linux-kernel - [RFC 3/8] mm: Avoid using set_page_count() in set_page

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Date:   Tue, 26 Oct 2021 17:38:17 +0000
From:   Pasha Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-m68k@...ts.linux-m68k.org,
        anshuman.khandual@....com, willy@...radead.org,
        akpm@...ux-foundation.org, william.kucharski@...cle.com,
        mike.kravetz@...cle.com, vbabka@...e.cz, geert@...ux-m68k.org,
        schmitzmic@...il.com, rostedt@...dmis.org, mingo@...hat.com,
        hannes@...xchg.org, guro@...com, songmuchun@...edance.com,
        weixugc@...gle.com, gthelen@...gle.com
Subject: [RFC 3/8] mm: Avoid using set_page_count() in set_page_recounted()

set_page_refcounted() converts a non-refcounted page that has
(page->_refcount == 0) into a refcounted page by setting _refcount to 1,

Use page_ref_inc_return() instead to avoid unconditionally overwriting
the _refcount value.

Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
---
 mm/internal.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index cf3cb933eba3..cf345fac6894 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -91,9 +91,12 @@ static inline bool page_evictable(struct page *page)
  */
 static inline void set_page_refcounted(struct page *page)
 {
+	int refcnt;
+
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	VM_BUG_ON_PAGE(page_ref_count(page), page);
-	set_page_count(page, 1);
+	refcnt = page_ref_inc_return(page);
+	VM_BUG_ON_PAGE(refcnt != 1, page);
 }
 
 extern unsigned long highest_memmap_pfn;
-- 
2.33.0.1079.g6e70778dc9-goog