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To: Shakeel Butt Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Neal Cardwell , Paolo Abeni , Willem de Bruijn , Matthieu Baerts , Mat Martineau , Johannes Weiner , Michal Hocko , Roman Gushchin , Andrew Morton , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Tejun Heo , Simon Horman , Geliang Tang , Muchun Song , Mina Almasry , Kuniyuki Iwashima , netdev@vger.kernel.org, mptcp@lists.linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, Aug 14, 2025 at 2:44=E2=80=AFPM Shakeel Butt wrote: > > On Thu, Aug 14, 2025 at 08:08:33PM +0000, Kuniyuki Iwashima wrote: > > When sk_alloc() allocates a socket, mem_cgroup_sk_alloc() sets > > sk->sk_memcg based on the current task. > > > > MPTCP subflow socket creation is triggered from userspace or > > an in-kernel worker. > > > > In the latter case, sk->sk_memcg is not what we want. So, we fix > > it up from the parent socket's sk->sk_memcg in mptcp_attach_cgroup(). > > > > Although the code is placed under #ifdef CONFIG_MEMCG, it is buried > > under #ifdef CONFIG_SOCK_CGROUP_DATA. > > > > The two configs are orthogonal. If CONFIG_MEMCG is enabled without > > CONFIG_SOCK_CGROUP_DATA, the subflow's memory usage is not charged > > correctly. > > > > Let's wrap sock_create_kern() for subflow with set_active_memcg() > > using the parent sk->sk_memcg. > > > > Fixes: 3764b0c5651e3 ("mptcp: attach subflow socket to parent cgroup") > > Suggested-by: Michal Koutn=C3=BD > > Signed-off-by: Kuniyuki Iwashima > > --- > > mm/memcontrol.c | 5 ++++- > > net/mptcp/subflow.c | 11 +++-------- > > 2 files changed, 7 insertions(+), 9 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 8dd7fbed5a94..450862e7fd7a 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -5006,8 +5006,11 @@ void mem_cgroup_sk_alloc(struct sock *sk) > > if (!in_task()) > > return; > > > > + memcg =3D current->active_memcg; > > + > > Use active_memcg() instead of current->active_memcg and do before the > !in_task() check. Why not reuse the !in_task() check here ? We never use int_active_memcg for socket and also know int_active_memcg is always NULL here. > > Basically something like following: > > memcg =3D active_memcg(); > /* Do not associate the sock with unrelated interrupted task's me= mcg. */ > if (!in_task() && !memcg) > return;