mm-only debug patch...

Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/attr.c

@@ -186,6 +186,8 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
 			return -EPERM;
 	}
 
+	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
+
 	now = current_fs_time(inode->i_sb);
 
 	attr->ia_ctime = now;