ceph: switch to page_mkwrite_check_truncate in ceph_page_mkwrite
Use the "page has been truncated" logic in page_mkwrite_check_truncate
instead of reimplementing it here. Other than with the existing code,
fail with -EFAULT / VM_FAULT_NOPAGE when page_offset(page) == size here
as well, as should be expected.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>