v4.19.13 snapshot.
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
new file mode 100644
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--- /dev/null
+++ b/include/linux/radix-tree.h
@@ -0,0 +1,621 @@
+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#ifndef _LINUX_RADIX_TREE_H
+#define _LINUX_RADIX_TREE_H
+
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/preempt.h>
+#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+/*
+ * The bottom two bits of the slot determine how the remaining bits in the
+ * slot are interpreted:
+ *
+ * 00 - data pointer
+ * 01 - internal entry
+ * 10 - exceptional entry
+ * 11 - this bit combination is currently unused/reserved
+ *
+ * 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 you cannot store NULL in the tree as a value for the index.
+ */
+#define RADIX_TREE_ENTRY_MASK 3UL
+#define RADIX_TREE_INTERNAL_NODE 1UL
+
+/*
+ * Most users of the radix tree store pointers but shmem/tmpfs stores swap
+ * entries in the same tree. They are marked as exceptional entries to
+ * distinguish them from pointers to struct page.
+ * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
+ */
+#define RADIX_TREE_EXCEPTIONAL_ENTRY 2
+#define RADIX_TREE_EXCEPTIONAL_SHIFT 2
+
+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_MAX_TAGS 3
+
+#ifndef RADIX_TREE_MAP_SHIFT
+#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
+#endif
+
+#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
+#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
+
+#define RADIX_TREE_TAG_LONGS \
+ ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
+
+#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))
+
+/*
+ * @count is the count of every non-NULL element in the ->slots array
+ * whether that is an exceptional entry, a retry entry, a user pointer,
+ * a sibling entry or a pointer to the next level of the tree.
+ * @exceptional is the count of every element in ->slots which is
+ * either radix_tree_exceptional_entry() or is a sibling entry for an
+ * exceptional entry.
+ */
+struct radix_tree_node {
+ unsigned char shift; /* Bits remaining in each slot */
+ unsigned char offset; /* Slot offset in parent */
+ unsigned char count; /* Total entry count */
+ unsigned char exceptional; /* Exceptional entry count */
+ struct radix_tree_node *parent; /* Used when ascending tree */
+ struct radix_tree_root *root; /* The tree we belong to */
+ union {
+ struct list_head private_list; /* For tree user */
+ struct rcu_head rcu_head; /* Used when freeing node */
+ };
+ void __rcu *slots[RADIX_TREE_MAP_SIZE];
+ unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
+};
+
+/* The IDR tag is stored in the low bits of the GFP flags */
+#define ROOT_IS_IDR ((__force gfp_t)4)
+/* The top bits of gfp_mask are used to store the root tags */
+#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT)
+
+struct radix_tree_root {
+ spinlock_t xa_lock;
+ gfp_t gfp_mask;
+ struct radix_tree_node __rcu *rnode;
+};
+
+#define RADIX_TREE_INIT(name, mask) { \
+ .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock), \
+ .gfp_mask = (mask), \
+ .rnode = NULL, \
+}
+
+#define RADIX_TREE(name, mask) \
+ struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
+
+#define INIT_RADIX_TREE(root, mask) \
+do { \
+ spin_lock_init(&(root)->xa_lock); \
+ (root)->gfp_mask = (mask); \
+ (root)->rnode = NULL; \
+} while (0)
+
+static inline bool radix_tree_empty(const struct radix_tree_root *root)
+{
+ return root->rnode == 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
+ * @shift: shift for the node that holds our slots
+ *
+ * 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;
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+ unsigned int shift;
+#endif
+};
+
+static inline unsigned int iter_shift(const struct radix_tree_iter *iter)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+ return iter->shift;
+#else
+ return 0;
+#endif
+}
+
+/**
+ * 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_slot
+ * radix_tree_gang_lookup_tag
+ * radix_tree_gang_lookup_tag_slot
+ * radix_tree_tagged
+ *
+ * The first 8 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_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
+ * @arg: value returned by radix_tree_deref_slot
+ * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
+ */
+static inline int radix_tree_exceptional_entry(void *arg)
+{
+ /* Not unlikely because radix_tree_exception often tested first */
+ return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
+}
+
+/**
+ * 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_create(struct radix_tree_root *, unsigned long index,
+ unsigned order, struct radix_tree_node **nodep,
+ void __rcu ***slotp);
+int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
+ unsigned order, void *);
+static inline int radix_tree_insert(struct radix_tree_root *root,
+ unsigned long index, void *entry)
+{
+ return __radix_tree_insert(root, index, 0, entry);
+}
+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);
+typedef void (*radix_tree_update_node_t)(struct radix_tree_node *);
+void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
+ void __rcu **slot, void *entry,
+ radix_tree_update_node_t update_node);
+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_delete_node(struct radix_tree_root *,
+ struct radix_tree_node *,
+ radix_tree_update_node_t update_node);
+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);
+void radix_tree_clear_tags(struct radix_tree_root *, struct radix_tree_node *,
+ void __rcu **slot);
+unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
+ void **results, unsigned long first_index,
+ unsigned int max_items);
+unsigned int radix_tree_gang_lookup_slot(const struct radix_tree_root *,
+ void __rcu ***results, unsigned long *indices,
+ 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);
+int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order);
+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_set(struct radix_tree_root *,
+ const struct radix_tree_iter *iter, 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)
+{
+ preempt_enable();
+}
+
+int radix_tree_split_preload(unsigned old_order, unsigned new_order, gfp_t);
+int radix_tree_split(struct radix_tree_root *, unsigned long index,
+ unsigned new_order);
+int radix_tree_join(struct radix_tree_root *, unsigned long index,
+ unsigned new_order, void *);
+
+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_find - find a present entry
+ * @root: radix tree root
+ * @iter: iterator state
+ * @index: start location
+ *
+ * This function returns the slot containing the entry with the lowest index
+ * which is at least @index. If @index is larger than any present entry, this
+ * function returns NULL. The @iter is updated to describe the entry found.
+ */
+static inline void __rcu **
+radix_tree_iter_find(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, 0);
+}
+
+/**
+ * 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 << iter_shift(iter));
+}
+
+/**
+ * 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) >> iter_shift(iter);
+}
+
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+void __rcu **__radix_tree_next_slot(void __rcu **slot,
+ struct radix_tree_iter *iter, unsigned flags);
+#else
+/* Can't happen without sibling entries, but the compiler can't tell that */
+static inline void __rcu **__radix_tree_next_slot(void __rcu **slot,
+ struct radix_tree_iter *iter, unsigned flags)
+{
+ return slot;
+}
+#endif
+
+/**
+ * radix_tree_next_slot - find next slot in chunk
+ *
+ * @slot: pointer to current slot
+ * @iter: pointer to interator 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:
+ if (unlikely(radix_tree_is_internal_node(rcu_dereference_raw(*slot))))
+ return __radix_tree_next_slot(slot, iter, flags);
+ 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_contig - iterate over contiguous 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_contig(slot, root, iter, start) \
+ for (slot = radix_tree_iter_init(iter, start) ; \
+ slot || (slot = radix_tree_next_chunk(root, iter, \
+ RADIX_TREE_ITER_CONTIG)) ; \
+ slot = radix_tree_next_slot(slot, iter, \
+ RADIX_TREE_ITER_CONTIG))
+
+/**
+ * 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 */