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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