If we call fiemap on a truncated file with none blocks allocated,
it makes sense we get nothing from this call. No output means
no blocks have been counted, but the call succeeded. It's a valid
response.
Signed-off-by: Murphy Zhou <jencce.kernel@gmail.com> Signed-off-by: Steve French <stfrench@microsoft.com> Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com> CC: Stable <stable@vger.kernel.org>