ksm: cleanup: introduce find_mergeable_vma()

There are multiple places which perform the same check.  Add a new
find_mergeable_vma() to handle this.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/ksm.c

@@ -374,6 +374,20 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
 	return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
 }
 
+static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm,
+		unsigned long addr)
+{
+	struct vm_area_struct *vma;
+	if (ksm_test_exit(mm))
+		return NULL;
+	vma = find_vma(mm, addr);
+	if (!vma || vma->vm_start > addr)
+		return NULL;
+	if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
+		return NULL;
+	return vma;
+}
+
 static void break_cow(struct rmap_item *rmap_item)
 {
 	struct mm_struct *mm = rmap_item->mm;
@@ -387,15 +401,9 @@ static void break_cow(struct rmap_item *rmap_item)
 	put_anon_vma(rmap_item->anon_vma);
 
 	down_read(&mm->mmap_sem);
-	if (ksm_test_exit(mm))
-		goto out;
-	vma = find_vma(mm, addr);
-	if (!vma || vma->vm_start > addr)
-		goto out;
-	if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
-		goto out;
-	break_ksm(vma, addr);
-out:
+	vma = find_mergeable_vma(mm, addr);
+	if (vma)
+		break_ksm(vma, addr);
 	up_read(&mm->mmap_sem);
 }
 
@@ -421,12 +429,8 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
 	struct page *page;
 
 	down_read(&mm->mmap_sem);
-	if (ksm_test_exit(mm))
-		goto out;
-	vma = find_vma(mm, addr);
-	if (!vma || vma->vm_start > addr)
-		goto out;
-	if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
+	vma = find_mergeable_vma(mm, addr);
+	if (!vma)
 		goto out;
 
 	page = follow_page(vma, addr, FOLL_GET);