Re: [PATCH v8 4/8] mm,memory_hotplug: Allocate memmap from the added memory range

[David Hildenbrand]

On 16.04.21 12:37, Oscar Salvador wrote:
> On Fri, Apr 16, 2021 at 12:33:34PM +0200, David Hildenbrand wrote:
> > IIRC, we have to add the zero shadow first, before touching the memory. This
> > is also what mm/memremap.c does.
> >
> > In mhp_deinit_memmap_on_memory(), you already remove in the proper
> > (reversed) order :)
>
> But looking at online_pages(), we do it after the
> move_pfn_range_to_zone(), right? AFAIK (I might be well wrong here),
> memory_notify() will eventually call kasan_add_zero_shadow? So that
> comes after the move_pfn_range_to_zone? Or is my understanding
> incorrect?

The thing is: move_pfn_range_to_zone() in case of ordinary 
online_pages() won't touch the pages but only the memmap. The memmap has 
a proper kasan shadow already. Pages won't be touched before exposing 
them to the page allocator via generic_online_pages().

This is different in this case :)

--
Thanks,

David / dhildenb