On Tue, Apr 22, 2025 at 1:16 AM Pavel Begunkov asml.silence@gmail.com wrote:
On 4/18/25 00:15, Mina Almasry wrote:
Later patches in the series adds TX net_iovs where there is no pp associated, so we can't rely on niov->pp->mp_ops to tell what is the type of the net_iov.
That's fine, but that needs a NULL pp check in io_uring as well, specifically in io_zcrx_recv_frag().
I think you mean this update in the code:
if (!niov->pp || niov->pp->mp_ops != &io_uring_pp_zc_ops || io_pp_to_ifq(niov->pp) != ifq) return -EFAULT;
Yes, thanks, will do.
You can also move it to struct net_iov_area and check niov->owner->type instead. It's a safer choice than aliasing with struct page, there is no cost as you're loading ->owner anyway (e.g. for net_iov_virtual_addr()), and it's better in terms of normalisation / not unnecessary duplicating it, assuming we'll never have niovs of different types bound to the same struct net_iov_area.
Putting it in niov->owner->type is an alternative approach. I don't see a strong reason to go with one over the other. I'm thinking there will be fast code paths that want to know the type of the frag or skb and don't need the owner, so it will be good to save loading another cacheline. We have more space in struct net_iov than we know what to do with anyway.
-- Thanks, Mina