RE: [PATCH 1/1] mm: prevent poison consumption when splitting THP

[Zhuo, Qiuxu]

Hi Miaohe,

> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> [...]
> >>   First Machine Check occurs // [1]
> >>     memory_failure()         // [2]
> >>       try_to_split_thp_page()
> >>         split_huge_page()
> >>           split_huge_page_to_list_to_order()
> >>             __folio_split()  // [3]
> >>               remap_page()
> >>                 remove_migration_ptes()
> >>                   remove_migration_pte()
> >>                     try_to_map_unused_to_zeropage()
> >
> > Just an observation: Unfortunately THP only has PageHasHWPoisoned and
> > don't know the exact HWPoisoned page. Otherwise, we may still use
> > zeropage for these not HWPoisoned.
> 
> IIUC, the raw error page will have HWPoisoned flag set while the THP has
> PageHasHWPoisoned set. So I think we could use zeropage for healthy sub-
> pages.

Good point. 

David's suggested diff in another e-mail checked the raw error page instead of
entire folio. And I tested that diff and it worked well.  

-Qiuxu