[dm-devel] [PATCH for-next] dm: fix missing bi_remaining accounting

[Mike Snitzer]

On Mon, Nov 04 2013 at 10:25am -0500,
Mikulas Patocka <mpatocka at redhat.com> wrote:

> 
> 
> On Mon, 4 Nov 2013, Mike Snitzer wrote:
> 
> > On Mon, Nov 04 2013 at 10:06am -0500,
> > Mikulas Patocka <mpatocka at redhat.com> wrote:
> > > 
> > > The code uses atomic_inc for restoration of bi_remaining. This patch
> > > changes it to atomic_set(1) to avoid an interlocked instruction. In the
> > > target's bi_endio routine we are sure that bi_remaining is zero
> > > (otherwise, the bi_endio routine wouldn't be called) and there are no
> > > concurrent users of the bio, so we can replace atomic_inc with
> > > atomic_set(1).
> > 
> > This isn't DM-specific.  Shouldn't the other places in the tree that use
> > atomic_inc on bi_remaining should really be converted at the same time?
> 
> There is no 'atomic_inc.*bi_remaining' in other drivers.

Wrong.  I know btrfs has at least one.  As does bcache afaik.