Re: [PATCH 0/6] mm: make movable onlining suck less

[Michal Hocko]

On Wed 05-04-17 23:02:14, Michal Hocko wrote:
[...]
> OK, I was staring into the code and I guess I finally understand what is
> going on here. Looking at arch_add_memory->...->register_mem_sect_under_node
> was just misleading. I am still not 100% sure why but we try to do the
> same thing later from register_one_node->link_mem_sections for nodes
> which were offline. I should have noticed this path before. And here
> is the difference from the previous code. We are past arch_add_memory
> and that path used to do __add_zone which among other things will also
> resize node boundaries. I am not doing that anymore because I postpone
> that to the onlining phase. Jeez this code is so convoluted my head
> spins.
> 
> I am not really sure how to fix this. I suspect register_mem_sect_under_node
> should just ignore the online state of the node. But I wouldn't
> be all that surprised if this had some subtle reason as well. An
> alternative would be to actually move register_mem_sect_under_node out
> of register_new_memory and move it up the call stack, most probably to
> add_memory_resource. We have the range and can map it to the memblock
> and so will not rely on the node range. I will sleep over it and
> hopefully come up with something tomorrow.

OK, so this is the most sensible way I was able to come up with. I
didn't get to test it yet but from the above analysis it should work.
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