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Date: Fri, 27 Sep 2002 11:35:05 -0700
From: Andrew Morton <akpm@digeo.com>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Ingo Molnar <mingo@elte.hu>, Chris Wedgwood <cw@f00f.org>,
       Linus Torvalds <torvalds@transmeta.com>,
       Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org
Subject: Re: [patch] 'virtual => physical page mapping cache',vcache-2.5.38-B8
References: <Pine.LNX.4.44.0209271952540.17034-100000@localhost.localdomain> <1033149675.16758.8.camel@irongate.swansea.linux.org.uk>
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Alan Cox wrote:
> 
> On Fri, 2002-09-27 at 18:53, Ingo Molnar wrote:
> >
> > On Fri, 27 Sep 2002, Chris Wedgwood wrote:
> >
> > > O_DIRECT is allow to break if someone does something silly :)  [...]
> >
> > to DMA into a page that does not belong to the process anymore? I doubt
> > that.
> 
> Try doing a truncate on a file as an O_DIRECT write is occuring.
> Scribbling into pages you dont own is the least of your problems.

O_DIRECT writes operate under i_sem, which provides exclusion
from trucate.  Do you know something which I don't??