[PATCH 3.8 160/166] virtio_net: fix error handling for mergeable buffers

Kamal Mostafa
2014-01-15T21:52:54Z

From: "Michael S. Tsirkin" <mst@redhat.com>

commit 8fc3b9e9a229778e5af3aa453c44f1a3857ba769 upstream.

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.

Fix this issue.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael Dalton <mwdalton@google.com>
Acked-by: Michael Dalton <mwdalton@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: David S. Miller <davem@davemloft.net>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

(cherry picked from commit 8fc3b9e9a229778e5af3aa453c44f1a3857ba769)
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/net/virtio_net.c | 66 +++++++++++++++++++++++++++++++++---------------
1 file changed, 46 insertions(+), 20 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fa2385a..184c59c 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -294,26 +294,33 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
return skb;
}

-static int receive_mergeable(struct receive_queue *rq, struct sk_buff *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(skb);
- struct page *page;
- int num_buf, i, len;
+ struct skb_vnet_hdr *hdr = page_address(buf);
+ int num_buf = hdr->mhdr.num_buffers;
+ struct page *page = buf;
+ struct sk_buff *skb = page_to_skb(rq, page, len);
+ int i;
+
+ if (unlikely(!skb))
+ goto err_skb;

- num_buf = hdr->mhdr.num_buffers;
while (--num_buf) {
i = skb_shinfo(skb)->nr_frags;
if (i >= MAX_SKB_FRAGS) {
pr_debug("%s: packet too long\n", skb->dev->name);
skb->dev->stats.rx_length_errors++;
- return -EINVAL;
+ return NULL;
}
page = virtqueue_get_buf(rq->vq, &len);
if (!page) {
- pr_debug("%s: rx error: %d buffers missing\n",
- skb->dev->name, hdr->mhdr.num_buffers);
- skb->dev->stats.rx_length_errors++;
- return -EINVAL;
+ pr_debug("%s: rx error: %d buffers %d missing\n",
+ dev->name, hdr->mhdr.num_buffers, num_buf);
+ dev->stats.rx_length_errors++;
+ goto err_buf;
}

if (len > PAGE_SIZE)
@@ -323,7 +330,25 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)

--rq->num;
}
- return 0;
+ return skb;
+err_skb:
+ give_pages(rq, page);
+ 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 = buf;
+ give_pages(rq, page);
+ --rq->num;
+ }
+err_buf:
+ dev->stats.rx_dropped++;
+ dev_kfree_skb(skb);
+ return NULL;
}

static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
@@ -351,17 +376,18 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
skb_trim(skb, len);
} else {
page = buf;
- skb = page_to_skb(rq, page, len);
- if (unlikely(!skb)) {
- dev->stats.rx_dropped++;
- give_pages(rq, page);
- return;
- }
- if (vi->mergeable_rx_bufs)
- if (receive_mergeable(rq, skb)) {
- dev_kfree_skb(skb);
+ if (vi->mergeable_rx_bufs) {
+ skb = receive_mergeable(dev, rq, page, len);
+ if (unlikely(!skb))
+ return;
+ } else {
+ skb = page_to_skb(rq, page, len);
+ if (unlikely(!skb)) {
+ dev->stats.rx_dropped++;
+ give_pages(rq, page);
return;
}
+ }
}

hdr = skb_vnet_hdr(skb);
--
1.8.3.2