LoongArch: Set _PAGE_DIRTY only if _PAGE_MODIFIED is set in {pmd,pte}_mkwrite()

mainline inclusion
from mainline-v6.1-rc7
commit 54e6cd42
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7362E
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/arch/loongarch?id=54e6cd42a183b602e3627ad3aaeeed44f7443e67

--------------------------------

Set _PAGE_DIRTY only if _PAGE_MODIFIED is set in {pmd,pte}_mkwrite().
Otherwise, _PAGE_DIRTY silences the TLB modify exception and make us
have no chance to mark a pmd/pte dirty (_PAGE_MODIFIED) for software.
Reviewed-by: NGuo Ren <guoren@kernel.org>
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>
Change-Id: I05f95f28b6c2a18c44b41f253a2f4cbb987521b9
(cherry picked from commit df87bdf6)

arch/loongarch/include/asm/pgtable.h

@@ -369,7 +369,9 @@ static inline pte_t pte_mkdirty(pte_t pte)
 
 static inline pte_t pte_mkwrite(pte_t pte)
 {
-	pte_val(pte) |= (_PAGE_WRITE | _PAGE_DIRTY);
+	pte_val(pte) |= _PAGE_WRITE;
+	if (pte_val(pte) & _PAGE_MODIFIED)
+		pte_val(pte) |= _PAGE_DIRTY;
 	return pte;
 }
 
@@ -466,7 +468,9 @@ static inline int pmd_write(pmd_t pmd)
 
 static inline pmd_t pmd_mkwrite(pmd_t pmd)
 {
-	pmd_val(pmd) |= (_PAGE_WRITE | _PAGE_DIRTY);
+	pmd_val(pmd) |= _PAGE_WRITE;
+	if (pmd_val(pmd) & _PAGE_MODIFIED)
+		pmd_val(pmd) |= _PAGE_DIRTY;
 	return pmd;
 }