On Tue, Jun 02, 2020 at 09:25:01AM +0000, Damien Le Moal wrote:
> On 2020/06/02 18:15, Ming Lei wrote:
> > All requests in the 'list' of blk_mq_dispatch_rq_list belong to same
> > hctx, so it is better to pass hctx instead of request queue, because
> > blk-mq's dispatch target is hctx instead of request queue.
> >
> > Cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
> > Cc: Baolin Wang <baolin.wang7@xxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> > Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
> > Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> > Tested-by: Baolin Wang <baolin.wang7@xxxxxxxxx>
> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> > ---
> > block/blk-mq-sched.c | 14 ++++++--------
> > block/blk-mq.c | 6 +++---
> > block/blk-mq.h | 2 +-
> > 3 files changed, 10 insertions(+), 12 deletions(-)
> >
> > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> > index a31e281e9d31..632c6f8b63f7 100644
> > --- a/block/blk-mq-sched.c
> > +++ b/block/blk-mq-sched.c
> > @@ -96,10 +96,9 @@ static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
> > struct elevator_queue *e = q->elevator;
> > LIST_HEAD(rq_list);
> > int ret = 0;
> > + struct request *rq;
> >
> > do {
> > - struct request *rq;
> > -
> > if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
> > break;
> >
> > @@ -131,7 +130,7 @@ static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
> > * in blk_mq_dispatch_rq_list().
> > */
> > list_add(&rq->queuelist, &rq_list);
> > - } while (blk_mq_dispatch_rq_list(q, &rq_list, true));
> > + } while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, true));
>
> Why not use the hctx argument passed to the function instead of rq->mq_hctx ?
e->type->ops.dispatch_request(hctx) may return one request which's
.mq_hctx isn't same with the 'hctx' argument, so far bfq and deadline
may do that.
Thanks,
Ming
