Re: [PATCH] lightnvm: pblk: avoid ref warning on cache creation

[Matias BjÃrling]

On 11/23/2018 11:04 AM, Hans Holmberg wrote:
> Great catch Javier! Nice refactoring work too.
>
> Reviewed-by: Hans Holmberg <hans.holmberg@xxxxxxxxxxxx>
> On Thu, Nov 22, 2018 at 2:47 PM Javier GonzÃlez <javier@xxxxxxxxxxx> wrote:
> > The current kref implementation around pblk global caches triggers a
> > false positive on refcount_inc_checked() (when called) as the kref is
> > initialized to 0. Instead of usint kref_inc() on a 0 reference, which is
> > in principle correct, use kref_init() to avoid the check. This is also
> > more explicit about what actually happens on cache creation.
> >
> > In the process, do a small refactoring to use kref helpers.
> >
> > Signed-off-by: Javier GonzÃlez <javier@xxxxxxxxxxxx>
> > ---
> >   drivers/lightnvm/pblk-init.c | 14 +++++---------
> >   1 file changed, 5 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> > index 13822594647c..e225bd60cbb4 100644
> > --- a/drivers/lightnvm/pblk-init.c
> > +++ b/drivers/lightnvm/pblk-init.c
> > @@ -350,23 +350,19 @@ static int pblk_create_global_caches(void)
> >
> >   static int pblk_get_global_caches(void)
> >   {
> > -       int ret;
> > +       int ret = 0;
> >
> >          mutex_lock(&pblk_caches.mutex);
> >
> > -       if (kref_read(&pblk_caches.kref) > 0) {
> > -               kref_get(&pblk_caches.kref);
> > -               mutex_unlock(&pblk_caches.mutex);
> > -               return 0;
> > -       }
> > +       if (kref_get_unless_zero(&pblk_caches.kref))
> > +               goto out;
> >
> >          ret = pblk_create_global_caches();
> > -
> >          if (!ret)
> > -               kref_get(&pblk_caches.kref);
> > +               kref_init(&pblk_caches.kref);
> >
> > +out:
> >          mutex_unlock(&pblk_caches.mutex);
> > -
> >          return ret;
> >   }
> >
> > --
> > 2.7.4

Picked up for 4.21.