[PATCH v2] mm/mmap.c: refine find_vma_prev with rb_last

[Wei Yang <richardw.yang@linux.intel.com>]

When addr is out of the range of the whole rb_tree, pprev will points to
the right-most node. rb_tree facility already provides a helper
function, rb_last, to do this task. We can leverage this instead of
re-implement it.

This patch refines find_vma_prev with rb_last to make it a little nicer
to read.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

---
v2: leverage rb_last
---
 mm/mmap.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 7e8c3e8ae75f..f7ed0afb994c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
 	if (vma) {
 		*pprev = vma->vm_prev;
 	} else {
-		struct rb_node *rb_node = mm->mm_rb.rb_node;
-		*pprev = NULL;
-		while (rb_node) {
-			*pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
-			rb_node = rb_node->rb_right;
-		}
+		struct rb_node *rb_node = rb_last(&mm->mm_rb);
+		*pprev = !rb_node ? NULL :
+			 rb_entry(rb_node, struct vm_area_struct, vm_rb);
 	}
 	return vma;
 }
-- 
2.17.1