netdev - Re: [PATCH v3 3/8] net/handshake: Ensure the request is destructed on completion

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Message-ID: <CAKmqyKMRXKJTQciiqjPXYAFa6UUJ6xkTSdEfU+9HnyNTOx-BxA@mail.gmail.com>
Date: Tue, 7 Oct 2025 11:22:29 +1000
From: Alistair Francis <alistair23@...il.com>
To: Hannes Reinecke <hare@...e.de>
Cc: chuck.lever@...cle.com, hare@...nel.org, 
	kernel-tls-handshake@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-nvme@...ts.infradead.org, linux-nfs@...r.kernel.org, kbusch@...nel.org, 
	axboe@...nel.dk, hch@....de, sagi@...mberg.me, kch@...dia.com, 
	Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v3 3/8] net/handshake: Ensure the request is destructed on completion

On Mon, Oct 6, 2025 at 4:16 PM Hannes Reinecke <hare@...e.de> wrote:
>
> On 10/3/25 06:31, alistair23@...il.com wrote:
> > From: Alistair Francis <alistair.francis@....com>
> >
> > To avoid future handshake_req_hash_add() calls failing with EEXIST when
> > performing a KeyUpdate let's make sure the old request is destructed
> > as part of the completion.
> >
> > Signed-off-by: Alistair Francis <alistair.francis@....com>
> > ---
> > v3:
> >   - New patch
> >
> >   net/handshake/request.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/net/handshake/request.c b/net/handshake/request.c
> > index 0d1c91c80478..194725a8aaca 100644
> > --- a/net/handshake/request.c
> > +++ b/net/handshake/request.c
> > @@ -311,6 +311,8 @@ void handshake_complete(struct handshake_req *req, unsigned int status,
> >               /* Handshake request is no longer pending */
> >               sock_put(sk);
> >       }
> > +
> > +     handshake_sk_destruct_req(sk);
> >   }
> >   EXPORT_SYMBOL_IF_KUNIT(handshake_complete);
> >
> Curious.
> Why do we need it now? We had been happily using the handshake mechanism
> for quite some time now, so who had been destroying the request without
> this patch?

Until now a handshake would only be destroyed on a failure or when a
sock is freed (via the sk_destruct function pointer).
handshake_complete() is only called on errors, not a successful
handshake so it doesn't remove the request.

Note that destroying is mostly just removing the entry from the hash
table with rhashtable_remove_fast(). Which is what we need to be able
to submit it again.

Alistair

>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                  Kernel Storage Architect
> hare@...e.de                                +49 911 74053 688
> SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
> HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich