From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: tuntap regression in v3.9.8 and v3.10 Date: Fri, 05 Jul 2013 11:43:30 +0800 Message-ID: <51D640E2.1010809@redhat.com> References: <20130702195910.GA20271@toau.bambla> <20130702220651.GA23097@toau.bambla> <51D39010.5090902@redhat.com> <20130703061104.GA22847@toau.bambla> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Fabio Estevam , linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Thomas Zeitlhofer , "Michael S. Tsirkin" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28119 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081Ab3GEDnt (ORCPT ); Thu, 4 Jul 2013 23:43:49 -0400 In-Reply-To: <20130703061104.GA22847@toau.bambla> Sender: netdev-owner@vger.kernel.org List-ID: On 07/03/2013 02:11 PM, Thomas Zeitlhofer wrote: > Hello Jason, > > On Wed, Jul 03, 2013 at 10:44:32AM +0800, Jason Wang wrote: >> On 07/03/2013 06:06 AM, Thomas Zeitlhofer wrote: >>> On Tue, Jul 02, 2013 at 06:01:12PM -0300, Fabio Estevam wrote: >>>> On Tue, Jul 2, 2013 at 4:59 PM, Thomas Zeitlhofer >>>> wrote: >>>>> Commit "tuntap: set SOCK_ZEROCOPY flag during open" introduces a >>>>> regression which is observed with live migration of qemu/kvm based >>>>> virtual machines that are connected to an openvswitch bridge. >>>>> >>>>> Reverting this commit (b26c93c46a3dec25ed236d4ba6107eb4ed5d9401 in >>>>> v3.9.8 and accordingly 19a6afb23e5d323e1245baa4e62755492b2f1200 in >>>>> v3.10) fixes the following problem: >>>> Should the sock_set_flag stay in tun_set_iff as it was prior to 54f968d6efd? >>>> >>>> --- a/drivers/net/tun.c >>>> +++ b/drivers/net/tun.c >>>> @@ -1652,6 +1652,7 @@ static int tun_set_iff(struct net *net, struct >>>> file *file, struct ifreq *ifr) >>>> tun->txflt.count = 0; >>>> tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr); >>>> >>>> + sock_set_flag(&tfile->sk, SOCK_ZEROCOPY); >>>> tun->filter_attached = false; >>>> tun->sndbuf = tfile->socket.sk->sk_sndbuf; >>>> >>>> @@ -2159,8 +2160,6 @@ static int tun_chr_open(struct inode *inode, >>>> struct file * file) >>>> set_bit(SOCK_EXTERNALLY_ALLOCATED, &tfile->socket.flags); >>>> INIT_LIST_HEAD(&tfile->next); >>>> >>>> - sock_set_flag(&tfile->sk, SOCK_ZEROCOPY); >>>> - >>>> return 0; >>>> } >>> I guess no, as this also leads to a kernel panic (tested against v3.10). >> Yes, commit "tuntap: set SOCK_ZEROCOPY flag during open" just re-enable >> the zerocopy capability of tuntap. I believe it just uncover other >> zerocopy bugs. >> >> Which regression did you see? > a kernel panic on the host machine. The details are in the first message > of this thread: http://lkml.org/lkml/2013/7/2/499 Could you please have a try with the patch in https://lkml.org/lkml/2013/6/25/304. Michael, please resubmit a patch which can applies cleanly. Thanks > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html