Re: [PATCH 0/2] mm, oom: fix oom_reaper fallouts

[Michal Hocko]

On Mon 07-08-17 22:28:27, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > Hi,
> > there are two issues this patch series attempts to fix. First one is
> > something that has been broken since MMF_UNSTABLE flag introduction
> > and I guess we should backport it stable trees (patch 1). The other
> > issue has been brought up by Wenwei Tao and Tetsuo Handa has created
> > a test case to trigger it very reliably. I am not yet sure this is a
> > stable material because the test case is rather artificial. If there is
> > a demand for the stable backport I will prepare it, of course, though.
> > 
> > I hope I've done the second patch correctly but I would definitely
> > appreciate some more eyes on it. Hence CCing Andrea and Kirill. My
> > previous attempt with some more context was posted here
> > http://lkml.kernel.org/r/20170803135902.31977-1-mhocko@xxxxxxxxxx
> > 
> > My testing didn't show anything unusual with these two applied on top of
> > the mmotm tree.
> 
> I really don't like your likely/unlikely speculation.

Have you seen any non artificial workload triggering this? Look, I am
not going to argue about how likely this is or not. I've said I am
willing to do backports if there is a demand but please do realize that
this is not a trivial change to backport pre 4.9 kernels would require
MMF_UNSTABLE to be backported as well. This all can be discussed
after the merge so can we focus on the review now rather than any
distractions?

Also please note that while writing zeros is certainly bad any integrity
assumptions are basically off when an application gets killed
unexpectedly while performing an IO.
-- 
Michal Hocko
SUSE Labs