linux-kernel - Re: [PATCH net-next 1/2] openvswitch: Fix double reporting of drops in dropwatch

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Date:   Fri, 29 Jul 2022 20:31:51 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Mike Pattrick <mkp@...hat.com>
Cc:     netdev@...r.kernel.org, pvalerio@...hat.com,
        Pravin B Shelar <pshelar@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] openvswitch: Fix double reporting of drops
 in dropwatch

On Thu, 28 Jul 2022 12:12:58 -0400 Mike Pattrick wrote:
> Frames sent to userspace can be reported as dropped in
> ovs_dp_process_packet, however, if they are dropped in the netlink code
> then netlink_attachskb will report the same frame as dropped.
> 
> This patch checks for error codes which indicate that the frame has
> already been freed.
> 
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2109946

Please remove the Bugzilla link, it doesn't seem to be public.
If it is then it should be a Link: tag, not a custom tag for bz.

> Signed-off-by: Mike Pattrick <mkp@...hat.com>
> ---
>  net/openvswitch/datapath.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 7e8a39a35627..029f9c3e1c28 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -252,10 +252,20 @@ void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)
>  
>  		upcall.mru = OVS_CB(skb)->mru;
>  		error = ovs_dp_upcall(dp, skb, key, &upcall, 0);
> -		if (unlikely(error))
> -			kfree_skb(skb);
> -		else
> +		switch (error) {
> +		case 0:
> +			fallthrough;
> +		case -EAGAIN:
> +			fallthrough;
> +		case -ERESTARTSYS:
> +			fallthrough;

No need to add the fallthrough;s between two case statements.

> +		case -EINTR:
>  			consume_skb(skb);
> +			break;
> +		default:
> +			kfree_skb(skb);
> +			break;
> +		}
>  		stats_counter = &stats->n_missed;
>  		goto out;
>  	}