On Fri, 17 Sep 2021 12:02:46 +0200 Lorenzo Bianconi wrote:
> > > +static inline unsigned int xdp_get_frag_tailroom(const skb_frag_t *frag)
> > > +{
> > > + struct page *page = skb_frag_page(frag);
> > > +
> > > + return page_size(page) - skb_frag_size(frag) - skb_frag_off(frag);
> > > +}
> >
> > How do we deal with NICs which can pack multiple skbs into a page frag?
> > skb_shared_info field to mark the end of last fragment? Just want to make
> > sure there is a path to supporting such designs.
>
> I guess here, intead of using page_size(page) we can rely on xdp_buff->frame_sz
> or even on skb_shared_info()->xdp_frag_truesize (assuming all fragments from a
> given hw have the same truesize, but I think this is something we can rely on)
>
> static inline unsigned int xdp_get_frag_tailroom(struct xdp_buff *xdp,
> const skb_frag_t *frag)
> {
> return xdp->frame_sz - skb_frag_size(frag) - skb_frag_off(frag);
> }
>
> what do you think?
Could work! We'd need to document the semantics of frame_sz for mb
frames clearly but I don't see why not.
