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From: Quentin Monnet <qmo@kernel.org>
Subject: Re: bpftool uses wrong order of tracefs search
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
 bpf <bpf@vger.kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
 Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau
 <martin.lau@kernel.org>, Steven Rostedt <rostedt@goodmis.org>
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2025-09-11 10:27 UTC-0700 ~ Alexei Starovoitov
<alexei.starovoitov@gmail.com>
> Hi Quentin,
> 
> since last merge window bpftool triggers a warn:
> $ bpftool prog tracelog
> [   72.942082] NOTICE: Automounting of tracing to debugfs is
> deprecated and will be removed in 2030
> 
> 
> I suspect it happens because get_tracefs_pipe()
> accesses debug/tracing first which causes automnount
> and triggers this warning.
> 
> Pls take a look.


Hi Alexei, sure, I'll look into it.

I haven't tested yet, but the check on /sys/kernel/debug/tracing is
likely to be the cause indeed. If that's the case, would that be OK to
move it to the end of the "known_mnts" list in the function? Or do you
prefer to avoid the warning completely, even at the cost of missing the
tracefs on older systems?

Quentin