Re: [PATCH RFC v3 8/9] mm/memory_hotplug: Introduce offline_and_remove_memory()

[Michal Hocko]

On Thu 19-09-19 16:22:27, David Hildenbrand wrote:
> virtio-mem wants to offline and remove a memory block once it unplugged
> all subblocks (e.g., using alloc_contig_range()). Let's provide
> an interface to do that from a driver. virtio-mem already supports to
> offline partially unplugged memory blocks. Offlining a fully unplugged
> memory block will not require to migrate any pages. All unplugged
> subblocks are PageOffline() and have a reference count of 0 - so
> offlining code will simply skip them.
> 
> All we need an interface to trigger the "offlining" and the removing in a
> single operation - to make sure the memory block cannot get onlined by
> user space again before it gets removed.
> 
> To keep things simple, allow to only work on a single memory block.

Without a user it is not really clear why do we need this interface.
I am also not really sure why do you want/need to control beyond the
offlining stage. Care to explain some more?
-- 
Michal Hocko
SUSE Labs