mm: introduce page_mapcount_is_type()

Resolve the awkward "and add one to this opaque constant" test into a
self-documenting inline function.

Link: https://lkml.kernel.org/r/20240821173914.2270383-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 2515ae85f191..0b5484fdbca1 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -956,12 +956,18 @@ enum pagetype {
 #define folio_test_type(folio, flag)					\
 	((READ_ONCE(folio->page.page_type) & (PAGE_TYPE_BASE | flag))  == PAGE_TYPE_BASE)
 
-static inline int page_type_has_type(unsigned int page_type)
+static inline bool page_type_has_type(int page_type)
 {
-	return (int)page_type < PAGE_MAPCOUNT_RESERVE;
+	return page_type < PAGE_MAPCOUNT_RESERVE;
 }
 
-static inline int page_has_type(const struct page *page)
+/* This takes a mapcount which is one more than page->_mapcount */
+static inline bool page_mapcount_is_type(unsigned int mapcount)
+{
+	return page_type_has_type(mapcount - 1);
+}
+
+static inline bool page_has_type(const struct page *page)
 {
 	return page_type_has_type(READ_ONCE(page->page_type));
 }