From: Michel Lespinasse Date: Wed, 3 Jan 2018 11:41:29 +0000 (+0100) Subject: rbtree: place easiest case first in rb_erase() X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~865 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=a6b1da2915b195cda66026e1024dc54375da08b4;p=xen.git rbtree: place easiest case first in rb_erase() In rb_erase, move the easy case (node to erase has no more than 1 child) first. I feel the code reads easier that way. Signed-off-by: Michel Lespinasse Reviewed-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [Linux commit 60670b8034d6e2ba860af79c9379b7788d09db73] Ported to Xen. Signed-off-by: Praveen Kumar Acked-by: Jan Beulich --- diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c index 0bba524218..e5697044a5 100644 --- a/xen/common/rbtree.c +++ b/xen/common/rbtree.c @@ -368,17 +368,28 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, void rb_erase(struct rb_node *node, struct rb_root *root) { - struct rb_node *child, *parent; + struct rb_node *child = node->rb_right, *tmp = node->rb_left; + struct rb_node *parent; int color; - if (!node->rb_left) - child = node->rb_right; - else if (!node->rb_right) - child = node->rb_left; - else { + if (!tmp) { + case1: + /* Case 1: node to erase has no more than 1 child (easy!) */ + + parent = rb_parent(node); + color = rb_color(node); + + if (child) + rb_set_parent(child, parent); + __rb_change_child(node, child, parent, root); + } else if (!child) { + /* Still case 1, but this time the child is node->rb_left */ + child = tmp; + goto case1; + } else { struct rb_node *old = node, *left; - node = node->rb_right; + node = child; while ((left = node->rb_left) != NULL) node = left; @@ -402,18 +413,8 @@ void rb_erase(struct rb_node *node, struct rb_root *root) node->__rb_parent_color = old->__rb_parent_color; node->rb_left = old->rb_left; rb_set_parent(old->rb_left, node); - - goto color; } - parent = rb_parent(node); - color = rb_color(node); - - if (child) - rb_set_parent(child, parent); - __rb_change_child(node, child, parent, root); - -color: if (color == RB_BLACK) __rb_erase_color(child, parent, root); }