On Sep 02, 2008 10:03 +0300, Artem Bityutskiy wrote: > On Mon, 2008-09-01 at 11:01 -0400, Christoph Hellwig wrote: > > > For btrfs I xor the first 64 bits with the second 64 bits, and put > > > _that_ into f_fsid. You're just putting the first 64 bits in and > > > ignoring the second 64 bits. Neither is really _better_ than the other; > > > you just alter the circumstances in which you get collisions. But I > > > suppose we might as well be consistent about how we do it? > > > > XFS just puts in the st_dev. And I can't realy find any useful > > defintion of what it's supposed to b anyway.. > > For me this means that we should rather do what XFS does for > consistency then. The fsid is supposed to be a persistent, unique identifier for the filesystem, used by NFS in file handles. Using st_dev is unsafe, because that may change from one server boot to the next, because of device probing order, driver changes, etc. Also, not all filesystems HAVE a valid st_dev in the first place, which is the whole reason for this thread. I think a ->get_fsid() export method would be preferable. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
