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 93a6717213aebe04df6eab972201c51a6e3d5126..6b12b62417e08ecca02a2e380ce86c9394257020 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1381,6 +1381,12 @@ 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 1f9401d757cbb78f5b15ffe8300c49e926b1284e..ae1e9e2b825576b66994199e35eeac7368ed5168 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2880,7 +2880,7 @@ 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);
 }