On Fri, Dec 19, 2025 at 05:45:14PM +0100, Laurent Vivier wrote:
The function tcp_splice_conn_epoll_events() currently takes an array of struct epoll_event and fills in the .events field for both sides using flow_foreach_sidei() loops.
This works, but the function is doing two conceptually separate things at once: computing events for side 0 and computing events for side 1. The OUT_WAIT handling is particularly subtle, as it has cross-side effects: when OUT_WAIT(sidei) is set, we add EPOLLOUT to ev[sidei] but also remove EPOLLIN from ev[!sidei].
Refactor to make the function compute events for a single side at a time, taking sidei as a parameter and returning uint32_t. This makes the logic more focused and easier to follow. The cross-side effects of OUT_WAIT are preserved by checking both OUT_WAIT(sidei) and OUT_WAIT(!sidei) within each call.
The caller tcp_splice_epoll_ctl() now invokes the function twice, once for each side, making the two-sided nature of the operation explicit.
No functional change.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
--- tcp_splice.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-)
diff --git a/tcp_splice.c b/tcp_splice.c index 440522449c13..bf4ff466de07 100644 --- a/tcp_splice.c +++ b/tcp_splice.c @@ -114,29 +114,23 @@ static struct tcp_splice_conn *conn_at_sidx(flow_sidx_t sidx) * @events: Connection event flags * @ev: Events to fill in, 0 is accepted socket, 1 is connecting socket */ -static void tcp_splice_conn_epoll_events(uint16_t events, - struct epoll_event ev[]) +static uint32_t tcp_splice_conn_epoll_events(uint16_t events, unsigned sidei) { - unsigned sidei; - - flow_foreach_sidei(sidei) - ev[sidei].events = 0; + uint32_t e = 0;
if (events & SPLICE_ESTABLISHED) { - flow_foreach_sidei(sidei) { - if (!(events & FIN_SENT(!sidei))) - ev[sidei].events = EPOLLIN | EPOLLRDHUP; - } - } else if (events & SPLICE_CONNECT) { - ev[1].events = EPOLLOUT; + if (!(events & FIN_SENT(!sidei))) + e = EPOLLIN | EPOLLRDHUP; + } else if (sidei == 1 && events & SPLICE_CONNECT) { + e = EPOLLOUT; }
- flow_foreach_sidei(sidei) { - if (events & OUT_WAIT(sidei)) { - ev[sidei].events |= EPOLLOUT; - ev[!sidei].events &= ~EPOLLIN; - } - } + if (events & OUT_WAIT(sidei)) + e |= EPOLLOUT; + if (events & OUT_WAIT(!sidei)) + e &= ~EPOLLIN; + + return e; }
/** @@ -161,7 +155,8 @@ static int tcp_splice_epoll_ctl(const struct ctx *c, struct epoll_event ev[SIDES] = { { .data.u64 = ref[0].u64 }, { .data.u64 = ref[1].u64 } };
- tcp_splice_conn_epoll_events(conn->events, ev); + ev[0].events = tcp_splice_conn_epoll_events(conn->events, 0); + ev[1].events = tcp_splice_conn_epoll_events(conn->events, 1);
if (epoll_ctl(epollfd, m, conn->s[0], &ev[0]) || -- 2.51.1
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson