linux-kernel - Re: [PATCH] sysfs: Optionally count subdirectories to support buggy applications

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Date:	Wed, 1 Feb 2012 14:24:41 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Jiri Slaby <jslaby@...e.cz>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>
Subject: Re: [PATCH] sysfs:  Optionally count subdirectories to support buggy
 applications

On Wed, Feb 01, 2012 at 02:21:59PM -0800, Eric W. Biederman wrote:
> 
> lm_sensors and possibly other applications get confused if all sysfs
> directories return nlink == 1.  The lm_sensors code that got confused
> was just wrong and a fixed version of lm_sensors should be released
> shortly.
> 
> There may be other applications that have problems with sysfs return
> nlink == 1 for directories.  To allow people to continue to use old
> versions of userspace with new kernels add to sysfs a compile time
> option to maintain mostly precise directory counts for those people who
> don't mind the cost.
> 
> I have moved where we keep nlink in sysfs_dirent as compared to previous
> versions of subdirectory counting to a location that packs better.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> ---
>  fs/sysfs/Kconfig |   15 +++++++++++++++
>  fs/sysfs/dir.c   |    8 ++++++++
>  fs/sysfs/inode.c |    2 ++
>  fs/sysfs/sysfs.h |   38 ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/sysfs/Kconfig b/fs/sysfs/Kconfig
> index 8c41fea..9b403e9 100644
> --- a/fs/sysfs/Kconfig
> +++ b/fs/sysfs/Kconfig
> @@ -21,3 +21,18 @@ config SYSFS
>  	example, "root=03:01" for /dev/hda1.
>  
>  	Designers of embedded systems may wish to say N here to conserve space.
> +
> +config SYSFS_COUNT_LINKS
> +	bool "sysfs count subdirectoires to support buggy applications"
> +	default n

As we don't want to break things, this should be default y, right?

Also, should we list this in the feature_removal list as well so that we
can get rid of it in a year or so?

thanks,

greg k-h
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