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Subject: Re: [syzbot] possible deadlock in blkdev_put (2)
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From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To:     Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
        Dave Chinner <dchinner@redhat.com>
Cc:     linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
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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?