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

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Message-ID: <20080109004748.GI2117@one.firstfloor.org>
Date:	Wed, 9 Jan 2008 01:47:48 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel@...r.kernel.org, apw@...dowen.org
Subject: Re: [JANITOR PROPOSAL] Switch ioctl functions to ->unlocked_ioctl

On Wed, Jan 09, 2008 at 01:40:58AM +0100, Arnd Bergmann wrote:
> On Tuesday 08 January 2008, Andi Kleen wrote:
> > > Thanks, Andi! I think it'd very useful change.
> > 
> > Reminds me this is something that should be actually flagged
> > in checkpatch.pl too
> > 
> > Andy, it would be good if checkpatch.pl complained about .ioctl = 
> > as opposed to .unlocked_ioctl = ...
> 
> This is rather hard, as there are different data structures that
> all contain ->ioctl and/or ->unlocked_ioctl function pointers.
> Some of them already use ->ioctl in an unlocked fashion only,
> so blindly warning about this would give lots of false positives.

I imagined it would check for 

+struct file_operations ... = { 
+      ...
+	.ioctl = ...

That wouldn't catch the case of someone adding only .ioctl to an 
already existing file_operations which is not visible in the patch context, 
but that should be hopefully rare. The more common case is adding
completely new operations

>  
> > Also perhaps if a whole new file_operations with a ioctl is added
> > complain about missing compat_ioctl as a low prioritity warning?
> > (might be ok if it's architecture specific on architectures without
> > compat layer)
> 
> Also, not every data structure that provides a ->ioctl callback
> also has a ->compat_ioctl, although there should be fewer exceptions

That's probably a bug in general. e.g. those likely won't work 
at all on the "compat by default" architectures like sparc or ppc64.

-Andi

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