Re: [net 7/9] net/mlx5e: kTLS, Call WARN_ONCE on netdev mismatch

[Jakub Kicinski <jakub.kicinski@netronome.com>]

On Thu, 25 Jul 2019 20:36:48 +0000, Saeed Mahameed wrote:
> From: Tariq Toukan <tariqt@mellanox.com>
> 
> A netdev mismatch in the processed TLS SKB should not occur,
> and indicates a kernel bug.
> Add WARN_ONCE to spot such cases.
> 
> Fixes: d2ead1f360e8 ("net/mlx5e: Add kTLS TX HW offload support")
> Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
> index ea032f54197e..3766545ce259 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c
> @@ -412,7 +412,7 @@ struct sk_buff *mlx5e_ktls_handle_tx_skb(struct net_device *netdev,
>  		goto out;
>  
>  	tls_ctx = tls_get_ctx(skb->sk);
> -	if (unlikely(tls_ctx->netdev != netdev))
> +	if (unlikely(WARN_ON_ONCE(tls_ctx->netdev != netdev)))

Ah, nit: the unlikely is probably unnecessary but that's no big deal.

#define WARN_ON_ONCE(condition) ({			\
	static int __warned;				\
	int __ret_warn_once = !!(condition);		\
							\
	if (unlikely(__ret_warn_once && !__warned)) {	\
		__warned = true;			\
		WARN_ON(1);				\
	}						\
	unlikely(__ret_warn_once);			\
})

>  		goto err_out;
>  
>  	priv_tx = mlx5e_get_ktls_tx_priv_ctx(tls_ctx);