hashtable: introduce a small and naive hashtable
This hashtable implementation is using hlist buckets to provide a simple hashtable to prevent it from getting reimplemented all over the kernel. Signed-off-by: Sasha Levin <levinsasha928@gmail.com> [ Merging this now, so that subsystems can start applying Sasha's patches that use this - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Sasha Levin
Linus Torvalds
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/*
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* Statically sized hash table implementation
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* (C) 2012 Sasha Levin <levinsasha928@gmail.com>
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*/
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#ifndef _LINUX_HASHTABLE_H
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#define _LINUX_HASHTABLE_H
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#include <linux/list.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/hash.h>
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#include <linux/rculist.h>
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#define DEFINE_HASHTABLE(name, bits) \
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struct hlist_head name[1 << (bits)] = \
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{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
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#define DECLARE_HASHTABLE(name, bits) \
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struct hlist_head name[1 << (bits)]
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#define HASH_SIZE(name) (ARRAY_SIZE(name))
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#define HASH_BITS(name) ilog2(HASH_SIZE(name))
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/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
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#define hash_min(val, bits) \
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(sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))
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static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
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{
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unsigned int i;
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for (i = 0; i < sz; i++)
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INIT_HLIST_HEAD(&ht[i]);
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}
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/**
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* hash_init - initialize a hash table
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* @hashtable: hashtable to be initialized
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*
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* Calculates the size of the hashtable from the given parameter, otherwise
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* same as hash_init_size.
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*
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* This has to be a macro since HASH_BITS() will not work on pointers since
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* it calculates the size during preprocessing.
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*/
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#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))
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/**
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* hash_add - add an object to a hashtable
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* @hashtable: hashtable to add to
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* @node: the &struct hlist_node of the object to be added
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* @key: the key of the object to be added
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*/
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#define hash_add(hashtable, node, key) \
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hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
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/**
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* hash_add_rcu - add an object to a rcu enabled hashtable
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* @hashtable: hashtable to add to
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* @node: the &struct hlist_node of the object to be added
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* @key: the key of the object to be added
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*/
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#define hash_add_rcu(hashtable, node, key) \
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hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
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/**
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* hash_hashed - check whether an object is in any hashtable
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* @node: the &struct hlist_node of the object to be checked
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*/
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static inline bool hash_hashed(struct hlist_node *node)
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{
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return !hlist_unhashed(node);
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}
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static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
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{
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unsigned int i;
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for (i = 0; i < sz; i++)
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if (!hlist_empty(&ht[i]))
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return false;
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return true;
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}
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/**
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* hash_empty - check whether a hashtable is empty
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* @hashtable: hashtable to check
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*
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* This has to be a macro since HASH_BITS() will not work on pointers since
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* it calculates the size during preprocessing.
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*/
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#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))
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/**
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* hash_del - remove an object from a hashtable
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* @node: &struct hlist_node of the object to remove
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*/
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static inline void hash_del(struct hlist_node *node)
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{
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hlist_del_init(node);
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}
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/**
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* hash_del_rcu - remove an object from a rcu enabled hashtable
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* @node: &struct hlist_node of the object to remove
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*/
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static inline void hash_del_rcu(struct hlist_node *node)
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{
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hlist_del_init_rcu(node);
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}
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/**
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* hash_for_each - iterate over a hashtable
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* @name: hashtable to iterate
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* @bkt: integer to use as bucket loop cursor
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @obj: the type * to use as a loop cursor for each entry
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* @member: the name of the hlist_node within the struct
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*/
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#define hash_for_each(name, bkt, node, obj, member) \
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for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
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hlist_for_each_entry(obj, node, &name[bkt], member)
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/**
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* hash_for_each_rcu - iterate over a rcu enabled hashtable
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* @name: hashtable to iterate
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* @bkt: integer to use as bucket loop cursor
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @obj: the type * to use as a loop cursor for each entry
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* @member: the name of the hlist_node within the struct
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*/
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#define hash_for_each_rcu(name, bkt, node, obj, member) \
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for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
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hlist_for_each_entry_rcu(obj, node, &name[bkt], member)
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/**
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* hash_for_each_safe - iterate over a hashtable safe against removal of
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* hash entry
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* @name: hashtable to iterate
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* @bkt: integer to use as bucket loop cursor
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @tmp: a &struct used for temporary storage
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* @obj: the type * to use as a loop cursor for each entry
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* @member: the name of the hlist_node within the struct
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*/
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#define hash_for_each_safe(name, bkt, node, tmp, obj, member) \
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for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\
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hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)
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/**
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* hash_for_each_possible - iterate over all possible objects hashing to the
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* same bucket
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* @name: hashtable to iterate
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* @obj: the type * to use as a loop cursor for each entry
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @member: the name of the hlist_node within the struct
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* @key: the key of the objects to iterate over
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*/
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#define hash_for_each_possible(name, obj, node, member, key) \
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hlist_for_each_entry(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
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/**
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* hash_for_each_possible_rcu - iterate over all possible objects hashing to the
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* same bucket in an rcu enabled hashtable
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* in a rcu enabled hashtable
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* @name: hashtable to iterate
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* @obj: the type * to use as a loop cursor for each entry
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @member: the name of the hlist_node within the struct
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* @key: the key of the objects to iterate over
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*/
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#define hash_for_each_possible_rcu(name, obj, node, member, key) \
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hlist_for_each_entry_rcu(obj, node, &name[hash_min(key, HASH_BITS(name))], member)
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/**
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* hash_for_each_possible_safe - iterate over all possible objects hashing to the
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* same bucket safe against removals
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* @name: hashtable to iterate
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* @obj: the type * to use as a loop cursor for each entry
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* @node: the &struct list_head to use as a loop cursor for each entry
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* @tmp: a &struct used for temporary storage
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* @member: the name of the hlist_node within the struct
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* @key: the key of the objects to iterate over
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*/
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#define hash_for_each_possible_safe(name, obj, node, tmp, member, key) \
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hlist_for_each_entry_safe(obj, node, tmp, \
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&name[hash_min(key, HASH_BITS(name))], member)
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#endif
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