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f89bd6f87a
In order to allow for wider usage of rhashtable, use a special nulls
marker to terminate each chain. The reason for not using the existing
nulls_list is that the prev pointer usage would not be valid as entries
can be linked in two different buckets at the same time.
The 4 nulls base bits can be set through the rhashtable_params structure
like this:
struct rhashtable_params params = {
[...]
.nulls_base = (1U << RHT_BASE_SHIFT),
};
This reduces the hash length from 32 bits to 27 bits.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
320 lines
11 KiB
C
320 lines
11 KiB
C
/*
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* Resizable, Scalable, Concurrent Hash Table
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*
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* Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
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* Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
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*
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* Based on the following paper by Josh Triplett, Paul E. McKenney
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* and Jonathan Walpole:
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* https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
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*
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* Code partially derived from nft_hash
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _LINUX_RHASHTABLE_H
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#define _LINUX_RHASHTABLE_H
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#include <linux/list_nulls.h>
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#include <linux/workqueue.h>
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/*
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* The end of the chain is marked with a special nulls marks which has
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* the following format:
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*
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* +-------+-----------------------------------------------------+-+
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* | Base | Hash |1|
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* +-------+-----------------------------------------------------+-+
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*
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* Base (4 bits) : Reserved to distinguish between multiple tables.
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* Specified via &struct rhashtable_params.nulls_base.
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* Hash (27 bits): Full hash (unmasked) of first element added to bucket
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* 1 (1 bit) : Nulls marker (always set)
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*
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* The remaining bits of the next pointer remain unused for now.
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*/
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#define RHT_BASE_BITS 4
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#define RHT_HASH_BITS 27
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#define RHT_BASE_SHIFT RHT_HASH_BITS
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struct rhash_head {
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struct rhash_head __rcu *next;
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};
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/**
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* struct bucket_table - Table of hash buckets
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* @size: Number of hash buckets
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* @locks_mask: Mask to apply before accessing locks[]
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* @locks: Array of spinlocks protecting individual buckets
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* @buckets: size * hash buckets
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*/
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struct bucket_table {
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size_t size;
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unsigned int locks_mask;
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spinlock_t *locks;
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struct rhash_head __rcu *buckets[];
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};
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typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
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typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
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struct rhashtable;
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/**
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* struct rhashtable_params - Hash table construction parameters
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* @nelem_hint: Hint on number of elements, should be 75% of desired size
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* @key_len: Length of key
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* @key_offset: Offset of key in struct to be hashed
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* @head_offset: Offset of rhash_head in struct to be hashed
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* @hash_rnd: Seed to use while hashing
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* @max_shift: Maximum number of shifts while expanding
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* @min_shift: Minimum number of shifts while shrinking
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* @nulls_base: Base value to generate nulls marker
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* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
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* @hashfn: Function to hash key
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* @obj_hashfn: Function to hash object
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* @grow_decision: If defined, may return true if table should expand
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* @shrink_decision: If defined, may return true if table should shrink
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*/
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struct rhashtable_params {
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size_t nelem_hint;
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size_t key_len;
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size_t key_offset;
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size_t head_offset;
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u32 hash_rnd;
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size_t max_shift;
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size_t min_shift;
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u32 nulls_base;
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size_t locks_mul;
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rht_hashfn_t hashfn;
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rht_obj_hashfn_t obj_hashfn;
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bool (*grow_decision)(const struct rhashtable *ht,
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size_t new_size);
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bool (*shrink_decision)(const struct rhashtable *ht,
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size_t new_size);
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};
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/**
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* struct rhashtable - Hash table handle
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* @tbl: Bucket table
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* @future_tbl: Table under construction during expansion/shrinking
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* @nelems: Number of elements in table
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* @shift: Current size (1 << shift)
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* @p: Configuration parameters
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* @run_work: Deferred worker to expand/shrink asynchronously
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* @mutex: Mutex to protect current/future table swapping
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* @being_destroyed: True if table is set up for destruction
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*/
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struct rhashtable {
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struct bucket_table __rcu *tbl;
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struct bucket_table __rcu *future_tbl;
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atomic_t nelems;
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size_t shift;
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struct rhashtable_params p;
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struct delayed_work run_work;
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struct mutex mutex;
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bool being_destroyed;
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};
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static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
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{
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return NULLS_MARKER(ht->p.nulls_base + hash);
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}
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#define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
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((ptr) = (typeof(ptr)) rht_marker(ht, hash))
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static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
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{
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return ((unsigned long) ptr & 1);
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}
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static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
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{
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return ((unsigned long) ptr) >> 1;
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}
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#ifdef CONFIG_PROVE_LOCKING
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int lockdep_rht_mutex_is_held(struct rhashtable *ht);
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int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
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#else
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static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
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{
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return 1;
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}
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static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
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u32 hash)
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{
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return 1;
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}
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#endif /* CONFIG_PROVE_LOCKING */
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int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
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void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
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bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
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bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size);
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bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size);
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int rhashtable_expand(struct rhashtable *ht);
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int rhashtable_shrink(struct rhashtable *ht);
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void *rhashtable_lookup(struct rhashtable *ht, const void *key);
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void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
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bool (*compare)(void *, void *), void *arg);
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void rhashtable_destroy(struct rhashtable *ht);
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#define rht_dereference(p, ht) \
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rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
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#define rht_dereference_rcu(p, ht) \
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rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
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#define rht_dereference_bucket(p, tbl, hash) \
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rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
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#define rht_dereference_bucket_rcu(p, tbl, hash) \
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rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
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#define rht_entry(tpos, pos, member) \
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({ tpos = container_of(pos, typeof(*tpos), member); 1; })
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/**
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* rht_for_each_continue - continue iterating over hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*/
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#define rht_for_each_continue(pos, head, tbl, hash) \
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for (pos = rht_dereference_bucket(head, tbl, hash); \
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!rht_is_a_nulls(pos); \
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pos = rht_dereference_bucket((pos)->next, tbl, hash))
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/**
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* rht_for_each - iterate over hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*/
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#define rht_for_each(pos, tbl, hash) \
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rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
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/**
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* rht_for_each_entry_continue - continue iterating over hash chain
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*/
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#define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
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for (pos = rht_dereference_bucket(head, tbl, hash); \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
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pos = rht_dereference_bucket((pos)->next, tbl, hash))
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/**
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* rht_for_each_entry - iterate over hash chain of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*/
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#define rht_for_each_entry(tpos, pos, tbl, hash, member) \
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rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
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tbl, hash, member)
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/**
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* rht_for_each_entry_safe - safely iterate over hash chain of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @next: the &struct rhash_head to use as next in loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*
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* This hash chain list-traversal primitive allows for the looped code to
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* remove the loop cursor from the list.
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*/
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#define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
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for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
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next = !rht_is_a_nulls(pos) ? \
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rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
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pos = next)
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/**
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* rht_for_each_rcu_continue - continue iterating over rcu hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_rcu_continue(pos, head, tbl, hash) \
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for (({barrier(); }), \
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pos = rht_dereference_bucket_rcu(head, tbl, hash); \
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!rht_is_a_nulls(pos); \
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pos = rcu_dereference_raw(pos->next))
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/**
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* rht_for_each_rcu - iterate over rcu hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_rcu(pos, tbl, hash) \
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rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
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/**
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* rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
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for (({barrier(); }), \
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pos = rht_dereference_bucket_rcu(head, tbl, hash); \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
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pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
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/**
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* rht_for_each_entry_rcu - iterate over rcu hash chain of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
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rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
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tbl, hash, member)
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#endif /* _LINUX_RHASHTABLE_H */
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