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net-memcg: Introduce mem_cgroup_from_sk().

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We will store a flag in the lowest bit of sk->sk_memcg.

Then, directly dereferencing sk->sk_memcg will be illegal, and we
do not want to allow touching the raw sk->sk_memcg in many places.

Let's introduce mem_cgroup_from_sk().

Other places accessing the raw sk->sk_memcg will be converted later.

Note that we cannot define the helper as an inline function in
memcontrol.h as we cannot access any fields of struct sock there
due to circular dependency, so it is placed in sock.h.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Link: https://patch.msgid.link/20250815201712.1745332-7-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-08-15 20:16:14 +00:00
committed by Jakub Kicinski
parent bd4aa23373
commit f7161b234f
3 changed files with 22 additions and 5 deletions
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12
include/net/sock.h
View File

@@ -2594,6 +2594,18 @@ static inline gfp_t gfp_memcg_charge(void)
return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;
}
#ifdef CONFIG_MEMCG
static inline struct mem_cgroup *mem_cgroup_from_sk(const struct sock *sk)
{
return sk->sk_memcg;
}
#else
static inline struct mem_cgroup *mem_cgroup_from_sk(const struct sock *sk)
{
return NULL;
}
#endif
static inline long sock_rcvtimeo(const struct sock *sk, bool noblock)
{
return noblock ? 0 : READ_ONCE(sk->sk_rcvtimeo);

13
mm/memcontrol.c
View File

@@ -5020,19 +5020,24 @@ out:
void mem_cgroup_sk_free(struct sock *sk)
{
if (sk->sk_memcg)
css_put(&sk->sk_memcg->css);
struct mem_cgroup *memcg = mem_cgroup_from_sk(sk);
if (memcg)
css_put(&memcg->css);
}
void mem_cgroup_sk_inherit(const struct sock *sk, struct sock *newsk)
{
struct mem_cgroup *memcg;
if (sk->sk_memcg == newsk->sk_memcg)
return;
mem_cgroup_sk_free(newsk);
if (sk->sk_memcg)
css_get(&sk->sk_memcg->css);
memcg = mem_cgroup_from_sk(sk);
if (memcg)
css_get(&memcg->css);
newsk->sk_memcg = sk->sk_memcg;
}

2
net/ipv4/inet_connection_sock.c
View File

@@ -718,7 +718,7 @@ struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg)
lock_sock(newsk);
mem_cgroup_sk_alloc(newsk);
if (newsk->sk_memcg) {
if (mem_cgroup_from_sk(newsk)) {
/* The socket has not been accepted yet, no need
* to look at newsk->sk_wmem_queued.
*/