linux-kernel - [PATCH 3.12 095/127] drivers/vfio: Rework offsetofend()

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Message-Id: <f6e1251137182ba9029b056fd69aa26c8b5623c6.1480062521.git.jslaby@suse.cz>
Date:   Fri, 25 Nov 2016 09:30:08 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 095/127] drivers/vfio: Rework offsetofend()

From: Gavin Shan <gwshan@...ux.vnet.ibm.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit b13460b92093b29347e99d6c3242e350052b62cd upstream.

The macro offsetofend() introduces unnecessary temporary variable
"tmp". The patch avoids that and saves a bit memory in stack.

Signed-off-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 include/linux/vfio.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 24579a0312a0..43f6bf4f8585 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -86,9 +86,8 @@ extern void vfio_unregister_iommu_driver(
  * from user space.  This allows us to easily determine if the provided
  * structure is sized to include various fields.
  */
-#define offsetofend(TYPE, MEMBER) ({				\
-	TYPE tmp;						\
-	offsetof(TYPE, MEMBER) + sizeof(tmp.MEMBER); })		\
+#define offsetofend(TYPE, MEMBER) \
+	(offsetof(TYPE, MEMBER)	+ sizeof(((TYPE *)0)->MEMBER))
 
 /*
  * External user API
-- 
2.10.2