Date: Fri, 13 Aug 2010 07:47:21 -0500 (CDT)
From: Christoph Lameter <cl@linux-foundation.org>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
cc: Andi Kleen <andi@firstfloor.org>,
        Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mel@csn.ul.ie>,
        Wu Fengguang <fengguang.wu@intel.com>,
        "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>,
        linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/9] Hugepage migration (v2)
In-Reply-To: <20100812075323.GA6112@spritzera.linux.bs1.fc.nec.co.jp>
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On Thu, 12 Aug 2010, Naoya Horiguchi wrote:

> > Can you also avoid refcounts being increased during migration?
>
> Yes. I think this will be done in above-mentioned refactoring.

Thats not what I meant. Can you avoid other processors increasing
refcounts (direct I/O etc?) on any page struct of the huge page while
migration is running?

> This patch only handles migration under direct I/O.
> For the opposite (direct I/O under migration) it's not true.
> I wrote additional patches (later I'll reply to this email)
> for solving locking problem. Could you review them?

Sure.

> (Maybe these patches are beyond the scope of hugepage migration patch,
> so is it better to propose them separately?)

Migration with known races is really not what we want in the kernel.

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