reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?id=d4eac172f8f9f4594056366859b67e589e6124c3
        git remote add chao https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git
        git fetch --no-tags chao feature/fs_param
        git checkout d4eac172f8f9f4594056366859b67e589e6124c3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash fs/f2fs/