/* SPDX-License-Identifier: GPL-2.0-or-later */

  /*
   * Copyright (C) 2001 Momchil Velikov
   * Portions Copyright (C) 2001 Christoph Hellwig

   * Copyright (C) 2006 Nick Piggin

   * Copyright (C) 2012 Konstantin Khlebnikov

   */
  #ifndef _LINUX_RADIX_TREE_H
  #define _LINUX_RADIX_TREE_H

  #include <linux/bitops.h>

  #include <linux/kernel.h>

  #include <linux/list.h>

  #include <linux/percpu.h>

  #include <linux/preempt.h>

  #include <linux/rcupdate.h>

  #include <linux/spinlock.h>
  #include <linux/types.h>

  #include <linux/xarray.h>

  #include <linux/local_lock.h>

  /* Keep unconverted code working */
  #define radix_tree_root		xarray

  #define radix_tree_node		xa_node

  struct radix_tree_preload {
  	local_lock_t lock;
  	unsigned nr;
  	/* nodes->parent points to next preallocated node */
  	struct radix_tree_node *nodes;
  };
  DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads);

  /*

   * The bottom two bits of the slot determine how the remaining bits in the
   * slot are interpreted:

   *

   * 00 - data pointer

   * 10 - internal entry
   * x1 - value entry

   *
   * The internal entry may be a pointer to the next level in the tree, a
   * sibling entry, or an indicator that the entry in this slot has been moved
   * to another location in the tree and the lookup should be restarted.  While
   * NULL fits the 'data pointer' pattern, it means that there is no entry in
   * the tree for this index (no matter what level of the tree it is found at).

   * This means that storing a NULL entry in the tree is the same as deleting
   * the entry from the tree.

   */

  #define RADIX_TREE_ENTRY_MASK		3UL

  #define RADIX_TREE_INTERNAL_NODE	2UL

  static inline bool radix_tree_is_internal_node(void *ptr)

  {

  	return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
  				RADIX_TREE_INTERNAL_NODE;

  }
  
  /*** radix-tree API starts here ***/

  #define RADIX_TREE_MAP_SHIFT	XA_CHUNK_SHIFT

  #define RADIX_TREE_MAP_SIZE	(1UL << RADIX_TREE_MAP_SHIFT)
  #define RADIX_TREE_MAP_MASK	(RADIX_TREE_MAP_SIZE-1)

  #define RADIX_TREE_MAX_TAGS	XA_MAX_MARKS
  #define RADIX_TREE_TAG_LONGS	XA_MARK_LONGS

  #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
  					  RADIX_TREE_MAP_SHIFT))

  /* The IDR tag is stored in the low bits of xa_flags */

  #define ROOT_IS_IDR	((__force gfp_t)4)

  /* The top bits of xa_flags are used to store the root tags */

  #define ROOT_TAG_SHIFT	(__GFP_BITS_SHIFT)

  #define RADIX_TREE_INIT(name, mask)	XARRAY_INIT(name, mask)

  
  #define RADIX_TREE(name, mask) \

  	struct radix_tree_root name = RADIX_TREE_INIT(name, mask)

  #define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask)

  static inline bool radix_tree_empty(const struct radix_tree_root *root)

  {

  	return root->xa_head == NULL;

  }

  /**

   * struct radix_tree_iter - radix tree iterator state
   *
   * @index:	index of current slot
   * @next_index:	one beyond the last index for this chunk
   * @tags:	bit-mask for tag-iterating
   * @node:	node that contains current slot

   *
   * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
   * subinterval of slots contained within one radix tree leaf node.  It is
   * described by a pointer to its first slot and a struct radix_tree_iter
   * which holds the chunk's position in the tree and its size.  For tagged
   * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
   * radix tree tag.
   */
  struct radix_tree_iter {
  	unsigned long	index;
  	unsigned long	next_index;
  	unsigned long	tags;
  	struct radix_tree_node *node;

  };

  /**

   * Radix-tree synchronization
   *
   * The radix-tree API requires that users provide all synchronisation (with
   * specific exceptions, noted below).
   *
   * Synchronization of access to the data items being stored in the tree, and
   * management of their lifetimes must be completely managed by API users.
   *
   * For API usage, in general,

   * - any function _modifying_ the tree or tags (inserting or deleting

   *   items, setting or clearing tags) must exclude other modifications, and

   *   exclude any functions reading the tree.

   * - any function _reading_ the tree or tags (looking up items or tags,

   *   gang lookups) must exclude modifications to the tree, but may occur
   *   concurrently with other readers.
   *
   * The notable exceptions to this rule are the following functions:

   * __radix_tree_lookup

   * radix_tree_lookup

   * radix_tree_lookup_slot

   * radix_tree_tag_get
   * radix_tree_gang_lookup
   * radix_tree_gang_lookup_tag

   * radix_tree_gang_lookup_tag_slot

   * radix_tree_tagged
   *

   * The first 7 functions are able to be called locklessly, using RCU. The

   * caller must ensure calls to these functions are made within rcu_read_lock()
   * regions. Other readers (lock-free or otherwise) and modifications may be
   * running concurrently.
   *
   * It is still required that the caller manage the synchronization and lifetimes
   * of the items. So if RCU lock-free lookups are used, typically this would mean
   * that the items have their own locks, or are amenable to lock-free access; and
   * that the items are freed by RCU (or only freed after having been deleted from
   * the radix tree *and* a synchronize_rcu() grace period).
   *
   * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
   * access to data items when inserting into or looking up from the radix tree)
   *

   * Note that the value returned by radix_tree_tag_get() may not be relied upon
   * if only the RCU read lock is held.  Functions to set/clear tags and to
   * delete nodes running concurrently with it may affect its result such that
   * two consecutive reads in the same locked section may return different
   * values.  If reliability is required, modification functions must also be
   * excluded from concurrency.
   *

   * radix_tree_tagged is able to be called without locking or RCU.
   */
  
  /**

   * radix_tree_deref_slot - dereference a slot
   * @slot: slot pointer, returned by radix_tree_lookup_slot

   *
   * For use with radix_tree_lookup_slot().  Caller must hold tree at least read

   * locked across slot lookup and dereference. Not required if write lock is
   * held (ie. items cannot be concurrently inserted).
   *
   * radix_tree_deref_retry must be used to confirm validity of the pointer if
   * only the read lock is held.

   *
   * Return: entry stored in that slot.

   */

  static inline void *radix_tree_deref_slot(void __rcu **slot)

  {

  	return rcu_dereference(*slot);

  }

  
  /**

   * radix_tree_deref_slot_protected - dereference a slot with tree lock held
   * @slot: slot pointer, returned by radix_tree_lookup_slot
   *
   * Similar to radix_tree_deref_slot.  The caller does not hold the RCU read
   * lock but it must hold the tree lock to prevent parallel updates.

   *

   * Return: entry stored in that slot.

   */

  static inline void *radix_tree_deref_slot_protected(void __rcu **slot,

  							spinlock_t *treelock)
  {

  	return rcu_dereference_protected(*slot, lockdep_is_held(treelock));

  }
  
  /**

   * radix_tree_deref_retry	- check radix_tree_deref_slot
   * @arg:	pointer returned by radix_tree_deref_slot
   * Returns:	0 if retry is not required, otherwise retry is required
   *
   * radix_tree_deref_retry must be used with radix_tree_deref_slot.
   */
  static inline int radix_tree_deref_retry(void *arg)
  {

  	return unlikely(radix_tree_is_internal_node(arg));

  }

  /**

   * radix_tree_exception	- radix_tree_deref_slot returned either exception?
   * @arg:	value returned by radix_tree_deref_slot
   * Returns:	0 if well-aligned pointer, non-0 if either kind of exception.
   */
  static inline int radix_tree_exception(void *arg)
  {

  	return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);

  }

  int radix_tree_insert(struct radix_tree_root *, unsigned long index,
  			void *);

  void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,

  			  struct radix_tree_node **nodep, void __rcu ***slotp);

  void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);

  void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
  					unsigned long index);

  void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,

  			  void __rcu **slot, void *entry);

  void radix_tree_iter_replace(struct radix_tree_root *,

  		const struct radix_tree_iter *, void __rcu **slot, void *entry);
  void radix_tree_replace_slot(struct radix_tree_root *,
  			     void __rcu **slot, void *entry);

  void radix_tree_iter_delete(struct radix_tree_root *,

  			struct radix_tree_iter *iter, void __rcu **slot);

  void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);

  void *radix_tree_delete(struct radix_tree_root *, unsigned long);

  unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,

  			void **results, unsigned long first_index,
  			unsigned int max_items);

  int radix_tree_preload(gfp_t gfp_mask);

  int radix_tree_maybe_preload(gfp_t gfp_mask);

  void radix_tree_init(void);

  void *radix_tree_tag_set(struct radix_tree_root *,

  			unsigned long index, unsigned int tag);

  void *radix_tree_tag_clear(struct radix_tree_root *,

  			unsigned long index, unsigned int tag);

  int radix_tree_tag_get(const struct radix_tree_root *,

  			unsigned long index, unsigned int tag);

  void radix_tree_iter_tag_clear(struct radix_tree_root *,

  		const struct radix_tree_iter *iter, unsigned int tag);

  unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
  		void **results, unsigned long first_index,
  		unsigned int max_items, unsigned int tag);
  unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
  		void __rcu ***results, unsigned long first_index,
  		unsigned int max_items, unsigned int tag);
  int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);

  
  static inline void radix_tree_preload_end(void)
  {

  	local_unlock(&radix_tree_preloads.lock);

  }

  void __rcu **idr_get_free(struct radix_tree_root *root,

  			      struct radix_tree_iter *iter, gfp_t gfp,
  			      unsigned long max);

  enum {
  	RADIX_TREE_ITER_TAG_MASK = 0x0f,	/* tag index in lower nybble */
  	RADIX_TREE_ITER_TAGGED   = 0x10,	/* lookup tagged slots */
  	RADIX_TREE_ITER_CONTIG   = 0x20,	/* stop at first hole */
  };

  
  /**
   * radix_tree_iter_init - initialize radix tree iterator
   *
   * @iter:	pointer to iterator state
   * @start:	iteration starting index
   * Returns:	NULL
   */

  static __always_inline void __rcu **

  radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
  {
  	/*
  	 * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
  	 * in the case of a successful tagged chunk lookup.  If the lookup was
  	 * unsuccessful or non-tagged then nobody cares about ->tags.
  	 *
  	 * Set index to zero to bypass next_index overflow protection.
  	 * See the comment in radix_tree_next_chunk() for details.
  	 */
  	iter->index = 0;
  	iter->next_index = start;
  	return NULL;
  }
  
  /**
   * radix_tree_next_chunk - find next chunk of slots for iteration
   *
   * @root:	radix tree root
   * @iter:	iterator state
   * @flags:	RADIX_TREE_ITER_* flags and tag index
   * Returns:	pointer to chunk first slot, or NULL if there no more left
   *
   * This function looks up the next chunk in the radix tree starting from
   * @iter->next_index.  It returns a pointer to the chunk's first slot.
   * Also it fills @iter with data about chunk: position in the tree (index),
   * its end (next_index), and constructs a bit mask for tagged iterating (tags).
   */

  void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,

  			     struct radix_tree_iter *iter, unsigned flags);
  
  /**

   * radix_tree_iter_lookup - look up an index in the radix tree
   * @root: radix tree root
   * @iter: iterator state
   * @index: key to look up
   *
   * If @index is present in the radix tree, this function returns the slot
   * containing it and updates @iter to describe the entry.  If @index is not
   * present, it returns NULL.
   */

  static inline void __rcu **
  radix_tree_iter_lookup(const struct radix_tree_root *root,

  			struct radix_tree_iter *iter, unsigned long index)
  {
  	radix_tree_iter_init(iter, index);
  	return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
  }
  
  /**

   * radix_tree_iter_retry - retry this chunk of the iteration
   * @iter:	iterator state
   *
   * If we iterate over a tree protected only by the RCU lock, a race
   * against deletion or creation may result in seeing a slot for which
   * radix_tree_deref_retry() returns true.  If so, call this function
   * and continue the iteration.
   */
  static inline __must_check

  void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)

  {
  	iter->next_index = iter->index;

  	iter->tags = 0;

  	return NULL;
  }

  static inline unsigned long
  __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
  {

  	return iter->index + slots;

  }

  /**

   * radix_tree_iter_resume - resume iterating when the chunk may be invalid
   * @slot: pointer to current slot
   * @iter: iterator state
   * Returns: New slot pointer

   *
   * If the iterator needs to release then reacquire a lock, the chunk may
   * have been invalidated by an insertion or deletion.  Call this function

   * before releasing the lock to continue the iteration from the next index.

   */

  void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,

  					struct radix_tree_iter *iter);

  
  /**

   * radix_tree_chunk_size - get current chunk size
   *
   * @iter:	pointer to radix tree iterator
   * Returns:	current chunk size
   */

  static __always_inline long

  radix_tree_chunk_size(struct radix_tree_iter *iter)
  {

  	return iter->next_index - iter->index;

  }
  
  /**
   * radix_tree_next_slot - find next slot in chunk
   *
   * @slot:	pointer to current slot

   * @iter:	pointer to iterator state

   * @flags:	RADIX_TREE_ITER_*, should be constant
   * Returns:	pointer to next slot, or NULL if there no more left
   *
   * This function updates @iter->index in the case of a successful lookup.
   * For tagged lookup it also eats @iter->tags.

   *
   * There are several cases where 'slot' can be passed in as NULL to this

   * function.  These cases result from the use of radix_tree_iter_resume() or

   * radix_tree_iter_retry().  In these cases we don't end up dereferencing
   * 'slot' because either:
   * a) we are doing tagged iteration and iter->tags has been set to 0, or
   * b) we are doing non-tagged iteration, and iter->index and iter->next_index
   *    have been set up so that radix_tree_chunk_size() returns 1 or 0.

   */

  static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
  				struct radix_tree_iter *iter, unsigned flags)

  {
  	if (flags & RADIX_TREE_ITER_TAGGED) {
  		iter->tags >>= 1;

  		if (unlikely(!iter->tags))
  			return NULL;

  		if (likely(iter->tags & 1ul)) {

  			iter->index = __radix_tree_iter_add(iter, 1);

  			slot++;
  			goto found;

  		}

  		if (!(flags & RADIX_TREE_ITER_CONTIG)) {

  			unsigned offset = __ffs(iter->tags);

  			iter->tags >>= offset++;
  			iter->index = __radix_tree_iter_add(iter, offset);
  			slot += offset;
  			goto found;

  		}
  	} else {

  		long count = radix_tree_chunk_size(iter);

  		while (--count > 0) {

  			slot++;

  			iter->index = __radix_tree_iter_add(iter, 1);

  			if (likely(*slot))

  				goto found;

  			if (flags & RADIX_TREE_ITER_CONTIG) {
  				/* forbid switching to the next chunk */
  				iter->next_index = 0;

  				break;

  			}

  		}
  	}
  	return NULL;

  
   found:

  	return slot;

  }
  
  /**

   * radix_tree_for_each_slot - iterate over non-empty slots
   *
   * @slot:	the void** variable for pointer to slot
   * @root:	the struct radix_tree_root pointer
   * @iter:	the struct radix_tree_iter pointer
   * @start:	iteration starting index
   *
   * @slot points to radix tree slot, @iter->index contains its index.
   */
  #define radix_tree_for_each_slot(slot, root, iter, start)		\
  	for (slot = radix_tree_iter_init(iter, start) ;			\
  	     slot || (slot = radix_tree_next_chunk(root, iter, 0)) ;	\
  	     slot = radix_tree_next_slot(slot, iter, 0))
  
  /**

   * radix_tree_for_each_tagged - iterate over tagged slots
   *
   * @slot:	the void** variable for pointer to slot
   * @root:	the struct radix_tree_root pointer
   * @iter:	the struct radix_tree_iter pointer
   * @start:	iteration starting index
   * @tag:	tag index
   *
   * @slot points to radix tree slot, @iter->index contains its index.
   */
  #define radix_tree_for_each_tagged(slot, root, iter, start, tag)	\
  	for (slot = radix_tree_iter_init(iter, start) ;			\
  	     slot || (slot = radix_tree_next_chunk(root, iter,		\
  			      RADIX_TREE_ITER_TAGGED | tag)) ;		\
  	     slot = radix_tree_next_slot(slot, iter,			\

  				RADIX_TREE_ITER_TAGGED | tag))

  #endif /* _LINUX_RADIX_TREE_H */