Re: GRUB bug with Btrfs multiple devices

From: Goffredo Baroncelli <kreijack@inwind.it>
To: Chris Murphy <lists@colorremedies.com>
Cc: Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: GRUB bug with Btrfs multiple devices
Date: Thu, 28 Nov 2019 18:58:12 +0100	[thread overview]
Message-ID: <69aaf772-9eb0-945a-5277-40895e6901de@inwind.it> (raw)
In-Reply-To: <CAJCQCtQF6xtBDWc+i3FezWZUqGsj8hJrAzYpWG+=huFkmOK==g@mail.gmail.com>

On 28/11/2019 01.42, Chris Murphy wrote:
> On Tue, Nov 26, 2019 at 11:07 PM Goffredo Baroncelli <kreijack@inwind.it> wrote:
>>
[...]
>> Could you enable the debug, doing
>>
>>          set pager=1
>>          set debug=all
> 
> I need to narrow the scope. Adding 'set debug=all', there's just way
> too much to video, minutes of pages just holding down space bar full
> time which is even too fast to video. There must be over 1000 pages, a
> tiny minority contain efidisk.c references, the vast majority are
> btrfs.c references. As many pages as there are, I was never able to
> stop right on a boundary between efidisk.c and btrfs.c. So I gave up
> on that approach.

If I remember correctly, in the previous email you reports that even a simple "ls" at the grub prompt raises an error.
So you could watch what happens when doing something simpler like "ls" or "ls (hd0)"

> 
> Since the errors happen with efidisk.c I've enabled 'set
> debug=efidisk' and captured 74 photos, available at the link below
> (they are in pager order)
> 
> 
> 
> It does seem that the errors only happen in efidisk.c and only when
> trying to read from what might be phantom devices; I do not know how a
> second device in a Btrfs volume triggers this though. There must be
> some interaction between efidisk.c and btrfs.c? The grubx64.efi,
> grubenv, grub.cfg, and grub modules are all on an HFS+ (no journal)
> file system acting as the EFI System partition (as is the default
> behavior in Fedora on Macs for many years now). Only vmlinuz and
> initramfs are on Btrfs. So I'm not really even sure why btrfs.c gets
> called before the GRUB menu is displayed.
> 
> I'll see about reproducing this with a VM using edk2 UEFI and two
> virtio devices, at least get to a cleaner environment so we're not
> confusing multiple system specific weird things. And I can also leave
> this particular Mac laptop as it is for further study.
> 
> 

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