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>

diff --git a/Documentation/ABI/stable/sysfs-transport-srp b/Documentation/ABI/stable/sysfs-transport-srp
index 8b6acc7..ec7af69 100644 (file)
--- a/Documentation/ABI/stable/sysfs-transport-srp
+++ b/Documentation/ABI/stable/sysfs-transport-srp
@@ -30,6 +30,14 @@ Contact:     linux-scsi@vger.kernel.org
 Description:   16-byte local SRP port identifier in hexadecimal format. An
                example: 4c:49:4e:55:58:20:56:49:4f:00:00:00:00:00:00:00.
 
+What:          /sys/class/srp_remote_ports/port-<h>:<n>/reconnect_delay
+Date:          February 1, 2014
+KernelVersion: 3.13
+Contact:       linux-scsi@vger.kernel.org, linux-rdma@vger.kernel.org
+Description:   Number of seconds the SCSI layer will wait after a reconnect
+               attempt failed before retrying. Setting this attribute to
+               "off" will disable time-based reconnecting.
+
 What:          /sys/class/srp_remote_ports/port-<h>:<n>/roles
 Date:          June 27, 2007
 KernelVersion: 2.6.24

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 076a3ab..99c893d 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -145,9 +145,9 @@ static int srp_tmo_set(const char *val, const struct kernel_param *kp)
                tmo = -1;
        }
        if (kp->arg == &srp_fast_io_fail_tmo)
-               res = srp_tmo_valid(tmo, srp_dev_loss_tmo);
+               res = srp_tmo_valid(-1, tmo, srp_dev_loss_tmo);
        else
-               res = srp_tmo_valid(srp_fast_io_fail_tmo, tmo);
+               res = srp_tmo_valid(-1, srp_fast_io_fail_tmo, tmo);
        if (res)
                goto out;
        *(int *)kp->arg = tmo;

diff --git a/drivers/scsi/scsi_transport_srp.c b/drivers/scsi/scsi_transport_srp.c
index 2696e26..2700a5a 100644 (file)
--- 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;

diff --git a/include/scsi/scsi_transport_srp.h b/include/scsi/scsi_transport_srp.h
index ee70016..4ebf691 100644 (file)
--- a/include/scsi/scsi_transport_srp.h
+++ b/include/scsi/scsi_transport_srp.h
@@ -31,7 +31,8 @@ enum srp_rport_state {
 /**
  * struct srp_rport
  * @lld_data: LLD private data.
- * @mutex:    Protects against concurrent rport fast_io_fail / dev_loss_tmo.
+ * @mutex:    Protects against concurrent rport reconnect / fast_io_fail /
+ *   dev_loss_tmo activity.
  */
 struct srp_rport {
        /* for initiator and target drivers */
@@ -48,6 +49,9 @@ struct srp_rport {
        struct mutex            mutex;
        enum srp_rport_state    state;
        bool                    deleted;
+       int                     reconnect_delay;
+       int                     failed_reconnects;
+       struct delayed_work     reconnect_work;
        int                     fast_io_fail_tmo;
        int                     dev_loss_tmo;
        struct delayed_work     fast_io_fail_work;
@@ -60,6 +64,7 @@ struct srp_rport {
  *     dev_loss_tmo sysfs attribute for an rport.
  * @reset_timer_if_blocked: Whether or srp_timed_out() should reset the command
  *     timer if the device on which it has been queued is blocked.
+ * @reconnect_delay: If not NULL, points to the default reconnect_delay value.
  * @fast_io_fail_tmo: If not NULL, points to the default fast_io_fail_tmo value.
  * @dev_loss_tmo: If not NULL, points to the default dev_loss_tmo value.
  * @reconnect: Callback function for reconnecting to the target. See also
@@ -71,6 +76,7 @@ struct srp_function_template {
        /* for initiator drivers */
        bool has_rport_state;
        bool reset_timer_if_blocked;
+       int *reconnect_delay;
        int *fast_io_fail_tmo;
        int *dev_loss_tmo;
        int (*reconnect)(struct srp_rport *rport);
@@ -90,7 +96,8 @@ extern void srp_rport_put(struct srp_rport *rport);
 extern struct srp_rport *srp_rport_add(struct Scsi_Host *,
                                       struct srp_rport_identifiers *);
 extern void srp_rport_del(struct srp_rport *);
-extern int srp_tmo_valid(int fast_io_fail_tmo, int dev_loss_tmo);
+extern int srp_tmo_valid(int reconnect_delay, int fast_io_fail_tmo,
+                        int dev_loss_tmo);
 extern int srp_reconnect_rport(struct srp_rport *rport);
 extern void srp_start_tl_fail_timers(struct srp_rport *rport);
 extern void srp_remove_host(struct Scsi_Host *);