ocfs2: Add missing iput() during error handling in ocfs2_dentry_attach_lock()

In ocfs2_dentry_attach_lock(), if unable to get the dentry lock, we need to
call iput(inode) because a failure here means no d_instantiate(), which means
the normally matching iput() will not be called during dput(dentry).

This patch fixes the oops that accompanies the following message:
(3996,1):dlm_empty_lockres:2708 ERROR: lockres W00000000000000000a1046b06a4382 still has local locks!
kernel BUG in dlm_empty_lockres at /rpmbuild/smushran/BUILD/ocfs2-1.4.2/fs/ocfs2/dlm/dlmmaster.c:2709!
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/dcache.c

@@ -290,6 +290,21 @@ out_attach:
 	else
 		mlog_errno(ret);
 
+	/*
+	 * In case of error, manually free the allocation and do the iput().
+	 * We need to do this because error here means no d_instantiate(),
+	 * which means iput() will not be called during dput(dentry).
+	 */
+	if (ret < 0 && !alias) {
+		ocfs2_lock_res_free(&dl->dl_lockres);
+		BUG_ON(dl->dl_count != 1);
+		spin_lock(&dentry_attach_lock);
+		dentry->d_fsdata = NULL;
+		spin_unlock(&dentry_attach_lock);
+		kfree(dl);
+		iput(inode);
+	}
+
 	dput(alias);
 
 	return ret;