[SCSI] zfcp: Allow running unit/LUN shutdown without acquiring reference

With the change for the LUN data to be part of the scsi_device, the
slave_destroy callback will be the final call to the
zfcp_erp_unit_shutdown function. The erp tries to acquire a reference
to run the action asynchronously and fail, if it cannot get the
reference. But calling scsi_device_get from slave_destroy will fail,
because the scsi_device is already in the state SDEV_DEL.

Introduce a new call into the zfcp erp to solve this: The function
zfcp_erp_unit_shutdown_wait will close the LUN and wait for the erp to
finish without acquiring an additional reference. The wait allows to
omit the reference; the caller waiting for the erp to finish already
has a reference that holds the struct in place.

Reviewed-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 63 insertions, 36 deletions

diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
index 160b432c907f..50514b4c8732 100644
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -21,6 +21,7 @@ enum zfcp_erp_act_flags {
         ZFCP_STATUS_ERP_DISMISSING      = 0x00100000,
         ZFCP_STATUS_ERP_DISMISSED       = 0x00200000,
         ZFCP_STATUS_ERP_LOWMEM          = 0x00400000,
+        ZFCP_STATUS_ERP_NO_REF          = 0x00800000,
 };
 
 enum zfcp_erp_steps {
@@ -169,22 +170,22 @@ static int zfcp_erp_required_act(int want, struct zfcp_adapter *adapter,
         return need;
 }
 
-static struct zfcp_erp_action *zfcp_erp_setup_act(int need,
+static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
                                                   struct zfcp_adapter *adapter,
                                                   struct zfcp_port *port,
                                                   struct zfcp_unit *unit)
 {
         struct zfcp_erp_action *erp_action;
-        u32 status = 0;
 
         switch (need) {
         case ZFCP_ERP_ACTION_REOPEN_UNIT:
-                if (!get_device(&unit->dev))
-                        return NULL;
+                if (!(act_status & ZFCP_STATUS_ERP_NO_REF))
+                        if (!get_device(&unit->dev))
+                                return NULL;
                 atomic_set_mask(ZFCP_STATUS_COMMON_ERP_INUSE, &unit->status);
                 erp_action = &unit->erp_action;
                 if (!(atomic_read(&unit->status) & ZFCP_STATUS_COMMON_RUNNING))
-                        status = ZFCP_STATUS_ERP_CLOSE_ONLY;
+                        act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
                 break;
 
         case ZFCP_ERP_ACTION_REOPEN_PORT:
@@ -195,7 +196,7 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need,
                 atomic_set_mask(ZFCP_STATUS_COMMON_ERP_INUSE, &port->status);
                 erp_action = &port->erp_action;
                 if (!(atomic_read(&port->status) & ZFCP_STATUS_COMMON_RUNNING))
-                        status = ZFCP_STATUS_ERP_CLOSE_ONLY;
+                        act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
                 break;
 
         case ZFCP_ERP_ACTION_REOPEN_ADAPTER:
@@ -205,7 +206,7 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need,
                 erp_action = &adapter->erp_action;
                 if (!(atomic_read(&adapter->status) &
                       ZFCP_STATUS_COMMON_RUNNING))
-                        status = ZFCP_STATUS_ERP_CLOSE_ONLY;
+                        act_status |= ZFCP_STATUS_ERP_CLOSE_ONLY;
                 break;
 
         default:
@@ -217,14 +218,15 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need,
         erp_action->port = port;
         erp_action->unit = unit;
         erp_action->action = need;
-        erp_action->status = status;
+        erp_action->status = act_status;
 
         return erp_action;
 }
 
 static int zfcp_erp_action_enqueue(int want, struct zfcp_adapter *adapter,
                                    struct zfcp_port *port,
-                                   struct zfcp_unit *unit, char *id, void *ref)
+                                   struct zfcp_unit *unit, char *id, void *ref,
+                                   u32 act_status)
 {
         int retval = 1, need;
         struct zfcp_erp_action *act = NULL;
@@ -236,10 +238,10 @@ static int zfcp_erp_action_enqueue(int want, struct zfcp_adapter *adapter,
         if (!need)
                 goto out;
 
-        atomic_set_mask(ZFCP_STATUS_ADAPTER_ERP_PENDING, &adapter->status);
-        act = zfcp_erp_setup_act(need, adapter, port, unit);
+        act = zfcp_erp_setup_act(need, act_status, adapter, port, unit);
         if (!act)
                 goto out;
+        atomic_set_mask(ZFCP_STATUS_ADAPTER_ERP_PENDING, &adapter->status);
         ++adapter->erp_total_count;
         list_add_tail(&act->list, &adapter->erp_ready_head);
         wake_up(&adapter->erp_ready_wq);
@@ -262,7 +264,7 @@ static int _zfcp_erp_adapter_reopen(struct zfcp_adapter *adapter,
                 return -EIO;
         }
         return zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_ADAPTER,
-                                       adapter, NULL, NULL, id, ref);
+                                       adapter, NULL, NULL, id, ref, 0);
 }
 
 /**
@@ -285,7 +287,7 @@ void zfcp_erp_adapter_reopen(struct zfcp_adapter *adapter, int clear,
                 zfcp_erp_adapter_failed(adapter, "erareo1", NULL);
         else
                 zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_ADAPTER, adapter,
-                                        NULL, NULL, id, ref);
+                                        NULL, NULL, id, ref, 0);
         write_unlock_irqrestore(&adapter->erp_lock, flags);
 }
 
@@ -317,20 +319,6 @@ void zfcp_erp_port_shutdown(struct zfcp_port *port, int clear, char *id,
         zfcp_erp_port_reopen(port, clear | flags, id, ref);
 }
 
-/**
- * zfcp_erp_unit_shutdown - Shutdown unit
- * @unit: Unit to shut down.
- * @clear: Status flags to clear.
- * @id: Id for debug trace event.
- * @ref: Reference for debug trace event.
- */
-void zfcp_erp_unit_shutdown(struct zfcp_unit *unit, int clear, char *id,
-                            void *ref)
-{
-        int flags = ZFCP_STATUS_COMMON_RUNNING | ZFCP_STATUS_COMMON_ERP_FAILED;
-        zfcp_erp_unit_reopen(unit, clear | flags, id, ref);
-}
-
 static void zfcp_erp_port_block(struct zfcp_port *port, int clear)
 {
         zfcp_erp_modify_port_status(port, "erpblk1", NULL,
@@ -348,7 +336,7 @@ static void _zfcp_erp_port_forced_reopen(struct zfcp_port *port,
                 return;
 
         zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_PORT_FORCED,
-                                port->adapter, port, NULL, id, ref);
+                                port->adapter, port, NULL, id, ref, 0);
 }
 
 /**
@@ -381,7 +369,7 @@ static int _zfcp_erp_port_reopen(struct zfcp_port *port, int clear, char *id,
         }
 
         return zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_PORT,
-                                       port->adapter, port, NULL, id, ref);
+                                       port->adapter, port, NULL, id, ref, 0);
 }
 
 /**
@@ -412,7 +400,7 @@ static void zfcp_erp_unit_block(struct zfcp_unit *unit, int clear_mask)
 }
 
 static void _zfcp_erp_unit_reopen(struct zfcp_unit *unit, int clear, char *id,
-                                  void *ref)
+                                  void *ref, u32 act_status)
 {
         struct zfcp_adapter *adapter = unit->port->adapter;
 
@@ -422,7 +410,7 @@ static void _zfcp_erp_unit_reopen(struct zfcp_unit *unit, int clear, char *id,
                 return;
 
         zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_UNIT,
-                                adapter, unit->port, unit, id, ref);
+                                adapter, unit->port, unit, id, ref, act_status);
 }
 
 /**
@@ -439,8 +427,45 @@ void zfcp_erp_unit_reopen(struct zfcp_unit *unit, int clear, char *id,
         struct zfcp_adapter *adapter = port->adapter;
 
         write_lock_irqsave(&adapter->erp_lock, flags);
-        _zfcp_erp_unit_reopen(unit, clear, id, ref);
+        _zfcp_erp_unit_reopen(unit, clear, id, ref, 0);
+        write_unlock_irqrestore(&adapter->erp_lock, flags);
+}
+
+/**
+ * zfcp_erp_unit_shutdown - Shutdown unit
+ * @unit: Unit to shut down.
+ * @clear: Status flags to clear.
+ * @id: Id for debug trace event.
+ * @ref: Reference for debug trace event.
+ */
+void zfcp_erp_unit_shutdown(struct zfcp_unit *unit, int clear, char *id,
+                            void *ref)
+{
+        int flags = ZFCP_STATUS_COMMON_RUNNING | ZFCP_STATUS_COMMON_ERP_FAILED;
+        zfcp_erp_unit_reopen(unit, clear | flags, id, ref);
+}
+
+/**
+ * zfcp_erp_unit_shutdown_wait - Shutdown unit and wait for erp completion
+ * @unit: Unit to shut down.
+ * @id: Id for debug trace event.
+ *
+ * Do not acquire a reference for the unit when creating the ERP
+ * action. It is safe, because this function waits for the ERP to
+ * complete first.
+ */
+void zfcp_erp_unit_shutdown_wait(struct zfcp_unit *unit, char *id)
+{
+        unsigned long flags;
+        struct zfcp_port *port = unit->port;
+        struct zfcp_adapter *adapter = port->adapter;
+        int clear = ZFCP_STATUS_COMMON_RUNNING | ZFCP_STATUS_COMMON_ERP_FAILED;
+
+        write_lock_irqsave(&adapter->erp_lock, flags);
+        _zfcp_erp_unit_reopen(unit, clear, id, NULL, ZFCP_STATUS_ERP_NO_REF);
         write_unlock_irqrestore(&adapter->erp_lock, flags);
+
+        zfcp_erp_wait(adapter);
 }
 
 static int status_change_set(unsigned long mask, atomic_t *status)
@@ -566,7 +591,7 @@ static void _zfcp_erp_unit_reopen_all(struct zfcp_port *port, int clear,
 
         read_lock(&port->unit_list_lock);
         list_for_each_entry(unit, &port->unit_list, list)
-                _zfcp_erp_unit_reopen(unit, clear, id, ref);
+                _zfcp_erp_unit_reopen(unit, clear, id, ref, 0);
         read_unlock(&port->unit_list_lock);
 }
 
@@ -583,7 +608,7 @@ static void zfcp_erp_strategy_followup_failed(struct zfcp_erp_action *act)
                 _zfcp_erp_port_reopen(act->port, 0, "ersff_3", NULL);
                 break;
         case ZFCP_ERP_ACTION_REOPEN_UNIT:
-                _zfcp_erp_unit_reopen(act->unit, 0, "ersff_4", NULL);
+                _zfcp_erp_unit_reopen(act->unit, 0, "ersff_4", NULL, 0);
                 break;
         }
 }
@@ -1143,7 +1168,7 @@ static int zfcp_erp_strategy_statechange(struct zfcp_erp_action *act, int ret)
                 if (zfcp_erp_strat_change_det(&unit->status, erp_status)) {
                         _zfcp_erp_unit_reopen(unit,
                                               ZFCP_STATUS_COMMON_ERP_FAILED,
-                                              "ersscg3", NULL);
+                                              "ersscg3", NULL, 0);
                         return ZFCP_ERP_EXIT;
                 }
                 break;
@@ -1191,7 +1216,8 @@ static void zfcp_erp_action_cleanup(struct zfcp_erp_action *act, int result)
 
         switch (act->action) {
         case ZFCP_ERP_ACTION_REOPEN_UNIT:
-                put_device(&unit->dev);
+                if (!(act->status & ZFCP_STATUS_ERP_NO_REF))
+                        put_device(&unit->dev);
                 break;
 
         case ZFCP_ERP_ACTION_REOPEN_PORT:
diff --git a/drivers/s390/scsi/zfcp_ext.h b/drivers/s390/scsi/zfcp_ext.h
index 5c3966eaca51..3c90604076e0 100644
--- a/drivers/s390/scsi/zfcp_ext.h
+++ b/drivers/s390/scsi/zfcp_ext.h
@@ -80,6 +80,7 @@ extern void zfcp_erp_modify_unit_status(struct zfcp_unit *, char *, void *, u32,
                                         int);
 extern void zfcp_erp_unit_reopen(struct zfcp_unit *, int, char *, void *);
 extern void zfcp_erp_unit_shutdown(struct zfcp_unit *, int, char *, void *);
+extern void zfcp_erp_unit_shutdown_wait(struct zfcp_unit *, char *);
 extern void zfcp_erp_unit_failed(struct zfcp_unit *, char *, void *);
 extern int  zfcp_erp_thread_setup(struct zfcp_adapter *);
 extern void zfcp_erp_thread_kill(struct zfcp_adapter *);