[PATCH v2 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 accurate, say a hpet_mmap()'ed 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). "True" just means
that a page fault will use do_anonymous_page().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/mm.h |    5 +++++
 mm/memory.c        |    8 ++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0755b9f..0207ffa 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;
+}
+
 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 2a9e098..87c9285 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3249,12 +3249,12 @@ static int handle_pte_fault(struct mm_struct *mm,
 	barrier();
 	if (!pte_present(entry)) {
 		if (pte_none(entry)) {
-			if (vma->vm_ops)
+			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_anonymous_page(mm, vma, address, pte, pmd,
-					flags);
 		}
 		return do_swap_page(mm, vma, address,
 					pte, pmd, flags, entry);
-- 
1.5.5.1