nvme: Make controller state visible via sysfs

Easier for debugging and testing state machine
transitions.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/host/core.c

@@ -1577,6 +1577,29 @@ static ssize_t nvme_sysfs_show_transport(struct device *dev,
 }
 static DEVICE_ATTR(transport, S_IRUGO, nvme_sysfs_show_transport, NULL);
 
+static ssize_t nvme_sysfs_show_state(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+	static const char *const state_name[] = {
+		[NVME_CTRL_NEW]		= "new",
+		[NVME_CTRL_LIVE]	= "live",
+		[NVME_CTRL_RESETTING]	= "resetting",
+		[NVME_CTRL_RECONNECTING]= "reconnecting",
+		[NVME_CTRL_DELETING]	= "deleting",
+		[NVME_CTRL_DEAD]	= "dead",
+	};
+
+	if ((unsigned)ctrl->state < ARRAY_SIZE(state_name) &&
+	    state_name[ctrl->state])
+		return sprintf(buf, "%s\n", state_name[ctrl->state]);
+
+	return sprintf(buf, "unknown state\n");
+}
+
+static DEVICE_ATTR(state, S_IRUGO, nvme_sysfs_show_state, NULL);
+
 static ssize_t nvme_sysfs_show_subsysnqn(struct device *dev,
 					 struct device_attribute *attr,
 					 char *buf)
@@ -1609,6 +1632,7 @@ static struct attribute *nvme_dev_attrs[] = {
 	&dev_attr_transport.attr,
 	&dev_attr_subsysnqn.attr,
 	&dev_attr_address.attr,
+	&dev_attr_state.attr,
 	NULL
 };