When a user tried to run chgrp command (recursively) to an directory which has a lot of files (4-5 million files), the client hanged and became no response. They tried a couple of time (even other client), but it couldn't be successful due to the following errors.

Apr 27 10:16:25 t2a006166 kernel: [1641802.777783] Lustre: work0-MDT0000-mdc-ffff880d8ae6c800: Connection to service work0-MDT0000 via nid 10.1.7.17@o2ib was lost; in progress operations using this service will wait for recovery to complete.
Apr 27 10:16:25 t2a006166 kernel: [1641802.777991] LustreError: 167-0: This client was evicted by work0-MDT0000; in progress operations using this service will fail.
Apr 27 10:16:25 t2a006166 kernel: [1641802.778116] LustreError: 16507:0:(llite_lib.c:1520:ll_setattr_raw()) mdc_setattr fails: rc = -4