On Wed, Mar 1, 2023 at 1:31 PM Florian Westphal [off-list ref] wrote:

Eric Dumazet [off-list ref] wrote:

quoted

BTW I was curious why Google was not seeing this, and it appears Brian Vasquez
forgot to upstream this change...

commit 5ea2f21d6c1078d2c563cb455ad5877b4ada94e1
Author: Brian Vazquez [off-list ref]
Date:   Thu Mar 3 19:09:49 2022 -0800

    PRODKERNEL: net-directcall: annotate tcp_leave_memory_pressure and
    tcp_getsockopt

diff --git a/net/core/sock.c b/net/core/sock.c
index 05032b399c873984e5297898d647905ca9f21f2e..54cb989dc162f3982380ac12cf5a150214e209a2

100644

--- a/net/core/sock.c
+++ b/net/core/sock.c

@@ -2647,10 +2647,13 @@ static void sk_enter_memory_pressure(struct sock *sk)
        sk->sk_prot->enter_memory_pressure(sk);
 }

+INDIRECT_CALLABLE_DECLARE(void tcp_leave_memory_pressure(struct sock *sk));
+
 static void sk_leave_memory_pressure(struct sock *sk)
 {
        if (sk->sk_prot->leave_memory_pressure) {
-               sk->sk_prot->leave_memory_pressure(sk);
+               INDIRECT_CALL_1(sk->sk_prot->leave_memory_pressure,
+                               tcp_leave_memory_pressure, sk);
        } else {
                unsigned long *memory_pressure = sk->sk_prot->memory_pressure;

re-tested: this change also resolves the regression i was seeing.

If you prefer to upstream this instead of the proposed change then I'm
fine with that.

This seems a bit less risky, if the plan is to add this to stable trees.
( We had this mitigation for ~4 years at Google)

I will rebase Brian patch (only the tcp_leave_memory_pressure part) and send it.

Thanks !