Add a helper dax_ioamp_zero() to zero a range. This patch basically
merges __dax_zero_page_range() and iomap_dax_zero().
Suggested-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20200228163456.1587-7-vgoyal@redhat.comSigned-off-by: NDan Williams <dan.j.williams@intel.com>