linux-kernel - [PATCH] mm/damon: Use set_huge_pte

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Message-Id: <1655692482-28797-1-git-send-email-baolin.wang@linux.alibaba.com>
Date:   Mon, 20 Jun 2022 10:34:42 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     sj@...nel.org, akpm@...ux-foundation.org
Cc:     mike.kravetz@...cle.com, songmuchun@...edance.com,
        baolin.wang@...ux.alibaba.com, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mm/damon: Use set_huge_pte_at() to make huge pte old

The huge_ptep_set_access_flags() can not make the huge pte old according
to the discussion [1], that means we will always mornitor the young state
of the hugetlb though we stopped accessing the hugetlb, as a result DAMON
will get inaccurate accessing statistics.

So changing to use set_huge_pte_at() to make the huge pte old to fix this
issue.

[1] https://lore.kernel.org/all/Yqy97gXI4Nqb7dYo@arm.com/

Fixes: 49f4203aae06 ("mm/damon: add access checking for hugetlb pages")
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 mm/damon/vaddr.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 5767be72c181..d24148a8149f 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -337,8 +337,7 @@ static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
 	if (pte_young(entry)) {
 		referenced = true;
 		entry = pte_mkold(entry);
-		huge_ptep_set_access_flags(vma, addr, pte, entry,
-					   vma->vm_flags & VM_WRITE);
+		set_huge_pte_at(mm, addr, pte, entry);
 	}
 
 #ifdef CONFIG_MMU_NOTIFIER
-- 
2.27.0