The original form of these was added (to the HP zx1 platform only) by
the following bitkeeper commit (by the way of the historic.git tree):

commit 66b99421
Author: Andrew Morton <akpm@osdl.org>
Date:   Sat Mar 13 17:05:37 2004 -0800

    [PATCH] DMA: Fill gaping hole in DMA API interfaces.

    From: "David S. Miller" <davem@redhat.com>

The commit does not explain why we'd need the memory barrier on ia64,
it never included the swiotlb or SGI IOMMU based platforms, and also
failed to address the map/unmap parts of the dma mapping interface,
which should provide the same ordering semantics and actually are
commonly used.  The conclusion of this is that they were added in
error and should be removed.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>