6.17-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@google.com
[ Upstream commit 68889dfd547bd8eabc5a98b58475d7b901cf5129 ]
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 move the code out of the wrong ifdef guard.
Note that sk->sk_memcg is freed in sk_prot_free() and the parent sk holds the refcnt of memcg->css here, so we don't need to use css_tryget().
Fixes: 3764b0c5651e3 ("mptcp: attach subflow socket to parent cgroup") Signed-off-by: Kuniyuki Iwashima kuniyu@google.com Reviewed-by: Eric Dumazet edumazet@google.com Acked-by: Matthieu Baerts (NGI0) matttbe@kernel.org Acked-by: Shakeel Butt shakeel.butt@linux.dev Link: https://patch.msgid.link/20250815201712.1745332-2-kuniyu@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/memcontrol.h | 6 ++++++ mm/memcontrol.c | 13 +++++++++++++ net/mptcp/subflow.c | 11 +++-------- 3 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 785173aa0739c..25921fbec6856 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1604,6 +1604,7 @@ extern struct static_key_false memcg_sockets_enabled_key; #define mem_cgroup_sockets_enabled static_branch_unlikely(&memcg_sockets_enabled_key) void mem_cgroup_sk_alloc(struct sock *sk); void mem_cgroup_sk_free(struct sock *sk); +void mem_cgroup_sk_inherit(const struct sock *sk, struct sock *newsk);
#if BITS_PER_LONG < 64 static inline void mem_cgroup_set_socket_pressure(struct mem_cgroup *memcg) @@ -1661,6 +1662,11 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg); #define mem_cgroup_sockets_enabled 0 static inline void mem_cgroup_sk_alloc(struct sock *sk) { }; static inline void mem_cgroup_sk_free(struct sock *sk) { }; + +static inline void mem_cgroup_sk_inherit(const struct sock *sk, struct sock *newsk) +{ +} + static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg) { return false; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8dd7fbed5a942..46713b9ece063 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5024,6 +5024,19 @@ void mem_cgroup_sk_free(struct sock *sk) css_put(&sk->sk_memcg->css); }
+void mem_cgroup_sk_inherit(const struct sock *sk, struct sock *newsk) +{ + if (sk->sk_memcg == newsk->sk_memcg) + return; + + mem_cgroup_sk_free(newsk); + + if (sk->sk_memcg) + css_get(&sk->sk_memcg->css); + + newsk->sk_memcg = sk->sk_memcg; +} + /** * mem_cgroup_charge_skmem - charge socket memory * @memcg: memcg to charge diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index f31a3a79531a2..e8325890a3223 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1721,19 +1721,14 @@ static void mptcp_attach_cgroup(struct sock *parent, struct sock *child) /* only the additional subflows created by kworkers have to be modified */ if (cgroup_id(sock_cgroup_ptr(parent_skcd)) != cgroup_id(sock_cgroup_ptr(child_skcd))) { -#ifdef CONFIG_MEMCG - struct mem_cgroup *memcg = parent->sk_memcg; - - mem_cgroup_sk_free(child); - if (memcg && css_tryget(&memcg->css)) - child->sk_memcg = memcg; -#endif /* CONFIG_MEMCG */ - cgroup_sk_free(child_skcd); *child_skcd = *parent_skcd; cgroup_sk_clone(child_skcd); } #endif /* CONFIG_SOCK_CGROUP_DATA */ + + if (mem_cgroup_sockets_enabled) + mem_cgroup_sk_inherit(parent, child); }
static void mptcp_subflow_ops_override(struct sock *ssk)