linux-kernel - Re: [PATCH] mm/memblock: validate the creation of debugfs files

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Message-Id: <20150815003830.c87afaff.akpm@linux-foundation.org>
Date:	Sat, 15 Aug 2015 00:38:30 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alexander Kuleshov <kuleshovmail@...il.com>
Cc:	Tony Luck <tony.luck@...el.com>, Pekka Enberg <penberg@...nel.org>,
	Mel Gorman <mgorman@...e.de>, Baoquan He <bhe@...hat.com>,
	Tang Chen <tangchen@...fujitsu.com>, Robin Holt <holt@....com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] mm/memblock: validate the creation of debugfs files

On Sat, 15 Aug 2015 13:26:36 +0600 Alexander Kuleshov <kuleshovmail@...il.com> wrote:

> Hello Andrew,
> 
> On 08-14-15, Andrew Morton wrote:
> > On Sat, 15 Aug 2015 01:03:31 +0600 Alexander Kuleshov <kuleshovmail@...il.com> wrote:
> > 
> > > Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> > 
> > There's no changelog.
> 
> Yes, will add it if there will be sense in the patch.
> 
> > 
> > Why?  Ignoring the debugfs API return values is standard practice.
> > 
> 
> Yes, but I saw many places where this practice is applicable (for example
> in the kernel/kprobes and etc.), besides this, the memblock API is used
> mostly at early stage, so we will have some output if something going wrong.

The debugfs error-handling rules are something Greg cooked up after one
too many beers.  I've never understood them, but maybe I continue to
miss the point.

Yes, I agree that if memblock's debugfs_create_file() fails, we want to
know about it because something needs fixing.  But that's true of
all(?) debugfs_create_file callsites, so it's a bit silly to add
warnings to them all.  Why not put the warning into
debugfs_create_file() itself?  And add a debugfs_create_file_no_warn()
if there are callsites which have reason to go it alone.  Or add a
debugfs_create_file_warn() wrapper.
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