Re: grub2 mdadm and default_layout , attempt to read or write outside of disk

[Andrei Borzenkov]

On 04.06.2022 14:25, Darko Luketic wrote:
> Hello,
> 
> I have made a forum post at 
> https://bbs.archlinux.org/viewtopic.php?id=276955 if you'd like to read 
> that, but I'll repeat here.
> 
> Essentially, I'm getting a
> 
> |attempt to read or write outside of disk 'hd1'.|
> ||
> ||when trying to 'linux /boot/the-kernel with-params...'
> 
> I have tried:
> mdadm --stop /dev/md0
> mdadm --assemble -U layout-alternate /dev/md0 /dev/sda2 /dev/sdb1
> sure enough when checked with mdadm --detail it shows "layout: alternate"
> 
> But I'm guessing grub2 is trying to read hd1, whatever hd1 may be.
> 
> I have an external SSD drive via USB, when it's plugged in the error 
> message reads 'hd1', when not it's 'hd0'.
> 
> fsck.ext4 returns no errors.
> 
> doing ls in grub cli when about to boot shows (md/0) (hd0) (hd1) etc...
> 
> A loss of the rootfs would be catastrophic as I've left my usual 
> residence and am in a different country and all the vpn info is there, 
> and hell I really don't have the time to reinstall and reconfigure the 
> system.
> Lucky /home is separate. I could probably create a /boot partition on 
> the Windows drive (dual-booting) and that's probably what I'll do, 
> because I need to work and I need to access my home network,
> but it worked before, why doesn't it now?
> 
> I would post the grub.cfg but Windows 10 can't read ext4 by default, 
> afaik. But nothing really changed.
> My guess is grub can't deal with mdadm's layout-original or 
> layout-alternate or layout-unspecified.
> 

Currently grub does not support RAID0 with different member disk sizes
which makes RAID0 layout irrelevant at all for now.

> What can I do to solve the problem?
> 

Implement it or find someone who can implement it. At least make bug
report upstream and may be in your distribution bug tracker, whoever is
first :)

Implementation looks more or less straightforward. Instead of using one
single RAID0 segment for the whole array grub should build a list of
segments if raid disks are of different sizes. And of course adjust
mapping between logical and physical sectors depending on current layout.

> Thanks in advance for eventual responses, please also reply directly as 
> I'm not subscribed to the mailing list.
> 
> - Darko