buf size less than blockSize error report write err about directio HOT 4 CLOSED

package main

import (
	"github.com/ncw/directio"
	"log"
	"os"
)

func main() {
	block1 := directio.AlignedBlock(directio.BlockSize + 1)
	for i := 0; i < len(block1); i++ {
		block1[i] = 'A'
	}

	// Write the file
	out, err := directio.OpenFile("O_DIRECT.test", os.O_CREATE|os.O_WRONLY, 0666)
	defer out.Close()
	if err != nil {
		log.Fatal("Failed to directio.OpenFile for write: ", err)
	}
	_, err = out.Write(block1)
	if err != nil {
		log.Fatal("Failed to write: ", err)
	}
}

   O_DIRECT
       The O_DIRECT flag may impose alignment restrictions on the  length  and
       address  of  user-space  buffers and the file offset of I/Os.  In Linux
       alignment restrictions vary by filesystem and kernel version and  might
       be  absent entirely.  However there is currently no filesystem-indepen‐
       dent interface for an application to discover these restrictions for  a
       given  file  or  filesystem.  Some filesystems provide their own inter‐
       faces for doing so, for example the XFS_IOC_DIOINFO  operation  in  xf‐
       sctl(3).