nvme-loop: handle cpu unplug when re-establishing the controller

If a cpu unplug event has occured, we need to take the minimum
of the provided nr_io_queues and the number of online cpus,
otherwise we won't be able to connect them as blk-mq mapping
won't dispatch to those queues.

Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Sagi Grimberg <[e-mail]>

drivers/nvme/target/loop.c

···
 static int nvme_loop_init_iod(struct nvme_loop_ctrl *ctrl,
 		struct nvme_loop_iod *iod, unsigned int queue_idx)
 {
-	BUG_ON(queue_idx >= ctrl->queue_count);
-
 	iod->req.cmd = &iod->cmd;
 	iod->req.rsp = &iod->rsp;
 	iod->queue = &ctrl->queues[queue_idx];
···
 	kfree(ctrl);
 }
 
+static void nvme_loop_destroy_io_queues(struct nvme_loop_ctrl *ctrl)
+{
+	int i;
+
+	for (i = 1; i < ctrl->queue_count; i++)
+		nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
+}
+
+static int nvme_loop_init_io_queues(struct nvme_loop_ctrl *ctrl)
+{
+	struct nvmf_ctrl_options *opts = ctrl->ctrl.opts;
+	unsigned int nr_io_queues;
+	int ret, i;
+
+	nr_io_queues = min(opts->nr_io_queues, num_online_cpus());
+	ret = nvme_set_queue_count(&ctrl->ctrl, &nr_io_queues);
+	if (ret || !nr_io_queues)
+		return ret;
+
+	dev_info(ctrl->ctrl.device, "creating %d I/O queues.\n", nr_io_queues);
+
+	for (i = 1; i <= nr_io_queues; i++) {
+		ctrl->queues[i].ctrl = ctrl;
+		ret = nvmet_sq_init(&ctrl->queues[i].nvme_sq);
+		if (ret)
+			goto out_destroy_queues;
+
+		ctrl->queue_count++;
+	}
+
+	return 0;
+
+out_destroy_queues:
+	nvme_loop_destroy_io_queues(ctrl);
+	return ret;
+}
+
 static int nvme_loop_configure_admin_queue(struct nvme_loop_ctrl *ctrl)
 {
 	int error;
···
 
 static void nvme_loop_shutdown_ctrl(struct nvme_loop_ctrl *ctrl)
 {
-	int i;
-
 	nvme_stop_keep_alive(&ctrl->ctrl);
 
 	if (ctrl->queue_count > 1) {
 		nvme_stop_queues(&ctrl->ctrl);
 		blk_mq_tagset_busy_iter(&ctrl->tag_set,
 					nvme_cancel_request, &ctrl->ctrl);
-
-		for (i = 1; i < ctrl->queue_count; i++)
-			nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
+		nvme_loop_destroy_io_queues(ctrl);
 	}
 
 	if (ctrl->ctrl.state == NVME_CTRL_LIVE)
···
 	if (ret)
 		goto out_disable;
 
-	for (i = 1; i <= ctrl->ctrl.opts->nr_io_queues; i++) {
-		ctrl->queues[i].ctrl = ctrl;
-		ret = nvmet_sq_init(&ctrl->queues[i].nvme_sq);
-		if (ret)
-			goto out_free_queues;
+	ret = nvme_loop_init_io_queues(ctrl);
+	if (ret)
+		goto out_destroy_admin;
 
-		ctrl->queue_count++;
-	}
-
-	for (i = 1; i <= ctrl->ctrl.opts->nr_io_queues; i++) {
+	for (i = 1; i < ctrl->queue_count; i++) {
 		ret = nvmf_connect_io_queue(&ctrl->ctrl, i);
 		if (ret)
-			goto out_free_queues;
+			goto out_destroy_io;
 	}
 
 	changed = nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_LIVE);
···
 
 	return;
 
-out_free_queues:
-	for (i = 1; i < ctrl->queue_count; i++)
-		nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
+out_destroy_io:
+	nvme_loop_destroy_io_queues(ctrl);
+out_destroy_admin:
 	nvme_loop_destroy_admin_queue(ctrl);
 out_disable:
 	dev_warn(ctrl->ctrl.device, "Removing after reset failure\n");
···
 
 static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)
 {
-	struct nvmf_ctrl_options *opts = ctrl->ctrl.opts;
 	int ret, i;
 
-	ret = nvme_set_queue_count(&ctrl->ctrl, &opts->nr_io_queues);
-	if (ret || !opts->nr_io_queues)
+	ret = nvme_loop_init_io_queues(ctrl);
+	if (ret)
 		return ret;
-
-	dev_info(ctrl->ctrl.device, "creating %d I/O queues.\n",
-		opts->nr_io_queues);
-
-	for (i = 1; i <= opts->nr_io_queues; i++) {
-		ctrl->queues[i].ctrl = ctrl;
-		ret = nvmet_sq_init(&ctrl->queues[i].nvme_sq);
-		if (ret)
-			goto out_destroy_queues;
-
-		ctrl->queue_count++;
-	}
 
 	memset(&ctrl->tag_set, 0, sizeof(ctrl->tag_set));
 	ctrl->tag_set.ops = &nvme_loop_mq_ops;
···
 		goto out_free_tagset;
 	}
 
-	for (i = 1; i <= opts->nr_io_queues; i++) {
+	for (i = 1; i < ctrl->queue_count; i++) {
 		ret = nvmf_connect_io_queue(&ctrl->ctrl, i);
 		if (ret)
 			goto out_cleanup_connect_q;
···
 out_free_tagset:
 	blk_mq_free_tag_set(&ctrl->tag_set);
 out_destroy_queues:
-	for (i = 1; i < ctrl->queue_count; i++)
-		nvmet_sq_destroy(&ctrl->queues[i].nvme_sq);
+	nvme_loop_destroy_io_queues(ctrl);
 	return ret;
 }