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Date:   Wed, 31 Jul 2019 09:46:44 +0800
From:   Ming Lei <ming.lei@redhat.com>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>, Tejun Heo <tj@kernel.org>,
        Hannes Reinecke <hare@suse.com>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        Alexandru Moise <00moses.alexander00@gmail.com>,
        Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: Re: [PATCH 1/2] block: Verify whether blk_queue_enter() is used when
 necessary
Message-ID: <20190731014643.GA4822@ming.t460p>
References: <20190730181757.248832-1-bvanassche@acm.org>
 <20190730181757.248832-2-bvanassche@acm.org>
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On Tue, Jul 30, 2019 at 11:17:56AM -0700, Bart Van Assche wrote:
> It is required to protect blkg_lookup() calls with a blk_queue_enter() /
> blk_queue_exit() pair. Since it is nontrivial to verify whether this is

Could you explain the reason why the blk_queue_enter()/blk_queue_exit()
pair is required for blkg_lookup()? And comment on blkg_lookup() only
mentioned RCU read lock is needed.

The request queue reference counter is supposed to be held for any
caller of submit_bio(), why isn't that ref count enough?

Thanks,
Ming