linux-kernel - Re: [PATCH v2 1/7] mm/compaction: split freepages without holding the zone lock

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Date:	Fri, 17 Jun 2016 16:27:53 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>, mgorman@...hsingularity.net,
	Minchan Kim <minchan@...nel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH v2 1/7] mm/compaction: split freepages without holding
 the zone lock

On Wed, Jun 15, 2016 at 11:27:31AM +0900, Joonsoo Kim wrote:
> On Tue, Jun 14, 2016 at 03:10:21PM -0400, Sasha Levin wrote:
> > On 06/14/2016 01:52 AM, Joonsoo Kim wrote:
> > > On Mon, Jun 13, 2016 at 04:31:15PM -0400, Sasha Levin wrote:
> > >> > On 05/25/2016 10:37 PM, js1304@...il.com wrote:
> > >>> > > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> > >>> > > 
> > >>> > > We don't need to split freepages with holding the zone lock. It will cause
> > >>> > > more contention on zone lock so not desirable.
> > >>> > > 
> > >>> > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> > >> > 
> > >> > Hey Joonsoo,
> > > Hello, Sasha.
> > >> > 
> > >> > I'm seeing the following corruption/crash which seems to be related to
> > >> > this patch:
> > > Could you tell me why you think that following corruption is related
> > > to this patch? list_del() in __isolate_free_page() is unchanged part.
> > > 
> > > Before this patch, we did it by split_free_page() ->
> > > __isolate_free_page() -> list_del(). With this patch, we do it by
> > > calling __isolate_free_page() directly.
> > 
> > I haven't bisected it, but it's the first time I see this issue and this
> > commit seems to have done related changes that might cause this.
> > 
> > I can go ahead with bisection if you don't think it's related.
> 
> Hmm... I can't find a bug in this patch for now. There are more candidates
> on this area hat changed by me and it would be very helpful if you can
> do bisection.

Hello, Sasha.

You are right! Minchan found the bug in this patch! I will send
updated patch soon.

http://marc.info/?i=20160616100932.GS17127%40bbox

Thanks.