scsi: serialize ->rescan against ->remove

Lock the device embedded in the scsi_device to protect against
concurrent calls to ->remove.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/scsi_scan.c

@@ -1570,16 +1570,15 @@ EXPORT_SYMBOL(scsi_add_device);
 
 void scsi_rescan_device(struct device *dev)
 {
-	if (!dev->driver)
-		return;
-
-	if (try_module_get(dev->driver->owner)) {
+	device_lock(dev);
+	if (dev->driver && try_module_get(dev->driver->owner)) {
 		struct scsi_driver *drv = to_scsi_driver(dev->driver);
 
 		if (drv->rescan)
 			drv->rescan(dev);
 		module_put(dev->driver->owner);
 	}
+	device_unlock(dev);
 }
 EXPORT_SYMBOL(scsi_rescan_device);