commit 8fc75bed upstream.

Ensure that we return the fatal error value that caused us to exit
nfs_page_async_flush().

Fixes: c373fff7 ("NFSv4: Don't special case "launder"")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org # v4.12+
Reviewed-by: NBenjamin Coddington <bcodding@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>