linux-kernel - Re: [PATCH 16/20] sysfs: Propagate renames to the vfs on demand

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Message-ID: <4A1521C2.4000506@kernel.org>
Date:	Thu, 21 May 2009 18:41:22 +0900
From:	Tejun Heo <tj@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 16/20] sysfs: Propagate renames to the vfs on demand

Eric W. Biederman wrote:
> From: Eric W. Biederman <ebiederm@...ssion.com>
> 
> By teaching sysfs_revalidate to hide a dentry for
> a sysfs_dirent if the sysfs_dirent has been renamed,
> and by teaching sysfs_lookup to return the original
> dentry if the sysfs dirent has been renamed.  I can
> show the results of renames correctly without having to
> update the dcache during the directory rename.
> 
> This massively simplifies the rename logic allowing a lot
> of weird sysfs special cases to be removed along with
> a lot of now unnecesary helper code.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>

It's probably a good idea to cc Al Viro?

> @@ -311,6 +270,14 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
>  	if (sd->s_flags & SYSFS_FLAG_REMOVED)
>  		goto out_bad;
>  
> +	/* The sysfs dirent has been moved? */
> +	if (dentry->d_parent->d_fsdata != sd->s_parent)
> +		goto out_bad;
> +
> +	/* The sysfs dirent has been renamed */
> +	if (strcmp(dentry->d_name.name, sd->s_name) != 0)
> +		goto out_bad;
> +
>  	mutex_unlock(&sysfs_mutex);
>  out_valid:
>  	return 1;
> @@ -318,6 +285,12 @@ out_bad:
>  	/* Remove the dentry from the dcache hashes.
>  	 * If this is a deleted dentry we use d_drop instead of d_delete
>  	 * so sysfs doesn't need to cope with negative dentries.
> +	 *
> +	 * If this is a dentry that has simply been renamed we
> +	 * use d_drop to remove it from the dcache lookup on it's
							     ^^^^
							     its

> +	 * old parent.  If this dentry persists later when a lookup
> +	 * is performed at it's new name the dentry will be readded
                           ^^^^
			   its

Other than the above comment changes,

Acked-by: Tejun Heo <tj@...nel.org>

-- 
tejun
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