sock: Fix misuse of sk_under_memory_pressure()

[ Upstream commit 2d0c88e84e483982067a82073f6125490ddf3614 ]

The status of global socket memory pressure is updated when:

  a) __sk_mem_raise_allocated():

	enter: sk_memory_allocated(sk) >  sysctl_mem[1]
	leave: sk_memory_allocated(sk) <= sysctl_mem[0]

  b) __sk_mem_reduce_allocated():

	leave: sk_under_memory_pressure(sk) &&
		sk_memory_allocated(sk) < sysctl_mem[0]

So the conditions of leaving global pressure are inconstant, which
may lead to the situation that one pressured net-memcg prevents the
global pressure from being cleared when there is indeed no global
pressure, thus the global constrains are still in effect unexpectedly
on the other sockets.

This patch fixes this by ignoring the net-memcg's pressure when
deciding whether should leave global memory pressure.

Fixes: e1aab161e013 ("socket: initial cgroup code.")
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Link: https://lore.kernel.org/r/20230816091226.1542-1-wuyun.abel@bytedance.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/sock.h b/include/net/sock.h
index ad468fe71413a33a0ac72442ebc2596a565ee06d..415f3840a26aa5f71923a5e2409d8e672ec1e3ab 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1421,6 +1421,12 @@ static inline bool sk_has_memory_pressure(const struct sock *sk)
        return sk->sk_prot->memory_pressure != NULL;
 }
 
+static inline bool sk_under_global_memory_pressure(const struct sock *sk)
+{
+       return sk->sk_prot->memory_pressure &&
+               !!*sk->sk_prot->memory_pressure;
+}
+
 static inline bool sk_under_memory_pressure(const struct sock *sk)
 {
        if (!sk->sk_prot->memory_pressure)

diff --git a/net/core/sock.c b/net/core/sock.c
index 1f31a97100d4f795ea4ee811e672304e067adca7..8451a95266bf005c0ffe753ac60b6d4d6f75a653 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3107,7 +3107,7 @@ void __sk_mem_reduce_allocated(struct sock *sk, int amount)
        if (mem_cgroup_sockets_enabled && sk->sk_memcg)
                mem_cgroup_uncharge_skmem(sk->sk_memcg, amount);
 
-       if (sk_under_memory_pressure(sk) &&
+       if (sk_under_global_memory_pressure(sk) &&
            (sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)))
                sk_leave_memory_pressure(sk);
 }