If osp_get_lastfid_from_ost() RPC failed, it will deactivate OST to let user to handle bad OST, but there may be different kinds of errors, some may be trivial, e.g. network issue, it's not necessary to deactivate OST in such cases. Among all the errors, -EFAULT means reading LAST_ID on OST failed, and it should only deactivate OST in this case.