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

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Date:	Fri, 16 Jul 2010 17:02:27 -0400
From:	Valerie Aurora <vaurora@...hat.com>
To:	Ian Kent <raven@...maw.net>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Miklos Szeredi <miklos@...redi.hu>,
	Jan Blunck <jblunck@...e.de>,
	Christoph Hellwig <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 Tue, Jul 13, 2010 at 12:47:02PM +0800, Ian Kent wrote:
> On Tue, Jun 15, 2010 at 11:39:51AM -0700, Valerie Aurora wrote:
> > +
> > +static int
> > +check_mnt_union(struct path *mntpnt, struct vfsmount *topmost_mnt, int mnt_flags)
> > +{
> > +	struct vfsmount *lower_mnt = mntpnt->mnt;
> > +
> > +	if (!(mnt_flags & MNT_UNION))
> > +		return 0;
> > +
> > +#ifndef CONFIG_UNION_MOUNT
> > +	return -EINVAL;
> > +#endif
> > +	if (!(lower_mnt->mnt_sb->s_flags & MS_RDONLY))
> > +		return -EBUSY;
> > +
> > +	if (!list_empty(&lower_mnt->mnt_mounts))
> > +		return -EBUSY;
> > +
> > +	if (!IS_ROOT(mntpnt->dentry))
> > +		return -EINVAL;
> > +
> > +	if (mnt_flags & MNT_READONLY)
> > +		return -EROFS;
> > +
> > +	if (!(topmost_mnt->mnt_sb->s_flags & MS_WHITEOUT))
> > +		return -EINVAL;
> > +
> 
> Is there a need to check fallthru, umm ... that probably doesn't
> apply for the ROOT(), right?

Actually, that's on my todo list - right now I'm assuming MS_WHITEOUT
implies fallthru support as well.  But it doesn't.

We're a little short on MS_* flags.  I'm thinking of just checking
->whiteout and ->fallthru for non-NULL on the root dir and getting rid
of MS_WHITEOUT entirely.  Thoughts?

-VAL
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