[SCSI] ipr: Fix a race on multiple configuration changes

In a multiple configuration change scenario a remove notification can be
followed by an immediate add notification for the same device, which
will cause the device to be removed but never added back. This patch
fixes the problem by ensuring that in such situations the device will be
added back.
Signed-off-by: Kleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/ipr.c

@@ -1301,7 +1301,7 @@ static void ipr_handle_config_change(struct ipr_ioa_cfg *ioa_cfg,
 			ipr_clear_res_target(res);
 			list_move_tail(&res->queue, &ioa_cfg->free_res_q);
 		}
-	} else if (!res->sdev) {
+	} else if (!res->sdev || res->del_from_ml) {
 		res->add_to_ml = 1;
 		if (ioa_cfg->allow_ml_add_del)
 			schedule_work(&ioa_cfg->work_q);
@@ -3104,7 +3104,10 @@ static void ipr_worker_thread(struct work_struct *work)
 				did_work = 1;
 				sdev = res->sdev;
 				if (!scsi_device_get(sdev)) {
+					if (!res->add_to_ml)
 						list_move_tail(&res->queue, &ioa_cfg->free_res_q);
+					else
+						res->del_from_ml = 0;
 					spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
 					scsi_remove_device(sdev);
 					scsi_device_put(sdev);