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

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Date:	Wed, 20 Nov 2013 11:06:27 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Michael Dalton <mwdalton@...gle.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Jason Wang <jasowang@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	lf-virt <virtualization@...ts.linux-foundation.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] virtio-net: fix page refcnt leaking when fail to
 allocate frag skb

On Tue, Nov 19, 2013 at 01:38:16PM -0800, Michael Dalton wrote:
> Great catch Jason. I agree this now raises the larger issue of how to
> handle a memory alloc failure in the middle of receive. As Eric mentioned,
> we can drop the packet and free the remaining (num_buf) frags.
> 
> Michael, perhaps I'm missing something, but why would you prefer
> pre-allocating buffers in this case? If the guest kernel is OOM'ing,
> dropping packets should provide backpressure.
> 
> Also, we could just as easily fail the initial skb alloc in page_to_skb,
> and I think that case also needs to be handled now in the same fashion as
> a memory allocation failure in receive_mergeable.
> 
> Best,
> 
> Mike

Yes I missed this last night. Thanks a lot Eric and Michael for pointing
this out.
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