Re: [PATCH v5 13/13] nvmet: Optionally use PCI P2P memory

Sagi Grimberg
2018-08-31T00:25:12Z

> +/*
> + * If allow_p2pmem is set, we will try to use P2P memory for the SGL lists for
> + * Ι/O commands. This requires the PCI p2p device to be compatible with the
> + * backing device for every namespace on this controller.
> + */
> +static void nvmet_setup_p2pmem(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
> +{
> + struct nvmet_ns *ns;
> + int ret;
> +
> + if (!req->port->use_p2pmem || !req->p2p_client)
> + return;
> +
> + mutex_lock(&ctrl->subsys->lock);
> +
> + ret = pci_p2pdma_add_client(&ctrl->p2p_clients, req->p2p_client);
> + if (ret) {
> + pr_err("failed adding peer-to-peer DMA client %s: %d\n",
> + dev_name(req->p2p_client), ret);
> + goto free_devices;
> + }
> +
> + list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link) {
> + ret = nvmet_p2pdma_add_client(ctrl, ns);
> + if (ret)
> + goto free_devices;
> + }
> +
> + if (req->port->p2p_dev) {
> + if (!pci_p2pdma_assign_provider(req->port->p2p_dev,
> + &ctrl->p2p_clients)) {
> + pr_info("peer-to-peer memory on %s is not supported\n",
> + pci_name(req->port->p2p_dev));
> + goto free_devices;
> + }
> + ctrl->p2p_dev = pci_dev_get(req->port->p2p_dev);
> + } else {

When is port->p2p_dev == NULL? a little more documentation would help
here...