Re: [PATCH] iscsi_iser: Re-enable 'iser_pi_guard' module parameter

Sagi Grimberg
2018-01-14T09:34:20Z

Hi Steven and Hannes,

>> On Wed, Jan 10, 2018 at 10:07:36AM +0100, Hannes Reinecke wrote:
>>> The module parameter 'iser_pi_guard' has been disabled by commit
>>> 5bb6e543d2a7d58 ("IB/iser: DIX update"), but the functionality
>>> to select the guard algorithm is still required.
>>
>> Commit should explain why it is still required? What is the actual bug here?
>>
>> Someone who understands this is going to have to Ack it for it to go
>> through the rdma tree..
>>
> Without the module parameter, there is no way to actually use the CRC guard format.
> Currently, iscsi_iser_session_create() indicates support for both IP and CRC formats, but
> sd_dif_config_host() always checks for IP support first, so CRC guard won't be used.

Isn't a bit backwards that each individual driver needs this knob to
modify the block layer behavior? I think a better approach would be to
get rid of the drivers modparams and simply add a block sysfs knob that
would take the knob guard if supported...

Thoughts?

CCing Martin...