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: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ffdb844..2917a86 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -298,11 +298,12 @@
}
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 @@
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 @@
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 @@
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 @@
goto out;
err = -EINVAL;
- if (rtnl_dereference(tfile->tun))
+ if (rtnl_dereference(tfile->tun) && !tfile->detached)
goto out;
err = -EBUSY;
@@ -1202,7 +1209,7 @@
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 @@
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);