scsi: core: add scsi_host_complete_all_commands() helper

Add a helper scsi_host_complete_all_commands() to terminate all outstanding
commands on a SCSI host.

Link: https://lore.kernel.org/r/20200228075318.91255-3-hare@suse.de
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hosts.c

@@ -650,3 +650,31 @@ void scsi_flush_work(struct Scsi_Host *shost)
 	flush_workqueue(shost->work_q);
 }
 EXPORT_SYMBOL_GPL(scsi_flush_work);
+
+static bool complete_all_cmds_iter(struct request *rq, void *data, bool rsvd)
+{
+	struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(rq);
+	int status = *(int *)data;
+
+	scsi_dma_unmap(scmd);
+	scmd->result = status << 16;
+	scmd->scsi_done(scmd);
+	return true;
+}
+
+/**
+ * scsi_host_complete_all_commands - Terminate all running commands
+ * @shost:	Scsi Host on which commands should be terminated
+ * @status:	Status to be set for the terminated commands
+ *
+ * There is no protection against modification of the number
+ * of outstanding commands. It is the responsibility of the
+ * caller to ensure that concurrent I/O submission and/or
+ * completion is stopped when calling this function.
+ */
+void scsi_host_complete_all_commands(struct Scsi_Host *shost, int status)
+{
+	blk_mq_tagset_busy_iter(&shost->tag_set, complete_all_cmds_iter,
+				&status);
+}
+EXPORT_SYMBOL_GPL(scsi_host_complete_all_commands);