reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?id=45862c2acdb90a83a4c2cfec50251d55ebb5d42a
        git remote add chao https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git
        git fetch --no-tags chao dev-test
        git checkout 45862c2acdb90a83a4c2cfec50251d55ebb5d42a
        # apt-get install sparse
        # sparse version: v0.6.4-73-gfbdde312

        # 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/