linux-kernel - Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories.

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Date:	Tue, 12 Jan 2010 13:41:34 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	Serge Hallyn <serue@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories.

On Mon, 11 Jan 2010 12:21:51 -0800,
"Eric W. Biederman" <ebiederm@...ssion.com> wrote:

> From: Eric W. Biederman <ebiederm@...stanetworks.com>
> 
> On large directories sysfs_count_nlinks can be a significant
> bottleneck, so keep a count in sysfs_dirent.  If we exceed
> the maximum number of directory entries we can store return
> nlink of 1.  An nlink of 1 matches what reiserfs does in
> this case, and it let's find and similar utlities know that
> we have a the directory nlink can not be used for optimization
> purposes.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
> ---
>  fs/sysfs/dir.c   |   20 ++++++++++++++++++++
>  fs/sysfs/inode.c |   15 +--------------
>  fs/sysfs/mount.c |    1 +
>  fs/sysfs/sysfs.h |    1 +
>  4 files changed, 23 insertions(+), 14 deletions(-)
> 

> @@ -420,6 +438,7 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
>  		return -EEXIST;
> 
>  	sd->s_parent = sysfs_get(acxt->parent_sd);
> +	sysfs_dir_inc_nlink(sd->s_parent);
> 
>  	sysfs_link_sibling(sd);
> 
> @@ -512,6 +531,7 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
> 
>  	BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);
> 
> +	sysfs_dir_dec_nlink(sd->s_parent);
>  	sysfs_unlink_sibling(sd);
> 
>  	/* Update timestamps on the parent */

Shouldn't s_nlink be adjusted in sysfs_rename for the move case as well?
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