dlm: use fl_owner from lockd

dlm: use fl_owner from lockd

This patch is changing the fl_owner value in case of an nfs lock request
to not be the pid of lockd. Instead this patch changes it to be the
owner value that nfs is giving us.

Currently there exists proved problems with this behaviour. One nfsd
server was created to export a gfs2 filesystem mount. Two nfs clients
doing a nfs mount of this export. Those two clients should conflict each
other operating on the same nfs file.

A small test program was written:

int main(int argc, const char *argv[])
{
	struct flock fl = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_SET,
		.l_start = 1L,
		.l_len = 1L,
	};
	int fd;

	fd = open("filename", O_RDWR | O_CREAT, 0700);
	printf("try to lock...\n");
	fcntl(fd, F_SETLKW, &fl);
	printf("locked!\n");
	getc(stdin);

	return 0;
}

Running on both clients at the same time and don't interrupting by
pressing any key. It will show that both clients are able to acquire the
lock which shouldn't be the case. The issue is here that the fl_owner
value is the same and the lock context of both clients should be
separated.

This patch lets lockd define how to deal with lock contexts and chose
hopefully the right fl_owner value. A test after this patch was made and
the locks conflicts each other which should be the case.

Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>