From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E3D7946F; Tue, 15 Apr 2025 16:30:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744734644; cv=none; b=vFSXtwcBb+Z+hK38zlonMdOOIaeSYLAYtT85BXcRWzz2NAv7y4zspH1Q/7jY4ji8Dp2QBMOAdfXTh80cDYmhhSIcxV0ErImcAoMpjq57oem5/BvPjI7HQYr1v6iPCmNB/f7s7Rl6A9UNHtDtYvR8guqS1/mC86Q9vH7zWl8UTDU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744734644; c=relaxed/simple; bh=weFLulQd64Nt8wSZqx8JH29VMOiyErt5HVf/jr1Jwis=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Y7bo50L0am4sZipl/gX9cnjzc1pASFsHoax7UKErX41NkMfi5vco83xuvG37WdfJvHbl4NmP9qdgBo5bCT7E4iOsiaTk1gIcjzSv6dRrz5TPoHzJpFZvWPzEs482qNmfE+Y4eOeLptire1hi01toJYm0qJzDrroWdS9Svlrj9Fs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JFN3xWrF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JFN3xWrF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39342C4CEEB; Tue, 15 Apr 2025 16:30:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744734643; bh=weFLulQd64Nt8wSZqx8JH29VMOiyErt5HVf/jr1Jwis=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JFN3xWrFVTdxpPrfi7cXgOlUtYWAdqvI481ubvKvsdOizS7JomWgFGpl2+12Oshwn 5h598+LtreCcO9iIK3DuomULfVKJu0mQzjtedtTcL+n+gD9tduCC/YjA/zA1VTTKFV tI8rsh1xksUtIABS4AhaDhzy1+WX5RscTdXqLPQNlAW5ycK2ImdSP4qrHDhu1GaFzI IAtCM+ZodyWa7+A4/qgSrvSov6DXtZ4vyxjByIBZC+rHO5JAOHSZDHh6e4Fe2AecW1 fxCINsp6qCnQzts3iPpoMzLv9r93UHArtxtXFRp+qB/qdny1l8msQu79Z9A65kZa6A 0k3WKQ3N0p/FQ== Message-ID: Date: Tue, 15 Apr 2025 18:30:38 +0200 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next V4 1/2] net: sched: generalize check for no-queue qdisc on TX queue To: David Ahern , netdev@vger.kernel.org, Jakub Kicinski Cc: bpf@vger.kernel.org, tom@herbertland.com, Eric Dumazet , "David S. Miller" , Paolo Abeni , =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , makita.toshiaki@lab.ntt.co.jp, kernel-team@cloudflare.com, phil@nwl.cc References: <174472463778.274639.12670590457453196991.stgit@firesoul> <174472469906.274639.14909448343817900822.stgit@firesoul> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 15/04/2025 17.43, David Ahern wrote: > On 4/15/25 7:44 AM, Jesper Dangaard Brouer wrote: >> The "noqueue" qdisc can either be directly attached, or get default >> attached if net_device priv_flags has IFF_NO_QUEUE. In both cases, the >> allocated Qdisc structure gets it's enqueue function pointer reset to >> NULL by noqueue_init() via noqueue_qdisc_ops. >> >> This is a common case for software virtual net_devices. For these devices >> with no-queue, the transmission path in __dev_queue_xmit() will bypass >> the qdisc layer. Directly invoking device drivers ndo_start_xmit (via >> dev_hard_start_xmit). In this mode the device driver is not allowed to >> ask for packets to be queued (either via returning NETDEV_TX_BUSY or >> stopping the TXQ). >> >> The simplest and most reliable way to identify this no-queue case is by >> checking if enqueue == NULL. >> >> The vrf driver currently open-codes this check (!qdisc->enqueue). While >> functionally correct, this low-level detail is better encapsulated in a >> dedicated helper for clarity and long-term maintainability. >> >> To make this behavior more explicit and reusable, this patch introduce a >> new helper: qdisc_txq_has_no_queue(). Helper will also be used by the >> veth driver in the next patch, which introduces optional qdisc-based >> backpressure. >> >> This is a non-functional change. >> >> Signed-off-by: Jesper Dangaard Brouer >> --- >> drivers/net/vrf.c | 4 +--- >> include/net/sch_generic.h | 8 ++++++++ >> 2 files changed, 9 insertions(+), 3 deletions(-) >> > > >> /* Local traffic destined to local address. Reinsert the packet to rx >> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h >> index d48c657191cd..b6c177f7141c 100644 >> --- a/include/net/sch_generic.h >> +++ b/include/net/sch_generic.h >> @@ -803,6 +803,14 @@ static inline bool qdisc_tx_changing(const struct net_device *dev) >> return false; >> } >> >> +/* "noqueue" qdisc identified by not having any enqueue, see noqueue_init() */ >> +static inline bool qdisc_txq_has_no_queue(const struct netdev_queue *txq) >> +{ >> + struct Qdisc *qdisc = rcu_access_pointer(txq->qdisc); >> + >> + return qdisc->enqueue == NULL; > > Did checkpatch not complain that this should be '!qdisc->enqueue' ? > Nope: ./scripts/checkpatch.pl patches-veth_pushback_to_qdisc03/01-0001-net-sched-generalize-noop.patch total: 0 errors, 0 warnings, 30 lines checked patches-veth_pushback_to_qdisc03/01-0001-net-sched-generalize-noop.patch has no obvious style problems and is ready for submission. > > Reviewed-by: David Ahern Thx for review :-) --Jesper