Re: [PATCH 1/4] block: centrelize PI remapping logic to the block layer

[Christoph Hellwig <hch@lst.de>]

On Wed, Sep 04, 2019 at 11:32:04AM +0300, Max Gurtovoy wrote:
>
> On 9/4/2019 8:49 AM, Christoph Hellwig wrote:
>> On Tue, Sep 03, 2019 at 01:21:59PM -0600, Jens Axboe wrote:
>>> On 9/3/19 1:11 PM, Sagi Grimberg wrote:
>>>>> +	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ &&
>>>>> +	    error == BLK_STS_OK)
>>>>> +		t10_pi_complete(req,
>>>>> +				nr_bytes / queue_logical_block_size(req->q));
>>>>> +
>>>> div in this path? better to use  >> ilog2(block_size).
>>>>
>>>> Also, would be better to have a wrapper in place like:
>>>>
>>>> static inline unsigned short blk_integrity_interval(struct request *rq)
>>>> {
>>>> 	return queue_logical_block_size(rq->q);
>>>> }
>>> If it's a hot path thing that matters, I'd strongly suggest to add
>>> a queue block size shift instead.
>> Make that a protection_interval_shift, please.  While that currently
>> is the same as the logical block size the concepts are a little
>> different, and that makes it clear.  Except for that this patch looks
>> very nice to me, it is great to avoid having drivers to deal with the
>> PI remapping.
>
> Christoph,
>
> I was thinking about the following addition to the code (combination of all 
> the suggestions):

I'll defer to Martin, but I think we still need the integrity_interval
naming in some form.

static inline unsigned short queue_logical_block_shift(struct  request_queue *q)
> +{
> +       unsigned short retval = 9;
> +
> +       if (q && q->limits.logical_block_shift)
> +               retval = q->limits.logical_block_shift;
> +
> +       return retval;

I don't think a NULL queue makes any sense here.  And I'd rather
ensure the field is always set rather than adding a conditional here.

And btw, centrelize in the Subject should be centralize.