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

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Message-ID: <4F29BE2F.2000907@suse.cz>
Date:	Wed, 01 Feb 2012 23:35:27 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Greg KH <greg@...ah.com>, 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 02/01/2012 11:21 PM, Eric W. Biederman wrote:
> --- 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
> +	help
> +
> +	Increase the memory and cpu untilization of sysfs by maintaining
> +	by maintaining a count of how hard links from subdirectories a

by maintaining only once.

of how "many"?

> +	directory has.  This allows sysfs to report the directory nlink
> +	as the number of subdirectories plus two.  With out this enabled
> +	sysfs will report the nlink of all directories as 1, which is
> +	the standard way of indicating that the number of subdirectoires
> +	is not tracked.
> +
> +	Unless you know you need this say N here.

You should put the opposite here. "If you are sure you don't need it,
say N."

> --- a/fs/sysfs/sysfs.h
> +++ b/fs/sysfs/sysfs.h
...
> @@ -127,6 +130,41 @@ do {								\
>  #define sysfs_dirent_init_lockdep(sd) do {} while(0)
>  #endif
>  
> +#ifdef CONFIG_SYSFS_COUNT_LINKS
> +static inline void sysfs_init_nlink(struct sysfs_dirent *sd)
> +{
> +	if (sysfs_type(sd) == SYSFS_DIR)
> +		sd->s_nlink = 2;
> +	else
> +		sd->s_nlink = 1;
> +}
> +static inline void sysfs_inc_nlink(struct sysfs_dirent *sd)
> +{
> +	sd->s_nlink++;
> +}
> +static inline void sysfs_dec_nlink(struct sysfs_dirent *sd)
> +{
> +	sd->s_nlink++;
> +}

Minus minus.

thanks,
-- 
js
suse labs
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