Re: [PATCH] mm/hmm: Fix bad subpage pointer in try_to_unmap_one

[Andrew Morton]

On Mon, 15 Jul 2019 17:38:04 -0700 Ralph Campbell <rcampbell@xxxxxxxxxx> wrote:

> I'm not surprised at the confusion. It took me quite awhile to 
> understand how migrate_vma() works with ZONE_DEVICE private memory.
>
> ...
> 
> I see Christoph Hellwig got confused by this too [1].

While making such discoveries, please prepare a patch which adds
comments which will help the next poor soul!