[PATCH 14/28] mm: Convert page_mapcount() to use folio_entire_mapcount()

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-mm@kvack.org, Hugh Dickins <hughd@google.com>
Subject: [PATCH 14/28] mm: Convert page_mapcount() to use folio_entire_mapcount()
Date: Wed, 11 Jan 2023 14:29:00 +0000	[thread overview]
Message-ID: <20230111142915.1001531-15-willy@infradead.org> (raw)
In-Reply-To: <20230111142915.1001531-1-willy@infradead.org>

Remove a use of head_compound_mapcount().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/mm.h | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8bddc7810f78..554b73dae188 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -853,22 +853,26 @@ static inline void page_mapcount_reset(struct page *page)
 	atomic_set(&(page)->_mapcount, -1);
 }
 
-/*
- * Mapcount of 0-order page; when compound sub-page, includes
- * compound_mapcount of compound_head of page.
+/**
+ * page_mapcount() - Number of times this precise page is mapped.
+ * @page: The page.
+ *
+ * The number of times this page is mapped.  If this page is part of
+ * a large folio, it includes the number of times this page is mapped
+ * as part of that folio.
  *
- * Result is undefined for pages which cannot be mapped into userspace.
+ * The result is undefined for pages which cannot be mapped into userspace.
  * For example SLAB or special types of pages. See function page_has_type().
- * They use this place in struct page differently.
+ * They use this field in struct page differently.
  */
 static inline int page_mapcount(struct page *page)
 {
 	int mapcount = atomic_read(&page->_mapcount) + 1;
 
-	if (likely(!PageCompound(page)))
-		return mapcount;
-	page = compound_head(page);
-	return head_compound_mapcount(page) + mapcount;
+	if (unlikely(PageCompound(page)))
+		mapcount += folio_entire_mapcount(page_folio(page));
+
+	return mapcount;
 }
 
 int folio_total_mapcount(struct folio *folio);
-- 
2.35.1


