linux-kernel - Re: mm: slub: invalid memory access in setup

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Message-ID: <alpine.DEB.2.02.1406301500410.13545@chino.kir.corp.google.com>
Date:	Mon, 30 Jun 2014 15:03:21 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...two.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>
cc:	Pekka Enberg <penberg@...nel.org>, Matt Mackall <mpm@...enic.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: mm: slub: invalid memory access in setup_object

On Wed, 25 Jun 2014, Christoph Lameter wrote:

> On Wed, 25 Jun 2014, Sasha Levin wrote:
> 
> > [  791.669480] ? init_object (mm/slub.c:665)
> > [  791.669480] setup_object.isra.34 (mm/slub.c:1008 mm/slub.c:1373)
> > [  791.669480] new_slab (mm/slub.c:278 mm/slub.c:1412)
> 
> So we just got a new page from the page allocator but somehow cannot
> write to it. This is the first write access to the page.
> 

I'd be inclined to think that this was a result of "slub: reduce duplicate 
creation on the first object" from -mm[*] that was added the day before 
Sasha reported the problem.

It's not at all clear to me that that patch is correct.  Wei?

Sasha, with a revert of that patch, does this reproduce?

 [*] http://ozlabs.org/~akpm/mmotm/broken-out/slub-reduce-duplicate-creation-on-the-first-object.patch
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