Re: [PATCH v2 0/2] mm: Memory offlining + page isolation cleanups

[Michal Hocko <mhocko@kernel.org>]

On Tue 22-10-19 08:52:28, David Hildenbrand wrote:
> On 21.10.19 19:23, David Hildenbrand wrote:
> > Two cleanups that popped up while working on (and discussing) virtio-mem:
> >   https://lkml.org/lkml/2019/9/19/463
> > 
> > Tested with DIMMs on x86.
> > 
> > As discussed with michal in v1, I'll soon look into removing the use
> > of PG_reserved during memory onlining completely - most probably
> > disallowing to offline memory blocks with holes, cleaning up the
> > onlining+offlining code.
> 
> BTW, I remember that ZONE_DEVICE pages are still required to be set
> PG_reserved. That has to be sorted out first.

Do they?

> I remember that somebody was
> working on it a while ago but didn't hear about that again. Will look into
> that as well - should be as easy as adding a zone check (if there isn't a
> pfn_to_online_page() check already). But of course, there might be special
> cases ....

I remember Alexander didn't want to change the PageReserved handling
because he was worried about unforeseeable side effects. I have a vague
recollection he (or maybe Dan) has promissed some follow up clean ups
which didn't seem to materialize.
-- 
Michal Hocko
SUSE Labs