[SCSI] queue async scan work to an async_schedule domain

This is preparation to enable async_synchronize_full() to be used as a
replacement for scsi_complete_async_scans(), i.e. to stop leaking scsi
internal details where they are not needed.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Tested-by: NEldad Zack <eldad@fogrefinery.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

drivers/scsi/scsi_scan.c

@@ -1845,14 +1845,13 @@ static void do_scsi_scan_host(struct Scsi_Host *shost)
 	}
 }
 
-static int do_scan_async(void *_data)
+static void do_scan_async(void *_data, async_cookie_t c)
 {
 	struct async_scan_data *data = _data;
 	struct Scsi_Host *shost = data->shost;
 
 	do_scsi_scan_host(shost);
 	scsi_finish_async_scan(data);
-	return 0;
 }
 
 /**
@@ -1861,7 +1860,6 @@ 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)
@@ -1876,9 +1874,11 @@ void scsi_scan_host(struct Scsi_Host *shost)
 		return;
 	}
 
-	p = kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
-	if (IS_ERR(p))
-		do_scan_async(data);
+	/* register with the async subsystem so wait_for_device_probe()
+	 * will flush this work
+	 */
+	async_schedule(do_scan_async, data);
+
 	/* scsi_autopm_put_host(shost) is called in scsi_finish_async_scan() */
 }
 EXPORT_SYMBOL(scsi_scan_host);