On Tue, Mar 24, 2020 at 7:32 AM John Hubbard <jhubbard@xxxxxxxxxx> wrote:
>
> On 3/23/20 12:34 AM, Michal Hocko wrote:
> > On Sun 22-03-20 21:57:07, Pingfan Liu wrote:
> >> For zone_device, migration can only happen on is_device_private_page(page).
> >> Correct the logic in try_to_unmap_one().
> >
> > Maybe it is just me lacking knowledge in the zone_device ZOO. But
> > this really deserves a much more detailed explanation IMHO. It seems
> > a5430dda8a3a ("mm/migrate: support un-addressable ZONE_DEVICE page in
> > migration") deliberately made the decision to allow unmapping these
> > pages? Is the check just wrong, inncomplete? Why?
> >
> > What is the real user visible problem here?
> >
>
> I was going to guess that someone was having trouble with the behavior on
> non-device-private ZONE_DEVICE pages, but...I am also at a loss as to
> what triggered this patch. So, I have the exact same questions as Michal,
> plus really wondering what tests you are running, and on what hardware config.
:), please see my reply to Michal.
>
> It's hard to get the right CC's, but probably Dan Williams and Ralph Campbell
> should also be added, if you are sure you need this. (I'm adding them now.)
Appreciate you to do that. In fact, I am not sure about some detail,
and hope someone can correct me if I make mistake.
Thanks,
Pingfan
