UBIFS with dma on 4.6 kernel is not working

[Christoph Hellwig]

On Fri, Oct 21, 2016 at 03:07:57PM +0200, Richard Weinberger wrote:
> Hmm, thought this is still problematic on VIVT architectures.
> Boris tried to provide a solution for that some time ago:
> http://www.spinics.net/lists/arm-kernel/msg494025.html

Things have been working fine for approx 10 years when using
flush_kernel_vmap_range before doing I/O using the physical addresses and
then invalidate_kernel_vmap_range when completing the I/O and going back
to using the virtual mapping for XFS.

Of course all this assumes at least the higher level that did the
vm_map_ram operation knows about this dance between virtually mapped and
physiscal addresses.