reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?id=34cf4084965437b9d1b470067b0b3155dbc119d6
        git remote add brauner-vfs https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
        git fetch --no-tags brauner-vfs vfs.misc
        git checkout 34cf4084965437b9d1b470067b0b3155dbc119d6
        make W=1 O=/tmp/kselftest headers
        make W=1 O=/tmp/kselftest -C tools/testing/selftests
        make W=1 O=/tmp/kselftest -C tools/testing/selftests/bpf