[Lustre-discuss] Group Lock in Lustre: write call is blocking

[pascal.deveze at bull.net]

Hi,

I have seen the group lock Design at:
http://lists.lustre.org/pipermail/lustre-devel/2006-May/000071.html
I checked the group lock capabilities with the programme
parallel_grouplock.c:
http://lustre.sourcearchive.com/documentation/1.6.5/parallel__grouplock_8c-source.html

This program runs well, but ... it only tests the read function call.

I have a Lustre version 1.6.6, and on this release, the write is blocking
(I have to delete my job). I would like to use the write call.

Here is a little program to reproduce this.

Could anyone tell me if I made a mistake, if Lustre does not support the
group lock or if it is a bug in Lustre ?

Thanks very much for your help.

Best Regards,
P. Devèze

===============================================
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>
#include "lustre_user.h"

char *strerror(int errnum);
#define FILEMODE S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH
#define FILENAME        "/mnt/fs_mpi/GL"

// Process takes a GROUP_LOCK and writes
// The write call will block ===> WHY ?

int main(int argc, char *argv[]) {
        int nb, rc, fd, gid = 1;

       if ((fd = open(FILENAME, O_RDWR | O_CREAT, FILEMODE)) == -1) {
                printf("Error opening file: %s\n", strerror(errno));
                exit(-1);
        }

        if ((rc = ioctl(fd, LL_IOC_GROUP_LOCK, gid)) == -1) {
                printf("Error ioctl GROUP_LOCK on file %d: %s\n", rc,
strerror(errno));
                exit(-1);
        }
        printf("GROUP_LOCK OK, we will write on file\n");

// This write call will block

        nb=write(fd, "Hello\n", 6);
        if (nb != 6) printf("write: %s\n", strerror(errno));
        printf("write done\n");

        printf("We will free the lock\n");
        if ((rc = ioctl(fd, LL_IOC_GROUP_UNLOCK, gid)) == -1) {
                 printf("Error ioctl GROUP_UNLOCK on file %d: %s", rc,
strerror(errno));
        }
        printf("group lock is free\n");
        close(fd);
}
=============================================================