Re: [PATCH 1/2] mm, memory_hotplug: display allowed zones in the preferred ordering

[Joonsoo Kim]

On Thu, Jun 29, 2017 at 09:35:08AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> Prior to "mm, memory_hotplug: do not associate hotadded memory to zones
> until online" we used to allow to change the valid zone types of a
> memory block if it is adjacent to a different zone type. This fact was
> reflected in memoryNN/valid_zones by the ordering of printed zones.
> The first one was default (echo online > memoryNN/state) and the other
> one could be onlined explicitly by online_{movable,kernel}. This
> behavior was removed by the said patch and as such the ordering was
> not all that important. In most cases a kernel zone would be default
> anyway. The only exception is movable_node handled by "mm,
> memory_hotplug: support movable_node for hotpluggable nodes".
> 
> Let's reintroduce this behavior again because later patch will remove
> the zone overlap restriction and so user will be allowed to online
> kernel resp. movable block regardless of its placement. Original
> behavior will then become significant again because it would be
> non-trivial for users to see what is the default zone to online into.
> 
> Implementation is really simple. Pull out zone selection out of
> move_pfn_range into zone_for_pfn_range helper and use it in
> show_valid_zones to display the zone for default onlining and then
> both kernel and movable if they are allowed. Default online zone is not
> duplicated.
> 
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> 

Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Thanks.