linux-kernel - Re: [PATCH 53 of 66] add numa awareness to hugepage allocations

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Message-Id: <20101130093804.23f8c355.nishimura@mxp.nes.nec.co.jp>
Date:	Tue, 30 Nov 2010 09:38:04 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>, bpicco@...hat.com,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Chris Mason <chris.mason@...cle.com>,
	Borislav Petkov <bp@...en8.de>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH 53 of 66] add numa awareness to hugepage allocations

On Mon, 29 Nov 2010 17:11:03 +0100
Andrea Arcangeli <aarcange@...hat.com> wrote:

> On Mon, Nov 29, 2010 at 02:38:01PM +0900, Daisuke Nishimura wrote:
> > I think this should be:
> > 
> > 	if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
> > #ifdef CONFIG_NUMA
> > 		put_page(new_page);
> > #endif
> > 		goto out;
> > 	}
> 
> Hmm no, the change you suggest would generate memory corruption with
> use after free.

I'm sorry if I miss something, "new_page" will be reused in !CONFIG_NUMA case
as you say, but, in CONFIG_NUMA case, it is allocated in this function
(collapse_huge_page()) by alloc_hugepage_vma(), and is not freed when memcg's
charge failed.
Actually, we do in collapse_huge_page():
	if (unlikely(!isolated)) {
		...
#ifdef CONFIG_NUMA
		put_page(new_page);
#endif
		goto out;
	}
later. I think we need a similar logic in memcg's failure path too.

Thanks,
Daisuke Nishimura.
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