linux-kernel - Re: [RFC PATCH] vhost, mm: make sure that oom_reaper doesn't reap memory read by vhost

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Message-ID: <20160619215258.GA2110@dhcp22.suse.cz>
Date:	Sun, 19 Jun 2016 23:52:58 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Vladimir Davydov <vdavydov@...allels.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-mm@...ck.org, virtualization@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] vhost, mm: make sure that oom_reaper doesn't reap
 memory read by vhost

On Sun 19-06-16 23:35:43, Michal Hocko wrote:
> On Sat 18-06-16 03:09:02, Michael S. Tsirkin wrote:
> > On Fri, Jun 17, 2016 at 11:00:17AM +0200, Michal Hocko wrote:
[...]
> > >  /*
> > > + * A safe variant of __get_user for for use_mm() users to have a
> > > + * gurantee that the address space wasn't reaped in the background
> > > + */
> > > +#define __get_user_mm(mm, x, ptr)				\
> > > +({								\
> > > +	int ___gu_err = __get_user(x, ptr);			\
> > > +	if (!___gu_err && test_bit(MMF_UNSTABLE, &mm->flags))	\
> > 
> > test_bit is somewhat expensive. See my old mail
> > 	x86/bitops: implement __test_bit
> 
> Do you have a msg_id?

Found it
http://lkml.kernel.org/r/1440776707-22016-1-git-send-email-mst@redhat.com
-- 
Michal Hocko
SUSE Labs