Re: [RFC PATCH 2/3] vfs: Add open by file handle support

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Mar 01, 2010 at 01:25:56PM -0500, Oleg Drokin wrote:
> Hello!
> 
> On Feb 28, 2010, at 2:00 PM, J. Bruce Fields wrote:
> 
> >> If there is interest to revive this idea, I'll try to dig up the old  
> >> patches we had. I believe that they set a FS_NFS_FSID (or similarly  
> >> named) flag in the file_system_type, and possibly a method that  
> >> extracted this information for NFSd.
> > OK, sure, but if it's only of use to lustre than I don't see how to
> > justify a kernel patch.
> 
> I wonder how does GFS/OCFS2 do this? They cannot depend on the
> SAN block device to have same major:minor on every exporting node, right?

Right, libblkid calculates a uuid from the contents somehow.

> > Another option would be to provide an alternative to
> > nfs-utils/utils/mountd/cache.c's get_uuid() that can request the
> > filesystem's uuid (assuming you've got an easy way to get it from
> > userspace).  That might also save having to add yet another case to e.g.
> > fs/nfsd/nfsfh.c:set_version_and_fsid_type().
> 
> Hopefully there would be a standard way to request the uuid, not
> just a huge switch with separate code for every fstype.

Sure.

--b.