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SubjectRe: [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@redhat.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@bytedance.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@redhat.com)
> >

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