On Fri, Jan 15, 2021 at 11:04:48AM -0800, Axel Rasmussen wrote:

As the comment says: for the MINOR fault use case, although the page
might be present and populated in the other (non-UFFD-registered) half
of the shared mapping, it may be out of date, and we explicitly want
userspace to get a minor fault so it can check and potentially update
the page's contents.

Huge PMD sharing would prevent these faults from occurring for
suitably aligned areas, so disable it upon UFFD registration.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu