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

[Suren Baghdasaryan]

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 <sur...@google.com>
Acked-by: Michal Hocko <mho...@suse.com>
Acked-by: Mel Gorman <mgor...@techsingularity.net>
Acked-by: Mike Rapoport (IBM) <r...@kernel.org>
---
 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