Re: [PATCH 03/11] tcp_splice: Don't handle EPOLL_CTL_DEL as part of tcp_splice_epoll_ctl()

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 12 Oct 2023 12:51:06 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> 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().
> 
> Caveat: this does require kernel 2.6.9 or later, in order to pass NULL as
> the event structure for epoll_ctl().  I _think_ we already require newer
> kernels than that for other features.

Yes, we do, we need at least 3.13 for unprivileged user namespaces.

-- 
Stefano