linux-kernel - [PATCH RFC 6/6] mm/mm_init: initialize page->_mapcount directly in__init_single

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Date: Wed, 22 May 2024 23:03:41 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Mike Rapoport <rppt@...nel.org>,
	Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH RFC 6/6] mm/mm_init: initialize page->_mapcount directly in__init_single_page()

Let's simply reinitialize the page->_mapcount directly. We can now
get rid of page_mapcount_reset().

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/mm.h       | 5 -----
 include/linux/mm_types.h | 2 +-
 mm/mm_init.c             | 2 +-
 3 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 018e7c0265ca..3e1d3b0d545e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1206,11 +1206,6 @@ static inline int folio_entire_mapcount(const struct folio *folio)
 	return atomic_read(&folio->_entire_mapcount) + 1;
 }
 
-static inline void page_mapcount_reset(struct page *page)
-{
-	atomic_set(&(page)->_mapcount, -1);
-}
-
 /**
  * page_mapcount() - Number of times this precise page is mapped.
  * @page: The page.
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6dae8e15037b..c377c040f87d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -169,7 +169,7 @@ struct page {
 		 * See page-flags.h for a list of page types which are currently
 		 * stored here.
 		 *
-		 * Owners of typed folios may reuse the lower 16bit of the
+		 * Owners of typed folios may reuse the lower 16 bit of the
 		 * head page page_type field after setting the page type,
 		 * but must reset these 16 bit to -1 before clearing the
 		 * page type.
diff --git a/mm/mm_init.c b/mm/mm_init.c
index f72b852bd5b8..b4916751edce 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -568,7 +568,7 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	mm_zero_struct_page(page);
 	set_page_links(page, zone, nid, pfn);
 	init_page_count(page);
-	page_mapcount_reset(page);
+	atomic_set(&page->_mapcount, -1);
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
 
-- 
2.45.0