[SCSI] zfcp: Hold queue lock when checking port/unit handle for FCP command

We need to hold the queue-lock when checking whether we still have a valid
unit/port handle for the FCP command, i.e whether we can issue this request for
this unit/port. If the error recovery is about to close this unit/port, then it
competes for the queue-lock. If the close request issued by the error recovery
wins, then it is guaranteed that this unit/port has been blocked for other
requests.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Martin Peschke <mp3@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index 908e8b2..17c251c 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -3593,6 +3593,12 @@
 		goto failed_req_create;
 	}
 
+	if (unlikely(!atomic_test_mask(ZFCP_STATUS_COMMON_UNBLOCKED,
+			&unit->status))) {
+		retval = -EBUSY;
+		goto unit_blocked;
+	}
+
 	zfcp_unit_get(unit);
 	fsf_req->unit = unit;
 
@@ -3733,6 +3739,7 @@
  send_failed:
  no_fit:
  failed_scsi_cmnd:
+ unit_blocked:
 	zfcp_unit_put(unit);
 	zfcp_fsf_req_free(fsf_req);
 	fsf_req = NULL;