mm: add vma_iter_{next,prev}_range() to vma iterator

Add functionality to the VMA iterator to advance and retreat one offset
within the maple tree, regardless of the value contained.  This can lead
to less re-walking to find an area of interest, especially when there is
nothing in that offset.

Link: https://lkml.kernel.org/r/20230518145544.1722059-35-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: David Binderman <dcb314@hotmail.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -866,11 +866,24 @@ static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi)
 	return mas_find(&vmi->mas, ULONG_MAX);
 }
 
+static inline
+struct vm_area_struct *vma_iter_next_range(struct vma_iterator *vmi)
+{
+	return mas_next_range(&vmi->mas, ULONG_MAX);
+}
+
+
 static inline struct vm_area_struct *vma_prev(struct vma_iterator *vmi)
 {
 	return mas_prev(&vmi->mas, 0);
 }
 
+static inline
+struct vm_area_struct *vma_iter_prev_range(struct vma_iterator *vmi)
+{
+	return mas_prev_range(&vmi->mas, 0);
+}
+
 static inline unsigned long vma_iter_addr(struct vma_iterator *vmi)
 {
 	return vmi->mas.index;