linux-kernel - Re: [BUGFIX][PATCH 2/5] memcg: fix init_page

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Date:	Tue, 14 Jun 2011 11:44:39 +0200
From:	Johannes Weiner <jweiner@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"bsingharora@...il.com" <bsingharora@...il.com>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>, Ying Han <yinghan@...gle.com>
Subject: Re: [BUGFIX][PATCH 2/5] memcg: fix init_page_cgroup nid with
 sparsemem

On Mon, Jun 13, 2011 at 12:06:08PM +0900, KAMEZAWA Hiroyuki wrote:
> added some clean ups.
> ==
> >From 45b8881201f73015c4e0352eb7e434f6e9c53fdd Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Date: Mon, 13 Jun 2011 10:09:17 +0900
> Subject: [PATCH 2/5] [BUGFIX] memcg: fix init_page_cgroup nid with sparsemem
> 
> 
> commit 21a3c96 makes page_cgroup allocation as NUMA aware. But that caused
> a problem https://bugzilla.kernel.org/show_bug.cgi?id=36192.
> 
> The problem was getting a NID from invalid struct pages, which was not
> initialized because it was out-of-node, out of [node_start_pfn, node_end_pfn)
> 
> Now, with sparsemem, page_cgroup_init scans pfn from 0 to max_pfn.
> But this may scan a pfn which is not on any node and can access
> memmap which is not initialized.
> 
> This makes page_cgroup_init() for SPARSEMEM node aware and remove
> a code to get nid from page->flags. (Then, we'll use valid NID
> always.)
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Acked-by: Johannes Weiner <jweiner@...hat.com>
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