On Wed, Nov 20, 2013 at 05:07:26PM +0800, Jason Wang wrote:
> We need decrease the rq->num after we can get a buf through
> virtqueue_get_buf() even if we could not allocate frag skb. Otherwise, the
> refill routine won't be triggered under heavy memory stress since the driver may
> still think there's enough room.
>
> This bug was introduced by commit 2613af0ed18a11d5c566a81f9a6510b73180660a
> (virtio_net: migrate mergeable rx buffers to page frag allocators).
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Michael Dalton <mwdalton@xxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
So let's wrap virtqueue_get_buf to make sure we get it right?
> ---
> The patch was needed for 3.12 stable.
> ---
> drivers/net/virtio_net.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 24fd502..de1d6ca 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -333,6 +333,7 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
> head_skb->dev->stats.rx_length_errors++;
> return -EINVAL;
> }
> + --rq->num;
> if (unlikely(len > MERGE_BUFFER_LEN)) {
> pr_debug("%s: rx error: merge buffer too long\n",
> head_skb->dev->name);
> @@ -367,7 +368,6 @@ 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);
> }
> - --rq->num;
> }
> return 0;
> }
> --
> 1.8.3.2
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