[PATCH V3 4/5] mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Architectures like ppc64 requires to do a conditional tlb flush based on the old
and new value of pte. Follow the regular pte change protection sequence for
hugetlb too. This allow the architectures to override the update sequence.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 include/linux/hugetlb.h | 20 ++++++++++++++++++++
 mm/hugetlb.c            |  8 +++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 087fd5f48c91..39e78b80375c 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -543,6 +543,26 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
 	set_huge_pte_at(mm, addr, ptep, pte);
 }
 #endif
+
+#ifndef huge_ptep_modify_prot_start
+#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start
+static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep)
+{
+	return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
+}
+#endif
+
+#ifndef huge_ptep_modify_prot_commit
+#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit
+static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+						unsigned long addr, pte_t *ptep,
+						pte_t old_pte, pte_t pte)
+{
+	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
+#endif
+
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 #define alloc_huge_page(v, a, r) NULL
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 705a3e9cc910..353bff385595 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4388,10 +4388,12 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 			continue;
 		}
 		if (!huge_pte_none(pte)) {
-			pte = huge_ptep_get_and_clear(mm, address, ptep);
-			pte = pte_mkhuge(huge_pte_modify(pte, newprot));
+			pte_t old_pte;
+
+			old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
+			pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
 			pte = arch_make_huge_pte(pte, vma, NULL, 0);
-			set_huge_pte_at(mm, address, ptep, pte);
+			huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
 			pages++;
 		}
 		spin_unlock(ptl);
-- 
2.19.2