linux-kernel - Re: RFC: Fix f_flags races without the BKL

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Message-ID: <20081229152732.GH496@one.firstfloor.org>
Date:	Mon, 29 Dec 2008 16:27:32 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Jonathan Corbet <corbet@....net>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Al Viro <viro@...IV.linux.org.uk>, bfields@...ldses.org,
	xfs-masters@....sgi.com
Subject: Re: RFC: Fix f_flags races without the BKL

On Mon, Dec 29, 2008 at 01:41:51PM +0100, Oleg Nesterov wrote:
> On 12/29, Jonathan Corbet wrote:
> >
> > After pondering for a while, I couldn't come up with anything better than a
> > global file->f_flags mutex.  There's no point in bloating struct file with
> > a mutex just for this purpose; it's hard to imagine that there will be any
> > real contention for this lock.
> 
> Yes, this patch is simple and straightforward, but now we can't change
> ->f_flags in non-preempible context. And the global lock is not very
> nice anyway.
> 
> Once again, can't we use O_LOCK_FLAGS bit? I agree, it is a bit ugly,
> and I won't insist if you don't like is.

I would prefer O_LOCK_FLAGS bit too. The global lock is not very nice
and I don't doubt someone will come up with a workload which
pounds on it.

-Andi
-- 
ak@...ux.intel.com
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