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Sun, 22 Feb 2026 06:35:09 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Sun, 22 Feb 2026 15:35:07 +0100 To: bot+bpf-ci@kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kafai@fb.com, eddyz87@gmail.com, songliubraving@fb.com, yhs@fb.com, menglong8.dong@gmail.com, rostedt@kernel.org, martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCH bpf-next 08/17] bpf: Add support for tracing multi link Message-ID: References: <20260220100649.628307-9-jolsa@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Feb 20, 2026 at 10:57:58AM +0000, bot+bpf-ci@kernel.org wrote: > > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h > > --- a/include/linux/bpf_types.h > > +++ b/include/linux/bpf_types.h > > [ ... ] > > > +BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING_MULTI, tracing) > > The existing BPF_LINK_TYPE_TRACING also uses "tracing" as its name > argument: > > BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing) > > This means bpf_link_type_strs[] will contain "tracing" for both > BPF_LINK_TYPE_TRACING and BPF_LINK_TYPE_TRACING_MULTI, making them > indistinguishable in fdinfo output via bpf_link_show_fdinfo(). > > The libbpf side correctly uses "tracing_multi": > > [BPF_LINK_TYPE_TRACING_MULTI] = "tracing_multi", > > Should this be BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING_MULTI, tracing_multi) > to match? it should, fixed > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > [ ... ] > > > +int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr) > > +{ > > [ ... ] > > > + ids = kvmalloc_array(cnt, sizeof(*ids), GFP_KERNEL); > > [ ... ] > > > + link = kzalloc(struct_size(link, nodes, cnt), GFP_KERNEL); > ^^^^^^ > > The ids array above uses kvmalloc_array() to handle large allocations, > but the link struct uses kzalloc(). With MAX_TRACING_MULTI_CNT at 1M > and each bpf_tracing_multi_node being roughly 40 bytes, > struct_size() can request up to ~40MB of contiguous memory. kzalloc() > is limited to KMALLOC_MAX_SIZE (~4MB on x86_64), so this will fail > for cnt values above roughly 100K. > > Would kvzalloc() work here instead? bpf_tracing_multi_link_dealloc() > would need to use kvfree() accordingly: > > > +static void bpf_tracing_multi_link_dealloc(struct bpf_link *link) > > +{ > > + struct bpf_tracing_multi_link *tr_link = > > + container_of(link, struct bpf_tracing_multi_link, link); > > + > > + kfree(tr_link); yes, makes sense, will fix, thnx jirka