[PATCH] NVMe: Metadata and PI format support

[keith.busch@intel.com (Keith Busch)]

On Tue, 17 Feb 2015, Sam Bradshaw wrote:
>>> If there is interest in incorporating this support, we can provide
>>> a patch on top of this that enables 16b/32b/64b metadata with PI and
>>> supports PIL={0,1}
>>
>> I would also like that to work. I was hoping to reuse the
>> t10_pi_generate/verify functions for this. Those can work if the
>> iter->prot_buf is incremented by the blk_intergity's tuple_size rather
>> than just the 8-byte PI field.
>>
>> That'd work with PIL=0, not sure what to do with PIL=1. Maybe we should
>> just define our own functions for nvme even though they'd mostly be the
>> same as the ones scsi uses.
>
> We were unable to come up with an elegant solution that reused the
> t10_pi_generate/verify functions while also handling the PIL=1 case.
> So we defined our own functions.

I see you support 16/32/64 exclusively. As unlikely it may be someone
would implement something other than those, the specification allows 64k
different metadata formats with as many more combinations for PIL. Could
the solution be generalized to accomodate arbitrary formats in a single
function rather than require a definition for each possible combination?