[2/2] mm: Simplify PageDoubleMap with PF_SECOND policy

Commit Message

Matthew Wilcox June 29, 2020, 3:19 p.m. UTC

Introduce the new page policy of PF_SECOND which lets us use the
normal pageflags generation machinery to create the various DoubleMap
manipulation functions.

Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
---
 include/linux/page-flags.h | 40 ++++++++++----------------------------
 1 file changed, 10 insertions(+), 30 deletions(-)

Comments

Zi Yan June 29, 2020, 6:38 p.m. UTC | #1

On 29 Jun 2020, at 11:19, Matthew Wilcox (Oracle) wrote:

> Introduce the new page policy of PF_SECOND which lets us use the
> normal pageflags generation machinery to create the various DoubleMap
> manipulation functions.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
> ---
>  include/linux/page-flags.h | 40 ++++++++++----------------------------
>  1 file changed, 10 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index b4e6051aa311..7182103583d2 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -232,6 +232,9 @@ static inline void page_init_poison(struct page *page, size_t size)
>   *
>   * PF_NO_COMPOUND:
>   *     the page flag is not relevant for compound pages.
> + *
> + * PF_SECOND:
> + *     the page flag is stored in the first tail page.

Just wonder if PF_FIRST_TAIL_PAGE is more informative, although it has more characters to type. :)


—
Best Regards,
Yan Zi

Patch

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index b4e6051aa311..7182103583d2 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -232,6 +232,9 @@  static inline void page_init_poison(struct page *page, size_t size)
  *
  * PF_NO_COMPOUND:
  *     the page flag is not relevant for compound pages.
+ *
+ * PF_SECOND:
+ *     the page flag is stored in the first tail page.
  */
 #define PF_POISONED_CHECK(page) ({					\
 		VM_BUG_ON_PGFLAGS(PagePoisoned(page), page);		\
@@ -247,6 +250,9 @@  static inline void page_init_poison(struct page *page, size_t size)
 #define PF_NO_COMPOUND(page, enforce) ({				\
 		VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page);	\
 		PF_POISONED_CHECK(page); })
+#define PF_SECOND(page, enforce) ({					\
+		VM_BUG_ON_PGFLAGS(!PageHead(page), page);		\
+		PF_POISONED_CHECK(&page[1]); })
 
 /*
  * Macros to create function definitions for page flags
@@ -685,42 +691,15 @@  static inline int PageTransTail(struct page *page)
  *
  * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
  */
-static inline int PageDoubleMap(struct page *page)
-{
-	return PageHead(page) && test_bit(PG_double_map, &page[1].flags);
-}
-
-static inline void SetPageDoubleMap(struct page *page)
-{
-	VM_BUG_ON_PAGE(!PageHead(page), page);
-	set_bit(PG_double_map, &page[1].flags);
-}
-
-static inline void ClearPageDoubleMap(struct page *page)
-{
-	VM_BUG_ON_PAGE(!PageHead(page), page);
-	clear_bit(PG_double_map, &page[1].flags);
-}
-static inline int TestSetPageDoubleMap(struct page *page)
-{
-	VM_BUG_ON_PAGE(!PageHead(page), page);
-	return test_and_set_bit(PG_double_map, &page[1].flags);
-}
-
-static inline int TestClearPageDoubleMap(struct page *page)
-{
-	VM_BUG_ON_PAGE(!PageHead(page), page);
-	return test_and_clear_bit(PG_double_map, &page[1].flags);
-}
-
+PAGEFLAG(DoubleMap, double_map, PF_SECOND)
+	TESTSCFLAG(DoubleMap, double_map, PF_SECOND)
 #else
 TESTPAGEFLAG_FALSE(TransHuge)
 TESTPAGEFLAG_FALSE(TransCompound)
 TESTPAGEFLAG_FALSE(TransCompoundMap)
 TESTPAGEFLAG_FALSE(TransTail)
 PAGEFLAG_FALSE(DoubleMap)
-	TESTSETFLAG_FALSE(DoubleMap)
-	TESTCLEARFLAG_FALSE(DoubleMap)
+	TESTSCFLAG_FALSE(DoubleMap)
 #endif
 
 /*
@@ -885,6 +864,7 @@  static inline int page_has_private(struct page *page)
 #undef PF_ONLY_HEAD
 #undef PF_NO_TAIL
 #undef PF_NO_COMPOUND
+#undef PF_SECOND
 #endif /* !__GENERATING_BOUNDS_H */
 
 #endif	/* PAGE_FLAGS_H */