[LU-4405] stat degradation (interoperability bug after landing a LU-3240)

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.2
• Affects Version/s: Lustre 2.4.1, Lustre 2.5.0
• Labels: mn4 patch
• Environment: any client with http://review.whamcloud.com/#/c/6460/8/ patch landed.
• Severity: 3
• Assignee: Cliff White (Inactive)
• Reporter: Alexey Lyashkov

Description

Cray reported an stat performance degradation in master with older servers (pre < 2.4).

it's easy replicated with statmany tool, as now it's have only ~600 stats per second for same files.

after bisect search by Cray

Patrick Farrell: http://review.whamcloud.com/#/c/6460/8/lustre/mdc/mdc_locks.c
Patrick Farrell: That's the patch that my bisection suggests is the problem

after looking to logs - i see more getattr rpc's as should be in such situation.
so root cause of additional RPC's - patch tries to match PERM bit in lock for servers don't supported such feature, after disabling it - stat rate is restored.

Issue Links

• is related to: LU-3240 The link count is not updated after the mkdir