[PATCH net v3] net: thunderx: avoid direct MTU assignment after WRITE_ONCE()
Jacob Keller
jacob.e.keller at intel.com
Wed Jul 9 15:35:25 PDT 2025
On 7/6/2025 12:43 PM, Alok Tiwari wrote:
> The current logic in nicvf_change_mtu() writes the new MTU to
> netdev->mtu using WRITE_ONCE() before verifying if the hardware
> update succeeds. However on hardware update failure, it attempts
> to revert to the original MTU using a direct assignment
> (netdev->mtu = orig_mtu)
> which violates the intended of WRITE_ONCE protection introduced in
> commit 1eb2cded45b3 ("net: annotate writes on dev->mtu from
> ndo_change_mtu()")
>
> Additionally, WRITE_ONCE(netdev->mtu, new_mtu) is unnecessarily
> performed even when the device is not running.
>
> Fix this by:
> Only writing netdev->mtu after successfully updating the hardware.
> Skipping hardware update when the device is down, and setting MTU
> directly. Remove unused variable orig_mtu.
>
> This ensures that all writes to netdev->mtu are consistent with
> WRITE_ONCE expectations and avoids unintended state corruption
> on failure paths.
>
> Signed-off-by: Alok Tiwari <alok.a.tiwari at oracle.com>
> ---
Reviewed-by: Jacob Keller <jacob.e.keller at intel.com>
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