1024 lines
26 KiB
C
1024 lines
26 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:
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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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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/log2.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/jhash.h>
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#include <linux/random.h>
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#include <linux/rhashtable.h>
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#define HASH_DEFAULT_SIZE 64UL
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#define HASH_MIN_SIZE 4UL
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#define BUCKET_LOCKS_PER_CPU 128UL
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/* Base bits plus 1 bit for nulls marker */
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#define HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
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enum {
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RHT_LOCK_NORMAL,
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RHT_LOCK_NESTED,
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RHT_LOCK_NESTED2,
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};
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/* The bucket lock is selected based on the hash and protects mutations
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* on a group of hash buckets.
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*
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* IMPORTANT: When holding the bucket lock of both the old and new table
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* during expansions and shrinking, the old bucket lock must always be
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* acquired first.
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*/
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static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash)
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{
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return &tbl->locks[hash & tbl->locks_mask];
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}
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#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
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#define ASSERT_BUCKET_LOCK(TBL, HASH) \
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BUG_ON(!lockdep_rht_bucket_is_held(TBL, HASH))
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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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{
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return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
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}
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EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
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int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
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{
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spinlock_t *lock = bucket_lock(tbl, hash);
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return (debug_locks) ? lockdep_is_held(lock) : 1;
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}
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EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
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#endif
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static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he)
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{
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return (void *) he - ht->p.head_offset;
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}
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static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash)
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{
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return hash & (tbl->size - 1);
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}
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static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr)
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{
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u32 hash;
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if (unlikely(!ht->p.key_len))
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hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd);
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else
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hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len,
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ht->p.hash_rnd);
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return hash >> HASH_RESERVED_SPACE;
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}
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static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len)
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{
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struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
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u32 hash;
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hash = ht->p.hashfn(key, len, ht->p.hash_rnd);
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hash >>= HASH_RESERVED_SPACE;
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return rht_bucket_index(tbl, hash);
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}
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static u32 head_hashfn(const struct rhashtable *ht,
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const struct bucket_table *tbl,
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const struct rhash_head *he)
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{
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return rht_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he)));
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}
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static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n)
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{
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struct rhash_head __rcu **pprev;
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for (pprev = &tbl->buckets[n];
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!rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n));
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pprev = &rht_dereference_bucket(*pprev, tbl, n)->next)
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;
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return pprev;
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}
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static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl)
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{
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unsigned int i, size;
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#if defined(CONFIG_PROVE_LOCKING)
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unsigned int nr_pcpus = 2;
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#else
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unsigned int nr_pcpus = num_possible_cpus();
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#endif
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nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL);
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size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
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/* Never allocate more than one lock per bucket */
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size = min_t(unsigned int, size, tbl->size);
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if (sizeof(spinlock_t) != 0) {
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#ifdef CONFIG_NUMA
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if (size * sizeof(spinlock_t) > PAGE_SIZE)
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tbl->locks = vmalloc(size * sizeof(spinlock_t));
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else
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#endif
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tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
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GFP_KERNEL);
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if (!tbl->locks)
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return -ENOMEM;
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for (i = 0; i < size; i++)
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spin_lock_init(&tbl->locks[i]);
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}
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tbl->locks_mask = size - 1;
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return 0;
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}
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static void bucket_table_free(const struct bucket_table *tbl)
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{
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if (tbl)
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kvfree(tbl->locks);
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kvfree(tbl);
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}
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static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
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size_t nbuckets)
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{
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struct bucket_table *tbl;
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size_t size;
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int i;
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size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
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tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
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if (tbl == NULL)
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tbl = vzalloc(size);
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if (tbl == NULL)
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return NULL;
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tbl->size = nbuckets;
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if (alloc_bucket_locks(ht, tbl) < 0) {
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bucket_table_free(tbl);
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return NULL;
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}
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for (i = 0; i < nbuckets; i++)
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INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
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return tbl;
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}
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/**
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* rht_grow_above_75 - returns true if nelems > 0.75 * table-size
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* @ht: hash table
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* @new_size: new table size
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*/
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bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
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{
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/* Expand table when exceeding 75% load */
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return atomic_read(&ht->nelems) > (new_size / 4 * 3);
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}
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EXPORT_SYMBOL_GPL(rht_grow_above_75);
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/**
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* rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
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* @ht: hash table
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* @new_size: new table size
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*/
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bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
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{
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/* Shrink table beneath 30% load */
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return atomic_read(&ht->nelems) < (new_size * 3 / 10);
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}
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EXPORT_SYMBOL_GPL(rht_shrink_below_30);
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static void hashtable_chain_unzip(const struct rhashtable *ht,
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const struct bucket_table *new_tbl,
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struct bucket_table *old_tbl,
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size_t old_hash)
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{
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struct rhash_head *he, *p, *next;
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spinlock_t *new_bucket_lock, *new_bucket_lock2 = NULL;
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unsigned int new_hash, new_hash2;
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ASSERT_BUCKET_LOCK(old_tbl, old_hash);
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/* Old bucket empty, no work needed. */
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p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
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old_hash);
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if (rht_is_a_nulls(p))
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return;
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new_hash = new_hash2 = head_hashfn(ht, new_tbl, p);
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new_bucket_lock = bucket_lock(new_tbl, new_hash);
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/* Advance the old bucket pointer one or more times until it
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* reaches a node that doesn't hash to the same bucket as the
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* previous node p. Call the previous node p;
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*/
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rht_for_each_continue(he, p->next, old_tbl, old_hash) {
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new_hash2 = head_hashfn(ht, new_tbl, he);
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if (new_hash != new_hash2)
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break;
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p = he;
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}
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rcu_assign_pointer(old_tbl->buckets[old_hash], p->next);
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spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
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/* If we have encountered an entry that maps to a different bucket in
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* the new table, lock down that bucket as well as we might cut off
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* the end of the chain.
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*/
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new_bucket_lock2 = bucket_lock(new_tbl, new_hash);
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if (new_bucket_lock != new_bucket_lock2)
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spin_lock_bh_nested(new_bucket_lock2, RHT_LOCK_NESTED2);
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/* Find the subsequent node which does hash to the same
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* bucket as node P, or NULL if no such node exists.
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*/
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INIT_RHT_NULLS_HEAD(next, ht, old_hash);
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if (!rht_is_a_nulls(he)) {
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rht_for_each_continue(he, he->next, old_tbl, old_hash) {
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if (head_hashfn(ht, new_tbl, he) == new_hash) {
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next = he;
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break;
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}
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}
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}
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/* Set p's next pointer to that subsequent node pointer,
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* bypassing the nodes which do not hash to p's bucket
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*/
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rcu_assign_pointer(p->next, next);
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if (new_bucket_lock != new_bucket_lock2)
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spin_unlock_bh(new_bucket_lock2);
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spin_unlock_bh(new_bucket_lock);
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}
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static void link_old_to_new(struct bucket_table *new_tbl,
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unsigned int new_hash, struct rhash_head *entry)
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{
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spinlock_t *new_bucket_lock;
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new_bucket_lock = bucket_lock(new_tbl, new_hash);
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spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
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rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry);
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spin_unlock_bh(new_bucket_lock);
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}
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/**
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* rhashtable_expand - Expand hash table while allowing concurrent lookups
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* @ht: the hash table to expand
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*
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* A secondary bucket array is allocated and the hash entries are migrated
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* while keeping them on both lists until the end of the RCU grace period.
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*
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* This function may only be called in a context where it is safe to call
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* synchronize_rcu(), e.g. not within a rcu_read_lock() section.
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*
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* The caller must ensure that no concurrent resizing occurs by holding
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* ht->mutex.
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*
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* It is valid to have concurrent insertions and deletions protected by per
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* bucket locks or concurrent RCU protected lookups and traversals.
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*/
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int rhashtable_expand(struct rhashtable *ht)
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{
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struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
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struct rhash_head *he;
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spinlock_t *old_bucket_lock;
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unsigned int new_hash, old_hash;
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bool complete = false;
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ASSERT_RHT_MUTEX(ht);
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if (ht->p.max_shift && ht->shift >= ht->p.max_shift)
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return 0;
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new_tbl = bucket_table_alloc(ht, old_tbl->size * 2);
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if (new_tbl == NULL)
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return -ENOMEM;
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ht->shift++;
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/* Make insertions go into the new, empty table right away. Deletions
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* and lookups will be attempted in both tables until we synchronize.
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* The synchronize_rcu() guarantees for the new table to be picked up
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* so no new additions go into the old table while we relink.
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*/
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rcu_assign_pointer(ht->future_tbl, new_tbl);
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synchronize_rcu();
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/* For each new bucket, search the corresponding old bucket for the
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* first entry that hashes to the new bucket, and link the end of
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* newly formed bucket chain (containing entries added to future
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* table) to that entry. Since all the entries which will end up in
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* the new bucket appear in the same old bucket, this constructs an
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* entirely valid new hash table, but with multiple buckets
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* "zipped" together into a single imprecise chain.
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*/
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for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
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old_hash = rht_bucket_index(old_tbl, new_hash);
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old_bucket_lock = bucket_lock(old_tbl, old_hash);
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spin_lock_bh(old_bucket_lock);
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rht_for_each(he, old_tbl, old_hash) {
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if (head_hashfn(ht, new_tbl, he) == new_hash) {
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link_old_to_new(new_tbl, new_hash, he);
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break;
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}
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}
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spin_unlock_bh(old_bucket_lock);
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}
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/* Publish the new table pointer. Lookups may now traverse
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* the new table, but they will not benefit from any
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* additional efficiency until later steps unzip the buckets.
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*/
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rcu_assign_pointer(ht->tbl, new_tbl);
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/* Unzip interleaved hash chains */
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while (!complete && !ht->being_destroyed) {
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/* Wait for readers. All new readers will see the new
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* table, and thus no references to the old table will
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* remain.
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*/
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synchronize_rcu();
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/* For each bucket in the old table (each of which
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* contains items from multiple buckets of the new
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* table): ...
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*/
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complete = true;
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for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
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struct rhash_head *head;
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old_bucket_lock = bucket_lock(old_tbl, old_hash);
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spin_lock_bh(old_bucket_lock);
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hashtable_chain_unzip(ht, new_tbl, old_tbl, old_hash);
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head = rht_dereference_bucket(old_tbl->buckets[old_hash],
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old_tbl, old_hash);
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if (!rht_is_a_nulls(head))
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complete = false;
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spin_unlock_bh(old_bucket_lock);
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}
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}
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bucket_table_free(old_tbl);
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return 0;
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}
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EXPORT_SYMBOL_GPL(rhashtable_expand);
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/**
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* rhashtable_shrink - Shrink hash table while allowing concurrent lookups
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* @ht: the hash table to shrink
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*
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* This function may only be called in a context where it is safe to call
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* synchronize_rcu(), e.g. not within a rcu_read_lock() section.
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*
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* The caller must ensure that no concurrent resizing occurs by holding
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* ht->mutex.
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*
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* The caller must ensure that no concurrent table mutations take place.
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* It is however valid to have concurrent lookups if they are RCU protected.
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*
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* It is valid to have concurrent insertions and deletions protected by per
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* bucket locks or concurrent RCU protected lookups and traversals.
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*/
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int rhashtable_shrink(struct rhashtable *ht)
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{
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struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht);
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spinlock_t *new_bucket_lock, *old_bucket_lock1, *old_bucket_lock2;
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unsigned int new_hash;
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ASSERT_RHT_MUTEX(ht);
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if (ht->shift <= ht->p.min_shift)
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return 0;
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new_tbl = bucket_table_alloc(ht, tbl->size / 2);
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if (new_tbl == NULL)
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return -ENOMEM;
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rcu_assign_pointer(ht->future_tbl, new_tbl);
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synchronize_rcu();
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/* Link the first entry in the old bucket to the end of the
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* bucket in the new table. As entries are concurrently being
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* added to the new table, lock down the new bucket. As we
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* always divide the size in half when shrinking, each bucket
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* in the new table maps to exactly two buckets in the old
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* table.
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*
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* As removals can occur concurrently on the old table, we need
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* to lock down both matching buckets in the old table.
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*/
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for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
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old_bucket_lock1 = bucket_lock(tbl, new_hash);
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old_bucket_lock2 = bucket_lock(tbl, new_hash + new_tbl->size);
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new_bucket_lock = bucket_lock(new_tbl, new_hash);
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spin_lock_bh(old_bucket_lock1);
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spin_lock_bh_nested(old_bucket_lock2, RHT_LOCK_NESTED);
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spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED2);
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rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
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tbl->buckets[new_hash]);
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rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
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tbl->buckets[new_hash + new_tbl->size]);
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spin_unlock_bh(new_bucket_lock);
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spin_unlock_bh(old_bucket_lock2);
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spin_unlock_bh(old_bucket_lock1);
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}
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/* Publish the new, valid hash table */
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rcu_assign_pointer(ht->tbl, new_tbl);
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ht->shift--;
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/* Wait for readers. No new readers will have references to the
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* old hash table.
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*/
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synchronize_rcu();
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bucket_table_free(tbl);
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return 0;
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}
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EXPORT_SYMBOL_GPL(rhashtable_shrink);
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static void rht_deferred_worker(struct work_struct *work)
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{
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struct rhashtable *ht;
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struct bucket_table *tbl;
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ht = container_of(work, struct rhashtable, run_work.work);
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mutex_lock(&ht->mutex);
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tbl = rht_dereference(ht->tbl, ht);
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if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
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rhashtable_expand(ht);
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else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size))
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rhashtable_shrink(ht);
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mutex_unlock(&ht->mutex);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_insert - insert object into hash hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
*
|
|
* Will take a per bucket spinlock to protect against mutual mutations
|
|
* on the same bucket. Multiple insertions may occur in parallel unless
|
|
* they map to the same bucket lock.
|
|
*
|
|
* It is safe to call this function from atomic context.
|
|
*
|
|
* Will trigger an automatic deferred table resizing if the size grows
|
|
* beyond the watermark indicated by grow_decision() which can be passed
|
|
* to rhashtable_init().
|
|
*/
|
|
void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
|
|
{
|
|
struct bucket_table *tbl;
|
|
struct rhash_head *head;
|
|
spinlock_t *lock;
|
|
unsigned hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
hash = head_hashfn(ht, tbl, obj);
|
|
lock = bucket_lock(tbl, hash);
|
|
|
|
spin_lock_bh(lock);
|
|
head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
|
|
if (rht_is_a_nulls(head))
|
|
INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
|
|
else
|
|
RCU_INIT_POINTER(obj->next, head);
|
|
|
|
rcu_assign_pointer(tbl->buckets[hash], obj);
|
|
spin_unlock_bh(lock);
|
|
|
|
atomic_inc(&ht->nelems);
|
|
|
|
/* Only grow the table if no resizing is currently in progress. */
|
|
if (ht->tbl != ht->future_tbl &&
|
|
ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
|
|
schedule_delayed_work(&ht->run_work, 0);
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_insert);
|
|
|
|
/**
|
|
* rhashtable_remove - remove object from hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
*
|
|
* Since the hash chain is single linked, the removal operation needs to
|
|
* walk the bucket chain upon removal. The removal operation is thus
|
|
* considerable slow if the hash table is not correctly sized.
|
|
*
|
|
* Will automatically shrink the table via rhashtable_expand() if the the
|
|
* shrink_decision function specified at rhashtable_init() returns true.
|
|
*
|
|
* The caller must ensure that no concurrent table mutations occur. It is
|
|
* however valid to have concurrent lookups if they are RCU protected.
|
|
*/
|
|
bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
|
|
{
|
|
struct bucket_table *tbl;
|
|
struct rhash_head __rcu **pprev;
|
|
struct rhash_head *he;
|
|
spinlock_t *lock;
|
|
unsigned int hash;
|
|
|
|
rcu_read_lock();
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
hash = head_hashfn(ht, tbl, obj);
|
|
|
|
lock = bucket_lock(tbl, hash);
|
|
spin_lock_bh(lock);
|
|
|
|
restart:
|
|
pprev = &tbl->buckets[hash];
|
|
rht_for_each(he, tbl, hash) {
|
|
if (he != obj) {
|
|
pprev = &he->next;
|
|
continue;
|
|
}
|
|
|
|
rcu_assign_pointer(*pprev, obj->next);
|
|
atomic_dec(&ht->nelems);
|
|
|
|
spin_unlock_bh(lock);
|
|
|
|
if (ht->tbl != ht->future_tbl &&
|
|
ht->p.shrink_decision &&
|
|
ht->p.shrink_decision(ht, tbl->size))
|
|
schedule_delayed_work(&ht->run_work, 0);
|
|
|
|
rcu_read_unlock();
|
|
|
|
return true;
|
|
}
|
|
|
|
if (tbl != rht_dereference_rcu(ht->tbl, ht)) {
|
|
spin_unlock_bh(lock);
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
hash = head_hashfn(ht, tbl, obj);
|
|
|
|
lock = bucket_lock(tbl, hash);
|
|
spin_lock_bh(lock);
|
|
goto restart;
|
|
}
|
|
|
|
spin_unlock_bh(lock);
|
|
rcu_read_unlock();
|
|
|
|
return false;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_remove);
|
|
|
|
/**
|
|
* rhashtable_lookup - lookup key in hash table
|
|
* @ht: hash table
|
|
* @key: pointer to key
|
|
*
|
|
* Computes the hash value for the key and traverses the bucket chain looking
|
|
* for a entry with an identical key. The first matching entry is returned.
|
|
*
|
|
* This lookup function may only be used for fixed key hash table (key_len
|
|
* paramter set). It will BUG() if used inappropriately.
|
|
*
|
|
* Lookups may occur in parallel with hashtable mutations and resizing.
|
|
*/
|
|
void *rhashtable_lookup(struct rhashtable *ht, const void *key)
|
|
{
|
|
const struct bucket_table *tbl, *old_tbl;
|
|
struct rhash_head *he;
|
|
u32 hash;
|
|
|
|
BUG_ON(!ht->p.key_len);
|
|
|
|
rcu_read_lock();
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
hash = key_hashfn(ht, key, ht->p.key_len);
|
|
restart:
|
|
rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) {
|
|
if (memcmp(rht_obj(ht, he) + ht->p.key_offset, key,
|
|
ht->p.key_len))
|
|
continue;
|
|
rcu_read_unlock();
|
|
return rht_obj(ht, he);
|
|
}
|
|
|
|
if (unlikely(tbl != old_tbl)) {
|
|
tbl = old_tbl;
|
|
goto restart;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup);
|
|
|
|
/**
|
|
* rhashtable_lookup_compare - search hash table with compare function
|
|
* @ht: hash table
|
|
* @key: the pointer to the key
|
|
* @compare: compare function, must return true on match
|
|
* @arg: argument passed on to compare function
|
|
*
|
|
* Traverses the bucket chain behind the provided hash value and calls the
|
|
* specified compare function for each entry.
|
|
*
|
|
* Lookups may occur in parallel with hashtable mutations and resizing.
|
|
*
|
|
* Returns the first entry on which the compare function returned true.
|
|
*/
|
|
void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
|
|
bool (*compare)(void *, void *), void *arg)
|
|
{
|
|
const struct bucket_table *tbl, *old_tbl;
|
|
struct rhash_head *he;
|
|
u32 hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
hash = key_hashfn(ht, key, ht->p.key_len);
|
|
restart:
|
|
rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) {
|
|
if (!compare(rht_obj(ht, he), arg))
|
|
continue;
|
|
rcu_read_unlock();
|
|
return rht_obj(ht, he);
|
|
}
|
|
|
|
if (unlikely(tbl != old_tbl)) {
|
|
tbl = old_tbl;
|
|
goto restart;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
|
|
|
|
static size_t rounded_hashtable_size(struct rhashtable_params *params)
|
|
{
|
|
return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
|
|
1UL << params->min_shift);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_init - initialize a new hash table
|
|
* @ht: hash table to be initialized
|
|
* @params: configuration parameters
|
|
*
|
|
* Initializes a new hash table based on the provided configuration
|
|
* parameters. A table can be configured either with a variable or
|
|
* fixed length key:
|
|
*
|
|
* Configuration Example 1: Fixed length keys
|
|
* struct test_obj {
|
|
* int key;
|
|
* void * my_member;
|
|
* struct rhash_head node;
|
|
* };
|
|
*
|
|
* struct rhashtable_params params = {
|
|
* .head_offset = offsetof(struct test_obj, node),
|
|
* .key_offset = offsetof(struct test_obj, key),
|
|
* .key_len = sizeof(int),
|
|
* .hashfn = jhash,
|
|
* .nulls_base = (1U << RHT_BASE_SHIFT),
|
|
* };
|
|
*
|
|
* Configuration Example 2: Variable length keys
|
|
* struct test_obj {
|
|
* [...]
|
|
* struct rhash_head node;
|
|
* };
|
|
*
|
|
* u32 my_hash_fn(const void *data, u32 seed)
|
|
* {
|
|
* struct test_obj *obj = data;
|
|
*
|
|
* return [... hash ...];
|
|
* }
|
|
*
|
|
* struct rhashtable_params params = {
|
|
* .head_offset = offsetof(struct test_obj, node),
|
|
* .hashfn = jhash,
|
|
* .obj_hashfn = my_hash_fn,
|
|
* };
|
|
*/
|
|
int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
|
|
{
|
|
struct bucket_table *tbl;
|
|
size_t size;
|
|
|
|
size = HASH_DEFAULT_SIZE;
|
|
|
|
if ((params->key_len && !params->hashfn) ||
|
|
(!params->key_len && !params->obj_hashfn))
|
|
return -EINVAL;
|
|
|
|
if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
|
|
return -EINVAL;
|
|
|
|
params->min_shift = max_t(size_t, params->min_shift,
|
|
ilog2(HASH_MIN_SIZE));
|
|
|
|
if (params->nelem_hint)
|
|
size = rounded_hashtable_size(params);
|
|
|
|
memset(ht, 0, sizeof(*ht));
|
|
mutex_init(&ht->mutex);
|
|
memcpy(&ht->p, params, sizeof(*params));
|
|
|
|
if (params->locks_mul)
|
|
ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
|
|
else
|
|
ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
|
|
|
|
tbl = bucket_table_alloc(ht, size);
|
|
if (tbl == NULL)
|
|
return -ENOMEM;
|
|
|
|
ht->shift = ilog2(tbl->size);
|
|
RCU_INIT_POINTER(ht->tbl, tbl);
|
|
RCU_INIT_POINTER(ht->future_tbl, tbl);
|
|
|
|
if (!ht->p.hash_rnd)
|
|
get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
|
|
|
|
if (ht->p.grow_decision || ht->p.shrink_decision)
|
|
INIT_DEFERRABLE_WORK(&ht->run_work, rht_deferred_worker);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_init);
|
|
|
|
/**
|
|
* rhashtable_destroy - destroy hash table
|
|
* @ht: the hash table to destroy
|
|
*
|
|
* Frees the bucket array. This function is not rcu safe, therefore the caller
|
|
* has to make sure that no resizing may happen by unpublishing the hashtable
|
|
* and waiting for the quiescent cycle before releasing the bucket array.
|
|
*/
|
|
void rhashtable_destroy(struct rhashtable *ht)
|
|
{
|
|
ht->being_destroyed = true;
|
|
|
|
mutex_lock(&ht->mutex);
|
|
|
|
cancel_delayed_work(&ht->run_work);
|
|
bucket_table_free(rht_dereference(ht->tbl, ht));
|
|
|
|
mutex_unlock(&ht->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_destroy);
|
|
|
|
/**************************************************************************
|
|
* Self Test
|
|
**************************************************************************/
|
|
|
|
#ifdef CONFIG_TEST_RHASHTABLE
|
|
|
|
#define TEST_HT_SIZE 8
|
|
#define TEST_ENTRIES 2048
|
|
#define TEST_PTR ((void *) 0xdeadbeef)
|
|
#define TEST_NEXPANDS 4
|
|
|
|
struct test_obj {
|
|
void *ptr;
|
|
int value;
|
|
struct rhash_head node;
|
|
};
|
|
|
|
static int __init test_rht_lookup(struct rhashtable *ht)
|
|
{
|
|
unsigned int i;
|
|
|
|
for (i = 0; i < TEST_ENTRIES * 2; i++) {
|
|
struct test_obj *obj;
|
|
bool expected = !(i % 2);
|
|
u32 key = i;
|
|
|
|
obj = rhashtable_lookup(ht, &key);
|
|
|
|
if (expected && !obj) {
|
|
pr_warn("Test failed: Could not find key %u\n", key);
|
|
return -ENOENT;
|
|
} else if (!expected && obj) {
|
|
pr_warn("Test failed: Unexpected entry found for key %u\n",
|
|
key);
|
|
return -EEXIST;
|
|
} else if (expected && obj) {
|
|
if (obj->ptr != TEST_PTR || obj->value != i) {
|
|
pr_warn("Test failed: Lookup value mismatch %p!=%p, %u!=%u\n",
|
|
obj->ptr, TEST_PTR, obj->value, i);
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void test_bucket_stats(struct rhashtable *ht, bool quiet)
|
|
{
|
|
unsigned int cnt, rcu_cnt, i, total = 0;
|
|
struct rhash_head *pos;
|
|
struct test_obj *obj;
|
|
struct bucket_table *tbl;
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
for (i = 0; i < tbl->size; i++) {
|
|
rcu_cnt = cnt = 0;
|
|
|
|
if (!quiet)
|
|
pr_info(" [%#4x/%zu]", i, tbl->size);
|
|
|
|
rht_for_each_entry_rcu(obj, pos, tbl, i, node) {
|
|
cnt++;
|
|
total++;
|
|
if (!quiet)
|
|
pr_cont(" [%p],", obj);
|
|
}
|
|
|
|
rht_for_each_entry_rcu(obj, pos, tbl, i, node)
|
|
rcu_cnt++;
|
|
|
|
if (rcu_cnt != cnt)
|
|
pr_warn("Test failed: Chain count mismach %d != %d",
|
|
cnt, rcu_cnt);
|
|
|
|
if (!quiet)
|
|
pr_cont("\n [%#x] first element: %p, chain length: %u\n",
|
|
i, tbl->buckets[i], cnt);
|
|
}
|
|
|
|
pr_info(" Traversal complete: counted=%u, nelems=%u, entries=%d\n",
|
|
total, atomic_read(&ht->nelems), TEST_ENTRIES);
|
|
|
|
if (total != atomic_read(&ht->nelems) || total != TEST_ENTRIES)
|
|
pr_warn("Test failed: Total count mismatch ^^^");
|
|
}
|
|
|
|
static int __init test_rhashtable(struct rhashtable *ht)
|
|
{
|
|
struct bucket_table *tbl;
|
|
struct test_obj *obj;
|
|
struct rhash_head *pos, *next;
|
|
int err;
|
|
unsigned int i;
|
|
|
|
/*
|
|
* Insertion Test:
|
|
* Insert TEST_ENTRIES into table with all keys even numbers
|
|
*/
|
|
pr_info(" Adding %d keys\n", TEST_ENTRIES);
|
|
for (i = 0; i < TEST_ENTRIES; i++) {
|
|
struct test_obj *obj;
|
|
|
|
obj = kzalloc(sizeof(*obj), GFP_KERNEL);
|
|
if (!obj) {
|
|
err = -ENOMEM;
|
|
goto error;
|
|
}
|
|
|
|
obj->ptr = TEST_PTR;
|
|
obj->value = i * 2;
|
|
|
|
rhashtable_insert(ht, &obj->node);
|
|
}
|
|
|
|
rcu_read_lock();
|
|
test_bucket_stats(ht, true);
|
|
test_rht_lookup(ht);
|
|
rcu_read_unlock();
|
|
|
|
for (i = 0; i < TEST_NEXPANDS; i++) {
|
|
pr_info(" Table expansion iteration %u...\n", i);
|
|
mutex_lock(&ht->mutex);
|
|
rhashtable_expand(ht);
|
|
mutex_unlock(&ht->mutex);
|
|
|
|
rcu_read_lock();
|
|
pr_info(" Verifying lookups...\n");
|
|
test_rht_lookup(ht);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
for (i = 0; i < TEST_NEXPANDS; i++) {
|
|
pr_info(" Table shrinkage iteration %u...\n", i);
|
|
mutex_lock(&ht->mutex);
|
|
rhashtable_shrink(ht);
|
|
mutex_unlock(&ht->mutex);
|
|
|
|
rcu_read_lock();
|
|
pr_info(" Verifying lookups...\n");
|
|
test_rht_lookup(ht);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
rcu_read_lock();
|
|
test_bucket_stats(ht, true);
|
|
rcu_read_unlock();
|
|
|
|
pr_info(" Deleting %d keys\n", TEST_ENTRIES);
|
|
for (i = 0; i < TEST_ENTRIES; i++) {
|
|
u32 key = i * 2;
|
|
|
|
obj = rhashtable_lookup(ht, &key);
|
|
BUG_ON(!obj);
|
|
|
|
rhashtable_remove(ht, &obj->node);
|
|
kfree(obj);
|
|
}
|
|
|
|
return 0;
|
|
|
|
error:
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
for (i = 0; i < tbl->size; i++)
|
|
rht_for_each_entry_safe(obj, pos, next, tbl, i, node)
|
|
kfree(obj);
|
|
|
|
return err;
|
|
}
|
|
|
|
static int __init test_rht_init(void)
|
|
{
|
|
struct rhashtable ht;
|
|
struct rhashtable_params params = {
|
|
.nelem_hint = TEST_HT_SIZE,
|
|
.head_offset = offsetof(struct test_obj, node),
|
|
.key_offset = offsetof(struct test_obj, value),
|
|
.key_len = sizeof(int),
|
|
.hashfn = jhash,
|
|
.nulls_base = (3U << RHT_BASE_SHIFT),
|
|
.grow_decision = rht_grow_above_75,
|
|
.shrink_decision = rht_shrink_below_30,
|
|
};
|
|
int err;
|
|
|
|
pr_info("Running resizable hashtable tests...\n");
|
|
|
|
err = rhashtable_init(&ht, ¶ms);
|
|
if (err < 0) {
|
|
pr_warn("Test failed: Unable to initialize hashtable: %d\n",
|
|
err);
|
|
return err;
|
|
}
|
|
|
|
err = test_rhashtable(&ht);
|
|
|
|
rhashtable_destroy(&ht);
|
|
|
|
return err;
|
|
}
|
|
|
|
subsys_initcall(test_rht_init);
|
|
|
|
#endif /* CONFIG_TEST_RHASHTABLE */
|