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    Subject[PATCH 3.10 25/54] virtio-net: fix the race between channels setting and refill
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jason Wang <jasowang@redhat.com>

    [ Upstream commit 9b9cd8024a2882e896c65222aa421d461354e3f2 ]

    Commit 55257d72bd1c51f25106350f4983ec19f62ed1fa (virtio-net: fill only rx queues
    which are being used) tries to refill on demand when changing the number of
    channels by call try_refill_recv() directly, this may race:

    - the refill work who may do the refill in the same time
    - the try_refill_recv() called in bh since napi was not disabled

    Which may led guest complain during setting channels:

    virtio_net virtio0: input.1:id 0 is not a head!

    Solve this issue by scheduling a refill work which can guarantee the
    serialization of refill.

    Signed-off-by: Jason Wang <jasowang@redhat.com>
    Cc: Sasha Levin <sasha.levin@oracle.com>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    Cc: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/virtio_net.c | 5 +----
    1 file changed, 1 insertion(+), 4 deletions(-)

    --- a/drivers/net/virtio_net.c
    +++ b/drivers/net/virtio_net.c
    @@ -902,7 +902,6 @@ static int virtnet_set_queues(struct vir
    struct scatterlist sg;
    struct virtio_net_ctrl_mq s;
    struct net_device *dev = vi->dev;
    - int i;

    if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
    return 0;
    @@ -916,10 +915,8 @@ static int virtnet_set_queues(struct vir
    queue_pairs);
    return -EINVAL;
    } else {
    - for (i = vi->curr_queue_pairs; i < queue_pairs; i++)
    - if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
    - schedule_delayed_work(&vi->refill, 0);
    vi->curr_queue_pairs = queue_pairs;
    + schedule_delayed_work(&vi->refill, 0);
    }

    return 0;



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