rhashtable: abstract out function to get hash

Split out most of rht_key_hashfn which is calculating the hash into
its own function. This way the hash function can be called separately to
get the hash value.
Acked-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NTom Herbert <tom@quantonium.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/rhashtable.h

@@ -240,34 +240,42 @@ static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
 	return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
 }
 
-static inline unsigned int rht_key_hashfn(
-	struct rhashtable *ht, const struct bucket_table *tbl,
-	const void *key, const struct rhashtable_params params)
+static inline unsigned int rht_key_get_hash(struct rhashtable *ht,
+	const void *key, const struct rhashtable_params params,
+	unsigned int hash_rnd)
 {
 	unsigned int hash;
 
 	/* params must be equal to ht->p if it isn't constant. */
 	if (!__builtin_constant_p(params.key_len))
-		hash = ht->p.hashfn(key, ht->key_len, tbl->hash_rnd);
+		hash = ht->p.hashfn(key, ht->key_len, hash_rnd);
 	else if (params.key_len) {
 		unsigned int key_len = params.key_len;
 
 		if (params.hashfn)
-			hash = params.hashfn(key, key_len, tbl->hash_rnd);
+			hash = params.hashfn(key, key_len, hash_rnd);
 		else if (key_len & (sizeof(u32) - 1))
-			hash = jhash(key, key_len, tbl->hash_rnd);
+			hash = jhash(key, key_len, hash_rnd);
 		else
-			hash = jhash2(key, key_len / sizeof(u32),
-				      tbl->hash_rnd);
+			hash = jhash2(key, key_len / sizeof(u32), hash_rnd);
 	} else {
 		unsigned int key_len = ht->p.key_len;
 
 		if (params.hashfn)
-			hash = params.hashfn(key, key_len, tbl->hash_rnd);
+			hash = params.hashfn(key, key_len, hash_rnd);
 		else
-			hash = jhash(key, key_len, tbl->hash_rnd);
+			hash = jhash(key, key_len, hash_rnd);
 	}
 
+	return hash;
+}
+
+static inline unsigned int rht_key_hashfn(
+	struct rhashtable *ht, const struct bucket_table *tbl,
+	const void *key, const struct rhashtable_params params)
+{
+	unsigned int hash = rht_key_get_hash(ht, key, params, tbl->hash_rnd);
+
 	return rht_bucket_index(tbl, hash);
 }