On Wed, 2017-07-12 at 02:21 +0800, Ming Lei wrote: > Before mq IO scheduler is in, we always send the request to > dispatch list if .queue_rq() return busy. After mq IO scheduler > is introduced, we only do this way when scheduler is used in > case of direct issue. Actually we can do that when scheduler > isn't used too. > > Signed-off-by: Ming Lei <[email protected]> > --- > block/blk-mq.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 041f7b7fa0d6..6e0fc80aa151 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1463,6 +1463,16 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx > *hctx, struct request *rq) > return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true); > } > > +static void blk_mq_direct_dispatch(struct blk_mq_hw_ctx *hctx, > + struct request *rq) > +{ > + spin_lock(&hctx->lock); > + list_add(&rq->queuelist, &hctx->dispatch); > + spin_unlock(&hctx->lock); > + > + blk_mq_run_hw_queue(hctx, false); > +} > + > static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, > struct request *rq, > blk_qc_t *cookie, bool may_sleep) > @@ -1499,15 +1509,17 @@ static void __blk_mq_try_issue_directly(struct > blk_mq_hw_ctx *hctx, > switch (ret) { > case BLK_STS_OK: > *cookie = new_cookie; > - return; > + break; > case BLK_STS_RESOURCE: > __blk_mq_requeue_request(rq); > - goto insert; > + blk_mq_direct_dispatch(hctx, rq); > + break; > default: > *cookie = BLK_QC_T_NONE; > blk_mq_end_request(rq, ret); > - return; > + break; > } > + return; > > insert: > blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
Hello Ming, This patch changes the behavior of blk_mq_try_issue_directly() if a scheduler has been configured and .queue_rq() returns BLK_STS_RESOURCE, namely by skipping the e->type->ops.mq.insert_requests() call. Sorry but I don't think this is what we want. Bart.
