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From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
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
Date: Wed, 31 Jul 2019 11:26:08 -0700	[thread overview]
Message-ID: <d24cba3d-1ba3-22bf-1223-e25264ca4084@acm.org> (raw)
In-Reply-To: <20190731014643.GA4822@ming.t460p>

On 7/30/19 6:46 PM, Ming Lei wrote:
> 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?

This patch was added to my own tree before commit
47cdee29ef9d ("block: move blk_exit_queue into __blk_release_queue") 
went upstream. Since blk_exit_queue() has been moved from 
blk_cleanup_queue() into __blk_release_queue() I don' think that we 
need this patch series. I will drop these two patches.

Bart.

  reply	other threads:[~2019-07-31 18:26 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-30 18:17 [PATCH 0/2] Fix a race condition triggered by submit_bio() Bart Van Assche
2019-07-30 18:17 ` [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary Bart Van Assche
2019-07-31  1:46   ` Ming Lei
2019-07-31 18:26     ` Bart Van Assche [this message]
2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche
2019-07-30 18:18   ` syzbot
2019-07-31  1:53   ` Ming Lei
2019-07-31  1:53     ` syzbot

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