Call flush_dcache_page after PIO data transfers in libata-sff.c

Call flush_dcache_page after PIO data transfers in libata-sff.c

commit 2d68b7fe55d9e19a8a868224ed0dfd6526568521 upstream.

flush_dcache_page() must be called after (!ATA_TFLAG_WRITE) the
data copying to avoid D-cache aliasing with user space or I-D cache
coherency issues (when reading data from an ATA device using PIO,
the kernel dirties the D-cache but there is no flush_dcache_page()
required on Harvard architectures).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>