Most storage drivers call graphdriver.GetFSMagic(home), it is more clean to easy to maintain. So btrfs need to adopt such change. Signed-off-by: Kai Qiang Wu(Kennan) <wkqwu@cn.ibm.com> Upstream-commit: feda5d768439c6ecb8d3c82cee332724302e7cd2 Component: engine