[LU-8420] unexpected? client eviction after bulk transfer timeout

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.10.0
• Labels: patch
• Severity: 3
• Assignee: WC Triage
• Reporter: Vladimir Saveliev

Description

The following scenario leading to client's eviction has been observed in acceptance testing:

1) client 1 owns PW lock on file A and sends write rpc to ost
2) ost initiates a bulk transfer which gets lost somewhere in networks
3) client 2 enqueues PR lock on file A
4) the server sees the incompatible lock, sends blocking ast to client 1 and starts waiting until client 1 cancels the lock.
5) bulk transfer timeouts, but client 1 does not get a reply in that case.

int tgt_brw_write(struct tgt_session_info *tsi)
...
        rc = target_bulk_io(exp, desc, &lwi);
        no_reply = rc != 0;
...

6) blocking ast callback timer expires and the server evicts client 1
7) write rpc on client 1 times out, and client 1 finds itself evicted

AT settings managed to make client's rpc timeout bigger than blast callback timeout.