linux-kernel - Re: [JANITOR PROPOSAL] Switch ioctl functions to ->unlocked

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Message-ID: <20080108204214.GA2117@one.firstfloor.org>
Date:	Tue, 8 Jan 2008 21:42:14 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Paolo Ciarrocchi <paolo.ciarrocchi@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, gorcunov@...il.com
Subject: Re: [JANITOR PROPOSAL] Switch ioctl functions to ->unlocked_ioctl

> I grepped and tried to do what you suggested.

First a quick question: how would you rate your C knowledge? Did you
ever write a program yourself? 

My proposal assumes that you have at least basic C knowledge.

> The first file that git grep reported was:
> arch/arm/common/rtctime.c:static const struct file_operations rtc_fops = {

It's probably better to only do that on files which you can easily compile.
For ARM you would need a cross compiler.

> 
> So I cooked up the following patch (probably mangled, just to give you
> a rough idea of what I did):
> diff --git a/arch/arm/common/rtctime.c b/arch/arm/common/rtctime.c
> index bf1075e..19dedb5 100644
> --- a/arch/arm/common/rtctime.c
> +++ b/arch/arm/common/rtctime.c
> @@ -189,13 +189,16 @@ static int rtc_ioctl(struct inode *inode, struct
> file *file, unsigned int cmd,
>  		if (ret)
>  			break;
>  		ret = copy_to_user(uarg, &alrm.time, sizeof(tm));
> -		if (ret)
> +		if (ret) {
> +			unlock_kernel();
>  			ret = -EFAULT;

In this case it would be better to just put the unlock_kernel() directly
before the single return. You only need to sprinkle them all over when
the function has multiple returns. Or then change the flow to only
have a single return, but that would be slightly advanced.


> -		if (ret)
> +		if (ret) {
> +			unlock_kernel();
>  			ret = -EFAULT;
> +		}
>  		break;
> 
>  	default:
> @@ -329,15 +340,18 @@ static int rtc_fasync(int fd, struct file *file, int on)
>  	return fasync_helper(fd, file, on, &rtc_async_queue);
>  }
> 
> -static const struct file_operations rtc_fops = {
> +static long rtc_fioctl(struct file_operations rtc_fops)
> +{
> +	lock_kernel();

No the lock_kernel() of course has to be in the function, not in the structure
definition which does not contain any code.

Also the _operations structure stays the same (except for .ioctl -> .unlocked_ioctl); 
only the the ioctl function prototype changes.


> Am I'm working in the right direction or should I completely redo the patch?

I would suggest to only work on files that compile. e.g. do a

make allyesconfig
make -j$[$(grep -c processor /proc/cpuinfo)*2] &1 |tee LOG             (will probably take a long time) 

first and then only modify files when are mentioned in "LOG" 

-Andi
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