Date: Sat, 20 Dec 2014 08:58:52 +0900
From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ganesh Mahendran <opensource.ganesh@gmail.com>, ngupta@vflare.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/zsmalloc: add statistics support
Message-ID: <20141219235852.GB11975@blaptop>
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 <20141219143244.1e5fabad8b6733204486f5bc@linux-foundation.org>
 <20141219233937.GA11975@blaptop>
 <20141219154548.3aa4cc02b3322f926aa4c1d6@linux-foundation.org>
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On Fri, Dec 19, 2014 at 03:45:48PM -0800, Andrew Morton wrote:
> On Sat, 20 Dec 2014 08:39:37 +0900 Minchan Kim <minchan@kernel.org> wrote:
> 
> > Then, we should fix debugfs_create_dir can return errno to propagate the error
> > to end user who can know it was failed ENOMEM or EEXIST.
> 
> Impractical.  Every caller of every debugfs interface will need to be
> changed!

If you don't like changing of all of current caller, maybe, we can define
debugfs_create_dir_error and use it.

struct dentry *debugfs_create_dir_err(const char *name, struct dentry *parent, int *err)
and tweak debugfs_create_dir.
struct dentry *debugfs_create_dir(const char *name, struct dentry *parent, int *err)
{
	..
	..
	if (error) {
		*err = error;
		dentry = NULL;
	}
}

Why not?

> 
> It's really irritating and dumb.  What we're supposed to do is to
> optionally report the failure, then ignore it.  This patch appears to
> be OK in that respect.

At least, we should notify to the user why it was failed so he can fix
the name if it was duplicated. So if you don't want debugfs, at least
I want to warn all of reasons it can fail(at least, duplicated name)
to the user.

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