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From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: <axboe@kernel.dk>, <linux-block@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <hch@lst.de>, <hare@suse.de>,
	<ppvk@codeaurora.org>, <bvanassche@acm.org>,
	<kashyap.desai@broadcom.com>
Subject: Re: [RFC PATCH] blk-mq: Clean up references when freeing rqs
Date: Thu, 10 Dec 2020 10:44:54 +0000	[thread overview]
Message-ID: <d8500ca2-1f26-7d28-6baa-237284df0a5c@huawei.com> (raw)
In-Reply-To: <20201210020745.GA1363446@T590>

Hi Ming,

On 10/12/2020 02:07, Ming Lei wrote:
>> Apart from this, my concern is that we come with for a solution, but it's a
>> complicated solution and may not be accepted as this issue is not seen as a
>> problem in practice.
> If that is the case, I'd suggest to consider the solution in the
> following link:
> 
> https://lore.kernel.org/linux-block/20200820180335.3109216-1-ming.lei@redhat.com/
> 
> At least, the idea is simple, which can be extended to support allocate driver tags
> request pool dynamically.

As I see with your approach, we may still iterate a stale request, but 
it just has not been freed, so just no use-after-free BUG, right? Rather 
it is cached until all references dropped. It may be best solution.

So I'll try an experiment today to prove your concern about 
blk_mq_queue_tag_busy_iter(). Then look at possible solution which 
builds on patch in $subject, and compare.

Thanks,
John

  reply	other threads:[~2020-12-10 10:46 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-01 13:02 John Garry
2020-12-02  3:31 ` Ming Lei
2020-12-02 11:18   ` John Garry
2020-12-03  0:55     ` Ming Lei
2020-12-03  9:26       ` John Garry
2020-12-08 11:36         ` John Garry
2020-12-08 17:36           ` John Garry
2020-12-09  1:01           ` Ming Lei
2020-12-09  9:55             ` John Garry
2020-12-10  2:07               ` Ming Lei
2020-12-10 10:44                 ` John Garry [this message]
2020-12-10 12:22                   ` John Garry
2020-12-11  0:21                   ` Ming Lei

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