linux-kernel - Re: [PATCH] debugfs: ignore auto and noauto options if given

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Date: Wed, 5 Jun 2024 17:33:26 +0200
From: Christian Brauner <brauner@...nel.org>
To: Eric Sandeen <sandeen@...hat.com>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	linux-renesas-soc@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	David Howells <dhowells@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] debugfs: ignore auto and noauto options if given

On Mon, Jun 03, 2024 at 10:13:43AM -0500, Eric Sandeen wrote:
> On 6/3/24 9:33 AM, Christian Brauner wrote:
> > On Mon, Jun 03, 2024 at 09:17:10AM -0500, Eric Sandeen wrote:
> >> On 6/3/24 8:31 AM, Christian Brauner wrote:
> >>> On Mon, Jun 03, 2024 at 09:24:50AM +0200, Wolfram Sang wrote:
> >>>>
> >>>>>>> Does that fix it for you?
> >>>>>>
> >>>>>> Yes, it does, thank you.
> >>>>>>
> >>>>>> Reported-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> >>>>>> Tested-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> >>>>>
> >>>>> Thanks, applied. Should be fixed by end of the week.
> >>>>
> >>>> It is in -next but not in rc2. rc3 then?
> >>>
> >>> Yes, it wasn't ready when I sent the fixes for -rc2 as I just put it in
> >>> that day.
> >>>
> >>
> >> See my other reply, are you sure we should make this change? From a
> >> "keep the old behavior" POV maybe so, but this looks to me like a
> >> bug in busybox, passing fstab hint "options" like "auto" as actual mount
> >> options being the root cause of the problem. debugfs isn't uniquely
> >> affected by this behavior.
> >>
> >> I'm not dead set against the change, just wanted to point this out.
> > 
> > Hm, it seems I forgot your other mail, sorry.
> 
> No worries!
> 
> > So the issue is that we're breaking existing userspace and it doesn't
> > seem like a situation where we can just ignore broken userspace. If
> > busybox has been doing that for a long time we might just have to
> > accommodate their brokenness. Thoughts?
> 
> Yep, I can totally see that POV.
> 
> It's just that surely every other strict-parsing filesystem is also
> broken in this same way, so coding around the busybox bug only in debugfs
> seems a little strange. (Surely we won't change every filesystem to accept
> unknown options just for busybox's benefit.)
> 
> IOWS: why do we accomodate busybox brokenness only for debugfs, given that
> "auto" can be used in fstab for any filesystem?

I suspect that not that most filesystems aren't mounted from fstab which
is why we've never saw reports.