Re: Adding an ioctl to check for disklabel existence

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Mon, 30 Sep 2019 06:43:10 -0000 (UTC)
    From:        mlelstv%serpens.de@localhost (Michael van Elst)
    Message-ID:  <qms85t$a45$1%serpens.de@localhost>

  | It also says 'fictitious' when you then write that label and read it
  | back (and that magic word is also used by the wedge naming code to
  | be treated like an empty label).

Yes, the idea (the one change that would be needed) was to delete
(blank/zero out) the label in the label read from disc routine(s)
if it is seen to contain "fictitious" - then the wedge code wouldn't
need to deal with it.

  | It might be easier to use a different, more obscure field in the
  | disklabel instead of d_packname (the "label" field) for such magic
  | values.

It makes little difference, whatever is used when the kernel invents one,
disklabel (or at least old versions of it) will simply write it to disc
when making (unrelated) changes.

The kernel is already using this field - inserting its magic value, we
don't really want that in a from disc label, so fixing the label read
routine(s) to delete it is probably worth doing whether or not Martin
decides to use this, or another method, to deal with non disklabel labels
that have been translated.

kre