linux-kernel - Re: [PATCH net-next 05/11] tuntap: tweak on the path of non-xdp case in tun_build

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Message-ID: <8a5b5db7-ce53-7dc5-7410-0b6d51b5bf10@redhat.com>
Date:   Fri, 7 Sep 2018 11:24:02 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 05/11] tuntap: tweak on the path of non-xdp case
 in tun_build_skb()



On 2018年09月07日 01:16, Michael S. Tsirkin wrote:
> On Thu, Sep 06, 2018 at 12:05:20PM +0800, Jason Wang wrote:
>> If we're sure not to go native XDP, there's no need for several things
>> like bh and rcu stuffs.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> True...
>
>> ---
>>   drivers/net/tun.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index f8cdcfa392c3..389aa0727cc6 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -1675,10 +1675,12 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>>   	 * of xdp_prog above, this should be rare and for simplicity
>>   	 * we do XDP on skb in case the headroom is not enough.
>>   	 */
>> -	if (hdr->gso_type || !xdp_prog)
>> +	if (hdr->gso_type || !xdp_prog) {
>>   		*skb_xdp = 1;
>> -	else
>> -		*skb_xdp = 0;
>> +		goto build;
>> +	}
>> +
>> +	*skb_xdp = 0;
>>   
>>   	local_bh_disable();
>>   	rcu_read_lock();
>> @@ -1724,6 +1726,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>>   	rcu_read_unlock();
>>   	local_bh_enable();
>>   
>> +build:
> But this is spaghetti code. Please just put common
> code into functions and call them, don't goto.

Ok, will do this.

Thanks

>
>>   	skb = build_skb(buf, buflen);
>>   	if (!skb) {
>>   		skb = ERR_PTR(-ENOMEM);
>> -- 
>> 2.17.1