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([2620:10d:c090:500::2:8a9]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30294adddaasm768297eec.13.2026.05.13.15.35.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 15:35:08 -0700 (PDT) Message-ID: <237f26933259d2a9114b4abd9cd7773b788c2038.camel@gmail.com> Subject: Re: [PATCH RESEND bpf-next v10 5/8] bpf: Add bpf_list_add to insert node after a given list node From: Eduard Zingerman To: Kaitao cheng , ast@kernel.org, corbet@lwn.net, martin.lau@linux.dev, daniel@iogearbox.net, andrii@kernel.org, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, skhan@linuxfoundation.org, memxor@gmail.com Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, vmalik@redhat.com, linux-kselftest@vger.kernel.org Date: Wed, 13 May 2026 15:35:06 -0700 In-Reply-To: <20260512055919.95716-6-kaitao.cheng@linux.dev> References: <20260512055919.95716-1-kaitao.cheng@linux.dev> <20260512055919.95716-6-kaitao.cheng@linux.dev> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-05-12 at 13:59 +0800, Kaitao cheng wrote: > From: Kaitao Cheng >=20 > Add a new kfunc bpf_list_add(head, new, prev, meta, off) that > inserts 'new' after 'prev' in the BPF linked list. Both must be in > the same list; 'prev' must already be in the list. The new node must > be an owning reference (e.g. from bpf_obj_new); the kfunc consumes > that reference and the node becomes non-owning once inserted. >=20 > We have added an additional parameter bpf_list_head *head to > bpf_list_add, as the verifier requires the head parameter to > check whether the lock is being held. >=20 > Returns 0 on success, -EINVAL if 'prev' is not in a list or 'new' > is already in a list (or duplicate insertion). On failure, the > kernel drops the passed-in node. >=20 > Signed-off-by: Kaitao Cheng > --- Reviewed-by: Eduard Zingerman [...] > @@ -19228,8 +19231,11 @@ int bpf_fixup_kfunc_call(struct bpf_verifier_env= *env, struct bpf_insn *insn, > int struct_meta_reg =3D BPF_REG_3; > int node_offset_reg =3D BPF_REG_4; > =20 > - /* rbtree_add has extra 'less' arg, so args-to-fixup are in diff regs = */ > - if (is_bpf_rbtree_add_kfunc(desc->func_id)) { > + /* list_add/rbtree_add have an extra arg (prev/less), > + * so args-to-fixup are in diff regs. > + */ > + if (desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_add] || Nit: same nit here, maybe add is_bpf_list_add_kfunc(). > + is_bpf_rbtree_add_kfunc(desc->func_id)) { > struct_meta_reg =3D BPF_REG_4; > node_offset_reg =3D BPF_REG_5; > }