linux-kernel - Re: [PATCH net-next 2/2] tuntap: orphan frags before trying to set tx timestamp

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Date:	Wed, 04 Sep 2013 17:27:01 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Jason Wang <jasowang@...hat.com>
CC:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com,
	Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next 2/2] tuntap: orphan frags before trying to set
 tx timestamp

Hello.

On 04-09-2013 8:33, Jason Wang wrote:

> sock_tx_timestamp() will clear all zerocopy flags of skb which may lead the
> frags never to be orphaned. This will break guest to guest traffic when zerocopy
> is enabled. Fix this by orphaning the frags before trying to set tx time stamp.

> The issue were introduced by commit eda297729171fe16bf34fe5b0419dfb69060f623
> (tun: Support software transmit time stamping).

> Cc: Richard Cochran <richardcochran@...il.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>   drivers/net/tun.c |    9 +++++----
>   1 files changed, 5 insertions(+), 4 deletions(-)

> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 2dddb1b..af9a096 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -749,15 +749,16 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
>   			  >= dev->tx_queue_len / tun->numqueues)
>   		goto drop;
>
> +	/* Orphan the skb - required as we might hang on to it
> +	 * for indefinite time. */

    You could fix the comment style to the networking code default, while at: it:

/* bla
  * bla
  */

> +	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
> +		goto drop;
> +
>   	if (skb->sk) {
>   		sock_tx_timestamp(skb->sk, &skb_shinfo(skb)->tx_flags);
>   		sw_tx_timestamp(skb);
>   	}
>
> -	/* Orphan the skb - required as we might hang on to it
> -	 * for indefinite time. */
> -	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
> -		goto drop;

WBR, Sergei



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