On Thu, Aug 11, 2022 at 10:49:13AM +0800, Yafang Shao wrote:
> On Thu, Aug 11, 2022 at 1:07 AM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote:
> >
> > On Wed, Aug 10, 2022 at 03:18:30PM +0000, Yafang Shao wrote:
> > > The memcg may be the root_mem_cgroup, in which case we shouldn't put it.
> >
> > No, it is ok to put root_mem_cgroup. css_put already handles the root
> > cgroups.
> >
>
> Ah, this commit log doesn't describe the issue clearly. I should improve it.
> The issue is that in bpf_map_get_memcg() it doesn't get the objcg if
> map->objcg is NULL (that can happen if the map belongs to the root
> memcg), so we shouldn't put the objcg if map->objcg is NULL neither in
> bpf_map_put_memcg().
Sorry I am still not understanding. We are not 'getting' objcg in
bpf_map_get_memcg(). We are 'getting' memcg from map->objcg and if that
is NULL the function is returning root memcg and putting root memcg is
totally fine. Or are you saying that root_mem_cgroup is NULL?
> Maybe the change below would be more reasonable ?
>
> +static void bpf_map_put_memcg(const struct bpf_map *map, struct
> mem_cgroup *memcg)
> +{
> + if (map->objcg)
> + mem_cgroup_put(memcg);
> +}
>
> --
> Regards
> Yafang
