[PATCH 1/3] mm: introduce vma_is_anonymous(vma) helper

[Oleg Nesterov <oleg@redhat.com>]

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 <oleg@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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