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Write it as a macro definition to improve the readability and > maintainability of the code. > > Signed-off-by: Liu Ye > --- > include/linux/mm.h | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 7b1068ddcbb7..750e75f45557 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1098,6 +1098,8 @@ int vma_is_stack_for_current(struct vm_area_struct *vma); > struct mmu_gather; > struct inode; > > +#define FOLIO_ORDER(folio) ((folio)->_flags_1 & 0xff) This folio order calculation is only valid for !large folios. When it's a single page (not a large folio), the memory is interpreted as struct page. struct folio { ... union { struct { unsigned long _flags_1; unsigned long _head_1; /* public: */ atomic_t _large_mapcount; atomic_t _entire_mapcount; atomic_t _nr_pages_mapped; atomic_t _pincount; #ifdef CONFIG_64BIT unsigned int _folio_nr_pages; #endif /* private: the union with struct page is transitional */ }; struct page __page_1; }; ... } I feel this to be risky, considering someone may directly use FOLIO_ORDER() macro without folio_test_large() check. Correct macro should look like: #define FOLIO_ORDER(folio) (folio_test_large(folio) ? ((folio)->_flags_1 & 0xff) : 0) Thanks, Shivank > + > /* > * compound_order() can be called without holding a reference, which means > * that niceties like page_folio() don't work. These callers should be > @@ -1111,7 +1113,7 @@ static inline unsigned int compound_order(struct page *page) > > if (!test_bit(PG_head, &folio->flags)) > return 0; > - return folio->_flags_1 & 0xff; > + return FOLIO_ORDER(folio); > } > > /** > @@ -1127,7 +1129,7 @@ static inline unsigned int folio_order(const struct folio *folio) > { > if (!folio_test_large(folio)) > return 0; > - return folio->_flags_1 & 0xff; > + return FOLIO_ORDER(folio); > } > > #include > @@ -2061,7 +2063,7 @@ static inline long folio_nr_pages(const struct folio *folio) > #ifdef CONFIG_64BIT > return folio->_folio_nr_pages; > #else > - return 1L << (folio->_flags_1 & 0xff); > + return 1L << FOLIO_ORDER(folio); > #endif > } > > @@ -2086,7 +2088,7 @@ static inline unsigned long compound_nr(struct page *page) > #ifdef CONFIG_64BIT > return folio->_folio_nr_pages; > #else > - return 1L << (folio->_flags_1 & 0xff); > + return 1L << FOLIO_ORDER(folio); > #endif > } >