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Date:   Mon, 19 Oct 2020 14:14:09 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Guy Keren <guy@vastdata.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: questions about the linux NFS 4.1 client and persistent sessions
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On Sun, Oct 18, 2020 at 02:18:55PM +0300, Guy Keren wrote:
> so suppose that the client sent two 'Open' requests in one compound.
> the server finished processing the first, but then had a delegation on
> the 2nd one, so it is supposed to return an NFS4_OK to the first Open
> and a NFSERR_DELAY for the 2nd open (and this is also the compound
> response that the server will store in its Duplicate Request Cache).
> if the server had a temporary network disconnection, or had a server
> restart, then when the client re-connects and re-sends this compound
> request, it receives the response from the server's Duplicate Request
> Cache (with OK for the first open and DELA?Y For the 2nd). than, i
> presume that the client needs to accept that the first Open already
> succeeded, and when creating a new session, re-send only the 2nd Open
> request. does this make sense?

Sounds right.

> > I don't know of any client that actually does that, for what it's worth.
> > The Linux client, for example, doesn't send any compounds that I can
> > think of that have more than one nonidempotent op.
> 
> does it mean that the linux NFS 4.1 client will also never send two
> Write requests in the same compound? and never send an Open request
> which might create a file, with a Write request in the same compound?

"Will never" might be a little strong--maybe there'll be a reason to do
it some day.  A server should be prepared to handle it.  But the client
doesn't currently do either of those things.

--b.