diff options
| -rw-r--r-- | block/blk-mq-sched.c | 64 |
1 files changed, 51 insertions, 13 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index eca81bd4010c..702ce525933c 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -86,12 +86,16 @@ void blk_mq_sched_restart(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. + * + * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to + * be run again. This is necessary to avoid starving flushes. */ -static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) +static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; LIST_HEAD(rq_list); + int ret = 0; do { struct request *rq; @@ -99,6 +103,11 @@ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) if (e->type->ops.has_work && !e->type->ops.has_work(hctx)) break; + if (!list_empty_careful(&hctx->dispatch)) { + ret = -EAGAIN; + break; + } + if (!blk_mq_get_dispatch_budget(hctx)) break; @@ -123,6 +132,8 @@ static void 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 ret; } static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, @@ -140,16 +151,25 @@ static struct blk_mq_ctx *blk_mq_next_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. + * + * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to + * to be run again. This is necessary to avoid starving flushes. */ -static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) +static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; LIST_HEAD(rq_list); struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from); + int ret = 0; do { struct request *rq; + if (!list_empty_careful(&hctx->dispatch)) { + ret = -EAGAIN; + break; + } + if (!sbitmap_any_bit_set(&hctx->ctx_map)) break; @@ -183,21 +203,17 @@ static void 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 ret; } -void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +int __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.dispatch_request; + int ret = 0; LIST_HEAD(rq_list); - /* RCU or SRCU read lock is needed before checking quiesced flag */ - if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) - return; - - hctx->run++; - /* * If we have previous entries on our dispatch list, grab them first for * more fair dispatch. @@ -226,19 +242,41 @@ void 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) - blk_mq_do_dispatch_sched(hctx); + ret = blk_mq_do_dispatch_sched(hctx); else - blk_mq_do_dispatch_ctx(hctx); + ret = blk_mq_do_dispatch_ctx(hctx); } } else if (has_sched_dispatch) { - blk_mq_do_dispatch_sched(hctx); + ret = blk_mq_do_dispatch_sched(hctx); } else if (hctx->dispatch_busy) { /* dequeue request one by one from sw queue if queue is busy */ - blk_mq_do_dispatch_ctx(hctx); + ret = blk_mq_do_dispatch_ctx(hctx); } else { blk_mq_flush_busy_ctxs(hctx, &rq_list); blk_mq_dispatch_rq_list(q, &rq_list, false); } + + return ret; +} + +void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + + /* RCU or SRCU read lock is needed before checking quiesced flag */ + if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) + return; + + hctx->run++; + + /* + * A return of -EAGAIN is an indication that hctx->dispatch is not + * empty and we must run again in order to avoid starving flushes. + */ + if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) { + if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) + blk_mq_run_hw_queue(hctx, true); + } } bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, |