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SubjectRe: [PATCH 2/8] blk-mq: change the method of iterating busy tags of a request_queue
On Sat, Mar 16, 2019 at 11:50:27PM -0700, Ming Lei wrote:
> On Sat, Mar 16, 2019 at 12:15 AM Keith Busch <kbusch@kernel.org> wrote:
> > On Fri, Mar 15, 2019 at 01:57:38AM -0700, Jianchao Wang wrote:
> > > + if (rq && rq->q == hctx->queue &&
> > > + rq->mq_hctx == hctx &&
> > > + (!iter_data->inflight ||
> > > + blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT))
> > > + return iter_data->fn(rq, iter_data->data, reserved);
> >
> > There is still a window where the check may succeed, but the request is
> > being assigned to a completely different request_queue. The callback
> > then operates on a request it doesn't own.
>
> The situation above is only related with 'none' io scheduler.
>
> However, this patch doesn't change behavior for none given .rq[tag] is same with
> .static_rq[tag], so I guess your concern may not be related with this patch.

Right, it's not new, but queue iteration wasn't exported for drivers
before this.

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