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rhashtable: Allow hashfn to be unset

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Since every current rhashtable user uses jhash as their hash
function, the fact that jhash is an inline function causes each
user to generate a copy of its code.

This function provides a solution to this problem by allowing
hashfn to be unset.  In which case rhashtable will automatically
set it to jhash.  Furthermore, if the key length is a multiple
of 4, we will switch over to jhash2.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2015-03-24 00:50:21 +11:00 • committed by David S. Miller
parent de91b25c80
commit 31ccde2dac
2 changed files with 44 additions and 8 deletions
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17
lib/rhashtable.c
View file

@ -532,6 +532,11 @@ static size_t rounded_hashtable_size(const struct rhashtable_params *params)
(unsigned long)params->min_size);
}
static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
{
return jhash2(key, length, seed);
}
/**
* rhashtable_init - initialize a new hash table
* @ht: hash table to be initialized
@ -583,7 +588,7 @@ int rhashtable_init(struct rhashtable *ht,
size = HASH_DEFAULT_SIZE;
if ((!(params->key_len && params->hashfn) && !params->obj_hashfn) ||
if ((!params->key_len && !params->obj_hashfn) ||
(params->obj_hashfn && !params->obj_cmpfn))
return -EINVAL;
@ -610,6 +615,16 @@ int rhashtable_init(struct rhashtable *ht,
else
ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
ht->key_len = ht->p.key_len;
if (!params->hashfn) {
ht->p.hashfn = jhash;
if (!(ht->key_len & (sizeof(u32) - 1))) {
ht->key_len /= sizeof(u32);
ht->p.hashfn = rhashtable_jhash2;
}
}
tbl = bucket_table_alloc(ht, size);
if (tbl == NULL)
return -ENOMEM;