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

Baolin Wang
2022-05-10T04:29:06Z

On 5/10/2022 12:04 PM, Andrew Morton wrote:
> On Tue, 10 May 2022 11:45:57 +0800 Baolin Wang <baolin.wang@linux.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")