+/*
+ * 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...
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