Re: [PATCH 3/8] md: raid5: use refcount_t for reference counting instead atomic_t

[Sebastian Andrzej Siewior]

On 2018-05-23 14:36:15 [+0200], Peter Zijlstra wrote:
> > Most changes are 1:1 replacements except for
> >     BUG_ON(atomic_inc_return(&sh->count) != 1);
> 
> That doesn't look right, 'inc_return == 1' implies inc-from-zero, which
> is not allowed by refcount.
> 
> > which has been turned into
> >         refcount_inc(&sh->count);
> >         BUG_ON(refcount_read(&sh->count) != 1);
> 
> And that is racy, you can have additional increments in between.

so do we stay with the atomic* API here or do we extend refcount* API?

Sebastian