[ClusterLabs] NFS mount fails to stop if NFS server is lost

Miro Igov miro.igov at pharmya.com
Tue Apr 18 09:45:54 EDT 2023

Force -f is improper in situations when NFS server is gone.

I have node intranet-test2 with nfs mount and nas-sync-test2 with NFS server and export resources.

I made following experiment:

1.	Paused the VM running nas-sync-test2 so cluster lost the member
2.	Executed umount -f /folder and it displayed error umount.nfs4: /folder: device is busy
3.	Executed umount -f -l /folder and all fine


Reference: https://askubuntu.com/questions/292043/how-to-unmount-nfs-when-server-is-gone


Is it possible to add the lazy -l option to the umount ?


From: Miro Igov <miro.igov at pharmya.com> 
Sent: 11 April 2023 21:47
To: Cluster Labs - All topics related to open-source clustering welcomed <users at clusterlabs.org>
Subject: Re: [ClusterLabs] NFS mount fails to stop if NFS server is lost


What about umount -f -l ?



From: Users <users-bounces at clusterlabs.org <mailto:users-bounces at clusterlabs.org> > on behalf of Andrei Borzenkov <arvidjaar at gmail.com <mailto:arvidjaar at gmail.com> >
Sent: Tuesday, April 11, 2023, 20:26
To: users at clusterlabs.org <mailto:users at clusterlabs.org>  <users at clusterlabs.org <mailto:users at clusterlabs.org> >
Subject: Re: [ClusterLabs] NFS mount fails to stop if NFS server is lost

On 11.04.2023 17:35, Miro Igov wrote:
> Hello,
> I have a node nas-sync-test1 with NFS server and NFS export running and
> another node intranet-test1 with data_1 fs mount:
> primitive data_1 Filesystem \
> params device="nas-sync-test1:/home/pharmya/NAS" fstype=nfs
> options=v4 directory="/data/synology/pharmya_office/NAS_Sync/NAS" \
> op monitor interval=10s
> Disconnecting nas-sync-test1 from the network shows it's state as UNCLEAN
> and pacemaker fences it.
> Then it tries to stop data_1 but it shows timeout error.
> I know unmounting of NFS mount when NFS server is gone requires force. Is
> there such option in Filesystem RA ?

It does it unconditionally from the very beginning

# For networked filesystems, there's merit in trying -f:
case "$FSTYPE" in
nfs4|nfs|efs|cifs|smbfs) umount_force="-f" ;;

But IIRC it is not enough (at least, not always) - so the trick is to 
setup the same IP address as server had. It could be an alias on a local 
client interface, does not matter. I suppose client gets stuck somewhere 
below application layer and having IP resets TCP connection allowing it 
to proceed.

I certainly had to do it in the past, and simple "umount -f" did not work.
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