Messages in this thread Patch in this message | | | From | Sidhartha Kumar <> | Subject | [PATCH mm-unstable] mm: clarify folio_set_compound_order() zero support | Date | Wed, 7 Dec 2022 14:37:31 -0800 |
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Document hugetlb's use of a zero compound order so support for zero orders is not removed from folio_set_compound_order().
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com> Suggested-by: Mike Kravetz <mike.kravetz@oracle.com> Suggested-by: Muchun Song <songmuchun@bytedance.com> --- This can be folded into f2b67a51d0ef6871d4fb0c3e8199f278112bd108 mm: add folio dtor and order setter functions
include/linux/mm.h | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h index 443d496949a8..cd8508d728f1 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -999,9 +999,16 @@ static inline void set_compound_order(struct page *page, unsigned int order) #endif } +/* + * folio_set_compound_order is generally passed a non-zero order to + * initialize a large folio. However, hugetlb code abuses this by + * passing in zero when 'dissolving' a large folio. + */ static inline void folio_set_compound_order(struct folio *folio, unsigned int order) { + VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); + folio->_folio_order = order; #ifdef CONFIG_64BIT folio->_folio_nr_pages = order ? 1U << order : 0; -- 2.38.1
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