Re: [PATCH 0/6 v3] kvmalloc
From: Michal Hocko
Date: Thu Jan 26 2017 - 09:14:06 EST
On Thu 26-01-17 14:40:04, Michal Hocko wrote:
> On Thu 26-01-17 14:10:06, Daniel Borkmann wrote:
> > On 01/26/2017 12:58 PM, Michal Hocko wrote:
> > > On Thu 26-01-17 12:33:55, Daniel Borkmann wrote:
> > > > On 01/26/2017 11:08 AM, Michal Hocko wrote:
> > > [...]
> > > > > If you disagree I can drop the bpf part of course...
> > > >
> > > > If we could consolidate these spots with kvmalloc() eventually, I'm
> > > > all for it. But even if __GFP_NORETRY is not covered down to all
> > > > possible paths, it kind of does have an effect already of saying
> > > > 'don't try too hard', so would it be harmful to still keep that for
> > > > now? If it's not, I'd personally prefer to just leave it as is until
> > > > there's some form of support by kvmalloc() and friends.
> > >
> > > Well, you can use kvmalloc(size, GFP_KERNEL|__GFP_NORETRY). It is not
> > > disallowed. It is not _supported_ which means that if it doesn't work as
> > > you expect you are on your own. Which is actually the situation right
> > > now as well. But I still think that this is just not right thing to do.
> > > Even though it might happen to work in some cases it gives a false
> > > impression of a solution. So I would rather go with
> > Hmm. 'On my own' means, we could potentially BUG somewhere down the
> > vmalloc implementation, etc, presumably? So it might in-fact be
> > harmful to pass that, right?
> No it would mean that it might eventually hit the behavior which you are
> trying to avoid - in other words it may invoke OOM killer even though
> __GFP_NORETRY means giving up before any system wide disruptive actions
> a re taken.
I will separate both bpf and netfilter hunks into its own patch with the
clarification. Does the following look better?