Subject: [PATCH v4 5/7] mm: replace vma->vm_flags indirect modification in ksm_madvise

From: Suren Baghdasaryan <[email-masked]>
Date: Thu, 26 Jan 2023 11:37:50 -0800

Replace indirect modifications to vma->vm_flags with calls to modifier
functions to be able to track flag changes and to keep vma locking
correctness.

Signed-off-by: Suren Baghdasaryan <[email-masked]>
Acked-by: Michal Hocko <[email-masked]>
Acked-by: Mel Gorman <[email-masked]>
Acked-by: Mike Rapoport (IBM) <[email-masked]>
---
 arch/powerpc/kvm/book3s_hv_uvmem.c | 6 +++++-
 arch/s390/mm/gmap.c                | 6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 1d67baa5557a..709ebd578394 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -393,6 +393,7 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm,
 {
 	unsigned long gfn = memslot->base_gfn;
 	unsigned long end, start = gfn_to_hva(kvm, gfn);
+	unsigned long vm_flags;
 	int ret = 0;
 	struct vm_area_struct *vma;
 	int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE;
@@ -409,12 +410,15 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm,
 			ret = H_STATE;
 			break;
 		}
+		/* Copy vm_flags to avoid partial modifications in ksm_madvise */
+		vm_flags = vma->vm_flags;
 		ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
-			  merge_flag, &vma->vm_flags);
+			  merge_flag, &vm_flags);
 		if (ret) {
 			ret = H_STATE;
 			break;
 		}
+		vm_flags_reset(vma, vm_flags);
 		start = vma->vm_end;
 	} while (end > vma->vm_end);
 
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index ab836597419d..5a716bdcba05 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2587,14 +2587,18 @@ int gmap_mark_unmergeable(void)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
+	unsigned long vm_flags;
 	int ret;
 	VMA_ITERATOR(vmi, mm, 0);
 
 	for_each_vma(vmi, vma) {
+		/* Copy vm_flags to avoid partial modifications in ksm_madvise */
+		vm_flags = vma->vm_flags;
 		ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
-				  MADV_UNMERGEABLE, &vma->vm_flags);
+				  MADV_UNMERGEABLE, &vm_flags);
 		if (ret)
 			return ret;
+		vm_flags_reset(vma, vm_flags);
 	}
 	mm->def_flags &= ~VM_MERGEABLE;
 	return 0;
-- 
2.39.1