Issue/Introduction

This article describes how to troubleshoot an expanded volume that becomes unusable after a snapshot is created and reverted. It applies to the initial diagnosis and resolution of similar issues in ZStack Cloud.

Environment

• Product: ZCF
• Component: Cloud
• Version: 3.x-5.5.30

Symptoms

1. A VM instance uses Kylin V10 SP3 2403. A data volume is attached, formatted as ext4, and mounted at the corresponding mount point.
2. Data is written to the data volume.
3. The data volume is expanded.
4. A snapshot is created for the data volume.
5. The VM instance is stopped and the volume snapshot is reverted. After the revert completes, the VM instance is started and the volume is mounted again in the operating system, but the following error occurs: mount: $MOUNT_POINT: cannot mount; probably corrupted filesystem on $DEVICE

Possible causes

An operating system kernel earlier than 4.19.90-89.19.v2401.ky10 introduces this bug. Version 89.19.v2401.ky10 itself is not affected.

Resolution

1. Restore the affected volume to normal operation.

If expanding the data volume, creating a snapshot, and reverting the snapshot has made the volume unusable, run the following commands so that it can be mounted and used normally:

  [root@localhost~]# debugfs -w $DEVICE
  --------------------------
  debugfs: set_super_value checksum 0x0
  debugfs: quit

2. Upgrade the VM instance kernel to version 89.19 or later to prevent the issue during subsequent volume expansion and snapshot reverts.