rhashtable: Eliminate unnecessary branch in rht_key_hashfn

When rht_key_hashfn is called from rhashtable itself and params
is equal to ht->p, there is no point in checking params.key_len
and falling back to ht->p.key_len.

For some reason gcc couldn't figure out that params is the same
as ht->p.  So let's help it by only checking params.key_len when
it's a constant.

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>

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 89d102270570aa114aae729f7cee67d38a42b347..3851952781d7c1a1b82f60156ed71b0195ae1346 100644 (file)
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -199,8 +199,12 @@ static inline unsigned int rht_key_hashfn(
        struct rhashtable *ht, const struct bucket_table *tbl,
        const void *key, const struct rhashtable_params params)
 {
-       return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?:
-                                                       ht->p.key_len,
+       /* params must be equal to ht->p if it isn't constant. */
+       unsigned key_len = __builtin_constant_p(params.key_len) ?
+                          (params.key_len ?: ht->p.key_len) :
+                          params.key_len;
+
+       return rht_bucket_index(tbl, params.hashfn(key, key_len,
                                                   tbl->hash_rnd));
 }