[PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory

[KOSAKI Motohiro]

> I think it again, and found that this check is necessary. Because we only
> lock memory hotplug when offlining pages. Here is the steps to offline and
> remove memory:
>
> 1. lock memory hotplug
> 2. offline a memory section
> 3. unlock memory hotplug
> 4. repeat 1-3 to offline all memory sections
> 5. lock memory hotplug
> 6. remove memory
> 7. unlock memory hotplug
>
> All memory sections must be offlined before removing memory. But we don't
> hold
> the lock in the whole operation. So we should check whether all memory
> sections
> are offlined before step6.

You should describe the race scenario in the patch description. OK?