linux-kernel - Re: [PATCH 6/6] procfs: Kill the bkl in ioctl

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Date:	Tue, 13 Apr 2010 22:10:18 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	Alexey Dobriyan <adobriyan@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Kacur <jkacur@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 6/6] procfs: Kill the bkl in ioctl

On Tue, Apr 13, 2010 at 11:26:27AM +0200, Arnd Bergmann wrote:
> On Monday 12 April 2010, Frederic Weisbecker wrote:
> > On Mon, Apr 12, 2010 at 07:34:17PM +0200, Arnd Bergmann wrote:
> > > 
> > > I think the rule set for the conversion needs to be one that can
> > > be done purely based on the code. How about this:
> > > 
> > > For each file operation {
> > >       if (uses f_pos) {
> > >               if (same module uses BKL)
> > >                       -> default_llseek
> > >               else
> > >                       -> generic_file_llseek
> > >       } else {
> > >               if (driver maintained)
> > >                       -> no_llseek (with maintainer ACK)
> > >               else
> > >                       -> noop_llseek
> > >       }
> > > }
> > 
> > It is also hard to determine a given driver really doesn't use
> > the bkl. A sole lock_kernel() grep in its files is not sufficient.
> > But a manual second pass should do the trick.
> 
> Why not? In my 2.6.33 based series, I have removed all implicit
> uses of the BKL, so we can be sure that it doesn't use the BKL
> unless the module is part of that series. The only two cases
> I can think of are:
> 
> - ioctl callback, which we should do in the same change, like I
> originally did. If a driver defines ->ioctl(), make it use
> deprecated_ioctl() and default_llseek()/deprecated_llseek.
> 
> - Any of the file systems from Jan's series.
> 
> 	Arnd


Ok looks like a good plan then.

Thanks.

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