Re: [PATCH 3/3] mm,thp,rmap: clean up the end of __split_huge_pmd_locked()

[Kirill A. Shutemov]

On Fri, Nov 18, 2022 at 01:16:20AM -0800, Hugh Dickins wrote:
> It's hard to add a page_add_anon_rmap() into __split_huge_pmd_locked()'s
> HPAGE_PMD_NR set_pte_at() loop, without wincing at the "freeze" case's
> HPAGE_PMD_NR page_remove_rmap() loop below it.
> 
> It's just a mistake to add rmaps in the "freeze" (insert migration entries
> prior to splitting huge page) case: the pmd_migration case already avoids
> doing that, so just follow its lead.  page_add_ref() versus put_page()
> likewise.  But why is one more put_page() needed in the "freeze" case?
> Because it's removing the pmd rmap, already removed when pmd_migration
> (and freeze and pmd_migration are mutually exclusive cases).
> 
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>

Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov