tun: don't look at current when non-blocking

We play with a wait queue even if socket is
non blocking. This is an obvious waste.
Besides, it will prevent calling the non blocking
variant when current is not valid.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 807815f..7cb105c 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1293,7 +1293,8 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
        if (unlikely(!noblock))
                add_wait_queue(&tfile->wq.wait, &wait);
        while (len) {
-               current->state = TASK_INTERRUPTIBLE;
+               if (unlikely(!noblock))
+                       current->state = TASK_INTERRUPTIBLE;
 
                /* Read frames from the queue */
                if (!(skb = skb_dequeue(&tfile->socket.sk->sk_receive_queue))) {
@@ -1320,9 +1321,10 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
                break;
        }
 
-       current->state = TASK_RUNNING;
-       if (unlikely(!noblock))
+       if (unlikely(!noblock)) {
+               current->state = TASK_RUNNING;
                remove_wait_queue(&tfile->wq.wait, &wait);
+       }
 
        return ret;
 }