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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	Dongli Zhang <dongli.zhang@oracle.com>,
	John Garry <john.garry@huawei.com>,
	Hannes Reinecke <hare@suse.de>, Daniel Wagner <dwagner@suse.de>
Subject: Re: [PATCH] blk-mq: don't fail driver tag allocation because of inactive hctx
Date: Wed, 3 Jun 2020 20:12:03 +0200	[thread overview]
Message-ID: <20200603181203.GA2032@lst.de> (raw)
In-Reply-To: <20200603133608.GA2149752@T590>

On Wed, Jun 03, 2020 at 09:36:08PM +0800, Ming Lei wrote:
> > +bool __blk_mq_get_driver_tag(struct request *rq)
> > +{
> > +	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
> > +	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
> > +	bool shared = blk_mq_tag_busy(rq->mq_hctx);
> 
> Not necessary to add 'shared' which is just used once.

blk_mq_tag_busy also increments active_queues, and the existing code
does that before various early returns.  To keep the behavior as-is
the call to blk_mq_tag_busy can't be moved around.

> > +	int tag;
> > +
> > +	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
> > +		bt = &rq->mq_hctx->tags->breserved_tags;
> 
> Too many rq->mq_hctx->tags, you can add one local variable to store it.

Really just three of them.  And with a local variable confusing it with
rq->mq_hctx->sched_tags becomes much easier.

      parent reply	other threads:[~2020-06-03 18:12 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-03 10:51 [PATCH] blk-mq: don't fail driver tag allocation because of inactive hctx Ming Lei
2020-06-03 11:53 ` Christoph Hellwig
2020-06-03 13:36   ` Ming Lei
2020-06-03 16:16     ` John Garry
2020-06-04  5:22       ` Dongli Zhang
2020-06-04 10:24         ` John Garry
2020-06-04 11:26           ` Ming Lei
2020-06-04 11:50             ` John Garry
2020-06-04 12:08               ` Ming Lei
2020-06-04 12:45                 ` John Garry
2020-06-04 13:00                   ` Ming Lei
2020-06-04 14:11                     ` John Garry
2020-06-05  0:59                       ` Ming Lei
2020-06-05  7:24                         ` John Garry
2020-06-05  7:31                           ` Ming Lei
2020-06-04 13:28                   ` Ming Lei
2020-06-05  8:33                   ` Ming Lei
2020-06-05  9:27                     ` John Garry
2020-06-05 11:08                       ` John Garry
2020-06-03 18:12     ` Christoph Hellwig [this message]

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