linux-kernel - [PATCH v2] LoongArch: Let {pte,pmd}_modify() record the status of _PAGE

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Message-ID: <20251107035805.3094024-1-zhangtianyang@loongson.cn>
Date: Fri,  7 Nov 2025 11:58:05 +0800
From: Tianyang Zhang <zhangtianyang@...ngson.cn>
To: chenhuacai@...nel.org,
	kernel@...0n.name,
	akpm@...ux-foundation.org,
	willy@...radead.org,
	david@...hat.com,
	linmag7@...il.com,
	thuth@...hat.com,
	maobibo@...ngson.cn,
	apopple@...dia.com
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Tianyang Zhang <zhangtianyang@...ngson.cn>,
	Liupu Wang <wangliupu@...ngson.cn>
Subject: [PATCH v2] LoongArch: Let {pte,pmd}_modify() record the status of _PAGE_DIRTY

Now, if the pte is dirty _PAGE_DIRTY but without _PAGE_MODIFIED, after
pte_modify() we lose _PAGE_DIRTY, then pte_dirty() returns false. So
we need _PAGE_MODIFIED to record _PAGE_DIRTY here.

The new modification involves checking whether the original PTE has the
_PAGE_DIRTY flag. If it exists, the _PAGE_MODIFIED bit is set, ensuring
that the pte_dirty interface can return accurate information.

Co-developed-by: Liupu Wang <wangliupu@...ngson.cn>
Signed-off-by: Liupu Wang <wangliupu@...ngson.cn>
Signed-off-by: Tianyang Zhang <zhangtianyang@...ngson.cn>
---
 arch/loongarch/include/asm/pgtable.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index bd128696e96d..e0b92fe850b3 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -424,6 +424,9 @@ static inline unsigned long pte_accessible(struct mm_struct *mm, pte_t a)
 
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
+	if (pte_val(pte) & _PAGE_DIRTY)
+		pte_val(pte) |= _PAGE_MODIFIED;
+
 	return __pte((pte_val(pte) & _PAGE_CHG_MASK) |
 		     (pgprot_val(newprot) & ~_PAGE_CHG_MASK));
 }
@@ -547,6 +550,9 @@ static inline struct page *pmd_page(pmd_t pmd)
 
 static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 {
+	if (pmd_val(pmd) & _PAGE_DIRTY)
+		pmd_val(pmd) |= _PAGE_MODIFIED;
+
 	pmd_val(pmd) = (pmd_val(pmd) & _HPAGE_CHG_MASK) |
 				(pgprot_val(newprot) & ~_HPAGE_CHG_MASK);
 	return pmd;
-- 
2.41.0