linux-kernel - [PATCH] Remove large struct from the stack in USB storage isd200 driver

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Date:	Wed,  3 Mar 2010 11:00:37 +1100
From:	imunsie@....ibm.com
To:	linux-kernel@...r.kernel.org
Cc:	Ian Munsie <imunsie@....ibm.com>,
	Matthew Dharm <mdharm-usb@...-eyed-alien.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, usb-storage@...ts.one-eyed-alien.net
Subject: [PATCH] Remove large struct from the stack in USB storage isd200 driver

From: Ian Munsie <imunsie@...ibm.com>

The compiler throws the following warning when compiling for a PowerPC 64
bit machine:

drivers/usb/storage/isd200.c:580: warning: the frame size of 2208 bytes is larger than 2048 bytes

There is a struct scsi_device which is placed on the stack and is
largely responsible for such wastage. The struct is just a dummy struct
filled with NULLs and set as the scsi_cmnd->device to make the
usb_stor_Bulk_transport function happy.

This patch makes the struct static, so that it is never placed onto the
stack and silences the compiler warning.

Signed-off-by: Ian Munsie <imunsie@...ibm.com>
---
 drivers/usb/storage/isd200.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/storage/isd200.c b/drivers/usb/storage/isd200.c
index fdba2f6..e9cbc14 100644
--- a/drivers/usb/storage/isd200.c
+++ b/drivers/usb/storage/isd200.c
@@ -490,13 +490,13 @@ static int isd200_action( struct us_data *us, int action,
 			  void* pointer, int value )
 {
 	union ata_cdb ata;
-	struct scsi_device srb_dev;
+	/* static to prevent this large struct being placed on the valuable stack */
+	static struct scsi_device srb_dev;
 	struct isd200_info *info = (struct isd200_info *)us->extra;
 	struct scsi_cmnd *srb = &info->srb;
 	int status;
 
 	memset(&ata, 0, sizeof(ata));
-	memset(&srb_dev, 0, sizeof(srb_dev));
 	srb->cmnd = info->cmnd;
 	srb->device = &srb_dev;
 	++srb->serial_number;
-- 
1.6.6.1

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