net/mlx5_core: Add flow steering base data structures

Introducing the base data structure and its operations that are
going to represent ConnectX-4 Flow Steering, this data structure
is basically a tree and all Flow steering objects such as
(Flow Table/Flow Group/FTE/etc ..) are represented as fs_node(s).

fs_node is the base object which describes a basic tree node, with the
following extra info:
    type: describes the runtime type of the node (Object).
    lock: lock this node sub-tree.
    ref_count: number of children + current references.
    remove_func: a generic destructor.

fs_node types will be used and explained once the usage is added in the
following patches.
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/Makefile

@@ -2,7 +2,7 @@ obj-$(CONFIG_MLX5_CORE)		+= mlx5_core.o
 
 mlx5_core-y :=	main.o cmd.o debugfs.o fw.o eq.o uar.o pagealloc.o \
 		health.o mcg.o cq.o srq.o alloc.o qp.o port.o mr.o pd.o   \
-		mad.o transobj.o vport.o sriov.o fs_cmd.o
+		mad.o transobj.o vport.o sriov.o fs_cmd.o fs_core.o
 mlx5_core-$(CONFIG_MLX5_CORE_EN) += wq.o flow_table.o eswitch.o \
 		en_main.o en_flow_table.o en_ethtool.o en_tx.o en_rx.o \
 		en_txrx.o

drivers/net/ethernet/mellanox/mlx5/core/fs_core.c

+/*
+ * Copyright (c) 2015, Mellanox Technologies. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/mutex.h>
+#include <linux/mlx5/driver.h>
+
+#include "mlx5_core.h"
+#include "fs_core.h"
+
+static void tree_init_node(struct fs_node *node,
+			   unsigned int refcount,
+			   void (*remove_func)(struct fs_node *))
+{
+	atomic_set(&node->refcount, refcount);
+	INIT_LIST_HEAD(&node->list);
+	INIT_LIST_HEAD(&node->children);
+	mutex_init(&node->lock);
+	node->remove_func = remove_func;
+}
+
+static void tree_add_node(struct fs_node *node, struct fs_node *parent)
+{
+	if (parent)
+		atomic_inc(&parent->refcount);
+	node->parent = parent;
+
+	/* Parent is the root */
+	if (!parent)
+		node->root = node;
+	else
+		node->root = parent->root;
+}
+
+static void tree_get_node(struct fs_node *node)
+{
+	atomic_inc(&node->refcount);
+}
+
+static void nested_lock_ref_node(struct fs_node *node)
+{
+	if (node) {
+		mutex_lock_nested(&node->lock, SINGLE_DEPTH_NESTING);
+		atomic_inc(&node->refcount);
+	}
+}
+
+static void lock_ref_node(struct fs_node *node)
+{
+	if (node) {
+		mutex_lock(&node->lock);
+		atomic_inc(&node->refcount);
+	}
+}
+
+static void unlock_ref_node(struct fs_node *node)
+{
+	if (node) {
+		atomic_dec(&node->refcount);
+		mutex_unlock(&node->lock);
+	}
+}
+
+static void tree_put_node(struct fs_node *node)
+{
+	struct fs_node *parent_node = node->parent;
+
+	lock_ref_node(parent_node);
+	if (atomic_dec_and_test(&node->refcount)) {
+		if (parent_node)
+			list_del_init(&node->list);
+		if (node->remove_func)
+			node->remove_func(node);
+		kfree(node);
+		node = NULL;
+	}
+	unlock_ref_node(parent_node);
+	if (!node && parent_node)
+		tree_put_node(parent_node);
+}
+
+static int tree_remove_node(struct fs_node *node)
+{
+	if (atomic_read(&node->refcount) > 1)
+		return -EPERM;
+	tree_put_node(node);
+	return 0;
+}

drivers/net/ethernet/mellanox/mlx5/core/fs_core.h

@@ -56,6 +56,12 @@ struct fs_node {
 	struct list_head	list;
 	struct list_head	children;
 	enum fs_node_type	type;
+	struct fs_node		*parent;
+	struct fs_node		*root;
+	/* lock the node for writing and traversing */
+	struct mutex		lock;
+	atomic_t		refcount;
+	void			(*remove_func)(struct fs_node *);
 };
 
 struct mlx5_flow_rule {