Re: [Nbd] [PATCH 1/6] block: export blkdev_reread_part()

[Ming Lei <ming.lei@...1301...>]

On Mon, Apr 6, 2015 at 10:50 PM, Christoph Hellwig <hch@...1270...> 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