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470 lines
16 KiB
470 lines
16 KiB
/* SPDX-License-Identifier: GPL-2.0-or-later */ |
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/* |
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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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#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/percpu.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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#include <linux/local_lock.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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struct radix_tree_preload { |
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local_lock_t lock; |
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unsigned nr; |
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/* nodes->parent points to next preallocated node */ |
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struct radix_tree_node *nodes; |
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}; |
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DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads); |
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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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local_unlock(&radix_tree_preloads.lock); |
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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_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 iterator 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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