After the update, the master server (first to be updated, of course) can no longer attach the xostor SR.
I have verified that the rolling pool update did look for updated packages, and that xostor is still installed and working (thankfully the linstor services are working fine, so there's no risk of data loss here).
When trying to mount the SR, the master host gets this error:
[19:02 goethite ~]# xe pbd-plug uuid=91e19949-cf2c-b1bb-7dda-d2c114c113a1
Error code: SR_BACKEND_FAILURE_46
Error parameters: , The VDI is not available [opterr=Could not load 5cb360ea-0904-472c-a3f9-1a44b97936c3 because: ['UNKNOWN_XENAPI_PLUGIN_FUNCTION', 'getInfo'] (openers: {'hematite.earth.gkhs.net': {'26922': {'process-name': '+tapdisk', 'open-duration': '612038496'}}, 'goethite.earth.gkhs.net': {}, 'siderite.earth.gkhs.net': {}})],
I would advise nobody updates a host using XOSTOR until this gets fixed!