SSL xarray.h Sprache: C

/* 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)

/**
* xa_mk_value() - Create an XArray entry from an integer.
* @v: Value to store in XArray.
*
* Context: Any context.
* Return: An entry suitable for storing in the XArray.
*/
static inline void *xa_mk_value(unsigned long v)
{
WARN_ON((long)v < 0);
return (void *)((v << 1) | 1);
}

/**
* xa_to_value() - Get value stored in an XArray entry.
* @entry: XArray entry.
*
* Context: Any context.
* Return: The value stored in the XArray entry.
*/
static inline unsigned long xa_to_value(const void *entry)
{
return (unsigned long)entry >> 1;
}

/**
* xa_is_value() - Determine if an entry is a value.
* @entry: XArray entry.
*
* Context: Any context.
* Return: True if the entry is a value, false if it is a pointer.
*/
static inline bool xa_is_value(const void *entry)
{
return (unsigned long)entry & 1;
}

/**
* xa_tag_pointer() - Create an XArray entry for a tagged pointer.
* @p: Plain pointer.
* @tag: Tag value (0, 1 or 3).
*
* If the user of the XArray prefers, they can tag their pointers instead
* of storing value entries.  Three tags are available (0, 1 and 3).
* These are distinct from the xa_mark_t as they are not replicated up
* through the array and cannot be searched for.
*
* Context: Any context.
* Return: An XArray entry.
*/
static inline void *xa_tag_pointer(void *p, unsigned long tag)
{
return (void *)((unsigned long)p | tag);
}

/**
* xa_untag_pointer() - Turn an XArray entry into a plain pointer.
* @entry: XArray entry.
*
* If you have stored a tagged pointer in the XArray, call this function
* to get the untagged version of the pointer.
*
* Context: Any context.
* Return: A pointer.
*/
static inline void *xa_untag_pointer(void *entry)
{
return (void *)((unsigned long)entry & ~3UL);
}

/**
* xa_pointer_tag() - Get the tag stored in an XArray entry.
* @entry: XArray entry.
*
* If you have stored a tagged pointer in the XArray, call this function
* to get the tag of that pointer.
*
* Context: Any context.
* Return: A tag.
*/
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)

/**
* xa_is_zero() - Is the entry a zero entry?
* @entry: Entry retrieved from the XArray
*
* The normal API will return NULL as the contents of a slot containing
* a zero entry.  You can only see zero entries by using the advanced API.
*
* Return: %true if the entry is a zero entry.
*/
static inline bool xa_is_zero(const void *entry)
{
return unlikely(entry == XA_ZERO_ENTRY);
}

/**
* xa_is_err() - Report whether an XArray operation returned an error
* @entry: Result from calling an XArray function
*
* If an XArray operation cannot complete an operation, it will return
* a special value indicating an error.  This function tells you
* whether an error occurred; xa_err() tells you which error occurred.
*
* Context: Any context.
* Return: %true if the entry indicates an error.
*/
static inline bool xa_is_err(const void *entry)
{
return unlikely(xa_is_internal(entry) &&
   entry >= xa_mk_internal(-MAX_ERRNO));
}

/**
* xa_err() - Turn an XArray result into an errno.
* @entry: Result from calling an XArray function.
*
* If an XArray operation cannot complete an operation, it will return
* a special pointer value which encodes an errno.  This function extracts
* the errno from the pointer value, or returns 0 if the pointer does not
* represent an errno.
*
* Context: Any context.
* Return: A negative errno or 0.
*/
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 - Represents a range of IDs.
* @min: The lowest ID to allocate (inclusive).
* @max: The maximum ID to allocate (inclusive).
*
* This structure is used either directly or via the XA_LIMIT() macro
* to communicate the range of IDs that are valid for allocation.
* Three common ranges are predefined for you:
* * xa_limit_32b - [0 - UINT_MAX]
* * xa_limit_31b - [0 - INT_MAX]
* * xa_limit_16b - [0 - USHRT_MAX]
*/
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)

/**
* struct xarray - The anchor of the XArray.
* @xa_lock: Lock that protects the contents of the XArray.
*
* To use the xarray, define it statically or embed it in your data structure.
* It is a very small data structure, so it does not usually make sense to
* allocate it separately and keep a pointer to it in your data structure.
*
* You may use the xa_lock to protect your own data structures as well.
*/
/*
* 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_XARRAY_FLAGS() - Define an XArray with custom flags.
* @name: A string that names your XArray.
* @flags: XA_FLAG values.
*
* This is intended for file scope definitions of XArrays.  It declares
* and initialises an empty XArray with the chosen name and flags.  It is
* equivalent to calling xa_init_flags() on the array, but it does the
* initialisation at compiletime instead of runtime.
*/
#define DEFINE_XARRAY_FLAGS(name, flags)    \
struct xarray name = XARRAY_INIT(name, flags)

/**
* DEFINE_XARRAY() - Define an XArray.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of XArrays.  It declares
* and initialises an empty XArray with the chosen name.  It is equivalent
* to calling xa_init() on the array, but it does the initialisation at
* compiletime instead of runtime.
*/
#define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)

/**
* DEFINE_XARRAY_ALLOC() - Define an XArray which allocates IDs starting at 0.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of allocating XArrays.
* See also DEFINE_XARRAY().
*/
#define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)

/**
* DEFINE_XARRAY_ALLOC1() - Define an XArray which allocates IDs starting at 1.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of allocating XArrays.
* See also DEFINE_XARRAY().
*/
#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 *);

/**
* xa_init_flags() - Initialise an empty XArray with flags.
* @xa: XArray.
* @flags: XA_FLAG values.
*
* If you need to initialise an XArray with special flags (eg you need
* to take the lock from interrupt context), use this function instead
* of xa_init().
*
* Context: Any context.
*/
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;
}

/**
* xa_init() - Initialise an empty XArray.
* @xa: XArray.
*
* An empty XArray is full of NULL entries.
*
* Context: Any context.
*/
static inline void xa_init(struct xarray *xa)
{
xa_init_flags(xa, 0);
}

/**
* xa_empty() - Determine if an array has any present entries.
* @xa: XArray.
*
* Context: Any context.
* Return: %true if the array contains only NULL pointers.
*/
static inline bool xa_empty(const struct xarray *xa)
{
return xa->xa_head == NULL;
}

/**
* xa_marked() - Inquire whether any entry in this array has a mark set
* @xa: Array
* @mark: Mark value
*
* Context: Any context.
* Return: %true if any entry has this mark set.
*/
static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
{
return xa->xa_flags & XA_FLAGS_MARK(mark);
}

/**
* xa_for_each_range() - Iterate over a portion of an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @start: First index to retrieve from array.
* @last: Last index to retrieve from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index.  You may modify @index during the iteration if you
* want to skip or reprocess indices.  It is safe to modify the array
* during the iteration.  At the end of the iteration, @entry will be set
* to NULL and @index will have a value less than or equal to max.
*
* xa_for_each_range() is O(n.log(n)) while xas_for_each() is O(n).  You have
* to handle your own locking with xas_for_each(), and if you have to unlock
* after each iteration, it will also end up being O(n.log(n)).
* xa_for_each_range() will spin if it hits a retry entry; if you intend to
* see retry entries, you should use the xas_for_each() iterator instead.
* The xas_for_each() iterator will expand into more inline code than
* xa_for_each_range().
*
* Context: Any context.  Takes and releases the RCU lock.
*/
#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))

/**
* xa_for_each_start() - Iterate over a portion of an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @start: First index to retrieve from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index.  You may modify @index during the iteration if you
* want to skip or reprocess indices.  It is safe to modify the array
* during the iteration.  At the end of the iteration, @entry will be set
* to NULL and @index will have a value less than or equal to max.
*
* xa_for_each_start() is O(n.log(n)) while xas_for_each() is O(n).  You have
* to handle your own locking with xas_for_each(), and if you have to unlock
* after each iteration, it will also end up being O(n.log(n)).
* xa_for_each_start() will spin if it hits a retry entry; if you intend to
* see retry entries, you should use the xas_for_each() iterator instead.
* The xas_for_each() iterator will expand into more inline code than
* xa_for_each_start().
*
* Context: Any context.  Takes and releases the RCU lock.
*/
#define xa_for_each_start(xa, index, entry, start) \
xa_for_each_range(xa, index, entry, start, ULONG_MAX)

/**
* xa_for_each() - Iterate over present entries in an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index.  You may modify @index during the iteration if you want
* to skip or reprocess indices.  It is safe to modify the array during the
* iteration.  At the end of the iteration, @entry will be set to NULL and
* @index will have a value less than or equal to max.
*
* xa_for_each() is O(n.log(n)) while xas_for_each() is O(n).  You have
* to handle your own locking with xas_for_each(), and if you have to unlock
* after each iteration, it will also end up being O(n.log(n)).  xa_for_each()
* will spin if it hits a retry entry; if you intend to see retry entries,
* you should use the xas_for_each() iterator instead.  The xas_for_each()
* iterator will expand into more inline code than xa_for_each().
*
* Context: Any context.  Takes and releases the RCU lock.
*/
#define xa_for_each(xa, index, entry) \
xa_for_each_start(xa, index, entry, 0)

/**
* xa_for_each_marked() - Iterate over marked entries in an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @filter: Selection criterion.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index.  The iteration will skip all entries in the array
* which do not match @filter.  You may modify @index during the iteration
* if you want to skip or reprocess indices.  It is safe to modify the array
* during the iteration.  At the end of the iteration, @entry will be set to
* NULL and @index will have a value less than or equal to max.
*
* xa_for_each_marked() is O(n.log(n)) while xas_for_each_marked() is O(n).
* You have to handle your own locking with xas_for_each(), and if you have
* to unlock after each iteration, it will also end up being O(n.log(n)).
* xa_for_each_marked() will spin if it hits a retry entry; if you intend to
* see retry entries, you should use the xas_for_each_marked() iterator
* instead.  The xas_for_each_marked() iterator will expand into more inline
* code than xa_for_each_marked().
*
* Context: Any context.  Takes and releases the RCU lock.
*/
#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);

/**
* xa_store_bh() - Store this entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_store() except it disables softirqs
* while holding the array lock.
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.
* Return: The old entry at this index or xa_err() if an error happened.
*/
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;
}

/**
* xa_store_irq() - Store this entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_store() except it disables interrupts
* while holding the array lock.
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.
* Return: The old entry at this index or xa_err() if an error happened.
*/
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;
}

/**
* xa_erase_bh() - Erase this entry from the XArray.
* @xa: XArray.
* @index: Index of entry.
*
* After this function returns, loading from @index will return %NULL.
* If the index is part of a multi-index entry, all indices will be erased
* and none of the entries will be part of a multi-index entry.
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.
* Return: The entry which used to be at this index.
*/
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;
}

/**
* xa_erase_irq() - Erase this entry from the XArray.
* @xa: XArray.
* @index: Index of entry.
*
* After this function returns, loading from @index will return %NULL.
* If the index is part of a multi-index entry, all indices will be erased
* and none of the entries will be part of a multi-index entry.
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.
* Return: The entry which used to be at this index.
*/
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;
}

/**
* xa_cmpxchg() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* If the entry at @index is the same as @old, replace it with @entry.
* If the return value is equal to @old, then the exchange was successful.
*
* Context: Any context.  Takes and releases the xa_lock.  May sleep
* if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
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;
}

/**
* xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_cmpxchg() except it disables softirqs
* while holding the array lock.
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.  May sleep if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
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;
}

/**
* xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_cmpxchg() except it disables interrupts
* while holding the array lock.
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.  May sleep if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
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;
}

/**
* xa_insert() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present.  Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context.  Takes and releases the xa_lock.  May sleep if
* the @gfp flags permit.
* Return: 0 if the store succeeded.  -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
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;
}

/**
* xa_insert_bh() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present.  Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.  May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded.  -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
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;
}

/**
* xa_insert_irq() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present.  Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.  May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded.  -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
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;
}

/**
* xa_alloc() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Context: Any context.  Takes and releases the xa_lock.  May sleep if
* the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_alloc_bh() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.  May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_alloc_irq() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.  May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Any context.  Takes and releases the xa_lock.  May sleep if
* the @gfp flags permit.
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_alloc_cyclic_bh() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.  May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_alloc_cyclic_irq() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index.  A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.  May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
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;
}

/**
* xa_reserve() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* Ensures there is somewhere to store an entry at @index in the array.
* If there is already something stored at @index, this function does
* nothing.  If there was nothing there, the entry is marked as reserved.
* Loading from a reserved entry returns a %NULL pointer.
*
* If you do not use the entry that you have reserved, call xa_release()
* or xa_erase() to free any unnecessary memory.
*
* Context: Any context.  Takes and releases the xa_lock.
* May sleep if the @gfp flags permit.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
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));
}

/**
* xa_reserve_bh() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* A softirq-disabling version of xa_reserve().
*
* Context: Any context.  Takes and releases the xa_lock while
* disabling softirqs.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
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));
}

/**
* xa_reserve_irq() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* An interrupt-disabling version of xa_reserve().
*
* Context: Process context.  Takes and releases the xa_lock while
* disabling interrupts.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
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));
}

/**
* xa_release() - Release a reserved entry.
* @xa: XArray.
* @index: Index of entry.
*
* After calling xa_reserve(), you can call this function to release the
* reservation.  If the entry at @index has been stored to, this function
* will do nothing.
*/
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 *)((unsigned long)node | 2);
}

/* Private */
static inline struct xa_node *xa_to_node(const void *entry)
{
return (struct xa_node *)((unsigned long)entry - 2);
}

/* Private */
static inline bool xa_is_node(const void *entry)
{
return xa_is_internal(entry) && (unsigned long)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);
}

/**
* xa_is_sibling() - Is the entry a sibling entry?
* @entry: Entry retrieved from the XArray
*
* Return: %true if the entry is a sibling 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)

/**
* xa_is_retry() - Is the entry a retry entry?
* @entry: Entry retrieved from the XArray
*
* Return: %true if the entry is a retry entry.
*/
static inline bool xa_is_retry(const void *entry)
{
return unlikely(entry == XA_RETRY_ENTRY);
}

/**
* xa_is_advanced() - Is the entry only permitted for the advanced API?
* @entry: Entry to be stored in the XArray.
*
* Return: %true if the entry cannot be stored by the normal API.
*/
static inline bool xa_is_advanced(const void *entry)
{
return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
}

/**
* typedef xa_update_node_t - A callback function from the XArray.
* @node: The node which is being processed
*
* This function is called every time the XArray updates the count of
* present and value entries in a node.  It allows advanced users to
* maintain the private_list in the node.
*
* Context: The xa_lock is held and interrupts may be disabled.
*     Implementations should not drop the xa_lock, nor re-enable
*     interrupts.
*/
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,     \
}

/**
* XA_STATE() - Declare an XArray operation state.
* @name: Name of this operation state (usually xas).
* @array: Array to operate on.
* @index: Initial index of interest.
*
* Declare and initialise an xa_state on the stack.
*/
#define XA_STATE(name, array, index)    \
struct xa_state name = __XA_STATE(array, index, 0, 0)

/**
* XA_STATE_ORDER() - Declare an XArray operation state.
* @name: Name of this operation state (usually xas).
* @array: Array to operate on.
* @index: Initial index of interest.
* @order: Order of entry.
*
* Declare and initialise an xa_state on the stack.  This variant of
* XA_STATE() allows you to specify the 'order' of the element you
* want to operate on.`
*/
#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)

/**
* xas_error() - Return an errno stored in the xa_state.
* @xas: XArray operation state.
*
* Return: 0 if no error has been noted.  A negative errno if one has.
*/
static inline int xas_error(const struct xa_state *xas)
{
return xa_err(xas->xa_node);
}

/**
* xas_set_err() - Note an error in the xa_state.
* @xas: XArray operation state.
* @err: Negative error number.
*
* Only call this function with a negative @err; zero or positive errors
* will probably not behave the way you think they should.  If you want
* to clear the error from an xa_state, use xas_reset().
*/
static inline void xas_set_err(struct xa_state *xas, long err)
{
xas->xa_node = XA_ERROR(err);
}

/**
* xas_invalid() - Is the xas in a retry or error state?
* @xas: XArray operation state.
*
* Return: %true if the xas cannot be used for operations.
*/
static inline bool xas_invalid(const struct xa_state *xas)
{
return (unsigned long)xas->xa_node & 3;
}

/**
* xas_valid() - Is the xas a valid cursor into the array?
* @xas: XArray operation state.
*
* Return: %true if the xas can be used for operations.
*/
static inline bool xas_valid(const struct xa_state *xas)
{
return !xas_invalid(xas);
}

/**
* xas_is_node() - Does the xas point to a node?
* @xas: XArray operation state.
*
* Return: %true if the xas currently references a node.
*/
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;
}

/**
* xas_reset() - Reset an XArray operation state.
* @xas: XArray operation state.
*
* Resets the error or walk state of the @xas so future walks of the
* array will start from the root.  Use this if you have dropped the
* xarray lock and want to reuse the xa_state.
*
* Context: Any context.
*/
static inline void xas_reset(struct xa_state *xas)
{
xas->xa_node = XAS_RESTART;
}

/**
* xas_retry() - Retry the operation if appropriate.
* @xas: XArray operation state.
* @entry: Entry from xarray.
*
* The advanced functions may sometimes return an internal entry, such as
* a retry entry or a zero entry.  This function sets up the @xas to restart
* the walk from the head of the array if needed.
*
* Context: Any context.
* Return: true if the operation needs to be retried.
*/
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

/**
* xas_reload() - Refetch an entry from the xarray.
* @xas: XArray operation state.
*
* Use this function to check that a previously loaded entry still has
* the same value.  This is useful for the lockless pagecache lookup where
* we walk the array with only the RCU lock to protect us, lock the page,
* then check that the page hasn't moved since we looked it up.
*
* The caller guarantees that @xas is still valid.  If it may be in an
* error or restart state, call xas_load() instead.
*
* Return: The entry at this location in the xarray.
*/
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);
}

/**
* xas_set() - Set up XArray operation state for a different index.
* @xas: XArray operation state.
* @index: New index into the XArray.
*
* Move the operation state to refer to a different index.  This will
* have the effect of starting a walk from the top; see xas_next()
* to move to an adjacent index.
*/
static inline void xas_set(struct xa_state *xas, unsigned long index)
{
xas->xa_index = index;
xas->xa_node = XAS_RESTART;
}

/**
* xas_advance() - Skip over sibling entries.
* @xas: XArray operation state.
* @index: Index of last sibling entry.
*
* Move the operation state to refer to the last sibling entry.
* This is useful for loops that normally want to see sibling
* entries but sometimes want to skip them.  Use xas_set() if you
* want to move to an index which is not part of this entry.
*/
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;
}

/**
* xas_set_order() - Set up XArray operation state for a multislot entry.
* @xas: XArray operation state.
* @index: Target of the operation.
* @order: Entry occupies 2^@order indices.
*/
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
}

/**
* xas_set_update() - Set up XArray operation state for a callback.
* @xas: XArray operation state.
* @update: Function to call when updating a node.
*
* The XArray can notify a caller after it has updated an xa_node.
* This is advanced functionality and is only needed by the page
* cache and swap cache.
*/
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;
}

/**
* xas_next_entry() - Advance iterator to next present entry.
* @xas: XArray operation state.
* @max: Highest index to return.
*
* xas_next_entry() is an inline function to optimise xarray traversal for
* speed.  It is equivalent to calling xas_find(), and will call xas_find()
* for all the hard cases.
*
* Return: The next present entry after the one currently referred to by @xas.
*/
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);
}

/**
* xas_next_marked() - Advance iterator to next marked entry.
* @xas: XArray operation state.
* @max: Highest index to return.
* @mark: Mark to search for.
*
* xas_next_marked() is an inline function to optimise xarray traversal for
* speed.  It is equivalent to calling xas_find_marked(), and will call
* xas_find_marked() for all the hard cases.
*
* Return: The next marked entry after the one currently referred to by @xas.
*/
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,
};

/**
* xas_for_each() - Iterate over a range of an XArray.
* @xas: XArray operation state.
* @entry: Entry retrieved from the array.
* @max: Maximum index to retrieve from array.
*
* The loop body will be executed for each entry present in the xarray
* between the current xas position and @max.  @entry will be set to
* the entry retrieved from the xarray.  It is safe to delete entries
* from the array in the loop body.  You should hold either the RCU lock
* or the xa_lock while iterating.  If you need to drop the lock, call
* xas_pause() first.
*/
#define xas_for_each(xas, entry, max) \
for (entry = xas_find(xas, max); entry; \
      entry = xas_next_entry(xas, max))

/**
* xas_for_each_marked() - Iterate over a range of an XArray.
* @xas: XArray operation state.
* @entry: Entry retrieved from the array.
* @max: Maximum index to retrieve from array.
* @mark: Mark to search for.
*
* The loop body will be executed for each marked entry in the xarray
* between the current xas position and @max.  @entry will be set to
* the entry retrieved from the xarray.  It is safe to delete entries
* from the array in the loop body.  You should hold either the RCU lock
* or the xa_lock while iterating.  If you need to drop the lock, call
* xas_pause() first.
*/
#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))

/**
* xas_for_each_conflict() - Iterate over a range of an XArray.
* @xas: XArray operation state.
* @entry: Entry retrieved from the array.
*
* The loop body will be executed for each entry in the XArray that
* lies within the range specified by @xas.  If the loop terminates
* normally, @entry will be %NULL.  The user may break out of the loop,
* which will leave @entry set to the conflicting entry.  The caller
* may also call xa_set_err() to exit the loop while setting an error
* to record the reason.
*/
#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 *);

/**
* xas_prev() - Move iterator to previous index.
* @xas: XArray operation state.
*
* If the @xas was in an error state, it will remain in an error state
* and this function will return %NULL.  If the @xas has never been walked,
* it will have the effect of calling xas_load().  Otherwise one will be
* subtracted from the index and the state will be walked to the correct
* location in the array for the next operation.
*
* If the iterator was referencing index 0, this function wraps
* around to %ULONG_MAX.
*
* Return: The entry at the new index.  This may be %NULL or an internal
* entry.
*/
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);
}

/**
* xas_next() - Move state to next index.
* @xas: XArray operation state.
*
* If the @xas was in an error state, it will remain in an error state
* and this function will return %NULL.  If the @xas has never been walked,
* it will have the effect of calling xas_load().  Otherwise one will be
* added to the index and the state will be walked to the correct
* location in the array for the next operation.
*
* If the iterator was referencing index %ULONG_MAX, this function wraps
* around to 0.
*
* Return: The entry at the new index.  This may be %NULL or an internal
* entry.
*/
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 */

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