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 1bbdddcf615422e98cea17113d8878c7f7d70d1e..699408944952ca60b9063b9a501237314f923c80 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1445,6 +1445,12 @@ 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 3b5304f084ef320bc1823f8349c8d04728588113..509773919d3021ea5c119266b13671f86f1c103f 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3099,7 +3099,7 @@ 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);
 }