ncpfs: document dentry_unhash usage

ncpfs returns EBUSY if there are any references to the directory.  The
dentry_unhash call only unhashes the dentry if there are no references.

CC: Petr Vandrovec <petr@vandrovec.name>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ncpfs/dir.c

@@ -1033,8 +1033,11 @@ static int ncp_rmdir(struct inode *dir, struct dentry *dentry)
 	DPRINTK("ncp_rmdir: removing %s/%s\n",
 		dentry->d_parent->d_name.name, dentry->d_name.name);
 
+	/*
+	 * fail with EBUSY if there are still references to this
+	 * directory.
+	 */
 	dentry_unhash(dentry);
-
 	error = -EBUSY;
 	if (!d_unhashed(dentry))
 		goto out;