On Sat, Apr 16, 2022 at 11:39 PM Vasily Averin <vvs@xxxxxxxxxx> wrote:
>
> __register_pernet_operations() executes init hook of registered
> pernet_operation structure in all existing net namespaces.
>
> Typically, these hooks are called by a process associated with
> the specified net namespace, and all __GFP_ACCOUNTING marked
> allocation are accounted for corresponding container/memcg.
>
> However __register_pernet_operations() calls the hooks in the same
> context, and as a result all marked allocations are accounted
> to one memcg for all processed net namespaces.
>
> This patch adjusts active memcg for each net namespace and helps
> to account memory allocated inside ops_init() into the proper memcg.
>
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxx>
> ---
> Dear Vlastimil, Roman,
> I'm not sure that memcg is used correctly here,
> is it perhaps some additional locking required?
> ---
> net/core/net_namespace.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index a5b5bb99c644..171c6e0b2337 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -26,6 +26,7 @@
> #include <net/net_namespace.h>
> #include <net/netns/generic.h>
>
> +#include <linux/sched/mm.h>
> /*
> * Our network namespace constructor/destructor lists
> */
> @@ -1147,7 +1148,13 @@ static int __register_pernet_operations(struct list_head *list,
> * setup_net() and cleanup_net() are not possible.
> */
> for_each_net(net) {
> + struct mem_cgroup *old, *memcg = NULL;
> +#ifdef CONFIG_MEMCG
> + memcg = (net == &init_net) ? root_mem_cgroup : mem_cgroup_from_obj(net);
memcg from obj is unstable, so you need a reference on memcg. You can
introduce get_mem_cgroup_from_kmem() which works for both
MEMCG_DATA_OBJCGS and MEMCG_DATA_KMEM. For uncharged objects (like
init_net) it should return NULL.
> +#endif
> + old = set_active_memcg(memcg);
> error = ops_init(ops, net);
> + set_active_memcg(old);
> if (error)
> goto out_undo;
> list_add_tail(&net->exit_list, &net_exit_list);
> --
> 2.31.1
>
