From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 81F0E6B0007 for ; Mon, 23 Apr 2018 11:10:20 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id z7-v6so18981217wrg.11 for ; Mon, 23 Apr 2018 08:10:20 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f16si1100086edf.188.2018.04.23.08.10.18 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 23 Apr 2018 08:10:19 -0700 (PDT) Date: Mon, 23 Apr 2018 09:10:15 -0600 From: Michal Hocko Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM Message-ID: <20180423151015.GT17484@dhcp22.suse.cz> References: <20180418.134651.2225112489265654270.davem@davemloft.net> <20180420130852.GC16083@dhcp22.suse.cz> <20180420210200.GH10788@bombadil.infradead.org> <20180421144757.GC14610@bombadil.infradead.org> <20180422130356.GG17484@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Mikulas Patocka Cc: Matthew Wilcox , David Miller , Andrew Morton , linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.com, bhutchings@solarflare.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, Vlastimil Babka On Mon 23-04-18 10:24:02, Mikulas Patocka wrote: [...] I am not going to comment on your continuous accusations. We can discuss patches but general rants make very limited sense. > > > > I already said that we can change it from CONFIG_DEBUG_VM to > > > > CONFIG_DEBUG_SG - or to whatever other option you may want, just to make > > > > sure that it is enabled in distro debug kernels by default. > > > > > > Yes, and I think that's the right idea. So send a v2 and ignore the > > > replies that are clearly relating to an earlier version of the patch. > > > Not everybody reads every mail in the thread before responding to one they > > > find interesting. Yes, ideally, one would, but sometimes one doesn't. > > > > And look here. This is yet another ad-hoc idea. We have many users of > > kvmalloc which have no relation to SG, yet you are going to control > > their behavior by CONFIG_DEBUG_SG? No way! (yeah evil again) > > Why aren't you constructive and pick up pick up the CONFIG flag? Because config doesn't make that much of a sense. You do not want a permanent vmalloc fallback unconditionally. Debugging option which changes the behavior completely is not useful IMNHO. Besides that who is going to enable it? > > Really, we have a fault injection framework and this sounds like > > something to hook in there. > > The testing people won't set it up. They install the "kernel-debug" > package and run the tests in it. > > If you introduce a hidden option that no one knows about, no one will use > it. then make sure people know about it. Fuzzers already do test fault injections. -- Michal Hocko SUSE Labs