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Message-ID: <1703581167.535505-1-xuanzhuo@linux.alibaba.com>
Date: Tue, 26 Dec 2023 16:59:27 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org,
 Jason Wang <jasowang@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v1] virtio_net: fix missing dma unmap for resize

On Tue, 26 Dec 2023 03:57:27 -0500, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Tue, Dec 26, 2023 at 01:57:09PM +0800, Xuan Zhuo wrote:
> > On Tue, 12 Dec 2023 03:26:41 -0500, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > > On Tue, Dec 12, 2023 at 04:11:41PM +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>
> > > > ---
> > > >
> > > > v1: rename to virtnet_rq_free_buf_check_dma()
> > >
> > > The fact that we check does not matter what matters is
> > > that we unmap. I'd change the name to reflect that.
> >
> >
> > Hi Michael:
> >
> > I see one "[GIT PULL] virtio: bugfixes". But this is not in the list.
> >
> > So I hope this is your list.
> >
> > Thanks.
>
> No - I'm still waiting for the comment to be addressed. sorry about
> the back and forth. It does unmap then free. So maybe virtnet_rq_unmap_free_buf?

OK.

I will post v2 soon.

Thanks.



>
>
> >
> > >
> > >
> > > >
> > > >  drivers/net/virtio_net.c | 60 ++++++++++++++++++++--------------------
> > > >  1 file changed, 30 insertions(+), 30 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index d16f592c2061..58ebbffeb952 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -334,7 +334,6 @@ struct virtio_net_common_hdr {
> > > >  	};
> > > >  };
> > > >
> > > > -static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > >  static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > >
> > > >  static bool is_xdp_frame(void *ptr)
> > > > @@ -408,6 +407,17 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
> > > >  	return p;
> > > >  }
> > > >
> > > > +static void virtnet_rq_free_buf(struct virtnet_info *vi,
> > > > +				struct receive_queue *rq, void *buf)
> > > > +{
> > > > +	if (vi->mergeable_rx_bufs)
> > > > +		put_page(virt_to_head_page(buf));
> > > > +	else if (vi->big_packets)
> > > > +		give_pages(rq, buf);
> > > > +	else
> > > > +		put_page(virt_to_head_page(buf));
> > > > +}
> > > > +
> > > >  static void enable_delayed_refill(struct virtnet_info *vi)
> > > >  {
> > > >  	spin_lock_bh(&vi->refill_lock);
> > > > @@ -634,17 +644,6 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
> > > >  	return buf;
> > > >  }
> > > >
> > > > -static void *virtnet_rq_detach_unused_buf(struct receive_queue *rq)
> > > > -{
> > > > -	void *buf;
> > > > -
> > > > -	buf = virtqueue_detach_unused_buf(rq->vq);
> > > > -	if (buf && rq->do_dma)
> > > > -		virtnet_rq_unmap(rq, buf, 0);
> > > > -
> > > > -	return buf;
> > > > -}
> > > > -
> > > >  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
> > > >  {
> > > >  	struct virtnet_rq_dma *dma;
> > > > @@ -744,6 +743,20 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > > >  	}
> > > >  }
> > > >
> > > > +static void virtnet_rq_free_buf_check_dma(struct virtqueue *vq, void *buf)
> > > > +{
> > > > +	struct virtnet_info *vi = vq->vdev->priv;
> > > > +	struct receive_queue *rq;
> > > > +	int i = vq2rxq(vq);
> > > > +
> > > > +	rq = &vi->rq[i];
> > > > +
> > > > +	if (rq->do_dma)
> > > > +		virtnet_rq_unmap(rq, buf, 0);
> > > > +
> > > > +	virtnet_rq_free_buf(vi, rq, buf);
> > > > +}
> > > > +
> > > >  static void free_old_xmit_skbs(struct send_queue *sq, bool in_napi)
> > > >  {
> > > >  	unsigned int len;
> > > > @@ -1764,7 +1777,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
> > > >  	if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
> > > >  		pr_debug("%s: short packet %i\n", dev->name, len);
> > > >  		DEV_STATS_INC(dev, rx_length_errors);
> > > > -		virtnet_rq_free_unused_buf(rq->vq, buf);
> > > > +		virtnet_rq_free_buf(vi, rq, buf);
> > > >  		return;
> > > >  	}
> > > >
> > > > @@ -2392,7 +2405,7 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
> > > >  	if (running)
> > > >  		napi_disable(&rq->napi);
> > > >
> > > > -	err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
> > > > +	err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_buf_check_dma);
> > > >  	if (err)
> > > >  		netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err);
> > > >
> > > > @@ -4031,19 +4044,6 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> > > >  		xdp_return_frame(ptr_to_xdp(buf));
> > > >  }
> > > >
> > > > -static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf)
> > > > -{
> > > > -	struct virtnet_info *vi = vq->vdev->priv;
> > > > -	int i = vq2rxq(vq);
> > > > -
> > > > -	if (vi->mergeable_rx_bufs)
> > > > -		put_page(virt_to_head_page(buf));
> > > > -	else if (vi->big_packets)
> > > > -		give_pages(&vi->rq[i], buf);
> > > > -	else
> > > > -		put_page(virt_to_head_page(buf));
> > > > -}
> > > > -
> > > >  static void free_unused_bufs(struct virtnet_info *vi)
> > > >  {
> > > >  	void *buf;
> > > > @@ -4057,10 +4057,10 @@ static void free_unused_bufs(struct virtnet_info *vi)
> > > >  	}
> > > >
> > > >  	for (i = 0; i < vi->max_queue_pairs; i++) {
> > > > -		struct receive_queue *rq = &vi->rq[i];
> > > > +		struct virtqueue *vq = vi->rq[i].vq;
> > > >
> > > > -		while ((buf = virtnet_rq_detach_unused_buf(rq)) != NULL)
> > > > -			virtnet_rq_free_unused_buf(rq->vq, buf);
> > > > +		while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> > > > +			virtnet_rq_free_buf_check_dma(vq, buf);
> > > >  		cond_resched();
> > > >  	}
> > > >  }
> > > > --
> > > > 2.32.0.3.g01195cf9f
> > >
>

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