netdev - Re: [PATCH net-next v7] vhost_net: avoid tx queue stuck when sendmsg fails

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Message-ID: <ff01b9da-f2a7-3559-63cc-833f52280ef6@redhat.com>
Date:   Fri, 15 Jan 2021 14:05:02 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     wangyunjian <wangyunjian@...wei.com>, netdev@...r.kernel.org
Cc:     mst@...hat.com, willemdebruijn.kernel@...il.com,
        virtualization@...ts.linux-foundation.org,
        jerry.lilijun@...wei.com, chenchanghu@...wei.com,
        xudingke@...wei.com, brian.huangbin@...wei.com
Subject: Re: [PATCH net-next v7] vhost_net: avoid tx queue stuck when sendmsg
 fails


On 2021/1/15 下午12:46, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@...wei.com>
>
> Currently the driver doesn't drop a packet which can't be sent by tun
> (e.g bad packet). In this case, the driver will always process the
> same packet lead to the tx queue stuck.
>
> To fix this issue:
> 1. in the case of persistent failure (e.g bad packet), the driver
>     can skip this descriptor by ignoring the error.
> 2. in the case of transient failure (e.g -ENOBUFS, -EAGAIN and -ENOMEM),
>     the driver schedules the worker to try again.
>
> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>


Acked-by: Jason Wang <jasowang@...hat.com>


> ---
> v7:
>     * code rebase
> v6:
>     * update code styles and commit log
> ---
>   drivers/vhost/net.c | 26 ++++++++++++++------------
>   1 file changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 3b744031ec8f..df82b124170e 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -828,14 +828,15 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
>   				msg.msg_flags &= ~MSG_MORE;
>   		}
>   
> -		/* TODO: Check specific error and bomb out unless ENOBUFS? */
>   		err = sock->ops->sendmsg(sock, &msg, len);
>   		if (unlikely(err < 0)) {
> -			vhost_discard_vq_desc(vq, 1);
> -			vhost_net_enable_vq(net, vq);
> -			break;
> -		}
> -		if (err != len)
> +			if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) {
> +				vhost_discard_vq_desc(vq, 1);
> +				vhost_net_enable_vq(net, vq);
> +				break;
> +			}
> +			pr_debug("Fail to send packet: err %d", err);
> +		} else if (unlikely(err != len))
>   			pr_debug("Truncated TX packet: len %d != %zd\n",
>   				 err, len);
>   done:
> @@ -924,7 +925,6 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
>   			msg.msg_flags &= ~MSG_MORE;
>   		}
>   
> -		/* TODO: Check specific error and bomb out unless ENOBUFS? */
>   		err = sock->ops->sendmsg(sock, &msg, len);
>   		if (unlikely(err < 0)) {
>   			if (zcopy_used) {
> @@ -933,11 +933,13 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
>   				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
>   					% UIO_MAXIOV;
>   			}
> -			vhost_discard_vq_desc(vq, 1);
> -			vhost_net_enable_vq(net, vq);
> -			break;
> -		}
> -		if (err != len)
> +			if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) {
> +				vhost_discard_vq_desc(vq, 1);
> +				vhost_net_enable_vq(net, vq);
> +				break;
> +			}
> +			pr_debug("Fail to send packet: err %d", err);
> +		} else if (unlikely(err != len))
>   			pr_debug("Truncated TX packet: "
>   				 " len %d != %zd\n", err, len);
>   		if (!zcopy_used)