Re: [PATCH] blk-mq: test QUEUE_FLAG_HCTX_ACTIVE for sbitmap_shared in hctx_may_queue

[Ming Lei <ming.lei@redhat.com>]

On Mon, Jan 04, 2021 at 10:41:36AM +0000, John Garry wrote:
> On 27/12/2020 11:34, Ming Lei wrote:
> > In case of blk_mq_is_sbitmap_shared(), we should test QUEUE_FLAG_HCTX_ACTIVE against
> > q->queue_flags instead of BLK_MQ_S_TAG_ACTIVE.
> > 
> > So fix it.
> > 
> > Cc: John Garry <john.garry@huawei.com>
> > Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> > Fixes: f1b49fdc1c64 ("blk-mq: Record active_queues_shared_sbitmap per tag_set for when using shared sbitmap")
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> 
> Reviewed-by: John Garry <john.garry@huawei.com>
> 
> > ---
> >   block/blk-mq.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/block/blk-mq.h b/block/blk-mq.h
> > index c1458d9502f1..3616453ca28c 100644
> > --- a/block/blk-mq.h
> > +++ b/block/blk-mq.h
> > @@ -304,7 +304,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
> >   		struct request_queue *q = hctx->queue;
> >   		struct blk_mq_tag_set *set = q->tag_set;
> > -		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &q->queue_flags))
> > +		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> 
> I wonder how this ever worked properly, as BLK_MQ_S_TAG_ACTIVE is bit index
> 1, and for q->queue_flags that means QUEUE_FLAG_DYING bit, which I figure is
> not set normally..

It always return true, and might just take a bit more CPU especially the tag queue
depth of magsas_raid and hisi_sas_v3 is quite high.

Thanks,
Ming