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Thu, 14 Aug 2025 19:31:19 -0700 (PDT) MIME-Version: 1.0 References: <20250814200912.1040628-1-kuniyu@google.com> <20250814200912.1040628-2-kuniyu@google.com> In-Reply-To: From: Kuniyuki Iwashima Date: Thu, 14 Aug 2025 19:31:08 -0700 X-Gm-Features: Ac12FXx0oP3F9dx8jnlPn8DV0XXtg4bMkD2eiCckKKtAFl_RyUY4z0YgVFHXtPQ Message-ID: Subject: Re: [PATCH v4 net-next 01/10] mptcp: Fix up subflow's memcg when CONFIG_SOCK_CGROUP_DATA=n. 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 X-Rspamd-Queue-Id: ACE7B20006 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: tntjarpwey56djdwa3zk48m9dzgofkkg X-HE-Tag: 1755225080-332173 X-HE-Meta: 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 4wUYbMJf dDvert3EUaUBklexSoLAjVm98pniM26xLnzlj5+jiCtzy+oJDgXsGuqUpjyIUFUchQ1FfSaVaLLmQwO4gtSE8CdxqmTDC5s6dFrMicZJc2hkEWVEcROjpK6FcSEA9C1tJmbwTYXtahm0ob73DoQ2Sknx7W/Okja8xSRBpTU5EfhjyldZTh8gOXb4jb6L2BIJ6BJqskCsOUlfv0WFeFklaBYz88QhAOgJFE5kpHwzUQbOXzvkNkJoHOkOrjxfl8qFxFy0IelmkDntcNBJSEtgsUhUQ1qzXAqfkgXD9ZIVU0aQYGifLLDJ4zGftLuWKUVV0YA78 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 14, 2025 at 6:06=E2=80=AFPM Shakeel Butt wrote: > > On Thu, Aug 14, 2025 at 05:05:56PM -0700, Kuniyuki Iwashima wrote: > > On Thu, Aug 14, 2025 at 4:46=E2=80=AFPM Shakeel Butt wrote: > > > > > > On Thu, Aug 14, 2025 at 04:27:31PM -0700, Kuniyuki Iwashima wrote: > > > > 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 f= ix > > > > > > it up from the parent socket's sk->sk_memcg in mptcp_attach_cgr= oup(). > > > > > > > > > > > > Although the code is placed under #ifdef CONFIG_MEMCG, it is bu= ried > > > > > > under #ifdef CONFIG_SOCK_CGROUP_DATA. > > > > > > > > > > > > The two configs are orthogonal. If CONFIG_MEMCG is enabled wit= hout > > > > > > CONFIG_SOCK_CGROUP_DATA, the subflow's memory usage is not char= ged > > > > > > 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 c= group") > > > > > > 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. > > > > > > > > > > If we are making mem_cgroup_sk_alloc() work with set_active_memcg() > > > infra then make it work for both in_task() and !in_task() contexts. > > > > Considering e876ecc67db80, then I think we should add > > set_active_memcg_in_task() and active_memcg_in_task(). > > > > or at least we need WARN_ON() if we want to place active_memcg() > > before the in_task() check, but this looks ugly. > > > > memcg =3D active_memcg(); > > if (!in_task() && !memcg) > > return; > > DEBUG_NET_WARN_ON_ONCE(!in_task() && memcg)) > > You don't have to use the code as is. It is just an example. Basically I > am asking if in future someone does the following: > > // in !in_task() context > old_memcg =3D set_active_memcg(new_memcg); > sk =3D sk_alloc(); > set_active_memcg(old_memcg); > > mem_cgroup_sk_alloc() should work and associate the sk with the > new_memcg. > > You can manually inline active_memcg() function to avoid multiple > in_task() checks like below: Will do so, thanks! > > void mem_cgroup_sk_alloc(struct sock *sk) > { > struct mem_cgroup *memcg; > > if (!mem_cgroup_sockets_enabled) > return; > > if (!in_task()) { > memcg =3D this_cpu_read(int_active_memcg); > > /* > * Do not associate the sock with unrelated interrupted > * task's memcg. > */ > if (!memcg) > return; > } else { > memcg =3D current->active_memcg; > } > > rcu_read_lock(); > if (likely(!memcg)) > memcg =3D mem_cgroup_from_task(current); > if (mem_cgroup_is_root(memcg)) > goto out; > if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg1_tcpmem_a= ctive(memcg)) > goto out; > if (css_tryget(&memcg->css)) > sk->sk_memcg =3D memcg; > out: > rcu_read_unlock(); > } >