Re: vnd.c 1.254

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

    Date:        Sun, 17 Jan 2016 14:49:23 +0100
    From:        Manuel Bouyer <bouyer%antioche.eu.org@localhost>
    Message-ID:  <20160117134923.GA2010%asim.lip6.fr@localhost>


  | I mean, vnconfig -l (without other arguments) has been showing available
  | devices for a long time:

Yes, I know, and agree, it has ... but that is only possible if it
is possible to rationally enumerate the available devices.   When there
were a fixed (small) number, it made sense.  That is no longer the case.

Do you really want it to list 4 billion free vnds ?

Using what is in /dev is incorrect (always was) as /dev is just a
convention (and particularly is not reliable when chroots are in use).

  | this is a major behavior change, which may well break existing setups.

True, but there is little alternative, unless you'd like to return to
the pre cloning days.   It can stay as it is now, listing free devices
up to the highest used (but that really is hard to explain and makes
little sense, and as you have observed, is not very reliable) or I guess
we could just add a 

	for (n = highest_found; ++n < highest_found + 4; )
		printf("vnd%d: not in use\n", n);

after it finishes printing, just to list a few more free ones.

  | You remove existing and working functionality to fix a marginal backward
  | compatibility issue ?

Not marginal at all, and backwards compat has always been one of NetBSD's
prime objectives.

  | But removing this functionality is breaking
  | backward compat, in a much more important way.

Actually, I doubt it.  I suspect some other issue is the problem here,
and the change to vnconfig -l is just confusing the issue.

  | we *are* already running an up to date vnconfig, dammit !

Ah, OK, I misread your description (I thought you meant one from 7.0)

  | not until this problem is fixed. Breaking XEN3_DOM0 support is a real
  | problem.

Agreed, we need to work out what is causing that vnconfig to fail.

  | Unfortunably it's transient.

That does make it difficult to debug.

  | After a view vnconfig manipulations the
  | problem is gone for me (and vnconfig -l again show all devices,
  | used or free).

All 4 billion of them?

  | cd_ndevs is now at 8 (checked with gdb against /dev/mem)

Then at some stage you had vnd7 configured.

kre