linux-kernel - Re: [patch] mm, page_alloc: make first

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Message-Id: <20140204160641.8f5d369eeb2d0318618d6d5f@linux-foundation.org>
Date:	Tue, 4 Feb 2014 16:06:41 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Holger Kiehl <Holger.Kiehl@....de>,
	Christoph Lameter <cl@...ux.com>,
	Rafael Aquini <aquini@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Mel Gorman <mgorman@...e.de>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, page_alloc: make first_page visible before PageTail

On Tue, 4 Feb 2014 16:02:39 -0800 (PST) David Rientjes <rientjes@...gle.com> wrote:

> Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned 
> pages") introduces page_count(page) into memory compaction which 
> dereferences page->first_page if PageTail(page).
> 
> Introduce a store memory barrier to ensure page->first_page is properly 
> initialized so that code that does page_count(page) on pages off the lru 
> always have a valid p->first_page.

Could we have a code comment please?  Even checkpatch knows this rule!

> Reported-by: Holger Kiehl <Holger.Kiehl@....de>

What did Holger report?

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