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 2208A352FCE; Tue, 26 Aug 2025 14:27:01 +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=1756218421; cv=none; b=ttKAwlXR2TDSTAQ2M4huj9ECNI94wfjvk2GUGJ8XHqtrud5EO7XGAEfHcAR8TSuvi38nV42cJPa/Gn6HXAkAbwuvGr5T8iMaxw+XbOhDTnQwk8aB1mE5T836QR3u2TAU09nJuquOjBcrn8CR+1z01dL0yxatQq305qAmey3R3OY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756218421; c=relaxed/simple; bh=3X4vPCTI+qfVjzHHzKs5LsSuS40kgG3xTxnIE+Dw2gQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=H+fpQh+2+SVbI18U3AY7/vPy0PinHsAll0AU6wwC3PYZSGoAQ++fg0+eCcSQjOCLJ884FNkbCefgyisH+8XXiIohlvVrpz/tKi3g0/KtFY3NtP8xxHNBtVK1V5XIXjVEdqY/PtryBK0gY+ZiId3QQ+op0HrZJYNbxeEi1FMRaKI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xfeXVXWv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xfeXVXWv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A73D6C4CEF1; Tue, 26 Aug 2025 14:27:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756218421; bh=3X4vPCTI+qfVjzHHzKs5LsSuS40kgG3xTxnIE+Dw2gQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xfeXVXWvzMJH8pe6BdmFyb1sBN5S+uqwJDy8akLM1Jy7R+91lpytbz4x0goIx3lEX 6AvEAo327YhhXMx+MH+uYEk2sIeiKBFT9v7udgO75gOjy4dJ6B8/HuGTBZrTMn/Rma xJ/8xb4oDK05dEPZQ9Px07zsq3miWk4F2087wn3c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, William Liu , Savino Dicanosa , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Jamal Hadi Salim , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 516/523] net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit Date: Tue, 26 Aug 2025 13:12:06 +0200 Message-ID: <20250826110937.167468548@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110924.562212281@linuxfoundation.org> References: <20250826110924.562212281@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: William Liu [ Upstream commit 15de71d06a400f7fdc15bf377a2552b0ec437cf5 ] The following setup can trigger a WARNING in htb_activate due to the condition: !cl->leaf.q->q.qlen tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 \ htb rate 64bit tc qdisc add dev lo parent 1:1 handle f: \ cake memlimit 1b ping -I lo -f -c1 -s64 -W0.001 127.0.0.1 This is because the low memlimit leads to a low buffer_limit, which causes packet dropping. However, cake_enqueue still returns NET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an empty child qdisc. We should return NET_XMIT_CN when packets are dropped from the same tin and flow. I do not believe return value of NET_XMIT_CN is necessary for packet drops in the case of ack filtering, as that is meant to optimize performance, not to signal congestion. Fixes: 046f6fd5daef ("sched: Add Common Applications Kept Enhanced (cake) qdisc") Signed-off-by: William Liu Reviewed-by: Savino Dicanosa Acked-by: Toke Høiland-Jørgensen Reviewed-by: Jamal Hadi Salim Link: https://patch.msgid.link/20250819033601.579821-1-will@willsroot.io Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_cake.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c index d9535129f4e9..6dabe5eaa3be 100644 --- a/net/sched/sch_cake.c +++ b/net/sched/sch_cake.c @@ -1761,7 +1761,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch, ktime_t now = ktime_get(); struct cake_tin_data *b; struct cake_flow *flow; - u32 idx; + u32 idx, tin; /* choose flow to insert into */ idx = cake_classify(sch, &b, skb, q->flow_mode, &ret); @@ -1771,6 +1771,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch, __qdisc_drop(skb, to_free); return ret; } + tin = (u32)(b - q->tins); idx--; flow = &b->flows[idx]; @@ -1938,13 +1939,22 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch, q->buffer_max_used = q->buffer_used; if (q->buffer_used > q->buffer_limit) { + bool same_flow = false; u32 dropped = 0; + u32 drop_id; while (q->buffer_used > q->buffer_limit) { dropped++; - cake_drop(sch, to_free); + drop_id = cake_drop(sch, to_free); + + if ((drop_id >> 16) == tin && + (drop_id & 0xFFFF) == idx) + same_flow = true; } b->drop_overlimit += dropped; + + if (same_flow) + return NET_XMIT_CN; } return NET_XMIT_SUCCESS; } -- 2.50.1