Re: [PATCH v3 2/2] block: use blk_mq_plug() wrapper consistently in the block layer

[Pankaj Raghav <p.raghav@samsung.com>]

>> Either of the changes should not have led to a bug in zoned devices:
>>
>> - blk_execute_rq_nowait:
>>   Only passthrough requests can use this function, and plugging can be
>>   performed on those requests in zoned devices. So no issues directly
>>   accessing the plug.
>>
>> - blk_flush_plug in bio_poll:
>>   As we don't plug the requests that require a zone lock in the first
>>   place, flushing should not have any impact. So no issues directly
>>   accessing the plug.
>>
>> This is just a cleanup patch to use this wrapper to get the plug
>> consistently across the block layer.
> 
> While I did suggest to make this consistent and in principle it's
> the right thing to do, it also irks me to add extra checks to paths
> where we know that it's just extra pointless code. Maybe we can
> just comment these two spots? Basically each of the sections above
> could just go into the appropriate file.
> 
The checks should go away, and the plug could be inlined by the compiler if
we don't have CONFIG_BLK_DEV_ZONED. Otherwise, I do agree with you that it
is a pointless check.

I am fine with either, though I prefer what this patch is doing. So if you
feel strongly against calling the blk_mq_plug function, I can turn this
patch into just adding comments as you suggested.