Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section

[Vlastimil Babka]

On 04/10/2017 01:03 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> device memory hotplug hooks into regular memory hotplug only half way.
> It needs memory sections to track struct pages but there is no
> need/desire to associate those sections with memory blocks and export
> them to the userspace via sysfs because they cannot be onlined anyway.
> 
> This is currently expressed by for_device argument to arch_add_memory
> which then makes sure to associate the given memory range with
> ZONE_DEVICE. register_new_memory then relies on is_zone_device_section
> to distinguish special memory hotplug from the regular one. While this
> works now, later patches in this series want to move __add_zone outside
> of arch_add_memory path so we have to come up with something else.
> 
> Add want_memblock down the __add_pages path and use it to control
> whether the section->memblock association should be done. arch_add_memory
> then just trivially want memblock for everything but for_device hotplug.
> 
> remove_memory_section doesn't need is_zone_device_section either. We can
> simply skip all the memblock specific cleanup if there is no memblock
> for the given section.
> 
> This shouldn't introduce any functional change.
> 
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

For the fixed version:

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>