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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Florian Fainelli , Jonas Gorski , Hauke Mehrtens , Kurt Kanzenbach , Woojung Huh , UNGLinuxDriver@microchip.com, "Chester A. Unal" , Daniel Golle , Matthias Brugger , AngeloGioacchino Del Regno , Wei Fang , Clark Wang , =?utf-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= , George McCollister , David Yang , netdev@vger.kernel.org, Sashiko AI Review Subject: Re: [PATCH net-next v2] net: dsa: Fix skb ownership in taggers Message-ID: <20260617130304.w6pwxlrptnn4dflz@skbuf> References: <20260616-dsa-fix-free-skb-v2-1-9dbda6a19e97@kernel.org> <20260616213728.xhja2net2vbjmgzb@skbuf> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Jun 17, 2026 at 02:23:40PM +0200, Linus Walleij wrote: > > - Has anyone proven that a real problem exists? Because dsa_user_xmit() > > -> skb_ensure_writable_head_tail() has run successfully at this stage, > > so we know that dev->needed_headroom bytes are available for writing. > > Because DSA uses VLAN as a tag, dsa_user_setup_tagger() will increase > > dev->needed_headroom by VLAN_HLEN for the tag_8021q protocols, so > > vlan_insert_tag() should not fail. I've looked at this function at it > > seems not to be coded up to fail for any other reason. > > I guess what you're saying is that vlan_insert_tag() will never fail in > ->xmit()? Yes, I may be wrong, but this is what I think. The central idea of the generic TX reallocation series (https://lore.kernel.org/netdev/20201030014910.2738809-1-vladimir.oltean@nxp.com/) was to simplify taggers by moving the failure point in case of reallocation somewhere else. I'm just saying I don't see a strong reason to complicate the tagger responsibility again.