From: Doug Doan <dougd@cray.com>

When a copy-on-write occurs, we take one of two paths in handle_mm_fault: 
through handle_pte_fault for normal pages, or through hugetlb_fault for huge pages.

In the normal page case, we eventually get to do_wp_page and call mmu notifiers 
via ptep_clear_flush_notify. There is no callout to the mmmu notifiers in the 
huge page case. This patch fixes that.

Signed-off-by: Doug Doan <dougd@cray.com>
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