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>
---
include/linux/memcontrol.h | 7 +++++++
mm/memcontrol.c | 10 ++++++++++
net/mptcp/subflow.c | 11 +++--------
3 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 87b6688f124a7..d8319ad5e8ea7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1602,6 +1602,8 @@ 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);
+
static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
{
#ifdef CONFIG_MEMCG_V1
@@ -1623,6 +1625,11 @@ 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 70fdeda1120b3..54eb25d8d555c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5090,6 +5090,16 @@ 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);
+ 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 1802bc5435a1a..f21d90fb1a19d 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1716,19 +1716,14 @@ 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 && parent->sk_memcg)
+ mem_cgroup_sk_inherit(parent, child);
}
static void mptcp_subflow_ops_override(struct sock *ssk)
--
2.50.0.727.gbf7dc18ff4-goog