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blk-mq-sched: bypass the scheduler for flushes entirely 

There's a weird inconsistency that flushes are mostly hidden from the
scheduler, but it needs to be aware of them in ->insert_requests().
Instead of having every scheduler call blk_mq_sched_bypass_insert(),
let's do it in the common framework.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Omar Sandoval 2017-02-02 15:42:39 -08:00 committed by Jens Axboe
parent e17354961b
commit 0cacba6cf8
3 changed files with 23 additions and 6 deletions
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25
block/blk-mq-sched.c
View File

@ -289,7 +289,8 @@ void blk_mq_sched_request_inserted(struct request *rq)
}
EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
struct request *rq)
{
if (rq->tag == -1) {
rq->rq_flags |= RQF_SORTED;
@ -305,7 +306,6 @@ bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
spin_unlock(&hctx->lock);
return true;
}
EXPORT_SYMBOL_GPL(blk_mq_sched_bypass_insert);
static void blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
{
@ -363,6 +363,9 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head,
return;
}
if (e && blk_mq_sched_bypass_insert(hctx, rq))
goto run;
if (e && e->type->ops.mq.insert_requests) {
LIST_HEAD(list);
@ -374,6 +377,7 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head,
spin_unlock(&ctx->lock);
}
run:
if (run_queue)
blk_mq_run_hw_queue(hctx, async);
}
@ -385,6 +389,23 @@ void blk_mq_sched_insert_requests(struct request_queue *q,
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
struct elevator_queue *e = hctx->queue->elevator;
if (e) {
struct request *rq, *next;
/*
* We bypass requests that already have a driver tag assigned,
* which should only be flushes. Flushes are only ever inserted
* as single requests, so we shouldn't ever hit the
* WARN_ON_ONCE() below (but let's handle it just in case).
*/
list_for_each_entry_safe(rq, next, list, queuelist) {
if (WARN_ON_ONCE(rq->tag != -1)) {
list_del_init(&rq->queuelist);
blk_mq_sched_bypass_insert(hctx, rq);
}
}
}
if (e && e->type->ops.mq.insert_requests)
e->type->ops.mq.insert_requests(hctx, list, false);
else

1
block/blk-mq-sched.h
View File

@ -15,7 +15,6 @@ struct request *blk_mq_sched_get_request(struct request_queue *q, struct bio *bi
void blk_mq_sched_put_request(struct request *rq);
void blk_mq_sched_request_inserted(struct request *rq);
bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq);
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio);
bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio);
bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq);

3
block/mq-deadline.c
View File

@ -395,9 +395,6 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_mq_sched_request_inserted(rq);
if (blk_mq_sched_bypass_insert(hctx, rq))
return;
if (at_head || blk_rq_is_passthrough(rq)) {
if (at_head)
list_add(&rq->queuelist, &dd->dispatch);