* Vladislav Bolkhovitin (vst@xxxxxxxx) wrote: > Robert Jennings wrote: > >>>>What I meant that is that the kernel tgt code (scsi_tgt*) receives > >>>>SCSI commands from one lld and send them to another lld instead of > >>>>sending them to user space. > >>> > >>>Although the approach of passing SCSI commands from a target LLD to an > >>>initiator one without any significant interventions from the target > >>>software looks to be nice and simple, you should realize how limited, > >>>unsafe and illegal it is, since it badly violates SCSI specs. > >> > >>I think that 'implemented cleanly' means that one scsi_host is assigned > >>to only one initiator. > > > >Vladislav listed a number of issues that are inherent in an implementation > >that does not have a 1:1 relationship of initiators to targets. The vscsi > >architecture defines the 1:1 relationship; it's imposible to have more > >than one initiator per target. > > Just few small notes: > > 1. As I already wrote, complete 1:1 relationship isn't practically > possible, because there is always a local access on the target (i.e. one > more initiator) and you can't disable it on practice. I was proposing a 1:1 relationship of initiator to target within the target framework for in-kernel pass-through. We would still have the case that local access on the target is possible; an administrator with privileges neccessary to create a target would have the responsibility to not then access the device locally. This is no different than if I create my root file system on /dev/sda1, I should not also 'dd' data to /dev/sda1 while the system is running. It's a bad idea, but nothing stops me; however this is something that only a root level user can do. This would be the same, these targets in pass-through have permissions by default that do not allow local access by non-root users. > 2. 1:1 relationship is a serious limitation for usage cases like an SPI > tape library serving backup for several servers on an FC net. Restricting the relationship to 1:1 would be for pass-through devices only, this would not necessarily dictate other target types which could be used for such cases. --Rob - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
