Re: [BUG] memcg: panic when rmdir()

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 16 Jan 2009 18:13:00 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Fri, 16 Jan 2009 17:26:51 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> > On Fri, 16 Jan 2009 17:07:24 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > 
> > > Now, at swapoff, even while try_charge() fails, commit is executed.
> > > This is bug and make refcnt of cgroup_subsys_state minus, finally.
> > > 
> > Nice catch!
> > 
> > I think this bug can explain this problem I've seen.
> > Commiting on trycharge failure will add the pc to the lru
> > without a corresponding charge and refcnt.
> > And rmdir uncharges the pc(so we get WARNING: at kernel/res_counter.c:71)
> > and decrements the refcnt(so we get BUG at kernel/cgroup.c:2517).
> > 
> > Even if the problem cannot be fixed by this patch, this patch is valid and needed.
> > 
> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> > 
> > I'll test it.
> > 
> I've tested several times, but this problem didn't happen.
> 
> Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 

Thank you!, I'll send the patch to Andrew.

-Kame

> 
> Thanks,
> Daisuke Nishimura.
> 
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