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Tue, 23 Dec 2025 05:48:20 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AD0D920043; Tue, 23 Dec 2025 05:48:20 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AD18A20040; Tue, 23 Dec 2025 05:48:16 +0000 (GMT) Received: from [9.124.209.226] (unknown [9.124.209.226]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 23 Dec 2025 05:48:16 +0000 (GMT) Message-ID: <972f7168-6dba-4a29-83e6-91f31355b90e@linux.ibm.com> Date: Tue, 23 Dec 2025 11:18:01 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] mm/hugetlb: ignore hugepage kernel args if hugepages are unsupported To: "Christophe Leroy (CS GROUP)" , "David Hildenbrand (Red Hat)" , "Ritesh Harjani (IBM)" , Andrew Morton Cc: Borislav Petkov , Heiko Carstens , Ingo Molnar , Madhavan Srinivasan , Michael Ellerman , Muchun Song , Oscar Salvador , Thomas Gleixner , Vasily Gorbik , linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, x86@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org References: <20251221053611.441251-1-sourabhjain@linux.ibm.com> <87a4zcml36.ritesh.list@gmail.com> <655cc605-2ce1-4ccb-8cc0-a0a31a9c89fd@kernel.org> <87fr93ky5i.ritesh.list@gmail.com> <16fef7a5-6853-4a6f-8d27-e005fa351eb7@linux.ibm.com> <051628be-ed70-4a56-8704-f2b8cdea1984@kernel.org> Content-Language: en-US From: Sourabh Jain In-Reply-To: Content-Type: text/plain; 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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@syzkaller.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 >     Signed-off-by: Jens Axboe Thanks for the suggestion Christophe. I will use Depends-on tag. - Sourabh Jain