From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] tuntap: raise EPOLLOUT on device up Date: Fri, 18 May 2018 17:06:23 +0300 Message-ID: <20180518170155-mutt-send-email-mst@kernel.org> References: <1526648443-24128-1-git-send-email-jasowang@redhat.com> <20180518161253-mutt-send-email-mst@kernel.org> <6159b23e-eeda-1d4b-6a30-63b1a30666eb@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Frederic Sowa , Eric Dumazet To: Jason Wang Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51668 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752573AbeEROGZ (ORCPT ); Fri, 18 May 2018 10:06:25 -0400 Content-Disposition: inline In-Reply-To: <6159b23e-eeda-1d4b-6a30-63b1a30666eb@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, May 18, 2018 at 10:00:31PM +0800, Jason Wang wrote: > > > On 2018年05月18日 21:26, Jason Wang wrote: > > > > > > On 2018年05月18日 21:13, Michael S. Tsirkin wrote: > > > On Fri, May 18, 2018 at 09:00:43PM +0800, Jason Wang wrote: > > > > We return -EIO on device down but can not raise EPOLLOUT after it was > > > > up. This may confuse user like vhost which expects tuntap to raise > > > > EPOLLOUT to re-enable its TX routine after tuntap is down. This could > > > > be easily reproduced by transmitting packets from VM while down and up > > > > the tap device. Fixing this by set SOCKWQ_ASYNC_NOSPACE on -EIO. > > > > > > > > Cc: Hannes Frederic Sowa > > > > Cc: Eric Dumazet > > > > Fixes: 1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()") > > > > Signed-off-by: Jason Wang > > > > --- > > > >   drivers/net/tun.c | 4 +++- > > > >   1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > > > index d45ac37..1b29761 100644 > > > > --- a/drivers/net/tun.c > > > > +++ b/drivers/net/tun.c > > > > @@ -1734,8 +1734,10 @@ static ssize_t tun_get_user(struct > > > > tun_struct *tun, struct tun_file *tfile, > > > >       int skb_xdp = 1; > > > >       bool frags = tun_napi_frags_enabled(tun); > > > >   -    if (!(tun->dev->flags & IFF_UP)) > > > > +    if (!(tun->dev->flags & IFF_UP)) { > > > Isn't this racy?  What if flag is cleared at this point? > > > > I think you mean "set at this point"? Then yes, so we probably need to > > set the bit during tun_net_close(). > > > > Thanks > > Looks no need, vhost will poll socket after it see EIO. So we are ok here? > > Thanks In fact I don't even understand why does this help any longer. -- MST