From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423704AbcFMON2 (ORCPT ); Mon, 13 Jun 2016 10:13:28 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:32950 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423255AbcFMON1 (ORCPT ); Mon, 13 Jun 2016 10:13:27 -0400 Date: Mon, 13 Jun 2016 16:13:24 +0200 From: Michal Hocko To: linux-mm@kvack.org Cc: Tetsuo Handa , David Rientjes , Oleg Nesterov , Vladimir Davydov , Andrew Morton , LKML Subject: Re: [PATCH 0/10 -v4] Handle oom bypass more gracefully Message-ID: <20160613141324.GK6518@dhcp22.suse.cz> References: <1465473137-22531-1-git-send-email-mhocko@kernel.org> <20160613112348.GC6518@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160613112348.GC6518@dhcp22.suse.cz> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 13-06-16 13:23:48, Michal Hocko wrote: > On Thu 09-06-16 13:52:07, Michal Hocko wrote: > > I would like to explore ways how to remove kthreads (use_mm) special > > case. It shouldn't be that hard, we just have to teach the page fault > > handler to recognize oom victim mm and enforce EFAULT for kthreads > > which have borrowed that mm. > > So I was trying to come up with solution for this which would require to > hook into the pagefault an enforce EFAULT when the mm is being reaped > by the oom_repaer. Not hard but then I have checked the current users > and none of them is really needing to read from the userspace (aka > copy_from_user/get_user). So we actually do not need to do anything > special. As pointed out by Tetsuo [1] vhost does realy on copy_from_user. I just missed that. So scratch this. I will revisit a potential solution for this but that would be outside of this series scope. [1] http://lkml.kernel.org/r/201606132252.IAE00593.OJQSFMtVFOLHOF@I-love.SAKURA.ne.jp -- Michal Hocko SUSE Labs