[PATCH v6 20/26] mm/mlock: Skip ZONE_DEVICE PMDs during mlock

[Dan Williams]

Alistair Popple wrote:
> At present mlock skips ptes mapping ZONE_DEVICE pages. A future change
> to remove pmd_devmap will allow pmd_trans_huge_lock() to return
> ZONE_DEVICE folios so make sure we continue to skip those.
> 
> Signed-off-by: Alistair Popple <apopple at nvidia.com>
> Acked-by: David Hildenbrand <david at redhat.com>

This looks like a fix in that mlock_pte_range() *does* call mlock_folio() 
when pmd_trans_huge_lock() returns a non-NULL @ptl.

So it is not in preparation for a future change it is making the pte and
pmd cases behave the same to drop mlock requests.

The code change looks good, but do add a Fixes tag and reword the
changelog a bit before adding:

Reviewed-by: Dan Williams <dan.j.williams at intel.com>