Re: [PATCH v4 12/13] blk-mq: Use shared tags for shared sbitmap support

[John Garry]

On 26/09/2021 04:25, Ming Lei wrote:
> > c
> > @@ -27,10 +27,11 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
> >   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
> >   		struct request_queue *q = hctx->queue;
> >   		struct blk_mq_tag_set *set = q->tag_set;
> > +		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
> The local variable of 'set' can be removed and just retrieve 'tags' from
> hctx->tags.
>
> >   
> >   		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
> >   		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> > -			atomic_inc(&set->active_queues_shared_sbitmap);
> > +			atomic_inc(&tags->active_queues);
> >   	} else {
> >   		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
> >   		    !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> > @@ -61,10 +62,12 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
> >   	struct blk_mq_tag_set *set = q->tag_set;
> >   
> >   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
> > +		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
> > +
> Same with above.

ok

> >   		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
> >   					&q->queue_flags))
> >   			return;
> > -		atomic_dec(&set->active_queues_shared_sbitmap);
> > +		atomic_dec(&tags->active_queues);
> >   	} else {
> >   		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> >   			return;
> > @@ -510,38 +513,10 @@ static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
> >   	return 0;
> >   }

...

> > -	struct sbitmap_queue	__bitmap_tags;
> > -	struct sbitmap_queue	__breserved_tags;
> >   	struct blk_mq_tags	**tags;
> >   
> > +	struct blk_mq_tags	*shared_sbitmap_tags;
> > +
> >   	struct mutex		tag_list_lock;
> >   	struct list_head	tag_list;
> >   };
> > @@ -432,6 +429,8 @@ enum {
> >   	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
> >   		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
> >   
> > +#define BLK_MQ_NO_HCTX_IDX	(-1U)
> > +
> >   struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
> >   		struct lock_class_key *lkclass);
> >   #define blk_mq_alloc_disk(set, queuedata)				\
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index 4baf9435232d..17e50e5ef47b 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -459,8 +459,7 @@ struct request_queue {
> >   
> >   	atomic_t		nr_active_requests_shared_sbitmap;
> >   
> > -	struct sbitmap_queue	sched_bitmap_tags;
> > -	struct sbitmap_queue	sched_breserved_tags;
> > +	struct blk_mq_tags	*shared_sbitmap_tags;
> Maybe better with shared_sched_sbitmap_tags or sched_sbitmap_tags?

Yeah, I suppose I should add "sched" to the name, as before.

BTW, Do you think that I should just change shared_sbitmap -> 
shared_tags naming now globally? I'm thinking now that I should...

Thanks,
John