From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751465AbeECRkz (ORCPT ); Thu, 3 May 2018 13:40:55 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45044 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751007AbeECRku (ORCPT ); Thu, 3 May 2018 13:40:50 -0400 Date: Thu, 3 May 2018 13:40:48 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: John Stoffel cc: Andrew@stoffel.org, dm-devel@redhat.com, eric.dumazet@gmail.com, mst@redhat.com, netdev@vger.kernel.org, jasowang@redhat.com, Randy Dunlap , linux-kernel@vger.kernel.org, Matthew Wilcox , Hocko , James Bottomley , Michal@stoffel.org, edumazet@google.com, linux-mm@kvack.org, David Rientjes , Morton , virtualization@lists.linux-foundation.org, David Miller , Vlastimil Babka Subject: Re: [dm-devel] [PATCH v5] fault-injection: introduce kvmalloc fallback options In-Reply-To: <23273.48986.516559.317965@quad.stoffel.home> Message-ID: References: <20180421144757.GC14610@bombadil.infradead.org> <20180424173836.GR17484@dhcp22.suse.cz> <1114eda5-9b1f-4db8-2090-556b4a37c532@infradead.org> <1524694663.4100.21.camel@HansenPartnership.com> <1524697697.4100.23.camel@HansenPartnership.com> <23266.8532.619051.784274@quad.stoffel.home> <23271.24580.695738.853532@quad.stoffel.home> <23273.48986.516559.317965@quad.stoffel.home> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2 May 2018, John Stoffel wrote: > You miss my point, which is that there's no explanation of what the > difference is between SLAB and SLUB and which I should choose. The > same goes here. If the KConfig option doesn't give useful info, it's > useless. So what, we could write explamantion of that option. > >> Now I also think that Linus has the right idea to not just sprinkle > >> BUG_ONs into the code, just dump and oops and keep going if you can. > >> If it's a filesystem or a device, turn it read only so that people > >> notice right away. > > Mikulas> This vmalloc fallback is similar to > Mikulas> CONFIG_DEBUG_KOBJECT_RELEASE. CONFIG_DEBUG_KOBJECT_RELEASE > Mikulas> changes the behavior of kobject_put in order to cause > Mikulas> deliberate crashes (that wouldn't happen otherwise) in > Mikulas> drivers that misuse kobject_put. In the same sense, we want > Mikulas> to cause deliberate crashes (that wouldn't happen otherwise) > Mikulas> in drivers that misuse kvmalloc. > > Mikulas> The crashes will only happen in debugging kernels, not in > Mikulas> production kernels. > > Says you. What about people or distros that enable it > unconditionally? They're going to get all kinds of reports and then > turn it off again. Crashing the system isn't the answer here. I've made that kvmalloc bug too (in the function dm_integrity_free_journal_scatterlist). I'd much rather like if the kernel crashed (because then - I would fix the bug). The kernel didn't crash and the bug sneaked into the official linux tree, where may be causing random crashes for other users. Mikulas