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 09EF524EF72; Thu, 17 Apr 2025 13:55:13 +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=1744898114; cv=none; b=OuGzjqdyOx13L8Gly/fh7jBf0mQroAuH28rubCpB+PRNgl1RmUZlVd4E8kY4MSDfsDRowPMsWHYYNZrFJP+xlbMHy9R+fah/2JL1y4UqBoQJhtz0RLtsQ/CiEhPfWK1Mbpd2wvJ1wc+ONoUxWWufMSu7yzgk03vJQ/sGNv8PdG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744898114; c=relaxed/simple; bh=DaXbVItV4vEdJ1PxdCzd1lAzo6REI3kB5/yRt2cUJ1Q=; h=Subject:From:To:Cc:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=nT9uY2mT999W9sjbIjahKVvTEAldvgItDxgs8mCaKdaaRIu7FfnqhA56mO/RZoXJ9XJrViJQm8zQkJcW6tlrs4qkhlIb4Wddho1XGEvkm7nSLn7nziqGuPyCuqw5BY5mGtIy0U7nWIsamazJKZTV29C1cJrYyVWmzAisioIes/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lTrZinNx; 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="lTrZinNx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A5FDC4CEEA; Thu, 17 Apr 2025 13:55:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744898113; bh=DaXbVItV4vEdJ1PxdCzd1lAzo6REI3kB5/yRt2cUJ1Q=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=lTrZinNxVD0pK3FP/9ZXEsvueppmmYKT6Axqz6Was9MxSmrYrK/6X/pUMOPbv2jO0 4A+WSRfX9ZhvZbHLinkWHch6E14ByOmz6KsI/uh8IEPWyGz/wS7/dwcyZFHzf1aMbc RYsfiDXU/K52ECeYWYvbSbRYO5vtzXLXoGxLq7cmWhj/vANDSIBrsLVFTBXTCJUVvx OaBKnY1jANSBoH+Zo3Vxpbb1t0o/ESBfBVv/PRXtYALSTJcCqhIMg0tC1Zn+Df/l2k Is4mcjMkvjyp654UAwb2C0I7WXTuWOwmoCkMeyW//k7w4OisjcolTQ2xhx1Ezk6xkB EaXIOhJglxpmA== Subject: [PATCH net-next V5 1/2] net: sched: generalize check for no-queue qdisc on TX queue From: Jesper Dangaard Brouer To: netdev@vger.kernel.org, Jakub Kicinski Cc: Jesper Dangaard Brouer , bpf@vger.kernel.org, tom@herbertland.com, Eric Dumazet , "David S. Miller" , Paolo Abeni , =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , dsahern@kernel.org, makita.toshiaki@lab.ntt.co.jp, kernel-team@cloudflare.com, phil@nwl.cc Date: Thu, 17 Apr 2025 15:55:09 +0200 Message-ID: <174489810897.355490.12073714761899580608.stgit@firesoul> In-Reply-To: <174489803410.355490.13216831426556849084.stgit@firesoul> References: <174489803410.355490.13216831426556849084.stgit@firesoul> User-Agent: StGit/1.5 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit 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. Reviewed-by: David Ahern Reviewed-by: Toke Høiland-Jørgensen Signed-off-by: Jesper Dangaard Brouer --- drivers/net/vrf.c | 4 +--- include/net/sch_generic.h | 8 ++++++++ 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c index 7168b33adadb..9a4beea6ee0c 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -343,15 +343,13 @@ static int vrf_ifindex_lookup_by_table_id(struct net *net, u32 table_id) static bool qdisc_tx_is_default(const struct net_device *dev) { struct netdev_queue *txq; - struct Qdisc *qdisc; if (dev->num_tx_queues > 1) return false; txq = netdev_get_tx_queue(dev, 0); - qdisc = rcu_access_pointer(txq->qdisc); - return !qdisc->enqueue; + return qdisc_txq_has_no_queue(txq); } /* 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; +} + /* Is the device using the noop qdisc on all queues? */ static inline bool qdisc_tx_is_noop(const struct net_device *dev) {