Re: dm: lock bd_mutex when setting device size

["Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>]

Hi Mike,

(10/30/10 06:50), Mike Snitzer wrote:
> Avoid taking md->bdev->bd_inode->i_mutex to update the DM block device's
> size.  Using md->bdev->bd_mutex eliminates the potential for deadlock if
> an fsync is racing with a device resize.
> 
> revalidate_disk() was avoided because it would flush_disk() while the DM
> device is suspended.
> 
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> Cc: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> ---
>  drivers/md/dm.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> Jun'ichi, was the following your implict Acked-by?  Care to make it
> explicit?
> "Anyway, I think your bd_mutex patch should be fine for now and is
> better than the current code with i_mutex, which has a real deadlock
> issue."

No, it was not an ACK.
(This is not multipath. So I think you don't need my ack.)

I'm reluctant to ack this because, as I wrote, it's prone to
cause deadlock in future.
But I couldn't find a real problem with the patch,
so I'm not NACK-ing either.

-- 
Jun'ichi Nomura, NEC Corporation