Re: [PATCH bpf-next v2 5/7] mm: introduce BPF kfunc to access memory events

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Sun, Dec 21, 2025 at 2:49 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Dec 19, 2025 at 6:13 PM Roman Gushchin <roman.gushchin@linux.dev> wrote:
> >
> > From: JP Kobryn <inwardvessel@gmail.com>
> >
> > Introduce BPF kfunc to access memory events, e.g.:
> > MEMCG_LOW, MEMCG_MAX, MEMCG_OOM, MEMCG_OOM_KILL etc.
> >
> > Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
> > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
> > Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
> > ---
> >  mm/bpf_memcontrol.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c
> > index d84fe6f3ed43..858eb43766ce 100644
> > --- a/mm/bpf_memcontrol.c
> > +++ b/mm/bpf_memcontrol.c
> > @@ -103,6 +103,22 @@ __bpf_kfunc unsigned long bpf_mem_cgroup_usage(struct mem_cgroup *memcg)
> >         return mem_cgroup_usage(memcg, false) * PAGE_SIZE;
> >  }
> >
> > +/**
> > + * bpf_mem_cgroup_memory_events - Read memory cgroup's memory event value
> > + * @memcg: memory cgroup
> > + * @event: memory event id
> > + *
> > + * Returns current memory event count.
> > + */
> > +__bpf_kfunc unsigned long bpf_mem_cgroup_memory_events(struct mem_cgroup *memcg,
> > +                                               enum memcg_memory_event event)
> > +{
> > +       if (event >= MEMCG_NR_MEMORY_EVENTS)
> > +               return (unsigned long)-1;
> > +
> > +       return atomic_long_read(&memcg->memory_events[event]);
> > +}
>
> Why is patch 5 not squashed with patch 4?
> I'd think placing bpf_mem_cgroup_memory_events()
> right next to bpf_mem_cgroup_vm_events() in the same patch
> will make the difference more clear.
> For non-mm people the names are very close and on the first glance
> it looks like a duplicate.

Also see a bunch of kdoc warnings flagged by CI.