From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net 1/3] virtio-net: drop the rest of buffers when we can't allocate skb Date: Wed, 20 Nov 2013 12:34:06 +0200 Message-ID: <20131120103406.GF19341@redhat.com> References: <1384938447-3775-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Michael Dalton , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Eric Dumazet , Shirley Ma To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1384938447-3775-1-git-send-email-jasowang@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Wed, Nov 20, 2013 at 05:07:25PM +0800, Jason Wang wrote: > When mergeable buffer were used, we only put the first page buf leave the rest > of buffers in the virt queue. This will cause the driver could not get the > correct head buffer any more. Fix this by dropping the rest of buffers for this > packet. > > The bug was introduced by commit 9ab86bbcf8be755256f0a5e994e0b38af6b4d399 > (virtio_net: Defer skb allocation in receive path). > > Cc: Rusty Russell > Cc: Michael S. Tsirkin > Cc: Michael Dalton > Cc: Eric Dumazet > Cc: Shirley Ma > Signed-off-by: Jason Wang > --- > This patch was needed for stable > --- > drivers/net/virtio_net.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 7bab4de..24fd502 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -222,6 +222,17 @@ static void skb_xmit_done(struct virtqueue *vq) > netif_wake_subqueue(vi->dev, vq2txq(vq)); > } > > +static void drop_mergeable_buffer(struct receive_queue *rq, int num_buf) > +{ > + char *buf; > + int len; > + > + while (--num_buf && (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) { > + --rq->num; > + put_page(virt_to_head_page(buf)); > + } > +} > + This is the same code we have in receive_mergeable anyway. So let's reuse that. > /* Called from bottom half context */ > static struct sk_buff *page_to_skb(struct receive_queue *rq, > struct page *page, unsigned int offset, > @@ -237,8 +248,13 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq, > > /* copy small packet so we can reuse these pages for small data */ > skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); > - if (unlikely(!skb)) > + if (unlikely(!skb)) { > + if (vi->mergeable_rx_bufs) { > + hdr = (struct skb_vnet_hdr *)p; > + drop_mergeable_buffer(rq, hdr->mhdr.num_buffers); > + } > return NULL; > + } > > hdr = skb_vnet_hdr(skb); > > -- > 1.8.3.2