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Date:   Fri, 30 Nov 2018 01:52:09 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Dennis Zhou <dennis@kernel.org>
Cc:     Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Josef Bacik <josef@toxicpanda.com>, kernel-team@fb.com,
        linux-block@vger.kernel.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 04/13] blkcg: introduce common blkg association logic
Message-ID: <20181130095209.GA17103@infradead.org>
References: <20181126211946.77067-1-dennis@kernel.org>
 <20181126211946.77067-5-dennis@kernel.org>
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>  EXPORT_SYMBOL_GPL(bio_associate_blkcg);
>  
>  /**
> - * bio_associate_blkg - associate a bio with the a blkg
> + * bio_has_queue - required check for blkg association
> + * @bio: target bio
> + *
> + * A blkg represents the relationship between a blkcg and a request_queue.
> + * If there is no request_queue, there is no blkg and therefore nothing to
> + * associate with.
> + */
> +static inline bool bio_has_queue(struct bio *bio)
> +{
> +	return bio->bi_disk && bio->bi_disk->queue;
> +}

How do you ever see a bio without a queue?  We can't even do I/O in
that case.