Re: [REGRESSION] Chrome and VSCode breakage with the commit b9b588f22a0c

[Paul Menzel <pmenzel@molgen.mpg.de>]

Dear Chuck, dear Takashi, dear Christian,


I just came across this issue.

Am 29.03.25 um 15:57 schrieb Chuck Lever:
> On 3/29/25 8:17 AM, Takashi Iwai wrote:
>> On Sun, 23 Feb 2025 09:53:10 +0100, Takashi Iwai wrote:

>>> we received a bug report showing the regression on 6.13.1 kernel
>>> against 6.13.0.  The symptom is that Chrome and VSCode stopped working
>>> with Gnome Scaling, as reported on openSUSE Tumbleweed bug tracker
>>>    https://bugzilla.suse.com/show_bug.cgi?id=1236943
>>>
>>> Quoting from there:
>>> """
>>> I use the latest TW on Gnome with a 4K display and 150%
>>> scaling. Everything has been working fine, but recently both Chrome
>>> and VSCode (installed from official non-openSUSE channels) stopped
>>> working with Scaling.
>>> ....
>>> I am using VSCode with:
>>> `--enable-features=UseOzonePlatform --enable-features=WaylandWindowDecorations --ozone-platform-hint=auto` and for Chrome, I select `Preferred Ozone platform` == `Wayland`.
>>> """
>>>
>>> Surprisingly, the bisection pointed to the backport of the commit
>>> b9b588f22a0c049a14885399e27625635ae6ef91 ("libfs: Use d_children list
>>> to iterate simple_offset directories").
>>>
>>> Indeed, the revert of this patch on the latest 6.13.4 was confirmed to
>>> fix the issue.  Also, the reporter verified that the latest 6.14-rc
>>> release is still affected, too.
>>>
>>> For now I have no concrete idea how the patch could break the behavior
>>> of a graphical application like the above.  Let us know if you need
>>> something for debugging.  (Or at easiest, join to the bugzilla entry
>>> and ask there; or open another bug report at whatever you like.)
>>>
>>> BTW, I'll be traveling tomorrow, so my reply will be delayed.

>>> #regzbot introduced: b9b588f22a0c049a14885399e27625635ae6ef91
>>> #regzbot monitor: https://bugzilla.suse.com/show_bug.cgi?id=1236943
>>
>> After all, this seems to be a bug in Chrome and its variant, which was
>> surfaced by the kernel commit above: as the commit changes the
>> directory enumeration, it also changed the list order returned from
>> libdrm drmGetDevices2(), and it screwed up the application that worked
>> casually beforehand.  That said, the bug itself has been already
>> present.  The Chrome upstream tracker:
>>    https://issuetracker.google.com/issues/396434686
>>
>> #regzbot invalid: problem has always existed on Chrome and related code

> Thank you very much for your report and for chasing this to conclusion.
Doesn’t marking this an invalid contradict Linux’ no regression policy 
to never break user space, so users can always update the Linux kernel? 
Shouldn’t this commit still be reverted, and another way be found 
keeping the old ordering?

Greg, Sasha, in stable/linux-6.13.y the two commits below would need to 
be reverted:

180c7e44a18bbd7db89dfd7e7b58d920c44db0ca
d9da7a68a24518e93686d7ae48937187a80944ea

For stable/linux-6.12.y:

176d0333aae43bd0b6d116b1ff4b91e9a15f88ef
639b40424d17d9eb1d826d047ab871fe37897e76


Kind regards,

Paul