[PATCH] r/o bind mounts: clean up OCFS2 nlink handling

OCFS2 does some operations on i_nlink, then reverts them if some of its
operations fail to complete.  This does not fit in well with the
drop_nlink() logic where we expect i_nlink to stay at zero once it gets
there.

So, delay all of the nlink operations until we're sure that the operations
have completed.  Also, introduce a small helper to check whether an inode
has proper "unlinkable" i_nlink counts no matter whether it is a directory
or regular inode.

This patch is broken out from the others because it does contain some
logical changes.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>