From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Jiri Olsa <jolsa@redhat.com>,
Eelco Chaudron <echaudro@redhat.com>,
KP Singh <kpsingh@chromium.org>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v8 04/11] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach
Date: Fri, 25 Sep 2020 08:45:04 -0700 [thread overview]
Message-ID: <CAADnVQLMBKAYsbS4PO87yVrPWJEf9H3qzpsL-p+gFQpcomDw2w@mail.gmail.com> (raw)
In-Reply-To: <87tuvmbztw.fsf@toke.dk>
On Thu, Sep 24, 2020 at 3:00 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> >> + struct mutex tgt_mutex; /* protects tgt_* pointers below, *after* prog becomes visible */
> >> + struct bpf_prog *tgt_prog;
> >> + struct bpf_trampoline *tgt_trampoline;
> >> bool verifier_zext; /* Zero extensions has been inserted by verifier. */
> >> bool offload_requested;
> >> bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */
> > ...
> >> struct bpf_tracing_link {
> >> struct bpf_link link;
> >> enum bpf_attach_type attach_type;
> >> + struct bpf_trampoline *trampoline;
> >> + struct bpf_prog *tgt_prog;
> >
> > imo it's confusing to have 'tgt_prog' to mean two different things.
> > In prog->aux->tgt_prog it means target prog to attach to in the future.
> > Whereas here it means the existing prog that was used to attached to.
> > They kinda both 'target progs' but would be good to disambiguate.
> > May be keep it as 'tgt_prog' here and
> > rename to 'dest_prog' and 'dest_trampoline' in prog->aux ?
>
> I started changing this as you suggested, but I think it actually makes
> the code weirder. We'll end up with a lot of 'tgt_prog =
> prog->aux->dest_prog' assignments in the verifier, unless we also rename
> all of the local variables, which I think is just code churn for very
> little gain (the existing 'target' meaning is quite clear, I think).
you mean "churn" just for this patch. that's fine.
But it will make names more accurate for everyone reading it afterwards.
Hence I prefer distinct and specific names where possible.
> I also think it's quite natural that the target moves; I mean, it's
> literally the same pointer being re-assigned from prog->aux to the link.
> We could rename the link member to 'attached_tgt_prog' or something like
> that, but I'm not sure it helps (and I don't see much of a problem in
> the first place).
'attached_tgt_prog' will not be the correct name.
There is 'prog' inside the link already. That's 'attached' prog.
Not this one. This one is the 'attached_to' prog.
But such name would be too long.
imo calling it 'dest_prog' in aux is shorter and more obvious.
next prev parent reply other threads:[~2020-09-25 15:45 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 18:38 [PATCH bpf-next v8 00/11] bpf: Support multi-attach for freplace programs Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 01/11] bpf: disallow attaching modify_return tracing functions to other BPF programs Toke Høiland-Jørgensen
2020-09-23 17:25 ` Andrii Nakryiko
2020-09-22 18:38 ` [PATCH bpf-next v8 02/11] bpf: change logging calls from verbose() to bpf_log() and use log pointer Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 03/11] bpf: verifier: refactor check_attach_btf_id() Toke Høiland-Jørgensen
2020-09-23 23:54 ` Alexei Starovoitov
2020-09-22 18:38 ` [PATCH bpf-next v8 04/11] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach Toke Høiland-Jørgensen
2020-09-24 0:14 ` Alexei Starovoitov
2020-09-24 14:34 ` Toke Høiland-Jørgensen
2020-09-24 15:43 ` Alexei Starovoitov
2020-09-24 21:30 ` Toke Høiland-Jørgensen
2020-09-24 20:40 ` Andrii Nakryiko
2020-09-24 21:24 ` Toke Høiland-Jørgensen
2020-09-24 21:59 ` Andrii Nakryiko
2020-09-24 22:20 ` Toke Høiland-Jørgensen
2020-09-24 22:37 ` Andrii Nakryiko
2020-09-24 23:13 ` Toke Høiland-Jørgensen
2020-09-24 21:59 ` Toke Høiland-Jørgensen
2020-09-25 15:45 ` Alexei Starovoitov [this message]
2020-09-25 20:57 ` Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 05/11] bpf: support attaching freplace programs to multiple attach points Toke Høiland-Jørgensen
2020-09-24 1:04 ` Alexei Starovoitov
2020-09-22 18:38 ` [PATCH bpf-next v8 06/11] bpf: Fix context type resolving for extension programs Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 07/11] libbpf: add support for freplace attachment in bpf_link_create Toke Høiland-Jørgensen
2020-09-23 17:28 ` Andrii Nakryiko
2020-09-23 20:58 ` Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 08/11] selftests: add test for multiple attachments of freplace program Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 09/11] selftests/bpf: Adding test for arg dereference in extension trace Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 10/11] selftests: Add selftest for disallowing modify_return attachment to freplace Toke Høiland-Jørgensen
2020-09-22 18:38 ` [PATCH bpf-next v8 11/11] selftests: Remove fmod_ret from benchmarks and test_overhead Toke Høiland-Jørgensen
2020-09-23 17:40 ` Andrii Nakryiko
2020-09-24 1:08 ` Alexei Starovoitov
2020-09-24 1:38 ` Andrii Nakryiko
2020-09-24 23:19 ` Toke Høiland-Jørgensen
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