Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Wei Yang <richardw.yang@linux.intel.com>
To:     akpm@linux-foundation.org, peterz@infradead.org, walken@google.com,
        richardw.yang@linux.intel.com, dbueso@suse.de, tglx@linutronix.de
Cc:     linux-kernel@vger.kernel.org
Subject: [Patch v2 1/2] lib/rbtree: set successor's parent unconditionally
Date:   Mon, 28 Oct 2019 10:14:41 +0800
Message-Id: <20191028021442.5450-1-richardw.yang@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 include/linux/rbtree_augmented.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index fdd421b8d9ae..99c42e1a74b8 100644
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -283,14 +283,13 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 		__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;
 	}
 
-- 
2.17.1