reproduce (this is a W=1 build):
        # https://github.com/gestionlin/linux/commit/a92c7b766c1f707dfd31e87822695e276e9d0aac
        git remote add linyunsheng https://github.com/gestionlin/linux.git
        git fetch --no-tags linyunsheng page_frag_cache_part2_v3_old
        git checkout a92c7b766c1f707dfd31e87822695e276e9d0aac
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash CLIPPY=1 rustdoc