From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757600AbcCaPLh (ORCPT ); Thu, 31 Mar 2016 11:11:37 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33244 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757083AbcCaPLc (ORCPT ); Thu, 31 Mar 2016 11:11:32 -0400 Date: Thu, 31 Mar 2016 17:11:25 +0200 From: Michal Hocko To: Tetsuo Handa Cc: rientjes@google.com, linux-mm@kvack.org, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm, oom: move GFP_NOFS check to out_of_memory Message-ID: <20160331151124.GG27831@dhcp22.suse.cz> References: <1459258055-1173-1-git-send-email-mhocko@kernel.org> <20160330094750.GH30729@dhcp22.suse.cz> <201603302046.CBJ39064.LFVQOHOOJtFSMF@I-love.SAKURA.ne.jp> <20160330121141.GD4324@dhcp22.suse.cz> <201603312056.BJH95312.HOQFFSVMJOLtOF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201603312056.BJH95312.HOQFFSVMJOLtOF@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 31-03-16 20:56:23, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Wed 30-03-16 20:46:48, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > > > On Tue 29-03-16 15:13:54, David Rientjes wrote: > > > > > On Tue, 29 Mar 2016, Michal Hocko wrote: > > > > > > > > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > > > > > index 86349586eacb..1c2b7a82f0c4 100644 > > > > > > --- a/mm/oom_kill.c > > > > > > +++ b/mm/oom_kill.c > > > > > > @@ -876,6 +876,10 @@ bool out_of_memory(struct oom_control *oc) > > > > > > return true; > > > > > > } > > > > > > > > > > > > + /* The OOM killer does not compensate for IO-less reclaim. */ > > > > > > + if (!(oc->gfp_mask & __GFP_FS)) > > > > > > + return true; > > > > > > + > > > > > > This patch will disable pagefault_out_of_memory() because currently > > > pagefault_out_of_memory() is passing oc->gfp_mask == 0. > > > > > > Because of current behavior, calling oom notifiers from !__GFP_FS seems > > > to be safe. > > > > You are right! I have completely missed that and thought we were > > providing GFP_KERNEL there. So we have two choices. Either we do > > use GFP_KERNEL (same as we do for sysrq+f) or we special case > > pagefault_out_of_memory in some way. The second option seems to be safer > > because the gfp_mask has to contain at least ___GFP_DIRECT_RECLAIM to > > trigger the OOM path. > > Oops, I missed that this patch also disables out_of_memory() for !__GFP_FS && > __GFP_NOFAIL allocation requests. True. The following should take care of that: diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 54aa4ec06889..32d8210b8773 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -882,7 +882,7 @@ bool out_of_memory(struct oom_control *oc) * make sure exclude 0 mask - all other users should have at least * ___GFP_DIRECT_RECLAIM to get here. */ - if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS)) + if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL))) return true; /* Thanks for spotting this! [...] -- Michal Hocko SUSE Labs