nvme-fc: shorten reconnect delay if possible for FC

We've had several complaints about a 10s reconnect delay (the default)
when there was an error while there is connectivity to a subsystem.
The max_reconnects and reconnect_delay are set in common code prior to
calling the transport to create the controller.

This change checks if the default reconnect delay is being used, and if
so, it adjusts it to a shorter period (2s) for the nvme-fc transport.
It does so by calculating the controller loss tmo window, changing the
value of the reconnect delay, and then recalculating the maximum number
of reconnect attempts allowed.

Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Author: James Smart

drivers/nvme/host/fc.c

@@ -26,6 +26,10 @@ enum nvme_fc_queue_flags {
 };
 
 #define NVME_FC_DEFAULT_DEV_LOSS_TMO	60	/* seconds */
+#define NVME_FC_DEFAULT_RECONNECT_TMO	2	/* delay between reconnects
+						 * when connected and a
+						 * connection failure.
+						 */
 
 struct nvme_fc_queue {
 	struct nvme_fc_ctrl	*ctrl;
@@ -3436,7 +3440,7 @@ nvme_fc_init_ctrl(struct device *dev, struct nvmf_ctrl_options *opts,
 {
 	struct nvme_fc_ctrl *ctrl;
 	unsigned long flags;
-	int ret, idx;
+	int ret, idx, ctrl_loss_tmo;
 
 	if (!(rport->remoteport.port_role &
 	    (FC_PORT_ROLE_NVME_DISCOVERY | FC_PORT_ROLE_NVME_TARGET))) {
@@ -3462,6 +3466,19 @@ nvme_fc_init_ctrl(struct device *dev, struct nvmf_ctrl_options *opts,
 		goto out_free_ctrl;
 	}
 
+	/*
+	 * if ctrl_loss_tmo is being enforced and the default reconnect delay
+	 * is being used, change to a shorter reconnect delay for FC.
+	 */
+	if (opts->max_reconnects != -1 &&
+	    opts->reconnect_delay == NVMF_DEF_RECONNECT_DELAY &&
+	    opts->reconnect_delay > NVME_FC_DEFAULT_RECONNECT_TMO) {
+		ctrl_loss_tmo = opts->max_reconnects * opts->reconnect_delay;
+		opts->reconnect_delay = NVME_FC_DEFAULT_RECONNECT_TMO;
+		opts->max_reconnects = DIV_ROUND_UP(ctrl_loss_tmo,
+						opts->reconnect_delay);
+	}
+
 	ctrl->ctrl.opts = opts;
 	ctrl->ctrl.nr_reconnects = 0;
 	if (lport->dev)