1 files changed, 99 insertions, 0 deletions
diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
new file mode 100644
index 000000000000..2cccb4be289d
--- /dev/null
+++ b/net/rxrpc/conn_client.c
@@ -0,0 +1,99 @@
+/* Client connection-specific management code.
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include <linux/timer.h>
+#include "ar-internal.h"
+
+/*
+ * We use machine-unique IDs for our client connections.
+ */
+DEFINE_IDR(rxrpc_client_conn_ids);
+static DEFINE_SPINLOCK(rxrpc_conn_id_lock);
+
+/*
+ * Get a connection ID and epoch for a client connection from the global pool.
+ * The connection struct pointer is then recorded in the idr radix tree.  The
+ * epoch is changed if this wraps.
+ *
+ * TODO: The IDR tree gets very expensive on memory if the connection IDs are
+ * widely scattered throughout the number space, so we shall need to retire
+ * connections that have, say, an ID more than four times the maximum number of
+ * client conns away from the current allocation point to try and keep the IDs
+ * concentrated.  We will also need to retire connections from an old epoch.
+ */
+int rxrpc_get_client_connection_id(struct rxrpc_connection *conn,
+				   struct rxrpc_transport *trans,
+				   gfp_t gfp)
+{
+	u32 epoch;
+	int id;
+
+	_enter("");
+
+	idr_preload(gfp);
+	write_lock_bh(&trans->conn_lock);
+	spin_lock(&rxrpc_conn_id_lock);
+
+	epoch = rxrpc_epoch;
+
+	/* We could use idr_alloc_cyclic() here, but we really need to know
+	 * when the thing wraps so that we can advance the epoch.
+	 */
+	if (rxrpc_client_conn_ids.cur == 0)
+		rxrpc_client_conn_ids.cur = 1;
+	id = idr_alloc(&rxrpc_client_conn_ids, conn,
+		       rxrpc_client_conn_ids.cur, 0x40000000, GFP_NOWAIT);
+	if (id < 0) {
+		if (id != -ENOSPC)
+			goto error;
+		id = idr_alloc(&rxrpc_client_conn_ids, conn,
+			       1, 0x40000000, GFP_NOWAIT);
+		if (id < 0)
+			goto error;
+		epoch++;
+		rxrpc_epoch = epoch;
+	}
+	rxrpc_client_conn_ids.cur = id + 1;
+
+	spin_unlock(&rxrpc_conn_id_lock);
+	write_unlock_bh(&trans->conn_lock);
+	idr_preload_end();
+
+	conn->proto.epoch = epoch;
+	conn->proto.cid = id << RXRPC_CIDSHIFT;
+	set_bit(RXRPC_CONN_HAS_IDR, &conn->flags);
+	_leave(" [CID %x:%x]", epoch, conn->proto.cid);
+	return 0;
+
+error:
+	spin_unlock(&rxrpc_conn_id_lock);
+	write_unlock_bh(&trans->conn_lock);
+	idr_preload_end();
+	_leave(" = %d", id);
+	return id;
+}
+
+/*
+ * Release a connection ID for a client connection from the global pool.
+ */
+void rxrpc_put_client_connection_id(struct rxrpc_connection *conn)
+{
+	if (test_bit(RXRPC_CONN_HAS_IDR, &conn->flags)) {
+		spin_lock(&rxrpc_conn_id_lock);
+		idr_remove(&rxrpc_client_conn_ids,
+			   conn->proto.cid >> RXRPC_CIDSHIFT);
+		spin_unlock(&rxrpc_conn_id_lock);
+	}
+}