[PATCH v3 09/10] nvme: add handling for app_tag

[Martin K. Petersen]

Kanchan,

>> This assumes the app tag is the same for every block in the I/O?
>> That's not how it's typically used (to the extent that it is used at
>> all due to the value 0xffff acting as escape).
>> 
>
> NVMe spec allows only one value to be passed in each read/write
> command (LBAT for write, and ELBAT for read). And that's what
> controller checks for the entire block range covered by one command.
> So per-io tag rather than per-block tag. The integrity buffer creator
> is supposed to put the same application-tag for each block if it is
> sending multi-block IO.

I am OK with that approach as long as the mask is only applied when
checking is enabled.

I.e. I don't have a use case for checking less than the full app tag.
But almost all users of PI I am aware of depend on being able to put
different values in the app tag for different blocks in the I/O when
checking is disabled.

-- 
Martin K. Petersen	Oracle Linux Engineering