linux-kernel - [PATCH] hugetlb: remove unnecessary set_page_count in prep_compound_gigantic

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Date:   Tue, 26 Oct 2021 15:06:35 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Matthew Wilcox <willy@...radead.org>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Subject: [PATCH] hugetlb: remove unnecessary set_page_count in prep_compound_gigantic_page

In commit 7118fc2906e29 ("hugetlb: address ref count racing in
prep_compound_gigantic_page"), page_ref_freeze is used to atomically
zero the ref count of tail pages iff they are 1.  The unconditional
call to set_page_count(0) was left in the code.  This call is after
page_ref_freeze so it is really a noop.

Remove redundant and unnecessary set_page_count call.

Fixes: 7118fc2906e29 ("hugetlb: address ref count racing in prep_compound_gigantic_page")
Suggested-by: Pasha Tatashin <pasha.tatashin@...een.com>
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/hugetlb.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 906fe8a3b93d..88047a367080 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1795,7 +1795,6 @@ static bool __prep_compound_gigantic_page(struct page *page, unsigned int order,
 		} else {
 			VM_BUG_ON_PAGE(page_count(p), p);
 		}
-		set_page_count(p, 0);
 		set_compound_head(p, page);
 	}
 	atomic_set(compound_mapcount_ptr(page), -1);
-- 
2.31.1