From: David Gibson <david@gibson.dropbear.id.au>
To: passt-dev@passt.top, Stefano Brivio <sbrivio@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Subject: [PATCH v2 03/11] tcp_splice: Don't handle EPOLL_CTL_DEL as part of tcp_splice_epoll_ctl()
Date: Tue, 7 Nov 2023 13:42:42 +1100 [thread overview]
Message-ID: <20231107024250.2290959-4-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20231107024250.2290959-1-david@gibson.dropbear.id.au>
tcp_splice_epoll_ctl() removes both sockets from the epoll set if called
when conn->flags & CLOSING. This will always happen immediately after
setting that flag, since conn_flag_do() makes the call itself. That's also
the _only_ time it can happen: we perform the EPOLL_CTL_DEL without
clearing the conn->in_epoll flag, meaning that any further calls to
tcp_splice_epoll_ctl() would attempt EPOLL_CTL_MOD, which would necessarily
fail since the fds are no longer in the epoll.
The EPOLL_CTL_DEL path in tcp_splice_epoll_ctl() has essentially zero
overlap with anything else the function does, so just move them to be
open coded in conn_flag_do().
This does require kernel 2.6.9 or later, in order to pass NULL as the
event structure for epoll_ctl(). However, we already require at least
3.13 to allow unprivileged user namespaces.
Given that, simply directly perform the EPOLL_CTL_DEL operations from
conn_flag_do() rather than unnecessarily multiplexini
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
tcp_splice.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/tcp_splice.c b/tcp_splice.c
index 6c4c664..570a8c6 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -152,8 +152,10 @@ static void conn_flag_do(const struct ctx *c, struct tcp_splice_conn *conn,
}
}
- if (flag == CLOSING)
- tcp_splice_epoll_ctl(c, conn);
+ if (flag == CLOSING) {
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->a, NULL);
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->b, NULL);
+ }
}
#define conn_flag(c, conn, flag) \
@@ -182,12 +184,6 @@ static int tcp_splice_epoll_ctl(const struct ctx *c,
struct epoll_event ev_b = { .data.u64 = ref_b.u64 };
uint32_t events_a, events_b;
- if (conn->flags & CLOSING) {
- epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->a, &ev_a);
- epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->b, &ev_b);
- return 0;
- }
-
tcp_splice_conn_epoll_events(conn->events, &events_a, &events_b);
ev_a.events = events_a;
ev_b.events = events_b;
--
@@ -152,8 +152,10 @@ static void conn_flag_do(const struct ctx *c, struct tcp_splice_conn *conn,
}
}
- if (flag == CLOSING)
- tcp_splice_epoll_ctl(c, conn);
+ if (flag == CLOSING) {
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->a, NULL);
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->b, NULL);
+ }
}
#define conn_flag(c, conn, flag) \
@@ -182,12 +184,6 @@ static int tcp_splice_epoll_ctl(const struct ctx *c,
struct epoll_event ev_b = { .data.u64 = ref_b.u64 };
uint32_t events_a, events_b;
- if (conn->flags & CLOSING) {
- epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->a, &ev_a);
- epoll_ctl(c->epollfd, EPOLL_CTL_DEL, conn->b, &ev_b);
- return 0;
- }
-
tcp_splice_conn_epoll_events(conn->events, &events_a, &events_b);
ev_a.events = events_a;
ev_b.events = events_b;
--
2.41.0
next prev parent reply other threads:[~2023-11-07 2:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-07 2:42 [PATCH v2 00/11] tcp_splice: Better exploit symmetry between sides of connection David Gibson
2023-11-07 2:42 ` [PATCH v2 01/11] tcp_splice: Remove redundant tcp_splice_epoll_ctl() David Gibson
2023-11-07 2:42 ` [PATCH v2 02/11] tcp_splice: Correct error handling in tcp_splice_epoll_ctl() David Gibson
2023-11-07 2:42 ` David Gibson [this message]
2023-11-07 2:42 ` [PATCH v2 04/11] tcp_splice: Remove unnecessary forward declaration David Gibson
2023-11-07 2:42 ` [PATCH v2 05/11] tcp_splice: Avoid awkward temporaries in tcp_splice_epoll_ctl() David Gibson
2023-11-07 2:42 ` [PATCH v2 06/11] tcp_splice: Don't pool pipes in pairs David Gibson
2023-11-07 2:42 ` [PATCH v2 07/11] tcp_splice: Rename sides of connection from a/b to 0/1 David Gibson
2023-11-07 2:42 ` [PATCH v2 08/11] tcp_splice: Exploit side symmetry in tcp_splice_timer() David Gibson
2023-11-07 2:42 ` [PATCH v2 09/11] tcp_splice: Exploit side symmetry in tcp_splice_connect_finish() David Gibson
2023-11-07 2:42 ` [PATCH v2 10/11] tcp_splice: Exploit side symmetry in tcp_splice_destroy() David Gibson
2023-11-07 2:42 ` [PATCH v2 11/11] tcp_splice: Simplify selection of socket and pipe sides in socket handler David Gibson
2023-11-07 12:45 ` [PATCH v2 00/11] tcp_splice: Better exploit symmetry between sides of connection Stefano Brivio
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