Preparation. Add the new simple helper, vma_is_anonymous(vma),
and change handle_pte_fault() to use it. It will have more users.

The name is not very accurate, say mmap_mem/VM_PFNMAP vma is not
anonymous. Perhaps it should be named vma_has_fault() instead.
But it matches the logic in mmap.c/memory.c, see next changes.

Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
 include/linux/mm.h |    5 +++++
 mm/memory.c        |   13 ++++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0755b9f..a0fe3d3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1225,6 +1225,11 @@ static inline int vma_growsdown(struct vm_area_struct 
*vma, unsigned long addr)
        return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
 }
 
+static inline bool vma_is_anonymous(struct vm_area_struct *vma)
+{
+       return !vma->vm_ops || !vma->vm_ops->fault;
+}
+
 static inline int stack_guard_page_start(struct vm_area_struct *vma,
                                             unsigned long addr)
 {
diff --git a/mm/memory.c b/mm/memory.c
index 22e037e..f50ed81 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3242,13 +3242,12 @@ static int handle_pte_fault(struct mm_struct *mm,
        barrier();
        if (!pte_present(entry)) {
                if (pte_none(entry)) {
-                       if (vma->vm_ops) {
-                               if (likely(vma->vm_ops->fault))
-                                       return do_fault(mm, vma, address, pte,
-                                                       pmd, flags, entry);
-                       }
-                       return do_anonymous_page(mm, vma, address,
-                                                pte, pmd, flags);
+                       if (vma_is_anonymous(vma))
+                               return do_anonymous_page(mm, vma, address,
+                                                        pte, pmd, flags);
+                       else
+                               return do_fault(mm, vma, address, pte, pmd,
+                                               flags, entry);
                }
                return do_swap_page(mm, vma, address,
                                        pte, pmd, flags, entry);
-- 
1.5.5.1

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