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Subject: Re: [RFC][PATCH] Cross Memory Attach
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christopher Yeoh <cyeoh@au1.ibm.com>, linux-kernel@vger.kernel.org
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Date: Thu, 16 Sep 2010 19:13:14 +0200
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On Thu, 2010-09-16 at 09:54 -0700, Linus Torvalds wrote:
> On Thu, Sep 16, 2010 at 9:27 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Wed, 2010-09-15 at 08:11 -0700, Linus Torvalds wrote:
> >
> >>    if (copy_to)
> >>       ret = copy_from_user(..);
> >>    else
> >>       ret = copy_to_user(..);
> >>    kunmap(process_pages[i]);
> >>    if (ret)
> >>       goto out;
> >
> > Shouldn't we be using kmap_atomic()
> 
> Over a copy_to/from_user? Not bloody likely.

Gah, indeed. OK, since its not nested kmap() should indeed work. The
alternative is using get_user_pages() on both address spaces, but I
guess that makes things unnecessarily complex.