macvtap: do not add self to waitqueue if doing a nonblock read

There's no need to add self to waitqueue if doing a nonblock read. This could
help to avoid the spinlock contention.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 5e485e307424..8949631c080c 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -845,7 +845,9 @@ static ssize_t macvtap_do_read(struct macvtap_queue *q, struct kiocb *iocb,
         ssize_t ret = 0;
 
         while (len) {
-                prepare_to_wait(sk_sleep(&q->sk), &wait, TASK_INTERRUPTIBLE);
+                if (!noblock)
+                        prepare_to_wait(sk_sleep(&q->sk), &wait,
+                                        TASK_INTERRUPTIBLE);
 
                 /* Read frames from the queue */
                 skb = skb_dequeue(&q->sk.sk_receive_queue);
@@ -867,7 +869,8 @@ static ssize_t macvtap_do_read(struct macvtap_queue *q, struct kiocb *iocb,
                 break;
         }
 
-        finish_wait(sk_sleep(&q->sk), &wait);
+        if (!noblock)
+                finish_wait(sk_sleep(&q->sk), &wait);
         return ret;
 }