Re: [PATCH bpf 1/2] bpf: drop duplicate check_app_limited in tcp_bpf_push

[Jiayuan Chen <jiayuan.chen@linux.dev>]

On 9/14/26 3:14 PM, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
>
> When the sendpage->MSG_SPLICE_PAGES migration series replaced
> do_tcp_sendpages() with direct tcp_sendmsg_locked() calls, callers that
> had used do_tcp_sendpages() kept an explicit tcp_rate_check_app_limited(sk)
> that was originally needed to cover do_tcp_sendpages() (which did not call
> tcp_rate_check_app_limited()). After the inlining, tcp_sendmsg_locked()
> always provides the check, and the outer call became redundant.
>
> The site changed here, tcp_bpf_push(), is a MSG_SPLICE_PAGES loop that
> holds the socket lock and only iterates when size > 0; tcp_sendmsg_locked()
> is invoked on every iteration with state identical to what the outer call
> sees, so dropping the outer call is safe and behavior-preserving.
>
> A potential benefit of this change is that it facilitates future reuse of
> tcp_bpf_push() for sockmap support in protocols beyond TCP, such as MPTCP.
> Since tcp_rate_check_app_limited() is TCP-specific while sendmsg_locked()
> is a generic interface in struct proto_ops, this change allows us to switch
> to different protocols via sk->sk_socket->ops->sendmsg_locked() without
> carrying protocol-specific assumptions.
>
> Fixes: ebf2e8860eea ("tcp_bpf: Inline do_tcp_sendpages as it's now a wrapper around tcp_sendmsg")


Same as the tls one: this looks like a cleanup to me. Is there a real 
regression that affects kernel or user behavior?

Do we really need a Fixes tag?


> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> ---
>   net/ipv4/tcp_bpf.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index 2e234d155b5e..d5fcf3ce4861 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -108,7 +108,6 @@ static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
>   		off  = sge->offset;
>   		page = sg_page(sge);
>   
> -		tcp_rate_check_app_limited(sk);
>   retry:
>   		msghdr.msg_flags = flags | MSG_SPLICE_PAGES;
>   		has_tx_ulp = tls_sw_has_ctx_tx(sk);