在 2025/2/12 13:12, Dev Jain 写道:
>
>
> On 12/02/25 8:28 am, Liu Ye wrote:
>> There are multiple locations in mm.h where (folio->_flags_1 & 0xff) is
>> used. Write it as a macro definition to improve the readability and
>> maintainability of the code.
>>
>> Signed-off-by: Liu Ye <liuye@xxxxxxxxxx>
>> ---
>> 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)
>> +
>> /*
>> * 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 <linux/huge_mm.h>
>> @@ -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
>> }
>>
>
> Personally I do not think this is improving readability. You are introducing one more macro for people to decipher instead of directly seeing folio->_flags_1 & 0xff. This is similar to whether to write
> if (x) => do_stuff(), or if (x != 0) => do_stuff(). The former is more "readable" by convention but the latter makes it easier and obvious to understand.
>
Or simply for maintenance purposes, if the meaning of a bit changes, only the macro definition needs to be modified.
Thanks，
Liu Ye
