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From: Christoph Hellwig <hch@infradead.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
	Dave Chinner <dchinner@redhat.com>,
	linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [syzbot] possible deadlock in blkdev_put (2)
Date: Mon, 29 Nov 2021 02:21:05 -0800	[thread overview]
Message-ID: <YaSpkRHgEMXrcn5i@infradead.org> (raw)
In-Reply-To: <20c6dcbd-1b71-eaee-5213-02ded93951fc@i-love.sakura.ne.jp>

On Sun, Nov 28, 2021 at 04:42:35PM +0900, Tetsuo Handa wrote:
> On 2021/11/28 14:32, Tetsuo Handa wrote:
> > If we can unconditionally start __loop_clr_fd() upon ioctl(LOOP_CLR_FD), I think
> > we can avoid circular locking between disk->open_mutex and flush_workqueue().
> 
> Too bad. There is ioctl(LOOP_SET_STATUS) which allows forcing __loop_clr_fd() to be
> called without ioctl(LOOP_CLR_FD). We have to support __loop_clr_fd() upon lo_release().
> 
> Is dropping disk->open_mutex inside lo_release()
> ( https://lkml.kernel.org/r/e4bdc6b1-701d-6cc1-5d42-65564d2aa089@I-love.SAKURA.ne.jp ) possible?

I don't think we can drop open_mutex inside ->release. What is the
problem with offloading the clearing to a different context than the
one that calls ->release?

  reply	other threads:[~2021-11-29 11:05 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-27  7:10 [syzbot] possible deadlock in blkdev_put (2) syzbot
2021-11-27 11:27 ` Tetsuo Handa
2021-11-28  5:32   ` Tetsuo Handa
2021-11-28  7:42     ` Tetsuo Handa
2021-11-29 10:21       ` Christoph Hellwig [this message]
2021-11-29 10:36         ` Tetsuo Handa
2021-11-29 14:13           ` Tetsuo Handa
2021-11-30 12:57           ` Christoph Hellwig
2021-12-01 14:41             ` [PATCH] loop: make autoclear operation asynchronous Tetsuo Handa
2021-12-02  7:22               ` Christoph Hellwig
2021-12-02 11:03                 ` Tetsuo Handa
2021-12-02 12:16               ` Jan Kara
2021-12-02 14:39                 ` Tetsuo Handa
2021-12-02 18:05                   ` Jan Kara
2021-12-03  6:50                     ` Christoph Hellwig
2021-12-03 11:01                       ` Tetsuo Handa
2021-12-08  9:56                         ` Tetsuo Handa
2021-12-08  5:05 ` [syzbot] possible deadlock in blkdev_put (2) syzbot
2021-12-08 11:42 ` syzbot

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