On Tue, 2008-09-02 at 17:48 -0400, Christoph Hellwig wrote: > On Tue, Sep 02, 2008 at 10:26:09PM +0100, David Woodhouse wrote: > > > We also called the filesystem part of the NFS filehandle in a few > > > places, and for those it's correct that it should be stable. Currently > > > the fsid is either created from the dev_t in kernelspace or from > > > uuids extracted through libuuid in userspace. > > > > Or from the f_fsid returned in statfs(), as of a week or so ago. > > I think that's a rather bad idea. As mentioned before f_fsid is > basically random. It's not that bad. Of the file systems which actually fill it in... For NTFS it's the volume serial number. For ext[234] it's the UUID xor-folded into 64 bits. For btrfs the same, but with the root object ID xor'd in too. For bfs and xfs it's the block device -- which isn't ideal, as Andreas points out, but is what we'd fall back to anyway. BFS seems to have a s_volume field which perhaps we could use, but we should check for it being all spaces and leave f_fsid as zero in that case. Presumably XFS could be using sb_uuid? For efs, it'll be either EFS_MAGIC or EFS_NEWMAGIC, which is probably a bad thing if you want to export multiple EFS file systems. I'll send a patch to fix that (by leaving it zero) shortly. -- David Woodhouse Open Source Technology Centre David.Woodhouse@xxxxxxxxx Intel Corporation -- 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
