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Date: Thu, 28 Jan 2010 16:57:58 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 04 of 31] update futex compound knowledge
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To: Mel Gorman <mel@csn.ul.ie>
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On Thu, Jan 28, 2010 at 03:33:57PM +0000, Mel Gorman wrote:
> On Wed, Jan 27, 2010 at 08:45:04PM +0100, Andrea Arcangeli wrote:
> > On Tue, Jan 26, 2010 at 06:37:07PM +0000, Mel Gorman wrote:
> > > I'm not fully getting from the changelog why the second round through
> > > __get_user_pages_fast() is necessary or why the write parameter is
> > > unconditionally 1.
> > 
> > The write parameter is unconditionally to 1 because the first gup_fast
> > already existing had it unconditionally set to 1, it's not relevant
> > with this change.
> > 
> 
> hmm, really? I was seeing rw == VERIFY_WRITE rather than an
> unconditional. I'll double check the kernel version I'm reading against
> when I read the next review.

No problem ;) and now I get why asked it, in my current version (last
pull) the code is:

again:
	err = get_user_pages_fast(address, 1, 1, &page);

Clearly if the above would have been rw == VERIFY_WRITE I would have
not used 1 in the __ irq disabled callout.

> Do please. That explanation helps a lot.

Glad it helps despite my broken english eheh, already included in #8
submit ;)

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