Re: [PATCH] block: Submit flush requests to the I/O scheduler

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 2022/08/12 23:41, Christoph Hellwig wrote:
> On Fri, Aug 12, 2022 at 02:03:55PM -0700, Bart Van Assche wrote:
>> When submitting a REQ_OP_WRITE | REQ_FUA request to a zoned storage
>> device, these requests must be passed to the (mq-deadline) I/O scheduler
>> to ensure that these happen at the write pointer.
> 
> Yes.
> 
> But maybe I'm stupid, but how is the patch related to fixing that?
> blk_mq_plug_issue_direct is called from blk_mq_flush_plug_list for
> only the !has_elevator case.  How does that change a thing?

And writes to zoned drives never get plugged in the first place, scheduler
present or not.

> 
> Also please include a description of why these changes are otherwise
> good and won't regress other cases.
> 
>> +		blk_mq_sched_insert_request(rq, /*at_head=*/false,
>> +			/*run_queue=*/last, /*async=*/false);
> 
> I find thise comment style very hard to read.  Yes, maybe the three
> bools here should become flags, but this is even worse than just
> passing the arguments.


-- 
Damien Le Moal
Western Digital Research