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

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

[Fei Li]

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.

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;
 	}
-- 
2.11.0

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

[Jason Wang]

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.
>
> 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)

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

[Jason Wang]

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)
>

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

[李菲]

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)
> >

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

[李菲]

Hi all,

On Mon, Jun 17, 2019 at 5:32 PM 李菲 <lifei.shirley@bytedance.com> wrote:
>
> Ok, thanks for 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);
Will remove the above unused struct in next version.
Sorry for the negligence!

Have a nice day, thanks
Fei


>> >> -    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)
>> >