net/mlx5e: Properly access RCU protected qdisc_sleeping variable

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 <[email protected]>
Signed-off-by: Tariq Toukan <[email protected]>
Reviewed-by: Michal Swiatkowski <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: rleon

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;