From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net-next v2 1/2] udp: msg_zerocopy
Date: Mon, 26 Nov 2018 19:04:09 +0100
Message-ID: <ae1b8e52272b14a49ff4225e647c86c0aab57980.camel@redhat.com>
References: <20181126152939.258443-1-willemdebruijn.kernel@gmail.com>
         <20181126152939.258443-2-willemdebruijn.kernel@gmail.com>
         <11350ff03fc6b03e34f8b4acd063371c887758d8.camel@redhat.com>
         <CAF=yD-J-QP_zUFY9W7CMdjOPgAwkHGgSfVQfVb=EKTNOZB4P8Q@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Cc: Network Development <netdev@vger.kernel.org>,
        David Miller <davem@davemloft.net>,
        Willem de Bruijn <willemb@google.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:50610 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1726202AbeK0E7E (ORCPT <rfc822;netdev@vger.kernel.org>);
        Mon, 26 Nov 2018 23:59:04 -0500
In-Reply-To: <CAF=yD-J-QP_zUFY9W7CMdjOPgAwkHGgSfVQfVb=EKTNOZB4P8Q@mail.gmail.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Mon, 2018-11-26 at 12:59 -0500, Willem de Bruijn wrote:
> The callers of this function do flush the queue of the other skbs on
> error, but only after the call to sock_zerocopy_put_abort.
> 
> sock_zerocopy_put_abort depends on total rollback to revert the
> sk_zckey increment and suppress the completion notification (which
> must not happen on return with error).
> 
> I don't immediately have a fix. Need to think about this some more..

[still out of sheer ignorance] How about tacking a refcnt for the whole
ip_append_data() scope, like in the tcp case? that will add an atomic
op per loop (likely, hitting the cache) but will remove some code hunk
in sock_zerocopy_put_abort() and sock_zerocopy_alloc().

Cheer,

Paolo