> -----Original Message-----
> From: Jason Wang [mailto:jasow...@redhat.com]
> Sent: Thursday, December 24, 2020 11:10 AM
> To: wangyunjian <wangyunj...@huawei.com>; netdev@vger.kernel.org;
> m...@redhat.com; willemdebruijn.ker...@gmail.com
> Cc: virtualizat...@lists.linux-foundation.org; Lilijun (Jerry)
> <jerry.lili...@huawei.com>; chenchanghu <chenchan...@huawei.com>;
> xudingke <xudin...@huawei.com>; huangbin (J)
> <brian.huang...@huawei.com>
> Subject: Re: [PATCH net v4 2/2] vhost_net: fix tx queue stuck when sendmsg
> fails
>
>
> On 2020/12/24 上午10:25, wangyunjian wrote:
> > From: Yunjian Wang <wangyunj...@huawei.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 -EAGAIN and -ENOMEM), the
> > driver schedules the worker to try again.
>
>
> I might be wrong but looking at alloc_skb_with_frags(), it returns -ENOBUFS
> actually:
>
> *errcode = -ENOBUFS;
> skb = alloc_skb(header_len, gfp_mask);
> if (!skb)
> return NULL;
Yes, but the sock_alloc_send_pskb() returns - EAGAIN when no sndbuf space.
So there is need to check return value which is -EAGAIN or -ENOMEM or - EAGAIN?
struct sk_buff *sock_alloc_send_pskb()
{
...
for (;;) {
...
sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
err = -EAGAIN;
if (!timeo)
goto failure;
...
}
skb = alloc_skb_with_frags(header_len, data_len, max_page_order,
errcode, sk->sk_allocation);
if (skb)
skb_set_owner_w(skb, sk);
return skb;
...
*errcode = err;
return NULL;
}
>
> Thanks
>
>
> >
> > Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server")
> > Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
> > ---
> > drivers/vhost/net.c | 16 ++++++++--------
> > 1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index
> > c8784dfafdd7..e76245daa7f6 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -827,14 +827,13 @@ 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)) {
> > + if (unlikely(err == -EAGAIN || err == -ENOMEM)) {
> > vhost_discard_vq_desc(vq, 1);
> > vhost_net_enable_vq(net, vq);
> > break;
> > }
> > - if (err != len)
> > + if (err >= 0 && err != len)
> > pr_debug("Truncated TX packet: len %d != %zd\n",
> > err, len);
> > done:
> > @@ -922,7 +921,6 @@ 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) {
> > @@ -931,11 +929,13 @@ 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 == -EAGAIN || err == -ENOMEM) {
> > + vhost_discard_vq_desc(vq, 1);
> > + vhost_net_enable_vq(net, vq);
> > + break;
> > + }
> > }
> > - if (err != len)
> > + if (err >= 0 && err != len)
> > pr_debug("Truncated TX packet: "
> > " len %d != %zd\n", err, len);
> > if (!zcopy_used)
