Re: [PATCH 2/4] mm: memory_hotplug: check hwpoisoned page firstly in do_migrate_range()

[David Hildenbrand <david@redhat.com>]

>>
>> We're not checking the head page here, will this work reliably for
>> hugetlb? (I recall some difference in per-page hwpoison handling between
>> hugetlb and THP due to the vmemmap optimization)
> 
> Before this changes, the hwposioned hugetlb page won't try to unmap in
> do_migrate_range(), we hope it already unmapped in memory_failure(), as
> mentioned from comments, there maybe fail to unmap, so a new safeguard
> to try to unmap it again here, but we don't need to guarantee it.

Thanks for clarifying!

But I do wonder if the PageHWPoison() is the right thing to do for hugetlb.

IIUC, hugetlb requires folio_test_hwpoison() -- testing the head page 
not the subpage. Reason is that due to the vmemmap optimization we might 
not be able to modify subpages to set hwpoison.

-- 
Cheers,

David / dhildenb