Re: [btrfs] commit bc27d6f0aa0e4de184b617aceeaf25818cc646de breaks update-grub

[Alex Romosan]

update-grub still doesn't work 6.8-rc1

so i did:

# cat /proc/self/mountinfo | grep btrfs
21 1 0:19 / / rw,relatime shared:1 - btrfs /dev/root
rw,ssd,discard=async,space_cache,subvolid=5,subvol=/

the difference from your test case is that it doesn't reference
the disk device but /dev/root which on my system doesn't exist. could this
be the problem?

--alex--


On Fri, Jan 12, 2024 at 12:24 AM Anand Jain <anand.jain@xxxxxxxxxx> 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:
> >>> [Adding Anand Jain, the author of the culprit to the list of recipients;
> >>> furthermore CCing the the Btrfs maintainers and the btrfs list; also
> >>> CCing regression list, as it should be in the loop for regressions:
> >>> https://docs.kernel.org/admin-guide/reporting-regressions.html]
> >>>
> >>> On 08.01.24 15:11, Alex Romosan wrote:
> >>>> Please Cc me as I am not subscribed to the list.
> >>>>
> >>>> 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.
> >>>>
> >>>> thank you.
> >>>
> >>> 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