[PATCH v4 02/36] mm: Simplify PageDoubleMap with PF_SECOND policy

Matthew Wilcox
2020-05-15T13:17:32Z

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) <willy@infradead.org>
---
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 de6e0696f55c..979460df4768 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

/*
@@ -875,6 +854,7 @@ 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 */
--
2.26.2