[LU-7693] umount hang on MDS

• Type: Bug
• Resolution: Cannot Reproduce
• Priority: Critical
• Labels: lola
• Environment: lola; build: https://build.hpdd.intel.com/job/lustre-reviews/36922/
• Severity: 3
• Assignee: WC Triage
• Reporter: Frank Heckes (Inactive)

Description

Error happen during soak testing of build '20160119' (https://wiki.hpdd.intel.com/display/Releases/Soak+Testing+on+Lola#SoakTestingonLola-20160119). build is based on master branch. DNE is enabled. MDTs had been formatted using ldiskfs, OSTs using zfs as backend.
Environment description: https://wiki.hpdd.intel.com/display/Releases/Soak+Testing+on+Lola#SoakTestingonLola-Configuration

The incident occurred during a normal 'umount' - process of the Lustre FS.
Sequence of events:

• Clients successful unmounted
• All server node successful unmounted besides MDTs (mdt-6,7) on lola-11
• umount is stalled on lola-11

Forced stack trace of processe on lola-11, created kernel debug log, and attached messages, console, and debug log to ticket.