Commit 2d0c88e8 authored by Abel Wu's avatar Abel Wu Committed by Jakub Kicinski
Browse files

sock: Fix misuse of sk_under_memory_pressure() 



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: e1aab161 ("socket: initial cgroup code.")
Signed-off-by: default avatarAbel Wu <wuyun.abel@bytedance.com>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Link: https://lore.kernel.org/r/20230816091226.1542-1-wuyun.abel@bytedance.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 54c9016e

include/net/sock.h

+6 −0
Original line number Diff line number Diff line
@@ -1420,6 +1420,12 @@ 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)

net/core/sock.c

+1 −1
Original line number Diff line number Diff line
@@ -3159,7 +3159,7 @@ 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);

}