>>> * Host per session or host per IB device: I agree with Or about the >>> need to have a host per session. I understand that the main >>> problem that commit 7e8e8af6511afafff33ef7eb0f519bf8702b78ed tries >>> to solve is what happens if we failover from one IB device to >>> another, right? We prefer to continue using a host per session, >>> >> It is not related to this. >> >> It deals with being able to set some limits at a level higher than per >> session. If we had X sessions on one HCA port then we do not want to >> always to push X * session->can_queue IOs onto the port because the port >> may not be able to take that much IO. The commands will time out and the >> sessions will be stopped, and the scsi eh will run. The problem we face >> is that the ib_device is per HCA and not per port like we would see with >> normal scsi pci drivers or iscsi network drivers. >> >> It deals with aligning data structures to objects that can be removed >> and handling refcounting in a common way, and aligning this with how we >> normally do it in the scsi layer. With a normal scsi hba and driver, we >> have a pci device and allocate a scsi host for it (we actually get a pci >> resource for each port on the hba and allocate a scsi_host per port). We >> implement the pci driver's remove and probe callouts which get called at >> those times. >> >> Unlike software iscsi for infinniband we have something close to this. >> We have the ib_client which makes allocating a host per ib_device really >> nice when having to handle resource limits and handling removal of the >> host object and the objects accessing it and doing it in a standard way. >> For example if I remove a broadcom card I will remove the iscsi/scsi >> host for each port and that will cause each session running on that card >> to be removed. For iser if I do a host per ib_device and you did >> something like rmmod the HCA's module then each devices's remove callout >> gets called. We can then remove the iscsi/scsi host for the ib_device >> and the iscsi layer will remove the sessions referencing it. And it is >> all a common code path and there is no special casing for different >> drivers of this class, and the driver does not need to maintain its own >> struct to represent what other driver's represent with the scsi_host. >> >> > > Oh yeah, I am not sure if you saw the end of that thread about this > item, but I had said I was ok with leaving it as is for now. Because we > allocate a ib_device per HCA, we run into problems with doing a > scsi_host per ib_device (when I did the patch I thought we were getting > a device per port). I am not going to push that patch because of this, > so we do not have to waste any time on this issue. At this time if you > are not complaining then I am not either :) > Yeah, I saw that you said that we have several options. Let's not change it for now.
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