[SCSI] libsas: prevent domain rediscovery competing with ata error handling

libata error handling provides for a timeout for link recovery.  libsas
must not rescan for previously known devices in this interval otherwise
it may remove a device that is simply waiting for its link to recover.
Let libata-eh make the determination of when the link is stable and
prevent libsas (host workqueue) from taking action while this
determination is pending.

Using a mutex (ha->disco_mutex) to flush and disable revalidation while
eh is running requires any discovery action that may block on eh be
moved to its own context outside the lock.  Probing ATA devices
explicitly waits on ata-eh and the cache-flush-io issued during device
removal may also pend awaiting eh completion.  Essentially any rphy
add/remove activity needs to run outside the lock.

This adds two new cleanup states for sas_unregister_domain_devices()
'allocated-but-not-probed', and 'flagged-for-destruction'.  In the
'allocated-but-not-probed' state  dev->rphy points to a rphy that is
known to have not been through a sas_rphy_add() event.  At domain
teardown check if this device is still pending probe and cleanup
accordingly.  Similarly if a device has already been queued for removal
then sas_unregister_domain_devices has nothing to do.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 57 insertions, 6 deletions

diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index 32e0117..7e8fdcb 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -148,9 +148,14 @@ static int sas_get_port_device(struct asd_sas_port *port)
 	port->disc.max_level = 0;
 
 	dev->rphy = rphy;
-	spin_lock_irq(&port->dev_list_lock);
-	list_add_tail(&dev->dev_list_node, &port->dev_list);
-	spin_unlock_irq(&port->dev_list_lock);
+
+	if (dev_is_sata(dev))
+		list_add_tail(&dev->disco_list_node, &port->disco_list);
+	else {
+		spin_lock_irq(&port->dev_list_lock);
+		list_add_tail(&dev->dev_list_node, &port->dev_list);
+		spin_unlock_irq(&port->dev_list_lock);
+	}
 
 	return 0;
 }
@@ -255,14 +260,43 @@ static void sas_unregister_common_dev(struct asd_sas_port *port, struct domain_d
 	sas_put_device(dev);
 }
 
-void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
+static void sas_destruct_devices(struct work_struct *work)
 {
-	if (dev->rphy) {
+	struct domain_device *dev, *n;
+	struct sas_discovery_event *ev =
+		container_of(work, struct sas_discovery_event, work);
+	struct asd_sas_port *port = ev->port;
+
+	clear_bit(DISCE_DESTRUCT, &port->disc.pending);
+
+	list_for_each_entry_safe(dev, n, &port->destroy_list, disco_list_node) {
+		list_del_init(&dev->disco_list_node);
+
 		sas_remove_children(&dev->rphy->dev);
 		sas_rphy_delete(dev->rphy);
 		dev->rphy = NULL;
+		sas_unregister_common_dev(port, dev);
+
+		sas_put_device(dev);
+	}
+}
+
+void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
+{
+	if (!test_bit(SAS_DEV_DESTROY, &dev->state) &&
+	    !list_empty(&dev->disco_list_node)) {
+		/* this rphy never saw sas_rphy_add */
+		list_del_init(&dev->disco_list_node);
+		sas_rphy_free(dev->rphy);
+		dev->rphy = NULL;
+		sas_unregister_common_dev(port, dev);
+	}
+
+	if (dev->rphy && !test_and_set_bit(SAS_DEV_DESTROY, &dev->state)) {
+		sas_rphy_unlink(dev->rphy);
+		list_move_tail(&dev->disco_list_node, &port->destroy_list);
+		sas_discover_event(dev->port, DISCE_DESTRUCT);
 	}
-	sas_unregister_common_dev(port, dev);
 }
 
 void sas_unregister_domain_devices(struct asd_sas_port *port)
@@ -271,6 +305,8 @@ void sas_unregister_domain_devices(struct asd_sas_port *port)
 
 	list_for_each_entry_safe_reverse(dev, n, &port->dev_list, dev_list_node)
 		sas_unregister_dev(port, dev);
+	list_for_each_entry_safe(dev, n, &port->disco_list, disco_list_node)
+		sas_unregister_dev(port, dev);
 
 	port->port->rphy = NULL;
 
@@ -335,6 +371,7 @@ static void sas_discover_domain(struct work_struct *work)
 		sas_rphy_free(dev->rphy);
 		dev->rphy = NULL;
 
+		list_del_init(&dev->disco_list_node);
 		spin_lock_irq(&port->dev_list_lock);
 		list_del_init(&dev->dev_list_node);
 		spin_unlock_irq(&port->dev_list_lock);
@@ -353,16 +390,28 @@ static void sas_revalidate_domain(struct work_struct *work)
 	struct sas_discovery_event *ev =
 		container_of(work, struct sas_discovery_event, work);
 	struct asd_sas_port *port = ev->port;
+	struct sas_ha_struct *ha = port->ha;
+
+	/* prevent revalidation from finding sata links in recovery */
+	mutex_lock(&ha->disco_mutex);
+	if (test_bit(SAS_HA_ATA_EH_ACTIVE, &ha->state)) {
+		SAS_DPRINTK("REVALIDATION DEFERRED on port %d, pid:%d\n",
+			    port->id, task_pid_nr(current));
+		goto out;
+	}
 
 	clear_bit(DISCE_REVALIDATE_DOMAIN, &port->disc.pending);
 
 	SAS_DPRINTK("REVALIDATING DOMAIN on port %d, pid:%d\n", port->id,
 		    task_pid_nr(current));
+
 	if (port->port_dev)
 		res = sas_ex_revalidate_domain(port->port_dev);
 
 	SAS_DPRINTK("done REVALIDATING DOMAIN on port %d, pid:%d, res 0x%x\n",
 		    port->id, task_pid_nr(current), res);
+ out:
+	mutex_unlock(&ha->disco_mutex);
 }
 
 /* ---------- Events ---------- */
@@ -414,6 +463,8 @@ void sas_init_disc(struct sas_discovery *disc, struct asd_sas_port *port)
 	static const work_func_t sas_event_fns[DISC_NUM_EVENTS] = {
 		[DISCE_DISCOVER_DOMAIN] = sas_discover_domain,
 		[DISCE_REVALIDATE_DOMAIN] = sas_revalidate_domain,
+		[DISCE_PROBE] = sas_probe_sata,
+		[DISCE_DESTRUCT] = sas_destruct_devices,
 	};
 
 	disc->pending = 0;