mm: add kmap_to_page()
commit
fcb8996728fb59eddf84678df7cb213b2c9a2e26 upstream.
This is extracted from Mel Gorman's commit
5a178119b0fb ('mm: add
support for direct_IO to highmem pages') upstream.
Required to backport commit
b9cdc88df8e6 ('virtio: 9p: correctly pass
physical address to userspace for high pages').
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>