From: Ming Lei ming.lei@redhat.com
commit 1f460b63d4b37f504d8d0affc2cd492eb005ea97 upstream
SCSI restarts its queue in scsi_end_request() automatically, so we don't need to handle this case in blk-mq.
Especailly any request won't be dequeued in this case, we needn't to worry about IO hang caused by restart vs. dispatch.
Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Jack Wang jinpu.wang@profitbricks.com --- block/blk-mq-sched.c | 45 ++++++++++++++++++++------------------------- block/blk-mq-sched.h | 2 +- block/blk-mq.c | 8 ++------ 3 files changed, 23 insertions(+), 32 deletions(-)
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index daab27feb653..7775f6b12fa9 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -81,8 +81,12 @@ void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) } }
-/* return true if hctx need to run again */ -static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE. + */ +static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; @@ -98,7 +102,7 @@ static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
ret = blk_mq_get_dispatch_budget(hctx); if (ret == BLK_STS_RESOURCE) - return true; + break;
rq = e->type->ops.mq.dispatch_request(hctx); if (!rq) { @@ -116,8 +120,6 @@ static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) */ list_add(&rq->queuelist, &rq_list); } while (blk_mq_dispatch_rq_list(q, &rq_list, true)); - - return false; }
static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, @@ -131,8 +133,12 @@ static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, return hctx->ctxs[idx]; }
-/* return true if hctx need to run again */ -static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE. + */ +static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; LIST_HEAD(rq_list); @@ -147,7 +153,7 @@ static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
ret = blk_mq_get_dispatch_budget(hctx); if (ret == BLK_STS_RESOURCE) - return true; + break;
rq = blk_mq_dequeue_from_ctx(hctx, ctx); if (!rq) { @@ -171,22 +177,19 @@ static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) } while (blk_mq_dispatch_rq_list(q, &rq_list, true));
WRITE_ONCE(hctx->dispatch_from, ctx); - - return false; }
/* return true if hw queue need to be run again */ -bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request; LIST_HEAD(rq_list); - bool run_queue = false;
/* RCU or SRCU read lock is needed before checking quiesced flag */ if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) - return false; + return;
hctx->run++;
@@ -218,12 +221,12 @@ bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) blk_mq_sched_mark_restart_hctx(hctx); if (blk_mq_dispatch_rq_list(q, &rq_list, false)) { if (has_sched_dispatch) - run_queue = blk_mq_do_dispatch_sched(hctx); + blk_mq_do_dispatch_sched(hctx); else - run_queue = blk_mq_do_dispatch_ctx(hctx); + blk_mq_do_dispatch_ctx(hctx); } } else if (has_sched_dispatch) { - run_queue = blk_mq_do_dispatch_sched(hctx); + blk_mq_do_dispatch_sched(hctx); } else if (q->mq_ops->get_budget) { /* * If we need to get budget before queuing request, we @@ -233,19 +236,11 @@ bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) * TODO: get more budgets, and dequeue more requests in * one time. */ - run_queue = blk_mq_do_dispatch_ctx(hctx); + blk_mq_do_dispatch_ctx(hctx); } else { blk_mq_flush_busy_ctxs(hctx, &rq_list); blk_mq_dispatch_rq_list(q, &rq_list, false); } - - if (run_queue && !blk_mq_sched_needs_restart(hctx) && - !test_bit(BLK_MQ_S_TAG_WAITING, &hctx->state)) { - blk_mq_sched_mark_restart_hctx(hctx); - return true; - } - - return false; }
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h index 1ccfb8027cfc..ba1d1418a96d 100644 --- a/block/blk-mq-sched.h +++ b/block/blk-mq-sched.h @@ -23,7 +23,7 @@ void blk_mq_sched_insert_requests(struct request_queue *q, struct blk_mq_ctx *ctx, struct list_head *list, bool run_queue_async);
-bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx); +void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);
int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e); void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e); diff --git a/block/blk-mq.c b/block/blk-mq.c index 3bc6de8b82c0..b9dac21f35f6 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1215,7 +1215,6 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) { int srcu_idx; - bool run_queue;
/* * We should be running this queue from one of the CPUs that @@ -1250,18 +1249,15 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
if (!(hctx->flags & BLK_MQ_F_BLOCKING)) { rcu_read_lock(); - run_queue = blk_mq_sched_dispatch_requests(hctx); + blk_mq_sched_dispatch_requests(hctx); rcu_read_unlock(); } else { might_sleep();
srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); - run_queue = blk_mq_sched_dispatch_requests(hctx); + blk_mq_sched_dispatch_requests(hctx); srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); } - - if (run_queue) - blk_mq_run_hw_queue(hctx, true); }
/*