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ClearCase dynamic view storage on BTRFS does not work correctly

Troubleshooting


Problem

On SUSE Linux Enterprise Server 12 after Service Pack 2 inclusive (SLES12 SP2+), and SUSE Linux Enterprise Server 15, if you create a dynamic MVFS view and set the view storage directory to a BTRFS file system with the snapshot feature active, then some operations like 'cleartool deliver' might enter into an uninterruptible state (or hang).

Symptom

Some processes running on the system cannot be killed with 'kill' or interrupted with Ctrl+C.

Cause

The uninterruptible state is caused by a problem with the interaction between MVFS and BTRFS.

Environment

SLES12 since SP2, and SLES15 with BTRFS and snapshots feature active.

Diagnosing The Problem

You find that a process cannot be interrupted. Check if it is in D state (an uninterruptible state) by using the following command:
$ ps -aux

The affected process will have a D in the STAT column.

Confirm that the dynamic view storage is local on a BTRFS file system mount. You need to know the dynamic view name. To find the path to the view storage directory, use the following commands:
$ ct lsview -l | grep 'access path' | cut -d ':' -f 2
/var/tmp/myview.vws


When you know the path to the view storage directory, use it to find the file system type with the following commands:
$ stat -f /var/tmp/myview.vws | grep Type
ID: 9ad5d09f86c3e90e Namelen: 255     Type: btrfs


If the 'Type' field is 'btrfs', then the view storage is on BTRFS and it is the probable cause of the process being in an uninterruptible state.

Resolving The Problem

Set the dynamic view storage to a different file system.

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Document Information

Modified date:
10 June 2020

UID

swg22004584