[SCSI] scsi_scan: Cope with kthread_run failing

If kthread_run failed, we would fail to scan the host, and leak the
allocated async_scan_data.  Since using a separate thread is just an
optimisation, do the scan synchronously if we fail to spawn a thread.
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_scan.c

@@ -1799,6 +1799,7 @@ static int do_scan_async(void *_data)
  **/
 void scsi_scan_host(struct Scsi_Host *shost)
 {
+	struct task_struct *p;
 	struct async_scan_data *data;
 
 	if (strncmp(scsi_scan_type, "none", 4) == 0)
@@ -1810,7 +1811,9 @@ void scsi_scan_host(struct Scsi_Host *shost)
 		return;
 	}
 
-	kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
+	p = kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
+	if (unlikely(IS_ERR(p)))
+		do_scan_async(data);
 }
 EXPORT_SYMBOL(scsi_scan_host);