From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752256AbdAZNKS (ORCPT ); Thu, 26 Jan 2017 08:10:18 -0500 Received: from www62.your-server.de ([213.133.104.62]:47956 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877AbdAZNKQ (ORCPT ); Thu, 26 Jan 2017 08:10:16 -0500 Message-ID: <5889F52E.7030602@iogearbox.net> Date: Thu, 26 Jan 2017 14:10:06 +0100 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Michal Hocko CC: Alexei Starovoitov , Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , linux-mm , LKML , "netdev@vger.kernel.org" , marcelo.leitner@gmail.com Subject: Re: [PATCH 0/6 v3] kvmalloc References: <588907AA.1020704@iogearbox.net> <20170126074354.GB8456@dhcp22.suse.cz> <5889C331.7020101@iogearbox.net> <20170126100802.GF6590@dhcp22.suse.cz> <5889DEA3.7040106@iogearbox.net> <20170126115833.GI6590@dhcp22.suse.cz> In-Reply-To: <20170126115833.GI6590@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/26/2017 12:58 PM, Michal Hocko wrote: > On Thu 26-01-17 12:33:55, Daniel Borkmann wrote: >> On 01/26/2017 11:08 AM, Michal Hocko wrote: > [...] >>> If you disagree I can drop the bpf part of course... >> >> If we could consolidate these spots with kvmalloc() eventually, I'm >> all for it. But even if __GFP_NORETRY is not covered down to all >> possible paths, it kind of does have an effect already of saying >> 'don't try too hard', so would it be harmful to still keep that for >> now? If it's not, I'd personally prefer to just leave it as is until >> there's some form of support by kvmalloc() and friends. > > Well, you can use kvmalloc(size, GFP_KERNEL|__GFP_NORETRY). It is not > disallowed. It is not _supported_ which means that if it doesn't work as > you expect you are on your own. Which is actually the situation right > now as well. But I still think that this is just not right thing to do. > Even though it might happen to work in some cases it gives a false > impression of a solution. So I would rather go with Hmm. 'On my own' means, we could potentially BUG somewhere down the vmalloc implementation, etc, presumably? So it might in-fact be harmful to pass that, right? > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 8697f43cf93c..a6dc4d596f14 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -53,6 +53,11 @@ void bpf_register_map_type(struct bpf_map_type_list *tl) > > void *bpf_map_area_alloc(size_t size) > { > + /* > + * FIXME: we would really like to not trigger the OOM killer and rather > + * fail instead. This is not supported right now. Please nag MM people > + * if these OOM start bothering people. > + */ Ok, I know this is out of scope for this series, but since i) this is _not_ the _only_ spot right now which has such a construct and ii) I am already kind of nagging a bit ;), my question would be, what would it take to start supporting it? > return kvzalloc(size, GFP_USER); > } Thanks, Daniel