Re: [PATCH] mm/memory_hotplug: build zonelist for managed_zone

[Wei Yang <richard.weiyang@gmail.com>]

On Thu, Jan 27, 2022 at 09:28:17AM +0100, Michal Hocko wrote:
>On Thu 27-01-22 01:20:23, Wei Yang wrote:
>> During memory hotplug, when online/offline a zone, we need to rebuild
>> the zonelist for all node. There are two checks to decide whether a zone
>> would be added to zonelist:
>> 
>>   * one in online_pages/offline_pages to decide necessity
>>   * one in build_zonerefs_node to do real add
>> 
>> Currently we use different criteria at these two places, which is
>> different from the original behavior.
>> 
>> Originally during memory hotplug, zonelist is re-built when zone hasn't
>> been populated. This in introduced in 'commit 6811378e7d8b ("[PATCH]
>> wait_table and zonelist initializing for memory hotadd: update zonelists")'.
>> And at that moment, build_zonelists_node() also use populated_zone() to
>> decide whether the zone should be added to zonelist.
>> 
>> While in 'commit 6aa303defb74 ("mm, vmscan: only allocate and reclaim
>> from zones with pages managed by the buddy allocator")',
>> build_zonelists_node() changed to use managed_zone() to add zonelist.
>> But we still use populated_zone() to decide the necessity.
>> 
>> This patch restore the original behavior by using the same criteria to
>> add a zone in zonelist during memory hotplug.
>
>Why?
>

In case we online a populated zone, but not managed. Then this zone will not
be in zonelist. Right?

-- 
Wei Yang
Help you, Help me