netdev - Re: [PATCH net] virtio_net: fix missing dma unmap for resize

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Date: Thu, 09 Nov 2023 12:26:16 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
  "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net] virtio_net: fix missing dma unmap for resize

On Mon, 2023-11-06 at 16:18 +0800, Xuan Zhuo wrote:
> For rq, we have three cases getting buffers from virtio core:
> 
> 1. virtqueue_get_buf{,_ctx}
> 2. virtqueue_detach_unused_buf
> 3. callback for virtqueue_resize
> 
> But in commit 295525e29a5b("virtio_net: merge dma operations when
> filling mergeable buffers"), I missed the dma unmap for the #3 case.
> 
> That will leak some memory, because I did not release the pages referred
> by the unused buffers.
> 
> If we do such script, we will make the system OOM.
> 
>     while true
>     do
>             ethtool -G ens4 rx 128
>             ethtool -G ens4 rx 256
>             free -m
>     done
> 
> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

@Micheal, @Jason: this fix LGTM, but I guess it deserve an explicit ack
from you before merging, thanks!

Paolo