On Mon, 2004-11-01 at 21:30, åää wrote:
> Hi,all
> When the GFS's version was 6.0ïits documents said that GFS supported directioã
> But now is 6.1pre2 or 6.1pre3 with Linux kernel 2.6.8.1 or 2.6.9, does it support too?
> I've tried some tests, the result showed negative. My test program has the lines as follow:
>
> #define _GNU_SOURCE 1 //for the tag O_DIRECT.
> fd=open(argv[1], O_RDONLY|O_DIRECT);
> if(fd<0) {
> perror("open");
> return -1;
> }
> readed=read(fd, buf, block_size);
> if(readed<=0) {
> perror("read");
> break;
> }
> close(fd);
>
> the result is "1. fd=3,valid. 2.read return: Invalid argument"
> I've run the same program on ext3 and gfs filesystem, the result is the same.
>
> So what's the problem, the kernel 2.6 does not support, or some kernel config problem?
>
> Another problem:
> Do I need to (or must) update GFS from 6.1pre2 with 2.6.8.1 to 6.1pre3 with 2.6.9?
> I see the cvs log "Lock_dlm and lock_gulm are broken ..."
>
> Thanks for any reply! Best regards!
>
Direct IO requires the buffer address be aligned and the size
of the i/o needs to be a multiple of 512.
This worked for me on GFS (and ext3).
#define _GNU_SOURCE 1 //for the tag O_DIRECT.
#include <fcntl.h>
#include <malloc.h>
main(int argc, char **argv)
{
int fd;
int readed;
char *buf;
int block_size = 4096;
buf = memalign(512, 4096);
fd=open(argv[1], O_RDONLY|O_DIRECT);
if(fd<0) {
perror("open");
return -1;
}
readed=read(fd, buf, block_size);
if(readed<=0) {
perror("read");
}
close(fd);
}
