Re: [PATCH] mm/memory_hotplug: Fix leftover use of struct page during hotplug

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On Wed 23-05-18 15:54:03, Oscar Salvador wrote:
> On Thu, May 10, 2018 at 02:02:00PM +0200, Michal Hocko wrote:
> > On Fri 04-05-18 17:50:51, Jonathan Cameron wrote:
> > [...]
> > > Exact path to the problem is as follows:
> > > 
> > > mm/memory_hotplug.c : add_memory_resource
> > > The node is not online so we enter the
> > > if (new_node) twice, on the second such block there is a call to
> > > link_mem_sections which calls into
> > > drivers/node.c: link_mem_sections which calls
> > > drivers/node.c: register_mem_sect_under_node which calls
> > > get_nid_for_pfn and keeps trying until the output of that matches
> > > the expected node (passed all the way down from add_memory_resource)
> > 
> > I am sorry but I am still confused. Why don't we create sysfs files from
> > __add_pages
> >   __add_section
> >     hotplug_memory_register
> >       register_mem_sect_under_node
> 
> IIUC the problem is that at the point we are calling register_mem_sect_under_node(),
> pages are not initialized yet.

Ahh, of course. I keep forgetting the latest hotplug optimizations that
we do not initialize even nid for struct pages. Which is the whole point
of this patch... Sigh.

I think the whole sysfs initialization needs to be refactored to be more
sane. The way how we depend on things silently is just not maintainable.

Thanks!
-- 
Michal Hocko
SUSE Labs




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