[PATCH] fs: add a sanity check in d_free

Hi Al,

remember that debug session we did at KS? You suggested this patch back
then....

From 7751eaf30474b8cbfaea64795805a17eab05ac53 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@linux.intel.com>
Date: Tue, 16 Sep 2008 16:51:17 -0700
Subject: [PATCH] fs: add a sanity check in d_free

we're seeing some corruption in the dentry->d_alias list that
appears like a free of an entry still on the list; this patch
adds a WARN_ON() to catch this scenario, as suggested by Al Viro

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>