net: tcp: Add noinline_for_tracing annotation for tcp_drop_reason()

We previously hooked the tcp_drop_reason() function using BPF to monitor
TCP drop reasons. However, after upgrading our compiler from GCC 9 to GCC
11, tcp_drop_reason() is now inlined, preventing us from hooking into it.
To address this, it would be beneficial to make noinline explicitly for
tracing.

Link: https://lore.kernel.org/netdev/CANn89iJuShCmidCi_ZkYABtmscwbVjhuDta1MS5LxV_4H9tKOA@mail.gmail.com/
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Menglong Dong <menglong8.dong@gmail.com>
Link: https://patch.msgid.link/20241024093742.87681-3-laoar.shao@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2d844e1f867f0a67187fcd7f5eed2e30156f2bd7..5bdf13ac26ef03615fd441d9401334b35bf06bd6 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4921,8 +4921,8 @@ static bool tcp_ooo_try_coalesce(struct sock *sk,
        return res;
 }
 
-static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
-                           enum skb_drop_reason reason)
+noinline_for_tracing static void
+tcp_drop_reason(struct sock *sk, struct sk_buff *skb, enum skb_drop_reason reason)
 {
        sk_drops_add(sk, skb);
        sk_skb_reason_drop(sk, skb, reason);