linux-kernel - Re: [PATCH 2/2] nfsd: allow for more callback session slots

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Message-ID: <66fb4420-a773-4da3-aa0b-7a78d9e50c5d@talpey.com>
Date: Tue, 29 Oct 2024 13:54:16 -0400
From: Tom Talpey <tom@...pey.com>
To: Jeff Layton <jlayton@...nel.org>, Chuck Lever <chuck.lever@...cle.com>
Cc: Neil Brown <neilb@...e.de>, Dai Ngo <Dai.Ngo@...cle.com>,
 Olga Kornievskaia <okorniev@...hat.com>, linux-nfs@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] nfsd: allow for more callback session slots

On 10/29/2024 6:28 AM, Jeff Layton wrote:
> I'm open to switching to a per-session lock of some sort, but I don't
> see a real need here. Only one session will be used as the backchannel
> at a time, so there shouldn't be competing access between different
> sessions for the cl_lock. We are competing with the other uses of the
> cl_lock, but this one should be pretty quick. My preference would be to
> add extra locking only once it becomes clear that it's necessary.
I have a question on what you mean by "Only one session will be used
as the backchannel". Does this mean that the server ignores backchannels
for all but one random victim? That doesn't seem fair, or efficient.
And what happens with nconnect > 1?

Another question is, what clients are offering this many backchannel
slots?

Tom.