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Commit 9e85722d authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
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tuntap: allow polling/writing/reading when detached 



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,
  host/qemu needs to do its own cleanup on those buffers which is complex
  sometimes. We can do this simply by allowing a user can still write to an
  disabled queue. Write to an disabled queue will cause the packet pass to the
  kernel and read will get nothing.
- 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)

We can simply achieve this by don't assign NULL to tfile->tun when detached.

Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2b8b328b

drivers/net/tun.c

+16 −9
Original line number Diff line number Diff line
@@ -298,11 +298,12 @@ static void tun_flow_cleanup(unsigned long data) 
}



static void tun_flow_update(struct tun_struct *tun, u32 rxhash,

			    u16 queue_index)

			    struct tun_file *tfile)

{

	struct hlist_head *head;

	struct tun_flow_entry *e;

	unsigned long delay = tun->ageing_time;

	u16 queue_index = tfile->queue_index;



	if (!rxhash)

		return;
@@ -311,7 +312,9 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash, 


	rcu_read_lock();



	if (tun->numqueues == 1)

	/* We may get a very small possibility of OOO during switching, not

	 * worth to optimize.*/

	if (tun->numqueues == 1 || tfile->detached)

		goto unlock;



	e = tun_flow_find(head, rxhash);
@@ -411,21 +414,21 @@ 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();
@@ -473,6 +476,10 @@ 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();
@@ -503,7 +510,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file) 
		goto out;



	err = -EINVAL;

	if (rtnl_dereference(tfile->tun))

	if (rtnl_dereference(tfile->tun) && !tfile->detached)

		goto out;



	err = -EBUSY;
@@ -1202,7 +1209,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, 
	tun->dev->stats.rx_packets++;

	tun->dev->stats.rx_bytes += len;



	tun_flow_update(tun, rxhash, tfile->queue_index);

	tun_flow_update(tun, rxhash, tfile);

	return total_len;

}
@@ -1816,7 +1823,7 @@ 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);