[PATCH v2 09/28] libsas: prevent domain rediscovery competing with ata error handling

[Dan Williams <dan.j.williams@intel.com>]

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->eh_mutex) to block ata eh while rediscovery 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 a new cleanup state for domain devices to libsas
'allocated-not-probed'.  In this state dev->rphy points to a rphy that
is known to have been through a sas_rphy_add() event.  At
sas_unregister_dev() time check if this device is still pending probe
and cleanup accordingly.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/scsi/libsas/sas_ata.c      |   45 +++++++++++++++++++++++++++---
 drivers/scsi/libsas/sas_discover.c |   54 ++++++++++++++++++++++++++++++++----
 drivers/scsi/libsas/sas_expander.c |    5 +--
 drivers/scsi/libsas/sas_init.c     |    2 +
 drivers/scsi/libsas/sas_internal.h |    1 +
 drivers/scsi/libsas/sas_port.c     |    2 +
 drivers/scsi/scsi_transport_sas.c  |   18 ++++++++++--
 include/scsi/libsas.h              |   10 +++++--
 include/scsi/sas_ata.h             |    5 +++
 include/scsi/scsi_transport_sas.h  |    1 +
 10 files changed, 125 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index 0489001..4b91c74 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -753,6 +753,35 @@ static int sas_discover_sata_pm(struct domain_device *dev)
 	return -ENODEV;
 }
 
+void sas_probe_sata(struct work_struct *work)
+{
+	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_PROBE, &port->disc.pending);
+
+	list_for_each_entry_safe(dev, n, &port->disco_list, disco_list_node) {
+		int err;
+
+		spin_lock_irq(&port->dev_list_lock);
+		list_add_tail(&dev->dev_list_node, &port->dev_list);
+		spin_unlock_irq(&port->dev_list_lock);
+
+		err = sas_rphy_add(dev->rphy);
+
+		if (err) {
+			SAS_DPRINTK("%s: for %s device %16llx returned %d\n",
+				    __func__, dev->parent ? "exp-attached" :
+							    "direct-attached",
+				    SAS_ADDR(dev->sas_addr), err);
+			sas_unregister_dev(port, dev);
+		} else
+			list_del_init(&dev->disco_list_node);
+	}
+}
+
 /**
  * sas_discover_sata -- discover an STP/SATA domain device
  * @dev: pointer to struct domain_device of interest
@@ -789,10 +818,15 @@ int sas_discover_sata(struct domain_device *dev)
 		break;
 	}
 	sas_notify_lldd_dev_gone(dev);
-	if (!res) {
-		sas_notify_lldd_dev_found(dev);
-		res = sas_rphy_add(dev->rphy);
-	}
+
+	if (res)
+		return res;
+
+	res = sas_notify_lldd_dev_found(dev);
+	if (res)
+		return res;
+
+	sas_discover_event(dev->port, DISCE_PROBE);
 
 	return res;
 }
@@ -800,7 +834,9 @@ int sas_discover_sata(struct domain_device *dev)
 void sas_ata_strategy_handler(struct Scsi_Host *shost)
 {
 	struct scsi_device *sdev;
+	struct sas_ha_struct *sas_ha = SHOST_TO_SAS_HA(shost);
 
+	mutex_lock(&sas_ha->eh_mutex);
 	shost_for_each_device(sdev, shost) {
 		struct domain_device *ddev = sdev_to_domain_dev(sdev);
 		struct ata_port *ap = ddev->sata_dev.ap;
@@ -811,6 +847,7 @@ void sas_ata_strategy_handler(struct Scsi_Host *shost)
 		ata_port_printk(ap, KERN_DEBUG, "sas eh calling libata port error handler");
 		ata_scsi_port_error_handler(shost, ap);
 	}
+	mutex_unlock(&sas_ha->eh_mutex);
 }
 
 int sas_ata_timed_out(struct scsi_cmnd *cmd, struct sas_task *task,
diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index 32e0117..eca9927 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 +260,42 @@ 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, dev_list_node) {
 		sas_remove_children(&dev->rphy->dev);
 		sas_rphy_delete(dev->rphy);
 		dev->rphy = NULL;
+		sas_unregister_common_dev(port, dev);
+	}
+}
+
+void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
+{
+	if (!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) {
+		sas_rphy_unlink(dev->rphy);
+
+		spin_lock_irq(&port->dev_list_lock);
+		list_move_tail(&dev->dev_list_node, &port->destroy_list);
+		spin_unlock_irq(&port->dev_list_lock);
+
+		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 +304,8 @@ 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 +370,7 @@ 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);
@@ -358,8 +394,12 @@ static void sas_revalidate_domain(struct work_struct *work)
 
 	SAS_DPRINTK("REVALIDATING DOMAIN on port %d, pid:%d\n", port->id,
 		    task_pid_nr(current));
+
+	/* prevent rediscovery from finding sata links in recovery */
+	mutex_lock(&port->ha->eh_mutex);
 	if (port->port_dev)
 		res = sas_ex_revalidate_domain(port->port_dev);
+	mutex_unlock(&port->ha->eh_mutex);
 
 	SAS_DPRINTK("done REVALIDATING DOMAIN on port %d, pid:%d, res 0x%x\n",
 		    port->id, task_pid_nr(current), res);
@@ -414,6 +454,8 @@ 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;
diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 15d2239..c3846cf 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -704,9 +704,7 @@ static struct domain_device *sas_ex_discover_end_dev(
 
 		child->rphy = rphy;
 
-		spin_lock_irq(&parent->port->dev_list_lock);
-		list_add_tail(&child->dev_list_node, &parent->port->dev_list);
-		spin_unlock_irq(&parent->port->dev_list_lock);
+		list_add_tail(&child->disco_list_node, &parent->port->disco_list);
 
 		res = sas_discover_sata(child);
 		if (res) {
@@ -756,6 +754,7 @@ static struct domain_device *sas_ex_discover_end_dev(
 	sas_rphy_free(child->rphy);
 	child->rphy = NULL;
 
+	list_del(&child->disco_list_node);
 	spin_lock_irq(&parent->port->dev_list_lock);
 	list_del(&child->dev_list_node);
 	spin_unlock_irq(&parent->port->dev_list_lock);
diff --git a/drivers/scsi/libsas/sas_init.c b/drivers/scsi/libsas/sas_init.c
index 572b943..0cca72a 100644
--- a/drivers/scsi/libsas/sas_init.c
+++ b/drivers/scsi/libsas/sas_init.c
@@ -104,6 +104,7 @@ int sas_register_ha(struct sas_ha_struct *sas_ha)
 {
 	int error = 0;
 
+	mutex_init(&sas_ha->eh_mutex);
 	spin_lock_init(&sas_ha->phy_port_lock);
 	sas_hash_addr(sas_ha->hashed_sas_addr, sas_ha->sas_addr);
 
@@ -168,6 +169,7 @@ int sas_unregister_ha(struct sas_ha_struct *sas_ha)
 	sas_drain_work(sas_ha);
 
 	sas_unregister_ports(sas_ha);
+	sas_drain_work(sas_ha);
 
 	if (sas_ha->lldd_max_execute_num > 1) {
 		sas_shutdown_queue(sas_ha);
diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index 948ea64..e21c245 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -138,6 +138,7 @@ static inline struct domain_device *sas_alloc_device(void)
 	if (dev) {
 		INIT_LIST_HEAD(&dev->siblings);
 		INIT_LIST_HEAD(&dev->dev_list_node);
+		INIT_LIST_HEAD(&dev->disco_list_node);
 		kref_init(&dev->kref);
 	}
 	return dev;
diff --git a/drivers/scsi/libsas/sas_port.c b/drivers/scsi/libsas/sas_port.c
index a47c7a7..e8e68d0 100644
--- a/drivers/scsi/libsas/sas_port.c
+++ b/drivers/scsi/libsas/sas_port.c
@@ -277,6 +277,8 @@ static void sas_init_port(struct asd_sas_port *port,
 	memset(port, 0, sizeof(*port));
 	port->id = i;
 	INIT_LIST_HEAD(&port->dev_list);
+	INIT_LIST_HEAD(&port->disco_list);
+	INIT_LIST_HEAD(&port->destroy_list);
 	spin_lock_init(&port->phy_list_lock);
 	INIT_LIST_HEAD(&port->phy_list);
 	port->ha = sas_ha;
diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 9d9330a..9421bae 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -1603,6 +1603,20 @@ sas_rphy_delete(struct sas_rphy *rphy)
 EXPORT_SYMBOL(sas_rphy_delete);
 
 /**
+ * sas_rphy_unlink  -  unlink SAS remote PHY
+ * @rphy:	SAS remote phy to unlink from its parent port
+ *
+ * Removes port reference to an rphy
+ */
+void sas_rphy_unlink(struct sas_rphy *rphy)
+{
+	struct sas_port *parent = dev_to_sas_port(rphy->dev.parent);
+
+	parent->rphy = NULL;
+}
+EXPORT_SYMBOL(sas_rphy_unlink);
+
+/**
  * sas_rphy_remove  -  remove SAS remote PHY
  * @rphy:	SAS remote phy to remove
  *
@@ -1612,7 +1626,6 @@ void
 sas_rphy_remove(struct sas_rphy *rphy)
 {
 	struct device *dev = &rphy->dev;
-	struct sas_port *parent = dev_to_sas_port(dev->parent);
 
 	switch (rphy->identify.device_type) {
 	case SAS_END_DEVICE:
@@ -1626,10 +1639,9 @@ sas_rphy_remove(struct sas_rphy *rphy)
 		break;
 	}
 
+	sas_rphy_unlink(rphy);
 	transport_remove_device(dev);
 	device_del(dev);
-
-	parent->rphy = NULL;
 }
 EXPORT_SYMBOL(sas_rphy_remove);
 
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 42900fa..8ada830 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -86,7 +86,9 @@ enum discover_event {
 	DISCE_DISCOVER_DOMAIN   = 0U,
 	DISCE_REVALIDATE_DOMAIN = 1,
 	DISCE_PORT_GONE         = 2,
-	DISC_NUM_EVENTS 	= 3,
+	DISCE_PROBE		= 3,
+	DISCE_DESTRUCT		= 4,
+	DISC_NUM_EVENTS		= 5,
 };
 
 /* ---------- Expander Devices ---------- */
@@ -188,6 +190,7 @@ struct domain_device {
         struct asd_sas_port *port;        /* shortcut to root of the tree */
 
         struct list_head dev_list_node;
+	struct list_head disco_list_node;
 
         enum sas_protocol    iproto;
         enum sas_protocol    tproto;
@@ -223,7 +226,6 @@ struct sas_discovery {
 	int    max_level;
 };
 
-
 /* The port struct is Class:RW, driver:RO */
 struct asd_sas_port {
 /* private: */
@@ -233,6 +235,8 @@ struct asd_sas_port {
 	struct domain_device *port_dev;
 	spinlock_t dev_list_lock;
 	struct list_head dev_list;
+	struct list_head disco_list;
+	struct list_head destroy_list;
 	enum   sas_linkrate linkrate;
 
 	struct sas_phy *phy;
@@ -343,6 +347,8 @@ struct sas_ha_struct {
 	unsigned long	  state;
 	spinlock_t 	  state_lock;
 
+	struct mutex eh_mutex;
+
 	struct scsi_core core;
 
 /* public: */
diff --git a/include/scsi/sas_ata.h b/include/scsi/sas_ata.h
index 7d5013f..557fc9a 100644
--- a/include/scsi/sas_ata.h
+++ b/include/scsi/sas_ata.h
@@ -45,6 +45,7 @@ int sas_ata_timed_out(struct scsi_cmnd *cmd, struct sas_task *task,
 		      enum blk_eh_timer_return *rtn);
 int sas_ata_eh(struct Scsi_Host *shost, struct list_head *work_q,
 	       struct list_head *done_q);
+void sas_probe_sata(struct work_struct *work);
 
 #else
 
@@ -78,6 +79,10 @@ static inline int sas_ata_eh(struct Scsi_Host *shost, struct list_head *work_q,
 	return 0;
 }
 
+static inline void sas_probe_sata(struct work_struct *work)
+{
+}
+
 #endif
 
 #endif /* _SAS_ATA_H_ */
diff --git a/include/scsi/scsi_transport_sas.h b/include/scsi/scsi_transport_sas.h
index ffeebc3..6d14daa 100644
--- a/include/scsi/scsi_transport_sas.h
+++ b/include/scsi/scsi_transport_sas.h
@@ -194,6 +194,7 @@ void sas_rphy_free(struct sas_rphy *);
 extern int sas_rphy_add(struct sas_rphy *);
 extern void sas_rphy_remove(struct sas_rphy *);
 extern void sas_rphy_delete(struct sas_rphy *);
+extern void sas_rphy_unlink(struct sas_rphy *);
 extern int scsi_is_sas_rphy(const struct device *);
 
 struct sas_port *sas_port_alloc(struct device *, int);