From: Roman Gushchin <roman.gushchin@linux.dev>
To: Matt Bobrowski <mattbobrowski@google.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
ohn Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>,
Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH bpf-next] bpf: Revert "bpf: drop KF_ACQUIRE flag on BPF kfunc bpf_get_root_mem_cgroup()"
Date: Wed, 21 Jan 2026 10:47:57 -0800 [thread overview]
Message-ID: <87o6mm7qg2.fsf@linux.dev> (raw)
In-Reply-To: <20260121090001.240166-1-mattbobrowski@google.com> (Matt Bobrowski's message of "Wed, 21 Jan 2026 09:00:01 +0000")
Matt Bobrowski <mattbobrowski@google.com> writes:
> This reverts commit e463b6de9da1 ("bpf: drop KF_ACQUIRE flag on BPF
> kfunc bpf_get_root_mem_cgroup()").
>
> The original commit removed the KF_ACQUIRE flag from
> bpf_get_root_mem_cgroup() under the assumption that it resulted in
> simplified usage. This stemmed from the fact that
> bpf_get_root_mem_cgroup() inherently returns a reference to an object
> which technically isn't reference counted, therefore there is no
> strong requirement to call a matching bpf_put_mem_cgroup() on the
> returned reference.
>
> Although technically correct, as per the arguments in the thread [0],
> dropping the KF_ACQUIRE flag and losing reference tracking semantics
> negatively impacted the usability of bpf_get_root_mem_cgroup() in
> practice.
>
> [0] https://lore.kernel.org/bpf/878qdx6yut.fsf@linux.dev/
>
> Link: https://lore.kernel.org/bpf/CAADnVQ+6d1Lj4dteAv8u62d7kj3Ze5io6bqM0xeQd-UPk9ZgJQ@mail.gmail.com/
> Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Thanks, Matt!
prev parent reply other threads:[~2026-01-21 18:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-21 9:00 [PATCH bpf-next] bpf: Revert "bpf: drop KF_ACQUIRE flag on BPF kfunc bpf_get_root_mem_cgroup()" Matt Bobrowski
2026-01-21 17:50 ` patchwork-bot+netdevbpf
2026-01-21 18:47 ` Roman Gushchin [this message]
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