From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Ihor Solodrai <ihor.solodrai@linux.dev>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next 1/4] libbpf: Add bpf_program__add_flags() and bpf_program__clear_flags()
Date: Thu, 10 Sep 2026 11:00:37 +0200 [thread overview]
Message-ID: <87jyoteb0q.fsf@toke.dk> (raw)
In-Reply-To: <261c5e00-31d8-4090-aab4-a633924d336c@linux.dev>
Ihor Solodrai <ihor.solodrai@linux.dev> writes:
> On 9/3/26 2:24 AM, Toke Høiland-Jørgensen wrote:
>> When changing BPF program flags, applications often need to just add or
>> remove a single flag. The bpf_program__set_flags() function clobbers any
>> existing flags value, making this awkward to do non-destructively.
>
> I think the whole "non-destructively" language in the series is misleading.
>
> bpf_program__add_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY);
>
> does exactly the same thing as
>
> bpf_program__set_flags(prog, bpf_program__flags(prog) | BPF_F_XDP_DEV_BOUND_ONLY);
>
> That is: overwriting the prog->prog_flags value. Where is the
> non-destructiveness?
bpf_program__add_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY) doesn't overwrite
any existing flag values, but bpf_program__set_flags(prog,
BPF_F_XDP_DEV_BOUND_ONLY) does. In your example you handle this in the
caller, but you have to take pains to do that (which, judging from the
fixups I had to do earlier, was not something everyone did :)).
However,
> Let's call this for what it is: a convenience API.
I don't mind changing the description - will respin with this change.
Thanks for reviewing!
-Toke
next prev parent reply other threads:[~2026-09-10 9:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 9:24 [PATCH bpf-next 1/4] libbpf: Add bpf_program__add_flags() and bpf_program__clear_flags() Toke Høiland-Jørgensen
2026-09-03 9:24 ` [PATCH bpf-next 2/4] selftests/bpf: Add assertions for bpf_program__{add,clear}_flags() Toke Høiland-Jørgensen
2026-09-03 9:32 ` sashiko-bot
2026-09-03 9:24 ` [PATCH bpf-next 3/4] selftests/bpf: Adopt bpf_program__add_flags() helper Toke Høiland-Jørgensen
2026-09-03 9:24 ` [PATCH bpf-next 4/4] bpftool: " Toke Høiland-Jørgensen
2026-09-07 15:24 ` Quentin Monnet
2026-09-03 9:30 ` [PATCH bpf-next 1/4] libbpf: Add bpf_program__add_flags() and bpf_program__clear_flags() sashiko-bot
2026-09-09 19:04 ` Ihor Solodrai
2026-09-10 9:00 ` Toke Høiland-Jørgensen [this message]
2026-09-10 16:07 ` Ihor Solodrai
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