nvme: enable to inject errors into admin commands

This enables to inject errors into the commands submitted to the admin
queue.

It is useful to test error handling in the controller initialization.

	# echo 100 > /sys/kernel/debug/nvme0/fault_inject/probability
	# echo 1 > /sys/kernel/debug/nvme0/fault_inject/times
	# echo 10 > /sys/kernel/debug/nvme0/fault_inject/space
	# nvme reset /dev/nvme0
	# dmesg
	...
	nvme nvme0: Could not set queue count (16385)
	nvme nvme0: IO queues not created
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -3722,6 +3722,7 @@ EXPORT_SYMBOL_GPL(nvme_start_ctrl);
 
 void nvme_uninit_ctrl(struct nvme_ctrl *ctrl)
 {
+	nvme_fault_inject_fini(&ctrl->fault_inject);
 	dev_pm_qos_hide_latency_tolerance(ctrl->device);
 	cdev_device_del(&ctrl->cdev, ctrl->device);
 }
@@ -3817,6 +3818,8 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 	dev_pm_qos_update_user_latency_tolerance(ctrl->device,
 		min(default_ps_max_latency_us, (unsigned long)S32_MAX));
 
+	nvme_fault_inject_init(&ctrl->fault_inject, dev_name(ctrl->device));
+
 	return 0;
 out_free_name:
 	kfree_const(ctrl->device->kobj.name);

drivers/nvme/host/fault_inject.c

@@ -60,9 +60,6 @@ void nvme_should_fail(struct request *req)
 	struct nvme_fault_inject *fault_inject = NULL;
 	u16 status;
 
-	/*
-	 * make sure this request is coming from a valid namespace
-	 */
 	if (disk) {
 		struct nvme_ns *ns = disk->private_data;
 
@@ -70,6 +67,8 @@ void nvme_should_fail(struct request *req)
 			fault_inject = &ns->fault_inject;
 		else
 			WARN_ONCE(1, "No namespace found for request\n");
+	} else {
+		fault_inject = &nvme_req(req)->ctrl->fault_inject;
 	}
 
 	if (fault_inject && should_fail(&fault_inject->attr, 1)) {

drivers/nvme/host/nvme.h

@@ -256,6 +256,8 @@ struct nvme_ctrl {
 
 	struct page *discard_page;
 	unsigned long discard_page_busy;
+
+	struct nvme_fault_inject fault_inject;
 };
 
 enum nvme_iopolicy {