O_DIRECT wierd behavior..

[Suresh Gopalakrishnan]

I tried this small piece of code from an old post in the archive:

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#define O_DIRECT	 040000	/* direct disk access hint */

int main()
{
	char buf[16384];
	int fd;
	char *p;

	p = (char *)((((unsigned long)buf) + 8191) & ~8191L);
	fd = open("/tmp/blah", O_CREAT | O_RDWR | O_DIRECT);

	printf("write returns %i\n", write(fd, buf, 8192));
	printf("write returns %i\n", write(fd, p, 1));

	return 0;
}

Output is:

write returns -1
Filesize limit exceeded (core dumped)

$ ls -l /tmp/blah
----------    1 gsuresh  users    4294967274 Dec 15 19:15 /tmp/blah

The kernel is 2.4.16 and /tmp is ext2. (It runs fine on 2.4.2).

Any idea why this happens and how to fix this?

Thanks
--suresh