[PATCH 1/2] mm: add helpers pmdp_modify_prot_start/commit

[Xuefeng Wang <wxf.wang@xxxxxxxxxxxxx>]

Introduce helpers pmdp_modify_prot_start/commit to abstract pmdp_modify_prot
transaction. Helpers pmdp_modify_prot_start/commit are functionally unchanged.

Signed-off-by: Xuefeng Wang <wxf.wang@xxxxxxxxxxxxx>
Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
---
 include/asm-generic/pgtable.h | 35 +++++++++++++++++++++++++++++++++++
 mm/huge_memory.c              | 19 ++++++++-----------
 2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 798ea36a0549..e81bd58a9170 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -673,6 +673,41 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
 	__ptep_modify_prot_commit(vma, addr, ptep, pte);
 }
 #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
+
+static inline pmd_t __pmdp_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr,
+						pmd_t *pmdp)
+{
+	return pmdp_invalidate(vma, addr, pmdp);
+}
+
+static inline void __pmdp_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr,
+						pmd_t *pmdp, pmd_t pmd)
+{
+	set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#ifndef __HAVE_ARCH_PMDP_MODIFY_PROT_TRANSACTION
+static inline pmd_t pmdp_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr,
+						pmd_t *pmdp)
+{
+	__pmdp_modify_prot_start(vma, addr, pmdp);
+}
+#endif /* __HAVE_ARCH_PMDP_MODIFY_PROT_TRANSACTION */
+
+/*
+ * Commit an update to a pmd.
+ */
+static inline void pmdp_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr,
+						pmd_t *pmdp, pmd_t old_pmd, pmd_t pmd)
+{
+	__pmdp_modify_prot_commit(vma, addr, pmdp, pmd);
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif /* CONFIG_MMU */
 
 /*
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a88093213674..53515a3c91dd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1933,9 +1933,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long addr, pgprot_t newprot, int prot_numa)
 {
-	struct mm_struct *mm = vma->vm_mm;
 	spinlock_t *ptl;
-	pmd_t entry;
+	pmd_t pmdnt, oldpmd;
 	bool preserve_write;
 	int ret;
 
@@ -1961,7 +1960,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			newpmd = swp_entry_to_pmd(entry);
 			if (pmd_swp_soft_dirty(*pmd))
 				newpmd = pmd_swp_mksoft_dirty(newpmd);
-			set_pmd_at(mm, addr, pmd, newpmd);
+			set_pmd_at(vma->vm_mm, addr, pmd, newpmd);
 		}
 		goto unlock;
 	}
@@ -1995,18 +1994,16 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 	 *
 	 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
 	 * which may break userspace.
-	 *
-	 * pmdp_invalidate() is required to make sure we don't miss
-	 * dirty/young flags set by hardware.
 	 */
-	entry = pmdp_invalidate(vma, addr, pmd);
 
-	entry = pmd_modify(entry, newprot);
+	oldpmd = pmdp_modify_prot_start(vma, addr, pmd);
+	pmdnt = pmd_modify(oldpmd, newprot);
 	if (preserve_write)
-		entry = pmd_mk_savedwrite(entry);
+		pmdnt = pmd_mk_savedwrite(pmdnt);
+	pmdp_modify_prot_commit(vma, addr, pmd, oldpmd, pmdnt);
+
 	ret = HPAGE_PMD_NR;
-	set_pmd_at(mm, addr, pmd, entry);
-	BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
+	BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(pmdnt));
 unlock:
 	spin_unlock(ptl);
 	return ret;
-- 
2.17.1