linux-kernel - Re: Q. DEBUG_FS and SYSFS config (Re: [RFC Aufs2 #3 2/2] split 'xino' entry under sysfs)

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Message-ID: <20090324153329.GA13705@kroah.com>
Date:	Tue, 24 Mar 2009 08:33:29 -0700
From:	Greg KH <greg@...ah.com>
To:	hooanon05@...oo.co.jp
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Q. DEBUG_FS and SYSFS config (Re: [RFC Aufs2 #3 2/2] split
	'xino' entry under sysfs)

On Tue, Mar 24, 2009 at 05:16:40PM +0900, hooanon05@...oo.co.jp wrote:
> 
> Greg KH:
> > No one disables sysfs that I know of.  Heck, my phone enables sysfs...
> > 
> > > Addition to set limit, there is one more reason to adopt seq_file.
> > > Because the printed string is a path, it may contain unprintable
> > > characters. seq_file has a good interface seq_path() which supports
> > > escaping such characters.
> > 
> > That is true.  Ok, let's see the final result and I'll be glad to look
> > at it.
> 
> Hi Greg,
> 
> Currently I am testing locally about new aufs entries under debugfs, and
> I found a strange issue about configuration.
> 
> First, configure "normaly".
> General setup
>   [ ] Configure standard kernel features (for small systems)  --->
> 
> $ egrep -i '(sysfs|debug_fs)' .config
> CONFIG_SYSFS_DEPRECATED=y
> CONFIG_SYSFS_DEPRECATED_V2=y

You should disable those two options, no modern distro needs them
anymore.

> CONFIG_SYSFS=y
> CONFIG_DEBUG_FS=y
> # CONFIG_FAULT_INJECTION_DEBUG_FS is not set
> 
> Next, enable EMBEDED, and then disable SYSFS.
> General setup
>   [*] Configure standard kernel features (for small systems)  --->
> File systems
>   Pseudo filesystems  --->
>     [ ] sysfs file system support
> 
> $ egrep -i '(sysfs|debug_fs)' .config
> # CONFIG_SYSFS is not set
> CONFIG_DEBUG_FS=y
> 
> SYSFS is disabled expectedly, but DEBUG_FS is still enabled,
> while "depends on SYSFS" is specified for DEBUG_FS.
> 
> Is this expected behaviour?
> In other words, can I assume "when DEBUG_FS is enabled, SYSFS must be
> enabled too" safely?

Your code should not worry about either of these, it will "just work"
either way.

As for if there is a bug here, I don't know, the kbuild dependancies
should fix it up if you run "make oldconfig" right?

thanks,

greg k-h
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