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Subject: Re: NFS client behavior on WRITE_DELEGATION
From:   Anna Schumaker <schumaker.anna@gmail.com>
To:     Anna Schumaker <schumakeranna@gmail.com>,
        Soumya Koduri <skoduri@redhat.com>
Cc:     linux-nfs@vger.kernel.org, Matt Benjamin <mbenjamin@redhat.com>
Date:   Wed, 05 Dec 2018 15:30:02 -0500
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On Wed, 2018-12-05 at 15:22 -0500, Anna Schumaker wrote:
> Hi Soumya,
> 
> What conditions are you seeing the writes?  It could be the kernel trying to
> flush out data to free up memory for other processes.
> 
> I don't think preemptively writing back data is necessarily a bad thing
> though, even with a write delegation.  If the server decides to recall the
> delegation, we wouldn't keep it waiting as long while we write back local
> data.  Additionally, if the client crashes then any updates might have already
> had a chance to sync to the server.
> 
> I hope this helps!
> Anna
> 
> On Mon, Dec 3, 2018 at 2:55 AM Soumya Koduri <skoduri@redhat.com> wrote:
> > Hi,
> > 
> > In our NFSv4.1 Delegations testing we observed that NFS client sends 
> > WRITE requests to the server even when granted WRITE_DELEGATION. I see 
> > that only OPEN/CLOSE and LOCK operations are served locally by the client.
> > 
> > Please confirm if this behavior is expected and if yes, can it be 
> > improved to avoid sending WRITEs to the server until the application 
> > does fsync.
> > 
> > Thanks,
> > Soumya