Description of problem:

If tcmu-runner is not running and a initiator sends a command, the command will be stuck until you reboot the box. The stuck command will force the initiator's error handler to run, the LUN to be offlined and in windows/linux the session will be dropped and future logins will fail.

Normally, the user should not be starting/stopping tcmu-runner manually. Components like rtslib and rbd-target-gw/ceph-iscsi-config and systemd will handle this.

However, users will sometimes start/stop services as part of their debugging, so this is a request to add a warning in the release notes or main doc like here

https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/3/html/block_device_guide/using_an_iscsi_gateway

or wherever something like this should go.


The warning should be something like:

tcmu-runner must not be stopped while iSCSI initiators are logged into the target. Before stopping tcmu-runner, the rbd-target-gw service must be stopped cleanly, or the iSCSI initiators must be logged out. If this is not done, SCSI commands may get stuck in the target layer and the system will have to be rebooted.



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A kernel fix is required and that will be added to 7.6. A bz for that is here

https://bugzilla.redhat.com/show_bug.cgi?id=1562587