scsi_transport_srp: Add periodic reconnect support

Add support for periodically reconnecting to an SRP target until
the dev_loss timer expires. After the tenth reconnection attempt,
gradually slow down subsequent reconnect attempts.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 99 insertions, 7 deletions

diff --git a/drivers/scsi/scsi_transport_srp.c b/drivers/scsi/scsi_transport_srp.c
index 2696e26b3423..2700a5a09bd4 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -41,7 +41,7 @@ struct srp_host_attrs {
 #define to_srp_host_attrs(host)	((struct srp_host_attrs *)(host)->shost_data)
 
 #define SRP_HOST_ATTRS 0
-#define SRP_RPORT_ATTRS 6
+#define SRP_RPORT_ATTRS 8
 
 struct srp_internal {
 	struct scsi_transport_template t;
@@ -69,11 +69,13 @@ static inline struct Scsi_Host *rport_to_shost(struct srp_rport *r)
  * are finished in a reasonable time. Hence do not allow the fast I/O fail
  * timeout to exceed SCSI_DEVICE_BLOCK_MAX_TIMEOUT. Furthermore, these
  * parameters must be such that multipath can detect failed paths timely.
- * Hence do not allow both parameters to be disabled simultaneously.
+ * Hence do not allow all three parameters to be disabled simultaneously.
  */
-int srp_tmo_valid(int fast_io_fail_tmo, int dev_loss_tmo)
+int srp_tmo_valid(int reconnect_delay, int fast_io_fail_tmo, int dev_loss_tmo)
 {
-	if (fast_io_fail_tmo < 0 && dev_loss_tmo < 0)
+	if (reconnect_delay < 0 && fast_io_fail_tmo < 0 && dev_loss_tmo < 0)
+		return -EINVAL;
+	if (reconnect_delay == 0)
 		return -EINVAL;
 	if (fast_io_fail_tmo > SCSI_DEVICE_BLOCK_MAX_TIMEOUT)
 		return -EINVAL;
@@ -202,6 +204,56 @@ static int srp_parse_tmo(int *tmo, const char *buf)
 	return res;
 }
 
+static ssize_t show_reconnect_delay(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct srp_rport *rport = transport_class_to_srp_rport(dev);
+
+	return srp_show_tmo(buf, rport->reconnect_delay);
+}
+
+static ssize_t store_reconnect_delay(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, const size_t count)
+{
+	struct srp_rport *rport = transport_class_to_srp_rport(dev);
+	int res, delay;
+
+	res = srp_parse_tmo(&delay, buf);
+	if (res)
+		goto out;
+	res = srp_tmo_valid(delay, rport->fast_io_fail_tmo,
+			    rport->dev_loss_tmo);
+	if (res)
+		goto out;
+
+	if (rport->reconnect_delay <= 0 && delay > 0 &&
+	    rport->state != SRP_RPORT_RUNNING) {
+		queue_delayed_work(system_long_wq, &rport->reconnect_work,
+				   delay * HZ);
+	} else if (delay <= 0) {
+		cancel_delayed_work(&rport->reconnect_work);
+	}
+	rport->reconnect_delay = delay;
+	res = count;
+
+out:
+	return res;
+}
+
+static DEVICE_ATTR(reconnect_delay, S_IRUGO | S_IWUSR, show_reconnect_delay,
+		   store_reconnect_delay);
+
+static ssize_t show_failed_reconnects(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct srp_rport *rport = transport_class_to_srp_rport(dev);
+
+	return sprintf(buf, "%d\n", rport->failed_reconnects);
+}
+
+static DEVICE_ATTR(failed_reconnects, S_IRUGO, show_failed_reconnects, NULL);
+
 static ssize_t show_srp_rport_fast_io_fail_tmo(struct device *dev,
 					       struct device_attribute *attr,
 					       char *buf)
@@ -222,7 +274,8 @@ static ssize_t store_srp_rport_fast_io_fail_tmo(struct device *dev,
 	res = srp_parse_tmo(&fast_io_fail_tmo, buf);
 	if (res)
 		goto out;
-	res = srp_tmo_valid(fast_io_fail_tmo, rport->dev_loss_tmo);
+	res = srp_tmo_valid(rport->reconnect_delay, fast_io_fail_tmo,
+			    rport->dev_loss_tmo);
 	if (res)
 		goto out;
 	rport->fast_io_fail_tmo = fast_io_fail_tmo;
@@ -256,7 +309,8 @@ static ssize_t store_srp_rport_dev_loss_tmo(struct device *dev,
 	res = srp_parse_tmo(&dev_loss_tmo, buf);
 	if (res)
 		goto out;
-	res = srp_tmo_valid(rport->fast_io_fail_tmo, dev_loss_tmo);
+	res = srp_tmo_valid(rport->reconnect_delay, rport->fast_io_fail_tmo,
+			    dev_loss_tmo);
 	if (res)
 		goto out;
 	rport->dev_loss_tmo = dev_loss_tmo;
@@ -312,6 +366,29 @@ invalid:
 	return -EINVAL;
 }
 
+/**
+ * srp_reconnect_work() - reconnect and schedule a new attempt if necessary
+ */
+static void srp_reconnect_work(struct work_struct *work)
+{
+	struct srp_rport *rport = container_of(to_delayed_work(work),
+					struct srp_rport, reconnect_work);
+	struct Scsi_Host *shost = rport_to_shost(rport);
+	int delay, res;
+
+	res = srp_reconnect_rport(rport);
+	if (res != 0) {
+		shost_printk(KERN_ERR, shost,
+			     "reconnect attempt %d failed (%d)\n",
+			     ++rport->failed_reconnects, res);
+		delay = rport->reconnect_delay *
+			min(100, max(1, rport->failed_reconnects - 10));
+		if (delay > 0)
+			queue_delayed_work(system_long_wq,
+					   &rport->reconnect_work, delay * HZ);
+	}
+}
+
 static void __rport_fail_io_fast(struct srp_rport *rport)
 {
 	struct Scsi_Host *shost = rport_to_shost(rport);
@@ -371,16 +448,21 @@ static void rport_dev_loss_timedout(struct work_struct *work)
 static void __srp_start_tl_fail_timers(struct srp_rport *rport)
 {
 	struct Scsi_Host *shost = rport_to_shost(rport);
-	int fast_io_fail_tmo, dev_loss_tmo;
+	int delay, fast_io_fail_tmo, dev_loss_tmo;
 
 	lockdep_assert_held(&rport->mutex);
 
 	if (!rport->deleted) {
+		delay = rport->reconnect_delay;
 		fast_io_fail_tmo = rport->fast_io_fail_tmo;
 		dev_loss_tmo = rport->dev_loss_tmo;
 		pr_debug("%s current state: %d\n",
 			 dev_name(&shost->shost_gendev), rport->state);
 
+		if (delay > 0)
+			queue_delayed_work(system_long_wq,
+					   &rport->reconnect_work,
+					   1UL * delay * HZ);
 		if (fast_io_fail_tmo >= 0 &&
 		    srp_rport_set_state(rport, SRP_RPORT_BLOCKED) == 0) {
 			pr_debug("%s new state: %d\n",
@@ -481,6 +563,7 @@ int srp_reconnect_rport(struct srp_rport *rport)
 		cancel_delayed_work(&rport->fast_io_fail_work);
 		cancel_delayed_work(&rport->dev_loss_work);
 
+		rport->failed_reconnects = 0;
 		srp_rport_set_state(rport, SRP_RPORT_RUNNING);
 		scsi_target_unblock(&shost->shost_gendev, SDEV_RUNNING);
 		/*
@@ -539,6 +622,7 @@ static void srp_rport_release(struct device *dev)
 {
 	struct srp_rport *rport = dev_to_rport(dev);
 
+	cancel_delayed_work_sync(&rport->reconnect_work);
 	cancel_delayed_work_sync(&rport->fast_io_fail_work);
 	cancel_delayed_work_sync(&rport->dev_loss_work);
 
@@ -635,6 +719,10 @@ struct srp_rport *srp_rport_add(struct Scsi_Host *shost,
 	memcpy(rport->port_id, ids->port_id, sizeof(rport->port_id));
 	rport->roles = ids->roles;
 
+	if (i->f->reconnect)
+		rport->reconnect_delay = i->f->reconnect_delay ?
+			*i->f->reconnect_delay : 10;
+	INIT_DELAYED_WORK(&rport->reconnect_work, srp_reconnect_work);
 	rport->fast_io_fail_tmo = i->f->fast_io_fail_tmo ?
 		*i->f->fast_io_fail_tmo : 15;
 	rport->dev_loss_tmo = i->f->dev_loss_tmo ? *i->f->dev_loss_tmo : 60;
@@ -773,6 +861,10 @@ srp_attach_transport(struct srp_function_template *ft)
 		i->rport_attrs[count++] = &dev_attr_fast_io_fail_tmo;
 		i->rport_attrs[count++] = &dev_attr_dev_loss_tmo;
 	}
+	if (ft->reconnect) {
+		i->rport_attrs[count++] = &dev_attr_reconnect_delay;
+		i->rport_attrs[count++] = &dev_attr_failed_reconnects;
+	}
 	if (ft->rport_delete)
 		i->rport_attrs[count++] = &dev_attr_delete;
 	i->rport_attrs[count++] = NULL;