Dell Unity: ls command hung on RHEL 8.4 client when mounting Unity NFS export via NFSv4 (User Correctable)

Summary: ls command hung on RHEL 8.4 client when mounting Unity NFS export via NFSv4.

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Symptoms

ls command hung forever on Linux client. Issue is only observed on RHEL 8.4 client running kernel version earlier than kernel-4.18.0-305.17.1.el8_4. 
 

Cause

The issue is caused by the interaction between the Unity NFS server and the RHEL 8.4 clients running a kernel earlier than kernel-4.18.0-305.17.1.el8_4.  When the NFS server is sending a non-zero verifier in the READDIR Reply, the NFS client continues to send 0 for the cookie verifier in the subsequent READDIR Call.  This results in an endless READDIR loop which causes the ls command to hang forever. 

Resolution

Workaround: 
- Mount the nfs export via NFSv3.

Permanent fix:

- From client side, the misbehavior is fixed in kernel-4.18.0-305.17.1.el8_4.

Details can be found from RHEL release. 
https://access.redhat.com/errata/RHSA-2021:3447

NFS client hangs on share listing when server side readdir verifiers are implemented (BZ#1993895)

A Redhat KB article is also available for this issue. 

https://access.redhat.com/solutions/6189341

Dell Unity Engineering are also investigating future code enhancements to further address this issue. The KB will be updated when there is an update.

Affected Products

Dell EMC Unity, Red Hat Enterprise Linux Version 8
Article Properties
Article Number: 000202521
Article Type: Solution
Last Modified: 27 Jul 2023
Version:  4
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