linux-kernel - Re: [for-next][PATCH 5/7] tracing: Automatically mount tracefs on debugfs/tracing

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Date:	Mon, 9 Feb 2015 10:06:26 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [for-next][PATCH 5/7] tracing: Automatically mount tracefs on
 debugfs/tracing

On Mon, 9 Feb 2015 15:00:02 +0900
Namhyung Kim <namhyung@...nel.org> wrote:

> On Wed, Feb 04, 2015 at 09:34:25AM -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> > 
> > As tools currently rely on the tracing directory in debugfs, we can not
> > just created a tracefs infrastructure and expect sysadmins to mount
> > the new tracefs to have their old tools work.
> > 
> > Instead, the debugfs tracing directory is still created and the tracefs
> > file system is mounted there when the debugfs filesystem is mounted.
> > 
> > No longer does the tracing infrastructure update the debugfs file system,
> > but instead interacts with the tracefs file system. But now, it still
> > appears to the user like nothing changed, except you also have the feature
> > of mounting just the tracing system without needing all of debugfs!
> 
> One question.  Is it possible to have both of the old
> /sys/kernel/debug/tracing and new /sys/kernel/tracing directories?

Yes. In fact it's required. Because we must stay backward compatible
with older tools, we can not get rid of the debug/tracing directory.


> > +	/*
> > +	 * As there may still be users that expect the tracing
> > +	 * files to exist in debugfs/tracing, we must automount
> > +	 * the tracefs file system there, so older tools still
> > +	 * work with the newer kerenl.
> 
> s/kerenl/kernel/

Thanks, will fix.

-- Steve

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