Re: [PATCH] mm: memcg/slab: fix obj_cgroup_charge() return value handling

[Roman Gushchin]

On Thu, Nov 26, 2020 at 09:55:24PM -0800, Shakeel Butt wrote:
> On Thu, Nov 26, 2020 at 8:14 PM Roman Gushchin <guro@xxxxxx> wrote:
> >
> > Commit 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches
> > for all allocations") introduced a regression into the handling of the
> > obj_cgroup_charge() return value. If a non-zero value is returned
> > (indicating of exceeding one of memory.max limits), the allocation
> > should fail, instead of falling back to non-accounted mode.
> >
> > To make the code more readable, move memcg_slab_pre_alloc_hook()
> > and memcg_slab_post_alloc_hook() calling conditions into bodies
> > of these hooks.
> >
> > Fixes: 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all allocations")
> > Signed-off-by: Roman Gushchin <guro@xxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> >  mm/slab.h | 40 ++++++++++++++++++++++++----------------
> >  1 file changed, 24 insertions(+), 16 deletions(-)
> >
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 59aeb0d9f11b..5dc89d8fb05e 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -257,22 +257,32 @@ static inline size_t obj_full_size(struct kmem_cache *s)
> >         return s->size + sizeof(struct obj_cgroup *);
> >  }
> >
> > -static inline struct obj_cgroup *memcg_slab_pre_alloc_hook(struct kmem_cache *s,
> > -                                                          size_t objects,
> > -                                                          gfp_t flags)
> > +/*
> > + * Returns true if the allocation should fail.
> 
> IMO returning false if the allocation should fail makes this more
> clear. Otherwise the patch looks good to me.

Ok, I agree. Here is an updated version.

Thank you for looking in!

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