[Ocfs2-devel] mount point is not unique among all nodes

[Joel Becker <Joel.Becker@oracle.com>]

On Thu, Feb 12, 2009 at 02:17:40PM -0800, Joel Becker wrote:
> On Fri, Feb 13, 2009 at 04:09:19AM +0800, Coly Li wrote:
> > Hi list,
> > 
> > Here is a bug report on novell bugzilla (https://bugzilla.novell.com/show_bug.cgi?id=456280) that
> > mount point inside node A can be removed from node B.
> 
> 	Can't access the bug.
> 
> > The problem is, node B does not know an empty dir is be using as mount point on another node. Is
> > there any solution to return -EBUSY when a dir is be using as mount point on another node ?
> 
> 	This is a good question.  As of right now, we don't have a way
> to do it.

	Sunil and I took a look.  It would seem we need to mark the
dentry lock LVB with a mountpoint count.  That way, ocfs2_unlink() could
check that right before calling ocfs2_remote_dentry_delete().
	The problem is that the VFS doesn't notify us when one of our
directories is mounted over.  Somewhere in do_add_mount() it would need
to tell ocfs2 about it, so that ocfs2 could take the EX on the dentry
lock and bump the mount count in the LVB.
	So, that's what we'll do when we get around to it.  I don't
think it's a high priority; we haven't actually run into this until now.

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127