OverlayFS is supported on top of btrfs as of Linux Kernel 4.7. Skip the hard enforcement when on kernel 4.7 or newer and respect the kernel check override flag on older kernels. https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature Signed-off-by: Derek McGowan <derek@mcgstyle.net> Upstream-commit: f64a4ad008e68996afcec3ab34a869887716f944 Component: engine