linux-kernel - Re: [PATCH 21/38] union-mount: Support for mounting union mount file systems

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Date:	Fri, 6 Aug 2010 12:33:38 -0400
From:	Valerie Aurora <vaurora@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	raven@...maw.net, viro@...iv.linux.org.uk, jblunck@...e.de,
	hch@...radead.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 21/38] union-mount: Support for mounting union mount file systems

On Thu, Aug 05, 2010 at 12:34:18PM +0200, Miklos Szeredi wrote:
> On Wed, 4 Aug 2010, Valerie Aurora wrote:
> > I went for MS_WHITEOUT and MS_FALLTHRU, and added the checks for the
> > ops being non-null.
> 
> This bit me.  Mount failing with EINVAL is a big PITA.

Thanks, I merged this.

-VAL


> Miklos
> 
> 
> Index: linux-2.6/fs/namespace.c
> ===================================================================
> --- linux-2.6.orig/fs/namespace.c	2010-08-05 11:06:56.000000000 +0200
> +++ linux-2.6/fs/namespace.c	2010-08-05 11:39:19.000000000 +0200
> @@ -1387,6 +1387,7 @@ check_mnt_union(struct path *mntpnt, str
>  		return 0;
>  
>  #ifndef CONFIG_UNION_MOUNT
> +	printk(KERN_INFO "union mount: not supported by the kernel\n");
>  	return -EINVAL;
>  #endif
>  	for (p = lower_mnt; p; p = next_mnt(p, lower_mnt)) {
> @@ -1396,17 +1397,23 @@ check_mnt_union(struct path *mntpnt, str
>  			return -EBUSY;
>  	}
>  
> -	if (!IS_ROOT(mntpnt->dentry))
> +	if (!IS_ROOT(mntpnt->dentry)) {
> +		printk(KERN_INFO "union mount: not root\n");
>  		return -EINVAL;
> +	}
>  
>  	if (mnt_flags & MNT_READONLY)
>  		return -EROFS;
>  
> -	if (!(topmost_mnt->mnt_sb->s_flags & MS_WHITEOUT))
> +	if (!(topmost_mnt->mnt_sb->s_flags & MS_WHITEOUT)) {
> +		printk(KERN_INFO "union mount: whiteout not supported by fs\n");
>  		return -EINVAL;
> +	}
>  
> -	if (!(topmost_mnt->mnt_sb->s_flags & MS_FALLTHRU))
> +	if (!(topmost_mnt->mnt_sb->s_flags & MS_FALLTHRU)) {
> +		printk(KERN_INFO "union mount: fallthrough not supported by fs\n");
>  		return -EINVAL;
> +	}
>  
>  	/* XXX top level mount should only be mounted once */
>  
> --
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