Re: [PATCH] Revert "mm: fix MAX_FOLIO_ORDER on powerpc configs with hugetlb"

["Christophe Leroy (CS GROUP)" <chleroy@kernel.org>]

Le 05/12/2025 à 08:05, David Hildenbrand (Red Hat) a écrit :
>>> 39231e8d6ba7 simply shuffles ifdefs and Kconfig items, so I assume it
>>> exposed a pre-existing bug.
>>>
>>> Reverting 39231e8d6ba7 will re-hide that bug.
>>
>> Shuah confirmed that the bugs were on v6.18-rc6 and they were fixed in
>> 6.18 [1].
>>
>> I verified that reverting 39231e8d6ba7 from v6.18-rc6 does not solve
>> anything, but applying 5bebe8de19264 does [2].
>>
> 
> Thanks!
> 
>> So reverting 39231e8d6ba7 does not change anything and there is no bug it
>> hides. The bug was introduced by adfb6609c680 ("mm/huge_memory: 
>> initialise
>> the tags of the huge zero folio"), was fixed by 5bebe8de1926
>> ("mm/huge_memory: Fix initialization of huge zero folio") ...
>>
>>> And that isn't a bad thing.  If we re-hide the bug in 6.18.x and in
>>> mainline then that relieves the people who are hitting this and it
>>> takes the pressure off David, Mike and yourself to get the underlying
>>> bug fixed in a hurry.
>>>
>>> So I think I'll queue this as a hotfix, plan to send it Linuswards in a
>>> couple of days.
>>>
>>> Or Linus may choose to apply it directly or to do a local revert of
>>> 39231e8d6ba7.  But I don't see how a local revert will get communicated
>>> to the 6.18.x maintainers.
>>>
>>> David, Linus, opinions please?
>>>
>>>> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
>>>
>>> Let's have a cc:stable here, just to be sure.
>>
>> ... and we can skip all this hassle.
> 
> Yes.
> 
> Thinking about reverting arbitrary commits after Shuah clearly tested 
> something wrong is completely unreasonable.
> 

That irrelevant revert has already been applied on mm-hotfixes-unstable, 
see https://lore.kernel.org/all/20251204215938.750D3C4CEFB@smtp.kernel.org/

Andrew, could you please drop it ?

Thanks
Christophe