Re: Adding an ioctl to check for disklabel existence

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

    Date:        Wed, 2 Oct 2019 10:48:26 -0400 (EDT)
    From:        Mouse <mouse%Rodents-Montreal.ORG@localhost>
    Message-ID:  <201910021448.KAA25424%Stone.Rodents-Montreal.ORG@localhost>

  | If _that_'s what you're concerned about, then just grow the relevant
  | fields (and, presumably, change the magic number).

Any change to the label format or semantics would make it be a
completely different object, no longer compatible with anything.

If we were going to invent something new that way, we may as well
make it lots better - and ideally compatible with other systems
so we can read one another's drives.

That's what GPT is, and it is already supported.   Why would we want
to invent something new, just to be different?

  | Or fix sector sizes other than 512 bytes.

disklabels work fine with drives with different sector sizes, and scale
the size limit proportionally, but only on drives with different sector
sizes.

There was a fad for making drives export bigger sector sizes for a while,
mostly, I suspect, because MBR has the same limitation as disklabel does.
Now GPT is widely available, everything seems to be back advertising 512
byte sectors again (regardless of whatever happens to be the way the physical
drive is used - which with caching, and likely full track reads most of the
time, is difficult to observe externally).

kre