On Wed, Jun 23, 2021 at 10:00:29PM +0300, Oded Gabbay wrote:

I understand the argument and I agree that for the generic case, the
top of the stack can't assume anything.
Having said that, in this case the SGL is encapsulated inside a dma-buf object.

But the scatterlist is defined to have a valid page.  If in dma-bufs you
can't do that dmabufs are completely broken.  Apparently the gpu folks
can somehow live with that and deal with the pitfals, but for dma-buf
users outside of their little fiefdom were they arbitrarily break rules
it simply is not acceptable.