From: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> Subject: lib/rbtree: set successor's parent unconditionally Both in Case 2 and 3, we exchange n and s. This mean no matter whether child2 is NULL or not, successor's parent should be assigned to node's. This patch takes this step out to make it explicit and reduce the ambiguity. Besides, this step reduces some symbol size like rb_erase(). KERN_CONFIG upstream patched OPT_FOR_PERF 877 870 OPT_FOR_SIZE 635 621 Link: http://lkml.kernel.org/r/20191028021442.5450-1-richardw.yang@xxxxxxxxxxxxxxx Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Michel Lespinasse <walken@xxxxxxxxxx> Reviewed-by: Davidlohr Bueso <dbueso@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/rbtree_augmented.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/include/linux/rbtree_augmented.h~lib-rbtree-set-successors-parent-unconditionally +++ a/include/linux/rbtree_augmented.h @@ -283,14 +283,13 @@ __rb_erase_augmented(struct rb_node *nod __rb_change_child(node, successor, tmp, root); if (child2) { - successor->__rb_parent_color = pc; rb_set_parent_color(child2, parent, RB_BLACK); rebalance = NULL; } else { unsigned long pc2 = successor->__rb_parent_color; - successor->__rb_parent_color = pc; rebalance = __rb_is_black(pc2) ? parent : NULL; } + successor->__rb_parent_color = pc; tmp = successor; } _
