nfs remounting regression in v6.5-rc1

nfs remounting regression in v6.5-rc1

[Jeff Layton]

I've hit a regression that crept in sometime after v6.5-rc1. If I have 2
NFS mounts on a client that are mounting 2 directories of the same
export, and then I remount one of them ro, the other will also flip to
being ro as well. For instance:

[vagrant@kdevops-nfs-default ~]$ sudo mount kdevops-nfsd:/export/fstests/kdevops-nfs-default/test /media/test
[vagrant@kdevops-nfs-default ~]$ sudo mount kdevops-nfsd:/export/fstests/kdevops-nfs-default/scratch /media/scratch
[vagrant@kdevops-nfs-default ~]$ mount -v | grep nfs
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)
kdevops-nfsd:/export/fstests/kdevops-nfs-default/test on /media/test type nfs4 (rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.122.79,local_lock=none,addr=192.168.122.138)
kdevops-nfsd:/export/fstests/kdevops-nfs-default/scratch on /media/scratch type nfs4 (rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.122.79,local_lock=none,addr=192.168.122.138)
[vagrant@kdevops-nfs-default ~]$ sudo mount kdevops-nfsd:/export/fstests/kdevops-nfs-default/scratch /media/scratch -o remount,ro
[vagrant@kdevops-nfs-default ~]$ mount -v | grep nfs
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)
kdevops-nfsd:/export/fstests/kdevops-nfs-default/test on /media/test type nfs4 (ro,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.122.79,local_lock=none,addr=192.168.122.138)
kdevops-nfsd:/export/fstests/kdevops-nfs-default/scratch on /media/scratch type nfs4 (ro,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.122.79,local_lock=none,addr=192.168.122.138)

 
In v6.4, /media/test stays rw. Mounting with -o nosharecache works
around the problem (since that disables superblock sharing). This also
manifests as a failure in fstest generic/306.

I'm running a bisect now to try and track down the problem, but if
anyone has thoughts on the cause, let me know.

Cheers,
-- 
Jeff Layton <jlayton@kernel.org>