Messages in this thread |  | | Date | Tue, 2 Sep 2025 19:59:49 +0000 | | From | Wei Yang <> | | Subject | Re: [PATCH v2 1/2] selftests/mm: split_huge_page_test: fix occasional is_backed_by_folio() wrong results |
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On Tue, Sep 02, 2025 at 06:25:35PM +0200, David Hildenbrand wrote: >When checking for actual tail or head pages of a folio, we must make >sure that the KPF_COMPOUND_HEAD/KPF_COMPOUND_TAIL flag is paired with >KPF_THP. > >For example, if we have another large folio after our large folio in >physical memory, our "pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL" would ^ One nit here, we missed )
>trigger even though it's actually a head page of the next folio. > >If is_backed_by_folio() returns a wrong result, split_pte_mapped_thp() >can fail with "Some THPs are missing during mremap". > >Fix it by checking for head/tail pages of folios properly. Add >folio_tail_flags/folio_head_flags to improve readability and use these >masks also when just testing for any compound page. > >Fixes: 169b456b0162 ("selftests/mm: reimplement is_backed_by_thp() with more precise check") >Signed-off-by: David Hildenbrand <david@redhat.com>
Otherwise,
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
-- Wei Yang Help you, Help me
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