Re: [PATCH] blk-mq-sched: don't run the queue async from blk_mq_try_issue_directly()

[Jens Axboe <axboe@kernel.dk>]

On 03/14/2017 11:48 AM, Omar Sandoval wrote:
> On Tue, Mar 14, 2017 at 08:57:50AM -0600, Jens Axboe wrote:
>> If we have scheduling enabled, we jump directly to insert-and-run.
>> That's fine, but we run the queue async and we don't pass in information
>> on whether we can block from this context or not. Fixup both these
>> cases.
> 
> Reviewed-by: Omar Sandoval <osandov@fb.com>
> 
> Just one question: we call blk_mq_get_driver_tag() with wait=false in
> blk_mq_try_issue_directly(). Should we change that to wait=can_block?
> Maybe it's pointless to try a direct issue if we'd have to wait for a
> tag anyways, though.

Exactly, don't want to wait for a tag, at that point we are just
pointlessly stalling an app that could perhaps be submitting more IO.
So I don't think we should factor that in here, better to let the
blocking vs non-blocking drivers behave the same in that regard.

-- 
Jens Axboe