netdev - Re: [PATCH net-next] hv_netvsc: fix return type of ndo_start

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Date:   Wed, 26 Sep 2018 12:59:58 +0100
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     <davem@...emloft.net>, <kys@...rosoft.com>,
        <haiyangz@...rosoft.com>, <sthemmin@...rosoft.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org
Subject: Re: [PATCH net-next] hv_netvsc: fix return type of ndo_start_xmit
 function

On Wed, 26 Sep 2018 18:25:10 +0800
YueHaibing <yuehaibing@...wei.com> wrote:

> The method ndo_start_xmit() is defined as returning an 'netdev_tx_t',
> which is a typedef for an enum type, so make sure the implementation in
> this driver has returns 'netdev_tx_t' value, and change the function
> return type to netdev_tx_t.
> 
> As suggestion from Haiyang Zhang <haiyangz@...rosoft.com>, if netvsc_vf_xmit
> fails, We are not sure if the error can go away after retrying, returning
> NETDEV_TX_BUSY may cause infinite retry from the upper layer.
> so just return NETDEV_TX_OK at there.
> 
> Found by coccinelle.
> 
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/net/hyperv/netvsc_drv.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index ec69974..a1d44b4 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -511,7 +511,8 @@ static int netvsc_vf_xmit(struct net_device *net, struct net_device *vf_netdev,
>  	return rc;
>  }
>  
> -static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
> +static netdev_tx_t
> +netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
>  {
>  	struct net_device_context *net_device_ctx = netdev_priv(net);
>  	struct hv_netvsc_packet *packet = NULL;
> @@ -528,8 +529,10 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
>  	 */
>  	vf_netdev = rcu_dereference_bh(net_device_ctx->vf_netdev);
>  	if (vf_netdev && netif_running(vf_netdev) &&
> -	    !netpoll_tx_running(net))
> -		return netvsc_vf_xmit(net, vf_netdev, skb);
> +	    !netpoll_tx_running(net)) {
> +		netvsc_vf_xmit(net, vf_netdev, skb);
> +		return NETDEV_TX_OK;
> +	}
>  
>  	/* We will atmost need two pages to describe the rndis
>  	 * header. We can only transmit MAX_PAGE_BUFFER_COUNT number

Your patch loses the possible return values of netvsc_vf_xmit.
A suggested better fix would be to make netvsc_vf_xmit return netdev_tx_t type.
And this means the return value of dev_queue_xmit needs to be netdev_tx_t.

Please don't merge this as is.