Re: [External Email] Re: [PATCH] Fix tun: wake up waitqueues after IFF_UP is set

Hi all,

On Mon, Jun 17, 2019 at 5:32 PM 李菲 [off-list ref] wrote:

Ok, thanks for detail suggestion! :)

On Mon, Jun 17, 2019 at 4:16 PM Jason Wang [off-list ref] wrote:

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On 2019/6/17 下午4:10, Jason Wang wrote:

quoted

On 2019/6/17 下午3:33, Fei Li wrote:

quoted

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

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Signed-off-by: Fei Li <redacted>
---
  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);

Will remove the above unused struct in next version.
Sorry for the negligence!

Have a nice day, thanks
Fei

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-    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)