Check for a valid block device size

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/filesetup.c b/filesetup.c
index 464c0f2..cfcfa9a 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -156,6 +156,11 @@
 		return 1;
 	}
 
+	if (!bytes) {
+		log_err("%s: zero sized block device?\n", f->file_name);
+		return 1;
+	}
+
 	f->real_file_size = bytes;
 	return 0;
 }