linux-kernel - Re: [RFC][PATCH] tracing: Deprecate auto-mounting tracefs in debugfs

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Message-ID: <3201A571-6F08-4E26-AC33-39E0D1925D27@goodmis.org>
Date: Tue, 17 Jun 2025 13:54:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
CC: LKML <linux-kernel@...r.kernel.org>,
 Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
 "linux-trace-users@...r.kernel.org" <linux-trace-users@...r.kernel.org>,
 linux-fsdevel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Mark Rutland <mark.rutland@....com>, Thomas Gleixner <tglx@...utronix.de>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Namhyung Kim <namhyung@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Al Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>,
 Jan Kara <jack@...e.cz>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Frederic Weisbecker <fweisbec@...il.com>, Jiri Olsa <jolsa@...nel.org>,
 Ian Rogers <irogers@...gle.com>
Subject: Re: [RFC][PATCH] tracing: Deprecate auto-mounting tracefs in debugfs



On June 17, 2025 1:41:07 PM EDT, Peter Zijlstra <peterz@...radead.org> wrote:
>On Tue, Jun 17, 2025 at 01:36:14PM -0400, Steven Rostedt wrote:
>> From: Steven Rostedt <rostedt@...dmis.org>
>> 
>> In January 2015, tracefs was created to allow access to the tracing
>> infrastructure without needing to compile in debugfs. When tracefs is
>> configured, the directory /sys/kernel/tracing will exist and tooling is
>> expected to use that path to access the tracing infrastructure.
>> 
>> To allow backward compatibility, when debugfs is mounted, it would
>> automount tracefs in its "tracing" directory so that tooling that had hard
>> coded /sys/kernel/debug/tracing would still work.
>> 
>> It has been over 10 years since the new interface was introduced, and all
>> tooling should now be using it. Start the process of deprecating the old
>> path so that it doesn't need to be maintained anymore.
>
>I've always used /debug/tracing/ (because /debug is the right place to
>mount debugfs). You're saying this is going away and will break all my
>scripts?!

You could mount tracefs in /tracing too:

  # mount -t tracefs nodev /tracing 

And update you scripts with a simple sed script.

-- Steve