[PATCH] Don't create files for engines that don't need them

Introduce FIO_NULLIO as a way to control that from the io engine.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/stat.c b/stat.c
index a98539f..a9e87aa 100644
--- a/stat.c
+++ b/stat.c
@@ -205,7 +205,7 @@
 	dev_t dev;
 	char *p;
 
-	if (!td->do_disk_util || (td->io_ops->flags & FIO_NETIO))
+	if (!td->do_disk_util || (td->io_ops->flags & (FIO_NETIO | FIO_NULLIO)))
 		return;
 
 	/*