Re: [PATCH net-next 3/6] net/mlx5e: Properly access RCU protected qdisc_sleeping variable

[Michal Swiatkowski <michal.swiatkowski@linux.intel.com>]

On Mon, Jul 14, 2025 at 08:39:42AM +0300, Tariq Toukan wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> qdisc_sleeping variable is declared as "struct Qdisc __rcu" and
> as such needs proper annotation while accessing it.
> 
> Without rtnl_dereference(), the following error is generated by sparse:
> 
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40: warning:
>   incorrect type in initializer (different address spaces)
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    expected
>   struct Qdisc *qdisc
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    got struct
>   Qdisc [noderef] __rcu *qdisc_sleeping
> 
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en/qos.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> index f0744a45db92..4e461cb03b83 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> @@ -374,7 +374,7 @@ void mlx5e_reactivate_qos_sq(struct mlx5e_priv *priv, u16 qid, struct netdev_que
>  void mlx5e_reset_qdisc(struct net_device *dev, u16 qid)
>  {
>  	struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, qid);
> -	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
> +	struct Qdisc *qdisc = rtnl_dereference(dev_queue->qdisc_sleeping);
>  
>  	if (!qdisc)
>  		return;

Good catch, other acesses to the qdisc_sleeping are fine.

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>

> -- 
> 2.40.1