Re: [PATCH V2 1/3] blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter

From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Khazhy Kumykov <khazhy@google.com>,
	Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Hannes Reinecke <hare@suse.de>,
	John Garry <john.garry@huawei.com>,
	David Jeffery <djeffery@redhat.com>
Subject: Re: [PATCH V2 1/3] blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter
Date: Mon, 26 Apr 2021 19:28:18 -0700	[thread overview]
Message-ID: <e0cd9c25-60e1-507d-4fc3-f6ea4ac4ca86@acm.org> (raw)
In-Reply-To: <20210427014540.2747282-2-ming.lei@redhat.com>

On 4/26/21 6:45 PM, Ming Lei wrote:
> + * We grab one request reference before calling @fn and release it after
> + * @fn returns. So far we don't support to pass the request reference to
> + * one new conetxt in @fn.
              ^^^^^^^
              context?

> +void blk_mq_put_rq_ref(struct request *rq)
> +{
> +	if (is_flush_rq(rq, rq->mq_hctx))
> +		rq->end_io(rq, 0);
> +	else if (refcount_dec_and_test(&rq->ref))
> +		__blk_mq_free_request(rq);
> +}

Will rq->end_io() be called twice when a tag iteration function
encounters a flush request?

Thanks,

Bart.