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SubjectRe: [PATCH] mm/khugepaged: Fix ->anon_vma race
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On 24.01.23 01:51, Kirill A. Shutemov wrote:
> On Mon, Jan 23, 2023 at 12:07:05PM +0100, David Hildenbrand wrote:
>>>> commit bedf03416913d88c796288f9dca109a53608c745
>>>> Author: Yang Shi <shy828301@gmail.com>
>>>> Date: Wed Sep 7 11:01:44 2022 -0700
>>>>
>>>> powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush
>>>> The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will
>>>> move to use RCU instead of disabling local interrupts in fast-GUP. Using
>>>> an IPI is the old-styled way of serializing against fast-GUP although it
>>>> still works as expected now.
>>>> And fast-GUP now fixed the potential race with THP collapse by checking
>>>> whether PMD is changed or not. So IPI broadcast in radix pmd collapse
>>>> flush is not necessary anymore. But it is still needed for hash TLB.
>>>
>>> Okay. But I think tlb_remove_table_sync_one() belongs inside
>>> pmdp_collapse_flush(). Collapsing pmd table into huge page without
>>> serialization is a bug. They should not be separate.
>>
>> Agreed. But I wonder if it should be moved into a generic
>> pmdp_collapse_flush(), that calls an arch specific __pmdp_collapse_flush().
>
> Um? There's no __pmdp_collapse_flush().

Did I imply that there is already one? ;)

--
Thanks,

David / dhildenb

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