reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/ceph/ceph-client/commit/150b41eb9654d09e993407ae522128f5af588e04
        git remote add ceph-client https://github.com/ceph/ceph-client.git
        git fetch --no-tags ceph-client tls_logger
        git checkout 150b41eb9654d09e993407ae522128f5af588e04
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash fs/ceph/