Re: [PATCH 13/15] nvmet: Add metadata/T10-PI support

[Max Gurtovoy <maxg@mellanox.com>]

On 1/17/2020 6:46 PM, James Smart wrote:
> On 1/6/2020 5:37 AM, Max Gurtovoy wrote:
>> From: Israel Rukshin <israelr@mellanox.com>
>>
>> Expose the namespace metadata format when PI is enabled. The user needs
>> to enable the capability per subsystem and per port. The other metadata
>> properties are taken from the namespace/bdev.
>>
>> Usage example:
>> echo 1 > /config/nvmet/subsystems/${NAME}/attr_pi_enable
>> echo 1 > /config/nvmet/ports/${PORT_NUM}/param_pi_enable
>>
>>
>
> Mind adding a core routine, callable by a transport, to set the 
> pi_enable attribute on the port ?

I'm not sure what you're asking here.

port->pi_enable is set using configfs before port is active and 
port->pi_capable will be set by each transport before creating the ctrl.

ctrl->pi_support will be set according to port capabilities and 
subsystem subsys->pi_support.

E.g in case you would like to expose subsystem with MD namespaces using 
RDMA port and using FC/TCP port it will work.

The RDMA port ctrl will verify/generate the MD and the FC/TCP port ctrl 
will create a regular bio request that will be passed to the bdev driver 
to handle.

Also these ctrl will identify themselves with the correct capabilities.


>
> Also - I don't know that all block sizes, metadata sizes, and DIF 
> types are supported by the port. Should these registration be 
> "capabilities" lists ?

would it worth complicating the code in this stage for ports that might 
not support all types ?

RDMA ports support all needed bs, metadata sizes and DIF types.

We can add "capabilities" in the future for another transports that PI 
will be implemented for them (if needed).


-Max.


>
> -- james

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