Re: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit lease renewals

["Schumaker, Anna" <Anna.Schumaker@netapp.com>]

Hi Robert,

On Mon, 2020-01-20 at 17:55 +0000, Robert Milkowski wrote:
> > -----Original Message-----
> > From: Chuck Lever <chuck.lever@oracle.com>
> > Sent: 30 December 2019 15:37
> > To: Robert Milkowski <rmilkowski@gmail.com>
> > Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>; Trond Myklebust
> > <trond.myklebust@hammerspace.com>; Anna Schumaker
> > <anna.schumaker@netapp.com>; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit
> > lease renewals
> > 
> > 
> > 
> > > On Dec 30, 2019, at 10:20 AM, Robert Milkowski <rmilkowski@gmail.com>
> > wrote:
> > > From: Robert Milkowski <rmilkowski@gmail.com>
> > > 
> > > Currently, each time nfs4_do_fsinfo() is called it will do an implicit
> > > NFS4 lease renewal, which is not compliant with the NFS4
> > specification.
> > > This can result in a lease being expired by an NFS server.
> > > 
> > > Commit 83ca7f5ab31f ("NFS: Avoid PUTROOTFH when managing leases")
> > > introduced implicit client lease renewal in nfs4_do_fsinfo(), which
> > > can result in the NFSv4.0 lease to expire on a server side, and
> > > servers returning NFS4ERR_EXPIRED or NFS4ERR_STALE_CLIENTID.
> > > 
> > > This can easily be reproduced by frequently unmounting a sub-mount,
> > > then stat'ing it to get it mounted again, which will delay or even
> > > completely prevent client from sending RENEW operations if no other
> > > NFS operations are issued. Eventually nfs server will expire client's
> > > lease and return an error on file access or next RENEW.
> > > 
> > > This can also happen when a sub-mount is automatically unmounted due
> > > to inactivity (after nfs_mountpoint_expiry_timeout), then it is
> > > mounted again via stat(). This can result in a short window during
> > > which client's lease will expire on a server but not on a client.
> > > This specific case was observed on production systems.
> > > 
> > > This patch makes an explicit lease renewal instead of an implicit one,
> > > by adding RENEW to a compound operation issued by nfs4_do_fsinfo(),
> > > similarly to NFSv4.1 which adds SEQUENCE operation.
> > > 
> > > Fixes: 83ca7f5ab31f ("NFS: Avoid PUTROOTFH when managing leases")
> > > Signed-off-by: Robert Milkowski <rmilkowski@gmail.com>
> > 
> > Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
> > 
> > 
> 
> How do we progress it further?

Thanks for following up! I have the patch included in my linux-next branch for
the next merge window.

Anna

>