Umount fails on NFSv4 formerly exported file system until another file system is unexported
This document (000020609) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Server 15 Service Pack 3
If the second file system is unexported and then the NFS lease time (usually 90 seconds) is allowed to expire, the first file system can finally be umounted. Alternatively, if the nfsserver service is stopped, the file system can be immediately umounted. However, it may be preferred for the first file system to be umounted without affecting the second file system's export status.
SLES15 SP3 kernel-default-5.3.18-150300.59.54.1
With the updated (or newer) kernel in place, use this sequence:
1. Unexport the file system in question. (See "man exportfs")
2. Signal the NFS Server to unlock the file system with this command:
echo /path/to/filesystem > /proc/fs/nfsd/unlock_filesystem
Where "/path/to/filesystem" is replaced with the actual path to the file system which had been exported. The proc location specified above is literal.
3. Unmount (umount) the file system.
This issue was first brought to SUSE's attention by a customer whose Linux NFS Server was operating in a cluster. Different NFS-exported file systems were being managed and moved around the cluster independently from each other. While this is a fairly common practice and will sometimes work without any perceptible problem, it doesn't correctly support 100% of NFS 4.x functionality. Specifically, it doesn't support client lock retention during NFS Server failover. For a discussion of NFS 4 cluster design which can support all functionality, see https://www.suse.com/support/kb/doc/?id=000020396
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- Document ID:000020609
- Creation Date: 09-Mar-2022
- Modified Date:09-Mar-2022
- SUSE Linux Enterprise Server
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