reproduce (this is a W=1 build):
        # https://github.com/koverstreet/bcachefs/commit/160f8bf55396c94122b638bc2bbf4859b5e1bad8
        git remote add koverstreet-bcachefs https://github.com/koverstreet/bcachefs
        git fetch --no-tags koverstreet-bcachefs latency_debug
        git checkout 160f8bf55396c94122b638bc2bbf4859b5e1bad8
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/