Re: GRUB bug with Btrfs multiple devices

[Chris Murphy <lists@colorremedies.com>]

On Sat, Nov 30, 2019 at 10:02 AM Andrei Borzenkov <arvidjaar@gmail.com> wrote:
>
> GRUB is normally using hints - grub-install (and grub-mkconfig) tries to
> guess firmware device name. At boot time grub tries to access hinted
> device first, if it succeeds, it does not try anything else. With second
> btrfs partition grub needs to find second device at boot time so it now
> probes everything and hits those vendor media devices.
>
> At least this explains what you see as well as ...
>
> > Last time this
> > happened, all I did was remove the 2nd device and the problem went
> > away.
>
> ... this.

Ahhh, that makes complete sense. So it is Btrfs multiple device
related, but not a bug in btrfs.c per se.

>
> If you go in grub shell in this state (without errors), do you see those
> ghost devices?

Uncertain. My vague memory recall is that yes they are there, because
I found their existence strange and different compared to pre-GRUB
2.02 where on this same system I'd see only either hd0 or hd1 (one
without the other), along with cd0. But something changed either with
a firmware update from Apple, or GRUB, that resulted in additional
GRUB devices, hd2, hd3, hd4, hd5.

> > I'm ready to try that again (remove the 2nd device) and see if
> > the problem goes away, but has enough information been collected about
> > the present state?
> >
> >
>
> If you are reasonably sure that all errors are related to those phantom
> devices - I would say yes, the reason for these phantom devices to exist
> is already clear.

I'll give it a shot in a bit.


-- 
Chris Murphy