[Xen-devel] [PATCH v4 13/17] rbtree: add __rb_change_child() helper function

[Praveen Kumar <kpraveen.lkml@xxxxxxxxx>]

From: Michel Lespinasse <walken@xxxxxxxxxx>

Add __rb_change_child() as an inline helper function to replace code that
would otherwise be duplicated 4 times in the source.

No changes to binary size or speed.

Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[Linux commit 7abc704ae399fcb9c51ca200b0456f8a975a8011]

Ported to Xen.

Signed-off-by: Praveen Kumar <kpraveen.lkml@xxxxxxxxx>
---
 xen/common/rbtree.c | 46 +++++++++++++++++-----------------------------
 1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c
index 56c815b4a5..d438d50761 100644
--- a/xen/common/rbtree.c
+++ b/xen/common/rbtree.c
@@ -65,6 +65,19 @@ static inline struct rb_node *rb_red_parent(struct rb_node 
*red)
        return (struct rb_node *)red->__rb_parent_color;
 }
 
+static inline void
+__rb_change_child(struct rb_node *old, struct rb_node *new,
+                 struct rb_node *parent, struct rb_root *root)
+{
+       if (parent) {
+               if (parent->rb_left == old)
+                       parent->rb_left = new;
+               else
+                       parent->rb_right = new;
+       } else
+               root->rb_node = new;
+}
+
 /*
  * Helper function for rotations:
  * - old's parent and color get assigned to new
@@ -77,13 +90,7 @@ __rb_rotate_set_parents(struct rb_node *old, struct rb_node 
*new,
        struct rb_node *parent = rb_parent(old);
        new->__rb_parent_color = old->__rb_parent_color;
        rb_set_parent_color(old, new, color);
-       if (parent) {
-               if (parent->rb_left == old)
-                       parent->rb_left = new;
-               else
-                       parent->rb_right = new;
-       } else
-               root->rb_node = new;
+       __rb_change_child(old, new, parent, root);
 }
 
 void rb_insert_color(struct rb_node *node, struct rb_root *root)
@@ -374,13 +381,7 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
                while ((left = node->rb_left) != NULL)
                        node = left;
 
-               if (rb_parent(old)) {
-                       if (rb_parent(old)->rb_left == old)
-                               rb_parent(old)->rb_left = node;
-                       else
-                               rb_parent(old)->rb_right = node;
-               } else
-                       root->rb_node = node;
+               __rb_change_child(old, node, rb_parent(old), root);
 
                child = node->rb_right;
                parent = rb_parent(node);
@@ -410,13 +411,7 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
 
        if (child)
                rb_set_parent(child, parent);
-       if (parent) {
-               if (parent->rb_left == node)
-                       parent->rb_left = child;
-               else
-                       parent->rb_right = child;
-       } else
-               root->rb_node = child;
+       __rb_change_child(node, child, parent, root);
 
 color:
        if (color == RB_BLACK)
@@ -520,14 +515,7 @@ void rb_replace_node(struct rb_node *victim, struct 
rb_node *new,
        struct rb_node *parent = rb_parent(victim);
 
        /* Set the surrounding nodes to point to the replacement */
-       if (parent) {
-               if (victim == parent->rb_left)
-                       parent->rb_left = new;
-               else
-                       parent->rb_right = new;
-       } else {
-               root->rb_node = new;
-       }
+       __rb_change_child(victim, new, parent, root);
        if (victim->rb_left)
                rb_set_parent(victim->rb_left, new);
        if (victim->rb_right)
-- 
2.12.0


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