Two patches landed for 2.17 are also needed for b2_16:
LU-15808 ptlrpc: ptlrpc_set_wait() use wait_woken LU-18516 quota: use wait_woken for qsd_op_begin0()
Both were already backported to b2_15 after we saw the symptoms at LLNL with 2.15 based Lustre.