[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, 15 insertions, 3 deletions

diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 9d9330ae4213..9421bae8af1a 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);