Re: [PATCH -V14 0/11] Generic name to handle and open by handle syscalls

[Neil Brown <neilb@suse.de>]

On Wed, 7 Jul 2010 09:23:51 +1000
Dave Chinner <david@fromorbit.com> wrote:

> > I can add a new syscall that returns 
> > 
> > struct fs_uuid {
> >        u8 fs_uuid[16];  
> > };
> > 
> > long sys_get_fs_uuid(int dfd, char *name, struct fs_uuid *fsid, int flag);  
> 
> libblkid already provides the UUID to userspace applications, doesn't it?

Yes and no.

libblkid provides the uuid of the thing that uses a block device.  That
doesn't directly map to "UUID of a filesystem".

There are two types of filesystem that I can think of for which libblkid
cannot give a uuid.
  - network filesystems (or virtual filesystems, or fuse )
  - filesystems which share a block device, such as btrfs.
    btrfs can have 'subvols' - multiple "filesystems" within
    the one (set of) block device(s).  libblkid cannot be asked about these
    different subvols.

libblkid is useful, but not a real solution.

NeilBrown