genetlink: use idr_alloc_cyclic for family->id assignment

When allocating the next family->id it makes more sense to use
idr_alloc_cyclic to avoid re-using a previously used family->id as much
as possible.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/genetlink.c

@@ -362,8 +362,8 @@ int genl_register_family(struct genl_family *family)
 	} else
 		family->attrbuf = NULL;
 
-	family->id = idr_alloc(&genl_fam_idr, family,
-			       start, end + 1, GFP_KERNEL);
+	family->id = idr_alloc_cyclic(&genl_fam_idr, family,
+				      start, end + 1, GFP_KERNEL);
 	if (family->id < 0) {
 		err = family->id;
 		goto errout_free;