XtraBackup test xb_export.sh now has a workaround for this bug:
# Tablespace import is asynchronous, so shutdown the server to have
# consistent backup results. Otherwise we risk ending up with no test.ibd
# in the backup in case importing has not finished before taking backup
XtraBackup test xb_export.sh now has a workaround for this bug:
# Tablespace import is asynchronous, so shutdown the server to have
# consistent backup results. Otherwise we risk ending up with no test.ibd
# in the backup in case importing has not finished before taking backup
shutdown_server
start_server $mysql_extra_args
Once this bug is fixed, it should be removed.