Return-Path: Received: from mx2.suse.de ([195.135.220.15]:38015 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750921AbdBCPno (ORCPT ); Fri, 3 Feb 2017 10:43:44 -0500 Date: Fri, 3 Feb 2017 16:32:22 +0100 From: Michal Hocko To: "Theodore Ts'o" Cc: Jan Kara , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Dave Chinner , djwong@kernel.org, Chris Mason , David Sterba , ceph-devel@vger.kernel.org, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, logfs@logfs.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mtd@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, linux-f2fs-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, LKML Subject: Re: [PATCH 8/8] Revert "ext4: fix wrong gfp type under transaction" Message-ID: <20170203153222.GH19325@dhcp22.suse.cz> References: <20170117161618.GT19699@dhcp22.suse.cz> <20170117172925.GA2486@quack2.suse.cz> <20170119083956.GE30786@dhcp22.suse.cz> <20170119092236.GC2565@quack2.suse.cz> <20170119094405.GK30786@dhcp22.suse.cz> <20170126074455.GC8456@dhcp22.suse.cz> <20170127061318.xd2qxashbl4dajez@thunk.org> <20170127093735.GB4143@dhcp22.suse.cz> <20170127164042.2o3bnyopihcb224g@thunk.org> <20170130081210.GD8443@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170130081210.GD8443@dhcp22.suse.cz> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon 30-01-17 09:12:10, Michal Hocko wrote: > On Fri 27-01-17 11:40:42, Theodore Ts'o wrote: > > On Fri, Jan 27, 2017 at 10:37:35AM +0100, Michal Hocko wrote: > > > If this ever turn out to be a problem and with the vmapped stacks we > > > have good chances to get a proper stack traces on a potential overflow > > > we can add the scope API around the problematic code path with the > > > explanation why it is needed. > > > > Yeah, or maybe we can automate it? Can the reclaim code check how > > much stack space is left and do the right thing automatically? > > I am not sure how to do that. Checking for some magic value sounds quite > fragile to me. It also sounds a bit strange to focus only on the reclaim > while other code paths might suffer from the same problem. > > What is actually the deepest possible call chain from the slab reclaim > where I stopped? I have tried to follow that path but hit the callback > wall quite early. > > > The reason why I'm nervous is that nojournal mode is not a common > > configuration, and "wait until production systems start failing" is > > not a strategy that I or many SRE-types find.... comforting. > > I understand that but I would be much more happier if we did the > decision based on the actual data rather than a fear something would > break down. ping on this. I would really like to move forward here and target 4.11 merge window. Is your concern so serious to block this patch? -- Michal Hocko SUSE Labs