From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 0241C6B0005 for ; Mon, 23 Apr 2018 20:25:22 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id a125so12321228qkd.4 for ; Mon, 23 Apr 2018 17:25:21 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id n17si678138qvg.289.2018.04.23.17.25.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 23 Apr 2018 17:25:20 -0700 (PDT) Date: Mon, 23 Apr 2018 20:25:15 -0400 (EDT) From: Mikulas Patocka Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM In-Reply-To: <20180423151545.GU17484@dhcp22.suse.cz> Message-ID: References: <20180418.134651.2225112489265654270.davem@davemloft.net> <20180420130852.GC16083@dhcp22.suse.cz> <20180420210200.GH10788@bombadil.infradead.org> <20180421144757.GC14610@bombadil.infradead.org> <20180423151545.GU17484@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Matthew Wilcox , David Miller , Andrew Morton , linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.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 Apr 2018, Michal Hocko wrote: > On Mon 23-04-18 10:06:08, Mikulas Patocka wrote: > > > > > He didn't want to fix vmalloc(GFP_NOIO) > > > > > > I don't remember that conversation, so I don't know whether I agree with > > > his reasoning or not. But we are supposed to be moving away from GFP_NOIO > > > towards marking regions with memalloc_noio_save() / restore. If you do > > > that, you won't need vmalloc(GFP_NOIO). > > > > He said the same thing a year ago. And there was small progress. 6 out of > > 27 __vmalloc calls were converted to memalloc_noio_save in a year - 5 in > > infiniband and 1 in btrfs. (the whole discussion is here > > http://lkml.iu.edu/hypermail/linux/kernel/1706.3/04681.html ) > > Well this is not that easy. It requires a cooperation from maintainers. > I can only do as much. I've posted patches in the past and actively > bringing up this topic at LSFMM last two years... You're right - but you have chosen the uneasy path. Fixing __vmalloc code is easy and it doesn't require cooperation with maintainers. > > He refuses 15-line patch to fix GFP_NOIO bug because he believes that in 4 > > years, the kernel will be refactored and GFP_NOIO will be eliminated. Why > > does he have veto over this part of the code? I'd much rather argue with > > people who have constructive comments about fixing bugs than with him. > > I didn't NACK the patch AFAIR. I've said it is not a good idea longterm. > I would be much more willing to change my mind if you would back your > patch by a real bug report. Hacks are acceptable when we have a real > issue in hands. But if we want to fix potential issue then better make > it properly. Developers should fix bugs in advance, not to wait until a crash hapens, is analyzed and reported. What's the problem with 15-line hack? Is the problem that kernel developers would feel depressed when looking the source code? Other than harming developers' feelings, I don't see what kind of damange could that piece of code do. Mikulas