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tcp_splice: Don't handle EPOLL_CTL_DEL as part of tcp_splice_epoll_ctl()

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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>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-11-07 13:42:42 +11:00 committed by Stefano Brivio
parent 536acab2de
commit 5a79ba6272
1 changed files with 4 additions and 8 deletions
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12
tcp_splice.c
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@ -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;