Re: [dm-devel] [PATCH 4/5] block: make blkdev_get/put() handle exclusive access

[Mike Snitzer <snitzer redhat com>]

On Wed, Nov 03 2010 at 12:10pm -0400,
Christoph Hellwig <hch infradead org> wrote:

> On Mon, Nov 01, 2010 at 05:15:28PM +0100, Tejun Heo wrote:
> > * blkdev_get() is extended to include exclusive access management.
> >   @holder argument is added and, if is @FMODE_EXCL specified, it will
> >   gain exclusive access atomically w.r.t. other exclusive accesses.
> > 
> > * blkdev_put() is similarly extended.  It now takes @mode argument and
> >   if @FMODE_EXCL is set, it releases an exclusive access.  Also, when
> >   the last exclusive claim is released, the holder/slave symlinks are
> >   removed automatically.
> 
> Could we get rid of FMODE_EXCL and just make a non-NULL holder field
> mean to open it exlusively (and pass a holder to the blkdev_put to
> release it)?

I agree that the need for a FMODE_EXCL flag is awkward.  Christoph's
proposed change should clean things up nicely.

Other than that, for the DM bits:

Acked-by: Mike Snitzer <snitzer redhat com>