa,
                const struct xa_node *node, unsigned int offset)
{
    XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
    return rcu_dereference_protected(node->slots[offset],
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline struct xa_node *xa_parent(const struct xarray *xa,
                    const struct xa_node *node)
{
    return rcu_dereference_check(node->parent,
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline struct xa_node *xa_parent_locked(const struct xarray *xa,
                    const struct xa_node *node)
{
    return rcu_dereference_protected(node->parent,
                        lockdep_is_held(&xa->xa_lock));
}
 
/* Private */
static inline void *xa_mk_node(const struct xa_node *node)
{
    return (void *)((uintptr_t)node | 2);
}
 
/* Private */
static inline struct xa_node *xa_to_node(const void *entry)
{
    return (struct xa_node *)((uintptr_t)entry - 2);
}
 
/* Private */
static inline bool xa_is_node(const void *entry)
{
    return xa_is_internal(entry) && (uintptr_t)entry > 4096;
}
 
/* Private */
static inline void *xa_mk_sibling(unsigned int offset)
{
    return xa_mk_internal(offset);
}
 
/* Private */
static inline unsigned long xa_to_sibling(const void *entry)
{
    return xa_to_internal(entry);
}
 
static inline bool xa_is_sibling(const void *entry)
{
    return IS_ENABLED(CONFIG_XARRAY_MULTI) && xa_is_internal(entry) &&
        (entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
}
 
#define XA_RETRY_ENTRY      xa_mk_internal(256)
 
static inline bool xa_is_retry(const void *entry)
{
    return unlikely(entry == XA_RETRY_ENTRY);
}
 
static inline bool xa_is_advanced(const void *entry)
{
    return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
}
 
typedef void (*xa_update_node_t)(struct xa_node *node);
 
void xa_delete_node(struct xa_node *, xa_update_node_t);
 
/*
 * The xa_state is opaque to its users.  It contains various different pieces
 * of state involved in the current operation on the XArray.  It should be
 * declared on the stack and passed between the various internal routines.
 * The various elements in it should not be accessed directly, but only
 * through the provided accessor functions.  The below documentation is for
 * the benefit of those working on the code, not for users of the XArray.
 *
 * @xa_node usually points to the xa_node containing the slot we're operating
 * on (and @xa_offset is the offset in the slots array).  If there is a
 * single entry in the array at index 0, there are no allocated xa_nodes to
 * point to, and so we store %NULL in @xa_node.  @xa_node is set to
 * the value %XAS_RESTART if the xa_state is not walked to the correct
 * position in the tree of nodes for this operation.  If an error occurs
 * during an operation, it is set to an %XAS_ERROR value.  If we run off the
 * end of the allocated nodes, it is set to %XAS_BOUNDS.
 */
struct xa_state {
    struct xarray *xa;
    unsigned long xa_index;
    unsigned char xa_shift;
    unsigned char xa_sibs;
    unsigned char xa_offset;
    unsigned char xa_pad;       /* Helps gcc generate better code */
    struct xa_node *xa_node;
    struct xa_node *xa_alloc;
    xa_update_node_t xa_update;
    struct list_lru *xa_lru;
};
 
/*
 * We encode errnos in the xas->xa_node.  If an error has happened, we need to
 * drop the lock to fix it, and once we've done so the xa_state is invalid.
 */
#define XA_ERROR(errno) ((struct xa_node *)(((unsigned long)errno << 2) | 2UL))
#define XAS_BOUNDS  ((struct xa_node *)1UL)
#define XAS_RESTART ((struct xa_node *)3UL)
 
#define __XA_STATE(array, index, shift, sibs)  {    \
    .xa = array,                    \
    .xa_index = index,              \
    .xa_shift = shift,              \
    .xa_sibs = sibs,                \
    .xa_offset = 0,                 \
    .xa_pad = 0,                    \
    .xa_node = XAS_RESTART,             \
    .xa_alloc = NULL,               \
    .xa_update = NULL,              \
    .xa_lru = NULL,                 \
}
 
#define XA_STATE(name, array, index)                \
    struct xa_state name = __XA_STATE(array, index, 0, 0)
 
#define XA_STATE_ORDER(name, array, index, order)       \
    struct xa_state name = __XA_STATE(array,        \
            (index >> order) << order,      \
            order - (order % XA_CHUNK_SHIFT),   \
            (1U << (order % XA_CHUNK_SHIFT)) - 1)
 
#define xas_marked(xas, mark)   xa_marked((xas)->xa, (mark))
#define xas_trylock(xas)    xa_trylock((xas)->xa)
#define xas_lock(xas)       xa_lock((xas)->xa)
#define xas_unlock(xas)     xa_unlock((xas)->xa)
#define xas_lock_bh(xas)    xa_lock_bh((xas)->xa)
#define xas_unlock_bh(xas)  xa_unlock_bh((xas)->xa)
#define xas_lock_irq(xas)   xa_lock_irq((xas)->xa)
#define xas_unlock_irq(xas) xa_unlock_irq((xas)->xa)
#define xas_lock_irqsave(xas, flags) \
                xa_lock_irqsave((xas)->xa, flags)
#define xas_unlock_irqrestore(xas, flags) \
                xa_unlock_irqrestore((xas)->xa, flags)
 
static inline int xas_error(const struct xa_state *xas)
{
    return xa_err(xas->xa_node);
}
 
static inline void xas_set_err(struct xa_state *xas, long err)
{
    xas->xa_node = XA_ERROR(err);
}
 
static inline bool xas_invalid(const struct xa_state *xas)
{
    return (unsigned long)xas->xa_node & 3;
}
 
static inline bool xas_valid(const struct xa_state *xas)
{
    return !xas_invalid(xas);
}
 
static inline bool xas_is_node(const struct xa_state *xas)
{
    return xas_valid(xas) && xas->xa_node;
}
 
/* True if the pointer is something other than a node */
static inline bool xas_not_node(struct xa_node *node)
{
    return ((unsigned long)node & 3) || !node;
}
 
/* True if the node represents RESTART or an error */
static inline bool xas_frozen(struct xa_node *node)
{
    return (unsigned long)node & 2;
}
 
/* True if the node represents head-of-tree, RESTART or BOUNDS */
static inline bool xas_top(struct xa_node *node)
{
    return node <= XAS_RESTART;
}
 
static inline void xas_reset(struct xa_state *xas)
{
    xas->xa_node = XAS_RESTART;
}
 
static inline bool xas_retry(struct xa_state *xas, const void *entry)
{
    if (xa_is_zero(entry))
        return true;
    if (!xa_is_retry(entry))
        return false;
    xas_reset(xas);
    return true;
}
 
void *xas_load(struct xa_state *);
void *xas_store(struct xa_state *, void *entry);
void *xas_find(struct xa_state *, unsigned long max);
void *xas_find_conflict(struct xa_state *);
 
bool xas_get_mark(const struct xa_state *, xa_mark_t);
void xas_set_mark(const struct xa_state *, xa_mark_t);
void xas_clear_mark(const struct xa_state *, xa_mark_t);
void *xas_find_marked(struct xa_state *, unsigned long max, xa_mark_t);
void xas_init_marks(const struct xa_state *);
 
bool xas_nomem(struct xa_state *, gfp_t);
void xas_destroy(struct xa_state *);
void xas_pause(struct xa_state *);
 
void xas_create_range(struct xa_state *);
 
#ifdef CONFIG_XARRAY_MULTI
int xa_get_order(struct xarray *, unsigned long index);
int xas_get_order(struct xa_state *xas);
void xas_split(struct xa_state *, void *entry, unsigned int order);
void xas_split_alloc(struct xa_state *, void *entry, unsigned int order, gfp_t);
void xas_try_split(struct xa_state *xas, void *entry, unsigned int order);
unsigned int xas_try_split_min_order(unsigned int order);
#else
static inline int xa_get_order(struct xarray *xa, unsigned long index)
{
    return 0;
}
 
static inline int xas_get_order(struct xa_state *xas)
{
    return 0;
}
 
static inline void xas_split(struct xa_state *xas, void *entry,
        unsigned int order)
{
    xas_store(xas, entry);
}
 
static inline void xas_split_alloc(struct xa_state *xas, void *entry,
        unsigned int order, gfp_t gfp)
{
}
 
static inline void xas_try_split(struct xa_state *xas, void *entry,
        unsigned int order)
{
}
 
static inline unsigned int xas_try_split_min_order(unsigned int order)
{
    return 0;
}
 
#endif
 
static inline void *xas_reload(struct xa_state *xas)
{
    struct xa_node *node = xas->xa_node;
    void *entry;
    char offset;
 
    if (!node)
        return xa_head(xas->xa);
    if (IS_ENABLED(CONFIG_XARRAY_MULTI)) {
        offset = (xas->xa_index >> node->shift) & XA_CHUNK_MASK;
        entry = xa_entry(xas->xa, node, offset);
        if (!xa_is_sibling(entry))
            return entry;
        offset = xa_to_sibling(entry);
    } else {
        offset = xas->xa_offset;
    }
    return xa_entry(xas->xa, node, offset);
}
 
static inline void xas_set(struct xa_state *xas, unsigned long index)
{
    xas->xa_index = index;
    xas->xa_node = XAS_RESTART;
}
 
static inline void xas_advance(struct xa_state *xas, unsigned long index)
{
    unsigned char shift = xas_is_node(xas) ? xas->xa_node->shift : 0;
 
    xas->xa_index = index;
    xas->xa_offset = (index >> shift) & XA_CHUNK_MASK;
}
 
static inline void xas_set_order(struct xa_state *xas, unsigned long index,
                    unsigned int order)
{
#ifdef CONFIG_XARRAY_MULTI
    xas->xa_index = order < BITS_PER_LONG ? (index >> order) << order : 0;
    xas->xa_shift = order - (order % XA_CHUNK_SHIFT);
    xas->xa_sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
    xas->xa_node = XAS_RESTART;
#else
    BUG_ON(order > 0);
    xas_set(xas, index);
#endif
}
 
static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update)
{
    xas->xa_update = update;
}
 
static inline void xas_set_lru(struct xa_state *xas, struct list_lru *lru)
{
    xas->xa_lru = lru;
}
 
static inline void *xas_next_entry(struct xa_state *xas, unsigned long max)
{
    struct xa_node *node = xas->xa_node;
    void *entry;
 
    if (unlikely(xas_not_node(node) || node->shift ||
            xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)))
        return xas_find(xas, max);
 
    do {
        if (unlikely(xas->xa_index >= max))
            return xas_find(xas, max);
        if (unlikely(xas->xa_offset == XA_CHUNK_MASK))
            return xas_find(xas, max);
        entry = xa_entry(xas->xa, node, xas->xa_offset + 1);
        if (unlikely(xa_is_internal(entry)))
            return xas_find(xas, max);
        xas->xa_offset++;
        xas->xa_index++;
    } while (!entry);
 
    return entry;
}
 
/* Private */
static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance,
        xa_mark_t mark)
{
    unsigned long *addr = xas->xa_node->marks[(__force unsigned)mark];
    unsigned int offset = xas->xa_offset;
 
    if (advance)
        offset++;
    if (XA_CHUNK_SIZE == BITS_PER_LONG) {
        if (offset < XA_CHUNK_SIZE) {
            unsigned long data = *addr & (~0UL << offset);
            if (data)
                return __ffs(data);
        }
        return XA_CHUNK_SIZE;
    }
 
    return find_next_bit(addr, XA_CHUNK_SIZE, offset);
}
 
static inline void *xas_next_marked(struct xa_state *xas, unsigned long max,
                                xa_mark_t mark)
{
    struct xa_node *node = xas->xa_node;
    void *entry;
    unsigned int offset;
 
    if (unlikely(xas_not_node(node) || node->shift))
        return xas_find_marked(xas, max, mark);
    offset = xas_find_chunk(xas, true, mark);
    xas->xa_offset = offset;
    xas->xa_index = (xas->xa_index & ~XA_CHUNK_MASK) + offset;
    if (xas->xa_index > max)
        return NULL;
    if (offset == XA_CHUNK_SIZE)
        return xas_find_marked(xas, max, mark);
    entry = xa_entry(xas->xa, node, offset);
    if (!entry)
        return xas_find_marked(xas, max, mark);
    return entry;
}
 
/*
 * If iterating while holding a lock, drop the lock and reschedule
 * every %XA_CHECK_SCHED loops.
 */
enum {
    XA_CHECK_SCHED = 4096,
};
 
#define xas_for_each(xas, entry, max) \
    for (entry = xas_find(xas, max); entry; \
         entry = xas_next_entry(xas, max))
 
#define xas_for_each_marked(xas, entry, max, mark) \
    for (entry = xas_find_marked(xas, max, mark); entry; \
         entry = xas_next_marked(xas, max, mark))
 
#define xas_for_each_conflict(xas, entry) \
    while ((entry = xas_find_conflict(xas)))
 
void *__xas_next(struct xa_state *);
void *__xas_prev(struct xa_state *);
 
static inline void *xas_prev(struct xa_state *xas)
{
    struct xa_node *node = xas->xa_node;
 
    if (unlikely(xas_not_node(node) || node->shift ||
                xas->xa_offset == 0))
        return __xas_prev(xas);
 
    xas->xa_index--;
    xas->xa_offset--;
    return xa_entry(xas->xa, node, xas->xa_offset);
}
 
static inline void *xas_next(struct xa_state *xas)
{
    struct xa_node *node = xas->xa_node;
 
    if (unlikely(xas_not_node(node) || node->shift ||
                xas->xa_offset == XA_CHUNK_MASK))
        return __xas_next(xas);
 
    xas->xa_index++;
    xas->xa_offset++;
    return xa_entry(xas->xa, node, xas->xa_offset);
}
 
#endif /* _LINUX_XARRAY_H */