linux-kernel - Re: [PATCH v3 0/3] Fix CONT-PTE/PMD size hugetlb issue when unmapping or migrating

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Message-ID: <0db300f4-8a91-b330-5c6f-bbc63cf2f151@linux.alibaba.com>
Date:   Tue, 10 May 2022 12:26:32 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     mike.kravetz@...cle.com, catalin.marinas@....com, will@...nel.org,
        songmuchun@...edance.com, tsbogend@...ha.franken.de,
        James.Bottomley@...senPartnership.com, deller@....de,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
        ysato@...rs.osdn.me, dalias@...c.org, davem@...emloft.net,
        arnd@...db.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 0/3] Fix CONT-PTE/PMD size hugetlb issue when unmapping
 or migrating



On 5/10/2022 12:04 PM, Andrew Morton wrote:
> On Tue, 10 May 2022 11:45:57 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:
> 
>> Hi,
>>
>> Now migrating a hugetlb page or unmapping a poisoned hugetlb page, we'll
>> use ptep_clear_flush() and set_pte_at() to nuke the page table entry
>> and remap it, and this is incorrect for CONT-PTE or CONT-PMD size hugetlb
>> page,
> 
> It would be helpful to describe why it's wrong.  Something like "should
> use huge_ptep_clear_flush() and huge_ptep_clear_flush() for this
> purpose"?

Sorry for the confusing description. I described the problem explicitly 
in each patch's commit message.

https://lore.kernel.org/all/ea5abf529f0997b5430961012bfda6166c1efc8c.1652147571.git.baolin.wang@linux.alibaba.com/
https://lore.kernel.org/all/730ea4b6d292f32fb10b7a4e87dad49b0eb30474.1652147571.git.baolin.wang@linux.alibaba.com/

> 
>> which will cause potential data consistent issue. This patch set
>> will change to use hugetlb related APIs to fix this issue, please find
>> details in each patch. Thanks.
> 
> Is a cc:stable needed here?  And are we able to identify a target for a
> Fixes: tag?

I think need a cc:stable tag, however I am not sure the target fixes 
tag, since we should trace back to the introduction of CONT-PTE/PMD 
hugetlb? 66b3923a1a0f ("arm64: hugetlb: add support for PTE contiguous bit")