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/*
* Resizable, Scalable, Concurrent Hash Table
*
* Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
* Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
*
* Based on the following paper by Josh Triplett, Paul E. McKenney
* and Jonathan Walpole:
* https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
*
* Code partially derived from nft_hash
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _LINUX_RHASHTABLE_H
#define _LINUX_RHASHTABLE_H
#include <linux/rculist.h>
struct rhash_head {
struct rhash_head __rcu *next;
};
#define INIT_HASH_HEAD(ptr) ((ptr)->next = NULL)
struct bucket_table {
size_t size;
struct rhash_head __rcu *buckets[];
};
typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
struct rhashtable;
/**
* struct rhashtable_params - Hash table construction parameters
* @nelem_hint: Hint on number of elements, should be 75% of desired size
* @key_len: Length of key
* @key_offset: Offset of key in struct to be hashed
* @head_offset: Offset of rhash_head in struct to be hashed
* @hash_rnd: Seed to use while hashing
* @max_shift: Maximum number of shifts while expanding
* @hashfn: Function to hash key
* @obj_hashfn: Function to hash object
* @grow_decision: If defined, may return true if table should expand
* @shrink_decision: If defined, may return true if table should shrink
* @mutex_is_held: Must return true if protecting mutex is held
*/
struct rhashtable_params {
size_t nelem_hint;
size_t key_len;
size_t key_offset;
size_t head_offset;
u32 hash_rnd;
size_t max_shift;
rht_hashfn_t hashfn;
rht_obj_hashfn_t obj_hashfn;
bool (*grow_decision)(const struct rhashtable *ht,
size_t new_size);
bool (*shrink_decision)(const struct rhashtable *ht,
size_t new_size);
int (*mutex_is_held)(void);
};
/**
* struct rhashtable - Hash table handle
* @tbl: Bucket table
* @nelems: Number of elements in table
* @shift: Current size (1 << shift)
* @p: Configuration parameters
*/
struct rhashtable {
struct bucket_table __rcu *tbl;
size_t nelems;
size_t shift;
struct rhashtable_params p;
};
#ifdef CONFIG_PROVE_LOCKING
int lockdep_rht_mutex_is_held(const struct rhashtable *ht);
#else
static inline int lockdep_rht_mutex_is_held(const struct rhashtable *ht)
{
return 1;
}
#endif /* CONFIG_PROVE_LOCKING */
int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len);
u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr);
void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node, gfp_t);
bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node, gfp_t);
void rhashtable_remove_pprev(struct rhashtable *ht, struct rhash_head *obj,
struct rhash_head __rcu **pprev, gfp_t flags);
bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size);
bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size);
int rhashtable_expand(struct rhashtable *ht, gfp_t flags);
int rhashtable_shrink(struct rhashtable *ht, gfp_t flags);
void *rhashtable_lookup(const struct rhashtable *ht, const void *key);
void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash,
bool (*compare)(void *, void *), void *arg);
void rhashtable_destroy(const struct rhashtable *ht);
#define rht_dereference(p, ht) \
rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
#define rht_dereference_rcu(p, ht) \
rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
#define rht_entry(ptr, type, member) container_of(ptr, type, member)
#define rht_entry_safe(ptr, type, member) \
({ \
typeof(ptr) __ptr = (ptr); \
__ptr ? rht_entry(__ptr, type, member) : NULL; \
})
#define rht_next_entry_safe(pos, ht, member) \
({ \
pos ? rht_entry_safe(rht_dereference((pos)->member.next, ht), \
typeof(*(pos)), member) : NULL; \
})
/**
* rht_for_each - iterate over hash chain
* @pos: &struct rhash_head to use as a loop cursor.
* @head: head of the hash chain (struct rhash_head *)
* @ht: pointer to your struct rhashtable
*/
#define rht_for_each(pos, head, ht) \
for (pos = rht_dereference(head, ht); \
pos; \
pos = rht_dereference((pos)->next, ht))
/**
* rht_for_each_entry - iterate over hash chain of given type
* @pos: type * to use as a loop cursor.
* @head: head of the hash chain (struct rhash_head *)
* @ht: pointer to your struct rhashtable
* @member: name of the rhash_head within the hashable struct.
*/
#define rht_for_each_entry(pos, head, ht, member) \
for (pos = rht_entry_safe(rht_dereference(head, ht), \
typeof(*(pos)), member); \
pos; \
pos = rht_next_entry_safe(pos, ht, member))
/**
* rht_for_each_entry_safe - safely iterate over hash chain of given type
* @pos: type * to use as a loop cursor.
* @n: type * to use for temporary next object storage
* @head: head of the hash chain (struct rhash_head *)
* @ht: pointer to your struct rhashtable
* @member: name of the rhash_head within the hashable struct.
*
* This hash chain list-traversal primitive allows for the looped code to
* remove the loop cursor from the list.
*/
#define rht_for_each_entry_safe(pos, n, head, ht, member) \
for (pos = rht_entry_safe(rht_dereference(head, ht), \
typeof(*(pos)), member), \
n = rht_next_entry_safe(pos, ht, member); \
pos; \
pos = n, \
n = rht_next_entry_safe(pos, ht, member))
/**
* rht_for_each_rcu - iterate over rcu hash chain
* @pos: &struct rhash_head to use as a loop cursor.
* @head: head of the hash chain (struct rhash_head *)
* @ht: pointer to your struct rhashtable
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu fkht mutation primitives such as rht_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_rcu(pos, head, ht) \
for (pos = rht_dereference_rcu(head, ht); \
pos; \
pos = rht_dereference_rcu((pos)->next, ht))
/**
* rht_for_each_entry_rcu - iterate over rcu hash chain of given type
* @pos: type * to use as a loop cursor.
* @head: head of the hash chain (struct rhash_head *)
* @member: name of the rhash_head within the hashable struct.
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu fkht mutation primitives such as rht_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_entry_rcu(pos, head, member) \
for (pos = rht_entry_safe(rcu_dereference_raw(head), \
typeof(*(pos)), member); \
pos; \
pos = rht_entry_safe(rcu_dereference_raw((pos)->member.next), \
typeof(*(pos)), member))
#endif /* _LINUX_RHASHTABLE_H */
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