| Message ID | 20171201000848.2656-7-bart.vanassche@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Nov 30, 2017 at 04:08:47PM -0800, Bart Van Assche wrote: > During request dispatch, after a scheduler or per-CPU queue has > been examined, .put_budget() is called if the examined queue is > empty. Since a new request may be queued concurrently with the > .put_budget() call, a request queue needs to be rerun after each > .put_budget() call. If a request is queued concurrently from another path, it can be run from that path, so don't need to rerun in __blk_mq_run_hw_queue(). > > Fixes: commit 1f460b63d4b3 ("blk-mq: don't restart queue when .get_budget returns BLK_STS_RESOURCE") > Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Omar Sandoval <osandov@fb.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Hannes Reinecke <hare@suse.de> > Cc: Johannes Thumshirn <jthumshirn@suse.de> > Cc: <stable@vger.kernel.org> > --- > block/blk-mq-sched.c | 39 ++++++++++++++++++++------------------- > block/blk-mq-sched.h | 2 +- > block/blk-mq.c | 17 ++++++++++++----- > 3 files changed, 33 insertions(+), 25 deletions(-) > > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c > index 398545d94521..3a935081a2d3 100644 > --- a/block/blk-mq-sched.c > +++ b/block/blk-mq-sched.c > @@ -82,12 +82,8 @@ static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx) > return blk_mq_run_hw_queue(hctx, true); > } > > -/* > - * 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) > +/* returns true if hctx needs to be run again */ > +static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) > { > struct request_queue *q = hctx->queue; > struct elevator_queue *e = q->elevator; > @@ -106,7 +102,7 @@ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) > rq = e->type->ops.mq.dispatch_request(hctx); > if (!rq) { > blk_mq_put_dispatch_budget(hctx); > - break; > + return true; > } > > /* > @@ -116,6 +112,8 @@ 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 false; > } > > static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, > @@ -129,16 +127,13 @@ static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, > return hctx->ctxs[idx]; > } > > -/* > - * 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) > +/* returns true if hctx needs to be run again */ > +static bool 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); > + bool ret = false; > > do { > struct request *rq; > @@ -152,6 +147,7 @@ static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) > rq = blk_mq_dequeue_from_ctx(hctx, ctx); > if (!rq) { > blk_mq_put_dispatch_budget(hctx); > + ret = true; > break; > } > > @@ -168,19 +164,22 @@ 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; > } > > /* return true if hw queue need to be run again */ > -void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) > +bool 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; > + return false; > > hctx->run++; > > @@ -212,12 +211,12 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) > if (!list_empty(&rq_list)) { > if (blk_mq_dispatch_rq_list(q, &rq_list, false)) { > if (has_sched_dispatch) > - blk_mq_do_dispatch_sched(hctx); > + run_queue = blk_mq_do_dispatch_sched(hctx); > else > - blk_mq_do_dispatch_ctx(hctx); > + run_queue = blk_mq_do_dispatch_ctx(hctx); > } > } else if (has_sched_dispatch) { > - blk_mq_do_dispatch_sched(hctx); > + run_queue = blk_mq_do_dispatch_sched(hctx); > } else if (q->mq_ops->get_budget) { > /* > * If we need to get budget before queuing request, we > @@ -227,11 +226,13 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) > * TODO: get more budgets, and dequeue more requests in > * one time. > */ > - blk_mq_do_dispatch_ctx(hctx); > + run_queue = 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 run_queue; > } > > 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 ba1d1418a96d..1ccfb8027cfc 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); > > -void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx); > +bool 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 3e0ce940377f..b4225f606737 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1079,7 +1079,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, > { > struct blk_mq_hw_ctx *hctx; > struct request *rq, *nxt; > - bool no_tag = false; > + bool restart = false, no_tag = false; > int errors, queued; > > if (list_empty(list)) > @@ -1105,8 +1105,10 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, > * we'll re-run it below. > */ > if (!blk_mq_mark_tag_wait(&hctx, rq)) { > - if (got_budget) > + if (got_budget) { > blk_mq_put_dispatch_budget(hctx); > + restart = true; > + } > /* > * For non-shared tags, the RESTART check > * will suffice. > @@ -1193,7 +1195,8 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, > * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq > * and dm-rq. > */ > - if (!blk_mq_sched_needs_restart(hctx) || > + if (restart || > + !blk_mq_sched_needs_restart(hctx) || > (no_tag && list_empty_careful(&hctx->dispatch_wait.entry))) > blk_mq_run_hw_queue(hctx, true); > } > @@ -1204,6 +1207,7 @@ 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 > @@ -1220,15 +1224,18 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) > > if (!(hctx->flags & BLK_MQ_F_BLOCKING)) { > rcu_read_lock(); > - blk_mq_sched_dispatch_requests(hctx); > + run_queue = blk_mq_sched_dispatch_requests(hctx); > rcu_read_unlock(); > } else { > might_sleep(); > > srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); > - blk_mq_sched_dispatch_requests(hctx); > + run_queue = blk_mq_sched_dispatch_requests(hctx); > srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); > } > + > + if (run_queue) > + blk_mq_sched_restart(hctx); > } > > /* > -- > 2.15.0 >
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 398545d94521..3a935081a2d3 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -82,12 +82,8 @@ static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx) return blk_mq_run_hw_queue(hctx, true); } -/* - * 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) +/* returns true if hctx needs to be run again */ +static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; @@ -106,7 +102,7 @@ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) rq = e->type->ops.mq.dispatch_request(hctx); if (!rq) { blk_mq_put_dispatch_budget(hctx); - break; + return true; } /* @@ -116,6 +112,8 @@ 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 false; } static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, @@ -129,16 +127,13 @@ static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, return hctx->ctxs[idx]; } -/* - * 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) +/* returns true if hctx needs to be run again */ +static bool 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); + bool ret = false; do { struct request *rq; @@ -152,6 +147,7 @@ static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) rq = blk_mq_dequeue_from_ctx(hctx, ctx); if (!rq) { blk_mq_put_dispatch_budget(hctx); + ret = true; break; } @@ -168,19 +164,22 @@ 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; } /* return true if hw queue need to be run again */ -void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +bool 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; + return false; hctx->run++; @@ -212,12 +211,12 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) if (!list_empty(&rq_list)) { if (blk_mq_dispatch_rq_list(q, &rq_list, false)) { if (has_sched_dispatch) - blk_mq_do_dispatch_sched(hctx); + run_queue = blk_mq_do_dispatch_sched(hctx); else - blk_mq_do_dispatch_ctx(hctx); + run_queue = blk_mq_do_dispatch_ctx(hctx); } } else if (has_sched_dispatch) { - blk_mq_do_dispatch_sched(hctx); + run_queue = blk_mq_do_dispatch_sched(hctx); } else if (q->mq_ops->get_budget) { /* * If we need to get budget before queuing request, we @@ -227,11 +226,13 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) * TODO: get more budgets, and dequeue more requests in * one time. */ - blk_mq_do_dispatch_ctx(hctx); + run_queue = 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 run_queue; } 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 ba1d1418a96d..1ccfb8027cfc 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); -void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx); +bool 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 3e0ce940377f..b4225f606737 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1079,7 +1079,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, { struct blk_mq_hw_ctx *hctx; struct request *rq, *nxt; - bool no_tag = false; + bool restart = false, no_tag = false; int errors, queued; if (list_empty(list)) @@ -1105,8 +1105,10 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, * we'll re-run it below. */ if (!blk_mq_mark_tag_wait(&hctx, rq)) { - if (got_budget) + if (got_budget) { blk_mq_put_dispatch_budget(hctx); + restart = true; + } /* * For non-shared tags, the RESTART check * will suffice. @@ -1193,7 +1195,8 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq * and dm-rq. */ - if (!blk_mq_sched_needs_restart(hctx) || + if (restart || + !blk_mq_sched_needs_restart(hctx) || (no_tag && list_empty_careful(&hctx->dispatch_wait.entry))) blk_mq_run_hw_queue(hctx, true); } @@ -1204,6 +1207,7 @@ 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 @@ -1220,15 +1224,18 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) if (!(hctx->flags & BLK_MQ_F_BLOCKING)) { rcu_read_lock(); - blk_mq_sched_dispatch_requests(hctx); + run_queue = blk_mq_sched_dispatch_requests(hctx); rcu_read_unlock(); } else { might_sleep(); srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); - blk_mq_sched_dispatch_requests(hctx); + run_queue = blk_mq_sched_dispatch_requests(hctx); srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); } + + if (run_queue) + blk_mq_sched_restart(hctx); } /*
During request dispatch, after a scheduler or per-CPU queue has been examined, .put_budget() is called if the examined queue is empty. Since a new request may be queued concurrently with the .put_budget() call, a request queue needs to be rerun after each .put_budget() call. Fixes: commit 1f460b63d4b3 ("blk-mq: don't restart queue when .get_budget returns BLK_STS_RESOURCE") Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Omar Sandoval <osandov@fb.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.de> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: <stable@vger.kernel.org> --- block/blk-mq-sched.c | 39 ++++++++++++++++++++------------------- block/blk-mq-sched.h | 2 +- block/blk-mq.c | 17 ++++++++++++----- 3 files changed, 33 insertions(+), 25 deletions(-)