ocfs2: needs ->d_lock to poke in ->d_parent->d_inode from ->d_revalidate()

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/ocfs2/dcache.c

@@ -70,9 +70,10 @@ static int ocfs2_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 	 */
 	if (inode == NULL) {
 		unsigned long gen = (unsigned long) dentry->d_fsdata;
-		unsigned long pgen =
-			OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
-
+		unsigned long pgen;
+		spin_lock(&dentry->d_lock);
+		pgen = OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
+		spin_unlock(&dentry->d_lock);
 		trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
 						       dentry->d_name.name,
 						       pgen, gen);