linux-kernel - Re: [PATCH 10/13] sysfs: In sysfs_chmod_file lazily propagate the mode change.

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Message-ID: <20091104042345.GF27639@us.ibm.com>
Date:	Tue, 3 Nov 2009 22:23:45 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 10/13] sysfs: In sysfs_chmod_file lazily propagate the
	mode change.

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> From: Eric W. Biederman <ebiederm@...ssion.com>
> 
> Now that sysfs_getattr and sysfs_permission refresh the vfs
> inode there is no need to immediatly push the mode change
> into the vfs cache.  Reducing the amount of work needed and
> simplifying the locking.
> 
> Acked-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>

Nice.

Acked-by: Serge Hallyn <serue@...ibm.com>

> ---
>  fs/sysfs/file.c |   31 ++++++++-----------------------
>  1 files changed, 8 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index faa1a80..dc30d9e 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -579,38 +579,23 @@ EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
>   */
>  int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
>  {
> -	struct sysfs_dirent *victim_sd = NULL;
> -	struct dentry *victim = NULL;
> -	struct inode * inode;
> +	struct sysfs_dirent *sd;
>  	struct iattr newattrs;
>  	int rc;
> 
> -	rc = -ENOENT;
> -	victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
> -	if (!victim_sd)
> -		goto out;
> +	mutex_lock(&sysfs_mutex);
> 
> -	mutex_lock(&sysfs_rename_mutex);
> -	victim = sysfs_get_dentry(victim_sd);
> -	mutex_unlock(&sysfs_rename_mutex);
> -	if (IS_ERR(victim)) {
> -		rc = PTR_ERR(victim);
> -		victim = NULL;
> +	rc = -ENOENT;
> +	sd = sysfs_find_dirent(kobj->sd, attr->name);
> +	if (!sd)
>  		goto out;
> -	}
> -
> -	inode = victim->d_inode;
> 
> -	mutex_lock(&inode->i_mutex);
> -
> -	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
> +	newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
>  	newattrs.ia_valid = ATTR_MODE;
> -	rc = sysfs_setattr(victim, &newattrs);
> +	rc = sysfs_sd_setattr(sd, &newattrs);
> 
> -	mutex_unlock(&inode->i_mutex);
>   out:
> -	dput(victim);
> -	sysfs_put(victim_sd);
> +	mutex_unlock(&sysfs_mutex);
>  	return rc;
>  }
>  EXPORT_SYMBOL_GPL(sysfs_chmod_file);
> -- 
> 1.6.5.2.143.g8cc62
> 
> --
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