[PATCH v4 01/18] block: Add PR callouts for read keys and reservation

[Chaitanya Kulkarni]

On 2/24/2023 9:44 AM, Mike Christie wrote:
> Add callouts for reading keys and reservations. This allows LIO to support
> the READ_KEYS and READ_RESERVATION commands and will allow dm-multipath
> to optimize it's error handling so it can check if it's getting an error
> because there's an existing reservation or if we need to retry different
> paths.
> 
> Note: This only initially adds the struct definitions in the kernel as I'm
> not sure if we wanted to export the interface to userspace yet. read_keys
> and read_reservation are exactly what dm-multipath and LIO need, but for a
> userspace interface we may want something like SCSI's READ_FULL_STATUS and
> NVMe's report reservation commands. Those are overkill for dm/LIO and
> READ_FULL_STATUS is sometimes broken for SCSI devices.
> 
> Signed-off-by: Mike Christie <michael.christie at oracle.com>
> ---

Looks good.

Reviewed-by: Chaitanya Kulkarni <kch at nvidia.com>

-ck