From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752467AbeERN0e (ORCPT ); Fri, 18 May 2018 09:26:34 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45798 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752213AbeERN0c (ORCPT ); Fri, 18 May 2018 09:26:32 -0400 Subject: Re: [PATCH net] tuntap: raise EPOLLOUT on device up To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Frederic Sowa , Eric Dumazet References: <1526648443-24128-1-git-send-email-jasowang@redhat.com> <20180518161253-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Fri, 18 May 2018 21:26:23 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180518161253-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >> + set_bit(SOCKWQ_ASYNC_NOSPACE, &tfile->socket.flags); >> return -EIO; >> + } >> >> if (!(tun->flags & IFF_NO_PI)) { >> if (len < sizeof(pi)) >> -- >> 2.7.4