Re: [PATCH] mm: hugepage: mark splitted page dirty when needed

[Zi Yan]

On 4 Sep 2018, at 4:01, Kirill A. Shutemov wrote:

> On Tue, Sep 04, 2018 at 03:55:10PM +0800, Peter Xu wrote:
>> When splitting a huge page, we should set all small pages as dirty if
>> the original huge page has the dirty bit set before.  Otherwise we'll
>> lose the original dirty bit.
>
> We don't lose it. It got transfered to struct page flag:
>
> 	if (pmd_dirty(old_pmd))
> 		SetPageDirty(page);
>

Plus, when split_huge_page_to_list() splits a THP, its subroutine __split_huge_page()
propagates the dirty bit in the head page flag to all subpages in __split_huge_page_tail().

--
Best Regards
Yan Zi

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