From dcbff5d1effbbd52be1ed9f2efb6c8d0445ad188 Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Fri, 6 Jun 2014 14:37:15 -0700
Subject: [PATCH] idr: reorder the fields

idr_layer->layer is always accessed in read path, move it in the front.

idr_layer->bitmap is moved on the bottom.  And rcu_head shares with
bitmap due to they do not be accessed at the same time.

idr->id_free/id_free_cnt/lock are free list fields, and moved to the
bottom.  They will be removed in near future.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/idr.h | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 6af3400b9b2f..013fd9bc4cb6 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -29,21 +29,24 @@
 
 struct idr_layer {
 	int			prefix;	/* the ID prefix of this idr_layer */
-	DECLARE_BITMAP(bitmap, IDR_SIZE); /* A zero bit means "space here" */
+	int			layer;	/* distance from leaf */
 	struct idr_layer __rcu	*ary[1<<IDR_BITS];
 	int			count;	/* When zero, we can release it */
-	int			layer;	/* distance from leaf */
-	struct rcu_head		rcu_head;
+	union {
+		/* A zero bit means "space here" */
+		DECLARE_BITMAP(bitmap, IDR_SIZE);
+		struct rcu_head		rcu_head;
+	};
 };
 
 struct idr {
 	struct idr_layer __rcu	*hint;	/* the last layer allocated from */
 	struct idr_layer __rcu	*top;
-	struct idr_layer	*id_free;
 	int			layers;	/* only valid w/o concurrent changes */
-	int			id_free_cnt;
 	int			cur;	/* current pos for cyclic allocation */
 	spinlock_t		lock;
+	int			id_free_cnt;
+	struct idr_layer	*id_free;
 };
 
 #define IDR_INIT(name)							\
-- 
2.20.1