macvtap: update file current position

[ Upstream commit e6ebc7f16ca1434a334647aa56399c546be4e64b ]

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index accd468..dda5bcc 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -905,6 +905,8 @@
 
 	ret = macvtap_do_read(q, iocb, iv, len, file->f_flags & O_NONBLOCK);
 	ret = min_t(ssize_t, ret, len); /* XXX copied from tun.c. Why? */
+	if (ret > 0)
+		iocb->ki_pos = ret;
 out:
 	return ret;
 }