On Sun, 2 Oct 2022, Geliang Tang wrote:
> This patch moves the duplicate code from __mptcp_push_pending() and
> __mptcp_subflow_push_pending() into a new helper function, named
> __subflow_push_pending(). And simplify __mptcp_push_pending() by
> invoking this helper.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 90 +++++++++++++++++++++++---------------------
> 1 file changed, 48 insertions(+), 42 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 296b7135e9cf..66c97ac06a4e 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1480,12 +1480,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
> return ssk;
> }
>
> -static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
> -{
> - tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
> - release_sock(ssk);
> -}
> -
> static void mptcp_update_post_push(struct mptcp_sock *msk,
> struct mptcp_data_frag *dfrag,
> u32 sent)
> @@ -1517,6 +1511,52 @@ void mptcp_check_and_set_pending(struct sock *sk)
> mptcp_sk(sk)->push_pending |= BIT(MPTCP_PUSH_PENDING);
> }
>
> +static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
> + struct mptcp_sendmsg_info *info)
> +{
> + struct mptcp_sock *msk = mptcp_sk(sk);
> + struct mptcp_data_frag *dfrag;
> + int len, copied = 0;
> +
> + while ((dfrag = mptcp_send_head(sk))) {
> + info->sent = dfrag->already_sent;
> + info->limit = dfrag->data_len;
> + len = dfrag->data_len - dfrag->already_sent;
> + while (len > 0) {
> + int ret = 0;
> +
> + ret = mptcp_sendmsg_frag(sk, ssk, dfrag, info);
> + if (ret <= 0) {
> + if (ret == -EAGAIN)
> + continue;
In the older code, the scheduler got called again in the -EAGAIN case.
With this refactored code, this could get in a very tight loop if
mptcp_sendmsg_frag() returns. I think it's necessary to cleanly finish
this loop iteration and let the scheduler run again in this -EAGAIN case.
> + goto out;
> + }
> +
> + info->sent += ret;
> + copied += ret;
> + len -= ret;
> +
> + mptcp_update_post_push(msk, dfrag, ret);
> + }
> + WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
> +
> + if (msk->snd_burst <= 0 ||
> + !sk_stream_memory_free(ssk) ||
> + !mptcp_subflow_active(mptcp_subflow_ctx(ssk))) {
> + goto out;
> + }
> + mptcp_set_timeout(sk);
> + }
> +
> +out:
> + if (copied) {
> + tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle,
> + info->size_goal);
> + }
> +
> + return copied;
> +}
> +
> void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> {
> struct mptcp_sock *msk = mptcp_sk(sk);
> @@ -1524,48 +1564,14 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> .flags = flags,
> };
> bool do_check_data_fin = false;
> - struct mptcp_data_frag *dfrag;
> struct sock *ssk;
> - int len;
>
> while (mptcp_send_head(sk) && (ssk = mptcp_subflow_get_send(msk))) {
> lock_sock(ssk);
> -
> - while ((dfrag = mptcp_send_head(sk))) {
> - info.sent = dfrag->already_sent;
> - info.limit = dfrag->data_len;
> - len = dfrag->data_len - dfrag->already_sent;
> - while (len > 0) {
> - int ret = 0;
> -
> - ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> - if (ret <= 0) {
> - if (ret == -EAGAIN)
> - continue;
> - mptcp_push_release(ssk, &info);
> - goto out;
> - }
> -
> - do_check_data_fin = true;
> - info.sent += ret;
> - len -= ret;
> -
> - mptcp_update_post_push(msk, dfrag, ret);
> - }
> - WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
> -
> - if (msk->snd_burst <= 0 ||
> - !sk_stream_memory_free(ssk) ||
> - !mptcp_subflow_active(mptcp_subflow_ctx(ssk))) {
> - goto out;
> - }
> - mptcp_set_timeout(sk);
> - }
> -
> - mptcp_push_release(ssk, &info);
> + do_check_data_fin = __subflow_push_pending(sk, ssk, &info);
do_check_data_fin is a bool, but __subflow_push_pending() returns an
int (the number of bytes copied). Looking at the other patches, the int
value is needed. I suggest assigning the int return value to an int
variable:
copied = __subflow_push_pending(sk, ssk, &info);
and updating the 'if' statement below...
> + release_sock(ssk);
> }
>
> -out:
> /* ensure the rtx timer is running */
> if (!mptcp_timer_pending(sk))
> mptcp_reset_timer(sk);
> if (do_check_data_fin)
> __mptcp_check_send_data_fin(sk);
...like this:
if (copied > 0)
__mptcp_check_send_data_fin(sk);
Thanks,
--
Mat Martineau
Intel