[LU-16538] Return PR or PW lock mode for OPEN ibits lock for DoM files

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Assignee: WC Triage
• Reporter: Qian Yingjin

Description

In the current Lustre, an OPEN ibits lock returned to a client is mandatorily setting to specific lock mode:
open mode lock mode

• FMODE_WRITE CW
• FMODE_EXEC PR
• other CR

For DoM files, it would better to return the corresponding DOM ibits lock together (combined) with OPEN ibits to a client during the open() or open-ahead(https://jira.whamcloud.com/browse/LU-16429) for the possible subsequent read or write, which can reduce extra lock traffic for DOM ibits lock.

The client needs to handle for PW or PW OPEN ibits lock properly.