Message-ID: <972f7168-6dba-4a29-83e6-91f31355b90e@linux.ibm.com>
Date: Tue, 23 Dec 2025 11:18:01 +0530
From: Sourabh Jain <sourabhjain@...ux.ibm.com>
To: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
        "David Hildenbrand (Red Hat)" <david@...nel.org>,
        "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc: Borislav Petkov <bp@...en8.de>, Heiko Carstens <hca@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        x86@...nel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] mm/hugetlb: ignore hugepage kernel args if hugepages
 are unsupported



On 22/12/25 16:24, Christophe Leroy (CS GROUP) wrote:
>
>
> Le 22/12/2025 à 11:28, David Hildenbrand (Red Hat) a écrit :
>> On 12/22/25 06:57, Sourabh Jain wrote:
>>>
>>>
>>> On 22/12/25 08:42, Ritesh Harjani (IBM) wrote:
>>>> "David Hildenbrand (Red Hat)" <david@...nel.org> writes:
>>>>
>>>>>> Coming back to the fixes tag. I did mention a bit of a history 
>>>>>> [2] of
>>>>>> whatever I could find while reviewing this patch. I am not sure 
>>>>>> whether
>>>>>> you have looked into the links shared in that email or not. Here 
>>>>>> [2]:
>>>>>>
>>>>>> [2]: https://eur01.safelinks.protection.outlook.com/? 
>>>>>> url=https%3A%2F%2Flore.kernel.org%2Flinuxppc- 
>>>>>> dev%2F875xa3ksz9.ritesh.list%40gmail.com%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cfe40f4881e8441ab3ebf08de4144e747%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639019961377096292%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Dnvzy5kJ%2ByF9GJjIw%2B12FTjaVgeAM2gA9g7hsYl7Qok%3D&reserved=0
>>>>>>
>>>>>> Where I am coming from is.. The current patch is acutally a partial
>>>>>> revert of the patch mentioned in the fixes tag. That means if 
>>>>>> this patch
>>>>>> gets applied to the older stable kernels, it would end up 
>>>>>> bringing the
>>>>>> same problem back, which the "Fixes" tagged patch is fixing in 
>>>>>> the 1st
>>>>>> place, isnt' it? See this discussion [3]...
>>>>>>
>>>>>> [3]: https://eur01.safelinks.protection.outlook.com/? 
>>>>>> url=https%3A%2F%2Flore.kernel.org%2Fall%2Fb1f04f9f-fa46- 
>>>>>> c2a0-7693-4a0679d2a1ee%40oracle.com%2FT%2F%23m0eee87b458d93559426b8b0e78dc6ebcd26ad3ae&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cfe40f4881e8441ab3ebf08de4144e747%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639019961377117150%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=bOO7FGN4jAtX3jjBnJVpSurmM9rGmz8vIs1iGtbm1gU%3D&reserved=0 
>>>>>>
>>>>>>
>>>>>> ... So, IMO - the right fixes tag, if we have to add, it should 
>>>>>> be the
>>>>>> patch which moved the hpage_shift initialization to happen early 
>>>>>> i.e. in
>>>>>> mmu_early_init_devtree. That would be this patch [4]:
>>>>>>
>>>>>> [4]: https://eur01.safelinks.protection.outlook.com/? 
>>>>>> url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3D2354ad252b66695be02f4acd18e37bf6264f0464&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cfe40f4881e8441ab3ebf08de4144e747%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639019961377133860%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=0yTuECy%2BBGDLiSNYuqYH9xGBOSxiRLxAtW%2FWTQU%2FB%2BA%3D&reserved=0
>>>>>>
>>>>>> Now, it's not really that the patch [4] had any issue as such. 
>>>>>> But it
>>>>>> seems like, that the current fix can only be applied after patch 
>>>>>> [4] is
>>>>>> taken.
>>>>>>
>>>>>> Do we agree?
>>>>> I think we should document all that in the cover letter, an describe
>>>>> that this partial revert is only possible after [4],
>>>> Yes, I agree. Let's add the above details in the commit msg.
>>>>
>>>>> and that that must
>>>>> be considered when attempting any kind of stable backports.
>>>> Sure. I would prefer if we change the Fixes tag to the one which I
>>>> pointed in above [4] (with explaination in the commit msg). However 
>>>> I am
>>>> still ok if we would like to retain the existing fixes tag and show 
>>>> [4]
>>>> as a dependency.
>>>
>>> I think we should keep the current Fixes tag with an explanation for
>>> dependency
>>> on [1] in the commit message.
>>>
>>> Would anyone have a different view?
>>
>> Whatever introduced the issue should be called out in the Fixes tag; 
>> if there are dependencies for the fix through other patches that were 
>> already merged, that can be documented in the patch description 
>> (relevant for stable or distro backports only).
>>
>
> We can also use the Depends-on: tag, see for exemple commit 
> 9517b82d8d42 ("nbd: defer config put in recv_work"):
>
>     Reported-by: syzbot+56fbf4c7ddf65e95c7cc@...kaller.appspotmail.com
>     Closes: 
> https://lore.kernel.org/all/6907edce.a70a0220.37351b.0014.GAE@google.com/T/
>     Fixes: 87aac3a80af5 ("nbd: make the config put is called before 
> the notifying the waiter")
>     Depends-on: e2daec488c57 ("nbd: Fix hungtask when nbd_config_put")
>     Signed-off-by: Zheng Qixing <zhengqixing@...wei.com>
>     Signed-off-by: Jens Axboe <axboe@...nel.dk>

Thanks for the suggestion Christophe. I will use Depends-on tag.

- Sourabh Jain

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