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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-675b286ecfdsm68306d50.12.2026.09.29.08.00.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2026 08:00:17 -0700 (PDT) Date: Tue, 29 Sep 2026 11:00:16 -0400 From: Willem de Bruijn To: Wang Zhan , netdev@vger.kernel.org, Willem de Bruijn Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, keyong.sun@smartx.com, Wang Zhan , Jason Wang , Andrew Lunn , Aaron Conole , Eelco Chaudron , Ilya Maximets , dev@openvswitch.org, Daniel Borkmann , Neal Cardwell , Kuniyuki Iwashima , Alice Mikityanska , David Laight Message-ID: In-Reply-To: <20260929102517.2005181-1-wang.zhan@smartx.com> References: <20260928044102.1004310-1-wang.zhan@smartx.com> <20260928044102.1004310-5-wang.zhan@smartx.com> <20260929102517.2005181-1-wang.zhan@smartx.com> Subject: Re: [PATCH net-next v3 4/5] net: core: resegment oversized TCP GSO skbs 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: 7bit Wang Zhan wrote: > On Mon, 28 Sep 2026 19:47:43 -0400 Willem de Bruijn wrote: > > > + /* > > > + * The TCP frag-list path segments through skb_segment_list(), which > > > + * does not carry max_segs, so bounded calls skip those skbs. > > > + */ > > > > This comment answers only one of six conditions. And one that is > > pretty straightforward. I'd drop. > > > > In general, drop all too-obvious comments. AI has a habit of adding > > a lot more, and more low information, comments than is customary in > > kernel code (where we also have commit messages). Generally, repeating > > what the code does is of little value. > > Dropped in v4. I will check all the comments in the series. > > > > + if (!skb_is_gso(skb) || !skb_is_gso_tcp(skb) || > > > + skb->encapsulation || skb_has_frag_list(skb) || > > > + !skb_mac_header_was_set(skb) || > > > + !skb_transport_header_was_set(skb)) > > > > Conversely, they last two conditions are less obvious. Are they not > > always true for a TSO packet? > > The transport header can be missing. qdisc_pkt_len_segs_init() does the > same check on this path (net/core/dev.c:4245, a0dce8752193e). > > The mac header is always set. It can be dropped in v4. > > > > + gso_max_size = netif_get_gso_max_size(dev, vlan_get_protocol(skb)); > > > > Third time this is now called in validate_xmit_skb. Not sure if that can > > easily be avoided. > > Maybe we can pass the oversize and gso_max_size flags out of > __netif_skb_features, but it would be a bit ugly. I think the current > cost is acceptable. Agreed. I was hoping otherwise, but don't see an easy fix (and didn't explore more deeply to be fair).