[SCSI] libsas: introduce sas_drain_work()
When an lldd invokes ->notify_port_event() it can trigger a chain of libsas
events to:
1/ form the port and find the direct attached device
2/ if the attached device is an expander perform domain discovery
A call to flush_workqueue() will only flush the initial port formation work.
Currently libsas users need to call scsi_flush_work() up to the max depth of
chain (which will grow from 2 to 3 when ata discovery is moved to its own
discovery event). Instead of open coding multiple calls switch to use
drain_workqueue() to flush sas work.
drain_workqueue() does not handle new work submitted during the drain so
libsas needs a bit of infrastructure to hold off unchained work submissions
while a drain is in flight. A lldd ->notify() event is considered 'unchained'
while a sas_discover_event() is 'chained'. As Tejun notes:
"For now, I think it would be best to add private wrapper in libsas to
support deferring unchained work items while draining."
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/drivers/scsi/libsas/sas_init.c b/drivers/scsi/libsas/sas_init.c
index da244e6..572b943 100644
--- a/drivers/scsi/libsas/sas_init.c
+++ b/drivers/scsi/libsas/sas_init.c
@@ -114,6 +114,8 @@
set_bit(SAS_HA_REGISTERED, &sas_ha->state);
spin_lock_init(&sas_ha->state_lock);
+ mutex_init(&sas_ha->drain_mutex);
+ INIT_LIST_HEAD(&sas_ha->defer_q);
error = sas_register_phys(sas_ha);
if (error) {
@@ -157,12 +159,13 @@
{
unsigned long flags;
- /* Set the state to unregistered to avoid further
- * events to be queued */
+ /* Set the state to unregistered to avoid further unchained
+ * events to be queued
+ */
spin_lock_irqsave(&sas_ha->state_lock, flags);
clear_bit(SAS_HA_REGISTERED, &sas_ha->state);
spin_unlock_irqrestore(&sas_ha->state_lock, flags);
- scsi_flush_work(sas_ha->core.shost);
+ sas_drain_work(sas_ha);
sas_unregister_ports(sas_ha);