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blk-mq: don't restart queue when .get_budget returns BLK_STS_RESOURCE 

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>
This commit is contained in:
Ming Lei 2017-10-27 12:43:30 +08:00 committed by Jens Axboe
parent 358a3a6bcc
commit 1f460b63d4
3 changed files with 23 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
block/blk-mq-sched.c
View File

@ -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,

2
block/blk-mq-sched.h
View File

@ -22,7 +22,7 @@ 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);

8
block/blk-mq.c
View File

@ -1226,7 +1226,6 @@ 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
@ -1243,18 +1242,15 @@ 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);
}
/*