Revert "mm/mmap: drop range_has_overlap() function"

This reverts commit 30cbc90.

mm/mmap.c

@@ -390,6 +390,30 @@ anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
 		anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
 }
 
+/*
+ * range_has_overlap() - Check the @start - @end range for overlapping VMAs and
+ * sets up a pointer to the previous VMA
+ * @mm: the mm struct
+ * @start: the start address of the range
+ * @end: the end address of the range
+ * @pprev: the pointer to the pointer of the previous VMA
+ *
+ * Returns: True if there is an overlapping VMA, false otherwise
+ */
+static inline
+bool range_has_overlap(struct mm_struct *mm, unsigned long start,
+		       unsigned long end, struct vm_area_struct **pprev)
+{
+	struct vm_area_struct *existing;
+
+	MA_STATE(mas, &mm->mm_mt, start, start);
+	rcu_read_lock();
+	existing = mas_find(&mas, end - 1);
+	*pprev = mas_prev(&mas, 0);
+	rcu_read_unlock();
+	return existing ? true : false;
+}
+
 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 		unsigned long addr, unsigned long end)
 {
@@ -3151,10 +3175,11 @@ void exit_mmap(struct mm_struct *mm)
  */
 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 {
+	struct vm_area_struct *prev;
 	unsigned long charged = vma_pages(vma);
 
 
-	if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
+	if (range_has_overlap(mm, vma->vm_start, vma->vm_end, &prev))
 		return -ENOMEM;
 
 	if ((vma->vm_flags & VM_ACCOUNT) &&