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From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     akpm@linux-foundation.org, tglx@linutronix.de,
        kirill.shutemov@linux.intel.com, mika.penttila@nextfour.com,
        david@redhat.com, jgg@nvidia.com
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, songmuchun@bytedance.com,
        zhouchengming@bytedance.com, Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH v3 08/15] mm/pte_ref: initialize the refcount of the withdrawn PTE page table page
Date:   Wed, 10 Nov 2021 16:40:50 +0800
Message-Id: <20211110084057.27676-9-zhengqi.arch@bytedance.com>
In-Reply-To: <20211110084057.27676-1-zhengqi.arch@bytedance.com>
References: <20211110084057.27676-1-zhengqi.arch@bytedance.com>
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When we split the PMD-mapped THP to the PTE-mapped THP, we should
initialize the refcount of the withdrawn PTE page table page to
HPAGE_PMD_NR, which ensures that we can release the PTE page table
page when it is free(the refcount is 0).

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/pgtable-generic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 4e640baf9794..523053e09dfa 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -186,6 +186,7 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 							  struct page, lru);
 	if (pmd_huge_pte(mm, pmdp))
 		list_del(&pgtable->lru);
+	pte_ref_init(pgtable, pmdp, HPAGE_PMD_NR);
 	return pgtable;
 }
 #endif
-- 
2.11.0