/*
* 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>
#include <linux/workqueue.h>
struct rhash_head {
struct rhash_head __rcu *next;
};
#define INIT_HASH_HEAD(ptr) ((ptr)->next = NULL)
/**
* struct bucket_table - Table of hash buckets
* @size: Number of hash buckets
* @locks_mask: Mask to apply before accessing locks[]
* @locks: Array of spinlocks protecting individual buckets
* @buckets: size * hash buckets
*/
struct bucket_table {
size_t size;
unsigned int locks_mask;
spinlock_t *locks;
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
* @min_shift: Minimum number of shifts while shrinking
* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
* @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
*/
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;
size_t min_shift;
size_t locks_mul;
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);
};
/**
* struct rhashtable - Hash table handle
* @tbl: Bucket table
* @future_tbl: Table under construction during expansion/shrinking
* @nelems: Number of elements in table
* @shift: Current size (1 << shift)
* @p: Configuration parameters
* @run_work: Deferred worker to expand/shrink asynchronously
* @mutex: Mutex to protect current/future table swapping
* @being_destroyed: True if table is set up for destruction
*/
struct rhashtable {
struct bucket_table __rcu *tbl;
struct bucket_table __rcu *future_tbl;
atomic_t nelems;
size_t shift;
struct rhashtable_params p;
struct delayed_work run_work;
struct mutex mutex;
bool being_destroyed;
};
#ifdef CONFIG_PROVE_LOCKING
int lockdep_rht_mutex_is_held(struct rhashtable *ht);
int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
#else
static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
{
return 1;
}
static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
u32 hash)
{
return 1;
}
#endif /* CONFIG_PROVE_LOCKING */
int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
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);
int rhashtable_shrink(struct rhashtable *ht);
void *rhashtable_lookup(struct rhashtable *ht, const void *key);
void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
bool (*compare)(void *, void *), void *arg);
void rhashtable_destroy(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_dereference_bucket(p, tbl, hash) \
rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
#define rht_dereference_bucket_rcu(p, tbl, hash) \
rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
#define rht_entry(tpos, pos, member) \
({ tpos = container_of(pos, typeof(*tpos), member); 1; })
/**
* rht_for_each_continue - continue iterating over hash chain
* @pos: the &struct rhash_head to use as a loop cursor.
* @head: the previous &struct rhash_head to continue from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*/
#define rht_for_each_continue(pos, head, tbl, hash) \
for (pos = rht_dereference_bucket(head, tbl, hash); \
pos; \
pos = rht_dereference_bucket((pos)->next, tbl, hash))
/**
* rht_for_each - iterate over hash chain
* @pos: the &struct rhash_head to use as a loop cursor.
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*/
#define rht_for_each(pos, tbl, hash) \
rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
/**
* rht_for_each_entry_continue - continue iterating over hash chain
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
* @head: the previous &struct rhash_head to continue from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
*/
#define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
for (pos = rht_dereference_bucket(head, tbl, hash); \
pos && rht_entry(tpos, pos, member); \
pos = rht_dereference_bucket((pos)->next, tbl, hash))
/**
* rht_for_each_entry - iterate over hash chain of given type
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
*/
#define rht_for_each_entry(tpos, pos, tbl, hash, member) \
rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
tbl, hash, member)
/**
* rht_for_each_entry_safe - safely iterate over hash chain of given type
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
* @next: the &struct rhash_head to use as next in loop cursor.
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct 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(tpos, pos, next, tbl, hash, member) \
for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
next = pos ? rht_dereference_bucket(pos->next, tbl, hash) \
: NULL; \
pos && rht_entry(tpos, pos, member); \
pos = next)
/**
* rht_for_each_rcu_continue - continue iterating over rcu hash chain
* @pos: the &struct rhash_head to use as a loop cursor.
* @head: the previous &struct rhash_head to continue from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_rcu_continue(pos, head, tbl, hash) \
for (({barrier(); }), \
pos = rht_dereference_bucket_rcu(head, tbl, hash); \
pos; \
pos = rcu_dereference_raw(pos->next))
/**
* rht_for_each_rcu - iterate over rcu hash chain
* @pos: the &struct rhash_head to use as a loop cursor.
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_rcu(pos, tbl, hash) \
rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
/**
* rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
* @head: the previous &struct rhash_head to continue from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
for (({barrier(); }), \
pos = rht_dereference_bucket_rcu(head, tbl, hash); \
pos && rht_entry(tpos, pos, member); \
pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
/**
* rht_for_each_entry_rcu - iterate over rcu hash chain of given type
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
*
* This hash chain list-traversal primitive may safely run concurrently with
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
tbl, hash, member)
#endif /* _LINUX_RHASHTABLE_H */
