[RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL

[Dan Williams]

On Mon, Nov 9, 2020 at 8:47 AM Logan Gunthorpe <logang at deltatee.com> wrote:
>
>
>
> On 2020-11-09 2:12 a.m., Christoph Hellwig wrote:
> > On Fri, Nov 06, 2020 at 10:00:25AM -0700, Logan Gunthorpe wrote:
> >> We make use of the top bit of the dma_length to indicate a P2PDMA
> >> segment.
> >
> > I don't think "we" can.  There is nothing limiting the size of a SGL
> > segment.
>
> Yes, I expected this would be the unacceptable part. Any alternative ideas?

Why is the SG_P2PDMA_FLAG needed as compared to checking the SGL
segment-pages for is_pci_p2pdma_page()?