[LU-6433] MDS deadlock in qouta

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.8.0
• Labels: patch
• Severity: 3
• Assignee: Niu Yawei (Inactive)
• Reporter: Andriy Skulysh

Description

With new quota code MDS obtains quota credits via ptlrpc requests.
All quota operation takes place after obtaining ldlm lock.
So, with single MDS it can happen that we are run out of mdt threads to process quota request while all other mdt threads are waiting for a lock conflicting with a lock taken by a thread which is sending quota request.

The possible solution is to serve quota requests in a HP queue. It looks like quota lock doesn't conflicts, so quota intends can be processed in a HP queue also.

Issue Links

• is related to: LU-7926 MDS sits idle with extreme slow response to clients