linux-kernel - RE: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit lease renewals

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Date:   Mon, 20 Jan 2020 17:55:00 -0000
From:   "Robert Milkowski" <rmilkowski@...il.com>
To:     "'Chuck Lever'" <chuck.lever@...cle.com>,
        "'Trond Myklebust'" <trondmy@...merspace.com>
Cc:     "'Linux NFS Mailing List'" <linux-nfs@...r.kernel.org>,
        "'Trond Myklebust'" <trond.myklebust@...merspace.com>,
        "'Anna Schumaker'" <anna.schumaker@...app.com>,
        <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit lease renewals



> -----Original Message-----
> From: Chuck Lever <chuck.lever@...cle.com>
> Sent: 30 December 2019 15:37
> To: Robert Milkowski <rmilkowski@...il.com>
> Cc: Linux NFS Mailing List <linux-nfs@...r.kernel.org>; Trond Myklebust
> <trond.myklebust@...merspace.com>; Anna Schumaker
> <anna.schumaker@...app.com>; linux-kernel@...r.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@...il.com>
> wrote:
> >
> > From: Robert Milkowski <rmilkowski@...il.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@...il.com>
> 
> Reviewed-by: Chuck Lever <chuck.lever@...cle.com>
> 
> 

How do we progress it further?

-- 
Robert Milkowski