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3a08cd52c3
All users have now been converted to the XArray. Removing the support reduces code size and ensures new users will use the XArray instead. Signed-off-by: Matthew Wilcox <willy@infradead.org>
491 lines
17 KiB
C
491 lines
17 KiB
C
/*
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* Copyright (C) 2001 Momchil Velikov
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* Portions Copyright (C) 2001 Christoph Hellwig
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* Copyright (C) 2006 Nick Piggin
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* Copyright (C) 2012 Konstantin Khlebnikov
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _LINUX_RADIX_TREE_H
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#define _LINUX_RADIX_TREE_H
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#include <linux/bitops.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/preempt.h>
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#include <linux/rcupdate.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include <linux/xarray.h>
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/* Keep unconverted code working */
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#define radix_tree_root xarray
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#define radix_tree_node xa_node
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/*
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* The bottom two bits of the slot determine how the remaining bits in the
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* slot are interpreted:
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*
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* 00 - data pointer
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* 10 - internal entry
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* x1 - value entry
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*
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* The internal entry may be a pointer to the next level in the tree, a
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* sibling entry, or an indicator that the entry in this slot has been moved
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* to another location in the tree and the lookup should be restarted. While
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* NULL fits the 'data pointer' pattern, it means that there is no entry in
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* the tree for this index (no matter what level of the tree it is found at).
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* This means that storing a NULL entry in the tree is the same as deleting
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* the entry from the tree.
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*/
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#define RADIX_TREE_ENTRY_MASK 3UL
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#define RADIX_TREE_INTERNAL_NODE 2UL
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static inline bool radix_tree_is_internal_node(void *ptr)
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{
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return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
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RADIX_TREE_INTERNAL_NODE;
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}
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/*** radix-tree API starts here ***/
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#define RADIX_TREE_MAP_SHIFT XA_CHUNK_SHIFT
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#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
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#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
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#define RADIX_TREE_MAX_TAGS XA_MAX_MARKS
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#define RADIX_TREE_TAG_LONGS XA_MARK_LONGS
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#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
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#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
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RADIX_TREE_MAP_SHIFT))
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/* The IDR tag is stored in the low bits of xa_flags */
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#define ROOT_IS_IDR ((__force gfp_t)4)
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/* The top bits of xa_flags are used to store the root tags */
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#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT)
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#define RADIX_TREE_INIT(name, mask) XARRAY_INIT(name, mask)
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#define RADIX_TREE(name, mask) \
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struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
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#define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask)
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static inline bool radix_tree_empty(const struct radix_tree_root *root)
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{
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return root->xa_head == NULL;
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}
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/**
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* struct radix_tree_iter - radix tree iterator state
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*
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* @index: index of current slot
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* @next_index: one beyond the last index for this chunk
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* @tags: bit-mask for tag-iterating
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* @node: node that contains current slot
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*
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* This radix tree iterator works in terms of "chunks" of slots. A chunk is a
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* subinterval of slots contained within one radix tree leaf node. It is
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* described by a pointer to its first slot and a struct radix_tree_iter
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* which holds the chunk's position in the tree and its size. For tagged
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* iteration radix_tree_iter also holds the slots' bit-mask for one chosen
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* radix tree tag.
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*/
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struct radix_tree_iter {
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unsigned long index;
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unsigned long next_index;
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unsigned long tags;
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struct radix_tree_node *node;
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};
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/**
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* Radix-tree synchronization
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*
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* The radix-tree API requires that users provide all synchronisation (with
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* specific exceptions, noted below).
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*
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* Synchronization of access to the data items being stored in the tree, and
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* management of their lifetimes must be completely managed by API users.
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*
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* For API usage, in general,
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* - any function _modifying_ the tree or tags (inserting or deleting
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* items, setting or clearing tags) must exclude other modifications, and
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* exclude any functions reading the tree.
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* - any function _reading_ the tree or tags (looking up items or tags,
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* gang lookups) must exclude modifications to the tree, but may occur
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* concurrently with other readers.
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*
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* The notable exceptions to this rule are the following functions:
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* __radix_tree_lookup
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* radix_tree_lookup
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* radix_tree_lookup_slot
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* radix_tree_tag_get
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* radix_tree_gang_lookup
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* radix_tree_gang_lookup_tag
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* radix_tree_gang_lookup_tag_slot
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* radix_tree_tagged
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*
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* The first 7 functions are able to be called locklessly, using RCU. The
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* caller must ensure calls to these functions are made within rcu_read_lock()
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* regions. Other readers (lock-free or otherwise) and modifications may be
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* running concurrently.
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*
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* It is still required that the caller manage the synchronization and lifetimes
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* of the items. So if RCU lock-free lookups are used, typically this would mean
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* that the items have their own locks, or are amenable to lock-free access; and
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* that the items are freed by RCU (or only freed after having been deleted from
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* the radix tree *and* a synchronize_rcu() grace period).
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*
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* (Note, rcu_assign_pointer and rcu_dereference are not needed to control
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* access to data items when inserting into or looking up from the radix tree)
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*
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* Note that the value returned by radix_tree_tag_get() may not be relied upon
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* if only the RCU read lock is held. Functions to set/clear tags and to
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* delete nodes running concurrently with it may affect its result such that
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* two consecutive reads in the same locked section may return different
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* values. If reliability is required, modification functions must also be
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* excluded from concurrency.
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*
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* radix_tree_tagged is able to be called without locking or RCU.
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*/
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/**
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* radix_tree_deref_slot - dereference a slot
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* @slot: slot pointer, returned by radix_tree_lookup_slot
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*
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* For use with radix_tree_lookup_slot(). Caller must hold tree at least read
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* locked across slot lookup and dereference. Not required if write lock is
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* held (ie. items cannot be concurrently inserted).
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*
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* radix_tree_deref_retry must be used to confirm validity of the pointer if
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* only the read lock is held.
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*
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* Return: entry stored in that slot.
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*/
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static inline void *radix_tree_deref_slot(void __rcu **slot)
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{
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return rcu_dereference(*slot);
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}
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/**
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* radix_tree_deref_slot_protected - dereference a slot with tree lock held
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* @slot: slot pointer, returned by radix_tree_lookup_slot
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*
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* Similar to radix_tree_deref_slot. The caller does not hold the RCU read
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* lock but it must hold the tree lock to prevent parallel updates.
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*
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* Return: entry stored in that slot.
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*/
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static inline void *radix_tree_deref_slot_protected(void __rcu **slot,
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spinlock_t *treelock)
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{
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return rcu_dereference_protected(*slot, lockdep_is_held(treelock));
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}
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/**
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* radix_tree_deref_retry - check radix_tree_deref_slot
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* @arg: pointer returned by radix_tree_deref_slot
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* Returns: 0 if retry is not required, otherwise retry is required
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*
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* radix_tree_deref_retry must be used with radix_tree_deref_slot.
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*/
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static inline int radix_tree_deref_retry(void *arg)
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{
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return unlikely(radix_tree_is_internal_node(arg));
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}
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/**
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* radix_tree_exception - radix_tree_deref_slot returned either exception?
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* @arg: value returned by radix_tree_deref_slot
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* Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
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*/
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static inline int radix_tree_exception(void *arg)
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{
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return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
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}
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int radix_tree_insert(struct radix_tree_root *, unsigned long index,
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void *);
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void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
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struct radix_tree_node **nodep, void __rcu ***slotp);
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void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
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void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
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unsigned long index);
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void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
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void __rcu **slot, void *entry);
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void radix_tree_iter_replace(struct radix_tree_root *,
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const struct radix_tree_iter *, void __rcu **slot, void *entry);
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void radix_tree_replace_slot(struct radix_tree_root *,
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void __rcu **slot, void *entry);
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void radix_tree_iter_delete(struct radix_tree_root *,
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struct radix_tree_iter *iter, void __rcu **slot);
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void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
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void *radix_tree_delete(struct radix_tree_root *, unsigned long);
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unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
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void **results, unsigned long first_index,
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unsigned int max_items);
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int radix_tree_preload(gfp_t gfp_mask);
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int radix_tree_maybe_preload(gfp_t gfp_mask);
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void radix_tree_init(void);
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void *radix_tree_tag_set(struct radix_tree_root *,
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unsigned long index, unsigned int tag);
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void *radix_tree_tag_clear(struct radix_tree_root *,
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unsigned long index, unsigned int tag);
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int radix_tree_tag_get(const struct radix_tree_root *,
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unsigned long index, unsigned int tag);
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void radix_tree_iter_tag_clear(struct radix_tree_root *,
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const struct radix_tree_iter *iter, unsigned int tag);
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unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
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void **results, unsigned long first_index,
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unsigned int max_items, unsigned int tag);
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unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
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void __rcu ***results, unsigned long first_index,
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unsigned int max_items, unsigned int tag);
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int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
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static inline void radix_tree_preload_end(void)
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{
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preempt_enable();
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}
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void __rcu **idr_get_free(struct radix_tree_root *root,
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struct radix_tree_iter *iter, gfp_t gfp,
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unsigned long max);
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enum {
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RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
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RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */
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RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */
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};
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/**
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* radix_tree_iter_init - initialize radix tree iterator
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*
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* @iter: pointer to iterator state
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* @start: iteration starting index
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* Returns: NULL
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*/
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static __always_inline void __rcu **
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radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
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{
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/*
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* Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
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* in the case of a successful tagged chunk lookup. If the lookup was
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* unsuccessful or non-tagged then nobody cares about ->tags.
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*
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* Set index to zero to bypass next_index overflow protection.
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* See the comment in radix_tree_next_chunk() for details.
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*/
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iter->index = 0;
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iter->next_index = start;
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return NULL;
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}
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/**
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* radix_tree_next_chunk - find next chunk of slots for iteration
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*
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* @root: radix tree root
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* @iter: iterator state
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* @flags: RADIX_TREE_ITER_* flags and tag index
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* Returns: pointer to chunk first slot, or NULL if there no more left
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*
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* This function looks up the next chunk in the radix tree starting from
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* @iter->next_index. It returns a pointer to the chunk's first slot.
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* Also it fills @iter with data about chunk: position in the tree (index),
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* its end (next_index), and constructs a bit mask for tagged iterating (tags).
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*/
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void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,
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struct radix_tree_iter *iter, unsigned flags);
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/**
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* radix_tree_iter_lookup - look up an index in the radix tree
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* @root: radix tree root
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* @iter: iterator state
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* @index: key to look up
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*
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* If @index is present in the radix tree, this function returns the slot
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* containing it and updates @iter to describe the entry. If @index is not
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* present, it returns NULL.
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*/
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static inline void __rcu **
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radix_tree_iter_lookup(const struct radix_tree_root *root,
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struct radix_tree_iter *iter, unsigned long index)
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{
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radix_tree_iter_init(iter, index);
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return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
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}
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/**
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* radix_tree_iter_find - find a present entry
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* @root: radix tree root
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* @iter: iterator state
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* @index: start location
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*
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* This function returns the slot containing the entry with the lowest index
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* which is at least @index. If @index is larger than any present entry, this
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* function returns NULL. The @iter is updated to describe the entry found.
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*/
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static inline void __rcu **
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radix_tree_iter_find(const struct radix_tree_root *root,
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struct radix_tree_iter *iter, unsigned long index)
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{
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radix_tree_iter_init(iter, index);
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return radix_tree_next_chunk(root, iter, 0);
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}
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/**
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* radix_tree_iter_retry - retry this chunk of the iteration
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* @iter: iterator state
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*
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* If we iterate over a tree protected only by the RCU lock, a race
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* against deletion or creation may result in seeing a slot for which
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* radix_tree_deref_retry() returns true. If so, call this function
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* and continue the iteration.
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*/
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static inline __must_check
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void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)
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{
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iter->next_index = iter->index;
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iter->tags = 0;
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return NULL;
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}
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static inline unsigned long
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__radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
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{
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return iter->index + slots;
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}
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/**
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* radix_tree_iter_resume - resume iterating when the chunk may be invalid
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* @slot: pointer to current slot
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* @iter: iterator state
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* Returns: New slot pointer
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*
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* If the iterator needs to release then reacquire a lock, the chunk may
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* have been invalidated by an insertion or deletion. Call this function
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* before releasing the lock to continue the iteration from the next index.
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*/
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void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,
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struct radix_tree_iter *iter);
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/**
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* radix_tree_chunk_size - get current chunk size
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*
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* @iter: pointer to radix tree iterator
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* Returns: current chunk size
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*/
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static __always_inline long
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radix_tree_chunk_size(struct radix_tree_iter *iter)
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{
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return iter->next_index - iter->index;
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}
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/**
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* radix_tree_next_slot - find next slot in chunk
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*
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* @slot: pointer to current slot
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* @iter: pointer to interator state
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* @flags: RADIX_TREE_ITER_*, should be constant
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* Returns: pointer to next slot, or NULL if there no more left
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*
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* This function updates @iter->index in the case of a successful lookup.
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* For tagged lookup it also eats @iter->tags.
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*
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* There are several cases where 'slot' can be passed in as NULL to this
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* function. These cases result from the use of radix_tree_iter_resume() or
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* radix_tree_iter_retry(). In these cases we don't end up dereferencing
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* 'slot' because either:
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* a) we are doing tagged iteration and iter->tags has been set to 0, or
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* b) we are doing non-tagged iteration, and iter->index and iter->next_index
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* have been set up so that radix_tree_chunk_size() returns 1 or 0.
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*/
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static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
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struct radix_tree_iter *iter, unsigned flags)
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{
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if (flags & RADIX_TREE_ITER_TAGGED) {
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iter->tags >>= 1;
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if (unlikely(!iter->tags))
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return NULL;
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if (likely(iter->tags & 1ul)) {
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iter->index = __radix_tree_iter_add(iter, 1);
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slot++;
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goto found;
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}
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if (!(flags & RADIX_TREE_ITER_CONTIG)) {
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unsigned offset = __ffs(iter->tags);
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iter->tags >>= offset++;
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iter->index = __radix_tree_iter_add(iter, offset);
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slot += offset;
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goto found;
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}
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} else {
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long count = radix_tree_chunk_size(iter);
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while (--count > 0) {
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slot++;
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iter->index = __radix_tree_iter_add(iter, 1);
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if (likely(*slot))
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goto found;
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if (flags & RADIX_TREE_ITER_CONTIG) {
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/* forbid switching to the next chunk */
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iter->next_index = 0;
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break;
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}
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}
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}
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return NULL;
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found:
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return slot;
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}
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/**
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* radix_tree_for_each_slot - iterate over non-empty slots
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*
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* @slot: the void** variable for pointer to slot
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* @root: the struct radix_tree_root pointer
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* @iter: the struct radix_tree_iter pointer
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* @start: iteration starting index
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*
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* @slot points to radix tree slot, @iter->index contains its index.
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*/
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#define radix_tree_for_each_slot(slot, root, iter, start) \
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for (slot = radix_tree_iter_init(iter, start) ; \
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slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
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slot = radix_tree_next_slot(slot, iter, 0))
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/**
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* radix_tree_for_each_tagged - iterate over tagged slots
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*
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* @slot: the void** variable for pointer to slot
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* @root: the struct radix_tree_root pointer
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* @iter: the struct radix_tree_iter pointer
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* @start: iteration starting index
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* @tag: tag index
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*
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* @slot points to radix tree slot, @iter->index contains its index.
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*/
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#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
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for (slot = radix_tree_iter_init(iter, start) ; \
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slot || (slot = radix_tree_next_chunk(root, iter, \
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RADIX_TREE_ITER_TAGGED | tag)) ; \
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slot = radix_tree_next_slot(slot, iter, \
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RADIX_TREE_ITER_TAGGED | tag))
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#endif /* _LINUX_RADIX_TREE_H */
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