netdev - Re: [PATCH net-next 04/11] tuntap: simplify error handling in tun_build

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Message-ID: <372ec320-83cf-add5-acf7-27d876c3d604@redhat.com>
Date:   Mon, 10 Sep 2018 11:44:26 +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 04/11] tuntap: simplify error handling in
 tun_build_skb()



On 2018年09月07日 22:17, Michael S. Tsirkin wrote:
> On Fri, Sep 07, 2018 at 11:22:00AM +0800, Jason Wang wrote:
>>>> @@ -1668,6 +1668,9 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
>>>>    	if (copied != len)
>>>>    		return ERR_PTR(-EFAULT);
>>>> +	get_page(alloc_frag->page);
>>>> +	alloc_frag->offset += buflen;
>>>> +
>>> This adds an atomic op on XDP_DROP which is a data path
>>> operation for some workloads.
>> Yes, I have patch on top to amortize this, the idea is to have a very big
>> refcount once after the frag was allocated and maintain a bias and decrease
>> them all when allocating new frags.'
> Why bother with refcounting for a drop though? It should be simple.
>

Right, let me fix this.

Thanks