From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758204Ab3APGRQ (ORCPT ); Wed, 16 Jan 2013 01:17:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:28606 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757831Ab3APGRO (ORCPT ); Wed, 16 Jan 2013 01:17:14 -0500 From: Jason Wang To: "Michael S. Tsirkin" Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V4 3/3] tuntap: allow polling/writing/reading when detached Date: Wed, 16 Jan 2013 14:17:06 +0800 Message-ID: <3742551.hhCnEOvBmh@jason-thinkpad-t430s> User-Agent: KMail/4.9.3 (Linux/3.7.0-rc7+; KDE/4.9.3; x86_64; ; ) In-Reply-To: <20130115164808.GA8792@redhat.com> References: <1358245726-16250-1-git-send-email-jasowang@redhat.com> <1358245726-16250-4-git-send-email-jasowang@redhat.com> <20130115164808.GA8792@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, January 15, 2013 06:48:08 PM Michael S. Tsirkin wrote: > On Tue, Jan 15, 2013 at 06:28:46PM +0800, Jason Wang wrote: > > We forbid polling, writing and reading when the file were detached, this > > may complex the user in several cases: > > > > - when guest pass some buffers to vhost/qemu and then disable some queues, > > > > vhost/qemu needs to to its own cleanup which is complex. We can do this > > simply by allowing a user can still write to an disabled queue to > > handle this. And user can still do read but just nothing returned. > > > > - align the polling behavior with macvtap which never fails when the queue > > is> > > created. this can simplify the polling errors handling of its user (e.g > > vhost)> > > Signed-off-by: Jason Wang > > --- > > > > drivers/net/tun.c | 18 +++++++++++------- > > 1 files changed, 11 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > index af372d0..eb68937 100644 > > --- a/drivers/net/tun.c > > +++ b/drivers/net/tun.c > > @@ -307,7 +307,7 @@ static void tun_flow_update(struct tun_struct *tun, > > u32 rxhash,> > > rcu_read_lock(); > > > > - if (tun->numqueues == 1) > > + if (tun->numqueues == 1 || queue_index >= tun->numqueues) > > > > goto unlock; > > > > e = tun_flow_find(head, rxhash); > > Hmm I don't understand - does something ensure that queue_index is > > numqueues if the queue is disabled? I miss this, something is needed. > Can we check tun->disabled and skip tun_flow_update completely? > We might need to switch to rcu_assign for tun->disabled for this > but otherwise it looks easy. Correct, will post another version, thanks. > > > @@ -406,21 +406,21 @@ static void __tun_detach(struct tun_file *tfile, > > bool clean)> > > tun = rtnl_dereference(tfile->tun); > > > > - if (tun) { > > + if (tun && !tfile->detached) { > > > > u16 index = tfile->queue_index; > > BUG_ON(index >= tun->numqueues); > > dev = tun->dev; > > > > rcu_assign_pointer(tun->tfiles[index], > > > > tun->tfiles[tun->numqueues - 1]); > > > > - rcu_assign_pointer(tfile->tun, NULL); > > > > ntfile = rtnl_dereference(tun->tfiles[index]); > > ntfile->queue_index = index; > > > > --tun->numqueues; > > > > - if (clean) > > + if (clean) { > > + rcu_assign_pointer(tfile->tun, NULL); > > > > sock_put(&tfile->sk); > > > > - else > > + } else > > > > tun_disable_queue(tun, tfile); > > > > synchronize_net(); > > > > @@ -465,6 +465,10 @@ static void tun_detach_all(struct net_device *dev) > > > > rcu_assign_pointer(tfile->tun, NULL); > > --tun->numqueues; > > > > } > > > > + list_for_each_entry(tfile, &tun->disabled, next) { > > + wake_up_all(&tfile->wq.wait); > > + rcu_assign_pointer(tfile->tun, NULL); > > + } > > > > BUG_ON(tun->numqueues != 0); > > > > synchronize_net(); > > > > @@ -491,7 +495,7 @@ static int tun_attach(struct tun_struct *tun, struct > > file *file)> > > int err; > > > > err = -EINVAL; > > > > - if (rtnl_dereference(tfile->tun)) > > + if (rtnl_dereference(tfile->tun) && !tfile->detached) > > > > goto out; > > > > err = -EBUSY; > > > > @@ -1795,7 +1799,7 @@ static int tun_set_queue(struct file *file, struct > > ifreq *ifr)> > > ret = tun_attach(tun, file); > > > > } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) { > > > > tun = rtnl_dereference(tfile->tun); > > > > - if (!tun || !(tun->flags & TUN_TAP_MQ)) > > + if (!tun || !(tun->flags & TUN_TAP_MQ) || tfile->detached) > > > > ret = -EINVAL; > > > > else > > > > __tun_detach(tfile, false); > > -- > 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