linux-kernel - Re: [patch 9/9] mm: fix pagecache write deadlocks

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Message-ID: <20070206055328.GD16647@wotan.suse.de>
Date:	Tue, 6 Feb 2007 06:53:28 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Filesystems <linux-fsdevel@...r.kernel.org>,
	Linux Memory Management <linux-mm@...ck.org>
Subject: Re: [patch 9/9] mm: fix pagecache write deadlocks

On Tue, Feb 06, 2007 at 06:49:05AM +0100, Nick Piggin wrote:
> > - If the get_user() doesn't fault, and if we're copying from and to the
> >   same page, we know that we've locked it, so nobody will be able to unmap
> >   it while we're copying from it.
> > 
> > Close, but no cigar!  This is still vulnerable to Hugh's ab/ba deadlock
> > scenario.
> 
> Yes I considered this too. Hard isn't it?

BTW, there are two different abba deadlocks. It's all documented in the
patch 9/9 description.
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