From: Geliang Tang <tanggeliang@kylinos.cn>

Before commit c5c37af6ecad9 ("tcp: Convert do_tcp_sendpages() to use
MSG_SPLICE_PAGES"), do_tcp_sendpages() did not call
tcp_rate_check_app_limited() internally, so callers needed an explicit
tcp_rate_check_app_limited() to cover it. That commit replaced
do_tcp_sendpages() with direct tcp_sendmsg_locked() calls, which perform
the check on every path that queues data. The outer call became redundant
but was left in place.

The site changed here, tls_push_sg(), holds the socket lock and invokes
tcp_sendmsg_locked() on every iteration. The early-return paths in
tcp_sendmsg_locked() that skip tcp_rate_check_app_limited() -- the
MSG_ZEROCOPY allocation failure and MSG_FASTOPEN branches -- return
without queueing any MSG_SPLICE_PAGES data, so there is no functional
consequence from omitting the outer check.

A potential benefit of this change is that it facilitates future reuse of
tls_push_sg() for KTLS 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.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
Note:

The patch benefits my ongoing "MPTCP KTLS support" work [1]. In patch 9
of that series, I had defined a check_app_limited() interface in struct
tls_prot_ops, but this interface is unnecessary if we can drop this
redundant call.

v3:
 - send this patch separately to net-next as Jakub suggested.
 - update the commit log.

v2:
 - drop the "Fixes" tags and update the prefixes and commit logs as Jiayuan
   suggested.
 - https://patchwork.kernel.org/project/netdevbpf/cover/cover.1789469930.git.tanggeliang@kylinos.cn/

v1:
 - https://patchwork.kernel.org/project/netdevbpf/cover/cover.1789368148.git.tanggeliang@kylinos.cn/

[1]
MPTCP KTLS support
https://lore.kernel.org/netdev/cover.1782123118.git.tanggeliang@kylinos.cn/
---
 net/tls/tls_main.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index fbb274287aa5..8bdb78718a8d 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -185,8 +185,6 @@ int tls_push_sg(struct sock *sk,
 
 	ctx->splicing_pages = true;
 	while (1) {
-		/* is sending application-limited? */
-		tcp_rate_check_app_limited(sk);
 		p = sg_page(sg);
 retry:
 		bvec_set_page(&bvec, p, size, offset);
-- 
2.53.0

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 17 Sep 2026 16:42:06 +0800 you wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> Before commit c5c37af6ecad9 ("tcp: Convert do_tcp_sendpages() to use
> MSG_SPLICE_PAGES"), do_tcp_sendpages() did not call
> tcp_rate_check_app_limited() internally, so callers needed an explicit
> tcp_rate_check_app_limited() to cover it. That commit replaced
> do_tcp_sendpages() with direct tcp_sendmsg_locked() calls, which perform
> the check on every path that queues data. The outer call became redundant
> but was left in place.
> 
> [...]

Here is the summary with links:
  - [net-next,v3] tls: drop duplicate check_app_limited in tls_push_sg
    https://git.kernel.org/netdev/net-next/c/cd7e4b1e4796

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Perf: Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/35202892935

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/b87643cd6e76
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1167234


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)