linux-kernel - [PATCH] drivers/mtd/ubi/wl.c: optimization for in_wl

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Date:	Sat,  9 Jun 2012 20:57:53 -0500
From:	Daniel Santos <daniel.santos@...ox.com>
To:	Richard Weinberger <richard@....at>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Daniel Santos <daniel.santos@...ox.com>
Subject: [PATCH] drivers/mtd/ubi/wl.c: optimization for in_wl_tree()

Essentially, instead of performing a search through the tree from the
top down, like we would when doing a lookup, we can just search from the
node up and then check to see if the root of the tree that the node is
in is the same as the one supplied.  Note that if you call this passing
a ubi_wl_entry who's u.rb member has not been inited with rb_init_node()
or added to a tree, the results are undefined.

This should be a little faster, but mostly, it'll be smaller.
---
 drivers/mtd/ubi/wl.c |   32 ++++++++------------------------
 1 files changed, 8 insertions(+), 24 deletions(-)

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 9df100a..d415011 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -287,33 +287,17 @@ static int produce_free_peb(struct ubi_device *ubi)
  */
 static int in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root)
 {
-	struct rb_node *p;
-
-	p = root->rb_node;
-	while (p) {
-		struct ubi_wl_entry *e1;
+	struct rb_node *p = &e->u.rb, *parent = rb_parent(&e->u.rb);
 
-		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
-
-		if (e->pnum == e1->pnum) {
-			ubi_assert(e == e1);
-			return 1;
-		}
+	if (parent == p)
+		return 0;
 
-		if (e->ec < e1->ec)
-			p = p->rb_left;
-		else if (e->ec > e1->ec)
-			p = p->rb_right;
-		else {
-			ubi_assert(e->pnum != e1->pnum);
-			if (e->pnum < e1->pnum)
-				p = p->rb_left;
-			else
-				p = p->rb_right;
-		}
-	}
+	do {
+		p = parent;
+		parent = rb_parent(parent);
+	} while (parent);
 
-	return 0;
+	return p == root->rb_node;
 }
 
 /**
-- 
1.7.3.4

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