mm: simplify PageDoubleMap with PF_SECOND policy

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Link: https://lkml.kernel.org/r/20200629151933.15671-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 76413b2..38ded40 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -235,6 +235,9 @@ 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);            \
@@ -250,6 +253,9 @@ 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
@@ -688,42 +694,15 @@ 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
 
 /*
@@ -888,6 +867,7 @@ 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 */