netdev - [PATCH 1/2] virtio_net: fix for stuck when change rx ring size with dev down

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Message-Id: <20220811080258.79398-2-xuanzhuo@linux.alibaba.com>
Date:   Thu, 11 Aug 2022 16:02:57 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     virtualization@...ts.linux-foundation.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Kangjie Xu <kangjie.xu@...ux.alibaba.com>
Subject: [PATCH 1/2] virtio_net: fix for stuck when change rx ring size with dev down

When dev is set to DOWN state, napi has been disabled, if we modify the
ring size at this time, we should not call napi_disable() again, which
will cause stuck.

And all operations are under the protection of rtnl_lock, so there is no
need to consider concurrency issues.

Reported-by: Kangjie Xu <kangjie.xu@...ux.alibaba.com>
Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 816c613c22f7..17687eb3f0bd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1892,11 +1892,13 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
 static int virtnet_rx_resize(struct virtnet_info *vi,
 			     struct receive_queue *rq, u32 ring_num)
 {
+	bool running = netif_running(vi->dev);
 	int err, qindex;
 
 	qindex = rq - vi->rq;
 
-	napi_disable(&rq->napi);
+	if (running)
+		napi_disable(&rq->napi);
 
 	err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
 	if (err)
@@ -1905,7 +1907,8 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
 	if (!try_fill_recv(vi, rq, GFP_KERNEL))
 		schedule_delayed_work(&vi->refill, 0);
 
-	virtnet_napi_enable(rq->vq, &rq->napi);
+	if (running)
+		virtnet_napi_enable(rq->vq, &rq->napi);
 	return err;
 }
 
-- 
2.31.0