mm/mmap.c: refine find_vma_prev() with rb_last()

When addr is out of range of the whole rb_tree, pprev will point 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
reimplementing it.

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

[akpm@linux-foundation.org: little cleanup, per Vlastimil]
Link: http://lkml.kernel.org/r/20190809001928.4950-1-richardw.yang@linux.intel.com
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 6bc21fc..e4a8f67 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2274,12 +2274,9 @@ 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 ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
        }
        return vma;
 }