linux-kernel - [PATCH] generic_nvram: Turn nvram

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Date:	Mon, 12 Oct 2009 00:12:45 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, John Kacur <jkacur@...hat.com>,
	Sven-Thorsten Dietrich <sven@...bigcorporation.com>,
	Jonathan Corbet <corbet@....net>,
	Alessio Igor Bogani <abogani@...ware.it>,
	Arnd Bergmann <arndbergmann@...glemail.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH] generic_nvram: Turn nvram_ioctl into an unlocked ioctl

nvram_ioctl is a bkl locked ioctl, but it can be an unlocked ioctl.

- part is provided by the user
- offset is provided by pmac_get_partition() which is safe as it only
  touches nvram_partitions, an array inistialized on __init time and
  read-only the rest of the time.
- nvram_sync() only relies on core99_nvram_sync() which checks
  is_core_99, nvram_data, nvram_image. Those are variables initialized
  on __init time only and their direct values are not touched further.
  The rest modifies the nvram image header, protected by nv_lock
  already.

So it's safe to call nvram_ioctl without the big kernel lock held.

Reported-by: Arnd Bergmann <arndbergmann@...glemail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: John Kacur <jkacur@...hat.com>
Cc: Sven-Thorsten Dietrich <sven@...bigcorporation.com>
Cc: Jonathan Corbet <corbet@....net>
Cc: Alessio Igor Bogani <abogani@...ware.it>
Cc: Arnd Bergmann <arndbergmann@...glemail.com>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
---
 drivers/char/generic_nvram.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/char/generic_nvram.c b/drivers/char/generic_nvram.c
index c49200e..fd448aa 100644
--- a/drivers/char/generic_nvram.c
+++ b/drivers/char/generic_nvram.c
@@ -118,11 +118,11 @@ static int nvram_ioctl(struct inode *inode, struct file *file,
 }
 
 const struct file_operations nvram_fops = {
-	.owner		= THIS_MODULE,
-	.llseek		= nvram_llseek,
-	.read		= read_nvram,
-	.write		= write_nvram,
-	.ioctl		= nvram_ioctl,
+	.owner			= THIS_MODULE,
+	.llseek			= nvram_llseek,
+	.read			= read_nvram,
+	.write			= write_nvram,
+	.unlocked_ioctl		= nvram_ioctl,
 };
 
 static struct miscdevice nvram_dev = {
-- 
1.6.2.3

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