drbd: Preallocate one page per drbd_socket as a receive buffer

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_int.h

@@ -554,6 +554,8 @@ struct p_delay_probe93 {
 #error "PAGE_SIZE too small"
 #endif
 
+#define DRBD_SOCKET_BUFFER_SIZE 4096
+
 union p_polymorph {
         struct p_header           header;
         struct p_handshake       handshake;
@@ -803,7 +805,7 @@ struct drbd_socket {
 	/* this way we get our
 	 * send/receive buffers off the stack */
 	union p_polymorph sbuf;
-	union p_polymorph rbuf;
+	void *rbuf;
 };
 
 struct drbd_md {

drivers/block/drbd/drbd_main.c

@@ -2272,6 +2272,19 @@ struct drbd_tconn *conn_by_name(const char *name)
 	return tconn;
 }
 
+static int drbd_alloc_socket(struct drbd_socket *socket)
+{
+	socket->rbuf = (void *) __get_free_page(GFP_KERNEL);
+	if (!socket->rbuf)
+		return -ENOMEM;
+	return 0;
+}
+
+static void drbd_free_socket(struct drbd_socket *socket)
+{
+	free_page((unsigned long) socket->rbuf);
+}
+
 struct drbd_tconn *drbd_new_tconn(const char *name)
 {
 	struct drbd_tconn *tconn;
@@ -2284,6 +2297,11 @@ struct drbd_tconn *drbd_new_tconn(const char *name)
 	if (!tconn->name)
 		goto fail;
 
+	if (drbd_alloc_socket(&tconn->data))
+		goto fail;
+	if (drbd_alloc_socket(&tconn->meta))
+		goto fail;
+
 	if (!zalloc_cpumask_var(&tconn->cpu_mask, GFP_KERNEL))
 		goto fail;
 
@@ -2322,6 +2340,8 @@ struct drbd_tconn *drbd_new_tconn(const char *name)
 fail:
 	tl_cleanup(tconn);
 	free_cpumask_var(tconn->cpu_mask);
+	drbd_free_socket(&tconn->meta);
+	drbd_free_socket(&tconn->data);
 	kfree(tconn->name);
 	kfree(tconn);
 
@@ -2334,6 +2354,8 @@ void drbd_free_tconn(struct drbd_tconn *tconn)
 	idr_destroy(&tconn->volumes);
 
 	free_cpumask_var(tconn->cpu_mask);
+	drbd_free_socket(&tconn->meta);
+	drbd_free_socket(&tconn->data);
 	kfree(tconn->name);
 	kfree(tconn->int_dig_out);
 	kfree(tconn->int_dig_in);