[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <YxkS5uzouv2bn6ZB@google.com>
Date: Wed, 7 Sep 2022 14:53:42 -0700
From: Brian Norris <briannorris@...omium.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] tracefs: Only clobber mode/uid/gid on remount if
asked
On Wed, Sep 07, 2022 at 05:48:13PM -0400, Steven Rostedt wrote:
> On Wed, 7 Sep 2022 17:46:04 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
> > > # Don't change /sys/kernel/tracing/ permissions on automount.
> > > umount /sys/kernel/debug/tracing/
> >
> > BTW, I noticed that the above doesn't do anything. That is,
> > you cannot unmount tracefs from /sys/kernel/debug/tracing.
Actually, it does work, but it's hard to observe. See below.
> I just saw your new email. I guess that's just how you were triggering the
> automount, by unmounting it. Right?
You trimmed the important line:
stat /sys/kernel/debug/tracing/.
It's hard to observe directly that /sys/kernel/debug/tracing is
unmounted, because traditional examination (stat(2), open(2), etc.)
methods will re-trigger the automount. The automount is *supposed* to
appear as if it is always there.
Try these:
umount /sys/kernel/debug/tracing/
grep tracefs /proc/mounts
stat /sys/kernel/debug/tracing/.
grep tracefs /proc/mounts
The first and the second grep will give you different results.
> A lot of assumptions about what people may know ;-)
Yes, I suppose. That's also why I figured I'd write a test case, because
test cases tell you exactly what is meant.
Brian
Powered by blists - more mailing lists