read failed EINVAL with O_DIRECT flag

[Yves Crespin <crespin.quartz@wanadoo.fr>]

Hello,

Using O_DIRECT flag, read() failed and errno is EINVAL.
kernel 2.4.22
Filesystem Ext3 mount on /home
What's wrong ?
Thanks

Yves Crespin

#gcc -Wall -D_GNU_SOURCE direct.c -o direct
#cp direct d
#./direct d
#open failed [d] 040402 0666 errno 22
#

/* --- start code --- */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>

#define O_BINARY    0

int main(int argc,char *argv[])
{
   struct stat    sbuf;
   char    buf[8192];
   int    openFlags;
   int    fd;
   int    nb;
   int    size;

   if (argc!=2){
       printf("Missing file name\n");
       exit(2);
   }
   openFlags = O_RDWR|O_BINARY|O_NOCTTY;
   openFlags |= O_DIRECT;    /* Not POSIX */
   fd = open(argv[1],openFlags,0666);
   if (fd==-1){
       printf("open failed [%s] %#o %#o errno 
%d\n",argv[1],openFlags,0666,errno);
       exit(1);
   }
   if (fstat(fd,&sbuf)<0){
       printf("fstat failed\n");
       exit(1);
   }
   size = sbuf.st_blksize;
   if (size > sizeof(buf)){
       printf("Page size too big\n");
       exit(3);
   }
   if (size > sbuf.st_size){
       printf("File too small\n");
       exit(3);
   }
   nb = read(fd,buf,size);
   if (nb != size){
       printf("read failed fd %d size %d nb %d errno 
%d\n",fd,size,nb,errno);
       exit(1);
   }
   if (close(fd)){
       printf("close failed\n");
       exit(1);
   }
   return 0;
}
/* --- end code --- */


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