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Date: Tue, 10 Dec 2013 00:19:22 -0800
From: Greg KH <gregkh@linuxfoundation.org>
To: Ethan Zhao <ethan.kernel@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        raghavendra.kt@linux.vnet.ibm.com, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] xen/debugfs: Check debugfs initialization before using it
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On Tue, Dec 10, 2013 at 04:03:41PM +0800, Ethan Zhao wrote:
> On Tue, Dec 10, 2013 at 2:40 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Mon, Dec 09, 2013 at 09:42:23PM +0800, Ethan Zhao wrote:
> >> Greg,
> >>     I am the man who built a Xen dom0, but couldn't see debugfs
> >> directory and files as expected. there is no warning or tip for me to
> >> enable the CONFIG_DEBUG_FS=y in .config , it cost me minutes to figure
> >> out what's
> >> the matter. and I know should check defugfs config and initialization as
> >> zswap_debugfs, tracer_debugfs ,rproc_debugfs did. Is it useless ? if
> >> it could save me just 1 minute next time ?
> >
> > So you would want a "warning" showing up for every single part of the
> > kernel that uses debugfs for when it isn't enabled?  That doesn't make
> > too much sense now, does it?
> 
> No, It is nice and like sun light when someone is struggling with the
> bugs in darkness,
> if some tips or warning output to them.
> 
> You have forgotten the initial stage you met :)

So, you really want to see 20+ KERNEL WARNINGS in your system when you
boot without CONFIG_DEBUGFS enabled?  No, that's not ok at all, sorry,
that is not going to happen.

Running a kernel without debugfs is a valid state, you are treating it
as an error, which isn't ok.

greg k-h