Re: [PATCH v1 2/4] mm/memory_hotplug: Handle unaligned start and nr_pages in online_pages_blocks()

[Michal Hocko]

On Wed 14-08-19 16:17:03, David Hildenbrand wrote:
> On 14.08.19 16:08, Michal Hocko wrote:
> > On Fri 09-08-19 14:56:59, David Hildenbrand wrote:
> >> Take care of nr_pages not being a power of two and start not being
> >> properly aligned. Essentially, what walk_system_ram_range() could provide
> >> to us. get_order() will round-up in case it's not a power of two.
> >>
> >> This should only apply to memory blocks that contain strange memory
> >> resources (especially with holes), not to ordinary DIMMs.
> > 
> > I would really like to see an example of such setup before making the
> > code hard to read. Because I am not really sure something like that
> > exists at all.
> 
> I don't have a real-live example at hand (founds this while exploring
> the code), however, the linked commit changed it without stating why it
> would be safe to do so.

Then just drop the change. It is making the code a real head scratcher,
and more so after the next patch. I am pretty sure that things would
easily and quickly blow up if we had ranges like that.
-- 
Michal Hocko
SUSE Labs