[PATCH] Loongarch:Make pte/pmd_modify can set _PAGE_MODIFIED

[Tianyang Zhang]

In the current pte_modify operation, _PAGE_DIRTY might be cleared. Since
the hardware-page-walk does not have a predefined _PAGE_MODIFIED flag,
this could lead to loss of valid data in certain scenarios.

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@xxxxxxxxxxx>
Signed-off-by: Liupu Wang <wangliupu@xxxxxxxxxxx>
Signed-off-by: Tianyang Zhang <zhangtianyang@xxxxxxxxxxx>
---
 arch/loongarch/include/asm/pgtable.h | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index bd128696e96d..106abfa5183b 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -424,8 +424,13 @@ 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)
 {
-	return __pte((pte_val(pte) & _PAGE_CHG_MASK) |
-		     (pgprot_val(newprot) & ~_PAGE_CHG_MASK));
+	unsigned long val = (pte_val(pte) & _PAGE_CHG_MASK) |
+		     (pgprot_val(newprot) & ~_PAGE_CHG_MASK);
+
+	if (pte_val(pte) & _PAGE_DIRTY)
+		val |= _PAGE_MODIFIED;
+
+	return __pte(val);
 }
 
 extern void __update_tlb(struct vm_area_struct *vma,
@@ -547,9 +552,13 @@ static inline struct page *pmd_page(pmd_t pmd)
 
 static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 {
-	pmd_val(pmd) = (pmd_val(pmd) & _HPAGE_CHG_MASK) |
+	unsigned long val = (pmd_val(pmd) & _HPAGE_CHG_MASK) |
 				(pgprot_val(newprot) & ~_HPAGE_CHG_MASK);
-	return pmd;
+
+	if (pmd_val(pmd) & _PAGE_DIRTY)
+		val |= _PAGE_MODIFIED;
+
+	return __pmd(val);
 }
 
 static inline pmd_t pmd_mkinvalid(pmd_t pmd)
-- 
2.41.0