[PATCH v2 02/20] mm: factor out large folio handling from folio_nr_pages() into folio_large_nr_pages()

[David Hildenbrand <david@xxxxxxxxxx>]

Let's factor it out into a simple helper function. This helper will
also come in handy when working with code where we know that our
folio is large.

While at it, let's consistently return a "long" value from all these
similar functions. Note that we cannot use "unsigned int" (even though
_folio_nr_pages is of that type), because it would break some callers
that do stuff like "-folio_nr_pages()". Both "int" or "unsigned long"
would work as well.

Maybe in the future we'll have the nr_pages readily available for all
large folios, maybe even for small folios, or maybe for none.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 include/linux/mm.h | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d00214e22a174..7c5a8fd29cfcd 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1199,6 +1199,18 @@ static inline unsigned int folio_large_order(const struct folio *folio)
 	return folio->_flags_1 & 0xff;
 }
 
+#ifdef CONFIG_64BIT
+static inline long folio_large_nr_pages(const struct folio *folio)
+{
+	return folio->_folio_nr_pages;
+}
+#else
+static inline long folio_large_nr_pages(const struct folio *folio)
+{
+	return 1L << folio_large_order(folio);
+}
+#endif
+
 /*
  * compound_order() can be called without holding a reference, which means
  * that niceties like page_folio() don't work.  These callers should be
@@ -2141,11 +2153,7 @@ static inline long folio_nr_pages(const struct folio *folio)
 {
 	if (!folio_test_large(folio))
 		return 1;
-#ifdef CONFIG_64BIT
-	return folio->_folio_nr_pages;
-#else
-	return 1L << folio_large_order(folio);
-#endif
+	return folio_large_nr_pages(folio);
 }
 
 /* Only hugetlbfs can allocate folios larger than MAX_ORDER */
@@ -2160,24 +2168,20 @@ static inline long folio_nr_pages(const struct folio *folio)
  * page.  compound_nr() can be called on a tail page, and is defined to
  * return 1 in that case.
  */
-static inline unsigned long compound_nr(struct page *page)
+static inline long compound_nr(struct page *page)
 {
 	struct folio *folio = (struct folio *)page;
 
 	if (!test_bit(PG_head, &folio->flags))
 		return 1;
-#ifdef CONFIG_64BIT
-	return folio->_folio_nr_pages;
-#else
-	return 1L << folio_large_order(folio);
-#endif
+	return folio_large_nr_pages(folio);
 }
 
 /**
  * thp_nr_pages - The number of regular pages in this huge page.
  * @page: The head page of a huge page.
  */
-static inline int thp_nr_pages(struct page *page)
+static inline long thp_nr_pages(struct page *page)
 {
 	return folio_nr_pages((struct folio *)page);
 }
-- 
2.48.1