linux-kernel - Re: Subject: [PATCH] crypto: s390: Remove BKL in zcrypt

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Message-ID: <alpine.LFD.2.00.0910211505320.3526@localhost.localdomain>
Date:	Wed, 21 Oct 2009 15:09:23 +0200 (CEST)
From:	John Kacur <jkacur@...hat.com>
To:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arndbergmann@...glemail.com>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Felix Beck <felix.beck@...ibm.com>,
	Ralph Wuerthner <ralph.wuerthner@...ibm.com>,
	linux390@...ibm.com, linux-s390@...r.kernel.org
Subject: Re: Subject: [PATCH] crypto: s390: Remove BKL in zcrypt_open


I took a deeper look at this after all of the great information form folks 
like Arnd and Thomas about what to be careful of. I think this patch is 
safe to do. I have respun it and explicitly set llseek to nollseek.

It is still RFC, or pending an ack by the S390 zcrypt folks who can 
actually test it.

Thanks

>From 6d3fad58dbeae2e37aeb093197c25a57018ab8fd Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@...hat.com>
Date: Mon, 19 Oct 2009 00:44:03 +0200
Subject: [PATCH] crypto: s390: Remove BKL in zcrypt_open

Remove the BKL in zcrypt_open and explicitly set llseek = nollseek.

- zcrypt_read, zcrypt_write, just return -EPERM
- zcrypt_open only has an atomic_inc which doesn't need to be locked.
- The bkl in the zcrypt_open function could conceivably be serializing the misc_register() in zcrypt_api_init(). However, the rest of the code is protected by the zcrypt_rng_mutex and the ioctl is already an unlocked_ioctl kind.

Signed-off-by: John Kacur <jkacur@...hat.com>
---
 drivers/s390/crypto/zcrypt_api.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index 65b6a96..22c9b0a 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -34,7 +34,6 @@
 #include <linux/fs.h>
 #include <linux/proc_fs.h>
 #include <linux/compat.h>
-#include <linux/smp_lock.h>
 #include <asm/atomic.h>
 #include <asm/uaccess.h>
 #include <linux/hw_random.h>
@@ -299,9 +298,7 @@ static ssize_t zcrypt_write(struct file *filp, const char __user *buf,
  */
 static int zcrypt_open(struct inode *inode, struct file *filp)
 {
-	lock_kernel();
 	atomic_inc(&zcrypt_open_count);
-	unlock_kernel();
 	return 0;
 }
 
@@ -888,6 +885,7 @@ static long zcrypt_compat_ioctl(struct file *filp, unsigned int cmd,
  */
 static const struct file_operations zcrypt_fops = {
 	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
 	.read		= zcrypt_read,
 	.write		= zcrypt_write,
 	.unlocked_ioctl	= zcrypt_unlocked_ioctl,
-- 
1.6.0.6


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