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Message-ID: <20170203153222.GH19325@dhcp22.suse.cz> Date: Fri, 3 Feb 2017 16:32:22 +0100 From: Michal Hocko <mhocko@...nel.org> To: Theodore Ts'o <tytso@....edu> Cc: Jan Kara <jack@...e.cz>, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Dave Chinner <david@...morbit.com>, djwong@...nel.org, Chris Mason <clm@...com>, David Sterba <dsterba@...e.cz>, ceph-devel@...r.kernel.org, cluster-devel@...hat.com, linux-nfs@...r.kernel.org, logfs@...fs.org, linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-mtd@...ts.infradead.org, reiserfs-devel@...r.kernel.org, linux-ntfs-dev@...ts.sourceforge.net, linux-f2fs-devel@...ts.sourceforge.net, linux-afs@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 8/8] Revert "ext4: fix wrong gfp type under transaction" 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
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