linux-kernel - Re: [PATCH 3/7 v3] vfs: add flag to allow rename to same inode

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Message-ID: <20100923220437.GD3536@shell>
Date:	Thu, 23 Sep 2010 18:04:37 -0400
From:	Valerie Aurora <vaurora@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	neilb@...e.de, viro@...iv.linux.org.uk
Subject: Re: [PATCH 3/7 v3] vfs: add flag to allow rename to same inode

On Mon, Sep 20, 2010 at 08:04:07PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> The overlay filesystem uses dummy inodes for non-directories.  Allow
> rename to work in this case despite the inode being the same.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> ---
>  fs/namei.c         |    4 +++-
>  include/linux/fs.h |    1 +
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6/include/linux/fs.h
> ===================================================================
> --- linux-2.6.orig/include/linux/fs.h	2010-08-25 14:19:34.000000000 +0200
> +++ linux-2.6/include/linux/fs.h	2010-08-25 14:19:53.000000000 +0200
> @@ -179,6 +179,7 @@ struct inodes_stat_t {
>  #define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move()
>  					 * during rename() internally.
>  					 */
> +#define FS_RENAME_SELF_ALLOW	65536	/* Allow rename to same inode */
>  
>  /*
>   * These are the fs-independent mount-flags: up to 32 flags are supported
> Index: linux-2.6/fs/namei.c
> ===================================================================
> --- linux-2.6.orig/fs/namei.c	2010-08-25 10:19:53.000000000 +0200
> +++ linux-2.6/fs/namei.c	2010-08-25 14:22:56.000000000 +0200
> @@ -2620,8 +2620,10 @@ int vfs_rename(struct inode *old_dir, st
>  	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
>  	const unsigned char *old_name;
>  
> -	if (old_dentry->d_inode == new_dentry->d_inode)
> +	if (old_dentry->d_inode == new_dentry->d_inode &&
> +	    !(old_dir->i_sb->s_type->fs_flags & FS_RENAME_SELF_ALLOW)) {
>   		return 0;
> +	}
>   
>  	error = may_delete(old_dir, old_dentry, is_dir);
>  	if (error)
> 

Perhaps a note in the commit message to say that the (inode == inode)
check on the lower layer is done when overlayfs calls vfs_rename() on
the targets?

What other issues arise with dummy inodes?

-VAL
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