On 12/02/25 12:37 pm, liuye wrote:
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.
Well, then let us wait for that time to come :) Personally I am not a
fan of over-abstracting, especially when it is just a single line; one
benefit I have seen of writing the way it is written right now, is that
I actually get reminded where the folio order is actually stored. I have
no objection on getting this patch applied, if someone else thinks this
is a fruitful abstraction. In any case, you do need to come up with a
better name than FOLIO_ORDER, as it is confusing.
Thanks，
Liu Ye
