Date: Tue, 30 Nov 2010 09:38:04 +0900
From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>,
        Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
        Hugh Dickins <hugh.dickins@tiscali.co.uk>,
        Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Christoph Lameter <cl@linux-foundation.org>,
        Chris Wright <chrisw@sous-sol.org>, bpicco@redhat.com,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Chris Mason <chris.mason@oracle.com>, Borislav Petkov <bp@alien8.de>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Subject: Re: [PATCH 53 of 66] add numa awareness to hugepage allocations
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On Mon, 29 Nov 2010 17:11:03 +0100
Andrea Arcangeli <aarcange@redhat.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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