linux-kernel - [PATCH] mm: hugetlb_vmemmap: use PageCompound() instead of PageReserved()

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Message-Id: <20230719063132.37676-1-songmuchun@bytedance.com>
Date:   Wed, 19 Jul 2023 14:31:31 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     mike.kravetz@...cle.com, muchun.song@...ux.dev,
        akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] mm: hugetlb_vmemmap: use PageCompound() instead of PageReserved()

The ckeck of PageReserved() is easy to be broken in the future, PageCompound()
is more stable to check if the page should be split.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/hugetlb_vmemmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 4b9734777f69..8068fe890f52 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -73,8 +73,10 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
 		 * be treated as indepdenent small pages (as they can be freed
 		 * individually).
 		 */
-		if (!PageReserved(head))
+		if (PageCompound(head)) {
+			VM_BUG_ON(compound_order(head) != get_order(PMD_SIZE));
 			split_page(head, get_order(PMD_SIZE));
+		}
 
 		/* Make pte visible before pmd. See comment in pmd_install(). */
 		smp_wmb();
-- 
2.11.0