[SCSI] libsas: fix sas_find_local_phy(), take phy references

In the direct-attached case this routine returns the phy on which this
device was first discovered.  Which is broken if we want to support
wide-targets, as this phy reference can become stale even though the
port is still active.

In the expander-attached case this routine tries to lookup the phy by
scanning the attached sas addresses of the parent expander, and BUG_ONs
if it can't find it.  However since eh and the libsas workqueue run
independently we can still be attempting device recovery via eh after
libsas has recorded the device as detached.  This is even easier to hit
now that eh is blocked while device domain rediscovery takes place, and
that libata is fed more timed out commands increasing the chances that
it will try to recover the ata device.

Arrange for dev->phy to always point to a last known good phy, it may be
stale after the port is torn down, but it will catch up for wide port
reconfigurations, and never be NULL.

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

1 files changed, 18 insertions, 20 deletions

diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index 5cc44fddfe95..94ef76316c31 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -439,30 +439,26 @@ static int sas_recover_I_T(struct domain_device *dev)
 	return res;
 }
 
-/* Find the sas_phy that's attached to this device */
-struct sas_phy *sas_find_local_phy(struct domain_device *dev)
+/* take a reference on the last known good phy for this device */
+struct sas_phy *sas_get_local_phy(struct domain_device *dev)
 {
-	struct domain_device *pdev = dev->parent;
-	struct ex_phy *exphy = NULL;
-	int i;
+	struct sas_ha_struct *ha = dev->port->ha;
+	struct sas_phy *phy;
+	unsigned long flags;
 
-	/* Directly attached device */
-	if (!pdev)
-		return dev->port->phy;
+	/* a published domain device always has a valid phy, it may be
+	 * stale, but it is never NULL
+	 */
+	BUG_ON(!dev->phy);
 
-	/* Otherwise look in the expander */
-	for (i = 0; i < pdev->ex_dev.num_phys; i++)
-		if (!memcmp(dev->sas_addr,
-			    pdev->ex_dev.ex_phy[i].attached_sas_addr,
-			    SAS_ADDR_SIZE)) {
-			exphy = &pdev->ex_dev.ex_phy[i];
-			break;
-		}
+	spin_lock_irqsave(&ha->phy_port_lock, flags);
+	phy = dev->phy;
+	get_device(&phy->dev);
+	spin_unlock_irqrestore(&ha->phy_port_lock, flags);
 
-	BUG_ON(!exphy);
-	return exphy->phy;
+	return phy;
 }
-EXPORT_SYMBOL_GPL(sas_find_local_phy);
+EXPORT_SYMBOL_GPL(sas_get_local_phy);
 
 /* Attempt to send a LUN reset message to a device */
 int sas_eh_device_reset_handler(struct scsi_cmnd *cmd)
@@ -489,7 +485,7 @@ int sas_eh_device_reset_handler(struct scsi_cmnd *cmd)
 int sas_eh_bus_reset_handler(struct scsi_cmnd *cmd)
 {
 	struct domain_device *dev = cmd_to_domain_dev(cmd);
-	struct sas_phy *phy = sas_find_local_phy(dev);
+	struct sas_phy *phy = sas_get_local_phy(dev);
 	int res;
 
 	res = sas_phy_reset(phy, 1);
@@ -497,6 +493,8 @@ int sas_eh_bus_reset_handler(struct scsi_cmnd *cmd)
 		SAS_DPRINTK("Bus reset of %s failed 0x%x\n",
 			    kobject_name(&phy->dev.kobj),
 			    res);
+	sas_put_local_phy(phy);
+
 	if (res == TMF_RESP_FUNC_SUCC || res == TMF_RESP_FUNC_COMPLETE)
 		return SUCCESS;