From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932265Ab3K1DPA (ORCPT ); Wed, 27 Nov 2013 22:15:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34099 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753935Ab3K1DO4 (ORCPT ); Wed, 27 Nov 2013 22:14:56 -0500 Message-ID: <5296B525.5060509@redhat.com> Date: Thu, 28 Nov 2013 11:14:45 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org CC: Rusty Russell , Michael Dalton , Eric Dumazet , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH 1/2] virtio_net: fix error handling for mergeable buffers References: <1385569684-26595-1-git-send-email-mst@redhat.com> In-Reply-To: <1385569684-26595-1-git-send-email-mst@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/28/2013 12:31 AM, Michael S. Tsirkin wrote: > Eric Dumazet noticed that if we encounter an error > when processing a mergeable buffer, we don't > dequeue all of the buffers from this packet, > the result is almost sure to be loss of networking. > > Jason Wang noticed that we also leak a page and that we don't decrement > the rq buf count, so we won't repost buffers (a resource leak). > > Fix both issues, and also make the logic a bit more > robust against device errors by not looping when e.g. because of a leak > like the one we are fixing here the number of buffers is 0. > > Cc: Rusty Russell > Cc: Michael Dalton > Reported-by: Eric Dumazet > Reported-by: Jason Wang > Signed-off-by: Michael S. Tsirkin > --- > > Note: this bugfix is needed on stable too, but backport > might not be trivial. > I'll send a backport for stable separately. That will be fine. > > drivers/net/virtio_net.c | 84 ++++++++++++++++++++++++++++++------------------ > 1 file changed, 52 insertions(+), 32 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 7bab4de..0e6ea69 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -299,41 +299,53 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq, > return skb; > } > > -static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb) > +static struct sk_buff *receive_mergeable(struct net_device *dev, > + struct receive_queue *rq, > + void *buf, > + unsigned int len) > { > - struct skb_vnet_hdr *hdr = skb_vnet_hdr(head_skb); > + struct skb_vnet_hdr *hdr = buf; > + int num_buf = hdr->mhdr.num_buffers; > + struct page *page = virt_to_head_page(buf); > + int offset = buf - page_address(page); > + struct sk_buff *head_skb = page_to_skb(rq, page, offset, len, > + MERGE_BUFFER_LEN); > struct sk_buff *curr_skb = head_skb; > - char *buf; > - struct page *page; > - int num_buf, len, offset; > > - num_buf = hdr->mhdr.num_buffers; > + if (unlikely(!curr_skb)) > + goto err_skb; > + > while (--num_buf) { > - int num_skb_frags = skb_shinfo(curr_skb)->nr_frags; > + int num_skb_frags; > + > buf = virtqueue_get_buf(rq->vq, &len); > if (unlikely(!buf)) { > - pr_debug("%s: rx error: %d buffers missing\n", > - head_skb->dev->name, hdr->mhdr.num_buffers); > - head_skb->dev->stats.rx_length_errors++; > - return -EINVAL; > + pr_debug("%s: rx error: %d buffers out of %d missing\n", > + dev->name, num_buf, hdr->mhdr.num_buffers); > + dev->stats.rx_length_errors++; > + goto err_buf; Not sure it's correct here. Since the we break immediately if buffer is missed in err_buf and rx_length_error will be miss counted. Maybe an ERR_PTR(-EINVAL) is better. > } > if (unlikely(len > MERGE_BUFFER_LEN)) { > pr_debug("%s: rx error: merge buffer too long\n", > - head_skb->dev->name); > + dev->name); > len = MERGE_BUFFER_LEN; > } > + > + page = virt_to_head_page(buf); > + --rq->num; > + > + num_skb_frags = skb_shinfo(curr_skb)->nr_frags; > if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) { > struct sk_buff *nskb = alloc_skb(0, GFP_ATOMIC); > - if (unlikely(!nskb)) { > - head_skb->dev->stats.rx_dropped++; > - return -ENOMEM; > - } > + > + if (unlikely(!nskb)) > + goto err_skb; > if (curr_skb == head_skb) > skb_shinfo(curr_skb)->frag_list = nskb; > else > curr_skb->next = nskb; > - curr_skb = nskb; > head_skb->truesize += nskb->truesize; > + curr_skb = nskb; This change seems unnecessary. Other looks good. > num_skb_frags = 0; > } > if (curr_skb != head_skb) { > @@ -341,8 +353,7 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb) > head_skb->len += len; > head_skb->truesize += MERGE_BUFFER_LEN; > } > - page = virt_to_head_page(buf); > - offset = buf - (char *)page_address(page); > + offset = buf - page_address(page); > if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) { > put_page(page); > skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1, > @@ -351,9 +362,28 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb) > skb_add_rx_frag(curr_skb, num_skb_frags, page, > offset, len, MERGE_BUFFER_LEN); > } > + } > + > + return head_skb; > + > +err_skb: > + put_page(page); > +err_buf: > + dev->stats.rx_dropped++; > + dev_kfree_skb(head_skb); > + while (--num_buf) { > + buf = virtqueue_get_buf(rq->vq, &len); > + if (unlikely(!buf)) { > + pr_debug("%s: rx error: %d buffers missing\n", > + dev->name, num_buf); > + dev->stats.rx_length_errors++; > + break; > + } > + page = virt_to_head_page(buf); > + put_page(page); > --rq->num; > } > - return 0; > + return NULL; > } > > static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) > @@ -382,19 +412,9 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) > len -= sizeof(struct virtio_net_hdr); > skb_trim(skb, len); > } else if (vi->mergeable_rx_bufs) { > - struct page *page = virt_to_head_page(buf); > - skb = page_to_skb(rq, page, > - (char *)buf - (char *)page_address(page), > - len, MERGE_BUFFER_LEN); > - if (unlikely(!skb)) { > - dev->stats.rx_dropped++; > - put_page(page); > + skb = receive_mergeable(dev, rq, buf, len); > + if (unlikely(!skb)) > return; > - } > - if (receive_mergeable(rq, skb)) { > - dev_kfree_skb(skb); > - return; > - } > } else { > page = buf; > skb = page_to_skb(rq, page, 0, len, PAGE_SIZE);