Re: [btrfs] commit bc27d6f0aa0e4de184b617aceeaf25818cc646de breaks update-grub

["Linux regression tracking (Thorsten Leemhuis)" <regressions@leemhuis.info>]

Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
for once, to make this easily accessible to everyone.

Anand, what's the status wrt to below issue (which afaics seems to
affect quite a few people)? Things look stalled, but I might be missing
something, that's why I ask for a quick update.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

#regzbot poke

On 12.01.24 00:24, Anand Jain wrote:
> On 11/01/2024 22:36, David Sterba wrote:
>> On Thu, Jan 11, 2024 at 04:50:56PM +0100, David Sterba wrote:
>>> On Thu, Jan 11, 2024 at 12:45:50PM +0100, Thorsten Leemhuis wrote:
>>>>
>>>> On 08.01.24 15:11, Alex Romosan wrote:
>>>>>
>>>>> Running my own compiled kernel without initramfs on a lenovo thinkpad
>>>>> x1 carbon gen 7.
>>>>>
>>>>> Since version 6.7-rc1 i haven't been able to to a grub-update,
>>>>>
>>>>> instead i get this error:
>>>>>
>>>>> grub-probe: error: cannot find a device for / (is /dev mounted?) solid
>>>>> state drive
>>>>>
>>>>> 6.6 was the last version that worked.
>>>>>
>>>>> Today I did a git-bisect between these two versions which identified
>>>>> commit bc27d6f0aa0e4de184b617aceeaf25818cc646de btrfs: scan but don't
>>>>> register device on single device filesystem as the culprit. reverting
>>>>> this commit from 6.7 final allowed me to run update-grub again.
>>>>>
>>>>> not sure if this is the intended behavior or if i'm missing some other
>>>>> kernel options. any help/fixes would be appreciated.
>>>>
>>>> Thanks for the report. To be sure the issue doesn't fall through the
>>>> cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
>>>> tracking bot:
>>>>
>>>> #regzbot ^introduced bc27d6f0aa0e4de184b617aceeaf25818cc646de
>>>> #regzbot title btrfs: update-grub broken (cannot find a device for /
>>>> (is
>>>> /dev mounted?))
>>>> #regzbot ignore-activity
>>>
>>> The bug is also tracked at
>>> https://bugzilla.kernel.org/show_bug.cgi?id=218353 .
>>
>> About the fix: we can't simply revert the patch because the temp_fsid
>> depends on that. A workaround could be to check if the device path is
>> "/dev/root" and still register the device. But I'm not sure if this does
>> not break the use case that Steamdeck needs, as it's for the root
>> partition.
> 
> 
> Thank you for the report.
> 
> The issue seems more complex than a simple scenario, as the following
> test-case works well:
> 
>   $ mount /dev/sdb1 /btrfs
>   $ cat /proc/self/mountinfo | grep btrfs
> 345 63 0:34 / /btrfs rw,relatime shared:179 - btrfs /dev/sdb1
> rw,space_cache=v2,subvolid=5,subvol=/
> 
> However, the relevant part of the commit
> bc27d6f0aa0e4de184b617aceeaf25818cc646de that may be failing could
> be in identifying a device, whether it is the same or different
> For this, we use:
> 
>      lookup_bdev(path, &path_devt);
> 
> and match with the devt(MAJ:MIN) saved in the btrfs_device;
> would this work during initrd? I need to dig more. Trying
> to figure out how can I reproduce this.
> 
> Thanks, Anand
> 
>