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Date: Tue, 7 Apr 2015 10:11:53 +0800
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Subject: Re: [PATCH 1/6] block: export blkdev_reread_part()
From: Ming Lei <ming.lei@canonical.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Andrew Morton <akpm@linux-foundation.org>,
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        Jarod Wilson <jarod@redhat.com>,
        David Herrmann <dh.herrmann@gmail.com>,
        Markus Pargmann <mpa@pengutronix.de>,
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On Mon, Apr 6, 2015 at 10:50 PM, Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, Apr 06, 2015 at 12:40:12AM +0800, Ming Lei wrote:
>> > int blkdev_reread_part(struct block_device *bdev)
>> > {
>> >         if (!mutex_trylock(&bdev->bd_mutex))
>> >                 return -EBUSY;
>> >         blkdev_reread_part_nolock(bdev);
>> >         mutex_unlock(&bdev->bd_mutex);
>> > }
>>
>> Yes, it is more clean, but with extra acquiring lock cost for the
>> failure cases, especially when we replace trylock with mutex_lock().
>
> It's just a few fairly trivial checks, so 'm not really worried about
> it, especially given that blkdev_reread_part isn't called from a fast
> path.

OK, considered that common users don't have any privilege
on block devices at default in most distributions, so they can't
do DoS by running ioctl(RRPART) with this change.

I will change to this style in v1.

Thanks,
Ming Lei