[LU-17177] prevent DoM read-on-open with FLR

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: Mikhail Pershin
• Reporter: Mikhail Pershin

Description

DoM read-on-open feature fetch some data from MDT stripe during file open. Meanwhile that is happening always when it sees data on MDT without regards to actual mirror states. That can cause at least useless reads from non-active mirror, at worse stale data read.

Considering that the following changes are proposed:

• no read-on-open data prefetch for FLR file
• no DoM lock/size returned if DoM component has stale FLR flag

thus we avoid potential problems and doesn't lose significant benefits, in most cases mirrored file is not having any real performance gain from read-on-open.

Issue Links

• is related to: LU-16468 some miscellaneous IOs need to protect accessing layout