Re: [PATCH] mm: don't rely on system state to detect hot-plug operations

[Laurent Dufour]

Le 10/09/2020 à 09:23, Michal Hocko a écrit :
> On Wed 09-09-20 18:07:15, Laurent Dufour wrote:
> > Le 09/09/2020 à 12:59, Michal Hocko a écrit :
> > > On Wed 09-09-20 11:21:58, Laurent Dufour wrote:
> [...]
> > > > For the point a, using the enum allows to know in
> > > > register_mem_sect_under_node() if the link operation is due to a hotplug
> > > > operation or done at boot time.
> > >
> > > Yes, but let me repeat. We have a mess here and different paths check
> > > for the very same condition by different ways. We need to unify those.
> >
> > What are you suggesting to unify these checks (using a MP_* enum as
> > suggested by David, something else)?
>
> We do have system_state check spread at different places. I would use
> this one and wrap it behind a helper. Or have I missed any reason why
> that wouldn't work for this case?

That would not work in that case because memory can be hot-added at the 
SYSTEM_SCHEDULING system state and the regular memory is also registered at that 
system state too. So system state is not enough to discriminate between the both.

I think I'll go with the option suggested by David, replacing the enum 
memmap_context a new enum memplug_context and pass that context to 
register_mem_sect_under_node() so that function will known when node id should 
be checked or not.

Cheers,
Laurent.