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Tue, 03 Feb 2026 06:40:08 -0800 (PST) Received: from [192.168.88.32] ([150.228.93.21]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e131ce64sm55977770f8f.26.2026.02.03.06.40.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Feb 2026 06:40:08 -0800 (PST) Message-ID: <7d544645-8699-409f-89c0-6fc606113627@redhat.com> Date: Tue, 3 Feb 2026 15:40:03 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v8 0/6] move CAN skb headroom content to skb extensions To: socketcan@hartkopp.net, Marc Kleine-Budde , Vincent Mailhol , Robin van der Gracht , Oleksij Rempel , kernel@pengutronix.de, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Simon Horman Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kernel test robot References: <20260201-can_skb_ext-v8-0-3635d790fe8b@hartkopp.net> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260201-can_skb_ext-v8-0-3635d790fe8b@hartkopp.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/1/26 3:33 PM, Oliver Hartkopp via B4 Relay wrote: > CAN bus related skbuffs (ETH_P_CAN/ETH_P_CANFD/ETH_P_CANXL) simply contain > CAN frame structs for CAN CC/FD/XL of skb->len length at skb->data. Those > CAN skbs do not have network/mac/transport headers nor other such > references for encapsulated protocols like ethernet/IP protocols. > > To store data for CAN specific use-cases all CAN bus related skbuffs are > created with a 16 byte private skb headroom (struct can_skb_priv). Using > the skb headroom and accessing skb->head for this private data led to > several problems in the past likely due to "The struct can_skb_priv > business is highly unconventional for the networking stack." [1] > > This patch set aims to remove the unconventional skb headroom usage for CAN > bus related skbuffs and use the common skb extensions instead. > > [1] https://lore.kernel.org/linux-can/20260104074222.29e660ac@kernel.org/ Could you please share how skb_ext size change with this series? (possibly breaking down the actual size to each separate extension). Ideally/hopefully the skbuff_ext_cache size is not going to change, and that would ensure that this change will not cause any indirect regressions. /P