rhashtable: Fix read-side crash during rehash

This patch fixes a typo rhashtable_lookup_compare where we fail
to recompute the hash when looking up the new table.  This causes
elements to be missed and potentially a crash during a resize.
Reported-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

lib/rhashtable.c

@@ -606,8 +606,8 @@ void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
 	rcu_read_lock();
 
 	tbl = rht_dereference_rcu(ht->tbl, ht);
-	hash = key_hashfn(ht, tbl, key);
 restart:
+	hash = key_hashfn(ht, tbl, key);
 	rht_for_each_rcu(he, tbl, hash) {
 		if (!compare(rht_obj(ht, he), arg))
 			continue;