n, err = w.Write(buf[:len(buf)-remain])
				if err != nil {
					return written, err
				}
				nw = int64(n)
			}

			// Disable O_DIRECT on fd's on unaligned buffer
			// perform an amortized Fdatasync(fd) on the fd at
			// the end, this is performed by the caller before
			// closing 'w'.
			if err = disk.DisableDirectIO(file); err != nil {
				return written, err
			}