[PATCH 03/12] libata, libsas: introduce sched_eh and end_eh port ops

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

When managing shost->host_eh_scheduled libata assumes that there is a
1:1 shost-to-ata_port relationship.  libsas creates a 1:N relationship
so it needs to manage host_eh_scheduled cumulatively at the host level.
The sched_eh and end_eh port port ops allow libsas to track when domain
devices enter/leave the "eh-pending" state under ha->lock (previously
named ha->state_lock, but it is no longer just a lock for ha->state
changes).

Since host_eh_scheduled indicates eh without backing commands pinning
the device it can be deallocated at any time.  Move the taking of the
domain_device reference under the port_lock to guarantee that the
ata_port stays around for the duration of eh.

Cc: Tejun Heo <tj@kernel.org>
Acked-by: Jacek Danecki <jacek.danecki@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/ata/libata-core.c           |    4 ++
 drivers/ata/libata-eh.c             |   57 ++++++++++++++++++++++++++++-------
 drivers/scsi/libsas/sas_ata.c       |   38 +++++++++++++++++++++--
 drivers/scsi/libsas/sas_discover.c  |    6 ++--
 drivers/scsi/libsas/sas_event.c     |   12 ++++---
 drivers/scsi/libsas/sas_init.c      |   14 ++++-----
 drivers/scsi/libsas/sas_scsi_host.c |   27 +++++++++++++----
 include/linux/libata.h              |    4 ++
 include/scsi/libsas.h               |    4 ++
 include/scsi/sas_ata.h              |    5 +++
 10 files changed, 134 insertions(+), 37 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index e0bda9f..ea8444e 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -80,6 +80,8 @@ const struct ata_port_operations ata_base_port_ops = {
 	.prereset		= ata_std_prereset,
 	.postreset		= ata_std_postreset,
 	.error_handler		= ata_std_error_handler,
+	.sched_eh		= ata_std_sched_eh,
+	.end_eh			= ata_std_end_eh,
 };
 
 const struct ata_port_operations sata_port_ops = {
@@ -6635,6 +6637,8 @@ struct ata_port_operations ata_dummy_port_ops = {
 	.qc_prep		= ata_noop_qc_prep,
 	.qc_issue		= ata_dummy_qc_issue,
 	.error_handler		= ata_dummy_error_handler,
+	.sched_eh		= ata_std_sched_eh,
+	.end_eh			= ata_std_end_eh,
 };
 
 const struct ata_port_info ata_dummy_port_info = {
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index c61316e..4f12f63 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -793,12 +793,12 @@ void ata_scsi_port_error_handler(struct Scsi_Host *host, struct ata_port *ap)
 		ata_for_each_link(link, ap, HOST_FIRST)
 			memset(&link->eh_info, 0, sizeof(link->eh_info));
 
-		/* Clear host_eh_scheduled while holding ap->lock such
-		 * that if exception occurs after this point but
-		 * before EH completion, SCSI midlayer will
+		/* end eh (clear host_eh_scheduled) while holding
+		 * ap->lock such that if exception occurs after this
+		 * point but before EH completion, SCSI midlayer will
 		 * re-initiate EH.
 		 */
-		host->host_eh_scheduled = 0;
+		ap->ops->end_eh(ap);
 
 		spin_unlock_irqrestore(ap->lock, flags);
 		ata_eh_release(ap);
@@ -986,16 +986,13 @@ void ata_qc_schedule_eh(struct ata_queued_cmd *qc)
 }
 
 /**
- *	ata_port_schedule_eh - schedule error handling without a qc
- *	@ap: ATA port to schedule EH for
- *
- *	Schedule error handling for @ap.  EH will kick in as soon as
- *	all commands are drained.
+ * ata_std_sched_eh - non-libsas ata_ports issue eh with this common routine
+ * @ap: ATA port to schedule EH for
  *
- *	LOCKING:
+ *	LOCKING: inherited from ata_port_schedule_eh
  *	spin_lock_irqsave(host lock)
  */
-void ata_port_schedule_eh(struct ata_port *ap)
+void ata_std_sched_eh(struct ata_port *ap)
 {
 	WARN_ON(!ap->ops->error_handler);
 
@@ -1007,6 +1004,44 @@ void ata_port_schedule_eh(struct ata_port *ap)
 
 	DPRINTK("port EH scheduled\n");
 }
+EXPORT_SYMBOL_GPL(ata_std_sched_eh);
+
+/**
+ * ata_std_end_eh - non-libsas ata_ports complete eh with this common routine
+ * @ap: ATA port to end EH for
+ *
+ * In the libata object model there is a 1:1 mapping of ata_port to
+ * shost, so host fields can be directly manipulated under ap->lock, in
+ * the libsas case we need to hold a lock at the ha->level to coordinate
+ * these events.
+ *
+ *	LOCKING:
+ *	spin_lock_irqsave(host lock)
+ */
+void ata_std_end_eh(struct ata_port *ap)
+{
+	struct Scsi_Host *host = ap->scsi_host;
+
+	host->host_eh_scheduled = 0;
+}
+EXPORT_SYMBOL(ata_std_end_eh);
+
+
+/**
+ *	ata_port_schedule_eh - schedule error handling without a qc
+ *	@ap: ATA port to schedule EH for
+ *
+ *	Schedule error handling for @ap.  EH will kick in as soon as
+ *	all commands are drained.
+ *
+ *	LOCKING:
+ *	spin_lock_irqsave(host lock)
+ */
+void ata_port_schedule_eh(struct ata_port *ap)
+{
+	/* see: ata_std_sched_eh, unless you know better */
+	ap->ops->sched_eh(ap);
+}
 
 static int ata_do_link_abort(struct ata_port *ap, struct ata_link *link)
 {
diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index bc83704..545b78d 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -523,6 +523,31 @@ static void sas_ata_set_dmamode(struct ata_port *ap, struct ata_device *ata_dev)
 		i->dft->lldd_ata_set_dmamode(dev);
 }
 
+static void sas_ata_sched_eh(struct ata_port *ap)
+{
+	struct domain_device *dev = ap->private_data;
+	struct sas_ha_struct *ha = dev->port->ha;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ha->lock, flags);
+	if (!test_and_set_bit(SAS_DEV_EH_PENDING, &dev->state))
+		ha->eh_active++;
+	ata_std_sched_eh(ap);
+	spin_unlock_irqrestore(&ha->lock, flags);
+}
+
+void sas_ata_end_eh(struct ata_port *ap)
+{
+	struct domain_device *dev = ap->private_data;
+	struct sas_ha_struct *ha = dev->port->ha;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ha->lock, flags);
+	if (test_and_clear_bit(SAS_DEV_EH_PENDING, &dev->state))
+		ha->eh_active--;
+	spin_unlock_irqrestore(&ha->lock, flags);
+}
+
 static struct ata_port_operations sas_sata_ops = {
 	.prereset		= ata_std_prereset,
 	.hardreset		= sas_ata_hard_reset,
@@ -536,6 +561,8 @@ static struct ata_port_operations sas_sata_ops = {
 	.port_start		= ata_sas_port_start,
 	.port_stop		= ata_sas_port_stop,
 	.set_dmamode		= sas_ata_set_dmamode,
+	.sched_eh		= sas_ata_sched_eh,
+	.end_eh			= sas_ata_end_eh,
 };
 
 static struct ata_port_info sata_port_info = {
@@ -708,10 +735,6 @@ static void async_sas_ata_eh(void *data, async_cookie_t cookie)
 	struct ata_port *ap = dev->sata_dev.ap;
 	struct sas_ha_struct *ha = dev->port->ha;
 
-	/* hold a reference over eh since we may be racing with final
-	 * remove once all commands are completed
-	 */
-	kref_get(&dev->kref);
 	sas_ata_printk(KERN_DEBUG, dev, "dev error handler\n");
 	ata_scsi_port_error_handler(ha->core.shost, ap);
 	sas_put_device(dev);
@@ -754,6 +777,13 @@ void sas_ata_strategy_handler(struct Scsi_Host *shost)
 		list_for_each_entry(dev, &port->dev_list, dev_list_node) {
 			if (!sas_ata_dev_eh_valid(dev))
 				continue;
+
+			/* hold a reference over eh since we may be
+			 * racing with final remove once all commands
+			 * are completed
+			 */
+			kref_get(&dev->kref);
+
 			async_schedule_domain(async_sas_ata_eh, dev, &async);
 		}
 		spin_unlock(&port->dev_list_lock);
diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index c7ac882..b82949c 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -282,6 +282,8 @@ static void sas_unregister_common_dev(struct asd_sas_port *port, struct domain_d
 
 	spin_lock_irq(&port->dev_list_lock);
 	list_del_init(&dev->dev_list_node);
+	if (dev_is_sata(dev))
+		sas_ata_end_eh(dev->sata_dev.ap);
 	spin_unlock_irq(&port->dev_list_lock);
 
 	sas_put_device(dev);
@@ -479,9 +481,9 @@ static void sas_chain_event(int event, unsigned long *pending,
 	if (!test_and_set_bit(event, pending)) {
 		unsigned long flags;
 
-		spin_lock_irqsave(&ha->state_lock, flags);
+		spin_lock_irqsave(&ha->lock, flags);
 		sas_chain_work(ha, sw);
-		spin_unlock_irqrestore(&ha->state_lock, flags);
+		spin_unlock_irqrestore(&ha->lock, flags);
 	}
 }
 
diff --git a/drivers/scsi/libsas/sas_event.c b/drivers/scsi/libsas/sas_event.c
index 4e4292d..789c4d8 100644
--- a/drivers/scsi/libsas/sas_event.c
+++ b/drivers/scsi/libsas/sas_event.c
@@ -47,9 +47,9 @@ static void sas_queue_event(int event, unsigned long *pending,
 	if (!test_and_set_bit(event, pending)) {
 		unsigned long flags;
 
-		spin_lock_irqsave(&ha->state_lock, flags);
+		spin_lock_irqsave(&ha->lock, flags);
 		sas_queue_work(ha, work);
-		spin_unlock_irqrestore(&ha->state_lock, flags);
+		spin_unlock_irqrestore(&ha->lock, flags);
 	}
 }
 
@@ -61,18 +61,18 @@ void __sas_drain_work(struct sas_ha_struct *ha)
 
 	set_bit(SAS_HA_DRAINING, &ha->state);
 	/* flush submitters */
-	spin_lock_irq(&ha->state_lock);
-	spin_unlock_irq(&ha->state_lock);
+	spin_lock_irq(&ha->lock);
+	spin_unlock_irq(&ha->lock);
 
 	drain_workqueue(wq);
 
-	spin_lock_irq(&ha->state_lock);
+	spin_lock_irq(&ha->lock);
 	clear_bit(SAS_HA_DRAINING, &ha->state);
 	list_for_each_entry_safe(sw, _sw, &ha->defer_q, drain_node) {
 		list_del_init(&sw->drain_node);
 		sas_queue_work(ha, sw);
 	}
-	spin_unlock_irq(&ha->state_lock);
+	spin_unlock_irq(&ha->lock);
 }
 
 int sas_drain_work(struct sas_ha_struct *ha)
diff --git a/drivers/scsi/libsas/sas_init.c b/drivers/scsi/libsas/sas_init.c
index 10cb5ae..6909fef 100644
--- a/drivers/scsi/libsas/sas_init.c
+++ b/drivers/scsi/libsas/sas_init.c
@@ -114,7 +114,7 @@ int sas_register_ha(struct sas_ha_struct *sas_ha)
 		sas_ha->lldd_queue_size = 128; /* Sanity */
 
 	set_bit(SAS_HA_REGISTERED, &sas_ha->state);
-	spin_lock_init(&sas_ha->state_lock);
+	spin_lock_init(&sas_ha->lock);
 	mutex_init(&sas_ha->drain_mutex);
 	INIT_LIST_HEAD(&sas_ha->defer_q);
 
@@ -163,9 +163,9 @@ int sas_unregister_ha(struct sas_ha_struct *sas_ha)
 	 * events to be queued, and flush any in-progress drainers
 	 */
 	mutex_lock(&sas_ha->drain_mutex);
-	spin_lock_irq(&sas_ha->state_lock);
+	spin_lock_irq(&sas_ha->lock);
 	clear_bit(SAS_HA_REGISTERED, &sas_ha->state);
-	spin_unlock_irq(&sas_ha->state_lock);
+	spin_unlock_irq(&sas_ha->lock);
 	__sas_drain_work(sas_ha);
 	mutex_unlock(&sas_ha->drain_mutex);
 
@@ -411,9 +411,9 @@ static int queue_phy_reset(struct sas_phy *phy, int hard_reset)
 	d->reset_result = 0;
 	d->hard_reset = hard_reset;
 
-	spin_lock_irq(&ha->state_lock);
+	spin_lock_irq(&ha->lock);
 	sas_queue_work(ha, &d->reset_work);
-	spin_unlock_irq(&ha->state_lock);
+	spin_unlock_irq(&ha->lock);
 
 	rc = sas_drain_work(ha);
 	if (rc == 0)
@@ -438,9 +438,9 @@ static int queue_phy_enable(struct sas_phy *phy, int enable)
 	d->enable_result = 0;
 	d->enable = enable;
 
-	spin_lock_irq(&ha->state_lock);
+	spin_lock_irq(&ha->lock);
 	sas_queue_work(ha, &d->enable_work);
-	spin_unlock_irq(&ha->state_lock);
+	spin_unlock_irq(&ha->lock);
 
 	rc = sas_drain_work(ha);
 	if (rc == 0)
diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index 17339e5..52d5b01 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -667,16 +667,20 @@ static void sas_eh_handle_sas_errors(struct Scsi_Host *shost, struct list_head *
 	goto out;
 }
 
+
 void sas_scsi_recover_host(struct Scsi_Host *shost)
 {
 	struct sas_ha_struct *ha = SHOST_TO_SAS_HA(shost);
-	unsigned long flags;
 	LIST_HEAD(eh_work_q);
+	int tries = 0;
+	bool retry;
 
-	spin_lock_irqsave(shost->host_lock, flags);
+retry:
+	tries++;
+	retry = true;
+	spin_lock_irq(shost->host_lock);
 	list_splice_init(&shost->eh_cmd_q, &eh_work_q);
-	shost->host_eh_scheduled = 0;
-	spin_unlock_irqrestore(shost->host_lock, flags);
+	spin_unlock_irq(shost->host_lock);
 
 	SAS_DPRINTK("Enter %s busy: %d failed: %d\n",
 		    __func__, shost->host_busy, shost->host_failed);
@@ -710,8 +714,19 @@ out:
 
 	scsi_eh_flush_done_q(&ha->eh_done_q);
 
-	SAS_DPRINTK("--- Exit %s: busy: %d failed: %d\n",
-		    __func__, shost->host_busy, shost->host_failed);
+	/* check if any new eh work was scheduled during the last run */
+	spin_lock_irq(&ha->lock);
+	if (ha->eh_active == 0) {
+		shost->host_eh_scheduled = 0;
+		retry = false;
+	}
+	spin_unlock_irq(&ha->lock);
+
+	if (retry)
+		goto retry;
+
+	SAS_DPRINTK("--- Exit %s: busy: %d failed: %d tries: %d\n",
+		    __func__, shost->host_busy, shost->host_failed, tries);
 }
 
 enum blk_eh_timer_return sas_scsi_timed_out(struct scsi_cmnd *cmd)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 42378d6..83ff256 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -845,6 +845,8 @@ struct ata_port_operations {
 	void (*error_handler)(struct ata_port *ap);
 	void (*lost_interrupt)(struct ata_port *ap);
 	void (*post_internal_cmd)(struct ata_queued_cmd *qc);
+	void (*sched_eh)(struct ata_port *ap);
+	void (*end_eh)(struct ata_port *ap);
 
 	/*
 	 * Optional features
@@ -1165,6 +1167,8 @@ extern void ata_do_eh(struct ata_port *ap, ata_prereset_fn_t prereset,
 		      ata_reset_fn_t softreset, ata_reset_fn_t hardreset,
 		      ata_postreset_fn_t postreset);
 extern void ata_std_error_handler(struct ata_port *ap);
+extern void ata_std_sched_eh(struct ata_port *ap);
+extern void ata_std_end_eh(struct ata_port *ap);
 extern int ata_link_nr_enabled(struct ata_link *link);
 
 /*
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index f4f1c96..2718b24 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -177,6 +177,7 @@ struct sata_device {
 enum {
 	SAS_DEV_GONE,
 	SAS_DEV_DESTROY,
+	SAS_DEV_EH_PENDING,
 };
 
 struct domain_device {
@@ -384,7 +385,8 @@ struct sas_ha_struct {
 	struct list_head  defer_q; /* work queued while draining */
 	struct mutex	  drain_mutex;
 	unsigned long	  state;
-	spinlock_t 	  state_lock;
+	spinlock_t	  lock;
+	int		  eh_active;
 
 	struct mutex disco_mutex;
 
diff --git a/include/scsi/sas_ata.h b/include/scsi/sas_ata.h
index cdccd2e..cae55b6 100644
--- a/include/scsi/sas_ata.h
+++ b/include/scsi/sas_ata.h
@@ -45,6 +45,7 @@ void sas_ata_eh(struct Scsi_Host *shost, struct list_head *work_q,
 void sas_ata_schedule_reset(struct domain_device *dev);
 void sas_ata_wait_eh(struct domain_device *dev);
 void sas_probe_sata(struct asd_sas_port *port);
+void sas_ata_end_eh(struct ata_port *ap);
 #else
 
 
@@ -85,6 +86,10 @@ static inline int sas_get_ata_info(struct domain_device *dev, struct ex_phy *phy
 {
 	return 0;
 }
+
+static inline void sas_ata_end_eh(struct ata_port *ap)
+{
+}
 #endif
 
 #endif /* _SAS_ATA_H_ */