add SYNC in function disk_ioctl

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2322 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/dfs/filesystems/elmfat/dfs_elm.c

@@ -780,6 +780,10 @@ DRESULT disk_ioctl(BYTE drv, BYTE ctrl, void *buff)
 		rt_device_control(device, RT_DEVICE_CTRL_BLK_GETGEOME, &geometry);
 
 		*(DWORD *)buff = geometry.block_size/geometry.bytes_per_sector;
+	}
+	else if (ctrl == CTRL_SYNC)
+	{
+		rt_device_control(device, RT_DEVICE_CTRL_BLK_SYNC, RT_NULL);
 	}
 
 	return RES_OK;