Re: [PATCH v3 07/11] lib/ref_tracker: remove warnings in case of allocation failure

[Andrzej Hajda]

On 22.02.2022 00:54, Eric Dumazet wrote:
> On Mon, Feb 21, 2022 at 3:26 PM Andrzej Hajda <andrzej.hajda@xxxxxxxxx> wrote:
> > Library can handle allocation failures. To avoid allocation warnings
> > __GFP_NOWARN has been added everywhere. Moreover GFP_ATOMIC has been
> > replaced with GFP_NOWAIT in case of stack allocation on tracker free
> > call.
> >
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > ---
> >   lib/ref_tracker.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
> > index 2ef4596b6b36f..cae4498fcfd70 100644
> > --- a/lib/ref_tracker.c
> > +++ b/lib/ref_tracker.c
> > @@ -189,7 +189,7 @@ int ref_tracker_alloc(struct ref_tracker_dir *dir,
> >          unsigned long entries[REF_TRACKER_STACK_ENTRIES];
> >          struct ref_tracker *tracker;
> >          unsigned int nr_entries;
> > -       gfp_t gfp_mask = gfp;
> > +       gfp_t gfp_mask = gfp | __GFP_NOWARN;
> SGTM
>
> >          unsigned long flags;
> >
> >          WARN_ON_ONCE(dir->dead);
> > @@ -237,7 +237,8 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
> >                  return -EEXIST;
> >          }
> >          nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
> > -       stack_handle = stack_depot_save(entries, nr_entries, GFP_ATOMIC);
> > +       stack_handle = stack_depot_save(entries, nr_entries,
> > +                                       GFP_NOWAIT | __GFP_NOWARN);
> Last time I looked at this, __GFP_NOWARN was enforced in __stack_depot_save()

You are right, however I am not sure if we should count on unexpected 
(at least for me) and undocumented behavior.
Currently we do not need to rely on some hidden feature.

Regards
Andrzej

> >          spin_lock_irqsave(&dir->lock, flags);
> >          if (tracker->dead) {
> > --
> > 2.25.1