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: Wed, 03 Jul 2013 10:44:32 +0800 Message-ID: <51D39010.5090902@redhat.com> References: <20130702195910.GA20271@toau.bambla> <20130702220651.GA23097@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 Return-path: In-Reply-To: <20130702220651.GA23097@toau.bambla> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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? Thanks