netdev - Re: [PATCH net] virtio-net: fix page refcnt leaking when fail to allocate frag skb

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Date:	Wed, 20 Nov 2013 11:00:41 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	rusty@...tcorp.com.au, mst@...hat.com,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Michael Dalton <mwdalton@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] virtio-net: fix page refcnt leaking when fail to
 allocate frag skb

On 11/19/2013 10:03 PM, Eric Dumazet wrote:
> On Tue, 2013-11-19 at 16:05 +0800, Jason Wang wrote:
>> > We need to drop the refcnt of page when we fail to allocate an skb for frag
>> > list, otherwise it will be leaked. The bug was introduced by commit
>> > 2613af0ed18a11d5c566a81f9a6510b73180660a ("virtio_net: migrate mergeable rx
>> > buffers to page frag allocators").
>> > 
>> > Cc: Michael Dalton <mwdalton@...gle.com>
>> > Cc: Eric Dumazet <edumazet@...gle.com>
>> > Cc: Rusty Russell <rusty@...tcorp.com.au>
>> > Cc: Michael S. Tsirkin <mst@...hat.com>
>> > Signed-off-by: Jason Wang <jasowang@...hat.com>
>> > ---
>> > The patch was needed for 3.12 stable.
> Good catch, but if we return from receive_mergeable() in the 'middle'
> of the frags we would need for the current skb, who will
> call the virtqueue_get_buf() to flush the remaining frags ?
>
> Don't we also need to call virtqueue_get_buf() like 
>
> while (--num_buf) {
>     buf = virtqueue_get_buf(rq->vq, &len);
>     if (!buf)
>         break;
>     put_page(virt_to_head_page(buf));
> }
>
> ?

Yes we need this, will send V2.

Thanks
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