From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755176AbeDTNtH (ORCPT ); Fri, 20 Apr 2018 09:49:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:54801 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754913AbeDTNtG (ORCPT ); Fri, 20 Apr 2018 09:49:06 -0400 Date: Fri, 20 Apr 2018 15:49:01 +0200 From: Michal Hocko To: Matthew Wilcox Cc: Mikulas Patocka , 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 Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM Message-ID: <20180420134901.GB17484@dhcp22.suse.cz> References: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> <20180418.134651.2225112489265654270.davem@davemloft.net> <20180420130852.GC16083@dhcp22.suse.cz> <20180420134136.GD10788@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180420134136.GD10788@bombadil.infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 20-04-18 06:41:36, Matthew Wilcox wrote: > On Fri, Apr 20, 2018 at 03:08:52PM +0200, Michal Hocko wrote: > > > In order to detect these bugs reliably I submit this patch that changes > > > kvmalloc to always use vmalloc if CONFIG_DEBUG_VM is turned on. > > > > No way. This is just wrong! First of all, you will explode most likely > > on many allocations of small sizes. Second, CONFIG_DEBUG_VM tends to be > > enabled quite often. > > I think it'll still suit Mikulas' debugging needs if we always use > vmalloc for sizes above PAGE_SIZE? Even if that was the case then this doesn't sounds like CONFIG_DEBUG_VM material. We do not want a completely different behavior when the config is enabled. If we really need some better fallback testing coverage then the fault injection, as suggested by Vlastimil, sounds much more reasonable to me -- Michal Hocko SUSE Labs