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Date: Tue, 13 Apr 2010 22:10:18 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>,
       Stefan Richter <stefanr@s5r6.in-berlin.de>,
       Alexey Dobriyan <adobriyan@gmail.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       John Kacur <jkacur@redhat.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Al Viro <viro@zeniv.linux.org.uk>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH 6/6] procfs: Kill the bkl in ioctl
Message-ID: <20100413201014.GA5602@nowhere>
References: <1269930015-863-1-git-send-regression-fweisbec@gmail.com> <201004121934.18307.arnd@arndb.de> <20100412215320.GF8285@nowhere> <201004131126.27482.arnd@arndb.de>
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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.