netdev - Re: [External Email] Re: [PATCH] Fix tun: wake up waitqueues after IFF

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Date:   Mon, 17 Jun 2019 17:58:38 +0800
From:   李菲 <lifei.shirley@...edance.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [External Email] Re: [PATCH] Fix tun: wake up waitqueues after
 IFF_UP is set

Ok, thanks for the detail suggestion! :)


On Mon, Jun 17, 2019 at 4:16 PM Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2019/6/17 下午4:10, Jason Wang wrote:
> >
> > On 2019/6/17 下午3:33, Fei Li wrote:
> >> Currently after setting tap0 link up, the tun code wakes tx/rx waited
> >> queues up in tun_net_open() when .ndo_open() is called, however the
> >> IFF_UP flag has not been set yet. If there's already a wait queue, it
> >> would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
> >> Then the saving vhost_poll_start() will add the wq into wqh until it
> >> is waken up again. Although this works when IFF_UP flag has been set
> >> when tun_chr_poll detects; this is not true if IFF_UP flag has not
> >> been set at that time. Sadly the latter case is a fatal error, as
> >> the wq will never be waken up in future unless later manually
> >> setting link up on purpose.
> >>
> >> Fix this by moving the wakeup process into the NETDEV_UP event
> >> notifying process, this makes sure IFF_UP has been set before all
> >> waited queues been waken up.
>
>
> Btw, the title needs some tweak. E.g you need use "net" as prefix since
> it's a fix for net.git and "Fix" could be removed like:
>
> [PATCH net] tun: wake up waitqueues after IFF_UP is set.
>
> Thanks
>
>
> >>
> >> Signed-off-by: Fei Li <lifei.shirley@...edance.com>
> >> ---
> >>   drivers/net/tun.c | 17 +++++++++--------
> >>   1 file changed, 9 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> >> index c452d6d831dd..a3c9cab5a4d0 100644
> >> --- a/drivers/net/tun.c
> >> +++ b/drivers/net/tun.c
> >> @@ -1015,17 +1015,9 @@ static void tun_net_uninit(struct net_device
> >> *dev)
> >>   static int tun_net_open(struct net_device *dev)
> >>   {
> >>       struct tun_struct *tun = netdev_priv(dev);
> >> -    int i;
> >>         netif_tx_start_all_queues(dev);
> >>   -    for (i = 0; i < tun->numqueues; i++) {
> >> -        struct tun_file *tfile;
> >> -
> >> -        tfile = rtnl_dereference(tun->tfiles[i]);
> >> - tfile->socket.sk->sk_write_space(tfile->socket.sk);
> >> -    }
> >> -
> >>       return 0;
> >>   }
> >>   @@ -3634,6 +3626,7 @@ static int tun_device_event(struct
> >> notifier_block *unused,
> >>   {
> >>       struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> >>       struct tun_struct *tun = netdev_priv(dev);
> >> +    int i;
> >>         if (dev->rtnl_link_ops != &tun_link_ops)
> >>           return NOTIFY_DONE;
> >> @@ -3643,6 +3636,14 @@ static int tun_device_event(struct
> >> notifier_block *unused,
> >>           if (tun_queue_resize(tun))
> >>               return NOTIFY_BAD;
> >>           break;
> >> +    case NETDEV_UP:
> >> +        for (i = 0; i < tun->numqueues; i++) {
> >> +            struct tun_file *tfile;
> >> +
> >> +            tfile = rtnl_dereference(tun->tfiles[i]);
> >> + tfile->socket.sk->sk_write_space(tfile->socket.sk);
> >> +        }
> >> +        break;
> >>       default:
> >>           break;
> >>       }
> >
> >
> > Acked-by: Jason Wang <jasowang@...hat.com)
> >